Fatigue Crack Growth and Crack Bridging in SCS-6/Ti-24-11

NASA Technical Reports Server (NTRS)

Ghosn, Louis J.; Kantzos, Pete; Telesman, Jack

1995-01-01

Interfacial damage induced by relative fiber/matrix sliding was found to occur in the bridged zone of unidirectional SCS-6/Ti-24Al-11Nb intermetallic matrix composite specimens subjected to fatigue crack growth conditions. The degree of interfacial damage was not uniform along the bridged crack wake. Higher damage zones were observed near the machined notch in comparison to the crack tip. The interfacial friction shear strength tau(sub f) measured in the crack wake using pushout testing revealed lower values than the as-received interface. Interfacial wear also reduced the strength of the bridging fibers. The reduction in fiber strength is thought to be a function of the magnitude of relative fiber/matrix displacements ind the degree of interfacial damage. Furthermore, two different fiber bridging models were used to predict the influence of bridging on the fatigue crack driving force. The shear lag model required a variable tau(sub f) in the crack wake (reflecting the degradation of the interface) before its predictions agreed with trends exhibited by the experimental data. The fiber pressure model did an excellent job in predicting both the FCG data and the DeltaCOD in the bridged zone even though it does not require a knowledge of tau(sub f).

Cartilage microindentation using cylindrical and spherical optical fiber indenters with integrated Bragg gratings as force sensors

NASA Astrophysics Data System (ADS)

Marchi, G.; Canti, O.; Baier, V.; Micallef, W.; Hartmann, B.; Alberton, P.; Aszodi, A.; Clausen-Schaumann, H.; Roths, J.

2018-02-01

Fiber optic microindentation sensors that have the potential to be integrated into arthroscopic instruments and to allow localizing degraded articular cartilage are presented in this paper. The indenters consist of optical fibers with integrated Bragg gratings as force sensors. In a basic configuration, the tip of the fiber optic indenter consists of a cleaved fiber end, forming a cylindrical flat punch indenter geometry. When using this indenter geometry, high stresses at the edges of the cylinder are present, which can disrupt the tissue structure. This is avoided with an improved version of the indenter. A spherical indenter tip that is formed by melting the end of the glass fiber. The spherical fiber tip shows the additional advantage of strongly reducing reflections from the fiber end. This allows a reduction of the length of the fiber optic sensor element from 65 mm of the flat punch type to 27 mm of the spherical punch. In order to compare the performance of both indenter types, in vitro stress-relaxation indentation experiments were performed on bovine articular cartilage with both indenter types, to assess biomechanical properties of bovine articular cartilage. For indentation depths between 60 μm and 300 μm, the measurements with both indenter types agreed very well with each other. This shows that both indenter geometries are suitable for microindentation measuremnts . The spherical indenter however has the additional advantage that it minimizes the risk to damage the surface of the tissue and has less than half dimensions than the flat indenter.

Force and time-dependent self-assembly, disruption and recovery of supramolecular peptide amphiphile nanofibers

NASA Astrophysics Data System (ADS)

Begum Dikecoglu, F.; Topal, Ahmet E.; Ozkan, Alper D.; Deniz Tekin, E.; Tekinay, Ayse B.; Guler, Mustafa O.; Dana, Aykutlu

2018-07-01

Biological feedback mechanisms exert precise control over the initiation and termination of molecular self-assembly in response to environmental stimuli, while minimizing the formation and propagation of defects through self-repair processes. Peptide amphiphile (PA) molecules can self-assemble at physiological conditions to form supramolecular nanostructures that structurally and functionally resemble the nanofibrous proteins of the extracellular matrix, and their ability to reconfigure themselves in response to external stimuli is crucial for the design of intelligent biomaterials systems. Here, we investigated real-time self-assembly, deformation, and recovery of PA nanofibers in aqueous solution by using a force-stabilizing double-pass scanning atomic force microscopy imaging method to disrupt the self-assembled peptide nanofibers in a force-dependent manner. We demonstrate that nanofiber damage occurs at tip-sample interaction forces exceeding 1 nN, and the damaged fibers subsequently recover when the tip pressure is reduced. Nanofiber ends occasionally fail to reconnect following breakage and continue to grow as two individual nanofibers. Energy minimization calculations of nanofibers with increasing cross-sectional ellipticity (corresponding to varying levels of tip-induced fiber deformation) support our observations, with high-ellipticity nanofibers exhibiting lower stability compared to their non-deformed counterparts. Consequently, tip-mediated mechanical forces can provide an effective means of altering nanofiber integrity and visualizing the self-recovery of PA assemblies.

Force and time-dependent self-assembly, disruption and recovery of supramolecular peptide amphiphile nanofibers.

PubMed

Dikecoglu, F Begum; Topal, Ahmet E; Ozkan, Alper D; Tekin, E Deniz; Tekinay, Ayse B; Guler, Mustafa O; Dana, Aykutlu

2018-07-13

Biological feedback mechanisms exert precise control over the initiation and termination of molecular self-assembly in response to environmental stimuli, while minimizing the formation and propagation of defects through self-repair processes. Peptide amphiphile (PA) molecules can self-assemble at physiological conditions to form supramolecular nanostructures that structurally and functionally resemble the nanofibrous proteins of the extracellular matrix, and their ability to reconfigure themselves in response to external stimuli is crucial for the design of intelligent biomaterials systems. Here, we investigated real-time self-assembly, deformation, and recovery of PA nanofibers in aqueous solution by using a force-stabilizing double-pass scanning atomic force microscopy imaging method to disrupt the self-assembled peptide nanofibers in a force-dependent manner. We demonstrate that nanofiber damage occurs at tip-sample interaction forces exceeding 1 nN, and the damaged fibers subsequently recover when the tip pressure is reduced. Nanofiber ends occasionally fail to reconnect following breakage and continue to grow as two individual nanofibers. Energy minimization calculations of nanofibers with increasing cross-sectional ellipticity (corresponding to varying levels of tip-induced fiber deformation) support our observations, with high-ellipticity nanofibers exhibiting lower stability compared to their non-deformed counterparts. Consequently, tip-mediated mechanical forces can provide an effective means of altering nanofiber integrity and visualizing the self-recovery of PA assemblies.

Thulium fiber laser lithotripsy using a muzzle brake fiber tip

NASA Astrophysics Data System (ADS)

Hutchens, Thomas C.; Gonzalez, David A.; Irby, Pierce B.; Fried, Nathaniel M.

2017-02-01

The Thulium fiber laser (TFL) is being explored as an alternative to Holmium:YAG laser for lithotripsy. TFL beam profile allows coupling of higher power into smaller fibers than multimode Holmium laser beam, without proximal fiber tip degradation. A smaller fiber provides more space in ureteroscope working channel for increased saline irrigation and allows maximum ureteroscope flexion. However, distal fiber tip burnback increases as fiber diameter decreases. Previous studies utilizing hollow steel sheaths around recessed distal fiber tips reduced fiber burnback, but increased retropulsion. In this study, a "fiber muzzle brake" was tested for reducing fiber burnback and stone retropulsion. TFL lithotripsy studies were performed at 1908 nm, 35 mJ, 500 μs, and 300 Hz using a 100-μm-core fiber. The optimal stainless steel muzzle brake tip tested consisted of a 1-cm-long, 560-μm-OD, 360-μm-ID tube with 275-μm thru hole located 250-μm from the distal end. The fiber tip was recessed a distance of 500 μm. Stone phantom retropulsion, fiber tip burnback, and calcium oxalate stone ablation studies were performed, ex vivo. Small stones with a mass of 40 +/- 4 mg and 4-mm-diameter were ablated over a 1.5-mm sieve in 25 +/- 4 s (n=10), without distal fiber tip burnback. Reduction in stone phantom retropulsion distance by 50% and 85% was observed when using muzzle brake tips versus 100-μm-core bare fibers and hollow steel tip fibers. The muzzle brake fiber tip provided efficient stone ablation, reduced stone retropulsion, and minimal fiber degradation during TFL lithotripsy.

Optical coherence tomography guided dental drill

DOEpatents

DaSilva, Luiz B.; Colston, Jr., Bill W.; James, Dale L.

2002-01-01

A dental drill that has one or multiple single mode fibers that can be used to image in the vicinity of the drill tip. It is valuable to image below the surface being drilled to minimize damage to vital or normal tissue. Identifying the boundary between decayed and normal enamel (or dentine) would reduce the removal of viable tissue, and identifying the nerve before getting too close with the drill could prevent nerve damage. By surrounding a drill with several optical fibers that can be used by an optical coherence domain reflectometry (OCDR) to image several millimeters ahead of the ablation surface will lead to a new and improved dental treatment device.

Lithotripsy Performance of Specially Designed Laser Fiber Tips.

PubMed

Kronenberg, Peter; Traxer, Olivier

2016-05-01

We evaluated and compared a standard laser lithotripsy fiber to laser fibers claimed to have lithotripsy performance enhancing features. A special AccuMax™ 200 polished tip fiber and an AccuTrac™ ball-shaped tip fiber, each with an approximately 240 μm core, were compared to a standard 272 μm core fiber (Rocamed™). The polished and ball-shaped tip fibers were used and reused without preparation. The standard fiber was stripped and cleaved according to manufacturer instructions after each experiment. An automated laser fragmentation testing system was used to perform multiple 30-second laser lithotripsy experiments. To mimic most typical lithotripsy conditions soft and hard stone materials were used with high frequency, low pulse energy (20 Hz and 0.5 J) or with low frequency, high pulse energy (5 Hz and 2.0 J) lithotripter settings. Ablation volumes and laser fiber tip photographs before and after lithotripsy were compared. The standard and ball-shaped tip fibers did not differ in ablation volume (p = 0.72) but they ablated 174% and 188% more stone, respectively, than the polished tip fiber (p <0.0001). The ball-shaped tip showed remarkable fiber tip degradation after short-term use at low frequency, high pulse energy settings. When high pulse energy settings were applied first even for short-term use, the ablation volume achieved by the polished and ball-shaped tip fibers at high frequency, low pulse energy settings decreased more than 20%. The standard laser fiber was as good as and sometimes better than the specially designed fibers. Rapid degradation of the specially designed laser fiber tips strongly limits their general usefulness but ball-shaped tip fibers may be useful in specific situations. Copyright © 2016 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Response of automated tow placed laminates to stress concentrations

NASA Technical Reports Server (NTRS)

Cairns, Douglas S.; Ilcewicz, Larry B.; Walker, Tom

1993-01-01

In this study, the response of laminates with stress concentrations is explored. Automated Tow Placed (ATP, also known as Fiber Placement) laminates are compared to conventional tape layup manufacturing. Previous tensile fracture tests on fiber placed laminates show an improvement in tensile fracture of large notches over 20 percent compared to tape layup laminates. A hierarchial modeling scheme is presented. In this scheme, a global model is developed for laminates with notches. A local model is developed to study the influence of inhomogeneities at the notch tip, which are a consequence of the fiber placement manufacturing technique. In addition, a stacked membrane model was developed to study delaminations and splitting on a ply-by-ply basis. The results indicate that some benefit with respect to tensile fracture (up to 11 percent) can be gained from inhomogeneity alone, but that the most improvement may be obtained with splitting and delaminations which are more severe in the case of fiber placement compared to tape layup. Improvements up to 36 percent were found from the model for fiber placed laminates with damage at the notch tip compared to conventional tape layup.

Fabrication and characterization of cylindrical light diffusers comprised of shape memory polymer.

PubMed

Small, Ward; Buckley, Patrick R; Wilson, Thomas S; Loge, Jeffrey M; Maitland, Kristen D; Maitland, Duncan J

2008-01-01

We developed a technique for constructing light diffusing devices comprised of a flexible shape memory polymer (SMP) cylindrical diffuser attached to the tip of an optical fiber. The devices are fabricated by casting an SMP rod over the cleaved tip of an optical fiber and media blasting the SMP rod to create a light diffusing surface. The axial and polar emission profiles and circumferential (azimuthal) uniformity are characterized for various blasting pressures, nozzle-to-sample distances, and nozzle translation speeds. The diffusers are generally strongly forward-directed and consistently withstand over 8 W of incident IR laser light without suffering damage when immersed in water. These devices are suitable for various endoluminal and interstitial biomedical applications.

Fabrication and characterization of cylindrical light diffusers comprised of shape memory polymer

PubMed Central

Small, Ward; Buckley, Patrick R.; Wilson, Thomas S.; Loge, Jeffrey M.; Maitland, Kristen D.; Maitland, Duncan J.

2009-01-01

We developed a technique for constructing light diffusing devices comprised of a flexible shape memory polymer (SMP) cylindrical diffuser attached to the tip of an optical fiber. The devices are fabricated by casting an SMP rod over the cleaved tip of an optical fiber and media blasting the SMP rod to create a light diffusing surface. The axial and polar emission profiles and circumferential (azimuthal) uniformity are characterized for various blasting pressures, nozzle-to-sample distances, and nozzle translation speeds. The diffusers are generally strongly forward-directed and consistently withstand over 8 W of incident IR laser light without suffering damage when immersed in water. These devices are suitable for various endoluminal and interstitial biomedical applications. PMID:18465981

Photonic surgery with noncoherent light

NASA Astrophysics Data System (ADS)

Feuermann, Daniel; Gordon, Jeffrey M.; Ng, Tuck Wah

2006-03-01

Extensive photothermal surgical effects have been generated with artificial noncoherent light. Our ex vivo experiments produced the same type and extent of tissue damage ordinarily achieved with laser fiber-optic surgery, at comparable surgical efficacy, the motivation being the possibility of supplanting surgical lasers with a potentially far less expensive device. Maximum-flux optics reconstitute the immense power density at the core of an ultrabright discharge lamp inside an optical fiber the distal tip of which couples light into the organ.

BRANCHED FIBERS FROM OLD FAST-TWITCH DYSTROPHIC MUSCLES ARE THE SITES OF TERMINAL DAMAGE IN MUSCULAR DYSTROPHY.

PubMed

Kiriaev, Leonit; Kueh, Sindy; Morley, John W; North, Kathryn N; Houweling, Peter J; Head, Stewart I

2018-02-07

A striking pathological feature of dystrophinopathies is the presence of morphologically abnormal branched skeletal muscle fibers. The deterioration of muscle contractile function in Duchenne muscular dystrophy is accompanied by both an increase in number and complexity of these branched fibers. We propose that when number and complexity of branched fibers reaches a critical threshold, "tipping point" the branches in and of themselves are the site of contraction-induced rupture. In the present study, we use the dystrophic mdx mouse and littermate controls to study the pre-diseased dystrophic fast-twitch EDL muscle at 2-3-weeks, the peak myonecrotic phase at 6-9 weeks and finally "old" at 58-112 weeks. Using a combination of isolated muscle function contractile measurements coupled with single fiber imaging and confocal microscope imaging of cleared whole muscles we identified a distinct pathophysiology; acute fiber rupture at branch nodes, which occurs in "old" fast-twitch EDL muscle approaching the end stage of the dystrophinopathy muscle disease, where the EDL muscles are entirely composed of complexed branched fibers. This evidence supports our concept of "tipping point" where the number and extent of fiber branching reaches a level where the branching itself terminally compromises muscle function, irrespective of the absence of dystrophin.

Fiber optic muzzle brake tip for reducing fiber burnback and stone retropulsion during thulium fiber laser lithotripsy

NASA Astrophysics Data System (ADS)

Hutchens, Thomas C.; Gonzalez, David A.; Irby, Pierce B.; Fried, Nathaniel M.

2017-01-01

The experimental thulium fiber laser (TFL) is being explored as an alternative to the current clinical gold standard Holmium:YAG laser for lithotripsy. The near single-mode TFL beam allows coupling of higher power into smaller optical fibers than the multimode Holmium laser beam profile, without proximal fiber tip degradation. A smaller fiber is desirable because it provides more space in the ureteroscope working channel for increased saline irrigation rates and allows maximum ureteroscope deflection. However, distal fiber tip burnback increases as fiber diameter decreases. Previous studies utilizing hollow steel sheaths around recessed distal fiber tips reduced fiber burnback but increased stone retropulsion. A "fiber muzzle brake" was tested for reducing both fiber burnback and stone retropulsion by manipulating vapor bubble expansion. TFL lithotripsy studies were performed at 1908 nm, 35 mJ, 500 μs, and 300 Hz using a 100-μm-core fiber. The optimal stainless steel muzzle brake tip tested consisted of a 1-cm-long, 560-μm-outer-diameter, 360-μm-inner-diameter tube with a 275-μm-diameter through hole located 250 μm from the distal end. The fiber tip was recessed a distance of 500 μm. Stone phantom retropulsion, fiber tip burnback, and calcium oxalate stone ablation studies were performed ex vivo. Small stones with a mass of 40±4 mg and 4-mm-diameter were ablated over a 1.5-mm sieve in 25±4 s (n=10) without visible distal fiber tip burnback. Reduction in stone phantom retropulsion distance by 50% and 85% was observed when using muzzle brake tips versus 100-μm-core bare fibers and hollow steel tip fibers, respectively. The muzzle brake fiber tip simultaneously provided efficient stone ablation, reduced stone retropulsion, and minimal fiber degradation during TFL lithotripsy.

Thulium fiber laser-induced vapor bubble dynamics using bare, tapered, ball, hollow steel, and muzzle brake fiber optic tips

NASA Astrophysics Data System (ADS)

Gonzalez, David A.; Hardy, Luke A.; Hutchens, Thomas C.; Irby, Pierce B.; Fried, Nathaniel M.

2018-03-01

This study characterizes laser-induced vapor bubble dynamics for five different distal fiber optic tip configurations, to provide insight into stone retropulsion commonly experienced during laser ablation of kidney stones. A thulium fiber laser with 1908-nm wavelength delivered 34-mJ energy per pulse at 500-μs pulse duration through five different fibers such as 100-μm-core / 170-μm-OD bare fiber tip, 150- to 300-μm-core tapered fiber tip, 100-μm-core / 300-μm-OD ball tip fiber, 100-μm-core / 340-μm-OD hollow steel tip fiber, and 100-μm-core / 560-μm-OD muzzle brake fiber tip. A high-speed camera with 10-μm-spatial and 9.5-μs-temporal resolution was used to image the vapor bubble dynamics. A needle hydrophone measured pressure transients in the forward (0 deg) and side (90 deg) directions while placed at a 6.8 ± 0.4 mm distance from the distal fiber tip. Maximum bubble dimensions (width/length) averaged 0.7/1.5, 1.0/1.6, 0.5/1.1, 0.8/1.9, and 0.7 / 1.5 mm, for bare, tapered, ball, hollow steel, and muzzle brake fiber tips, respectively (n = 5). The hollow steel tip exhibited the most elongated vapor bubble shape, translating into increased forward pressure in this study and consistent with higher stone retropulsion in previous reports. Relative pressures (a.u.) in (forward/side) directions averaged 1.7/1.6, 2.0/2.0, 1.4/1.2, 6.8/1.1, and 0.3/1.2, for each fiber tip (n = 5). For the hollow steel tip, forward pressure was 4 × higher than for the bare fiber. For the muzzle brake fiber tip, forward pressure was 5 × lower than the bare fiber. Bubble dimensions and pressure measurements demonstrated that the muzzle brake fiber tip reduced forward pressure by partially venting vapors through the portholes, which is consistent with the observation of lower stone retropulsion in previous reports.

Thulium fiber laser induced vapor bubbles using bare, tapered, ball, hollow steel, and muzzle brake fiber optic tips

NASA Astrophysics Data System (ADS)

Gonzalez, David A.; Hardy, Luke A.; Hutchens, Thomas C.; Irby, Pierce B.; Fried, Nathaniel M.

2018-02-01

This study characterizes laser-induced vapor bubbles for five distal fiber optic tip configurations, to provide insight into stone retropulsion experienced during laser ablation of kidney stones. A TFL with 1908-nm wavelength delivered 34 mJ energy per pulse at 500-μs pulse duration through five different fibers: 100-μm-core/170-μm-OD bare fiber tip, 150-μm- to 300-μm-core tapered fiber tip, 100-μm-core/300-μm-OD ball tip fiber, 100-μm-core/340- μm-OD hollow steel tip fiber, and 100-μm-core/560-μm-OD muzzle brake fiber tip. A high speed camera with 10- μm spatial and 9.5-μs temporal resolution imaged vapor bubble dynamics. A needle hydrophone measured pressure transients in forward (0°) and side (90°) directions while placed at a 6.8 +/- 0.4 mm distance from fiber tip. Maximum bubble dimensions (width/length) averaged 0.7/1.5, 1.0/1.6, 0.5/1.1, 0.8/1.9, and 0.7/1.5 mm, for bare, tapered, ball, hollow steel, and muzzle tips, respectively (n=5). The hollow steel tip exhibited the most elongated vapor bubble shape, translating into increased forward pressure in this study and consistent with higher stone retropulsion in previous reports. Relative pressures (a.u.) in (forward/side) directions averaged 1.7/1.6, 2.0/2.0, 1.4/1.2, 6.8/1.1, and 0.3/1.2, for each fiber tip (n=5). For hollow steel tip, forward pressure was 4× higher than for bare fiber. For the muzzle brake fiber tip, forward pressure was 5× lower than for bare fiber. Bubble dimensions and pressure measurements demonstrated that the muzzle tip reduced forward pressure by partially venting vapors through side holes, consistent with lower stone retropulsion observed in previous reports.

Photothermal lesions in soft tissue induced by optical fiber microheaters.

PubMed

Pimentel-Domínguez, Reinher; Moreno-Álvarez, Paola; Hautefeuille, Mathieu; Chavarría, Anahí; Hernández-Cordero, Juan

2016-04-01

Photothermal therapy has shown to be a promising technique for local treatment of tumors. However, the main challenge for this technique is the availability of localized heat sources to minimize thermal damage in the surrounding healthy tissue. In this work, we demonstrate the use of optical fiber microheaters for inducing thermal lesions in soft tissue. The proposed devices incorporate carbon nanotubes or gold nanolayers on the tips of optical fibers for enhanced photothermal effects and heating of ex vivo biological tissues. We report preliminary results of small size photothermal lesions induced on mice liver tissues. The morphology of the resulting lesions shows that optical fiber microheaters may render useful for delivering highly localized heat for photothermal therapy.

Demonstration of an ultra-wideband optical fiber inline polarizer with metal nano-grid on the fiber tip.

PubMed

Lin, Yongbin; Guo, Junpeng; Lindquist, Robert G

2009-09-28

Dramatic increase in the bandwidth of optical fiber inline polarizer can be achieved by using metal nano-grid on the fiber tip. However, high extinction ratio of such fiber polarizer requires high spatial frequency metal nano girds with high aspect ratio on the small area of optical fiber tip. We report the development of a nano-fabrication process on the optical fiber tip, and the design and realization of the first ultra-wideband fiber inline polarization device with Au nano gird fabricated on a single mode optical fiber end face.

Nasal tip plasty: the delivery approach revisited.

PubMed

Xavier, Rui

2013-02-01

The delivery approach, though very appropriate for remodeling the tip of the nose, has been overlooked in recent years and has often been passed over for the open approach. One reason for this is the intercartilaginous incision used for the delivery approach, which may cause scarring at the nasal valve area, leading to postoperative functional obstruction of the nose. The delivery of the alar cartilages is another negative, as this maneuver will disrupt the collagen fibers that attach the upper lateral cartilages to the cephalic margin of the alar cartilages, leading to a weakening of the tip's support. We propose a modification to the traditional delivery approach by using a transcartilaginous instead of an intercartilaginous incision to prevent damage to the valve area. We also suggest taking advantage of the interference to the tip's support caused by the disruption of the collagen fibers of the scroll area. The purpose of this article is to describe this modification of the delivery approach and to emphasize the advantages that this controlled interference to the tip's support may have in selected cases. This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Graded-index fiber tip optical tweezers: numerical simulation and trapping experiment.

PubMed

Gong, Yuan; Ye, Ai-Yan; Wu, Yu; Rao, Yun-Jiang; Yao, Yao; Xiao, Song

2013-07-01

Optical fiber tweezers based on a graded-index multimode fiber (GIMMF) tip is proposed. Light propagation characteristics and gradient force distribution near the GIMMF tip are numerically investigated, which are further compared with that of optical fiber tips based on conventional single mode fibers. The simulated results indicated that by selecting optimal GIMMF length, the gradient force of the GIMMF tip tweezers is about 4 times higher than that of the SMF tip tweezers with a same shape. To prove the feasibility of such a new concept, optical trapping of yeast cells with a diameter of ~5 μm using the chemically-etched GIMMF tip is experimentally demonstrated and the trapping force is also calculated.

A novel carbon tipped single micro-optrode for combined optogenetics and electrophysiology

PubMed Central

Vizvári, Attila D.; Bali, Zsolt K.; Márki, Balázs; Nagy, Lili V.; Kónya, Zoltán; Madarász, Dániel; Henn-Mike, Nóra; Varga, Csaba; Hernádi, István

2018-01-01

Optical microelectrodes (optrodes) are used in neuroscience to transmit light into the brain of a genetically modified animal to evoke and record electrical activity from light-sensitive neurons. Our novel micro-optrode solution integrates a light-transmitting 125 micrometer optical fiber and a 9 micrometer carbon monofilament to form an electrical lead element, which is contained in a borosilicate glass sheathing coaxial arrangement ending with a micrometer-sized carbon tip. This novel unit design is stiff and slender enough to be used for targeting deep brain areas, and may cause less tissue damage compared with previous models. The center-positioned carbon fiber is less prone to light-induced artifacts than side-lit metal microelectrodes previously presented. The carbon tip is capable of not only recording electrical signals of neuronal origin but can also provide valuable surface area for electron transfer, which is essential in electrochemical (voltammetry, amperometry) or microbiosensor applications. We present details of design and manufacture as well as operational examples of the newly developed single micro-optrode, which includes assessments of 1) carbon tip length–impedance relationship, 2) light transmission capabilities, 3) photoelectric artifacts in carbon fibers, 4) responses to dopamine using fast-scan cyclic voltammetry in vivo, and 5) optogenetic stimulation and spike or local field potential recording from the rat brain transfected with channelrhodopsin-2. With this work, we demonstrate that our novel carbon tipped single micro-optrode may open up new avenues for use in optogenetic stimulation when needing to be combined with extracellular recording, electrochemical, or microbiosensor measurements performed on a millisecond basis. PMID:29513711

Fiber optic muzzle brake tip for reducing fiber burnback and stone retropulsion during thulium fiber laser lithotripsy.

PubMed

Hutchens, Thomas C; Gonzalez, David A; Irby, Pierce B; Fried, Nathaniel M

2017-01-01

The experimental thulium fiber laser (TFL) is being explored as an alternative to the current clinical gold standard Holmium:YAG laser for lithotripsy. The near single-mode TFL beam allows coupling of higher power into smaller optical fibers than the multimode Holmium laser beam profile, without proximal fiber tip degradation. A smaller fiber is desirable because it provides more space in the ureteroscope working channel for increased saline irrigation rates and allows maximum ureteroscope deflection. However, distal fiber tip burnback increases as fiber diameter decreases. Previous studies utilizing hollow steel sheaths around recessed distal fiber tips reduced fiber burnback but increased stone retropulsion. A “fiber muzzle brake” was tested for reducing both fiber burnback and stone retropulsion by manipulating vapor bubble expansion. TFL lithotripsy studies were performed at 1908 nm, 35 mJ, 500 ?? ? s , and 300 Hz using a 100 - ? m -core fiber. The optimal stainless steel muzzle brake tip tested consisted of a 1-cm-long, 560 - ? m -outer-diameter, 360 - ? m -inner-diameter tube with a 275 - ? m -diameter through hole located 250 ?? ? m from the distal end. The fiber tip was recessed a distance of 500 ?? ? m . Stone phantom retropulsion, fiber tip burnback, and calcium oxalate stone ablation studies were performed ex vivo. Small stones with a mass of 40 ± 4 ?? mg and 4-mm-diameter were ablated over a 1.5-mm sieve in 25 ± 4 ?? s

Multi-function diamond film fiber optic probe and measuring system employing same

DOEpatents

Young, J.P.

1998-11-24

A fused fiber optic probe having a protective cover, a fiber optic probe system, and embodiments thereof for conducting electromagnetic spectral measurements are disclosed. The fused fiber optic probe comprises a probe tip having a specific geometrical configuration, an exciting optical fiber and at least one collection optical fiber fused within a housing, preferably silica, with a protective cover disposed over at least a portion of the probe tip. The specific geometrical configurations in which the probe tip can be shaped include a slanted probe tip with an angle greater than 0{degree}, an inverted cone-shaped probe tip, and a lens head. 9 figs.

Photoacoustic shock wave emission and cavitation from structured optical fiber tips

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

Mohammadzadeh, M.; Gonzalez-Avila, S. R.; Ohl, C. D., E-mail: cdohl@ntu.edu.sg

Photoacoustic waves generated at the tip of an optical fiber consist of a compressive shock wave followed by tensile diffraction waves. These tensile waves overlap along the fiber axis and form a cloud of cavitation bubbles. We demonstrate that shaping the fiber tip through micromachining alters the number and direction of the emitted waves and cavitation clouds. Shock wave emission and cavitation patterns from five distinctively shaped fiber tips have been studied experimentally and compared to a linear wave propagation model. In particular, multiple shock wave emission and generation of strong tension away from the fiber axis have been realizedmore » using modified fiber tips. These altered waveforms may be applied for novel microsurgery protocols, such as fiber-based histotripsy, by utilizing bubble-shock wave interaction.« less

Use of nondestructive inspection and fiber optic sensing for damage characterization in carbon fiber fuselage structure

NASA Astrophysics Data System (ADS)

Neidigk, Stephen; Le, Jacqui; Roach, Dennis; Duvall, Randy; Rice, Tom

2014-04-01

To investigate a variety of nondestructive inspection technologies and assess impact damage characteristics in carbon fiber aircraft structure, the FAA Airworthiness Assurance Center, operated by Sandia National Labs, fabricated and impact tested two full-scale composite fuselage sections. The panels are representative of structure seen on advanced composite transport category aircraft and measured approximately 56"x76". The structural components consisted of a 16 ply skin, co-cured hat-section stringers, fastened shear ties and frames. The material used to fabricate the panels was T800 unidirectional pre-preg (BMS 8-276) and was processed in an autoclave. Simulated hail impact testing was conducted on the panels using a high velocity gas gun with 2.4" diameter ice balls in collaboration with the University of California San Diego (UCSD). Damage was mapped onto the surface of the panels using conventional, hand deployed ultrasonic inspection techniques, as well as more advanced ultrasonic and resonance scanning techniques. In addition to the simulated hail impact testing performed on the panels, 2" diameter steel tip impacts were used to produce representative impact damage which can occur during ground maintenance operations. The extent of impact damage ranges from less than 1 in2 to 55 in2 of interply delamination in the 16 ply skin. Substructure damage on the panels includes shear tie cracking and stringer flange disbonding. It was demonstrated that the fiber optic distributed strain sensing system is capable of detecting impact damage when bonded to the backside of the fuselage.

Are we all doing it wrong? Influence of stripping and cleaving methods of laser fibers on laser lithotripsy performance.

PubMed

Kronenberg, Peter; Traxer, Olivier

2015-03-01

We assessed whether stripping and cleaving the laser fiber tip with specialized tools, namely laser fiber strippers, or ceramic or metal scissors, would influence lithotripsy performance. Laser fiber tips were stripped with a specialized laser fiber stripper or remained coated. The tips were then cleaved with metal or ceramic scissors. Laser lithotripsy experiments were performed with the 4 fiber tip combinations using an automated laser fragmentation testing system with artificial stones made of plaster of Paris or BegoStone Plus (Bego, Lincoln, Rhode Island). High frequency-low pulse energy (20 Hz and 0.5 J) and low frequency-high pulse energy (5 Hz and 2.0 J) settings were used for 30 seconds. Fissure width, depth and volume, and laser fiber tip photos were analyzed. Coated laser fiber tips always achieved significantly higher ablation volumes (sometimes greater than 50%) than stripped laser fiber tips (p <0.00001) regardless of cleaving scissor type, stone material or lithotripter setting. Coated fiber tips cleaved with metal scissors ablated as well as those cleaved with ceramic scissors (p = 0.16). However, stripped fibers were much less ablative when they were cut with metal scissors compared to ceramic scissors (p <0.00001). Harder stone material decreased ablation volume (p <0.00001). Low frequency-high pulse energy settings were an average of 3 times more ablative than high frequency-low pulse energy settings (p <0.00001). Stripping the fibers, a harder stone material and low frequency-high pulse energy settings were associated with increased fiber tip degradation. Coated laser fibers provided better lithotripsy performance and metal scissors were as good as ceramic scissors to cleave coated fibers. This knowledge may improve and simplify the way that laser lithotripsy procedures are done worldwide. Copyright © 2015 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Tapered fiber nanoprobes: plasmonic nanopillars on tapered optical fiber tips for large EM enhancement.

PubMed

Savaliya, Priten; Dhawan, Anuj

2016-10-01

Employing finite difference time domain simulations, we demonstrate that electromagnetic field enhancement is substantially greater for tapered optical fibers with plasmonic nanostructures present on their tips as compared with non-tapered optical fibers having those plasmonic nanostructures, or with tapered optical fibers without the plasmonic nanostructures. We also carried out fabrication of plasmonic nanostructures on optical fiber tips.

Cotton fiber tips have diverse morphologies and show evidence of apical cell wall synthesis

PubMed Central

Stiff , Michael R.; Haigler, Candace H.

2016-01-01

Cotton fibers arise through highly anisotropic expansion of a single seed epidermal cell. We obtained evidence that apical cell wall synthesis occurs through examining the tips of young elongating Gossypium hirsutum (Gh) and G. barbadense (Gb) fibers. We characterized two tip types in Gh fiber (hemisphere and tapered), each with distinct apical diameter, central vacuole location, and distribution of cell wall components. The apex of Gh hemisphere tips was enriched in homogalacturonan epitopes, including a relatively high methyl-esterified form associated with cell wall pliability. Other wall components increased behind the apex including cellulose and the α-Fuc-(1,2)-β-Gal epitope predominantly found in xyloglucan. Gb fibers had only one narrow tip type featuring characters found in each Gh tip type. Pulse-labeling of cell wall glucans indicated wall synthesis at the apex of both Gh tip types and in distal zones. Living Gh hemisphere and Gb tips ruptured preferentially at the apex upon treatment with wall degrading enzymes, consistent with newly synthesized wall at the apex. Gh tapered tips ruptured either at the apex or distantly. Overall, the results reveal diverse cotton fiber tip morphologies and support primary wall synthesis occurring at the apex and discrete distal regions of the tip. PMID:27301434

Characterization of novel microsphere chain fiber optic tips for potential use in ophthalmic laser surgery.

PubMed

Hutchens, Thomas C; Darafsheh, Arash; Fardad, Amir; Antoszyk, Andrew N; Ying, Howard S; Astratov, Vasily N; Fried, Nathaniel M

2012-06-01

Ophthalmic surgery may benefit from use of more precise fiber delivery systems during laser surgery. Some current ophthalmic surgical techniques rely on tedious mechanical dissection of tissue layers. In this study, chains of sapphire microspheres integrated into a hollow waveguide distal tip are used for erbium:YAG laser ablation studies in contact mode with ophthalmic tissues, ex vivo. The laser's short optical penetration depth combined with the small spot diameters achieved with this fiber probe may provide more precise tissue removal. One-, three-, and five-microsphere chain structures were characterized, resulting in FWHM diameters of 67, 32, and 30 μm in air, respectively, with beam profiles comparable to simulations. Single Er:YAG pulses of 0.1 mJ and 75-μs duration produced ablation craters with average diameters of 44, 30, and 17 μm and depths of 26, 10, and 8 μm, for one-, three-, and five-sphere structures, respectively. Microsphere chains produced spatial filtering of the multimode Er:YAG laser beam and fiber, providing spot diameters not otherwise available with conventional fiber systems. Because of the extremely shallow treatment depth, compact focused beam, and contact mode operation, this probe may have potential for use in dissecting epiretinal membranes and other ophthalmic tissues without damaging adjacent retinal tissue.

Chemically etched fiber tips for near-field optical microscopy: a process for smoother tips.

PubMed

Lambelet, P; Sayah, A; Pfeffer, M; Philipona, C; Marquis-Weible, F

1998-11-01

An improved method for producing fiber tips for scanning near-field optical microscopy is presented. The improvement consists of chemically etching quartz optical fibers through their acrylate jacket. This new method is compared with the previous one in which bare fibers were etched. With the new process the meniscus formed by the acid along the fiber does not move during etching, leading to a much smoother surface of the tip cone. Subsequent metallization is thus improved, resulting in better coverage of the tip with an aluminum opaque layer. Our results show that leakage can be avoided along the cone, and light transmission through the tip is spatially limited to an optical aperture of a 100-nm dimension.

Compound parabolic concentrator optical fiber tip for FRET-based fluorescent sensors

NASA Astrophysics Data System (ADS)

Ul Hassan, Hafeez; Nielsen, Kristian; Aasmul, Soren; Bang, Ole

2015-09-01

The Compound Parabolic Concentrator (CPC) optical fiber tip shape has been proposed for intensity based fluorescent sensors working on the principle of FRET (Förster Resonance Energy Transfer). A simple numerical Zemax model has been used to optimize the CPC tip geometry for a step-index multimode polymer optical fiber for an excitation and emission wavelength of 550 nm and 650nm, respectively. The model suggests an increase of a factor of 1.6 to 4 in the collected fluorescent power for an ideal CPC tip, as compared to the plane-cut fiber tip for fiber lengths between 5 and 45mm.

Quantification of holmium:YAG optical tip degradation

NASA Astrophysics Data System (ADS)

Mues, Adam C.; Teichman, Joel M. H.; Knudsen, Bodo E.

2009-02-01

The holmium:yttrium aluminum garnet (YAG) laser is the gold standard laser for intracorporeal lithotripsy. Optical fibers are utilized to transmit laser energy to the surface of a stone for fragmentation. During lithotripsy, fiber tip degradation (burn back) can occur. The exact mechanism for tip degradation and related factors are not completely understood, and have not been investigated. This characteristic is important because fiber burn back may affect diminish fragmentation efficiency, increase operative time, and increase cost due to the need for fiber replacement. We hypothesize that fiber tip degradation (burn back) varies amongst different commercially available holmium:YAG laser fibers.

Sensitive Detection of Small Particles in Fluids Using Optical Fiber Tip with Dielectrophoresis

PubMed Central

Tai, Yi-Hsin; Chang, Dao-Ming; Pan, Ming-Yang; Huang, Ding-Wei; Wei, Pei-Kuen

2016-01-01

This work presents using a tapered fiber tip coated with thin metallic film to detect small particles in water with high sensitivity. When an AC voltage applied to the Ti/Al coated fiber tip and indium tin oxide (ITO) substrate, a gradient electric field at the fiber tip induced attractive/repulsive force to suspended small particles due to the frequency-dependent dielectrophoresis (DEP) effect. Such DEP force greatly enhanced the concentration of the small particles near the tip. The increase of the local concentration also increased the scattering of surface plasmon wave near the fiber tip. Combined both DEP effect and scattering optical near-field, we show the detection limit of the concentration for 1.36 μm polystyrene beads can be down to 1 particle/mL. The detection limit of the Escherichia coli (E. coli) bacteria was 20 CFU/mL. The fiber tip sensor takes advantages of ultrasmall volume, label-free and simple detection system. PMID:26927128

Micro-mechanical analysis of damage growth and fracture in discontinuous fiber reinforced metal matrix composites

NASA Technical Reports Server (NTRS)

Goree, James G.; Richardson, David E.

1990-01-01

The near-crack-tip stresses in any planar coupon of arbitrary geometry subjected to mode 1 loading may be equated to those in an infinite center-cracked panel subjected to the appropriate equivalent remote biaxial stresses (ERBS). Since this process can be done for all such mode 1 coupons, attention may be focused on the behavior of the equivalent infinite cracked panel. To calculate the ERBS, the constant term in the series expansion of the crack-tip stress must be retained. It is proposed that the ERBS may be used quantitatively to explain different fracture phenomena such as crack branching.

Escherichia coli Fiber Sensors Using Concentrated Dielectrophoretic Force with Optical Defocusing Method.

PubMed

Tai, Yi-Hsin; Lee, Chia-Wei; Chang, Dao-Ming; Lai, Yu-Sheng; Huang, Ding-Wei; Wei, Pei-Kuen

2018-05-25

A sensitive tapered optical fiber tip combined with dielectrophoretic (DEP) trapping was used for rapid and label-free detection of bacteria in water. The angular spectrum of the optical field at the fiber tip was changed with the surrounding refractive index (RI). By measuring far-field intensity change at the defocus plane, the intensity sensitivity was up to 95 200%/RIU (RI unit), and the detection limit was 5.2 × 10 -6 RIU at 0.5% intensity stability. By applying an AC voltage to a Ti/Al coated fiber tip and an indium-tin-oxide glass, the DEP force effectively trapped the Escherichia coli ( E. coli) near the fiber tip. Those bacteria can be directly measured from optical intensity change due to the increase of surrounding RI. By immobilizing the antibody on the Ti/Al fiber tip, the tests for specific K12 bacteria and nonspecific BL21 bacteria verified the specificity. The antibody-immobilized Ti/Al coated fiber tip with DEP trapping can detect bacteria at a concentration about 100 CFU/mL.

Theoretical investigation for excitation light and fluorescence signal of fiber optical sensor using tapered fiber tip.

PubMed

Yuan, Yinquan; Ding, Liyun

2011-10-24

For fiber optical sensor made of tapered fiber tip, the effects of the geometrical parameters of tapered tip on two important factors have been investigated. One factor is the intensity of the evanescent wave into fluorescent layer through core-medium interface; the other is the intensity of fluorescence signal transmitted from fluorescent layer to measurement end. A dependence relation of the intensity of fluorescence signal transmitted from fluorescent layer to measurement end upon the geometrical parameters of tapered tip has been obtained. Theoretical results show that the intensity of the evanescent wave into fluorescent layer rises with the decrease of the end diameter of tapered tip, and the increase of the tip length; and the transmitted power of fluorescence signal increases linearly with the increase of the tip length due to the contribution of the side area of tapered tip. © 2011 Optical Society of America

Optical fiber tips for biological applications: From light confinement, biosensing to bioparticles manipulation.

PubMed

Paiva, Joana S; Jorge, Pedro A S; Rosa, Carla C; Cunha, João P S

2018-05-01

The tip of an optical fiber has been considered an attractive platform in Biology. The simple cleaved end of an optical fiber can be machined, patterned and/or functionalized, acquiring unique properties enabling the exploitation of novel optical phenomena. Prompted by the constant need to measure and manipulate nanoparticles, the invention of the Scanning Near-field Optical Microscopy (SNOM) triggered the optimization and development of novel fiber tip microfabrication methods. In fact, the fiber tip was soon considered a key element in SNOM by confining light to sufficiently small extensions, challenging the diffraction limit. As result and in consequence of the newly proposed "Lab On Tip" concept, several geometries of fiber tips were applied in three main fields: imaging (in Microscopy/Spectroscopy), biosensors and micromanipulation (Optical Fiber Tweezers, OFTs). These are able to exert forces on microparticles, trap and manipulate them for relevant applications, as biomolecules mechanical study or protein aggregates unfolding. This review presents an overview of the main achievements, most impactful studies and limitations of fiber tip-based configurations within the above three fields, along the past 10 years. OFTs could be in future a valuable tool for studying several cellular phenomena such as neurodegeneration caused by abnormal protein fibrils or manipulating organelles within cells. This could contribute to understand the mechanisms of some diseases or biophenomena, as the axonal growth in neurons. To the best of our knowledge, no other review article has so far provided such a broad view. Despite of the limitations, fiber tips have key roles in Biology/Medicine. Copyright © 2018 Elsevier B.V. All rights reserved.

Evaluation of a new 240-μm single-use holmium:YAG optical fiber for flexible ureteroscopy.

PubMed

Khemees, Tariq A; Shore, David M; Antiporda, Michael; Teichman, Joel M H; Knudsen, Bodo E

2013-04-01

Numerous holmium:yttrium-aluminum-garnet laser fibers are available for flexible ureteroscopy. Performance and durability of fibers can vary widely among different manufacturers and their product lines with differences within a single product line have been reported. We sought to evaluate a newly developed nontapered, single-use 240-μm fiber, Flexiva™ 200 (Boston Scientific, Natick, MA), during clinical use and in a bench-testing model. A total of 100 new fibers were tested after their use in 100 consecutive flexible ureteroscopic lithotripsy procedures by a single surgeon (B.K.). Prospectively recorded clinical parameters were laser pulse energy and frequency settings, total energy delivered and fibers failure. Subsequently, each fiber was bench-tested using an established protocol. Parameters evaluated for were fibers true diameter, flexibility, tip degradation, energy transmission in straight and 180° bend configuration and fibers failure threshold with stress testing. The mean total energy delivered was 2.20 kJ (range 0-18.24 kJ) and most common laser settings used were 0.8 J at 8 Hz, 0.2 J at 50 Hz, and 1.0 J at 10 Hz, respectively. No fiber fractured during clinical procedures. The true fiber diameter was 450 μm. Fiber tips burnt back an average of 1.664 mm, but were highly variable. With laser setting of 400 mJ at 5 Hz, the mean energy transmitted was 451 and 441 mJ in straight and 180° bend configuration, respectively. Thirteen percent of fibers fractured at the bend radius of 0.5 cm with a positive correlation to the total energy transmitted during clinical use identified. Fiber performance was consistent in terms of energy transmission and resistance to fracture when activated in bent configuration. Fiber failure during stress testing showed significant correlation with the total energy delivered during the clinical procedure. The lack of fiber fracture during clinical use may reduce the risk of flexible endoscope damage due to fiber failure.

Tapered optical fiber tip probes based on focused ion beam-milled Fabry-Perot microcavities

NASA Astrophysics Data System (ADS)

André, Ricardo M.; Warren-Smith, Stephen C.; Becker, Martin; Dellith, Jan; Rothhardt, Manfred; Zibaii, M. I.; Latifi, H.; Marques, Manuel B.; Bartelt, Hartmut; Frazão, Orlando

2016-09-01

Focused ion beam technology is combined with dynamic chemical etching to create microcavities in tapered optical fiber tips, resulting in fiber probes for temperature and refractive index sensing. Dynamic chemical etching uses hydrofluoric acid and a syringe pump to etch standard optical fibers into cone structures called tapered fiber tips where the length, shape, and cone angle can be precisely controlled. On these tips, focused ion beam is used to mill several different types of Fabry-Perot microcavities. Two main cavity types are initially compared and then combined to form a third, complex cavity structure. In the first case, a gap is milled on the tapered fiber tip which allows the external medium to penetrate the light guiding region and thus presents sensitivity to external refractive index changes. In the second, two slots that function as mirrors are milled on the tip creating a silica cavity that is only sensitive to temperature changes. Finally, both cavities are combined on a single tapered fiber tip, resulting in a multi-cavity structure capable of discriminating between temperature and refractive index variations. This dual characterization is performed with the aid of a fast Fourier transform method to separate the contributions of each cavity and thus of temperature and refractive index. Ultimately, a tapered optical fiber tip probe with sub-standard dimensions containing a multi-cavity structure is projected, fabricated, characterized and applied as a sensing element for simultaneous temperature and refractive index discrimination.

Femtosecond laser micromachining of compound parabolic concentrator fiber tipped glucose sensors.

PubMed

Hassan, Hafeez Ul; Lacraz, Amédée; Kalli, Kyriacos; Bang, Ole

2017-03-01

We report on highly accurate femtosecond (fs) laser micromachining of a compound parabolic concentrator (CPC) fiber tip on a polymer optical fiber (POF). The accuracy is reflected in an unprecedented correspondence between the numerically predicted and experimentally found improvement in fluorescence pickup efficiency of a Förster resonance energy transfer-based POF glucose sensor. A Zemax model of the CPC-tipped sensor predicts an optimal improvement of a factor of 3.96 compared to the sensor with a plane-cut fiber tip. The fs laser micromachined CPC tip showed an increase of a factor of 3.5, which is only 11.6% from the predicted value. Earlier state-of-the-art fabrication of the CPC-shaped tip by fiber tapering was of so poor quality that the actual improvement was 43% lower than the predicted improvement of the ideal CPC shape.

Femtosecond laser micromachining of compound parabolic concentrator fiber tipped glucose sensors

NASA Astrophysics Data System (ADS)

Hassan, Hafeez Ul; Lacraz, Amédée; Kalli, Kyriacos; Bang, Ole

2017-03-01

We report on highly accurate femtosecond (fs) laser micromachining of a compound parabolic concentrator (CPC) fiber tip on a polymer optical fiber (POF). The accuracy is reflected in an unprecedented correspondence between the numerically predicted and experimentally found improvement in fluorescence pickup efficiency of a Förster resonance energy transfer-based POF glucose sensor. A Zemax model of the CPC-tipped sensor predicts an optimal improvement of a factor of 3.96 compared to the sensor with a plane-cut fiber tip. The fs laser micromachined CPC tip showed an increase of a factor of 3.5, which is only 11.6% from the predicted value. Earlier state-of-the-art fabrication of the CPC-shaped tip by fiber tapering was of so poor quality that the actual improvement was 43% lower than the predicted improvement of the ideal CPC shape.

Two-photon excited fluorescence from a pseudoisocyanine-attached gold-coated tip via a thin tapered fiber under a weak continuous wave excitation.

PubMed

Ren, Fang; Takashima, Hideaki; Tanaka, Yoshito; Fujiwara, Hideki; Sasaki, Keiji

2013-11-18

A simple tapered fiber based photonic-plasmonic hybrid nanostructure composed of a thin tapered fiber and a pseudoisocyanine (PIC)-attached Au-coated tip was demonstrated. Using this simple hybrid nanostructure, we succeeded in observing two-photon excited fluorescence from the PIC dye molecules under a weak continuous wave excitation condition. From the results of the tip-fiber distance dependence and excitation polarization dependence, we found that using a thin tapered fiber and an Au-coated tip realized efficient coupling of the incident light (~95%) and LSP excitation at the Au-coated tip, suggesting the possibility of efficiently inducing two-photon excited fluorescence from the PIC dye molecules attached on the Au-coated tip. This simple photonic-plasmonic hybrid system is one of the promising tools for single photon sources, highly efficient plasmonic sensors, and integrated nonlinear plasmonic devices.

Yeh-Stratton Criterion for Stress Concentrations on Fiber-Reinforced Composite Materials

NASA Technical Reports Server (NTRS)

Yeh, Hsien-Yang; Richards, W. Lance

1996-01-01

This study investigated the Yeh-Stratton Failure Criterion with the stress concentrations on fiber-reinforced composites materials under tensile stresses. The Yeh-Stratton Failure Criterion was developed from the initial yielding of materials based on macromechanics. To investigate this criterion, the influence of the materials anisotropic properties and far field loading on the composite materials with central hole and normal crack were studied. Special emphasis was placed on defining the crack tip stress fields and their applications. The study of Yeh-Stratton criterion for damage zone stress fields on fiber-reinforced composites under tensile loading was compared with several fracture criteria; Tsai-Wu Theory, Hoffman Theory, Fischer Theory, and Cowin Theory. Theoretical predictions from these criteria are examined using experimental results.

Accurate real-time sensing tip for aqueous NO with optical fibers embedded in active hydrogel waveguide

NASA Astrophysics Data System (ADS)

Chung, Chieh-Wen; Tsai, May-Jywan; Lin, Peng-Wei; Huang, Ding-Wen; Wang, Kuan-Hsun; Chen, Yu-An; Meng, Hsin-Fei; Zan, Hsiao-Wen; Cheng, Henrich; Tong, Limin; Zhang, Lei; Horng, Sheng-Fu; Hung, Cheng-Hsiung

2018-02-01

A NO sensing tip is made by inserting two parallel optical fibers inside a poly 2-hydroxyethyl methacrylate (PolyHEMA) hydrogel waveguide mixed with the probe molecule 1, 2-Diaminoanthraquinone (DAQ). There is a length difference of 1 mm between the two fibers, and the light has to propagate through the difference from the short fiber to the long fiber. The total cross section area of the active hydrogel waveguide embedded with the fibers is only 3mm x 1.2 mm. For practical use the tip is housed in a needle for mechanical protection and the sensing tip is able to detect aqueous NO concentration around 1 μM with time resolution about 5 minutes. Such a sensing tip can be used to monitor the medical conditions inside the brain after a stroke or a brain injury.

Characterization of novel microsphere chain fiber optic tips for potential use in ophthalmic laser surgery

PubMed Central

Hutchens, Thomas C.; Darafsheh, Arash; Fardad, Amir; Antoszyk, Andrew N.; Ying, Howard S.; Astratov, Vasily N.

2012-01-01

Abstract. Ophthalmic surgery may benefit from use of more precise fiber delivery systems during laser surgery. Some current ophthalmic surgical techniques rely on tedious mechanical dissection of tissue layers. In this study, chains of sapphire microspheres integrated into a hollow waveguide distal tip are used for erbium:YAG laser ablation studies in contact mode with ophthalmic tissues, ex vivo. The laser’s short optical penetration depth combined with the small spot diameters achieved with this fiber probe may provide more precise tissue removal. One-, three-, and five-microsphere chain structures were characterized, resulting in FWHM diameters of 67, 32, and 30 μm in air, respectively, with beam profiles comparable to simulations. Single Er:YAG pulses of 0.1 mJ and 75-μs duration produced ablation craters with average diameters of 44, 30, and 17 μm and depths of 26, 10, and 8 μm, for one-, three-, and five-sphere structures, respectively. Microsphere chains produced spatial filtering of the multimode Er:YAG laser beam and fiber, providing spot diameters not otherwise available with conventional fiber systems. Because of the extremely shallow treatment depth, compact focused beam, and contact mode operation, this probe may have potential for use in dissecting epiretinal membranes and other ophthalmic tissues without damaging adjacent retinal tissue. PMID:22734790

Single and dual fiber nano-tip optical tweezers: trapping and analysis.

PubMed

Decombe, Jean-Baptiste; Huant, Serge; Fick, Jochen

2013-12-16

An original optical tweezers using one or two chemically etched fiber nano-tips is developed. We demonstrate optical trapping of 1 micrometer polystyrene spheres at optical powers down to 2 mW. Harmonic trap potentials were found in the case of dual fiber tweezers by analyzing the trapped particle position fluctuations. The trap stiffness was deduced using three different models. Consistent values of up to 1 fN/nm were found. The stiffness linearly decreases with decreasing light intensity and increasing fiber tip-to-tip distance.

State of the art of CO laser angioplasty system

NASA Astrophysics Data System (ADS)

Arai, Tsunenori; Mizuno, Kyoichi; Miyamoto, Akira; Sakurada, Masami; Kikuchi, Makoto; Kurita, Akira; Nakamura, Haruo; Takaoka, Hidetsugu; Utsumi, Atsushi; Takeuchi, Kiyoshi

1994-07-01

A unique percutaneous transluminal coronary angioplasty system new IR therapy laser with IR glass fiber delivery under novel angioscope guidance was described. Carbon monoxide (CO) laser emission of 5 mm in wavelength was employed as therapy laser to achieve precise ablation of atheromatous plaque with a flexible As-S IR glass fiber for laser delivery. We developed the first medical CO laser as well as As-S IR glass fiber cable. We also developed 5.5 Fr. thin angioscope catheter with complete directional manipulatability at its tip. The system control unit could manage to prevent failure irradiations and fiber damages. This novel angioplasty system was evaluated by a stenosis model of mongrel dogs. We demonstrated the usefulness of our system to overcome current issues on laser angioplasty using multifiber catheter with over-the-guidewire system.

Fiber-array based optogenetic prosthetic system for stimulation therapy

NASA Astrophysics Data System (ADS)

Gu, Ling; Cote, Chris; Tejeda, Hector; Mohanty, Samarendra

2012-02-01

Recent advent of optogenetics has enabled activation of genetically-targeted neuronal cells using low intensity blue light with high temporal precision. Since blue light is attenuated rapidly due to scattering and absorption in neural tissue, optogenetic treatment of neurological disorders may require stimulation of specific cell types in multiple regions of the brain. Further, restoration of certain neural functions (vision, and auditory etc) requires accurate spatio-temporal stimulation patterns rather than just precise temporal stimulation. In order to activate multiple regions of the central nervous system in 3D, here, we report development of an optogenetic prosthetic comprising of array of fibers coupled to independently-controllable LEDs. This design avoids direct contact of LEDs with the brain tissue and thus does not require electrical and heat isolation, which can non-specifically stimulate and damage the local brain regions. The intensity, frequency, and duty cycle of light pulses from each fiber in the array was controlled independently using an inhouse developed LabView based program interfaced with a microcontroller driving the individual LEDs. While the temporal profile of the light pulses was controlled by varying the current driving the LED, the beam profile emanating from each fiber tip could be sculpted by microfabrication of the fiber tip. The fiber array was used to stimulate neurons, expressing channelrhodopsin-2, in different locations within the brain or retina. Control of neural activity in the mice cortex, using the fiber-array based prosthetic, is evaluated from recordings made with multi-electrode array (MEA). We also report construction of a μLED array based prosthetic for spatio-temporal stimulation of cortex.

Method to improve the blade tip-timing accuracy of fiber bundle sensor under varying tip clearance

NASA Astrophysics Data System (ADS)

Duan, Fajie; Zhang, Jilong; Jiang, Jiajia; Guo, Haotian; Ye, Dechao

2016-01-01

Blade vibration measurement based on the blade tip-timing method has become an industry-standard procedure. Fiber bundle sensors are widely used for tip-timing measurement. However, the variation of clearance between the sensor and the blade will bring a tip-timing error to fiber bundle sensors due to the change in signal amplitude. This article presents methods based on software and hardware to reduce the error caused by the tip clearance change. The software method utilizes both the rising and falling edges of the tip-timing signal to determine the blade arrival time, and a calibration process suitable for asymmetric tip-timing signals is presented. The hardware method uses an automatic gain control circuit to stabilize the signal amplitude. Experiments are conducted and the results prove that both methods can effectively reduce the impact of tip clearance variation on the blade tip-timing and improve the accuracy of measurements.

Vaginal Speculum For Photodynamic Therapy And Method Of Using The Same

DOEpatents

Tadir, Yona; Berns, Michael W.; Monk, Brad J.; Profeta, Glen; Tromberg, Bruce J.

1995-10-17

An improved vaginal speculum for photodynamic therapy of intraepithelial tissue and in particular vaginal, cervical and vulvar neoplasia utilizes a precisely and accurately positionable optic fiber through which a predetermined dose of light in the range of 620 to 700 nanometers is delivered over a controlled area which has been previously treated with photodynamic therapeutic substances. In particular, the neoplastic area has been treated with hematoporphyrin derivatives and other photosensitizers which are selectively taken into the cancerous tissue. Exposure to the appropriate wavelength laser light photoactivates the absorbed hematoporphyrins causing the release of singlet oxygen which internally oxidizes and ultimately causes cell death. The fiber optic tip from which the laser light is transmitted is precisely positioned within the body cavity at a predetermined distance from the intraepithelial neoplasia in order to obtain the appropriate spot size and location to minimize damage to healthy tissue and maximize damage to the selectively impregnated cancerous tissue.

Impact resistance of composite fan blades. [fiber reinforced graphite and boron epoxy blades for STOL operating conditions

NASA Technical Reports Server (NTRS)

Premont, E. J.; Stubenrauch, K. R.

1973-01-01

The resistance of current-design Pratt and Whitney Aircraft low aspect ratio advanced fiber reinforced epoxy matrix composite fan blades to foreign object damage (FOD) at STOL operating conditions was investigated. Five graphite/epoxy and five boron/epoxy wide chord fan blades with nickel plated stainless steel leading edge sheath protection were fabricated and impact tested. The fan blades were individually tested in a vacuum whirlpit under FOD environments. The FOD environments were typical of those encountered in service operations. The impact objects were ice balls, gravel, stralings and gelatin simulated birds. Results of the damage sustained from each FOD impact are presented for both the graphite boron reinforced blades. Tests showed that the present design composite fan blades, with wrap around leading edge protection have inadequate FOD impact resistance at 244 m/sec (800 ft/sec) tip speed, a possible STOL operating condition.

Characterization of power induced heating and damage in fiber optic probes for near-field scanning optical microscopy

NASA Astrophysics Data System (ADS)

Dickenson, Nicholas E.; Erickson, Elizabeth S.; Mooren, Olivia L.; Dunn, Robert C.

2007-05-01

Tip-induced sample heating in near-field scanning optical microscopy (NSOM) is studied for fiber optic probes fabricated using the chemical etching technique. To characterize sample heating from etched NSOM probes, the spectra of a thermochromic polymer sample are measured as a function of probe output power, as was previously reported for pulled NSOM probes. The results reveal that sample heating increases rapidly to ˜55-60°C as output powers reach ˜50nW. At higher output powers, the sample heating remains approximately constant up to the maximum power studied of ˜450nW. The sample heating profiles measured for etched NSOM probes are consistent with those previously measured for NSOM probes fabricated using the pulling method. At high powers, both pulled and etched NSOM probes fail as the aluminum coating is damaged. For probes fabricated in our laboratory we find failure occurring at input powers of 3.4±1.7 and 20.7±6.9mW for pulled and etched probes, respectively. The larger half-cone angle for etched probes (˜15° for etched and ˜6° for pulled probes) enables more light delivery and also apparently leads to a different failure mechanism. For pulled NSOM probes, high resolution images of NSOM probes as power is increased reveal the development of stress fractures in the coating at a taper diameter of ˜6μm. These stress fractures, arising from the differential heating expansion of the dielectric and the metal coating, eventually lead to coating removal and probe failure. For etched tips, the absence of clear stress fractures and the pooled morphology of the damaged aluminum coating following failure suggest that thermal damage may cause coating failure, although other mechanisms cannot be ruled out.

Characterization of power induced heating and damage in fiber optic probes for near-field scanning optical microscopy.

PubMed

Dickenson, Nicholas E; Erickson, Elizabeth S; Mooren, Olivia L; Dunn, Robert C

2007-05-01

Tip-induced sample heating in near-field scanning optical microscopy (NSOM) is studied for fiber optic probes fabricated using the chemical etching technique. To characterize sample heating from etched NSOM probes, the spectra of a thermochromic polymer sample are measured as a function of probe output power, as was previously reported for pulled NSOM probes. The results reveal that sample heating increases rapidly to approximately 55-60 degrees C as output powers reach approximately 50 nW. At higher output powers, the sample heating remains approximately constant up to the maximum power studied of approximately 450 nW. The sample heating profiles measured for etched NSOM probes are consistent with those previously measured for NSOM probes fabricated using the pulling method. At high powers, both pulled and etched NSOM probes fail as the aluminum coating is damaged. For probes fabricated in our laboratory we find failure occurring at input powers of 3.4+/-1.7 and 20.7+/-6.9 mW for pulled and etched probes, respectively. The larger half-cone angle for etched probes ( approximately 15 degrees for etched and approximately 6 degrees for pulled probes) enables more light delivery and also apparently leads to a different failure mechanism. For pulled NSOM probes, high resolution images of NSOM probes as power is increased reveal the development of stress fractures in the coating at a taper diameter of approximately 6 microm. These stress fractures, arising from the differential heating expansion of the dielectric and the metal coating, eventually lead to coating removal and probe failure. For etched tips, the absence of clear stress fractures and the pooled morphology of the damaged aluminum coating following failure suggest that thermal damage may cause coating failure, although other mechanisms cannot be ruled out.

Polymer optical fiber compound parabolic concentrator tip for enhanced coupling efficiency for fluorescence based glucose sensors

PubMed Central

Hassan, Hafeez Ul; Nielsen, Kristian; Aasmul, Soren; Bang, Ole

2015-01-01

We demonstrate that the light excitation and capturing efficiency of fluorescence based fiber-optical sensors can be significantly increased by using a CPC (Compound Parabolic Concentrator) tip instead of the standard plane-cut tip. We use Zemax modelling to find the optimum CPC tip profile and fiber length of a polymer optical fiber diabetes sensor for continuous monitoring of glucose levels. We experimentally verify the improved performance of the CPC tipped sensor and the predicted production tolerances. Due to physical size requirements when the sensor has to be inserted into the body a non-optimal fiber length of 35 mm is chosen. For this length an average improvement in efficiency of a factor of 1.7 is experimentally demonstrated and critically compared to the predicted ideal factor of 3 in terms of parameters that should be improved through production optimization. PMID:26713213

Polymer optical fiber compound parabolic concentrator tip for enhanced coupling efficiency for fluorescence based glucose sensors.

PubMed

Hassan, Hafeez Ul; Nielsen, Kristian; Aasmul, Soren; Bang, Ole

2015-12-01

We demonstrate that the light excitation and capturing efficiency of fluorescence based fiber-optical sensors can be significantly increased by using a CPC (Compound Parabolic Concentrator) tip instead of the standard plane-cut tip. We use Zemax modelling to find the optimum CPC tip profile and fiber length of a polymer optical fiber diabetes sensor for continuous monitoring of glucose levels. We experimentally verify the improved performance of the CPC tipped sensor and the predicted production tolerances. Due to physical size requirements when the sensor has to be inserted into the body a non-optimal fiber length of 35 mm is chosen. For this length an average improvement in efficiency of a factor of 1.7 is experimentally demonstrated and critically compared to the predicted ideal factor of 3 in terms of parameters that should be improved through production optimization.

Functional and Physical Outcomes following Use of a Flexible CO2 Laser Fiber and Bipolar Electrocautery in Close Proximity to the Rat Sciatic Nerve with Correlation to an In Vitro Thermal Profile Model

PubMed Central

Robinson, A. M.; Fishman, A. J.; Bendok, B. R.; Richter, C.-P.

2015-01-01

This study compared functional and physical collateral damage to a nerve when operating a Codman MALIS Bipolar Electrosurgical System CMC-III or a CO2 laser coupled to a laser, with correlation to an in vitro model of heating profiles created by the devices in thermochromic ink agarose. Functional damage of the rat sciatic nerve after operating the MALIS or CO2 laser at various power settings and proximities to the nerve was measured by electrically evoked nerve action potentials, and histology of the nerve was used to assess physical damage. Thermochromic ink dissolved in agarose was used to model the spatial and temporal profile of the collateral heating zone of the electrosurgical system and the laser ablation cone. We found that this laser can be operated at 2 W directly above the nerve with minimal damage, while power settings of 5 W and 10 W resulted in acute functional and physical nerve damage, correlating with the maximal heating cone in the thermochromic ink model. MALIS settings up to 40 (11 W) did not result in major functional or physical nerve damage until the nerve was between the forceps tips, correlating with the hottest zone, localized discretely between the tips. PMID:25699266

Gold Coating of Fiber Tips in Near-Field Scanning Optical Microscopy

NASA Technical Reports Server (NTRS)

Vikram, Chandra S.; Witherow, William K.

2000-01-01

We report what is believed to be the first experimental demonstration of gold coating by a chemical baking process on tapered fiber tips used in near-field scanning optical microscopy. Many tips can be simultaneously coated.

Dynamic response of tapered optical multimode fiber coated with carbon nanotubes for ethanol sensing application.

PubMed

Shabaneh, Arafat; Girei, Saad; Arasu, Punitha; Mahdi, Mohd; Rashid, Suraya; Paiman, Suriati; Yaacob, Mohd

2015-05-04

Ethanol is a highly combustible chemical universally designed for biomedical applications. In this paper, optical sensing performance of tapered multimode fiber tip coated with carbon nanotube (CNT) thin film towards aqueous ethanol with different concentrations is investigated. The tapered optical multimode fiber tip is coated with CNT using drop-casting technique and is annealed at 70 °C to enhance the binding of the nanomaterial to the silica fiber tip. The optical fiber tip and the CNT sensing layer are micro-characterized using FESEM and Raman spectroscopy techniques. When the developed sensor was exposed to different concentrations of ethanol (5% to 80%), the sensor reflectance reduced proportionally. The developed sensors showed high sensitivity, repeatability and fast responses (<55 s) towards ethanol.

Dynamic Response of Tapered Optical Multimode Fiber Coated with Carbon Nanotubes for Ethanol Sensing Application

PubMed Central

Shabaneh, Arafat; Girei, Saad; Arasu, Punitha; Mahdi, Mohd; Rashid, Suraya; Paiman, Suriati; Yaacob, Mohd

2015-01-01

Ethanol is a highly combustible chemical universally designed for biomedical applications. In this paper, optical sensing performance of tapered multimode fiber tip coated with carbon nanotube (CNT) thin film towards aqueous ethanol with different concentrations is investigated. The tapered optical multimode fiber tip is coated with CNT using drop-casting technique and is annealed at 70 °C to enhance the binding of the nanomaterial to the silica fiber tip. The optical fiber tip and the CNT sensing layer are micro-characterized using FESEM and Raman spectroscopy techniques. When the developed sensor was exposed to different concentrations of ethanol (5% to 80%), the sensor reflectance reduced proportionally. The developed sensors showed high sensitivity, repeatability and fast responses (<55 s) towards ethanol. PMID:25946634

Photonic jet subwavelength etching using a shaped optical fiber tip.

PubMed

Zelgowski, Julien; Abdurrochman, Andri; Mermet, Frederic; Pfeiffer, Pierre; Fontaine, Joël; Lecler, Sylvain

2016-05-01

We demonstrate that photonic jets (PJs) can be obtained in the vicinity of a shaped optical fiber and that they can be used to achieve subwavelength etchings. Only 10% of the power of a 30 W, 100 ns, near-infrared (1064 nm) Nd:YAG laser, commonly used for industrial laser processing, has been required. Etchings on a silicon wafer with a lateral feature size close to half-laser wavelength have been achieved using a shaped-tip optical fiber. This breakthrough has been carried out in ambient air by using a multimode 100/140 μm silica fiber with a shaped tip that generates a concentrated beam at their vicinity, a phenomenon referred to as a PJ, obtained for the first time without using microspheres. PJ achieved with a fiber tip, easier to manipulate, opens far-reaching benefits for all PJ applications. The roles of parameters such as laser fluence, tip shape, and mode excitation are discussed. A good correlation has been observed between the computed PJ intensity distribution and the etched marks' sizes.

Scale factor gage for fiber optics inspection device

NASA Technical Reports Server (NTRS)

Mcmahon, W.; Sugg, F. E.

1971-01-01

Flexible wire device, fastened along outside of fiber bundle from viewing portion to tip, positions calibrated adjustable gage in field of view. Scale factor is determined from known magnification characteristics of fiber optics system or from graduations on gage tip.

Interlaminar fracture of random short-fiber SMC composite

NASA Technical Reports Server (NTRS)

Wang, S. S.; Suemasu, H.; Zahlan, N. M.

1984-01-01

In the experimental phase of the present study of the interlaminar fracture behavior of a randomly oriented short fiber sheet molding compound (SMC) composite, the double cantilever beam fracture test is used to evaluate the mode I interlaminar fracture toughness of different composite thicknesses. In the analytical phase of this work, a geometrically nonlinear analysis is introduced in order to account for large deflections and nonlinear load deflection curves in the evaluation of interlaminar fracture toughness. For the SMC-R50 material studied, interlaminar toughness is an order of magnitude higher than that of unreinforced neat resin, due to unusual damage mechanisms ahead of the crack tip, together with significant fiber bridging across crack surfaces. Composite thickness effects on interlaminar fracture are noted to be appreciable, and a detailed discussion is given on the influence of SMC microstructure.

Rugged fiber optic probe for raman measurement

DOEpatents

O'Rourke, Patrick E.; Toole, Jr., William R.; Nave, Stanley E.

1998-01-01

An optical probe for conducting light scattering analysis is disclosed. The probe comprises a hollow housing and a probe tip. A fiber assembly made up of a transmitting fiber and a receiving bundle is inserted in the tip. A filter assembly is inserted in the housing and connected to the fiber assembly. A signal line from the light source and to the spectrometer also is connected to the filter assembly and communicates with the fiber assembly. By using a spring-loaded assembly to hold the fiber connectors together with the in-line filters, complex and sensitive alignment procedures are avoided. The close proximity of the filter assembly to the probe tip eliminates or minimizes self-scattering generated by the optical fiber. Also, because the probe can contact the sample directly, sensitive optics can be eliminated.

A non-resonant fiber scanner based on an electrothermally-actuated MEMS stage

PubMed Central

Zhang, Xiaoyang; Duan, Can; Liu, Lin; Li, Xingde; Xie, Huikai

2015-01-01

Scanning fiber tips provides the most convenient way for forward-viewing fiber-optic microendoscopy. In this paper, a distal fiber scanning method based on a large-displacement MEMS actuator is presented. A single-mode fiber is glued on the micro-platform of an electrothermal MEMS stage to realize large range non-resonantscanning. The micro-platform has a large piston scan range of up to 800 µm at only 6V. The tip deflection of the fiber can be further amplified by placing the MEMS stage at a proper location along the fiber. A quasi-static model of the fiber-MEMS assembly has been developed and validated experimentally. The frequency response has also been studied and measured. A fiber tip deflection of up to 1650 µm for the 45 mm-long movable fiber portion has been achieved when the MEMS electrothermal stage was placed 25 mm away from the free end. The electrothermally-actuated MEMS stage shows a great potential for forward viewing fiber scanning and optical applications. PMID:26347583

Photonic jet etching: Justifying the shape of optical fiber tip

NASA Astrophysics Data System (ADS)

Abdurrochman, Andri; Zelgowski, Julien; Lecler, Sylvain; Mermet, Frédéric; Tumbelaka, Bernard; Fontaine, Joël

2016-02-01

Photonic jet (PJ) is a low diverging and highly concentrated beam in the shadow side of dielectric particle (cylinder or sphere). The concentration can be more than 200 times higher than the incidence wave. It is a non-resonance phenomenon in the near-field can propagate in a few wavelengths. Many potential applications have been proposed, including PJ etching. Hence, a guided-beam is considered increasing the PJ mobility control. While the others used a combination of classical optical fibers and spheres, we are concerned on a classical optical fiber with spherical tip to generate the PJ. This PJ driven waveguide has been realized using Gaussian mode beam inside the core. It has different variable parameters compared to classical PJ, which will be discussed in correlation with the etching demonstrations. The parameters dependency between the tip and PJ properties are complex; and theoretical aspect of this interaction will be exposed to justify the shape of our tip and optical fiber used in our demonstrations. Methods to achieve such a needed optical fiber tip will also be described. Finally the ability to generate PJ out of the shaped optical fiber will be experimentally demonstrated and the potential applications for material processing will be exposed.

Observation of Biological Tissues Using Common Path Optical Coherence Tomography with Gold Coated Conical Tip Lens Fiber

NASA Astrophysics Data System (ADS)

Taguchi, K.; Sugiyama, J.; Totsuka, M.; Imanaka, S.

2012-03-01

In this paper, we proposed a high lateral resolution common-path Fourier domain optical coherence tomography(OCT) system with the use of a chemically etched single mode fiber. In our experiments, single mode optical fiber for 1310nm was used for preparing the tapered tips. Our system used a conical microlens that was chemically etched by selective chemical etching technique using an etching solution of buffered hydrofluoric acid (BHF). From experimental results, we verified that our proposed optical coherence tomography system could operate as a common-path Fourier domain OCT system and conical tip lens fiber was very useful for a high lateral resolution common-path Fourier domain OCT system. Furthermore, we could observe a surface of paramecium bursaria and symbiotic chlorella in the paramecium bursaria using gold coated conical-tip fiber in the water.

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

PubMed Central

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

2010-01-01

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

Integrated fiber optic light probe: Measurement of static deflections in rotating turbomachinery

NASA Astrophysics Data System (ADS)

Dhadwal, Harbans S.; Mehmud, Ali; Khan, Romel; Kurkov, Anatole

1996-02-01

This paper describes the design, fabrication, and testing of an integrated fiber optic light probe system for monitoring blade tip deflections, vibrational modes, and changes in blade tip clearances in the compressor stage of rotating turbomachinery. The system comprises a set of integrated fiber optic light probes which are positioned to detect the passing blade tip at the leading and the trailing edges. In this configuration measurements of both blade vibrations and steady-state blade deflection can be obtained from the timing information provided by each light probe, which comprises an integrated fiber optic transmitting channel and a number of high numerical aperture receiving fibers, all mounted in the same cylindrical housing. A spatial resolution of 50 μm is possible with the integrated fiber optic technology, while keeping the outer diameter below 2.5 mm. Additionally, one fiber sensor provides a capability of monitoring changes in the blade tip clearance of the order of 10 μm. Measurements from a single stage compressor facility and an engine-fan rig in a 9 ft×15 ft subsonic wind tunnel are presented.

Numerical analysis of the blade tip-timing signal of a fiber bundle sensor probe

NASA Astrophysics Data System (ADS)

Guo, Haotian; Duan, Fajie; Cheng, Zhonghai

2015-03-01

Blade tip-timing is the most effective method for online blade vibration measurement of large rotating machines like turbine engines. Fiber bundle sensors are utilized in tip-timing system to measure the arrival time of the blade. The model of the tip-timing signal of the fiber bundle sensor is established. Experiments are conducted and the results are in concordance with the model established. The rising speed of the tip-timing signal is analyzed. To minimize the tip-timing error, the effects of the clearance change between the sensor and the blade and the deflection of the tip surface are analyzed. Simulation results indicate that the variable gain amplifier, which amplifies the signals to a similar level, can eliminate the measurement error caused by the variation of the clearance between the sensor and blade. Increasing the clearance between the sensor and blade can reduce the measurement error introduced by deflection of the tip surface.

The fiber walk: a model of tip-driven growth with lateral expansion.

PubMed

Bucksch, Alexander; Turk, Greg; Weitz, Joshua S

2014-01-01

Tip-driven growth processes underlie the development of many plants. To date, tip-driven growth processes have been modeled as an elongating path or series of segments, without taking into account lateral expansion during elongation. Instead, models of growth often introduce an explicit thickness by expanding the area around the completed elongated path. Modeling expansion in this way can lead to contradictions in the physical plausibility of the resulting surface and to uncertainty about how the object reached certain regions of space. Here, we introduce fiber walks as a self-avoiding random walk model for tip-driven growth processes that includes lateral expansion. In 2D, the fiber walk takes place on a square lattice and the space occupied by the fiber is modeled as a lateral contraction of the lattice. This contraction influences the possible subsequent steps of the fiber walk. The boundary of the area consumed by the contraction is derived as the dual of the lattice faces adjacent to the fiber. We show that fiber walks generate fibers that have well-defined curvatures, and thus enable the identification of the process underlying the occupancy of physical space. Hence, fiber walks provide a base from which to model both the extension and expansion of physical biological objects with finite thickness.

The Fiber Walk: A Model of Tip-Driven Growth with Lateral Expansion

PubMed Central

Bucksch, Alexander; Turk, Greg; Weitz, Joshua S.

2014-01-01

Tip-driven growth processes underlie the development of many plants. To date, tip-driven growth processes have been modeled as an elongating path or series of segments, without taking into account lateral expansion during elongation. Instead, models of growth often introduce an explicit thickness by expanding the area around the completed elongated path. Modeling expansion in this way can lead to contradictions in the physical plausibility of the resulting surface and to uncertainty about how the object reached certain regions of space. Here, we introduce fiber walks as a self-avoiding random walk model for tip-driven growth processes that includes lateral expansion. In 2D, the fiber walk takes place on a square lattice and the space occupied by the fiber is modeled as a lateral contraction of the lattice. This contraction influences the possible subsequent steps of the fiber walk. The boundary of the area consumed by the contraction is derived as the dual of the lattice faces adjacent to the fiber. We show that fiber walks generate fibers that have well-defined curvatures, and thus enable the identification of the process underlying the occupancy of physical space. Hence, fiber walks provide a base from which to model both the extension and expansion of physical biological objects with finite thickness. PMID:24465607

Particle trapping in 3-D using a single fiber probe with an annular light distribution.

PubMed

Taylor, R; Hnatovsky, C

2003-10-20

A single optical fiber probe has been used to trap a solid 2 ìm diameter glass bead in 3-D in water. Optical confinement in 2-D was produced by the annular light distribution emerging from a selectively chemically etched, tapered, hollow tipped metalized fiber probe. Confinement of the bead in 3-D was achieved by balancing an electrostatic force of attraction towards the tip and the optical scattering force pushing the particle away from the tip.

Large Volume, Behaviorally-relevant Illumination for Optogenetics in Non-human Primates.

PubMed

Acker, Leah C; Pino, Erica N; Boyden, Edward S; Desimone, Robert

2017-10-03

This protocol describes a large-volume illuminator, which was developed for optogenetic manipulations in the non-human primate brain. The illuminator is a modified plastic optical fiber with etched tip, such that the light emitting surface area is > 100x that of a conventional fiber. In addition to describing the construction of the large-volume illuminator, this protocol details the quality-control calibration used to ensure even light distribution. Further, this protocol describes techniques for inserting and removing the large volume illuminator. Both superficial and deep structures may be illuminated. This large volume illuminator does not need to be physically coupled to an electrode, and because the illuminator is made of plastic, not glass, it will simply bend in circumstances when traditional optical fibers would shatter. Because this illuminator delivers light over behaviorally-relevant tissue volumes (≈ 10 mm 3 ) with no greater penetration damage than a conventional optical fiber, it facilitates behavioral studies using optogenetics in non-human primates.

Infrared thermal measurements of laser soft tissue ablation as a function of air/water coolant for Nd:YAG and diode lasers

NASA Astrophysics Data System (ADS)

Gekelman, Diana; Yamamoto, Andrew; Oto, Marvin G.; White, Joel M.

2003-06-01

The purpose of this investigation was to measure the maximum temperature at the Nd:YAG and Diode lasers fiberoptic tips as a function of air/water coolant, during soft tissue ablation in pig jaws. A pulsed Nd:YAG laser (1064nm) and a Diode laser (800-830 nm) were used varying parameters of power, conditioning or not of the fiber tip, under 4 settings of air/water coolant. The maximum temperature at the fiber tip was measured using an infra-red camera and the interaction of the fiber with the porcine soft tissue was evaluated. A two-factor ANOVA was used for statistical analysis (p<=0.05). Nd:YAG laser interaction with soft tissues produced temperatures levels directly proportional to power increase, but the conditioning of the fiber tip did not influence the temperature rise. On the other hand, conditioning of the fiber tip did influence the temperature rise for Diode laser. The addition of air/water coolant, for both lasers, did not promote temperature rise consistent with cutting and coagulation of porcine soft tissue. Laser parameters affect the fiberoptic surface temperature, and the addition of air/water coolant significantly lowered surface temperature on the fiberoptic tip for all lasers and parameters tested.

Method for Cleaning Laser-Drilled Holes on Printed Wiring Boards by Plasma Treatment

NASA Astrophysics Data System (ADS)

Hirogaki, Toshiki; Aoyama, Eiichi; Minagi, Ryu; Ogawa, Keiji; Katayama, Tsutao; Matsuoka, Takashi; Inoue, Hisahiro

We propose a new method for cleaning blind via holes after laser drilling of PWBs using oxygen plasma treatment. This report dealt with three kinds of PWB materials: epoxy resin and two kinds of aramid fiber reinforced plastics (AFRP: Technora or Kevlar fiber reinforcement). We observed the drilled holes after plasma treatment using both an optical and a scanning electric microscope (SEM). It was confirmed that adequate etching took place in the drilled holes by plasma treatment. We also compared the hole wall and hole bottom after plasma treatment with ones after chemical etching. It was clear that there was no damage to the aramid fiber tip on the hole wall, and that a smooth roughness of the hole wall was obtained by means of plasma treatment. As a result, we demonstrated that the plasma treatment is effective in cleaning the laser drilled holes of PWBs.

Turbine-blade tip clearance and tip timing measurements using an optical fiber bundle sensor

NASA Astrophysics Data System (ADS)

Garcia, Iker; Beloki, Josu; Zubia, Joseba; Durana, Gaizka; Aldabaldetreku, Gotzon

2013-04-01

Traditional limitations of capacitive, inductive or discharging probe sensor for tip timing and tip clearance measurements are overcome by reflective intensity modulated optical fiber sensors. This paper presents the signals and results corresponding to a one stage turbine rig which rotor has 146 blades, obtained from a transonic wind-tunnel test. The probe is based on a trifurcated bundle of optical fibers that is mounted on turbine casing. It is composed of a central illuminating fiber that guides the light from a laser to the turbine blade, and two concentric rings of receiving fibers that collect the reflected light. Two photodetectors turn this reflected light signal from the receiving rings into voltage. The electrical signals are acquired and saved by a high-sample-rate oscilloscope. In tip clearance calculations the ratio of the signals provided by each ring of receiving fibers is evaluated and translated into distance. In the case of tip timing measurements, only one of the signals is considered to get the arrival time of the blade. The differences between the real and theoretical arrival times of the blades are used to obtain the deflections amplitude. The system provides the travelling wave spectrum, which presents the average vibration amplitude of the blades at a certain nodal diameter. The reliability of the results in the turbine rig testing facilities suggests the possibility of performing these measurements in real turbines under real working conditions.

Chemical Silver Coating of Fiber Tips in Near-Field Scanning Optical Microscopy

NASA Technical Reports Server (NTRS)

Vikram, Chandra S.; Witherow, William K.

1998-01-01

We report what is believed to be the first experimental demonstration of silver coating by a wet chemical process on tapered fiber tips used in near-field scanning optical microscopy. The process is at room temperature and pressure and takes only a few minutes to complete. Many tips can be simultaneously coated.

Investigations on the potential of a low power diode pumped Er:YAG laser system for oral surgery

NASA Astrophysics Data System (ADS)

Stock, Karl; Wurm, Holger; Hausladen, Florian; Wagner, Sophia; Hibst, Raimund

2015-02-01

Flash lamp pumped Er:YAG-lasers are used in clinical practice for dental applications successfully. As an alternative, several diode pumped Er:YAG laser systems (Pantec Engineering AG) become available, with mean laser power of 2W, 15W, and 30W. The aim of the presented study is to investigate the potential of the 2W Er:YAG laser system for oral surgery. At first an appropriate experimental set-up was realized with a beam delivery and both, a focusing unit for non-contact tissue cutting and a fiber tip for tissue cutting in contact mode. In order to produce reproducible cuts, the samples (porcine gingiva) were moved by a computer controlled translation stage. On the fresh samples cutting depth and quality were determined by light microscopy. Afterwards histological sections were prepared and microscopically analyzed regarding cutting depth and thermal damage zone. The experiments show that low laser power ≤ 2W is sufficient to perform efficient oral soft tissue cutting with cut depth up to 2mm (sample movement 2mm/s). The width of the thermal damage zone can be controlled by the irradiation parameters within a range of about 50μm to 110μm. In general, thermal injury is more pronounced using fiber tips in contact mode compared to the focused laser beam. In conclusion the results reveal that even the low power diode pumped Er:YAG laser is an appropriate tool for oral surgery.

Fiber optic probe having fibers with endfaces formed for improved coupling efficiency and method using same

DOEpatents

O`Rourke, P.E.; Livingston, R.R.

1995-03-28

A fiber optic probe is disclosed for detecting scattered light, with transmitting and receiving fibers having slanted ends and bundled together to form a bevel within the tip of the probe. The probe comprises a housing with a transparent window across its tip for protecting the transmitting and receiving fibers held therein. The endfaces of the fibers are slanted, by cutting, polishing and the like, so that they lie in a plane that is not perpendicular to the longitudinal axis of the respective fiber. The fibers are held in the tip of the probe using an epoxy and oriented so that lines normal to the slanted endfaces are divergent with respect to one another. The epoxy, which is positioned substantially between the transmitting and receiving fibers, is tapered so that the transmitting fiber, the epoxy and the receiving fiber form a bevel of not more than 20 degrees. The angled fiber endfaces cause directing of the light cones toward each other, resulting in improved light coupling efficiency. A light absorber, such as carbon black, is contained in the epoxy to reduce crosstalk between the transmitting and receiving fibers. 3 figures.

Fiber optic probe having fibers with endfaces formed for improved coupling efficiency and method using same

DOEpatents

O'Rourke, Patrick E.; Livingston, Ronald R.

1995-01-01

A fiber optic probe for detecting scattered light, with transmitting and receiving fibers having slanted ends and bundled together to form a bevel within the tip of the probe. The probe comprises a housing with a transparent window across its tip for protecting the transmitting and receiving fibers held therein. The endfaces of the fibers are slanted, by cutting, polishing and the like, so that they lie in a plane that is not perpendicular to the longitudinal axis of the respective fiber. The fibers are held in the tip of the probe using an epoxy and oriented so that lines normal to the slanted endfaces are divergent with respect to one another. The epoxy, which is positioned substantially between the transmitting and receiving fibers, is tapered so that the transmitting fiber, the epoxy and the receiving fiber form a bevel of not more than 20 degrees. The angled fiber endfaces cause directing of the light cones toward each other, resulting in improved light coupling efficiency. A light absorber, such as carbon black, is contained in the epoxy to reduce crosstalk between the transmitting and receiving fibers.

Fiberoptic probe and system for spectral measurements

DOEpatents

Dai, Sheng; Young, Jack P.

1998-01-01

A fused fiberoptic probe, a system, method and embodiments thereof for conducting spectral measurements are disclosed. The fused fiberoptic probe comprises a probe tip having a specific geometrical configuration, an exciting optical fiber and at least one collection optical fiber fused within a housing, preferrably silica. The specific geometrical configurations in which the probe tip can be shaped include a slanted probe tip with an angle greater than 0.degree., an inverted cone-shaped probe tip, and a lens head.

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.

Micromachined array tip for multifocus fiber-based optical coherence tomography.

PubMed

Yang, Victor X D; Munce, Nigel; Pekar, Julius; Gordon, Maggie L; Lo, Stewart; Marcon, Norman E; Wilson, Brian C; Vitkin, I Alex

2004-08-01

High-resolution optical coherence tomography demands a large detector bandwidth and a high numerical aperture for real-time imaging, which is difficult to achieve over a large imaging depth. To resolve these conflicting requirements we propose a novel multifocus fiber-based optical coherence tomography system with a micromachined array tip. We demonstrate the fabrication of a prototype four-channel tip that maintains a 9-14-microm spot diameter with more than 500 microm of imaging depth. Images of a resolution target and a human tooth were obtained with this tip by use of a four-channel cascaded Michelson fiber-optic interferometer, scanned simultaneously at 8 kHz with geometric power distribution across the four channels.

Dispersion of near-infrared laser energy through radicular dentine when using plain or conical tips.

PubMed

Teo, Christine Yi Jia; George, Roy; Walsh, Laurence J

2018-02-01

The aim of this study was to investigate the influence of tip design on patterns of laser energy dispersion through the dentine of tooth roots when using near-infrared diode lasers. Diode laser emissions of 810 or 940 nm were used in combination with optical fiber tips with either conventional plain ends or conical ends, to irradiate tooth roots of oval or round cross-sectional shapes. The lasers were operated in continuous wave mode at 0.5 W for 5 s with the distal end of the fiber tip placed in the apical or coronal third of the root canal at preset positions. Laser light exiting through the roots and apical foramen was imaged, and the extent of lateral spread calculated. There was a significant difference in infrared light exiting the root canal apex between plain and conical fiber tips for both laser wavelengths, with more forward transmission of laser energy through the apex for plain tips. For both laser wavelengths, there were no significant differences in emission patterns when the variable of canal shape was used and all other variables were kept the same (plain vs conical tip, tip position). To ensure optimal treatment effect and to prevent the risks of inadvertent laser effects on the adjacent periapical tissues, it is important to have a good understanding of laser transmission characteristics of the root canal and root dentine. Importantly, it is also essential to understand transmission characteristics of plain and conical fibers tips.

Articulated Bone Block for Posterior Cruciate Ligament Reconstruction Using Bone-Patellar Tendon-Bone Autograft: Surgical Technique to Facilitate Graft Passage.

PubMed

Cugat, Ramón; Alentorn-Geli, Eduard; Cuscó, Xavier; Navarro, Jordi; Steinbacher, Gilbert; Álvarez-Díaz, Pedro; Seijas, Roberto; Barastegui, David; García-Balletbó, Montse

2018-02-01

Posterior cruciate ligament reconstruction using the transtibial technique provides successful clinical outcomes. However, a bone-patellar tendon-bone (BTB) autograft with the transtibial technique has not been used by some surgeons because of concerns with graft passage from the tibial to the femoral tunnels (sharp turn) that can damage graft fibers. In the present surgical technique, an arthroscopic, transtibial, single-bundle technique for posterior cruciate ligament reconstruction using the BTB autograft with an easy and effective technical tip to facilitate graft passage is presented. Once the BTB is harvested, the femoral bone block is divided into 2 equal-sized blocks providing an articulated structure while preserving the tendon component. This facilitates the passage of the BTB tendon once it is entered in the posterior tibia and the graft has to make a sharp turn to reach the femoral tunnel. This easy and effective technique tip may avoid graft damage during the sharp turn, while maintaining all the advantages of a BTB autograft (bone-to-bone healing, own tissue with fast incorporation, and strong fixation and stability).

Detachable microsphere scalpel tips for potential use in ophthalmic surgery with the erbium:YAG laser.

PubMed

Hutchens, Thomas C; Darafsheh, Arash; Fardad, Amir; Antoszyk, Andrew N; Ying, Howard S; Astratov, Vasily N; Fried, Nathaniel M

2014-01-01

Vitreoretinal surgery is performed using mechanical dissection that sometimes results in iatrogenic complications, including vitreous hemorrhage, retinal breaks, incomplete membrane delamination, retinal distortion, microscopic damage, etc. An ultraprecise laser probe would be an ideal tool for cutting away pathologic membranes; however, the depth of surgery should be precisely controlled to protect the sensitive underlying retina. The ultraprecise surgical microprobe formed by chains of dielectric spheres for use with the erbium:YAG laser source (λ=2940  nm), with extremely short optical penetration depth in tissue, was optimized. Numerical modeling demonstrated a potential advantage of five-sphere focusing chains of sapphire spheres with index n=1.71 for ablating the tissue with self-limited depth around 10 to 20 μm. Novel detachable microsphere scalpel tips formed by chains of 300 μm sapphire (or ruby) spheres were tested on ophthalmic tissues, ex vivo. Detachable scalpel tips could allow for reusability of expensive mid-infrared trunk fibers between procedures, and offer more surgical customization by interchanging various scalpel tip configurations. An innovative method for aiming beam integration into the microsphere scalpel to improve the illumination of the surgical site was also shown. Single Er:YAG pulses of 0.2 mJ and 75-μs duration produced ablation craters in cornea epithelium for one, three, and five sphere structures with the latter generating the smallest crater depth (10 μm) with the least amount of thermal damage depth (30 μm). Detachable microsphere laser scalpel tips may allow surgeons better precision and safety compared to mechanical scalpels when operating on delicate or sensitive areas like the retina.

Sensitive liquid refractive index sensors using tapered optical fiber tips.

PubMed

Tai, Yi-Hsin; Wei, Pei-Kuen

2010-04-01

An optical fiber sensor based on the change of optical confinement in a subwavelength tip is presented. The optical spot is substantially increased when the environmental refractive index (RI) increases from 1.3 to 1.4. By measuring the intensity of low angular spectral components, an intensity sensitivity up to 8000% per RI unit is achieved. The fiber tip sensors take advantage of the small detection volume and real-time responses. We demonstrate the application of the nanofiber sensors for measuring concentrations of acids and evaporation rates of aqueous mixtures.

Cross-sectional examination of the damage zone in impacted specimens of carbon/epoxy and carbon/PEEK composites

NASA Technical Reports Server (NTRS)

Nettles, A. T.; Magold, N. J.

1990-01-01

Drop weight impact testing was utilized to inflict damage on eight-ply bidirectional and unidirectional samples of carbon/epoxy and carbon/PEEK (polyetheretherketone) test specimens with impact energies ranging from 0.80 J to 1.76 J. The impacting tip was of a smaller diameter (4.2-mm) than those used in most previous studies, and the specimens were placed with a diamond wheel wafering saw through the impacted area perpendicular to the outer fibers. Photographs at 12 x magnification were taken of these cross-sections and examined. The results on the bidirectional samples show little damage until 1.13 J, at which point delaminations were seen in the epoxy specimens. The PEEK specimens showed less delamination than the epoxy specimens for a given impact energy level. The unidirectional specimens displayed more damage than the bidirectional samples for a given impact energy, with the PEEK specimens showing much less damage than the epoxy material.

Catalyst-induced growth of carbon nanotubes on tips of cantilevers and nanowires

DOEpatents

Lee, James Weifu; Lowndes, Douglas H.; Merkulov, Vladimir I.; Eres, Gyula; Wei, Yayi; Greenbaum, Elias; Lee, Ida

2004-06-29

A method is described for catalyst-induced growth of carbon nanotubes, nanofibers, and other nanostructures on the tips of nanowires, cantilevers, conductive micro/nanometer structures, wafers and the like. The method can be used for production of carbon nanotube-anchored cantilevers that can significantly improve the performance of scaning probe microscopy (AFM, EFM etc). The invention can also be used in many other processes of micro and/or nanofabrication with carbon nanotubes/fibers. Key elements of this invention include: (1) Proper selection of a metal catalyst and programmable pulsed electrolytic deposition of the desired specific catalyst precisely at the tip of a substrate, (2) Catalyst-induced growth of carbon nanotubes/fibers at the catalyst-deposited tips, (3) Control of carbon nanotube/fiber growth pattern by manipulation of tip shape and growth conditions, and (4) Automation for mass production.

Nanofiber electrode and method of forming same

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

Pintauro, Peter N.; Zhang, Wenjing

In one aspect, a method of forming an electrode for an electrochemical device is disclosed. In one embodiment, the method includes the steps of mixing at least a first amount of a catalyst and a second amount of an ionomer or uncharged polymer to form a solution and delivering the solution into a metallic needle having a needle tip. The method further includes the steps of applying a voltage between the needle tip and a collector substrate positioned at a distance from the needle tip, and extruding the solution from the needle tip at a flow rate such as tomore » generate electrospun fibers and deposit the generated fibers on the collector substrate to form a mat with a porous network of fibers. Each fiber in the porous network of the mat has distributed particles of the catalyst. The method also includes the step of pressing the mat onto a membrane.« less

Intrauterine device for laser light diffusion and method of using the same

DOEpatents

Tadir, Yona; Berns, Michael W.; Svaasand, Lars O.; Tromberg, Bruce J.

1995-01-01

An improved device for delivery of photoenergy from a light source, such as a laser, into a uterine cavity for photodynamic therapy is comprised of a plurality of optic fibers, which are bundled together and inserted into the uterine cavity by means of a uterine cannula. The cannula is positioned within the uterine cavity at a preferred location and then withdrawn thereby allowing the plurality of optic fibers to splay or diverge one from the other within the cavity. Different portions of the distal tip of the optic fiber is provided with a light diffusing tip, the remainder being provided with a nondiffusing tip portion. The fiber optic shape, as well as the segment which is permitted to actively diffuse light through the tip, is selected in order to provide a more uniform exposure intensity of the photo energy or at least sufficient radiation directed to each segment of the uterine walls.

Intrauterine device for laser light diffusion and method of using the same

DOEpatents

Tadir, Y.; Berns, M.W.; Svaasand, L.O.; Tromberg, B.J.

1995-12-26

An improved device for delivery of photoenergy from a light source, such as a laser, into a uterine cavity for photodynamic therapy is comprised of a plurality of optic fibers, which are bundled together and inserted into the uterine cavity by means of a uterine cannula. The cannula is positioned within the uterine cavity at a preferred location and then withdrawn thereby allowing the plurality of optic fibers to splay or diverge one from the other within the cavity. Different portions of the distal tip of the optic fiber is provided with a light diffusing tip, the remainder being provided with a nondiffusing tip portion. The fiber optic shape, as well as the segment which is permitted to actively diffuse light through the tip, is selected in order to provide a more uniform exposure intensity of the photo energy or at least sufficient radiation directed to each segment of the uterine walls. 5 figs.

Optical fiber meta-tips

NASA Astrophysics Data System (ADS)

Principe, Maria; Micco, Alberto; Crescitelli, Alessio; Castaldi, Giuseppe; Consales, Marco; Esposito, Emanuela; La Ferrara, Vera; Galdi, Vincenzo; Cusano, Andrea

2016-04-01

We report on the first example of a "meta-tip" configuration that integrates a metasurface on the tip of an optical fiber. Our proposed design is based on an inverted-Babinet plasmonic metasurface obtained by patterning (via focused ion beam) a thin gold film deposited on the tip of an optical fiber, so as to realize an array of rectangular aperture nanoantennas with spatially modulated sizes. By properly tuning the resonances of the aperture nanoantennas, abrupt variations can be impressed in the field wavefront and polarization. We fabricated and characterized several proof-of-principle prototypes operating an near-infrared wavelengths, and implementing the beam-steering (with various angles) of the cross-polarized component, as well as the excitation of surface waves. Our results pave the way to the integration of the exceptional field-manipulation capabilities enabled by metasurfaces with the versatility and ubiquity of fiber-optics technological platforms.

Fiberoptic probe and system for spectral measurements

DOEpatents

Dai, S.; Young, J.P.

1998-10-13

A fused fiberoptic probe, a system, method and embodiments thereof for conducting spectral measurements are disclosed. The fused fiberoptic probe comprises a probe tip having a specific geometrical configuration, an exciting optical fiber and at least one collection optical fiber fused within a housing, preferably silica. The specific geometrical configurations in which the probe tip can be shaped include a slanted probe tip with an angle greater than 0{degree}, an inverted cone-shaped probe tip, and a lens head. 12 figs.

Optical Fiber-Tip Sensors Based on In-Situ µ-Printed Polymer Suspended-Microbeams.

PubMed

Yao, Mian; Ouyang, Xia; Wu, Jushuai; Zhang, A Ping; Tam, Hwa-Yaw; Wai, P K A

2018-06-05

Miniature optical fiber-tip sensors based on directly µ-printed polymer suspended-microbeams are presented. With an in-house optical 3D μ-printing technology, SU-8 suspended-microbeams are fabricated in situ to form Fabry⁻Pérot (FP) micro-interferometers on the end face of standard single-mode optical fiber. Optical reflection spectra of the fabricated FP micro-interferometers are measured and fast Fourier transform is applied to analyze the cavity of micro-interferometers. The applications of the optical fiber-tip sensors for refractive index (RI) sensing and pressure sensing, which showed 917.3 nm/RIU to RI change and 4.29 nm/MPa to pressure change, respectively, are demonstrated in the experiments. The sensors and their optical µ-printing method unveil a new strategy to integrate complicated microcomponents on optical fibers toward 'lab-on-fiber' devices and applications.

Low Velocity Blunt Impact on Lightweight Composite Sandwich Panels

NASA Astrophysics Data System (ADS)

Chan, Monica Kar

There is an increased desire to incorporate more composite sandwich structures into modern aircrafts. Because in-service aircrafts routinely experience impact damage during maintenance due to ground vehicle collision, dropped equipment, or foreign object damage (FOD) impact, it is necessary to understand their impact characteristics, particularly when blunt impact sources create internal damage with little or no external visibility. The objective of this investigation is to explore damage formation in lightweight composite sandwich panels due to low-velocity impacts of variable tip radius and energy level. The correlation between barely visible external dent formation and internal core damage was explored as a function of impact tip radius. A pendulum impactor was used to impact composite sandwich panels having honeycomb core while held in a 165 mm square window fixture. The panels were impacted by hardened steel tips with radii of 12.7, 25.4, 50.8, and 76.2 mm at energy levels ranging from 2 to 14 J. Experimental data showed little dependence of external dent depth on tip radius at very low energies of 2 to 6 J, and thus, there was also little variation in visibility due to tip radius. Four modes of internal core damage were identified. Internal damage span and depth were dependent on impact tip radius. Damage depth was also radius-dependent, but stabilized at constant depth independent of kinetic energy. Internal damage span increased with increasing impact energy, but not with increasing tip radius, suggesting a relationship between maximum damage tip radius with core density/size.

Multi-function diamond film fiberoptic probe and measuring system employing same

DOEpatents

Young, Jack P.

1998-01-01

A fused fiberoptic probe having a protective cover, a fiberoptic probe system, and embodiments thereof for conducting electromagnetic spectral measurements are disclosed. The fused fiberoptic probe comprises a probe tip having a specific geometrical configuration, an exciting optical fiber and at least one collection optical fiber fused within a housing, preferrably silica, with a protective cover disposed over at least a portion of the probe tip. The specific geometrical configurations in which the probe tip can be shaped include a slanted probe tip with an angle greater than 0.degree., an inverted cone-shaped probe tip, and a lens head.

Cylindrically distributing optical fiber tip for uniform laser illumination of hollow organs

NASA Astrophysics Data System (ADS)

Buonaccorsi, Giovanni A.; Burke, T.; MacRobert, Alexander J.; Hill, P. D.; Essenpreis, Matthias; Mills, Timothy N.

1993-05-01

To predict the outcome of laser therapy it is important to possess, among other things, an accurate knowledge of the intensity and distribution of the laser light incident on the tissue. For irradiation of the internal surfaces of hollow organs, modified fiber tips can be used to shape the light distribution to best suit the treatment geometry. There exist bulb-tipped optical fibers emitting a uniform isotropic distribution of light suitable for the treatment of organs which approximate a spherical geometry--the bladder, for example. For the treatment of organs approximating a cylindrical geometry--e.g. the oesophagus--an optical fiber tip which emits a uniform cylindrical distribution of light is required. We report on the design, development and testing of such a device, the CLD fiber tip. The device was made from a solid polymethylmethacrylate (PMMA) rod, 27 mm in length and 4 mm in diameter. One end was shaped and 'silvered' to form a mirror which reflected the light emitted from the delivery fiber positioned at the other end of the rod. The shape of the mirror was such that the light fell with uniform intensity on the circumferential surface of the rod. This surface was coated with BaSO4 reflectance paint to couple the light out of the rod and onto the surface of the tissue.

Hairlike Percutaneous Photochemical Sensors

NASA Technical Reports Server (NTRS)

George, Thomas; Loeb, Gerald

2004-01-01

Instrumentation systems based on hairlike fiber-optic photochemical sensors have been proposed as minimally invasive means of detecting biochemicals associated with cancer and other diseases. The fiber-optic sensors could be mass-produced as inexpensive, disposable components. The sensory tip of a fiber-optic sensor would be injected through the patient's skin into subcutaneous tissue. A biosensing material on the sensory tip would bind or otherwise react with the biochemical(s) of interest [the analyte(s)] to produce a change in optical properties that would be measured by use of an external photonic analyzer. After use, a fiber-optic sensor could be simply removed by plucking it out with tweezers. A fiber-optic sensor according to the proposal would be of the approximate size and shape of a human hair, and its sensory tip would resemble a follicle. Once inserted into a patient's subcutaneous tissue, the sensor would even more closely resemble a hair growing from a follicle (see Figure 1). The biosensing material on the sensory tip could consist of a chemical and/or cells cultured and modified for the purpose. The biosensing material would be contained within a membrane that would cover the tip. If the membrane were not permeable by an analyte, then it would be necessary to create pores in the membrane that would be large enough to allow analyte molecules to diffuse to the biosensing material, but not so large as to allow cells (if present as part of the biosensing material) to diffuse out. The end of the fiber-optic sensor opposite the sensory tip would be inserted in a fiberoptic socket in the photonic analyzer.

High temperature heat source generation with quasi-continuous wave semiconductor lasers at power levels of 6 W for medical use.

PubMed

Fujimoto, Takahiro; Imai, Yusuke; Tei, Kazuyoku; Ito, Shinobu; Kanazawa, Hideko; Yamaguchi, Shigeru

2014-01-01

We investigate a technology to create a high temperature heat source on the tip surface of the glass fiber proposed for medical surgery applications. Using 4 to 6 W power level semiconductor lasers at a wavelength of 980 nm, a laser coupled fiber tip was preprocessed to contain a certain amount of titanium oxide powder with a depth of 100 μm from the tip surface so that the irradiated low laser energy could be perfectly absorbed to be transferred to thermal energy. Thus, the laser treatment can be performed without suffering from any optical characteristic of the material. A semiconductor laser was operated quasi-continuous wave mode pulse time duration of 180 ms and >95% of the laser energy was converted to thermal energy in the fiber tip. Based on two-color thermometry, by using a gated optical multichannel analyzer with a 0.25 m spectrometer in visible wavelength region, the temperature of the fiber tip was analyzed. The temperature of the heat source was measured to be in excess 3100 K.

Thermal effects from modified endodontic laser tips used in the apical third of root canals with erbium-doped yttrium aluminium garnet and erbium, chromium-doped yttrium scandium gallium garnet lasers.

PubMed

George, Roy; Walsh, Laurence J

2010-04-01

To evaluate the temperature changes occurring on the apical third of root surfaces when erbium-doped yttrium aluminium garnet (Er:YAG) and erbium, chromium-doped yttrium scandium gallium garnet (Er,Cr:YSGG) laser energy was delivered with a tube etched, laterally emitting conical tip and a conventional bare design optical fiber tip. Thermal effects of root canal laser treatments on periodontal ligament cells and alveolar bone are of concern in terms of safety. A total of 64 single-rooted extracted teeth were prepared 1 mm short of the working length using rotary nickel-titanium Pro-Taper files to an apical size corresponding to a F5 Pro-Taper instrument. A thermocouple located 2 mm from the apex was used to record temperature changes arising from delivery of laser energy through laterally emitting conical tips or plain tips, using an Er:YAG or Er,Cr:YSGG laser. For the Er:YAG and Er,Cr:YSGG systems, conical fibers showed greater lateral emissions (452 + 69% and 443 + 64%) and corresponding lower forward emissions (48 + 5% and 49 + 5%) than conventional plain-fiber tips. All four combinations of laser system and fiber design elicited temperature increases less than 2.5 degrees C during lasing. The use of water irrigation attenuated completely the thermal effects of individual lasing cycles. Laterally emitting conical fiber tips can be used safely under defined conditions for intracanal irradiation without harmful thermal effects on the periodontal apparatus.

An optical fiber bundle sensor for tip clearance and tip timing measurements in a turbine rig.

PubMed

García, Iker; Beloki, Josu; Zubia, Joseba; Aldabaldetreku, Gotzon; Illarramendi, María Asunción; Jiménez, Felipe

2013-06-05

When it comes to measuring blade-tip clearance or blade-tip timing in turbines, reflective intensity-modulated optical fiber sensors overcome several traditional limitations of capacitive, inductive or discharging probe sensors. This paper presents the signals and results corresponding to the third stage of a multistage turbine rig, obtained from a transonic wind-tunnel test. The probe is based on a trifurcated bundle of optical fibers that is mounted on the turbine casing. To eliminate the influence of light source intensity variations and blade surface reflectivity, the sensing principle is based on the quotient of the voltages obtained from the two receiving bundle legs. A discrepancy lower than 3% with respect to a commercial sensor was observed in tip clearance measurements. Regarding tip timing measurements, the travel wave spectrum was obtained, which provides the average vibration amplitude for all blades at a particular nodal diameter. With this approach, both blade-tip timing and tip clearance measurements can be carried out simultaneously. The results obtained on the test turbine rig demonstrate the suitability and reliability of the type of sensor used, and suggest the possibility of performing these measurements in real turbines under real working conditions.

An Optical Fiber Bundle Sensor for Tip Clearance and Tip Timing Measurements in a Turbine Rig

PubMed Central

García, Iker; Beloki, Josu; Zubia, Joseba; Aldabaldetreku, Gotzon; Illarramendi, María Asunción; Jiménez, Felipe

2013-01-01

When it comes to measuring blade-tip clearance or blade-tip timing in turbines, reflective intensity-modulated optical fiber sensors overcome several traditional limitations of capacitive, inductive or discharging probe sensors. This paper presents the signals and results corresponding to the third stage of a multistage turbine rig, obtained from a transonic wind-tunnel test. The probe is based on a trifurcated bundle of optical fibers that is mounted on the turbine casing. To eliminate the influence of light source intensity variations and blade surface reflectivity, the sensing principle is based on the quotient of the voltages obtained from the two receiving bundle legs. A discrepancy lower than 3% with respect to a commercial sensor was observed in tip clearance measurements. Regarding tip timing measurements, the travel wave spectrum was obtained, which provides the average vibration amplitude for all blades at a particular nodal diameter. With this approach, both blade-tip timing and tip clearance measurements can be carried out simultaneously. The results obtained on the test turbine rig demonstrate the suitability and reliability of the type of sensor used, and suggest the possibility of performing these measurements in real turbines under real working conditions. PMID:23739163

Meta-tips for lab-on-fiber optrodes

NASA Astrophysics Data System (ADS)

Principe, M.; Consales, M.; Micco, A.; Crescitelli, A.; Castaldi, G.; Esposito, E.; La Ferrara, V.; Cutolo, A.; Galdi, V.; Cusano, A.

2016-05-01

We realize the first optical-fiber "meta-tip" that integrates a metasurface on the tip of an optical fiber. In our proposed configuration a Babinet-inverted plasmonic metasurface is fabricated by patterning (via focused-ion-beam) an array of rectangular aperture nanoantennas in a thin gold film. Via spatial modulation of the nanoantennas size, we properly tune their resonances so as to impress abrupt arbitrary phase variations in the transmitted field wavefront. As a proof-of-principle, we fabricate and characterize several prototypes implementing in the near-infrared the beam-steering with various angles. We also explore the limit case where surface waves are excited, and its capability to work as refractive index sensors. Notably, its sensitivity overwhelms that of the corresponding gradient-free plasmonic array, thus paving the way to the use of metasurfaces for label-free chemical and biological sensing. Our experimental results, in fairly good agreement with numerical predictions, demonstrate the practical feasibility of the meta-tip concept, and set the stage for the integration of metasurfaces, and their exceptional capabilities to manipulate light, in fiber-optics technological platforms, within the emerging "lab-on-fiber" paradigm.

New Technique for Fabrication of Scanning Single-Electron Transistor Microscopy Tips

NASA Astrophysics Data System (ADS)

Goodwin, Eric; Tessmer, Stuart

Fabrication of glass tips for Scanning Single-Electron Transistor Microscopy (SSETM) can be expensive, time consuming, and inconsistent. Various techniques have been tried, with varying levels of success in regards to cost and reproducibility. The main requirement for SSETM tips is to have a sharp tip ending in a micron-scale flat face to allow for deposition of a quantum dot. Drawing inspiration from methods used to create tips from optical fibers for Near-Field Scanning Optical Microscopes, our group has come up with a quick and cost effective process for creating SSETM tips. By utilizing hydrofluoric acid to etch the tips and oleic acid to guide the etch profile, optical fiber tips with appropriate shaping can be rapidly prepared. Once etched, electric leads are thermally evaporated onto each side of the tip, while an aluminum quantum dot is evaporated onto the face. Preliminary results using various metals, oxide layers, and lead thicknesses have proven promising.

Plasma treatment of fiber facets for increased (de)mating endurance in physical contact fiber connectors

NASA Astrophysics Data System (ADS)

Van Erps, Jürgen; Voss, Kevin; De Witte, Martijn; Radulescu, Radu; Beri, Stefano; Watté, Jan; Thienpont, Hugo

2016-04-01

It is known that cleaving an optical fiber introduces a number of irregularities and defects to the fiber's end-face, such as hackles and shockwaves. These defects can act as failure initiators when stress is applied to the end-face. Given the fiber's small diameter of 125 ffm, a large amount of mechanical stress can be expected to be applied on its end-face during the mating-demating cycle. In addition, a connector in a fiber-to-the-home (FTTH) network can be expected to be mated and demated more than 30 times during its lifetime for purposes such as testing, churning, or provisioning. For this reason, the performance of a connector that displays low optical loss when first installed can dramatically degrade after few mating-demating cycles and catastrophic connector failure due to end-face breakage is likely. We present plasma discharge shaping of cleaved fiber tips to strongly improve the endurance of the fibers to repeated mating-demating cycles. We quantify the dependency of the plasma-induced surface curvature of the fiber tip on the plasma duration and on the position of the fiber tip within the plasma cloud. Finally we present data showing the improved endurance of fibers that are exposed to plasma compared to conventional as-cleaved fibers.

Wavefront sensing and adaptive control in phased array of fiber collimators

NASA Astrophysics Data System (ADS)

Lachinova, Svetlana L.; Vorontsov, Mikhail A.

2011-03-01

A new wavefront control approach for mitigation of atmospheric turbulence-induced wavefront phase aberrations in coherent fiber-array-based laser beam projection systems is introduced and analyzed. This approach is based on integration of wavefront sensing capabilities directly into the fiber-array transmitter aperture. In the coherent fiber array considered, we assume that each fiber collimator (subaperture) of the array is capable of precompensation of local (onsubaperture) wavefront phase tip and tilt aberrations using controllable rapid displacement of the tip of the delivery fiber at the collimating lens focal plane. In the technique proposed, this tip and tilt phase aberration control is based on maximization of the optical power received through the same fiber collimator using the stochastic parallel gradient descent (SPGD) technique. The coordinates of the fiber tip after the local tip and tilt aberrations are mitigated correspond to the coordinates of the focal-spot centroid of the optical wave backscattered off the target. Similar to a conventional Shack-Hartmann wavefront sensor, phase function over the entire fiber-array aperture can then be retrieved using the coordinates obtained. The piston phases that are required for coherent combining (phase locking) of the outgoing beams at the target plane can be further calculated from the reconstructed wavefront phase. Results of analysis and numerical simulations are presented. Performance of adaptive precompensation of phase aberrations in this laser beam projection system type is compared for various system configurations characterized by the number of fiber collimators and atmospheric turbulence conditions. The wavefront control concept presented can be effectively applied for long-range laser beam projection scenarios for which the time delay related with the double-pass laser beam propagation to the target and back is compared or even exceeds the characteristic time of the atmospheric turbulence change - scenarios when conventional target-in-the-loop phase-locking techniques fail.

Laser fiber cleaving techniques: effects on tip morphology and power output.

PubMed

Vassantachart, Janna M; Lightfoot, Michelle; Yeo, Alexander; Maldonado, Jonathan; Li, Roger; Alsyouf, Muhannad; Martin, Jacob; Lee, Michael; Olgin, Gaudencio; Baldwin, D Duane

2015-01-01

Proper cleaving of reusable laser fibers is needed to maintain optimal functionality. This study quantifies the effect of different cleaving tools on power output of the holmium laser fiber and demonstrates morphologic changes using microscopy. The uncleaved tips of new 272 μm reusable laser fibers were used to obtain baseline power transmission values at 3 W (0.6 J, 5 Hz). Power output for each of four cleaving techniques-11-blade scalpel, scribe pen cleaving tool, diamond cleaving wheel, and suture scissors-was measured in a single-blinded fashion. Dispersion of light from the fibers was compared with manufacturer specifications and rated as "ideal," "acceptable," or "unacceptable" by blinded reviewers. The fiber tips were also imaged using confocal and scanning electron microscopy. Independent samples Kruskal-Wallis test and chi square were used for statistical analysis (α<0.05). New uncleaved fiber tips transmitted 3.04 W of power and were used as a reference (100%). The scribe pen cleaving tool produced the next highest output (97.1%), followed by the scalpel (83.4%), diamond cleaving wheel (77.1%), and suture scissors (61.7%), a trend that was highly significant (P<0.001). On pairwise comparison, no difference in power output was seen between the uncleaved fiber tips and those cleaved with the scribe pen (P=1.0). The rating of the light dispersion patterns from the different cleaving methods followed the same trend as the power output results (P<0.001). Microscopy showed that the scribe pen produced small defects along the fiber cladding but maintained a smooth, flat core surface. The other cleaving techniques produced defects on both the core and cladding. Cleaving techniques produce a significant effect on the initial power transmitted by reusable laser fibers. The scribe pen cleaving tool produced the most consistent and highest average power output.

Evaluation of hollow fiberoptic tips for the conduction of Er:YAG laser.

PubMed

Alves, Paulo Roberto Vieira; Aranha, Norberto; Alfredo, Edson; Marchesan, Melissa Andréia; Brugnera Junior, Aldo; Sousa-Neto, Manoel D

2005-08-01

The use of Er:YAG laser operating in the 3 microm range with adjustable power and pulses has become popular for dental and medical practice due to its high photoablative capacity, surgical precision and antimicrobial action. The existing fiberoptic tips irradiate lasers parallel to the long axes of the tooth limiting its efficiency in the root canal. We evaluated hollow fiberoptic tips obtained from silicate glass as a means of Er:YAG laser conduction in dental procedures. The fiber tips were molded from capillary tubes with different profiles so that their ends would have cylindric, conical or spherical shapes. The performance of the three fibers as a means of propagation of Er:YAG (lambda = 2.94 microm) laser radiation was compared to that of a solid sapphire fiber at 10 Hz and 200 mJ and of 20 Hz and 500 mJ. The profiles of frontal and lateral burning were visualized on thermal paper. Analysis of these profiles demonstrated that the sapphire tip and the hollow fiber of cylindric section did not differ significantly in the profiles of frontal burning, and no lateral burning was detected. The fibers of the conical and spherical sections, although presenting attenuation in the frontal output power, showed a larger burning area in the frontal profile, in addition to producing lateral burning. The results indicate that commercial hollow fiberoptics have advantages such as easy manufacture of the different tip shapes, great adaptability, low cost, and a low loss of transmission.

Analysis and experimental demonstration of conformal adaptive phase-locked fiber array for laser communications and beam projection applications

NASA Astrophysics Data System (ADS)

Liu, Ling

The primary goal of this research is the analysis, development, and experimental demonstration of an adaptive phase-locked fiber array system for free-space optical communications and laser beam projection applications. To our knowledge, the developed adaptive phase-locked system composed of three fiber collimators (subapertures) with tip-tilt wavefront phase control at each subaperture represents the first reported fiber array system that implements both phase-locking control and adaptive wavefront tip-tilt control capabilities. This research has also resulted in the following innovations: (a) The first experimental demonstration of a phase-locked fiber array with tip-tilt wave-front aberration compensation at each fiber collimator; (b) Development and demonstration of the fastest currently reported stochastic parallel gradient descent (SPGD) system capable of operation at 180,000 iterations per second; (c) The first experimental demonstration of a laser communication link based on a phase-locked fiber array; (d) The first successful experimental demonstration of turbulence and jitter-induced phase distortion compensation in a phase-locked fiber array optical system; (e) The first demonstration of laser beam projection onto an extended target with a randomly rough surface using a conformal adaptive fiber array system. Fiber array optical systems, the subject of this study, can overcome some of the draw-backs of conventional monolithic large-aperture transmitter/receiver optical systems that are usually heavy, bulky, and expensive. The primary experimental challenges in the development of the adaptive phased-locked fiber-array included precise (<5 microrad) alignment of the fiber collimators and development of fast (100kHz-class) phase-locking and wavefront tip-tilt control systems. The precise alignment of the fiber collimator array is achieved through a specially developed initial coarse alignment tool based on high precision piezoelectric picomotors and a dynamic fine alignment mechanism implemented with specially designed and manufactured piezoelectric fiber positioners. Phase-locking of the fiber collimators is performed by controlling the phases of the output beams (beamlets) using integrated polarization-maintaining (PM) fiber-coupled LiNbO3 phase shifters. The developed phase-locking controllers are based on either the SPGD algorithm or the multi-dithering technique. Subaperture wavefront phase tip-tilt control is realized using piezoelectric fiber positioners that are controlled using a computer-based SPGD controller. Both coherent (phase-locked) and incoherent beam combining in the fiber array system are analyzed theoretically and experimentally. Two special fiber-based beam-combining testbeds have been built to demonstrate the technical feasibility of phase-locking compensation prior to free-space operation. In addition, the reciprocity of counter-propagating beams in a phase-locked fiber array system has been investigated. Coherent beam combining in a phase-locking system with wavefront phase tip-tilt compensation at each subaperture is successfully demonstrated when laboratory-simulated turbulence and wavefront jitters are present in the propagation path of the beamlets. In addition, coherent beam combining with a non-cooperative extended target in the control loop is successfully demonstrated.

Endoluminal laser delivery mode and wavelength effects on varicose veins in an ex vivo model.

PubMed

Massaki, Ane B M N; Kiripolsky, Monika G; Detwiler, Susan P; Goldman, Mitchel P

2013-02-01

Endovenous laser ablation (EVLA) has been shown to be effective for the elimination of saphenous veins and associated reflux. Mechanism is known to be heat related, but precise way in which heat causes vein ablation is not completely known. This study aimed to determine the effects of various endovenous laser wavelengths and delivery modes on ex vivo human vein both macroscopically and microscopically. We also evaluated whether protected-tip fibers, consisting of prototype silica fibers with a metal tube over the distal end, reduced vein wall perforations compared with non-protected-tip fibers. An ex vivo EVLA model with human veins harvested during ambulatory phlebectomy procedures was used. Six laser fiber combinations were tested: 810 nm continuous wave (CW) diode laser with a flat tip fiber, 810 CW diode laser with a protected tip fiber, 1,320 nm pulsed Nd:YAG laser, 1,310 nm CW diode laser, 1,470 nm CW diode laser, and 2,100 nm pulsed Ho:YAG laser. Perforation or full thickness necrosis of a portion of the vein wall was observed in 5/11 (45%), 0/11 (0%), 3/22 (14%), 7/11 (64%), 4/6 (67%), and 5/10 (50%) of cross-sections of veins treated with the 810 nm CW diode laser with a flat tip fiber, the 810 CW diode laser with a protected tip fiber, the 1,320 nm pulsed Nd:YAG laser, the 1,310 nm CW diode laser, the 1,470 nm CW diode laser, and the 2,100 nm pulsed Ho:YAG laser, respectively. Our results have shown that the delivery mode, pulsed Nd:YAG versus CW, may be just as important as the wavelength. Therefore, the 1,310 nm CW laser may not be equivalent to the 1,320 nm pulsed laser. In addition, protected 810 nm fibers may be less likely to yield wall perforations than their non-protected counterparts. Copyright © 2012 Wiley Periodicals, Inc.

A Novel, High-Resolution, High-Speed Fiber-Optic Temperature Sensor for Oceanographic Applications

DTIC Science & Technology

2015-05-11

attached to the endface of a cleaved single-mode fiber using UV curable glue . A novel signal processing method has also been developed for the...thick Si wafer was bonded onto the tip of a single mode optical fiber using UV -curable glue . In addition to the sensor shown in Fig. 1(b), sensor...we developed a process to introduce much thicker silicon pieces onto the optical fiber tip. UV curable glue was first attached to the endface of

Needle tip visualization by bevel-point ultrasound generator and prototype photoacoustic imaging system

NASA Astrophysics Data System (ADS)

Irisawa, Kaku; Murakoshi, Dai; Hashimoto, Atsushi; Yamamoto, Katsuya; Hayakawa, Toshiro

2017-03-01

Visualization of the tip of medical devices like needles or catheters under ultrasound imaging has been a continuous topic since the early 1980's. In this study, a needle tip visualization system utilizing photoacoustic effects is proposed. In order to visualize the needle tip, an optical fiber was inserted into a needle. The optical fiber tip is placed on the needle bevel and affixed with black glue. The pulsed laser light from laser diode was transferred to the optical fiber and converted to ultrasound due to laser light absorption of the black glue and the subsequent photoacoustic effect. The ultrasound is detected by transducer array and reconstructed into photoacoustic images in the ultrasound unit. The photoacoustic image is displayed with a superposed ultrasound B-mode image. As a system evaluation, the needle is punctured into bovine meat and the needle tip is observed with commercialized conventional linear transducers or convex transducers. The needle tip is visualized clearly at 7 and 12 cm depths with linear and convex probes, respectively, even with a steep needle puncture angle of around 90 degrees. Laser and acoustic outputs, and thermal rise at the needle tip, were measured and were well below the limits of the safety standards. Compared with existing needle tip visualization technologies, the photoacoustic needle tip visualization system has potential distinguishable features for clinical procedures related with needle puncture and injection.

Retinotomy using an erbium:YAG laser on human autopsy eyes

NASA Astrophysics Data System (ADS)

Ellsworth, Lansing G.; Kramer, Theresa R.; Noecker, Robert J.; Snyder, Robert W.; Yarborough, J. Michael

1994-06-01

Mid-IR lasers that operate near the absorption peak of water have a short penetration depth in ocular tissues. Ablation of tissue can be accomplished with minimal coagulative damage to underlying structures. We used an erbium:YAG laser equipped with a contact probe to create retinotomy sites in the human retina of eye bank eyes. An erbium:YAG laser (2.94 micrometers ) equipped with an infrared transmitting glass fiber and a sapphire tip (400 micrometers ) was used to directly ablate the surface of the retina. We administered both single and multiple pulses to the macula and peripheral retina using energy levels from 4 to 16 mJ per pulse. The retinas were then examined histopathologically to evaluate the extent of ablation and coagulative damage. Single pulses at low energy levels were noted to cause ablative damage to the nerve fiber layer and ganglion cell layer without a notable coagulative effect. The mean ablation depth at lower energy levels was less than the mean ablation depth at higher energy levels. Extensive laser application produced disruption of the retinal pigment epithelium, choroid and sclera. the erbium:YAG laser equipped with a contact probe is an effective means of creating retinotomies in human autopsy eyes. When used in the single pulse mode at lower energy levels, the erbium:YAG laser appears capable of removing superficial retinal layers without damaging deeper structures.

Photonic jet: key role of injection for etchings with a shaped optical fiber tip.

PubMed

Pierron, Robin; Zelgowski, Julien; Pfeiffer, Pierre; Fontaine, Joël; Lecler, Sylvain

2017-07-15

We demonstrate the key role of the laser injection into a multimode fiber to obtain a photonic jet (PJ). PJ, a high concentrated propagating beam with a full width at half-maximum smaller than the diffraction limit, is here generated with a shaped optical fiber tip using a pulsed laser source (1064 nm, 100 ns, 35 kHz). Three optical injection systems of light are compared. For similar etched marks on silicon with diameters around 1 μm, we show that the required ablation energy is minimum when the injected light beam is close to the fundamental mode diameter of the fiber. Thus, we confirm experimentally that to obtain a PJ out of an optical fiber, light injection plays a role as important as that of the tip shape and, therefore, the role of the fundamental mode in the process.

Sirt1 physically interacts with Tip60 and negatively regulates Tip60-mediated acetylation of H2AX

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

Yamagata, Kazutsune, E-mail: kyamagat@ncc.go.jp; Kitabayashi, Issay

2009-12-25

Sirt1 appear to be NAD(+)-dependent deacetylase that deacetylates histones and several non-histone proteins. In this study, we identified Sirt1 as a physical interaction partner of Tip60, which is a mammalian MYST-type histone acetyl-transferase that specifically acetylates histones H2A and H4. Although Tip60 also acetylates DNA damage-specific histone H2A variant H2AX in response to DNA damage, which is a process required for appropriate DNA damage response, overexpression of Sirt1 represses Tip60-mediated acetylation of H2AX. Furthermore, Sirt1 depletion by RNAi causes excessive acetylation of H2AX, and enhances accumulation of {gamma}-ray irradiation-induced MDC1, BRCA1, and Rad51 foci in nuclei. These findings suggest thatmore » Sirt1 functions as negative regulator of Tip60-mediated acetylation of H2AX. Moreover, Sirt1 deacetylates an acetylated Tip60 in response to DNA damage and stimulates proteasome-dependent Tip60 degradation in vivo, suggesting that Sirt1 negatively regulates the protein level of Tip60 in vivo. Sirt1 may thus repress excessive activation of the DNA damage response and Rad51-homologous recombination repair by suppressing the function of Tip60.« less

Fabry-Perot interferometer fiber tip sensor based on a glass microsphere glued at the etched end of multimode fiber

NASA Astrophysics Data System (ADS)

Chen, Weiping P.; Wang, Dongning N.; Xu, Ben; Wang, Zhaokun K.; Zhao, Chun-Liu

2017-05-01

We demonstrate an optical Fabry-Perot interferometer fiber tip sensor based on a glass microsphere glued at the etched end of a multimode fiber. The fiber device is miniature and robust, with a convenient reflection mode of operation, a high temperature sensitivity of 202.6 pm/°C within the range from 5°C to 90°C, a good refractive index sensitivity of ˜119 nm/RIU within the range from 1.331 to 1.38, and a gas pressure sensitivity of 0.19 dB/MPa.

Turbine blade tip clearance measurement using a skewed dual-beam fiber optic sensor

NASA Astrophysics Data System (ADS)

Ye, De-chao; Duan, Fa-jie; Guo, Hao-tian; Li, Yangzong; Wang, Kai

2012-08-01

Optimization and active control of the tip clearance of turbine blades has been identified as a key to improve fuel efficiency, reduce emission, and increase service life of the engine. However, reliable and real-time tip clearance measurement is difficult due to the adverse environmental conditions that are typically found in a turbine. We describe a dual-beam fiber optic measurement system that can measure the tip timing and tip clearance simultaneously. Because the tip timing information is used to calculate the tip clearance, the method is insensitive to the signal intensity variation caused by fluctuations in environmental conditions such as light source instability, contamination, and blade tip imperfection. The system was calibrated and tested using experimental rotors. The test results indicated a high resolution of 4.5 μm and measurement accuracy of ±20 μm over the rotation speed range of 2000 to 10,000 rpm.

Integrated Fiber-Optic Light Probe: Measurement of Static Deflections in Rotating Turbomachinery

NASA Technical Reports Server (NTRS)

Kurkov, Anatole P.

1998-01-01

At the NASA Lewis Research Center, in cooperation with Integrated Fiber Optic Systems, Inc., an integrated fiber-optic light probe system was designed, fabricated, and tested for monitoring blade tip deflections, vibrations, and to some extent, changes in the blade tip clearances of a turbomachinery fan or a compressor rotor. The system comprises a set of integrated fiber-optic light probes that are positioned to detect the passing blade tip at the leading and trailing edges. In this configuration, measurements of both nonsynchronous blade vibrations and steady-state blade deflections can be made from the timing information provided by each light probe-consisting of an integrated fiber-optic transmitting channel and numerical aperture receiving fibers, all mounted in the same cylindrical housing. With integrated fiber-optic technology, a spatial resolution of 50 mm is possible while the outer diameter is kept below 2.5 mm. To evaluate these probes, we took measurements in a single-stage compressor facility and an advanced fan rig in Lewis' 9- by 15-Foot Low-Speed Wind Tunnel.

Novel cylindrical illuminator tip for ultraviolet light delivery

NASA Astrophysics Data System (ADS)

Shangguan, HanQun; Haw, Thomas E.; Gregory, Kenton W.; Casperson, Lee W.

1993-06-01

The design, processing, and sequential testing of a novel cylindrical diffusing optical fiber tip for ultraviolet light delivery is described. This device has been shown to uniformly (+/- 15%) illuminate angioplasty balloons, 20 mm in length, that are used in an experimental photochemotherapeutic treatment of swine intimal hyperplasia. Our experiments show that uniform diffusing tips of < 400 micron diameter can be reliably constructed for this and other interstitial applications. Modeling results indicate that this design is scalable to smaller diameters. The diffusing tips are made by stripping the protective buffer and etching away the cladding over a length of 20 mm from the fiber tip and replacing it with a thin layer of optical epoxy mixed with Al2O3 powder. To improve the uniformity and ease of fabrication, we have evaluated a new device configuration where the tip is etched into a modified conical shape, and the distal end face is polished and then coated with an optically opaque epoxy. This is shown to uniformly scatter approximately 70% of the light launched into the fiber without forward transmission.

Nano-cone optical fiber array sensors for MiRNA profiling

NASA Astrophysics Data System (ADS)

Wang, Yunshan; Senapati, Satyajyoti; Stoddart, Paul; Howard, Scott; Chang, Hsueh-Chia

2013-09-01

Up/down regulation of microRNA panels has been correlated to cardiovascular diseases and cancer. Frequent miRNA profiling at home can hence allow early cancer diagnosis and home-use chronic disease monitoring, thus reducing both mortality rate and healthcare cost. However, lifetime of miRNAs is less than 1 hour without preservation and their concentrations range from pM to mM. Despite rapid progress in the last decade, modern nucleic acid analysis methods still do not allow personalized miRNA profiling---Real-time PCR and DNA micro-array both require elaborate miRNA preservation steps and expensive equipment and nano pore sensors cannot selectively quantify a large panel with a large dynamic range. We report a novel and low-cost optical fiber sensing platform, which has the potential to profile a panel of miRNA with simple LED light sources and detectors. The individual tips of an optical imaging fiber bundle (mm in diameter with 7000 fiber cores) were etched into cones with 10 nm radius of curvature and coated with Au. FRET (Forster Resonant Energy Transfer) hairpin oligo probes, with the loop complementary to a specific miRNA that can release the hairpin, were functionalized onto the conic tips. Exciting light in the optical fiber waveguide is optimally coupled to surface plasmonics on the gold surface, which then converges to the conic tips with two orders of magnitude enhancement in intensity. Unlike nanoparticle plasmonics, tip plasmonics can be excited over a large band width and hence the plasmonic enhanced fluorescence signal of the FRET reporter is also focused towards the tip--- and is further enhanced with the periodic resonant grid of the fiber array which gives rise to pronounced standing wave interference patterns. Multiplexing is realized by functionalizing different probes onto one fiber bundle using a photoactivation process.

Excitation of surface plasmons in Al-coated SNOM tips

NASA Astrophysics Data System (ADS)

Palm, Viktor; Rähn, Mihkel; Jäme, Joonas; Hizhnyakov, Vladimir

2012-10-01

The mesoscopic effect of spectral modulation occurring due to the interference of two photonic fiber modes filtered out by a metal-coated SNOM tip is used to observe the surface plasmon polariton (SPP) excitation in SNOM tips. In a spectrum of the broadband light transmitted by a SNOM tip a region of highly regular spectral modulation can be found, indicating the spectral interval in which only two photonic modes (apparently HE11 and TM01) are transmitted with significant and comparable amplitudes. The modulation period yields the value of optical path difference (OPD) for this pair of modes. Due to the multimode fiber's inherent modal dispersion, this OPD value depends linearly on the fiber tail length l. An additional contribution to OPD can be generated in a metal-coated SNOM tip due to a mode-dependent photon-plasmon coupling strength resulting in generation of SPPs with different propagation velocities. For an Al-coated 200 nm SNOM tip spectra of transmitted light have been registered for ten different l values. An extrapolation of the linear OPD (l) dependence to l=0 yields a significant residual OPD value, indicating according to our theoretical considerations a mode-selective SPP excitation in the metal-coated tip. The modal dispersion is shown to switch its sign in the SNOM tip. First results of analogous experiments with an Al-coated 150 nm SNOM tip confirm our conclusions.

Fiber-optic Singlet Oxygen [1O2 (1Δg)] Generator Device Serving as a Point Selective Sterilizer

PubMed Central

Aebisher, David; Zamadar, Matibur; Mahendran, Adaickapillai; Ghosh, Goutam; McEntee, Catherine; Greer, Alexander

2016-01-01

Traditionally, Type II heterogeneous photo-oxidations produce singlet oxygen via external irradiation of a sensitizer and external supply of ground-state oxygen. A potential improvement is reported here. A hollow-core fiber-optic device was developed with an “internal” supply of light and flowing oxygen, and a porous photosensitizer-end capped configuration. Singlet oxygen was delivered through the fiber tip. The singlet oxygen steady-state concentration in the immediate vicinity of the probe tip was ca 20 fM by N-benzoyl-DL-methionine trapping. The device is portable and the singlet oxygen-generating tip is maneuverable, which opened the door to simple disinfectant studies. Complete Escherichia coli inactivation was observed in 2 h when the singlet oxygen sensitizing probe tip was immersed in 0.1 mL aqueous samples of 0.1–4.4 × 107 cells. Photobleaching of the probe tip occurred after ca 12 h of use, requiring baking and sensitizer reloading steps for reuse. PMID:20497367

Comparison to the scanning electron microscope of professional dental hygiene methods on metal-free layered structures and metal-free monolithic structures processed by different polymerization cycles.

PubMed

Ermetici, M; Segù, M; Butera, A

2014-06-01

Aim of the study was to find effective instrumental methodologies and procedures for scaling and deplaquing without compromising the structure of metal-free, monolithic lithium disilicate and layered zirconia prosthetics. Of 14 decontaminated, extracted teeth in good anatomical condition, 7 veneers lithium disilicate monolithic and 7 layered zirconia crowns were prepared for testing and divided into 6 treatment groups. Each group was composed of a veneer and a crown. The division of the groups was carried out according to the type of treatment performed- instrumental carbon fiber and steel tips, prophylaxis paste with high and low RDA (Relative dentin abrasion), bicarbonate powder. Samples were examined and observed through a scanning electron microscope (SEM). Afterwards a detailed comparison of the images of treated and untreated samples was performed. The images were at the same magnification, thus showing the differences in the treated samples. The monolithic lithium disilicate presents minor damage to the surface but no excessive changes to the structure in general post treatment. The layered zirconia resulted in notable damage with evident abrasions on the layered ceramic structure after the use of ultrasound with a steel tip and air flow with bicarbonate. Carbon fibre tips and prophylaxis paste containing perlite and low RDA did not create notable changes to the properties of the materials in question. The results of the disilicate monolithic appear to show it to be a much more resistant material compared to layered zirconia in ceramic. Its resistance is demonstrated by the lack of notable damage in all the treatment groups.

Purification process for vertically aligned carbon nanofibers

NASA Technical Reports Server (NTRS)

Nguyen, Cattien V.; Delziet, Lance; Matthews, Kristopher; Chen, Bin; Meyyappan, M.

2003-01-01

Individual, free-standing, vertically aligned multiwall carbon nanotubes or nanofibers are ideal for sensor and electrode applications. Our plasma-enhanced chemical vapor deposition techniques for producing free-standing and vertically aligned carbon nanofibers use catalyst particles at the tip of the fiber. Here we present a simple purification process for the removal of iron catalyst particles at the tip of vertically aligned carbon nanofibers derived by plasma-enhanced chemical vapor deposition. The first step involves thermal oxidation in air, at temperatures of 200-400 degrees C, resulting in the physical swelling of the iron particles from the formation of iron oxide. Subsequently, the complete removal of the iron oxide particles is achieved with diluted acid (12% HCl). The purification process appears to be very efficient at removing all of the iron catalyst particles. Electron microscopy images and Raman spectroscopy data indicate that the purification process does not damage the graphitic structure of the nanotubes.

Tissue dissection using a 1470-nm diode laser and laparoscopic prototype

NASA Astrophysics Data System (ADS)

Chang, Chun-Hung; Hammerland, John; Nau, William H.; Fried, Nathaniel M.

2017-02-01

A continuous-wave, 40 Watt, 1470 nm laser was explored for rapid and precise dissection of porcine mesentery fascia and liver tissues, ex vivo. Laser energy was delivered through a 550-μm-core optical fiber inside a 5-mm-OD, laparoscopic probe, with detachable, 2 mm, sapphire ball rolling tip. Fascia tissue was cleanly dissected with scanning rates from 2.0 - 4.5 mm/s using 16 - 31W. Fascia collateral thermal damage measured as low as 180 +/- 50 μm at 4.5 mm/s scan speed. Porcine liver ablation crater depth measured up to 1010 +/- 220 μm with 30 W at 2.0 mm/s or as shallow as 80 +/- 30 μm with 10 W at 10 mm/s. Peak temperatures reached 130 °C at ball tip and 75 °C on metal jaws. The 1470-nm laser and probe show promise for laparoscopic tissue cutting and coagulation.

General Tips Concerning What Has Been Learned About Cotton Processing in Traditional Textile Manufacturing

USDA-ARS?s Scientific Manuscript database

This article, under the following sub-headings, briefly describes a few important practical tips involving processing of cotton in traditional textile manufacturing: (1)Bale Selection and Fiber Mixing, (2) Fiber Opening and Cleaning, (3) Carding, (4) Drawing, (5) Combing (if necessary), (6) Roving, ...

Fiber-optic laser Doppler turbine tip clearance probe

NASA Astrophysics Data System (ADS)

Büttner, Lars; Pfister, Thorsten; Czarske, Jürgen

2006-05-01

A laser Doppler based method for in situ single blade tip clearance measurements of turbomachines with high precision is presented for what we believe is the first time. The sensor is based on two superposed fanlike interference fringe systems generated by two laser wavelengths from a fiber-coupled, passive, and therefore compact measurement head employing diffractive optics. Tip clearance measurements at a transonic centrifugal compressor performed during operation at 50,000 rpm (833 Hz, 586 m/s tip speed) are reported. At these speeds the measured uncertainty of the tip position was less than 20 μm, a factor of 2 more accurate than that of capacitive probes. The sensor offers great potential for in situ and online high-precision tip clearance measurements of metallic and nonmetallic turbine blades.

Fiber-optic laser Doppler turbine tip clearance probe.

PubMed

Büttner, Lars; Pfister, Thorsten; Czarske, Jürgen

2006-05-01

A laser Doppler based method for in situ single blade tip clearance measurements of turbomachines with high precision is presented for what we believe is the first time. The sensor is based on two superposed fanlike interference fringe systems generated by two laser wavelengths from a fiber-coupled, passive, and therefore compact measurement head employing diffractive optics. Tip clearance measurements at a transonic centrifugal compressor performed during operation at 50,000 rpm (833 Hz, 586 m/s tip speed) are reported. At these speeds the measured uncertainty of the tip position was less than 20 microm, a factor of 2 more accurate than that of capacitive probes. The sensor offers great potential for in situ and online high-precision tip clearance measurements of metallic and nonmetallic turbine blades.

Optical characteristics of modified fiber tips in single fiber, laser Doppler flowmetry

NASA Astrophysics Data System (ADS)

Oberg, P. Ake; Cai, Hongming; Rohman, Hakan; Larsson, Sven-Erik

1994-02-01

Percutaneous laser Doppler flowmetry (LDF) and bipolar surface electromyography (EMG) were used simultaneously for measurement of skeletal muscle (trapezius) perfusion in relation to static load and fatigue. On-line computer (386 SX) processing of the LDF- and EMG- signals made possible interpretation of the relationship between the perfusion and the activity of the muscle. The single fiber laser Doppler technique was used in order to minimize the trauma. A ray-tracing program was developed in the C language by which the optical properties of the fiber and fiber ends could be simulated. Isoirradiance graphs were calculated for three fiber end types and the radiance characteristics were measured for each fiber end. The three types of fiber-tips were evaluated and compared in flow model measurements.

Improved extrinsic polymer optical fiber sensors for gamma-ray monitoring in radioprotection applications

NASA Astrophysics Data System (ADS)

de Andrés, A. I.; Esteban, Ó.; Embid, M.

2017-08-01

Gamma radiation detection in the range of 662 keV, the reference for environmental protection, is done through extrinsic optical fiber sensors. The fluorescence rendered by an inorganic scintillator when irradiated with such gamma rays is gathered by a modified polymer optical fiber tip. This modification increases the recorded signal when compared with plain unaltered fiber. Two fiber tip modification are then compared in terms of light gathering capability. A chemically etched fiber, in which the cladding and part of the core are removed, and a tapered fiber in which the core-cladding structure is kept. Both structures are comparable in length and final diameter, and show linear response in the tested range up to 2 Gy/h air Kerma rate. The etched fiber shows a higher slope than the tapered one, although both improve the signal gathered by a plain fiber tip. The easy fabrication and handling of the reported transducers, together with the improved signal gathering, allow to reduce the overall system budget with the use of low-cost optoelectronics in the detection stage. This offers a significant improvement for surveillance systems in radioprotection applications, in which presence of gamma radiation coming out accidental leakage or spurious sources activity is the main target.

Off-axis reflective optical apparatus

NASA Technical Reports Server (NTRS)

Ames, Lawrence L. (Inventor); Leary, David F. (Inventor); Mammini, Paul V. (Inventor)

2005-01-01

Embodiments of the present invention are directed to a simple apparatus and a convenient and accurate method of mounting the components to form an off-axis reflective optical apparatus such as a collimator. In one embodiment, an off-axis reflective optical apparatus comprises a mounting block having a ferrule holder support surface and an off-axis reflector support surface which is generally perpendicular to the ferrule holder support surface. An optical reflector is mounted on the off-axis reflector support surface and has a reflected beam centerline. The optical reflector has a conic reflective surface and a conic center. A ferrule holder is mounted on the ferrule holder support surface. The ferrule holder provides a ferrule for coupling to an optical fiber and orienting a fiber tip of the optical fiber along a fiber axis toward the optical reflector. The fiber axis is nonparallel to the reflected beam centerline. Prior to mounting the optical reflector to the off-axis reflector support surface and prior to mounting the ferrule holder to the ferrule holder support surface, the optical reflector is movable on the off-axis reflector surface and the ferrule holder is movable on the ferrule holder support surface to align the conic center of the optical reflector with respect to the fiber tip of the optical fiber, and the apparatus has at least one of the following features: (1) the optical reflector is movable on the off-axis reflector support surface to adjust a focus of the fiber tip with respect to the optical reflector, and (2) the ferrule holder is movable on the ferrule holder support surface to adjust the focus of the fiber tip with respect to the optical reflector.

Adaptive fiber optics collimator based on flexible hinges.

PubMed

Zhi, Dong; Ma, Yanxing; Ma, Pengfei; Si, Lei; Wang, Xiaolin; Zhou, Pu

2014-08-20

In this manuscript, we present a new design for an adaptive fiber optics collimator (AFOC) based on flexible hinges by using piezoelectric stacks actuators for X-Y displacement. Different from traditional AFOC, the new structure is based on flexible hinges to drive the fiber end cap instead of naked fiber. We fabricated a real AFOC based on flexible hinges, and the end cap's deviation and resonance frequency of the device were measured. Experimental results show that this new AFOC can provide fast control of tip-tilt deviation of the laser beam emitting from the end cap. As a result, the fiber end cap can support much higher power than naked fiber, which makes the new structure ideal for tip-tilt controlling in a high-power fiber laser system.

Infrared techniques for detecting carbonization at onset of device failure

NASA Astrophysics Data System (ADS)

Farr, Norman; Sinofsky, Edward L.

1997-05-01

We describe the design, and development of an infrared detection system which detects the onset of carbonization of fluoropolymers in the presence of up to 60 watts of 1.06 micrometer laser energy. This system is used to shut down a therapeutic laser system before significant damage is done to a laser delivery device and patient. Black body radiation emitting from the diffusion tip is transmitted, backwards, through the same optical fiber as the therapeutic wavelength. Using a high power 1.06 micrometer laser mirror at 45 degrees, most of the 1.06 micrometer light is reflected while the black body radiation is passed to a holographic notch filter which further filters the signal. Still more filtering was needed before the 1.1 to 2 micrometer signal could be detected within the presence the therapeutic light using an extended indium gallium arsenide photodetector. There was still a significant detected offset which increased with laser power which necessitated a means to automatically null the offset for different laser power settings. The system is designed to be used with any unmodified laser system. It interfaces directly to or in series with most common external safety interlocks and can be used with various diffusing tips, probes or bare fibers.

Thulium fiber laser ablation of kidney stones using a 50-μm-core silica optical fiber

NASA Astrophysics Data System (ADS)

Blackmon, Richard L.; Hutchens, Thomas C.; Hardy, Luke A.; Wilson, Christopher R.; Irby, Pierce B.; Fried, Nathaniel M.

2015-01-01

Our laboratory is currently studying the experimental thulium fiber laser (TFL) as a potential alternative laser lithotripter to the gold standard, clinical Holmium:YAG laser. We have previously demonstrated the efficient coupling of TFL energy into fibers as small as 100-μm-core-diameter without damage to the proximal end. Although smaller fibers have a greater tendency to degrade at the distal tip during lithotripsy, fiber diameters (≤200 μm) have been shown to increase the saline irrigation rates through the working channel of a flexible ureteroscope, to maximize the ureteroscope deflection, and to reduce the stone retropulsion during laser lithotripsy. In this study, a 50-μm-core-diameter, 85-μm-outer-diameter, low-OH silica fiber is characterized for TFL ablation of human calcium oxalate monohydrate urinary stones, ex vivo. The 50-μm-core fiber consumes approximately 30 times less cross-sectional area inside the single working channel of a ureteroscope than the standard 270-μm-core fiber currently used in the clinic. The ureteroscope working channel flow rate, including the 50-μm fiber, decreased by only 10% with no impairment of ureteroscope deflection. The fiber delivered up to 15.4±5.9 W under extreme bending (5-mm-radius) conditions. The stone ablation rate measured 70±22 μg/s for 35-mJ-pulse-energy, 500-μs-pulse-duration, and 50-Hz-pulse-rate. Stone retropulsion and fiber burnback averaged 201±336 and 3000±2600 μm, respectively, after 2 min. With further development, thulium fiber laser lithotripsy using ultra-small, 50-μm-core fibers may introduce new integration and miniaturization possibilities and potentially provide an alternative to conventional Holmium:YAG laser lithotripsy using larger fibers.

Rotating fiber array molecular driver and molecular momentum transfer device constructed therewith

DOEpatents

Milleron, Norman

1983-01-01

A rotating fiber array molecular driver is disclosed which includes a magnetically suspended and rotated central hub to which is attached a plurality of elongated fibers extending radially therefrom. The hub is rotated so as to straighten and axially extend the fibers and to provide the fibers with a tip speed which exceeds the average molecular velocity of fluid molecules entering between the fibers. Molecules colliding with the sides of the rotating fibers are accelerated to the tip speed of the fiber and given a momentum having a directional orientation within a relatively narrow distribution angle at a point radially outward of the hub, which is centered and peaks at the normal to the fiber sides in the direction of fiber rotation. The rotating fiber array may be used with other like fiber arrays or with other stationary structures to form molecular momentum transfer devices such as vacuum pumps, molecular separators, molecular coaters, or molecular reactors.

Confined detection volume of fluorescence correlation spectroscopy by bare fiber probes.

PubMed

Lu, Guowei; Lei, Franck H; Angiboust, Jean-François; Manfait, Michel

2010-04-01

A fiber-tip-based near-field fluorescence correlation spectroscopy (FCS) has been developed for confining the detection volume to sub-diffraction-limited dimensions. This near-field FCS is based on near-field illumination by coupling a scanning near-field optical microscope (SNOM) to a conventional confocal FCS. Single-molecule FCS analysis at 100 nM Rhodamine 6G has been achieved by using bare chemically etched, tapered fiber tips. The detection volume under control of the SNOM system has been reduced over one order of magnitude compared to that of the conventional confocal FCS. Related factors influencing the near-field FCS performance are investigated and discussed in detail. In this proof-of-principle study, the preliminary experimental results suggest that the fiber-tip-based near-field FCS might be a good alternative to realize localized analysis at the single-molecule level.

Etching of semiconductors and metals by the photonic jet with shaped optical fiber tips

NASA Astrophysics Data System (ADS)

Pierron, Robin; Lecler, Sylvain; Zelgowski, Julien; Pfeiffer, Pierre; Mermet, Frédéric; Fontaine, Joël

2017-10-01

The etching of semiconductors and metals by a photonic jet (PJ) generated with a shaped optical fiber tip is studied. Etched marks with a diameter of 1 μm have been realized on silicon, stainless steel and titanium with a 35 kHz pulsed laser, emitting 100 ns pulses at 1064 nm. The selection criteria of the fiber and its tip are discussed. We show that a 100/140 silica fiber is a good compromise which takes into account the injection, the working distance and the energy coupled in the higher-order modes. The energy balance is performed on the basis of the known ablation threshold of the material. Finally, the dependence between the etching depth and the number of pulses is studied. Saturation is observed probably due to a redeposition of the etched material, showing that a higher pulse energy is required for deeper etchings.

Correlation of Retinal Nerve Fiber Layer Thickness and Visual Fields in Glaucoma: A broken stick model

PubMed Central

Alasil, Tarek; Wang, Kaidi; Yu, Fei; Field, Matthew G.; Lee, Hang; Baniasadi, Neda; de Boer, Johannes F.; Coleman, Anne L.; Chen, Teresa C.

2015-01-01

Purpose To determine the retinal nerve fiber layer (RNFL) thickness at which visual field (VF) damage becomes detectable and associated with structural loss. Design Retrospective cross-sectional study. Methods Eighty seven healthy and 108 glaucoma subjects (one eye per subject) were recruited from an academic institution. All patients had VF examinations (Swedish Interactive Threshold Algorithm 24-2 test of the Humphrey visual field analyzer 750i; Carl Zeiss Meditec, Dublin, CA) and spectral domain optical coherence tomography RNFL scans (Spectralis, Heidelberg Engineering, Heidelberg, Germany). Comparison of RNFL thicknesses values with VF threshold values showed a plateau of VF threshold values at high RNFL thickness values and then a sharp decrease at lower RNFL thickness values. A broken stick statistical analysis was utilized to estimate the tipping point at which RNFL thickness values are associated with VF defects. The slope for the association between structure and function was computed for data above and below the tipping point. Results The mean RNFL thickness value that was associated with initial VF loss was 89 μm. The superior RNFL thickness value that was associated with initial corresponding inferior VF loss was 100 μm. The inferior RNFL thickness value that was associated with initial corresponding superior VF loss was 73 μm. The differences between all the slopes above and below the aforementioned tipping points were statistically significant (p<0.001). Conclusions In open angle glaucoma, substantial RNFL thinning or structural loss appears to be necessary before functional visual field defects become detectable. PMID:24487047

Radial-firing optical fiber tip containing conical-shaped air-pocket for biomedical applications.

PubMed

Lee, Seung Ho; Ryu, Yong-Tak; Son, Dong Hoon; Jeong, Seongmook; Kim, Youngwoong; Ju, Seongmin; Kim, Bok Hyeon; Han, Won-Taek

2015-08-10

We report a novel radial-firing optical fiber tip containing a conical-shaped air-pocket fabricated by deforming a hollow optical fiber using electric arc-discharge process. The hollow optical fiber was fusion spliced with a conventional optical fiber, simultaneously deforming into the intagliated conical-shaped region along the longitudinal fiber-axis of the fiber due to the gradual collapse of the cavity of the hollow optical fiber. Then the distal-end of the hollow optical fiber was sealed by the additional arc-discharge in order to obstruct the inflow of an external bio-substance or liquid to the inner air surface during the surgical operations, resulting in the formation of encased air-pocket in the silica glass fiber. Due to the total internal reflection of the laser beam at the conical-shaped air surface, the laser beam (λ = 632.8 nm) was deflected to the circumferential direction up to 87 degree with respect to the fiber-axis.

Fabrication, characterization, and potential application of carbon fiber cone nanometer-size electrodes.

PubMed

Zhang, X; Zhang, W; Zhou, X; Ogorevc, B

1996-10-01

A novel method has been developed for the fabrication of carbon fiber cone nanometer-size ultramicroelectrodes (nanoelectrodes) with overall tip dimensions as small as 50 nm in diameter. In this method, carbon fibers were initially etched by an argon ion beam thinner. Afterward, a single etched carbon fiber was inserted into a glass capillary, which was then sealed by heating the glass/fiber interface in a vacuum; thus, no epoxy resin is involved. The success rate of our fabrication route for the electrodes with overall tip diameters of up to 500 nm was about 80%; for those with tip diameters of up to 100 nm, it was about 50%. The fabricated carbon fiber cone nanoelectrodes (CFCNEs) were inspected by optical and scanning electron microscopy. Their electrochemical behavior was examined by cyclic and linear sweep voltammetric measurements of ferricyanide and ferrocene ions in aqueous and nonaqueous media. The potential analytical applicability of the CFCNEs was tested by differential pulse voltammetric measurements of two well-known neurotransmitters, dopamine (DA) and 5-hydroxytryptamine (5-HT), and the results achieved were highly satisfactory. The calibration plots obtained were linear over the ranges from 5.0 × 10(-7) to 1.0 × 10(-4) and from 2.0 × 10(-6) to 1.0 × 10(-4) mol/L, with limits of detection of 1.0 × 10(-7) and 5.0 × 10(-7) mol/L for DA and 5-HT, respectively. Some advantages and improvements of the proposed CFCNE fabrication method, especially with respect to smoothness of the fiber (electrode) surface, strength, and control over the fiber tip dimensions, are also discussed.

Bubble velocity, diameter, and void fraction measurements in a multiphase flow using fiber optic reflectometer

NASA Astrophysics Data System (ADS)

Lim, Ho-Joon; Chang, Kuang-An; Su, Chin B.; Chen, Chi-Yueh

2008-12-01

A fiber optic reflectometer (FOR) technique featuring a single fiber probe is investigated for its feasibility of measuring the bubble velocity, diameter, and void fraction in a multiphase flow. The method is based on the interference of the scattered signal from the bubble surface with the Fresnel reflection signal from the tip of the optical fiber. Void fraction is obtained with a high accuracy if an appropriate correction is applied to compensate the underestimated measurement value. Velocity information is accurately obtained from the reflected signals before the fiber tip touches the bubble surface so that several factors affecting the traditional dual-tip probes such as blinding, crawling, and drifting effects due to the interaction between the probe and bubbles can be prevented. The coherent signals reflected from both the front and rear ends of a bubble can provide velocity information. Deceleration of rising bubbles and particles due to the presence of the fiber probe is observed when they are very close to the fiber tip. With the residence time obtained, the bubble chord length can be determined by analyzing the coherent signal for velocity determination before the deceleration starts. The bubble diameters are directly obtained from analyzing the signals of the bubbles that contain velocity information. The chord lengths of these bubbles measured by FOR represent the bubble diameters when the bubble shape is spherical or represent the minor axes when the bubble shape is ellipsoidal. The velocity and size of bubbles obtained from the FOR measurements are compared with those obtained simultaneously using a high speed camera.

Fiber-type susceptibility to eccentric contraction-induced damage of hindlimb-unloaded rat AL muscles

NASA Technical Reports Server (NTRS)

Vijayan, K.; Thompson, J. L.; Norenberg, K. M.; Fitts, R. H.; Riley, D. A.

2001-01-01

Slow oxidative (SO) fibers of the adductor longus (AL) were predominantly damaged during voluntary reloading of hindlimb unloaded (HU) rats and appeared explainable by preferential SO fiber recruitment. The present study assessed damage after eliminating the variable of voluntary recruitment by tetanically activating all fibers in situ through the motor nerve while applying eccentric (lengthening) or isometric contractions. Muscles were aldehyde fixed and resin embedded, and semithin sections were cut. Sarcomere lesions were quantified in toluidine blue-stained sections. Fibers were typed in serial sections immunostained with antifast myosin and antitotal myosin (which highlights slow fibers). Both isometric and eccentric paradigms caused fatigue. Lesions occurred only in eccentrically contracted control and HU muscles. Fatigue did not cause lesions. HU increased damage because lesioned- fiber percentages within fiber types and lesion sizes were greater than control. Fast oxidative glycolytic (FOG) fibers were predominantly damaged. In no case did damaged SO fibers predominate. Thus, when FOG, SO, and hybrid fibers are actively lengthened in chronically unloaded muscle, FOG fibers are intrinsically more susceptible to damage than SO fibers. Damaged hybrid-fiber proportions ranged between these extremes.

Light distribution properties in spinal cord for optogenetic stimulation (Conference Presentation)

NASA Astrophysics Data System (ADS)

GÄ secka, Alicja; Bahdine, Mohamed; Lapointe, Nicolas; Rioux, Veronique; Perez-Sanchez, Jimena; Bonin, Robert P.; De Koninck, Yves; Côté, Daniel

2016-03-01

Optogenetics is currently one of the most popular technique in neuroscience. It enables cell-selective and temporally-precise control of neuronal activity. Good spatial control of the stimulated area and minimized tissue damage requires a specific knowledge about light scattering properties. Light propagation in cell cultures and brain tissue is relatively well documented and allows for a precise and reliable delivery of light to the neurons. In spinal cord, light must pass through highly organized white matter before reaching cell bodies present in grey matter, this heterogenous structure makes it difficult to predict the propagation pattern. In this work we investigate the light distribution properties through mouse and monkey spinal cord. The light propagation depends on a fibers orientation, leading to less deep penetration profile in the direction perpendicular to the fibers and lower attenuation in the direction parallel to the fibers. Additionally, the use of different illumination wavelengths results in variations of the attenuation coefficient. Next, we use Monte-Carlo simulation to study light transport. The model gives a full 3-D simulation of light distribution in spinal cord and takes into account different scattering properties related to the fibers orientation. These studies are important to estimate the minimum optical irradiance required at the fiber tip to effectively excite the optogenetic proteins in a desired region of spinal cord.

Biologically inspired autonomous structural materials with controlled toughening and healing

NASA Astrophysics Data System (ADS)

Garcia, Michael E.; Sodano, Henry A.

2010-04-01

The field of structural health monitoring (SHM) has made significant contributions in the field of prognosis and damage detection in the past decade. The advantageous use of this technology has not been integrated into operational structures to prevent damage from propagating or to heal injured regions under real time loading conditions. Rather, current systems relay this information to a central processor or human operator, who then determines a course of action such as altering the mission or scheduling repair maintenance. Biological systems exhibit advanced sensory and healing traits that can be applied to the design of material systems. For instance, bone is the major structural component in vertebrates; however, unlike modern structural materials, bone has many properties that make it effective for arresting the propagation of cracks and subsequent healing of the fractured area. The foremost goal for the development of future adaptive structures is to mimic biological systems, similar to bone, such that the material system can detect damage and deploy defensive traits to impede damage from propagating, thus preventing catastrophic failure while in operation. After sensing and stalling the propagation of damage, the structure must then be repaired autonomously using self healing mechanisms motivated by biological systems. Here a novel autonomous system is developed using shape memory polymers (SMPs), that employs an optical fiber network as both a damage detection sensor and a network to deliver stimulus to the damage site initiating adaptation and healing. In the presence of damage the fiber optic fractures allowing a high power laser diode to deposit a controlled level of thermal energy at the fractured sight locally reducing the modulus and blunting the crack tip, which significantly slows the crack growth rate. By applying a pre-induced strain field and utilizing the shape memory recovery effect, thermal energy can be deployed to close the crack and return the system to its original operating state. The entire system will effectively detect, self toughen, and subsequently heal damage as biological materials such as bone does.

Low-coherence interferometric tip-clearance probe

NASA Astrophysics Data System (ADS)

Kempe, Andreas; Schlamp, Stefan; Rösgen, Thomas; Haffner, Ken

2003-08-01

We propose an all-fiber, self-calibrating, economical probe that is capable of near-real-time, single-port, simultaneous blade-to-blade tip-clearance measurements with submillimeter accuracy (typically <100 μm, absolute) in the first stages of a gas turbine. Our probe relies on the interference between backreflected light from the blade tips during the 1-μs blade passage time and a frequency-shifted reference with variable time delay, making use of a low-coherence light source. A single optical fiber of arbitrary length connects the self-contained optics and electronics to the turbine.

Electron Microscopy of Dural and Arachnoid Disruptions After Subarachnoid Block.

PubMed

Reina, Miguel Angel; Puigdellívol-Sánchez, Anna; Gatt, Stephen P; De Andrés, José; Prats-Galino, Alberto; van Zundert, André

It has been customary to attribute postdural puncture headache (PDPH) incidence and severity to size and nature of the dural hole produced during major neuraxial blockade or diagnostic dural puncture. Needle orientation in relation to the direction of dural fibers was thought to be of importance because of the propensity for horizontal bevel placement to cause cutting rather than splitting of the dural fibers. In vitro punctures of stringently quality-controlled human dural sac specimens were obtained with 27-gauge (27G) Whitacre needle (n = 33), with 29G Quincke used parallel to the spinal axis (n = 30), and with 29G Quincke in perpendicular approach (n = 40). The samples were studied with a scanning electron microscope, and the perimeter, appearance, and area (%) of the lesion were calculated. When using small 27G to 29G needles, neither needle tip characteristics nor needle orientation had a substantial bearing on the damage to dural fibers in the dural lesion. Of ultimate importance was the characteristic and size of the hole in the arachnoid. Arachnoid layer lesions produced by different types of spinal needles were not markedly different. Accepted theories of the etiology of PDPH need to be revised. This article marks the first time that arachnoid layer damage has been quantified. Dural fibers tend to have sufficient "memory" to close back the hole created by a spinal needle, whereas arachnoid has diminished capacity to do so. The pathogenesis of PDPH and its resolution algorithm are a far more complex process that involves many more "stages" of development than hitherto imagined.

Predicting infestation levels of the nantucket pine tip moth (Lepidoptera: Tortricidae) using pheromone traps

Treesearch

Christopher Asaro; C. Wayne Berisford

2001-01-01

There is considerable interest in using pheromone trap catches of the Nantucket pine tip moth, Rhyacionia frustrana (Conistock), to estimate or predict population density and damage. At six sites in the Georgia Piedmont, adult tip moths were monitored through one or more years using pheromone traps while population density and damage for each tip...

Micro particle launcher/cleaner based on optical trapping technology.

PubMed

Liu, Zhihai; Liang, Peibo; Zhang, Yu; Zhang, Yaxun; Zhao, Enming; Yang, Jun; Yuan, Libo

2015-04-06

Efficient and controllable launching function of an optical tweezers is a challenging task. We present and demonstrate a novel single fiber optical tweezers which can trap and launch (clean) a target polystyrene (PS) microsphere (diameter~10μm) with independent control by using two wavelengths beams: 980nm and 1480nm. We employ 980nm laser beam to trap the target PS microsphere by molding the fiber tip into a special tapered-shape; and we employ 1480nm laser beam to launch the trapped PS microsphere with a certain velocity by using the thermophoresis force generated from the thermal effect due to the high absorption of the 1480nm laser beams in water. When the launching force is smaller than the trapping force, the PS microsphere will be trapped near the fiber tip, and the launching force will blow away other PS microspheres in the workspace realizing the cleaning function; When the launching force is larger than the trapping force, the trapped PS microsphere will be launched away from the fiber tip with a certain velocity and towards a certain direction, realizing the launching function. The launching velocity, acceleration and the distance can be measured by detecting the interference signals generated from the PS microsphere surface and the fiber tip end-face. This PS microsphere launching and cleaning functions expanded new features of single fiber optical tweezers, providing for the possibility of more practical applications in the micro manipulation research fields.

High temperature heat source generation with a very low power level quasi-cw(continuous wave) semiconductor laser for medical use

NASA Astrophysics Data System (ADS)

Fujimoto, Takahiro; Imai, Yusuke; Tei, Kazuyoku; Fujioka, Tomoo; Yamaguchi, Shigeru

2013-03-01

In most of medical and dental laser treatments, high power pulsed laser have been used as desirable light sources employing with an optical fiber delivery system. The treatment process involves high temperature thermal effect associated with direct laser absorption of the materials such as hard and soft tissues, tooth, bones and so on. Such treatments sometimes face technical difficulties suffering from their optical absorption properties. We investigate a new technology to create high temperature heat source on the tip surface of the glass fiber proposed for the medical surgery applications. Using a low power level (4 6W) semiconductor laser at a wavelength of 980nm, a laser coupled fiber tip was pre-processed to contain certain amount of TiO2 powder with a depth of 400μm from the tip surface so that the irradiated low laser energy could be perfectly absorbed to be transferred to thermal energy. Thus the laser treatment can be performed without suffering from any optical characteristic of the material. Semiconductor laser was operated quasi-CW mode pulse time duration of 180ms and more than 95% of the laser energy was converted to thermal energy in the fiber tip. by Based on twocolor thermometry by using a gated optical multichannel analyzer with 0.25m spectrometer in visible wavelength region, the temperature of the fiber tip was analyzed. The temperature of the heat source was measured to be approximately 3000K. Demonstration of laser processing employing this system was successfully carried out drilling through holes in ceramic materials simulating bone surgery.

Multimode fiber tip Fabry-Perot cavity for highly sensitive pressure measurement.

PubMed

Chen, W P; Wang, D N; Xu, Ben; Zhao, C L; Chen, H F

2017-03-23

We demonstrate an optical Fabry-Perot interferometer fiber tip sensor based on an etched end of multimode fiber filled with ultraviolet adhesive. The fiber device is miniature (with diameter of less than 60 μm), robust and low cost, in a convenient reflection mode of operation, and has a very high gas pressure sensitivity of -40.94 nm/MPa, a large temperature sensitivity of 213 pm/°C within the range from 55 to 85 °C, and a relatively low temperature cross-sensitivity of 5.2 kPa/°C. This device has a high potential in monitoring environment of high pressure.

Fiber sensor assisted in-vivo needle guidance for minimally invasive procedures (Conference Presentation)

NASA Astrophysics Data System (ADS)

Baghdadchi, Saharnaz; Chao, Cherng; Esener, Sadik; Mattrey, Robert F.; Eghtedari, Mohammad A.

2017-02-01

Image-guided procedures are performed frequently by radiologists to insert a catheter within a target vessel or lumen or to perform biopsy of a lesion. For instance, an interventional radiologist uses fluoroscopy during percutaneous biliary drainage procedure (a procedure during which a catheter is inserted through the skin to drain the bile from liver) to identify the location of the needle tip within liver parenchyma, hepatic blood vessel or bile duct. However, the identification of the target organ under fluoroscopy exposes the patient to x-ray irradiation, which may be significant if the time of procedure is prolonged. We have designed a fiber core needle system that may help the radiologist identify the location of the needle tip in real time without exposing the patient to x-ray. Our needle system transmits a low power modulated light into the tissue through a fiber cable embedded in the needle and detects the backscattered light using another fiber inside the needle. We were able to successfully distinguish the location of our prototype needle tip inside a cow liver phantom to identify if the needle tip was within liver parenchyma, liver vessels, or in the bile duct based on the recorded backscattered light.

Fiber optic chemical sensors: The evolution of high- density fiber-optic DNA microarrays

NASA Astrophysics Data System (ADS)

Ferguson, Jane A.

2001-06-01

Sensors were developed for multianalyte monitoring, fermentation monitoring, lactate analysis, remote oxygen detection for use in bioremediation monitoring and in a fuel spill clean-up project, heavy metal analysis, and high density DNA microarrays. The major focus of this thesis involved creating and improving high-density DNA gene arrays. Fiber optic sensors are created using fluorescent indicators, polymeric supports, and optical fiber substrates. The fluorescent indicator is entrapped in a polymer layer and attached to the tip of the optical fiber. The tip of the fiber bearing the sensing layer (the distal end) is placed in the sample of interest while the other end of the fiber (the proximal end) is connected to an analysis system. Any length of fiber can be used without compromising the integrity or sensitivity of the system. A fiber optic oxygen sensor was designed incorporating an oxygen sensitive fluorescent dye and a gas permeable polymer attached to an optical fiber. The construction simplicity and ruggedness of the sensor enabled its deployment for in situ chemical oxidation and bioremediation studies. Optical fibers were also used as the substrate to detect biomolecules in solution. To monitor bioprocesses, the production of the analyte of interest must be coupled with a species that is optically measurable. For example, oxygen is consumed in many metabolic functions. The fiber optic oxygen sensor is equipped with an additional sensing layer. Upon contact with a specific biochemical in the sample, a reaction occurs in the additional sensing layer that either consumes or produces oxygen. This dual layer system was used to monitor the presence of lactate, an important metabolite for clinical and bioprocess analysis. In many biological and environmental systems, the generation of one species occurs coincidentally with the generation or consumption of another species. A multianalyte sensor was prepared that can monitor the simultaneous activity of pH, CO2 and O2. This sensor is useful for monitoring bioprocesses such as (beer) fermentation and for clinical situations such as blood gas analysis. DNA sensors were created by attaching short single strands of DNA (probes) to the fiber tip. A matching single strand (target) forms a strong interacting pair with the probe upon contact. The target strands in a sample are labeled with a fluorescent dye. When a probe-target pair is formed and excitation light is sent down the fiber, the fiber bearing the pair emits light that is captured and detected. A high density DNA array was created by isolating thousands of discrete DNA sensors on the tip of an imaging optical fiber. This array was made possible by the formation of microwells on the imaging fiber tip. Microspheres functionalized with DNA were placed in the wells of the fiber and each microsphere was independently and simultaneously monitored. (Abstract shortened by UMI.)

Nanomechanics of electrospun phospholipid fiber

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

Mendes, Ana C., E-mail: anac@food.dtu.dk, E-mail: ioach@food.dtu.dk; Chronakis, Ioannis S., E-mail: anac@food.dtu.dk, E-mail: ioach@food.dtu.dk; Nikogeorgos, Nikolaos

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 modulusmore » of elasticity up to 24 h.« less

Transurethral illumination probe design for deep photoacoustic imaging of prostate

NASA Astrophysics Data System (ADS)

Ai, Min; Salcudean, Tim; Rohling, Robert; Abolmaesumi, Purang; Tang, Shuo

2018-02-01

Photoacoustic (PA) imaging with internal light illumination through optical fiber could enable imaging of internal organs at deep penetration. We have developed a transurethral probe with a multimode fiber inserted in a rigid cystoscope sheath for illuminating the prostate. At the distal end, the fiber tip is processed to diffuse light circumferentially over 2 cm length. A parabolic cylinder mirror then reflects the light to form a rectangular-shaped parallel beam which has at least 1 cm2 at the probe surface. The relatively large rectangular beam size can reduce the laser fluence rate on the urethral wall and thus reduce the potential of tissue damage. A 3 cm optical penetration in chicken tissue is achieved at a fluence rate around 7 mJ/cm2 . For further validation, a prostate phantom was built with similar optical properties of the human prostate. A 1.5 cm penetration depth is achieved in the prostate mimicking phantom at 10 mJ/cm2 fluence rate. PA imaging of prostate can potentially be carried out in the future by combining a transrectal ultrasound transducer and the transurethral illumination.

Detecting and Segregating Black Tip-Damaged Wheat Kernels Using Visible and Near Infrared Spectroscopy

USDA-ARS?s Scientific Manuscript database

Detection of individual wheat kernels with black tip symptom (BTS) and black tip damage (BTD) was demonstrated using near infrared reflectance spectroscopy (NIRS) and silicon light-emitting-diode (LED) based instruments. The two instruments tested, a single kernel near-infrared spectroscopy instrume...

Blade tip clearance measurement of the turbine engines based on a multi-mode fiber coupled laser ranging system

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

Guo, Haotian; Duan, Fajie; Wu, Guoxiu

2014-11-15

The blade tip clearance is a parameter of great importance to guarantee the efficiency and safety of the turbine engines. In this article, a laser ranging system designed for blade tip clearance measurement is presented. Multi-mode fiber is utilized for optical transmission to guarantee that enough optical power is received by the sensor probe. The model of the tiny sensor probe is presented. The error brought by the optical path difference of different modes of the fiber is estimated and the length of the fiber is limited to reduce this error. The measurement range in which the optical power receivedmore » by the probe remains essentially unchanged is analyzed. Calibration experiments and dynamic experiments are conducted. The results of the calibration experiments indicate that the resolution of the system is about 0.02 mm and the range of the system is about 9 mm.« less

Optical fiber nanoprobe preparation for near-field optical microscopy by chemical etching under surface tension and capillary action.

PubMed

Mondal, Samir K; Mitra, Anupam; Singh, Nahar; Sarkar, S N; Kapur, Pawan

2009-10-26

We propose a technique of chemical etching for fabrication of near perfect optical fiber nanoprobe (NNP). It uses photosensitive single mode optical fiber to etch in hydro fluoric (HF) acid solution. The difference in etching rate for cladding and photosensitive core in HF acid solution creates capillary ring along core-cladding boundary under a given condition. The capillary ring is filled with acid solution due to surface tension and capillary action. Finally it creates near perfect symmetric tip at the apex of the fiber as the height of the acid level in capillary ring decreases while width of the ring increases with continuous etching. Typical tip features are short taper length (approximately 4 microm), large cone angle (approximately 38 degrees ), and small probe tip dimension (<100 nm). A finite difference time domain (FDTD) analysis is also presented to compare near field optics of the NNP with conventional nanoprobe (CNP). The probe may be ideal for near field optical imaging and sensor applications.

The Effect of Delamination on Damage Path and Failure Load Prediction for Notched Composite Laminates

NASA Technical Reports Server (NTRS)

Satyanarayana, Arunkumar; Bogert, Philip B.; Chunchu, Prasad B.

2007-01-01

The influence of delamination on the progressing damage path and initial failure load in composite laminates is investigated. Results are presented from a numerical and an experimental study of center-notched tensile-loaded coupons. The numerical study includes two approaches. The first approach considers only intralaminar (fiber breakage and matrix cracking) damage modes in calculating the progression of the damage path. In the second approach, the model is extended to consider the effect of interlaminar (delamination) damage modes in addition to the intralaminar damage modes. The intralaminar damage is modeled using progressive damage analysis (PDA) methodology implemented with the VUMAT subroutine in the ABAQUS finite element code. The interlaminar damage mode has been simulated using cohesive elements in ABAQUS. In the experimental study, 2-3 specimens each of two different stacking sequences of center-notched laminates are tensile loaded. The numerical results from the two different modeling approaches are compared with each other and the experimentally observed results for both laminate types. The comparisons reveal that the second modeling approach, where the delamination damage mode is included together with the intralaminar damage modes, better simulates the experimentally observed damage modes and damage paths, which were characterized by splitting failures perpendicular to the notch tips in one or more layers. Additionally, the inclusion of the delamination mode resulted in a better prediction of the loads at which the failure took place, which were higher than those predicted by the first modeling approach which did not include delaminations.

Endovascular Catheter for Magnetic Navigation under MR Imaging Guidance: Evaluation of Safety in Vivo at 1.5T

PubMed Central

Hetts, S.W.; Saeed, M.; Martin, A.J.; Evans, L.; Bernhardt, A.F.; Malba, V.; Settecase, F.; Do, L.; Yee, E.J.; Losey, A.; Sincic, R.; Roy, S.; Arenson, R.L.; Wilson, M.W.

2013-01-01

BACKGROUND AND PURPOSE: Endovascular navigation under MR imaging guidance can be facilitated by a catheter with steerable microcoils on the tip. Not only do microcoils create visible artifacts allowing catheter tracking, but also they create a small magnetic moment permitting remote-controlled catheter tip deflection. A side product of catheter tip electrical currents, however, is the heat that might damage blood vessels. We sought to determine the upper boundary of electrical currents safely usable at 1.5T in a coil-tipped microcatheter system. MATERIALS AND METHODS: Alumina tubes with solenoid copper coils were attached to neurovascular microcatheters with heat shrink-wrap. Catheters were tested in carotid arteries of 8 pigs. The catheters were advanced under x-ray fluoroscopy and MR imaging. Currents from 0 mA to 700 mA were applied to test heating and potential vascular damage. Postmortem histologic analysis was the primary endpoint. RESULTS: Several heat-mitigation strategies demonstrated negligible vascular damage compared with control arteries. Coil currents ≤300 mA resulted in no damage (0/58 samples) compared with 9 (25%) of 36 samples for > 300-mA activations (P = .0001). Tip coil activation ≤1 minute and a proximal carotid guide catheter saline drip > 2 mL/minute also had a nonsignificantly lower likelihood of vascular damage. For catheter tip coil activations ≤300 mA for ≤1 minute in normal carotid flow, 0 of 43 samples had tissue damage. CONCLUSIONS: Activations of copper coils at the tip of microcatheters at low currents in 1.5T MR scanners can be achieved without significant damage to blood vessel walls in a controlled experimental setting. Further optimization of catheter design and procedure protocols is necessary for safe remote control magnetic catheter guidance. PMID:23846795

Design and fabrication of sub-wavelength annular apertures on fiber tip for femtosecond laser machining

NASA Astrophysics Data System (ADS)

Tung, Yen-Chun; Chung, Ming-Han; Sung, I.-Hui; Lee, Chih-Kung

2014-03-01

Adopting optical technique to pursue micromachining must make a compromise between the focal spot sizes the depth of focus. The focal spot size determines the minimum features can be fabricated. On the other hand, the depth of focus influences the ease of alignment in positioning the fabrication light beam. A typical approach to bypass the diffraction limit is to adopt the near-field approach, which has spot size in the range of the optical fiber tip. However, the depth of focus of the emitted light beam will be limited to tens of nanometers in most cases, which posts a difficult challenge to control the distance between the optical fiber tip and the sample to be machined optically. More specifically, problems remained in this machining approach, which include issues such as residue induced by laser ablation tends to deposit near the optical fiber tip and leads to loss of coupling efficiency. We proposed a method based on illuminating femtosecond laser through a sub-wavelength annular aperture on metallic film so as to produce Bessel light beam of sub-wavelength while maintaining large depth of focus first. To further advance the ease of use in one such system, producing sub-wavelength annular aperture on a single mode optical fiber head with sub-wavelength focusing ability is detailed. It is shown that this method can be applied in material machining with an emphasis to produce high aspect ratio structure. Simulations and experimental results are presented in this paper.

Molecular characteristics suggest an effector function of palisade endings in extraocular muscles.

PubMed

Konakci, Kadriye Zeynep; Streicher, Johannes; Hoetzenecker, Wolfram; Blumer, Michael Josef Franz; Lukas, Julius-Robert; Blumer, Roland

2005-01-01

To analyze palisade endings in cat extraocular muscles (EOMs) and to clarify whether these EOM-specific organs are sensory or motor. Twelve cats aged between 1 and 16 years were analyzed. Whole EOM tendons were immunostained using four different combinations of triple fluorescence labeling. Triple labeling included antibodies against choline acetyltransferase (ChAT), neurofilament, synaptophysin, and alpha-bungarotoxin. Preparations were examined by confocal laser scanning microscopy. ChAT-labeled EOMs were also analyzed by immunoelectron microscopy. Three-dimensional reconstructions were made of palisade endings. Palisade endings were found in the distal and proximal myotendinous regions of cat EOMs. These endings arose from thin nerve fibers coming from the muscle and extending into the tendon. There, the nerve fibers turned back 180 degrees to divide into terminal branches around the muscle fiber tips. Terminal branches established numerous contacts with the tendon attached to the muscle fiber tip and only a few contacts with the muscle fiber. Often, nerve fibers forming palisade endings on muscle fiber tips were observed to establish multiple motor contacts on muscle fibers outside palisade endings. Three-dimensional reconstructions depicted the complex morphology of the palisade endings. All nerve fibers supplying palisade endings stained positively for ChAT and neurofilament. All nerve terminals in palisade endings were ChAT and synaptophysin positive. Only neuromuscular contacts in palisade endings were positive for alpha-bungarotoxin, as well. This study provides evidence that palisade endings in cat EOMs have effector function. The findings may be of significance for strabismus surgery because palisade endings are also found in human EOMs.

Electric-Field Sensing with a Scanning Fiber-Coupled Quantum Dot

NASA Astrophysics Data System (ADS)

Cadeddu, D.; Munsch, M.; Rossi, N.; Gérard, J.-M.; Claudon, J.; Warburton, R. J.; Poggio, M.

2017-09-01

We demonstrate the application of a fiber-coupled quantum dot (QD) in a tip as a scanning probe for electric-field imaging. We map the out-of-plane component of the electric field induced by a pair of electrodes by the measurement of the quantum-confined Stark effect induced on a QD spectral line. Our results are in agreement with finite-element simulations of the experiment. Furthermore, we present results from analytic calculations and simulations which are relevant to any electric-field sensor embedded in a dielectric tip. In particular, we highlight the impact of the tip geometry on both the resolution and sensitivity.

Medical catheters thermally manipulated by fiber optic bundles

DOEpatents

Chastagner, Philippe

1992-01-01

A maneuverable medical catheter comprising a flexible tube having a functional tip. The catheter is connected to a control source. The functional tip of the catheter carries a plurality of temperature activated elements arranged in parallel and disposed about the functional tip and held in spaced relation at each end. These elements expand when they are heated. A plurality of fiber optic bundles, each bundle having a proximal end attached to the control source and a distal end attached to one of the elements carry light into the elements where the light is absorbed as heat. By varying the optic fiber that is carrying the light and the intensity of the light, the bending of the elements can be controlled and thus the catheter steered. In an alternate embodiment, the catheter carries a medical instrument for gathering a sample of tissue. The instrument may also be deployed and operated by thermal expansion and contraction of its moving parts.

Evaluation of degree of conversion and hardness of dental composites photo-activated with different light guide tips.

PubMed

Galvão, Marília Regalado; Caldas, Sergei Godeiro Fernandes Rabelo; Bagnato, Vanderlei Salvador; de Souza Rastelli, Alessandra Nara; de Andrade, Marcelo Ferrarezi

2013-01-01

The aim of this study was to evaluate the degree of conversion and hardness of different composite resins, photo-activated for 40 s with two different light guide tips, fiber optic and polymer. Five specimens were made for each group evaluated. The percentage of unreacted carbon double bonds (% C═C) was determined from the ratio of absorbance intensities of aliphatic C═C (peak at 1637 cm(-1)) against internal standard before and after curing of the specimen: aromatic C-C (peak at 1610 cm(-1)). The Vickers hardness measurements were performed in a universal testing machine. A 50 gf load was used and the indenter with a dwell time of 30 seconds. The degree of conversion and hardness mean values were analyzed separately by ANOVA and Tukey's test, with a significance level set at 5%. The mean values of degree of conversion for the polymer and fiber optic light guide tip were statistically different (P<.001). The hardness mean values were statistically different among the light guide tips (P<.001), but also there was difference between top and bottom surfaces (P<.001). The results showed that the resins photo-activated with the fiber optic light guide tip promoted higher values for degree of conversion and hardness.

Evaluation of degree of conversion and hardness of dental composites photo-activated with different light guide tips

PubMed Central

Galvão, Marília Regalado; Caldas, Sergei Godeiro Fernandes Rabelo; Bagnato, Vanderlei Salvador; de Souza Rastelli, Alessandra Nara; de Andrade, Marcelo Ferrarezi

2013-01-01

Objective: The aim of this study was to evaluate the degree of conversion and hardness of different composite resins, photo-activated for 40 s with two different light guide tips, fiber optic and polymer. Methods: Five specimens were made for each group evaluated. The percentage of unreacted carbon double bonds (% C═C) was determined from the ratio of absorbance intensities of aliphatic C═C (peak at 1637 cm−1) against internal standard before and after curing of the specimen: aromatic C-C (peak at 1610 cm−1). The Vickers hardness measurements were performed in a universal testing machine. A 50 gf load was used and the indenter with a dwell time of 30 seconds. The degree of conversion and hardness mean values were analyzed separately by ANOVA and Tukey’s test, with a significance level set at 5%. Results: The mean values of degree of conversion for the polymer and fiber optic light guide tip were statistically different (P<.001). The hardness mean values were statistically different among the light guide tips (P<.001), but also there was difference between top and bottom surfaces (P<.001). Conclusions: The results showed that the resins photo-activated with the fiber optic light guide tip promoted higher values for degree of conversion and hardness. PMID:23407620

Experimental removal of subgingival calculus with the Er:YAG laser

NASA Astrophysics Data System (ADS)

Keller, Ulrich; Hibst, Raimund

1996-01-01

The purpose of this study was to evaluate the effects of the Er:YAG laser removal of subgingival calculi in periodontal treatment and to describe laser-induced cementum surface alterations. Freshly extracted human teeth with adherent plaques and mineralized calculi were laser treated using modified quartz fiber tips in direct contact to the root surface. For the fiber tip tested, the ablation threshold was 6.5 mJ. An effective removal of calculi was possible with 50 mJ resp. 150 mJ for a triple fiber. For the latter, a mass loss with a mean of about 5.1. mg/min was achieved. Histologic examinations of the cementum surface showed smoothed appearance alternately with rough depressions of the fiber tips, which can be discussed as a good precondition for periodontal tissue regeneration. Maximum temperature increase of 1.4 K was reached in the pulp, if an additional water irrigation was applied to the root surface. From these results it can be concluded that with the Er:YAG laser an effective removal of subgingival calculi can be performed without thermal risk for the pulp.

Reconfiguration of the multiwavelength operation of optical fiber ring lasers by the modifiable intra-cavity induced losses of an in-fiber tip probe modal Michelson interferometer

NASA Astrophysics Data System (ADS)

Salceda-Delgado, G.; Martinez-Rios, A.; Sierra-Hernandez, J. M.; Rodríguez-Carreón, V. C.; Toral-Acosta, D.; Selvas-Aguilar, R.; Álvarez-Tamayo, R. I.; Castillo-Guzman, A. A.; Rojas-Laguna, R.

2018-03-01

A straightforward and versatile method for switching from single to different multiwavelength laser emission in ring cavity fiber lasers is proposed and demonstrated experimentally. The method is based on using the changeable interference pattern from an optical fiber modal Michelson interferometer as a wavelength selective filter into the ring cavity laser. The interferometer is constructed using a bi-conical tapered fiber and a single-mode fiber segment, with these being spliced together to form an optical fiber tip probe. When the length of the single-mode fiber piece is modified, the phase difference between the interfering modes of the interferometer causes a change in the interferometer free spectral range. As a consequence, the laser intra-cavity losses lead to gain competition, which allows us to adjust the number of simultaneously generated laser lines. A multiwavelength reconfiguration of the laser from one up to a maximum of eight emission lines was obtained, with a maximum SNR of around 47 dBm.

Experimental demonstration of using divergence cost-function in SPGD algorithm for coherent beam combining with tip/tilt control.

PubMed

Geng, Chao; Luo, Wen; Tan, Yi; Liu, Hongmei; Mu, Jinbo; Li, Xinyang

2013-10-21

A novel approach of tip/tilt control by using divergence cost function in stochastic parallel gradient descent (SPGD) algorithm for coherent beam combining (CBC) is proposed and demonstrated experimentally in a seven-channel 2-W fiber amplifier array with both phase-locking and tip/tilt control, for the first time to our best knowledge. Compared with the conventional power-in-the-bucket (PIB) cost function for SPGD optimization, the tip/tilt control using divergence cost function ensures wider correction range, automatic switching control of program, and freedom of camera's intensity-saturation. Homemade piezoelectric-ring phase-modulator (PZT PM) and adaptive fiber-optics collimator (AFOC) are developed to correct piston- and tip/tilt-type aberrations, respectively. The PIB cost function is employed for phase-locking via maximization of SPGD optimization, while the divergence cost function is used for tip/tilt control via minimization. An average of 432-μrad of divergence metrics in open loop has decreased to 89-μrad when tip/tilt control implemented. In CBC, the power in the full width at half maximum (FWHM) of the main lobe increases by 32 times, and the phase residual error is less than λ/15.

Intranasal approach for manipulating the depressor septi nasi.

PubMed

Oh, Sang-Ha; Choi, Sangmun; Kim, Dong Woon; Jeong, Jae Yong

2012-03-01

A hyperactivated depressor septi nasi is an important factor contributing to nasal tip drooping. Although many studies have examined this, its treatment remains controversial. This study presents a surgical intervention based on an anatomic study.Ten fresh cadavers with large noses were used for the anatomic study. Between April 2008 and September 2010, 20 patients underwent surgical intervention for hyperactivated depressor septi nasi.In all of the cadaver dissections, the depressor septi nasi was present, although it was difficult to identify the muscle clearly in 6 of the cadavers. We found that the depressor septi nasi in the other 4 cadavers consisted of 3 fascicles. The medial fascicles were divided into superficial and deep fibers. Both the deep and superficial fibers were inserted into the dermocartilaginous ligament in the nearby nasal tip. After the superficial fibers were interdigitated with the orbicularis oris, they originated from the alveolar bone. The deep fibers originated at the anterior nasal spine. The intermediate fascicles inserted to the footplates of the medial crus and caudal septum. After interdigitating with the medial fascicles and orbicularis oris, they also originated from the alveolar bone. The drooping nasal tips were improved in all cases using an intranasal approach to manipulate the depressor septi nasi. No specific complication was seen. Surgical intervention of a hyperactivated depressor septi nasi using an intranasal approach was a useful method for correcting a drooping nasal tip.

Cohesive Laws for Analyzing Through-Crack Propagation in Cross Ply Laminates

NASA Technical Reports Server (NTRS)

Bergan, Andrew C.; Davila, Carlos G.

2015-01-01

The laminate cohesive approach (LCA) is a methodology for the experimental characterization of cohesive through-the-thickness damage propagation in fiber-reinforced polymer matrix composites. LCA has several advantages over other existing approaches for cohesive law characterization, including: visual measurements of crack length are not required, structural effects are accounted for, and LCA can be applied when the specimen is too small to achieve steady-state fracture. In this work, the applicability of this method is investigated for two material systems: IM7/8552, a conventional prepreg, and AS4/VRM34, a non-crimp fabric cured using an out-of-autoclave process. The compact tension specimen configuration is used to propagate stable Mode I damage. Trilinear cohesive laws are characterized using the fracture toughness and the notch tip opening displacement. Test results are compared for the IM7/8552 specimens with notches machined by waterjet and by wire slurry saw. It is shown that the test results are nearly identical for both notch tip preparations methods, indicating that significant specimen preparation time and cost savings can be realized by using the waterjet to notch the specimen instead of the wire slurry saw. The accuracy of the cohesive laws characterized herein are assessed by reproducing the structural response of the test specimens using computational methods. The applicability of the characterization procedure for inferring lamina fracture toughness is also discussed.

Applications of fiber-optics-based nanosensors to drug discovery.

PubMed

Vo-Dinh, Tuan; Scaffidi, Jonathan; Gregas, Molly; Zhang, Yan; Seewaldt, Victoria

2009-08-01

Fiber-optic nanosensors are fabricated by heating and pulling optical fibers to yield sub-micron diameter tips and have been used for in vitro analysis of individual living mammalian cells. Immobilization of bioreceptors (e.g., antibodies, peptides, DNA) selective to targeting analyte molecules of interest provides molecular specificity. Excitation light can be launched into the fiber, and the resulting evanescent field at the tip of the nanofiber can be used to excite target molecules bound to the bioreceptor molecules. The fluorescence or surface-enhanced Raman scattering produced by the analyte molecules is detected using an ultra-sensitive photodetector. This article provides an overview of the development and application of fiber-optic nanosensors for drug discovery. The nanosensors provide minimally invasive tools to probe subcellular compartments inside single living cells for health effect studies (e.g., detection of benzopyrene adducts) and medical applications (e.g., monitoring of apoptosis in cells treated with anticancer drugs).

Optical fiber sensor for low dose gamma irradiation monitoring

NASA Astrophysics Data System (ADS)

de Andrés, Ana I.; Esteban, Ã.`scar; Embid, Miguel

2016-05-01

An optical fiber gamma ray detector is presented in this work. It is based on a Terbium doped Gadolinium Oxysulfide (Gd2O2S:Tb) scintillating powder which cover a chemically etched polymer fiber tip. This etching improves the fluorescence gathering by the optical fiber. The final diameter has been selected to fulfill the trade-off between light gathering and mechanical strength. Powder has been encapsulated inside a microtube where the fiber tip is immersed. The sensor has been irradiated with different air Kerma doses up to 2 Gy/h with a 137Cs source, and the spectral distribution of the fluorescence intensity has been recorded in a commercial grade CCD spectrometer. The obtained signal-to-noise ratio is good enough even for low doses, which has allowed to reduce the integration time in the spectrometer. The presented results show the feasibility for using low cost equipment to detect/measure ionizing radiation as gamma rays are.

Limitations of the commonly used simplified laterally uniform optical fiber probe-tissue interface in Monte Carlo simulations of diffuse reflectance

PubMed Central

Naglič, Peter; Pernuš, Franjo; Likar, Boštjan; Bürmen, Miran

2015-01-01

Light propagation models often simplify the interface between the optical fiber probe tip and tissue to a laterally uniform boundary with mismatched refractive indices. Such simplification neglects the precise optical properties of the commonly used probe tip materials, e.g. stainless steel or black epoxy. In this paper, we investigate the limitations of the laterally uniform probe-tissue interface in Monte Carlo simulations of diffuse reflectance. In comparison to a realistic probe-tissue interface that accounts for the layout and properties of the probe tip materials, the simplified laterally uniform interface is shown to introduce significant errors into the simulated diffuse reflectance. PMID:26504647

Optical fiber-based fluorescent viscosity sensor

NASA Astrophysics Data System (ADS)

Haidekker, Mark A.; Akers, Walter J.; Fischer, Derek; Theodorakis, Emmanuel A.

2006-09-01

Molecular rotors are a unique group of viscosity-sensitive fluorescent probes. Several recent studies have shown their applicability as nonmechanical fluid viscosity sensors, particularly in biofluids containing proteins. To date, molecular rotors have had to be dissolved in the fluid for the measurement to be taken. We now show that molecular rotors may be covalently bound to a fiber-optic tip without loss of viscosity sensitivity. The optical fiber itself may be used as a light guide for emission light (external illumination of the tip) as well as for both emission and excitation light. Covalently bound molecular rotors exhibit a viscosity-dependent intensity increase similar to molecular rotors in solution. An optical fiber-based fluorescent viscosity sensor may be used in real-time measurement applications ranging from biomedical applications to the food industry.

Optical fiber-based fluorescent viscosity sensor.

PubMed

Haidekker, Mark A; Akers, Walter J; Fischer, Derek; Theodorakis, Emmanuel A

2006-09-01

Molecular rotors are a unique group of viscosity-sensitive fluorescent probes. Several recent studies have shown their applicability as nonmechanical fluid viscosity sensors, particularly in biofluids containing proteins. To date, molecular rotors have had to be dissolved in the fluid for the measurement to be taken. We now show that molecular rotors may be covalently bound to a fiber-optic tip without loss of viscosity sensitivity. The optical fiber itself may be used as a light guide for emission light (external illumination of the tip) as well as for both emission and excitation light. Covalently bound molecular rotors exhibit a viscosity-dependent intensity increase similar to molecular rotors in solution. An optical fiber-based fluorescent viscosity sensor may be used in real-time measurement applications ranging from biomedical applications to the food industry.

Quasi-linearly polarized hybrid modes in tapered and metal-coated tips with circular apertures: understanding the functionality of aperture tips

NASA Astrophysics Data System (ADS)

Tugchin, B. N.; Janunts, N.; Steinert, M.; Dietrich, K.; Kley, E. B.; Tünnermann, A.; Pertsch, T.

2017-06-01

In this study, we investigate analytically and experimentally the roles of quasi-linearly polarized (LP), hybrid, plasmonic and photonic modes in optical detection and excitation with aperture tips in scanning near-field optical microscopy. Aperture tips are tapered and metal-coated optical fibers where small circular apertures are made at the apex. In aperture tips, there exist plasmonic modes that are bound at the interface of the metal cladding to the inner dielectric fiber and photonic modes that are guided in the area of the increased index in the dielectric fiber core. The fundamental photonic mode, although excited by the free-space Gaussian beam, experiences cutoff and turns into an evanescent mode. The photonic mode also becomes lossier than the plasmonic mode toward the tip aperture, and its power decay due to absorption and reflection is expected to be at least 10-9. In contrast, the fundamental plasmonic mode has no cutoff and thus reaches all the way to the tip aperture. Due to the non-adiabaticity of both modes’ propagations through the taper below a core radius of 600 nm, there occurs coupling between the modes. The transmission efficiency of the plasmonic mode, including the coupling efficiency and the propagation loss, is expected to be about 10-6 that is at least 3 orders of magnitude larger than that of the photonic mode. Toward the tip aperture, the longitudinal field of the photonic mode becomes stronger than the transverse ones while the transverse fields always dominate for the plasmonic mode. Experimentally, we obtain polarization resolved images of the near-field at the tip aperture and compare with the x- and y-components of the fundamental quasi-LP plasmonic and photonic modes. The results show that not only the pattern but also the intensity ratios of the x- and y-components of the aperture near-field match with that of the fundamental plasmonic mode. Consequently, we conclude that only the plasmonic mode reaches the tip aperture and thus governs the near-field interaction outside the tip aperture. Our conclusion remains valid for all aperture tips regardless of the cladding metal type that mainly influences the total transmission efficiency of the aperture tip.

Preferential type II muscle fiber damage from plyometric exercise.

PubMed

Macaluso, Filippo; Isaacs, Ashwin W; Myburgh, Kathryn H

2012-01-01

Plyometric training has been successfully used in different sporting contexts. Studies that investigated the effect of plyometric training on muscle morphology are limited, and results are controversial with regard to which muscle fiber type is mainly affected. To analyze the skeletal muscle structural and ultrastructural change induced by an acute bout of plyometric exercise to determine which type of muscle fibers is predominantly damaged. Descriptive laboratory study. Research laboratory. Eight healthy, untrained individuals (age = 22 ± 1 years, height = 179.2 ± 6.4 cm, weight = 78.9 ± 5.9 kg). Participants completed an acute bout of plyometric exercise (10 sets of 10 squat-jumps with a 1-minute rest between sets). Blood samples were collected 9 days and immediately before and 6 hours and 1, 2, and 3 days after the acute intervention. Muscle samples were collected 9 days before and 3 days after the exercise intervention. Blood samples were analyzed for creatine kinase activity. Muscle biopsies were analyzed for damage using fluorescent and electron transmission microscopy. Creatine kinase activity peaked 1 day after the exercise bout (529.0 ± 317.8 U/L). Immunofluorescence revealed sarcolemmal damage in 155 of 1616 fibers analyzed. Mainly fast-twitch fibers were damaged. Within subgroups, 7.6% of type I fibers, 10.3% of type IIa fibers, and 14.3% of type IIx fibers were damaged as assessed by losses in dystrophin staining. Similar damage was prevalent in IIx and IIa fibers. Electron microscopy revealed clearly distinguishable moderate and severe sarcomere damage, with damage quantifiably predominant in type II muscle fibers of both the glycolytic and oxidative subtypes (86% and 84%, respectively, versus only 27% of slow-twitch fibers). We provide direct evidence that a single bout of plyometric exercise affected mainly type II muscle fibers.

The PolyScope: a modular design, semidisposable flexible ureterorenoscope system.

PubMed

Bader, Markus Juergen; Gratzke, Christian; Walther, Sebastian; Schlenker, Boris; Tilki, Derya; Hocaoglu, Yasemin; Sroka, Ronald; Stief, Christian Georg; Reich, Oliver

2010-07-01

To characterize the mechanical and optical properties of the PolyScope endoscope system and to examine the clinical outcome in patients who were undergoing ureteronephroscopy. Mechanical assessment involved measurement of the deflection angle and irrigation flow rate. Optical resolution and distortion, field and angle of view, and light transmission and output formed the optical assessment. Clinical assessment was made in a series of consecutive ureteronephroscopy procedures. The optical cord was disconnected after each procedure, and the image fiber was assessed for damage. The mean value for the angle of maximum active tip deflection with an empty working channel was 265 degrees (261-275 degrees). Deflection was impaired most with insertion of the 3.0 F basket (10% decrease) and least with an indwelling 220 microm laser fiber (2% decrease). Irrigation flow rate was 57 mL/min with an empty working channel. Flow was reduced by 50% and 68%, with the insertion of a 200 microm or 365 microm laser probe, respectively, and by 92.5% with a 3.2F basket. No damage to the image fiber occurred. The PolyScope optics system could identify a target of about 0.125 mm at a distance of 2 to 4 mm, based on 3 line-pairs/mm needed for clear identification. Lithotripsy of renal calculi was performed for 40 stone burdens in 32 patients; the resulting stone-free rate was 87.5%. The novel semidisposable ureteroscope system PolyScope was simple to use, effective, and reliable in this preliminary clinical evaluation. It overcomes the inherent fragility of comparable devices, which renders the need for maintenance unnecessary.

Multipurpose fiber-optic sensor with sloped tip

NASA Astrophysics Data System (ADS)

Melnik, Ivan S.; Krivokhizha, A. M.; Ptashnik, O. V.

1991-08-01

Fiber-optic sensors C FOS) are wi. del y used for rioncontact measurements due to their simplicity, small size, insensitivity to I nfl uence of el ectromagneti C fiel ds , hi gh metrol ogi cal characteristics, etc. The operation principle of FOS with intensity modul ati on techni que I s based on the photodetector regi strati on of 1ight , reflected from the control 1 ed surface E I ) . The i ntensi ty of detected 1 1 ght depends on th FOS' s di stance from the control 1 ed surface, its form and inclination to sensor's axis, FOS shift speed, etc. So they can be consider multipurpose. We are devel opi ng FOS wi th i ntensi ty modul ati on techni que wi th traight tips as well as with sloped tips. In FOS with sloped tips the light ring spot is appearing on the controlled surface due to the effect of symmetry. We use thi s phenomena to empl oy refl ected 1 i ght more efficiently and to increase the FOS characteristics. Tak i ng I nto account the fact that pr obl ems of cal cul aWl on of fibers with sloped tip were not analyzed in details earlier-, in particular, only the case of light distribution of parallel beams runni ng was consi dered E 2) we wi I 1 conduct a consi stent cal cul ati on of bounds of i rradi ance fi ci d , created by a fi ber wi th sl oped tip, esti mate I i ght di stri buti on I n a 1 1 ght spot , and determi. ne characteristics of the FOS with sloped tip.

The effect of force on laser fiber burnback during lithotripsy

NASA Astrophysics Data System (ADS)

Aryaei, Ashkan; Chia, Ray; Peng, Steven

2018-02-01

Optical fibers for lithotripsy are designed to deliver the maximum energy precisely to the treatment site without a decrease in performance and without increasing the risks to patients and users. One of the obstacles to constant energy delivery is burnback of the optical fiber tip. So far, researchers identified mechanical, thermal, and optical factors as mechanisms in burnback phenomena. Among mechanical factors, the force applied by urologists against a stone is expected to play a dominant role in burnback. In this study, we introduce a novel technique to measure accurately the stone depth and volume ablation under varying force. Our results show varying burnback lengths on the optical fibers and varying stone depth and volume ablation depending on the optical fiber core size. For instance, the slope of the burnback as a function of the applied force for 273 μm fibers was more than two times higher than for the 550 μm fibers. The slope of the total volume of stone ablated as function of force for 550 μm fibers was almost twice as much as for the 273 μm fibers. The data suggest urologists can maximize the stone ablation rate and minimize fiber tip burnback by controlling the applied force on the optical fiber during a lithotripsy procedure.

Novel splice techniques and micro-hole collapse effect in photonic crystal fibers

NASA Astrophysics Data System (ADS)

Xiao, Limin

Photonic crystal fibers (PCFs) represent one of the most active research areas today in the field of fiber optics. Because of the freedom they offer in their design and novel wave-guiding properties, PCFs have resulted in a number of applications that are difficult to achieve with conventional fibers. In practical applications, low-loss connection PCFs with conventional fibers is a key issue for integrating PCF devices into existing fiber optic systems. However, connecting PCFs to conventional fibers without incurring too much loss is a very challenging problem. Two novel techniques were proposed to solve this problem in the thesis. One is fusion splicing technique; the other is micro-tip technique. First, fusion splicing technique for PCFs is investigated. For fusion splicing SMFs and PCFs having similar mode field diameters, a low-loss joint with good mechanical strength can be formed by choosing a suitably weak fusion current, short fusion time, offset and overlap to minimize the collapse of air holes and well melt two fibers together. For small-core PCFs, an optimum mode field match and an adiabatic mode field variation can be achieved by repeated arc discharges. Low-loss fusion splicing of five different PCFs with SMFs are achieved, including large mode PCF, hollow-core PCF, nonlinear PCFs with low and high air-filling fraction and polarization maintaining PCF. The other novel technique is using micro-tips. The method is based on growing photopolymer micro-tips directly on the end face of SMFs. The shape and the size of the tips can be controlled, by adjusting the laser power, the exposure time and the oxygen diffusion concentration for polymerization, to match its mode field to the small-core PCFs. Micro-hole collapse effect can be used to fabricate selective injection PCFs. The suitable arc discharge energy can cause the cladding holes to collapse while leaving the central hollow core to remain open. Thus a simple method for selective filling the central hole of PCFs is developed. Hybrid PCF guides light by a novel guiding mechanism, which is a combination of index-guiding and bandgap-guiding. The properties of the hybrid PCF are systematically investigated.

Low Velocity Impacts of Variable Tip Radius on Carbon/Epoxy Plates

NASA Astrophysics Data System (ADS)

Delaney, Mac P.

With a growing use of composite materials in aircraft structures, there is a greater need to understand the response of these materials to low velocity impacts. Low velocity impacts from tool drops or ground equipment collisions can be of varying bluntness and can leave little or no visible evidence of damage. Therefore, a need exists to investigate the initiation of internal damage and the relationship between this internal damage and the external visible damage with respect to the bluntness of the impactor. A pendulum impactor was used to impact 76.2 x 127 mm carbon/epoxy panels that were 8, 16, and 24 plies thick. The panels were impacted by hardened steel tips with radii of 12.7 to 76.2 mm. The experimental results show that the failure threshold energies for each panel thickness and tip radius combination occur at a distinct and consistent energy. This threshold increases with impactor bluntness, and this effect is greater for the 8 ply panel than it is for the 16 or 24 ply panels. To describe the visibility of impact damage, the area of delamination was compared to the depth of the dents resulting from the impacts. For the sharper impact tips, there is a clear relationship between the delamination area and the depth of the dents. However, these relationships are dependent on the radius of the impact tip, and for the blunter impact tips no strong correlation could be determined between the delamination area and the depth of the dents.

Determination of temperature and residual laser energy on film fiber-optic thermal converter for diode laser surgery.

PubMed

Liu, Weichao; Kong, Yaqun; Shi, Xiafei; Dong, Xiaoxi; Wang, Hong; Zhao, Jizhi; Li, Yingxin

2017-12-01

The diode laser was utilized in soft tissue incision of oral surgery based on the photothermic effect. The contradiction between the ablation efficiency and the thermal damage has always been in diode laser surgery, due to low absorption of its radiation in the near infrared region by biological tissues. Fiber-optic thermal converters (FOTCs) were used to improve efficiency for diode laser surgery. The purpose of this study was to determine the photothermic effect by the temperature and residual laser energy on film FOTCs. The film FOTC was made by a distal end of optical fiber impacting on paper. The external surface of the converter is covered by a film contained amorphous carbon. The diode laser with 810 nm worked at the different rated power of 1.0 W, 1.5 W, 2.0 W, 3.0 W, 4.0 W, 5.0 W, 6.0 W, 7.0 W, 8.0 W in continuous wave (CW)and pulse mode. The temperature of the distal end of optical fiber was recorded and the power of the residual laser energy from the film FOTC was measured synchronously. The temperature, residual power and the output power were analyzed by linear or exponential regression model and Pearson correlations analysis. The residual power has good linearity versus output power in CW and pulse modes (R 2  = 0.963, P < 0.01 for both). The temperature on film FOTCs increases exponentially with adjusted R 2  = 0.959 in continuous wave mode, while in pulsed mode with adjusted R 2  = 0.934. The temperature was elevated up to about 210 °C and eventually to be a stable state. Film FOTCs centralized approximately 50% of laser energy on the fiber tip both in CW and pulsed mode while limiting the ability of the laser light to interact directly with target tissue. Film FOTCs can concentrate part of laser energy transferred to heat on distal end of optical fiber, which have the feasibility of improving efficiency and reducing thermal damage of deep tissue.

Shortleaf pine hybrids: growth and tip moth damage in southeast Mississippi

Treesearch

Larry H. Lott; Maxine T. Highsmith; C. Dana Nelson

2007-01-01

It is well known that shortleaf pine (Pinus echinata Mill.), loblolly pine (Pinus taeda L.), and Virginia pine (Pinus virginiana Mill.) sustain significantly more Nantucket pine tip moth (Rhyacionia frustrana Comst.) damage than do slash pine (Pinus elliotti var. ...

Medical catheters thermally manipulated by fiber optic bundles

DOEpatents

Chastagner, P.

1992-10-06

A maneuverable medical catheter comprising a flexible tube having a functional tip is described. The catheter is connected to a control source. The functional tip of the catheter carries a plurality of temperature activated elements arranged in parallel and disposed about the functional tip and held in spaced relation at each end. These elements expand when they are heated. A plurality of fiber optic bundles, each bundle having a proximal end attached to the control source and a distal end attached to one of the elements carry light into the elements where the light is absorbed as heat. By varying the optic fiber that is carrying the light and the intensity of the light, the bending of the elements can be controlled and thus the catheter steered. In an alternate embodiment, the catheter carries a medical instrument for gathering a sample of tissue. The instrument may also be deployed and operated by thermal expansion and contraction of its moving parts. 10 figs.

Optical Fiber Sensors for Aircraft Structural Health Monitoring

PubMed Central

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

2015-01-01

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

Optical Fiber Sensors for Aircraft Structural Health Monitoring.

PubMed

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

2015-06-30

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

Fracture toughness of fibrous composite materials

NASA Technical Reports Server (NTRS)

Poe, C. C., Jr.

1984-01-01

Laminates with various proportions of 0 deg, 45 deg, and 90 deg plies were fabricated from T300/5208 and T300/BP-907 graphite/epoxy prepreg tape material. The fracture toughness of each laminate orientation or lay-up was determined by testing center-cracked specimens, and it was also predicted with the general fracture-toughness parameter. The predictions were good except when crack-tip splitting was large, at which time the toughness and strengths tended to be underpredicted. By using predictions, a parametric study was also made of factors that influence fracture toughness. Fiber and matrix properties as well as lay-up were investigated. Without crack-tip splitting, fracture toughness increases in proportion to fiber strength and fiber volume fraction, increases linearly with E(22)/E(11), is largest when the modulus for non-0 deg fibers is greater than that of 0 deg fibers, and is smallest for 0(m)/90(p)(s) lay-ups. (The E(11) and E(22) are Young's moduli of the lamina parallel to and normal to the direction of the fibers, respectively). For a given proportion of 0 deg plies, the most notch-sensitive lay-ups are 0(m)/90(p)(s) and the least sensitive are 0(m)/45(n)(s) and alpha(s). Notch sensitivity increases with the proportion of 0 deg plies and decreases with alpha. Strong, tough matrix materials, which inhibit crack-tip splitting, generally lead to minimum fracture toughness.

The use of optical fiber in endodontic photodynamic therapy. Is it really relevant?

PubMed

Garcez, Aguinaldo S; Fregnani, Eduardo R; Rodriguez, Helena M; Nunez, Silvia C; Sabino, Caetano P; Suzuki, Hideo; Ribeiro, Martha S

2013-01-01

This study analyzed the necessity of use of an optical fiber/diffusor when performing antimicrobial photodynamic therapy (PDT) associated with endodontic therapy. Fifty freshly extracted human single-rooted teeth were used. Conventional endodontic treatment was performed using a sequence of ProTaper (Dentsply Maillefer Instruments), the teeth were sterilized, and the canals were contaminated with Enterococcus faecalis 3 days' biofilm. The samples were divided into five groups: group 1--ten roots irradiated with a laser tip (area of 0.04 cm(2)), group 2--ten roots irradiated with a smaller laser tip (area of 0.028 cm(2)), and group 3--ten teeth with the crown, irradiate with the laser tip with 0.04 cm(2) of area. The forth group (G4) followed the same methodology as group 3, but the irradiation was performed with smaller tip (area of 0.028 cm(2)) and G5 ten teeth with crown were irradiated using a 200-mm-diameter fiber/diffusor coupled to diode laser. Microbiological samples were taken after accessing the canal, after endodontic therapy, and after PDT. Groups 1 and 2 showed a reduction of two logs (99%), groups 3 and 4 of one log (85% and 97%, respectively), and group 5 of four logs (99.99%). Results suggest that the use of PDT added to endodontic treatment in roots canals infected with E. faecalis with the optical fiber/diffusor is better than when the laser light is used directed at the access of cavity.

Fe65 is required for Tip60-directed histone H4 acetylation at DNA strand breaks

PubMed Central

Stante, Maria; Minopoli, Giuseppina; Passaro, Fabiana; Raia, Maddalena; Vecchio, Luigi Del; Russo, Tommaso

2009-01-01

Fe65 is a binding partner of the Alzheimer's β-amyloid precursor protein APP. The possible involvement of this protein in the cellular response to DNA damage was suggested by the observation that Fe65 null mice are more sensitive to genotoxic stress than WT counterpart. Fe65 associated with chromatin under basal conditions and its involvement in DNA damage repair requires this association. A known partner of Fe65 is the histone acetyltransferase Tip60. Considering the crucial role of Tip60 in DNA repair, we explored the hypothesis that the phenotype of Fe65 null cells depended on its interaction with Tip60. We demonstrated that Fe65 knockdown impaired recruitment of Tip60-TRRAP complex to DNA double strand breaks and decreased histone H4 acetylation. Accordingly, the efficiency of DNA repair was decreased upon Fe65 suppression. To explore whether APP has a role in this mechanism, we analyzed a Fe65 mutant unable to bind to APP. This mutant failed to rescue the phenotypes of Fe65 null cells; furthermore, APP/APLP2 suppression results in the impairment of recruitment of Tip60-TRRAP complex to DNA double strand breaks, decreased histone H4 acetylation and repair efficiency. On these bases, we propose that Fe65 and its interaction with APP play an important role in the response to DNA damage by assisting the recruitment of Tip60-TRRAP to DNA damage sites. PMID:19282473

Ultra high tip speed (670.6 m/sec) fan stage with composite rotor: Aerodynamic and mechanical design

NASA Technical Reports Server (NTRS)

Halle, J. E.; Burger, G. D.; Dundas, R. E.

1977-01-01

A highly loaded, single-stage compressor having a tip speed of 670.6 m/sec was designed for the purpose of investigating very high tip speeds and high aerodynamic loadings to obtain high stage pressure ratios at acceptable levels of efficiency. The design pressure ratio is 2.8 at an adiabatic efficiency of 84.4%. Corrected design flow is 83.4 kg/sec; corrected design speed is 15,200 rpm; and rotor inlet tip diameter is 0.853 m. The rotor uses multiple-circular-arc airfoils from 0 to 15% span, precompression airfoils assuming single, strong oblique shocks from 21 to 43% span, and precompression airfoils assuming multiple oblique shocks from 52% span to the tip. Because of the high tip speeds, the rotor blades are designed to be fabricated of composite materials. Two composite materials were investigated: Courtaulds HTS graphite fiber in a Kerimid 601 polyimide matrix and the same fibers in a PMR polyimide matrix. In addition to providing a description of the aerodynamic and mechanical design of the 670.0 m/sec fan, discussion is presented of the results of structural tests of blades fabricated with both types of matrices.

Passive Impact Damage Detection of Fiber Glass Composite Panels

DTIC Science & Technology

2013-12-19

PASSIVE IMPACT DAMAGE DETECTION OF FIBER GLASS COMPOSITE PANELS. By BRUNO ZAMORANO-SENDEROS A dissertation...COVERED 04-11-2012 to 10-12-2013 4. TITLE AND SUBTITLE PASSIVE IMPACT DAMAGE DETECTION OF FIBER GLASS COMPOSITE PANELS 5a. CONTRACT NUMBER 5b...process. .................................... 31 Figure 3-8 Sensor attached to the fiber glass fabric

Preferential Type II Muscle Fiber Damage From Plyometric Exercise

PubMed Central

Macaluso, Filippo; Isaacs, Ashwin W.; Myburgh, Kathryn H.

2012-01-01

Context Plyometric training has been successfully used in different sporting contexts. Studies that investigated the effect of plyometric training on muscle morphology are limited, and results are controversial with regard to which muscle fiber type is mainly affected. Objective To analyze the skeletal muscle structural and ultrastructural change induced by an acute bout of plyometric exercise to determine which type of muscle fibers is predominantly damaged. Design Descriptive laboratory study. Setting Research laboratory. Patients or Other Participants Eight healthy, untrained individuals (age = 22 ± 1 years, height = 179.2 ± 6.4 cm, weight = 78.9 ± 5.9 kg). Intervention(s) Participants completed an acute bout of plyometric exercise (10 sets of 10 squat-jumps with a 1-minute rest between sets). Main Outcome Measure(s) Blood samples were collected 9 days and immediately before and 6 hours and 1, 2, and 3 days after the acute intervention. Muscle samples were collected 9 days before and 3 days after the exercise intervention. Blood samples were analyzed for creatine kinase activity. Muscle biopsies were analyzed for damage using fluorescent and electron transmission microscopy. Results Creatine kinase activity peaked 1 day after the exercise bout (529.0 ± 317.8 U/L). Immunofluorescence revealed sarcolemmal damage in 155 of 1616 fibers analyzed. Mainly fast-twitch fibers were damaged. Within subgroups, 7.6% of type I fibers, 10.3% of type IIa fibers, and 14.3% of type IIx fibers were damaged as assessed by losses in dystrophin staining. Similar damage was prevalent in IIx and IIa fibers. Electron microscopy revealed clearly distinguishable moderate and severe sarcomere damage, with damage quantifiably predominant in type II muscle fibers of both the glycolytic and oxidative subtypes (86% and 84%, respectively, versus only 27% of slow-twitch fibers). Conclusions We provide direct evidence that a single bout of plyometric exercise affected mainly type II muscle fibers. PMID:22889657

Progressive Fracture and Damage Tolerance of Composite Pressure Vessels

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Gotsis, Pascal K.; Minnetyan, Levon

1997-01-01

Structural performance (integrity, durability and damage tolerance) of fiber reinforced composite pressure vessels, designed for pressured shelters for planetary exploration, is investigated via computational simulation. An integrated computer code is utilized for the simulation of damage initiation, growth, and propagation under pressure. Aramid fibers are considered in a rubbery polymer matrix for the composite system. Effects of fiber orientation and fabrication defect/accidental damages are investigated with regard to the safety and durability of the shelter. Results show the viability of fiber reinforced pressure vessels as damage tolerant shelters for planetary colonization.

Fatigue damage accumulation in various metal matrix composites

NASA Technical Reports Server (NTRS)

Johnson, W. S.

1987-01-01

The purpose of this paper is to review some of the latest understanding of the fatigue behavior of continuous fiber reinforced metal matrix composites. The emphasis is on the development of an understanding of different fatigue damage mechanisms and why and how they occur. The fatigue failure modes in continuous fiber reinforced metal matrix composites are controlled by the three constituents of the system: fiber, matrix, and fiber/matrix interface. The relative strains to fatigue failure of the fiber and matrix will determine the failure mode. Several examples of matrix, fiber, and self-similar damage growth dominated fatigue damage are given for several metal matrix composite systems. Composite analysis, failure modes, and damage modeling are discussed. Boron/aluminum, silicon-carbide/aluminum, FP/aluminum, and borsic/titanium metal matrix composites are discussed.

Coherent beam combining of collimated fiber array based on target-in-the-loop technique

NASA Astrophysics Data System (ADS)

Li, Xinyang; Geng, Chao; Zhang, Xiaojun; Rao, Changhui

2011-11-01

Coherent beam combining (CBC) of fiber array is a promising way to generate high power and high quality laser beams. Target-in-the-loop (TIL) technique might be an effective way to ensure atmosphere propagation compensation without wavefront sensors. In this paper, we present very recent research work about CBC of collimated fiber array using TIL technique at the Key Lab on Adaptive Optics (KLAO), CAS. A novel Adaptive Fiber Optics Collimator (AFOC) composed of phase-locking module and tip/tilt control module was developed. CBC experimental setup of three-element fiber array was established. Feedback control is realized using stochastic parallel gradient descent (SPGD) algorithm. The CBC based on TIL with piston and tip/tilt correction simultaneously is demonstrated. And the beam pointing to locate or sweep position of combined spot on target was achieved through TIL technique too. The goal of our work is achieve multi-element CBC for long-distance transmission in atmosphere.

Radiotherapy fiber dosimeter probes based on silver-only coated hollow glass waveguides

NASA Astrophysics Data System (ADS)

Darafsheh, Arash; Melzer, Jeffrey E.; Harrington, James A.; Kassaee, Alireza; Finlay, Jarod C.

2018-01-01

Manifestation of Čerenkov radiation as a contaminating signal is a significant issue in radiation therapy dose measurement by fiber-coupled scintillator dosimeters. To enhance the scintillation signal transmission while minimizing Čerenkov radiation contamination, we designed a fiber probe using a silver-only coated hollow waveguide (HWG). The HWG with scintillator inserted in its tip, embedded in tissue-mimicking phantoms, was irradiated with clinical electron and photon beams generated by a medical linear accelerator. Optical spectra of the irradiated tip were taken using a fiber spectrometer, and the signal was deconvolved with a linear fitting algorithm. The resultant decomposed spectra of the scintillator with and without Čerenkov correction were in agreement with measurements performed by a standard electron diode and ion chamber for electron and photon beam dosimetry, respectively, indicating the minimal effect of Čerenkov contamination in the HWG-based dosimeter. Furthermore, compared with a silver/dielectric-coated HWG fiber dosimeter design, we observed higher signal transmission in the design based on the use of silver-only HWG.

DAMAGE MODELING OF INJECTION-MOLDED SHORT- AND LONG-FIBER THERMOPLASTICS

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

Nguyen, Ba Nghiep; Kunc, Vlastimil; Bapanapalli, Satish K.

2009-10-30

This article applies the recent anisotropic rotary diffusion – reduced strain closure (ARD-RSC) model for predicting fiber orientation and a new damage model for injection-molded long-fiber thermoplastics (LFTs) to analyze progressive damage leading to total failure of injection-molded long-glass-fiber/polypropylene (PP) specimens. The ARD-RSC model was implemented in a research version of the Autodesk Moldflow Plastics Insight (MPI) processing code, and it has been used to simulate injection-molding of a long-glass-fiber/PP plaque. The damage model combines micromechanical modeling with a continuum damage mechanics description to predict the nonlinear behavior due to plasticity coupled with damage in LFTs. This model has beenmore » implemented in the ABAQUS finite element code via user-subroutines and has been used in the damage analyses of tensile specimens removed from the injection-molded long-glass-fiber/PP plaques. Experimental characterization and mechanical testing were performed to provide input data to support and validate both process modeling and damage analyses. The predictions are in agreement with the experimental results.« less

Fomation of corn fiber gum-milk protein conjugates and their molecular characterization

USDA-ARS?s Scientific Manuscript database

Corn fiber arabinoxylan is hemicellulose B isolated from the fibrous portions (pericarp, tip cap, and endosperm cell wall fractions) of corn kernels and is commonly referred to as corn fiber gum (CFG). Our previous studies showed that CFG isolated from corn bran (a byproduct of corn dry milling) co...

Corn fiber gum: New structure/function relationships for this potential beverage flavor stabilizer

USDA-ARS?s Scientific Manuscript database

Corn fiber arabinoxylan is a hemicellulose B isolated from the fibrous portions (pericarp, tip cap, and endosperm cell wall fractions) of corn kernels by alkaline solution, often in the presence of hydrogen peroxide and is commonly referred to as “Corn fiber gum” (CFG). The unique polysaccharide, C...

High-power diffusing-tip fibers for interstitial photocoagulation

NASA Astrophysics Data System (ADS)

Sinofsky, Edward L.; Farr, Norman; Baxter, Lincoln; Weiler, William

1997-05-01

A line of optical fiber based diffusing tips has been designed, developed, and tested that are capable of distributing tens of watts of cw laser power over lengths ranging from two millimeters to over 10 cm. The result is a flexible non-stick diffuser capable of coagulating large volumes of tissue in reasonably short exposures of 3 - 5 minutes. Sub-millimeter diameter devices have a distinct effect on reducing the force needed to insert the applicator interstitially into tissue. Utilizing our design approach, we have produced diffusers based on 200 micrometer core fiber that has delivered over 35 watts of Nd:YAG energy over diffusion lengths as short as 4 mm. These applicators are being tested for applications in oncology, cardiology, electrophysiology, urology and gynecology.

Wide angle near-field optical probes by reverse tube etching.

PubMed

Patanè, S; Cefalì, E; Arena, A; Gucciardi, P G; Allegrini, M

2006-04-01

We present a simple modification of the tube etching process for the fabrication of fiber probes for near-field optical microscopy. It increases the taper angle of the probe by a factor of two. The novelty is that the fiber is immersed in hydrofluoric acid and chemically etched in an upside-down geometry. The tip formation occurs inside the micrometer tube cavity formed by the polymeric jacket. By applying this approach, called reverse tube etching, to multimode fibers with 200/250 microm core/cladding diameter, we have fabricated tapered regions featuring high surface smoothness and average cone angles of approximately 30 degrees . A simple model based on the crucial role of the gravity in removing the etching products, explains the tip formation process.

MEH-PPV film thickness influenced fluorescent quenching of tip-coated plastic optical fiber sensors

NASA Astrophysics Data System (ADS)

Yusufu, A. M.; Noor, A. S. M.; Tamchek, N.; Abidin, Z. Z.

2017-12-01

The performance of plastic optical fiber sensors in detecting nitro aromatic explosives 1,4-dinitrobenzene (DNB) have been investigated by fluorescence spectroscopy and analyzed by using fluorescence quenching technique. The plastic optical fiber utilized is 90 degrees cut tip and dip-coated with conjugated polymer MEH-PPV poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] thin films for detection conjugants. The thicknesses of the MEH-PPV coating were varied to improvise the sensitivity whilst slowly reducing the fluorescence intensity. It was shown that fluorescence intensity from thinner film decreased by (82% in 40 s) in the presence of DNB signifying an improvement of 28% reduction with time 13 s less than that of the thicker film.

Three-axis force sensor with fiber Bragg grating.

PubMed

Hyundo Choi; Yoan Lim; Junhyung Kim

2017-07-01

Haptic feedback is critical for many surgical tasks, and it replicates force reflections at the surgical site. To meet the force reflection requirements, we propose a force sensor with an optical fiber Bragg grating (FBG) for robotic surgery. The force sensor can calculate three directional forces of an instrument from the strain of three FBGs, even under electromagnetic interference. A flexible ring-shape structure connects an instrument tip and fiber strain gages to sense three directional force. And a stopper mechanism is added in the structure to avoid plastic deformation under unexpected large force on the instrument tip. The proposed sensor is experimentally verified to have a sensing range from -12 N to 12 N, and its sensitivity was less than 0.06 N.

BRANCHING PATTERNS OF INDIVIDUAL SYMPATHETIC NEURONS IN CULTURE

PubMed Central

Bray, D.

1973-01-01

The growth of single sympathetic neurons in tissue culture was examined with particular regard to the way in which the patterns of axonal or dendritic processes (here called nerve fibers), were formed. The tips of the fibers were seen to advance in straight lines and to grow at rates that did not vary appreciably with time, with their position in the cell outgrowth, or with the fiber diameter. Most of the branch points were formed by the bifurcation of a fiber tip (growth cone), apparently at random, and thereafter remained at about the same distance from the cell body. It seemed that the final shape of a neuron was the result of the reiterated and largely autonomous activities of the growth cones. The other parts of the cell played a supportive role but, apart from this, had no obvious influence on the final pattern of branches formed. PMID:4687915

3D silicon neural probe with integrated optical fibers for optogenetic modulation.

PubMed

Kim, Eric G R; Tu, Hongen; Luo, Hao; Liu, Bin; Bao, Shaowen; Zhang, Jinsheng; Xu, Yong

2015-07-21

Optogenetics is a powerful modality for neural modulation that can be useful for a wide array of biomedical studies. Penetrating microelectrode arrays provide a means of recording neural signals with high spatial resolution. It is highly desirable to integrate optics with neural probes to allow for functional study of neural tissue by optogenetics. In this paper, we report the development of a novel 3D neural probe coupled simply and robustly to optical fibers using a hollow parylene tube structure. The device shanks are hollow tubes with rigid silicon tips, allowing the insertion and encasement of optical fibers within the shanks. The position of the fiber tip can be precisely controlled relative to the electrodes on the shank by inherent design features. Preliminary in vivo rat studies indicate that these devices are capable of optogenetic modulation simultaneously with 3D neural signal recording.

Regulation of Histone Acetyltransferase TIP60 Function by Histone Deacetylase 3

PubMed Central

Yi, Jingjie; Huang, Xiangyang; Yang, Yuxia; Zhu, Wei-Guo; Gu, Wei; Luo, Jianyuan

2014-01-01

The key member of the MOZ (monocyticleukaemia zinc finger protein), Ybf2/Sas3, Sas2, and TIP60 acetyltransferases family, Tat-interactive protein, 60 kD (TIP60), tightly modulates a wide array of cellular processes, including chromatin remodeling, gene transcription, apoptosis, DNA repair, and cell cycle arrest. The function of TIP60 can be regulated by SIRT1 through deacetylation. Here we found that TIP60 can also be functionally regulated by HDAC3. We identified six lysine residues as its autoacetylation sites. Mutagenesis of these lysines to arginines completely abolishes the autoacetylation of TIP60. Overexpression of HDAC3 increases TIP60 ubiquitination levels. However, unlike SIRT1, HDAC3 increased the half-life of TIP60. Further study found that HDAC3 colocalized with TIP60 both in the nucleus and the cytoplasm, which could be the reason why HDAC3 can stabilize TIP60. The deacetylation of TIP60 by both SIRT1 and HDAC3 reduces apoptosis induced by DNA damage. Knockdown of HDAC3 in cells increased TIP60 acetylation levels and increased apoptosis after DNA damage. Together, our findings provide a better understanding of TIP60 regulation mechanisms, which is a significant basis for further studies of its cellular functions. PMID:25301942

Nanostructural evolution during emission of CsI-coated carbon fiber cathodes

NASA Astrophysics Data System (ADS)

Drummy, Lawrence F.; Apt, Scott; Shiffler, Don; Golby, Ken; LaCour, Matt; Maruyama, Benji; Vaia, Richard A.

2010-06-01

Carbon-based nanofiber and microfiber cathodes exhibit very low voltages for the onset of electron emission, and thus provide exciting opportunities for applications ranging from high power microwave sources to field emission displays. CsI coatings have been experimentally shown to lower the work function for emission from the fiber tips, although little is known about the microstructure of the fibers themselves in their as-received state, after coating with CsI, or after being subjected to high voltage cycling. Longitudinal cross sections of the original, unused CsI-coated fibers produced by focused ion beam lift-out revealed a nanostructured graphitic core surrounded by an amorphous carbon shell with submicron sized islands of crystalline CsI on the outer surface. Aberration-corrected high resolution electron microscopy (HREM) of the fiber core achieved 0.10 nm resolution, with the graphite (200) clearly visible in digital fast Fourier transformations of the 2-4 nm highly ordered graphitic domains. As the cathode fibers are cycled at high voltage, HREM demonstrates that the graphitic ordering of the core increases with the number of cycles, however the structure and thickness of the amorphous carbon layer remains unchanged. These results are consistent with micro-Raman measurements of the fiber disordered/graphitic (D/G) band ratios. After high voltage cycling, a uniform ˜100 nm film at the fiber tip was evident in both bright field transmission electron microscopy (TEM) and high angle annular dark field scanning TEM (STEM). Low-dose electron diffraction techniques confirmed the amorphous nature of this film, and STEM with elemental mapping via x-ray energy dispersive spectroscopy indicates this layer is composed of CsIO. The oxidative evolution of tip composition and morphology due to impurities in the chamber, along with increased graphitization of the fiber core, contributes to changes in emission behavior with cycling.

Sealing apparatus for airfoils of gas turbine engines

DOEpatents

Jones, Russell B.

1998-01-01

An improved airfoil tip sealing apparatus is disclosed wherein brush seals are attached to airfoil tips with the distal ends of the brush seal fibers sealingly contacting opposing wall surfaces. Embodiments for variable vanes, stators and both cooled and uncooled turbine blade applications are disclosed.

Alleviation effect of alginate-derived oligosaccharides on Vicia faba root tip cells damaged by cadmium.

PubMed

Ma, L J; Zhang, Y; Bu, N; Wang, S H

2010-02-01

Cadmium has been shown to prevent Vicia faba growth by inhibiting cell mitosis. In this study we investigated the role of Alginate-derived Oligosaccharides (ADO) in alleviating Vicia faba root tip cells damaged by 6 and 8 mg L(-1) CdCl2. Micronucleus assay and chromosomal aberration assay were used to determine mitotic index, micronucleus frequency and chromosomal aberration frequency. The results showed that micronucleus frequency of Vicia faba root tip cells was inhibited under all the ADO concentrations. Especially, the inhibition ratio of 0.125% ADO highly reached 66.11 and 67.17% in 6 and 8 mg L(-1) CdCl2, respectively. Furthermore, the mitotic index increased (p < 0.05) and chromosomal aberration frequency decreased (p < 0.05) under all the ADO concentrations. This indicated that ADO had a significant alleviation effect on Vicia faba root tip cells damaged by cadmium.

Fatigue damage evaluation of short fiber CFRP based on phase information of thermoelastic temperature change

NASA Astrophysics Data System (ADS)

Sakagami, Takahide; Shiozawa, Daiki; Nakamura, Yu; Nonaka, Shinichi; Hamada, Kenichi

2017-05-01

Carbon fiber-reinforced plastic (CFRP) is widely used for structural members of transportation vehicles such as automobile, aircraft or spacecraft, utilizing its excellent specific strength and specific rigidity in contrast with the metal. Short carbon fiber composite materials are receiving a lot of attentions because of their excellent moldability and productivity, however they show complicated behaviors in fatigue fracture due to the random fibers orientation. In this study, thermoelastic stress analysis (TSA) using an infrared thermography was applied to the evaluation of fatigue damage in short carbon fiber composites. The distributions of the thermoelastic temperature change was measured during the fatigue test, as well as the phase difference between the thermoelastic temperature change and applied loading signal. Evolution of fatigue damages was detected from distributions of thermoelastic temperature change according to the thermoelastic damage analysis (TDA) procedure. It was also found that fatigue damage evolution was clearly detected than ever by the newly developed thermoelastic phase damage analysis (TPDA) in which damaged area was emphasized in the differential phase delay images utilizing the nature that carbon fiber show opposite phase thermoelastic temperature change.

Tapered fiber optical tweezers for microscopic particle trapping: fabrication and application

NASA Astrophysics Data System (ADS)

Liu, Zhihai; Guo, Chengkai; Yang, Jun; Yuan, Libo

2006-12-01

A novel single tapered fiber optical tweezers is proposed and fabricated by heating and drawing technology. The microscopic particle tapping performance of this special designed tapered fiber probe is demonstrated and investigated. The distribution of the optical field emerging from the tapered fiber tip is numerically calculated based on the beam propagation method. The trapping force FDTD analysis results, both axial and transverse, are also given.

Optical bio-sniffer for ethanol vapor using an oxygen-sensitive optical fiber.

PubMed

Mitsubayashi, Kohji; Kon, Takuo; Hashimoto, Yuki

2003-11-30

An optical bio-sniffer for ethanol was constructed by immobilizing alcohol oxidase (AOD) onto a tip of a fiber optic oxygen sensor with a tube-ring, using an oxygen sensitive ruthenium organic complex (excitation, 470 nm; fluorescent, 600 nm). A reaction unit for circulating buffer solution was applied to the tip of the device. After the experiment in the liquid phase, the sniffer-device was applied for gas analysis using a gas flow measurement system with a gas generator. The optical device was applied to detect the oxygen consumption induced by AOD enzymatic reaction with alcohol application. The sensor in the liquid phase was used to measure ethanol solution from 0.50 to 9.09 mmol/l. Then, the bio-sniffer was calibrated against ethanol vapor from 0.71 to 51.49 ppm with good gas-selectivity based on the AOD substrate specificity. The bio-sniffer with the reaction unit was also used to monitor the concentration change of gaseous ethanol by rinsing and cleaning the fiber tip and the enzyme membrane with buffer solution.

Effect of low velocity impact damage on the natural frequency of composite plates

NASA Astrophysics Data System (ADS)

Chok, E. Y. L.; Majid, D. L. A. A.; Harmin, M. Y.

2017-12-01

Biodegradable natural fibers have been suggested to replace the hazardous synthetic fibers in many aerospace applications. However, this notion has been limited due to their low mechanical properties, which leads to the idea of hybridizing the two materials. Many aircraft components such as radome, aft body and wing are highly susceptible to low velocity impact damage while in-service. The damages degrade the structural integrity of the components and change their dynamic characteristics. In worst case scenario, the changes can lead to resonance, which is an excessive vibration. This research is conducted to study the dynamic characteristic changes of low velocity impact damaged hybrid composites that is designed for aircraft radome applications. Three materials, which are glass fiber, kenaf fiber and kenaf/glass fiber hybrid composites, have been impacted with 3J, 6J and 9J of energy. Cantilevered and also vertically clamped boundary conditions are used and the natural frequencies are extracted for each of the specimens. The obtained results show that natural frequency decreases with increasing impact level. Cantilevered condition is found to induce lower modes due to the gravitational pull. To eliminate mass and geometrical effects, normalized modes are computed. Among the three materials considered, glass fiber composites have displayed the highest normalized frequency that reflects on its higher stiffness compared to the other two materials. As the damage level is increased, glass fiber composites have shown the highest frequency reduction to a maximum of 35% while kenaf composites have the least frequency reduction in the range of 1 - 18%. Thus, kenaf fiber is taken to be helpful in stalling the damage progression and reducing the effect of damage. This has been proven when the percentage frequency decrement shown by kenaf/glass fiber composite lies between glass fiber and kenaf fiber composites.

Structurally integrated fiber optic damage assessment system for composite materials.

PubMed

Measures, R M; Glossop, N D; Lymer, J; Leblanc, M; West, J; Dubois, S; Tsaw, W; Tennyson, R C

1989-07-01

Progress toward the development of a fiber optic damage assessment system for composite materials is reported. This system, based on the fracture of embedded optical fibers, has been characterized with respect to the orientation and location of the optical fibers in the composite. Together with a special treatment, these parameters have been tailored to yield a system capable of detecting the threshold of damage for various impacted Kevlar/epoxy panels. The technique has been extended to measure the growth of a damage region which could arise from either impact, manufacturing flaws, or static overloading. The mechanism of optical fiber fracture has also been investigated. In addition, the influence of embedded optical fibers on the tensile and compressive strength of the composite material has been studied. Image enhanced backlighting has been shown to be a powerful and convenient method of assessing internal damage to translucent composite materials.

Fibers comprised of epitaxially grown single-wall carbon nanotubes, and a method for added catalyst and continuous growth at the tip

DOEpatents

Kittrell, W. Carter; Wang, Yuhuang; Kim, Myung Jong; Hauge, Robert H.; Smalley, Richard E.; Marek leg, Irene Morin

2010-06-01

The present invention is directed to fibers of epitaxially grown single-wall carbon nanotubes (SWNTs) and methods of making same. Such methods generally comprise the steps of: (a) providing a spun SWNT fiber; (b) cutting the fiber substantially perpendicular to the fiber axis to yield a cut fiber; (c) etching the cut fiber at its end with a plasma to yield an etched cut fiber; (d) depositing metal catalyst on the etched cut fiber end to form a continuous SWNT fiber precursor; and (e) introducing feedstock gases under SWNT growth conditions to grow the continuous SWNT fiber precursor into a continuous SWNT fiber.

Irrigation and fertilization effects on Nantucket Pine Tip Moth (Lepidoptera: Tortricidae) Damage levels and pupal weight in an intensively-managed pine plantation.

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

Coyle, David, R.; Nowak, John, T.; Fettig, Christopher, J.

2003-10-01

The widespread application of intensive forest management practices throughout the southeastern U.S. has increased loblolly pine, Pinus taeda L., yields and shortened conventional rotation lengths. Fluctuations in Nantucket pine tip moth, Rhyacionia frustrana (Comstock), population density and subsequent damage levels have been linked to variations in management intensity. We examined the effects of two practices, irrigation and fertilization, on R. frustrana damage levels and pupal weights in an intensively-managed P. taeda plantation in South Carolina. Trees received intensive weed control and one of the following treatments; irrigation only. fertilization only, irrigation + fertilization, or control. Mean whole-tree tip moth damagemore » levels ranged from <1 to 48% during this study. Damage levels differed significantly among treatments in two tip moth generations in 2001, but not 2000. Pupal weight was significantly heavier in fertilization compared to the irrigation treatment in 2000, but no significant differences were observed in 2001. Tree diameter. height. and aboveground volume were significantly greater in the irrigation + fertilization than in the irrigation treatment after two growing seasons. Our data suggest that intensive management practices that include irrigation and fertilization do not consistently increase R. frustrana damage levels and pupal weights as is commonly believed. However, tip moth suppression efforts in areas adjacent to our study may have partially reduced the potential impacts of R. frustrana on this experiment.« less

Sealing apparatus for airfoils of gas turbine engines

DOEpatents

Jones, R.B.

1998-05-19

An improved airfoil tip sealing apparatus is disclosed wherein brush seals are attached to airfoil tips with the distal ends of the brush seal fibers sealingly contacting opposing wall surfaces. Embodiments for variable vanes, stators and both cooled and uncooled turbine blade applications are disclosed. 17 figs.

Corrugated metal-coated tapered tip for scanning near-field optical microscope.

PubMed

Antosiewicz, Tomasz J; Szoplik, Tomasz

2007-08-20

This paper addresses an important issue of light throughput of a metal-coated tapered tip for scanning near-field microscope (SNOM). Corrugations of the interface between the fiber core and metal coating in the form of parallel grooves of different profiles etched in the core considerably increase the energy throughput. In 2D FDTD simulations in the Cartesian coordinates we calculate near-field light emitted from such tips. For a certain wavelength range total intensity of forward emission from the corrugated tip is 10 times stronger than that from a classical tapered tip. When realized in practice the idea of corrugated tip may lead up to twice better resolution of SNOM.

Generation of spirally polarized propagation-invariant beam using fiber microaxicon.

PubMed

Philip, Geo M; Viswanathan, Nirmal K

2011-10-01

We present here a fiber microaxicon (MA)based method to generate spirally polarized propagation-invariant optical beam. MA chemically etched in the tip of a two-mode fiber efficiently converts the generic cylindrically polarized vortex fiber mode into a spirally polarized propagation-invariant (Bessel-type) beam via radial dependence of polarization rotation angle. The combined roles of helico-conical phase and nonparaxial propagation in the generation and characteristics of the output beam from the fiber MA are discussed. © 2011 Optical Society of America

[Progress in laser neurosurgery].

PubMed

Majchrzak, H; Kopera, M; Idzik, M

1991-01-01

Nd:YAG lasers with different wavelengths are used in neurosurgery. Their great advantage is the ability of coagulation of blood vessels and delivery through flexible fiber optics . Nd:YAG laser with wavelength 1.318 microns is used, besides, to connect blood vessels and nerves. CO2 laser is the best cutting tool but requires, for delivery rigid cable. Both types of lasers cause shrinkage and vaporisation of the tumors what facilitates its removing without greater traumatisation of surrounding tissues. The introduction of sapphire contact tips to Nd:YAG and argon lasers enables application of small laser powers and diminish the area of damage in surrounding structures. Contact laser is used for destroying of tumours, coagulation of blood vessels, restoration of patency of the main arteries, interstitial denaturation of gliomas and denaturation of the nucleus pulposus in lumbar vertebral column.

SU-E-T-610: Phosphor-Based Fiber Optic Probes for Proton Beam Characterization

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

Darafsheh, A; Soldner, A; Liu, H

2015-06-15

Purpose: To investigate feasibility of using fiber optics probes with rare-earth-based phosphor tips for proton beam radiation dosimetry. We designed and fabricated a fiber probe with submillimeter resolution (<0.5 mm3) based on TbF3 phosphors and evaluated its performance for measurement of proton beam including profiles and range. Methods: The fiber optic probe with TbF3 phosphor tip, embedded in tissue-mimicking phantoms was irradiated with double scattering proton beam with energy of 180 MeV. Luminescence spectroscopy was performed by a CCD-coupled spectrograph to analyze the emission spectra of the fiber tip. In order to measure the spatial beam profile and percentage depthmore » dose, we used singular value decomposition method to spectrally separate the phosphors ionoluminescence signal from the background Cerenkov radiation signal. Results: The spectra of the TbF3 fiber probe showed characteristic ionoluminescence emission peaks at 489, 542, 586, and 620 nm. By using singular value decomposition we found the contribution of the ionoluminescence signal to measure the percentage depth dose in phantoms and compared that with measurements performed with ion chamber. We observed quenching effect at the spread out Bragg peak region, manifested as under-responding of the signal, due to the high LET of the beam. However, the beam profiles were not dramatically affected by the quenching effect. Conclusion: We have evaluated the performance of a fiber optic probe with submillimeter resolution for proton beam dosimetry. We demonstrated feasibility of spectral separation of the Cerenkov radiation from the collected signal. Such fiber probes can be used for measurements of proton beams profile and range. The experimental apparatus and spectroscopy method developed in this work provide a robust platform for characterization of proton-irradiated nanophosphor particles for ultralow fluence photodynamic therapy or molecular imaging applications.« less

Engineering Interfaces in Metal Matrix Composites (Volume 3)

DTIC Science & Technology

1988-06-10

Howard S. Landis and James A. Cornie Interfaces with Controlled Toughness as Mechanical Fuses to Isolate Fibers from Damage -Vijay Gupta, All S. Argon and...protect the re- inforcing fiber from damage resulting from fracture of surrounding fibers or from misfitting reaction products between the matrix and...properties to govern the decoupling of the fiber from its damaging surroundings, while maintaining full wetting contact along the interface between

On the threshold conditions for electron beam damage of asbestos amosite fibers in the transmission electron microscope (TEM).

PubMed

Martin, Joannie; Beauparlant, Martin; Sauvé, Sébastien; L'Espérance, Gilles

2016-12-01

Asbestos amosite fibers were investigated to evaluate the damage caused by a transmission electron microscope (TEM) electron beam. Since elemental x-ray intensity ratios obtained by energy dispersive x-ray spectroscopy (EDS) are commonly used for asbestos identification, the impact of beam damage on these ratios was evaluated. It was determined that the magnesium/silicon ratio best represented the damage caused to the fiber. Various tests showed that most fibers have a current density threshold above which the chemical composition of the fiber is modified. The value of this threshold current density varied depending on the fiber, regardless of fiber diameter, and in some cases could not be determined. The existence of a threshold electron dose was also demonstrated. This value was dependent on the current density used and can be increased by providing a recovery period between exposures to the electron beam. This study also established that the electron beam current is directly related to the damage rate above a current density of 165 A/cm 2 . The large number of different results obtained suggest, that in order to ensure that the amosite fibers are not damaged, analysis should be conducted below a current density of 100 A/cm 2 .

Improving the lateral resolution of quartz tuning fork-based sensors in liquid by integrating commercial AFM tips into the fiber end.

PubMed

Gonzalez, Laura; Martínez-Martín, David; Otero, Jorge; de Pablo, Pedro José; Puig-Vidal, Manel; Gómez-Herrero, Julio

2015-01-14

The use of quartz tuning fork sensors as probes for scanning probe microscopy is growing in popularity. Working in shear mode, some methods achieve a lateral resolution comparable with that obtained with standard cantilevered probes, but only in experiments conducted in air or vacuum. Here, we report a method to produce and use commercial AFM tips in electrically driven quartz tuning fork sensors operating in shear mode in a liquid environment. The process is based on attaching a standard AFM tip to the end of a fiber probe which has previously been sharpened. Only the end of the probe is immersed in the buffer solution during imaging. The lateral resolution achieved is about 6 times higher than that of the etched microfiber on its own.

Investigation of translaminar fracture in fibrereinforced composite laminates---applicability of linear elastic fracture mechanics and cohesive-zone model

NASA Astrophysics Data System (ADS)

Hou, Fang

With the extensive application of fiber-reinforced composite laminates in industry, research on the fracture mechanisms of this type of materials have drawn more and more attentions. A variety of fracture theories and models have been developed. Among them, the linear elastic fracture mechanics (LEFM) and cohesive-zone model (CZM) are two widely-accepted fracture models, which have already shown applicability in the fracture analysis of fiber-reinforced composite laminates. However, there remain challenges which prevent further applications of the two fracture models, such as the experimental measurement of fracture resistance. This dissertation primarily focused on the study of the applicability of LEFM and CZM for the fracture analysis of translaminar fracture in fibre-reinforced composite laminates. The research for each fracture model consisted of two sections: the analytical characterization of crack-tip fields and the experimental measurement of fracture resistance parameters. In the study of LEFM, an experimental investigation based on full-field crack-tip displacement measurements was carried out as a way to characterize the subcritical and steady-state crack advances in translaminar fracture of fiber-reinforced composite laminates. Here, the fiber-reinforced composite laminates were approximated as anisotropic solids. The experimental investigation relied on the LEFM theory with a modification with respect to the material anisotropy. Firstly, the full-field crack-tip displacement fields were measured by Digital Image Correlation (DIC). Then two methods, separately based on the stress intensity approach and the energy approach, were developed to measure the crack-tip field parameters from crack-tip displacement fields. The studied crack-tip field parameters included the stress intensity factor, energy release rate and effective crack length. Moreover, the crack-growth resistance curves (R-curves) were constructed with the measured crack-tip field parameters. In addition, an error analysis was carried out with an emphasis on the influence of out-of-plane rotation of specimen. In the study of CZM, two analytical inverse methods, namely the field projection method (FPM) and the separable nonlinear least-squares method, were developed for the extraction of cohesive fracture properties from crack-tip full-field displacements. Firstly, analytical characterizations of the elastic fields around a crack-tip cohesive zone and the cohesive variables within the cohesive zone were derived in terms of an eigenfunction expansion. Then both of the inverse methods were developed based on the analytical characterization. With the analytical inverse methods, the cohesive-zone law (CZL), cohesive-zone size and position can be inversely computed from the cohesive-crack-tip displacement fields. In the study, comprehensive numerical tests were carried out to investigate the applicability and robustness of two inverse methods. From the numerical tests, it was found that the field projection method was very sensitive to noise and thus had limited applicability in practice. On the other hand, the separable nonlinear least-squares method was found to be more noise-resistant and less ill-conditioned. Subsequently, the applicability of separable nonlinear least-squares method was validated with the same translaminar fracture experiment for the study of LEFM. Eventually, it was found that the experimental measurements of R-curves and CZL showed a great agreement, in both of the fracture energy and the predicted load carrying capability. It thus demonstrated the validity of present research for the translaminar fracture of fiber-reinforced composite laminates.

Irrigation and Fertilization Effects on Nantucket Pine Tip Moth (Lepidoptera: Tortricidae) Damage Levels and Pupal Weight in an Intensively-Managed Pine Plantation

Treesearch

David R. Coyle; John T. Nowak; Christopher J. Fettig

2003-01-01

The widespread application of intensive forest management practices throughout the southeastern U.S. has increased loblolly pine, pinus taeda L., yields and shortened conventional rotation lengths. Fluctuations in Nantucket pine tip moth, Rhyacionia frustrana (Comstock), population density and subsequent damage levels have been...

Hyperspectral imaging for detection of black tip damage in wheat kernels

NASA Astrophysics Data System (ADS)

Delwiche, Stephen R.; Yang, I.-Chang; Kim, Moon S.

2009-05-01

A feasibility study was conducted on the use of hyperspectral imaging to differentiate sound wheat kernels from those with the fungal condition called black point or black tip. Individual kernels of hard red spring wheat were loaded in indented slots on a blackened machined aluminum plate. Damage conditions, determined by official (USDA) inspection, were either sound (no damage) or damaged by the black tip condition alone. Hyperspectral imaging was separately performed under modes of reflectance from white light illumination and fluorescence from UV light (~380 nm) illumination. By cursory inspection of wavelength images, one fluorescence wavelength (531 nm) was selected for image processing and classification analysis. Results indicated that with this one wavelength alone, classification accuracy can be as high as 95% when kernels are oriented with their dorsal side toward the camera. It is suggested that improvement in classification can be made through the inclusion of multiple wavelength images.

Optical fiber micro-displacement sensor using a refractive index modulation window-assisted reflection fiber taper

NASA Astrophysics Data System (ADS)

Bao, Weijia; Qiao, Xueguang; Yin, Xunli; Rong, Qiangzhou; Wang, Ruohui; Yang, Hangzhou

2017-12-01

We demonstrate a compact fiber-optic quasi-Michelson interferometer (QMI) for micro-displacement measurement. The sensor comprises a micro-structure of a reflection taper tip containing a refractive index modification (RIM) as a coupling window over the interface between core and cladding of the fiber. Femtosecond laser-based direct inscription technique is used to achieve this window inscription and to induce large refractive index change. The RIM acts as a window for the strong coupling and recoupling of core-to-cladding modes. As the core and cladding modes are reflected at the taper tip and coupled back to lead-in fiber, a well-defined interference spectrum is achieved. The spectral intensity exhibits a high micro-bending sensitivity of 4 . 94 dB / μm because of the sensitivity to bending of recoupled intensity of cladding modes. In contrast, the spectral wavelength is insensitive to bending but linearly responds to temperature. The simultaneous measurements, including power-referenced for displacement and wavelength-referenced for temperature, were achieved by selective interference dip monitoring.

Fatigue Damage Evaluation of Short Carbon Fiber Reinforced Plastics Based on Phase Information of Thermoelastic Temperature Change.

PubMed

Shiozawa, Daiki; Sakagami, Takahide; Nakamura, Yu; Nonaka, Shinichi; Hamada, Kenichi

2017-12-06

Carbon fiber-reinforced plastic (CFRP) is widely used for structural members of transportation vehicles such as automobile, aircraft, or spacecraft, utilizing its excellent specific strength and specific rigidity in contrast with the metal. Short carbon fiber composite materials are receiving a lot of attentions because of their excellent moldability and productivity, however they show complicated behaviors in fatigue fracture due to the random fibers orientation. In this study, thermoelastic stress analysis (TSA) using an infrared thermography was applied to evaluate fatigue damage in short carbon fiber composites. The distribution of the thermoelastic temperature change was measured during the fatigue test, as well as the phase difference between the thermoelastic temperature change and applied loading signal. Evolution of fatigue damage was detected from the distribution of thermoelastic temperature change according to the thermoelastic damage analysis (TDA) procedure. It was also found that fatigue damage evolution was more clearly detected than before by the newly developed thermoelastic phase damage analysis (TPDA) in which damaged area was emphasized in the differential phase delay images utilizing the property that carbon fiber shows opposite phase thermoelastic temperature change.

Tension fracture of laminates for transport fuselage. Part 2: Large notches

NASA Technical Reports Server (NTRS)

Walker, Tom H.; Ilcewicz, Larry B.; Polland, D. R.; Poe, C. C., Jr.

1993-01-01

Tests were conducted on over 200 center-crack specimens to evaluate: (a) the tension-fracture performance of candidate materials and laminates for commercial fuselage applications; and (b) the accuracy of several failure criteria in predicting response. Crack lengths of up to 12 inches were considered. Other variables included fiber/matrix combination, layup, lamination manufacturing process, and intraply hybridization. Laminates fabricated using the automated tow-placement process provided significantly higher tension-fracture strengths than nominally identical tape laminates. This confirmed earlier findings for other layups, and possibly relates to a reduced stress concentration resulting from a larger scale of repeatable material inhomogeneity in the tow-placed laminates. Changes in material and layup result in a trade-off between small-notch and large-notch strengths. Toughened resins and 0 deg-dominate layups result in higher small-notch strengths but lower large-notch strengths than brittle resins, 90 deg and 45 deg dominated layups, and intraply S2-glass hybrid material forms. Test results indicate that strength-prediction methods that allow for a reduced order singularity of the crack-tip stress field are more successful at predicting failure over a range of notch sizes than those relying on the classical square-root singularity. The order of singularity required to accurately predict large-notch strength from small-notch data was affected by both material and layup. Measured crack-tip strain distributions were generally higher than those predicted using classical methods. Traditional methods of correcting for finite specimen width were found to be lacking, confirming earlier findings with other specimen geometries. Fracture tests of two stiffened panels, identical except for differing materials, with severed central stiffeners resulted in nearly identical damage progression and failure sequences. Strain-softening laws implemented within finite element models appear attractive to account for load redistribution in configured structure due to damage-induced crack tip softening

Adhesive Bubble Removal Method and Apparatus for Fiber Optic Applications

NASA Technical Reports Server (NTRS)

Kolasinski, John R. (Inventor)

2001-01-01

An assembly for supporting a fiber optic termination or connector in a centrifuge and comprising a cylindrical body member having a top portion adapted to receive the ferrule body portion of a fiber optic termination or connector and a bottom portion for receiving a cylindrical piston/sealing unit is presented. The piston portion of the piston/sealing unit includes a compressible tip which is adapted to a butt up against the outer end of the ferrule body portion of the fiber optic termination or connector. A cylindrical end cap fits over the upper end of the body member for holding the fiber optic termination in place on the body member and causing a seal to be formed between the termination or connector and the upper portion of the body member adjacent the compressible tip of the plunger. The parts, when fitted together, are placed in a centrifuge which is operated for a predetermined spin cycle, so as to cause any bubbles in the uncured liquid adhesive to be vented outwardly from the termination through the end cap. Subsequent removal of the fiber optic termination or connector from the centrifuge and assembly is "bubble free" and ready to be joined with an optical fiber which is inserted in the ferrule end of the termination or connector.

Adhesive bubble removal method and apparatus for fiber applications

NASA Technical Reports Server (NTRS)

Kolasinski, John R. (Inventor)

2005-01-01

An assembly for supporting a fiber optic termination or connector in a centrifuge and comprising a cylindrical body member having a top portion adapted to receive the ferrule body portion of a fiber optic termination or connector and a bottom portion for receiving a cylindrical piston/sealing unit. The piston portion of the piston/sealing unit includes a compressible tip which is adapted to a butt up against the outer end of the ferrule body portion of the fiber optic termination or connector. A cylindrical end cap fits over the upper end of the body member for holding the fiber optic termination in place on the body member and causing a seal to be formed between the termination or connector and the upper portion of the body member adjacent the compressible tip of the plunger. The parts, when fitted together, are placed in a centrifuge which is operated for a predetermined spin cycle, so as to cause any bubbles in the uncured liquid adhesive to be vented outwardly from the termination through the end cap. Subsequent removal of the fiber optic termination or connector from the centrifuge and assembly is bubble free and ready to be joined with an optical fiber which is inserted in the ferrule end of the termination or connector.

Update on lasers in urology 2014: current assessment on holmium:yttrium-aluminum-garnet (Ho:YAG) laser lithotripter settings and laser fibers.

PubMed

Kronenberg, Peter; Traxer, Olivier

2015-04-01

The purpose of the study was to review the existing literature on holmium:yttrium-aluminum-garnet laser lithotripsy regarding lithotripter settings and laser fibers. An online search of current and past peer-reviewed literature on holmium laser lithotripsy was performed on several databases, including PubMed, SciElo, and Google Scholar. Relevant studies and original articles about lithotripter settings and laser fibers were examined, and the most important information is summarized and presented here. We examine how the choice of lithotripter settings and laser fibers influences the performance of holmium laser lithotripsy. Traditional laser lithotripter settings are analyzed, including pulse energy, pulse frequency, and power levels, as well as newly developed long-pulse modes. The impact of these settings on ablation volume, fragment size, and retropulsion is also examined. Advantages of small- and large-diameter laser fibers are discussed, and controversies are highlighted. Additionally, the influence of the laser fiber is examined, specifically the fiber tip preparation and the lithotripter settings' influence on tip degradation. Many technical factors influence the performance of holmium laser lithotripsy. Knowing and understanding these controllable parameters allows the urologist to perform a laser lithotripsy procedure safely, efficiently, and with few complications.

Infrared glass fiber cables for CO laser medical applications

NASA Astrophysics Data System (ADS)

Arai, Tsunenori; Mizuno, Kyoichi; Sensaki, Koji; Kikuchi, Makoto; Watanabe, Tamishige; Utsumi, Atsushi; Takeuchi, Kiyoshi; Akai, Yoshiro

1993-05-01

We developed the medical fiber cables which were designed for CO laser therapy, i.e., angioplasty and endoscopic therapy. As-S chalcogenide glass fibers were used for CO laser delivery. A 230 micrometers core-diameter fiber was used for the angioplasty laser cable. The outer diameter of this cable was 600 micrometers . The total length and insertion length of the angioplasty laser cable were 2.5 m and 1.0 m, respectively. Typically, 2.0 W of fiber output was used in the animal experiment in vivo for the ablation of the model plaque which consisted of human atheromatous aorta wall. The transmission of the angioplasty laser cable was approximately 35%, because the reflection loss occurred at both ends of the fiber and window. Meanwhile, the core diameter of the energy delivery fiber for the endoscopic therapy was 450 micrometers . The outer diameter of this cable was 1.7 mm. Approximately 4.5 W of fiber output was used for clinical treatment of pneumothorax through a pneumoscope. Both types of the cables had the ultra-thin thermocouples for temperature monitoring at the tip of the cables. This temperature monitoring was extremely useful to prevent the thermal destruction of the fiber tip. Moreover, the As-S glass fibers were completely sealed by the CaF2 windows and outer tubes. Therefore, these cables were considered to have sufficient safety properties for medical applications. These laser cables were successfully used for the in vivo animal experiments and/or actual clinical therapies.

Characteristics of Nd:YAG sculptured contact probes after prolonged laser application.

PubMed

Barroso, E G; Haklin, M F; Staren, E D

1995-01-01

This study analyzed the functional and structural characteristics of cone, hemisphere, and modified sculptured contact fibers (1,000 microns) after 1 hour of continuous Nd:YAG laser application. Continuous laser application was performed on live porcine tissue using 20 watts of power. The fiber's appearance under a microscope as well as the power output was recorded after 0, 5, 10, 20, 30, 45, and 60 minutes of continuous laser application. (N = 3 for each fiber). At time 0, all fibers transmitted from 49 to 56% of the initial 20 watts (W); power transmission decreased to less than 9% relative power transmission after 20 minutes and then plateaued. The fibers exhibited severe distortion and carbonization of the surface where laser had been applied with evidence of quartz melting and shattering after only 10 minutes. By 30 minutes of laser application, all three fibers were fractured and essentially indistinguishable from one another; moreover, the fibers exhibited similar power transmission, and cutting and coagulation activity, as determined by a panel of independent, double-blinded surgeons. These data lead us to conclude that 1) Nd:YAG contact laser effects result from thermal heating of the fiber tip with subsequent tissue injury, 2) the unique structural configuration of the fiber's sculptured tip are lost after several minutes of laser application without appreciable change in functional integrity, and 3) fibers may be manually fractured allowing for multiple uses without significant sacrifice of power transmission or surgical utility.

Impurity-doped optical shock, detonation and damage location sensor

DOEpatents

Weiss, J.D.

1995-02-07

A shock, detonation, and damage location sensor providing continuous fiber-optic means of measuring shock speed and damage location, and could be designed through proper cabling to have virtually any desired crush pressure. The sensor has one or a plurality of parallel multimode optical fibers, or a singlemode fiber core, surrounded by an elongated cladding, doped along their entire length with impurities to fluoresce in response to light at a different wavelength entering one end of the fiber(s). The length of a fiber would be continuously shorted as it is progressively destroyed by a shock wave traveling parallel to its axis. The resulting backscattered and shifted light would eventually enter a detector and be converted into a proportional electrical signals which would be evaluated to determine shock velocity and damage location. The corresponding reduction in output, because of the shortening of the optical fibers, is used as it is received to determine the velocity and position of the shock front as a function of time. As a damage location sensor the sensor fiber cracks along with the structure to which it is mounted. The size of the resulting drop in detector output is indicative of the location of the crack. 8 figs.

Impurity-doped optical shock, detonation and damage location sensor

DOEpatents

Weiss, Jonathan D.

1995-01-01

A shock, detonation, and damage location sensor providing continuous fiber-optic means of measuring shock speed and damage location, and could be designed through proper cabling to have virtually any desired crush pressure. The sensor has one or a plurality of parallel multimode optical fibers, or a singlemode fiber core, surrounded by an elongated cladding, doped along their entire length with impurities to fluoresce in response to light at a different wavelength entering one end of the fiber(s). The length of a fiber would be continuously shorted as it is progressively destroyed by a shock wave traveling parallel to its axis. The resulting backscattered and shifted light would eventually enter a detector and be converted into a proportional electrical signals which would be evaluated to determine shock velocity and damage location. The corresponding reduction in output, because of the shortening of the optical fibers, is used as it is received to determine the velocity and position of the shock front as a function of time. As a damage location sensor the sensor fiber cracks along with the structure to which it is mounted. The size of the resulting drop in detector output is indicative of the location of the crack.

On mechanical mechanism of damage evolution in articular cartilage.

PubMed

Men, Yu-Tao; Jiang, Yan-Long; Chen, Ling; Zhang, Chun-Qiu; Ye, Jin-Duo

2017-09-01

Superficial lesions of cartilage are the direct indication of osteoarthritis. To investigate the mechanical mechanism of cartilage with micro-defect under external loading, a new plain strain numerical model with micro-defect was proposed and damage evolution progression in cartilage over time has been simulated, the parameter were studied including load style, velocity of load and degree of damage. The new model consists of the hierarchical structure of cartilage and depth-dependent arched fibers. The numerical results have shown that not only damage of the cartilage altered the distribution of the stress but also matrix and fiber had distinct roles in affecting cartilage damage, and damage in either matrix or fiber could promote each other. It has been found that the superficial cracks in cartilage spread preferentially along the tangent direction of the fibers. It is the arched distribution form of fibers that affects the crack spread of cartilage, which has been verified by experiment. During the process of damage evolution, its extension direction and velocity varied constantly with the damage degree. The rolling load could cause larger stress and strain than sliding load. Strain values of the matrix initially increased and then decreased gradually with the increase of velocity, and velocity had a greater effect on matrix than fibers. Damage increased steadily before reaching 50%, sharply within 50 to 85%, and smoothly and slowly after 85%. The finding of the paper may help to understand the mechanical mechanism why the cracks in cartilage spread preferentially along the tangent direction of the fibers. Copyright © 2017 Elsevier B.V. All rights reserved.

Amperometric Carbon Fiber Nitrite Microsensor for In Situ Biofilm Monitoring

EPA Science Inventory

A highly selective needle type solid state amperometric nitrite microsensor based on direct nitrite oxidation on carbon fiber was developed using a simplified fabrication method. The microsensor’s tip diameter was approximately 7 µm, providing a high spatial resolution of at lea...

Improvement of optical damage in specialty fiber at 266 nm wavelength

NASA Astrophysics Data System (ADS)

Tobisch, T.; Ohlmeyer, H.; Zimmermann, H.; Prein, S.; Kirchhof, J.; Unger, S.; Belz, M.; Klein, K.-F.

2014-02-01

Improved multimode UV-fibers with core diameters ranging from 70 to 600 μm diameter have been manufactured based on novel preform modifications and fiber processing techniques. Only E'-centers at 214 nm and NBOHC at 260 nm are generated in these fibers. A new generation of inexpensive laser-systems have entered the market and generated a multitude of new and attractive applications in the bio-life science, chemical and material processing field. However, for example pulsed 355 nm Nd:YAG lasers generate significant UV-damages in commercially available fibers. For lower wavelengths, no results on suitable multi-mode or low-mode fibers with high UV resistance at 266 nm wavelength (pulsed 4th harmonic Nd:YAG laser) have been published. In this report, double-clad fibers with 70 μm or 100 μm core diameter and a large claddingto- core ratio will be recommended. Laser-induced UV-damages will be compared between these new fiber type and traditional UV fibers with similar core sizes. Finally, experimental results will be cross compared against broadband cw deuterium lamp damage standards.

Stress transfer around a broken fiber in unidirectional fiber-reinforced composites considering matrix damage evolution and interface slipping

NASA Astrophysics Data System (ADS)

Yang, Zhong; Zhang, BoMing; Zhao, Lin; Sun, XinYang

2011-02-01

A shear-lag model is applied to study the stress transfer around a broken fiber within unidirectional fiber-reinforced composites (FRC) subjected to uniaxial tensile loading along the fiber direction. The matrix damage and interfacial debonding, which are the main failure modes, are considered in the model. The maximum stress criterion with the linear damage evolution theory is used for the matrix. The slipping friction stress is considered in the interfacial debonding region using Coulomb friction theory, in which interfacial clamping stress comes from radial residual stress and mismatch of Poisson's ratios of constituents (fiber and matrix). The stress distributions in the fiber and matrix are obtained by the shear-lag theory added with boundary conditions, which includes force continuity and displacement compatibility constraints in the broken and neighboring intact fibers. The result gives axial stress distribution in fibers and shear stress in the interface and compares the theory reasonably well with the measurement by a polarized light microscope. The relation curves between damage, debonding and ineffective region lengths with external strain loading are obtained.

Micromechanical Analysis of Crack Closure Mechanism for Intelligent Material Containing TiNi Fibers

NASA Astrophysics Data System (ADS)

Araki, Shigetoshi; Ono, Hiroyuki; Saito, Kenji

In our previous study, the micromechanical modeling of an intelligent material containing TiNi fibers was performed and the stress intensity factor KI at the tip of the crack in the material was expressed in terms of the magnitude of the shape memory shrinkage of the fibers and the thermal expansion strain in the material. In this study, the value of KI at the tip of the crack in the TiNi/epoxy material is calculated numerically by using analytical expressions obtained in our first report. As a result, we find that the KI value decreases with increasing shrink strain of the fibers, and this tendency agrees with that of the experimental result obtained by Shimamoto etal.(Trans. Jpn. Soc. Mech. Eng., Vol. 65, No. 634 (1999), pp. 1282-1286). Moreover, there exists an optimal value of the shrink strain of the fibers to make the KI value zero. The change in KI with temperature during the heating process from the reference temperature to the inverse austenitic finishing temperature of TiNi fiber is also consistent with the experimental result. These results can be explained by the changes in the shrink strain, the thermal expansion strain, and the elastic moduli of TiNi fiber with temperature. These results may be useful in designing intelligent materials containing TiNi fibers from the viewpoint of crack closure.

Holmium: YAG laser-induced liquid jet knife: possible novel method for dissection.

PubMed

Nakagawa, Atsuhiro; Hirano, Takayuki; Komatsu, Makoto; Sato, Mariko; Uenohara, Hiroshi; Ohyama, Hideki; Kusaka, Yasuko; Shirane, Reizo; Takayama, Kazuyoshi; Yoshimoto, Takashi

2002-01-01

Making surgical incisions in vessel-rich organs without causing bleeding is difficult. Thus, it is necessary to develop new devices for this purpose, especially for surgery involving small vessels as in neurosurgery, where damage against even small cerebral vessels result in severe neurological deficits. A laser-induced liquid jet was generated by irradiating pulsed Holmium Yttrium-Aluminum-Garnet (Ho: YAG) laser (beams of 350 microseconds pulse width) within a copper tube (internal diameter, 1 mm) with pure water (150 ml /hour). Ho: YAG laser beams were irradiated through an optical fiber (core diameter, 0.4 mm). The influence of the input of laser energy, structure of the nozzle, and the stand-off distance between the optical fiber tip and nozzle exit on the jet velocity was measured by a high-speed video camera to evaluate controllability of jet. The effect on artificial organs made of 10 and 30%(w/v) gelatin, each of which represent features of soft tissue and blood vessels. Jet velocity increased in proportion to gain in laser energy input, and maximum penetration depth into 10%(w/v) gelatin was 35 mm by single exposure at 350 mJ/pulse without impairing a vessel model. Shapes of nozzle also modified jet velocity with optimal nozzle/tube area ratio of 0.25. The laser-induced liquid jet has excellent potential as a new tool for removing soft tissue without damaging vital structures. Copyright 2002 Wiley-Liss, Inc.

In-plane ultrasonic needle tracking using a fiber-optic hydrophone

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

Xia, Wenfeng, E-mail: wenfeng.xia@ucl.ac.uk; Desjardins, Adrien E.; Mari, Jean Martial

Purpose: Accurate and efficient guidance of needles to procedural targets is critically important during percutaneous interventional procedures. Ultrasound imaging is widely used for real-time image guidance in a variety of clinical contexts, but with this modality, uncertainties about the location of the needle tip within the image plane lead to significant complications. Whilst several methods have been proposed to improve the visibility of the needle, achieving accuracy and compatibility with current clinical practice is an ongoing challenge. In this paper, the authors present a method for directly visualizing the needle tip using an integrated fiber-optic ultrasound receiver in conjunction withmore » the imaging probe used to acquire B-mode ultrasound images. Methods: Needle visualization and ultrasound imaging were performed with a clinical ultrasound imaging system. A miniature fiber-optic ultrasound hydrophone was integrated into a 20 gauge injection needle tip to receive transmissions from individual transducer elements of the ultrasound imaging probe. The received signals were reconstructed to create an image of the needle tip. Ultrasound B-mode imaging was interleaved with needle tip imaging. A first set of measurements was acquired in water and tissue ex vivo with a wide range of insertion angles (15°–68°) to study the accuracy and sensitivity of the tracking method. A second set was acquired in an in vivo swine model, with needle insertions to the brachial plexus. A third set was acquired in an in vivo ovine model for fetal interventions, with insertions to different locations within the uterine cavity. Two linear ultrasound imaging probes were used: a 14–5 MHz probe for the first and second sets, and a 9–4 MHz probe for the third. Results: During insertions in tissue ex vivo and in vivo, the imaged needle tip had submillimeter axial and lateral dimensions. The signal-to-noise (SNR) of the needle tip was found to depend on the insertion angle. With the needle tip in water, the SNR of the needle tip varied with insertion angle, attaining values of 284 at 27° and 501 at 68°. In swine tissue ex vivo, the SNR decreased from 80 at 15° to 16 at 61°. In swine tissue in vivo, the SNR varied with depth, from 200 at 17.5 mm to 48 at 26 mm, with a constant insertion angle of 40°. In ovine tissue in vivo, within the uterine cavity, the SNR varied from 46.4 at 25 mm depth to 18.4 at 32 mm depth, with insertion angles in the range of 26°–65°. Conclusions: A fiber-optic ultrasound receiver integrated into the needle cannula in combination with single-element transmissions from the imaging probe allows for direct visualization of the needle tip within the ultrasound imaging plane. Visualization of the needle tip was achieved at depths and insertion angles that are encountered during nerve blocks and fetal interventions. The method presented in this paper has strong potential to improve the safety and efficiency of ultrasound-guided needle insertions.« less

Susceptibility of parent and interspecific Fl hybrid pine trees to tip moth damage in a coastal North Carolina planting

Treesearch

Maxine T. Highsmith; John Frampton; David 0' Malley; James Richmond; Martesa Webb

2001-01-01

Tip moth damage arnong families of parent pine species and their interspecific F1 hybrids was quantitatively assessed in a coastal planting in North Carolina. Three slash pine (Pinus elliotti var. elliotti Engelm.), two loblolly pine (Pinus taeda L.), and four interspecific F1 hybrid pine families were used. The...

Optically resilient 3D micro-optics on the tips of optical fibers

NASA Astrophysics Data System (ADS)

Jonušauskas, Linas

2017-05-01

In this paper we present a study aimed at investigating an optical resiliency of polymers that could be applied in 3D femtosecond laser lithography. These include popular in lithography SU8 and OrmoClear as well as hybrid organic-inorganic zirconium containing SZ2080. We show that latter material in its pure (non-photosensitized) form has the best optical resiliency out of all tested materials. Furthermore, its 3D structurability is investigated. Despite threshold-like quality degradation outside fabrication window, we show that this material is suitable for creating complex 3D structures on the tips of optical fibers. Overall it is demonstrated, that unique capability of 3DLL to structure pure materials can lead to very compact functional fiber-based devices that could withstand high (GW/cm2) light intensities.

Engine spectrometer probe and method of use

NASA Technical Reports Server (NTRS)

Barkhoudarian, Sarkis (Inventor); Kittinger, Scott A. (Inventor)

2006-01-01

The engine spectrometer probe and method of using the same of the present invention provides a simple engine spectrometer probe which is both lightweight and rugged, allowing an exhaust plume monitoring system to be attached to a vehicle, such as the space shuttle. The engine spectrometer probe can be mounted to limit exposure to the heat and debris of the exhaust plume. The spectrometer probe 50 comprises a housing 52 having an aperture 55 and a fiber optic cable 60 having a fiber optic tip 65. The fiber optic tip 65 has an acceptance angle 87 and is coupled to the aperture 55 so that the acceptance angle 87 intersects the exhaust plume 30. The spectrometer probe can generate a spectrum signal from light in the acceptance angle 506 and the spectrum signal can be provided to a spectrometer 508.

NOTCH1 Inhibits Activation of ATM by Impairing the Formation of an ATM-FOXO3a-KAT5/Tip60 Complex.

PubMed

Adamowicz, Marek; Vermezovic, Jelena; d'Adda di Fagagna, Fabrizio

2016-08-23

The DNA damage response (DDR) signal transduction pathway is responsible for sensing DNA damage and further relaying this signal into the cell. ATM is an apical DDR kinase that orchestrates the activation and the recruitment of downstream DDR factors to induce cell-cycle arrest and repair. We have previously shown that NOTCH1 inhibits ATM activation upon DNA damage, but the underlying mechanism remains unclear. Here, we show that NOTCH1 does not impair ATM recruitment to DNA double-strand breaks (DSBs). Rather, NOTCH1 prevents binding of FOXO3a and KAT5/Tip60 to ATM through a mechanism in which NOTCH1 competes with FOXO3a for ATM binding. Lack of FOXO3a binding to ATM leads to the loss of KAT5/Tip60 association with ATM. Moreover, expression of NOTCH1 or depletion of ATM impairs the formation of the FOXO3a-KAT5/Tip60 protein complex. Finally, we show that pharmacological induction of FOXO3a nuclear localization sensitizes NOTCH1-driven cancers to DNA-damage-induced cell death. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Fiber composite fan blade impact improvement

NASA Technical Reports Server (NTRS)

Graff, J.; Stoltze, L.; Varholak, E. M.

1976-01-01

The improved foreign object damage resistance of a metal matrix advanced composite fan blade was demonstrated. The fabrication, whirl impact test and subsequent evaluation of nine advanced composite fan blades of the "QCSEE" type design were performed. The blades were designed to operate at a tip speed of 282 m/sec. The blade design was the spar/shell type, consisting of a titanium spar and boron/aluminum composite airfoils. The blade retention was designed to rock on impact with large birds, thereby reducing the blade bending stresses. The program demonstrated the ability of the blades to sustain impacts with up to 681 g slices of birds at 0.38 rad with little damage (only 1.4 percent max weight loss) and 788 g slices of birds at 0.56 rad with only 3.2 percent max weight loss. Unbonding did not exceed 1.1 percent of the post-test blade area during any of the tests. All blades in the post-test condition were judged capable of operation in accordance with the FAA guidelines for medium and large bird impacts.

General Tips of What Little This Author has Learned of Cotton Processing in Traditional Textile Manufacturing

USDA-ARS?s Scientific Manuscript database

This article, under the following sub-headings, only lists a few very important tips that the author has experienced in his career involving processing of cotton in the traditional textile manufacturing: (1) Fiber Opening and Cleaning (2) Carding (3) Drawing (4) Combing, if necessary (5) Roving (6)...

Characterization of laser-driven shock waves in solids using a fiber optic pressure probe.

PubMed

Cranch, Geoffrey A; Lunsford, Robert; Grün, Jacob; Weaver, James; Compton, Steve; May, Mark; Kostinski, Natalie

2013-11-10

Measurement of laser-driven shock wave pressure in solid blocks of polymethyl methacrylate is demonstrated using fiber optic pressure probes. Three probes based on a fiber Fabry-Perot, fiber Bragg grating, and interferometric fiber tip sensor are tested and compared. Shock waves are generated using a high-power laser focused onto a thin foil target placed in close proximity to the test blocks. The fiber Fabry-Perot sensor appears capable of resolving the shock front with a rise time of 91 ns. The peak pressure is estimated, using a separate shadowgraphy measurement, to be 3.4 GPa.

The potential for trichogramma releases to suppress tip moth populations in pine plantations

Treesearch

David B. Orr; Charles P.-C Suh; Michael Philip; Kenneth W. McCravy; Gary L. DeBarr

1999-01-01

Because the Nantucket pine tip moth is a native pest, augmentation (mass-release) of native natural enemies may be the most promising method of tip moth biocontrol. The tip moth has several important egg, larval, and pupal parasitoids. Egg parasitoids are most effective as biocontrol agents because they eliminate the host before it reaches a damaging stage....

Experimental Verification of Computational Models for Laminated Composites

NASA Technical Reports Server (NTRS)

Harris, Charles E.; Coats, Timothy W.; Glaessgen, Edward H.

1999-01-01

The objective of the research reported herein is to develop a progressive damage methodology capable of predicting the residual strength of continuous fiber-reinforced, laminated, polymer matrix composites with through-penetration damage. The fracture behavior of center-notch tension panels with thin crack-like slits was studied. Since fibers are the major load-carrying constituent in polymer matrix composites, predicting the residual strength of a laminate requires a criterion for fiber fracture. The effects on fiber strain due to other damage mechanisms such as matrix cracking and delaminations must also be modeled. Therefore, the research herein examines the damage mechanisms involved in translaminate fracture and identifies the toughening mechanisms responsible for damage growth resistance in brittle epoxy matrix systems. The mechanics of matrix cracking and fiber fracture are discussed as is the mathematical framework for the progressive damage model developed by the authors. The progressive damage analysis algorithms have been implemented into a general purpose finite element code developed by NASA, the Computational Structural Mechanics Testbed (COMET). Damage growth is numerically simulated and the analytical residual strength predictions are compared to experimental results for a variety of notched panel configurations and materials systems.

On-demand drawing of high aspect-ratio, microsphere-tipped elastomeric micropillars

NASA Astrophysics Data System (ADS)

Li, Qiang; Kim, Jaeyoun

2017-08-01

High aspect-ratio elastomeric micropillars are widely used in a plethora of applications, such as functional surfaces, actuators, and sensors. Their fabrication at arbitrary positions on non-planar substrates, however, has rarely been reported. Here we demonstrate a new technique for facile fabrication of high aspect-ratio, microsphere-tipped elastomeric micropillars on structures with uncommon geometries. As a proof-of-concept exemplary application, a fiber optic contact sensor is realized by integrating a micropillar onto the end facet of an optical fiber. Overall, both the fabrication technique and the resulting outcomes of this work will add new tools to the toolbox of soft-MEMS and softrobotics.

Miniature ureteroscope tip designs for use in thulium fiber laser lithotripsy

NASA Astrophysics Data System (ADS)

Kennedy, Joshua D.; Wilson, Christopher R.; Irby, Pierce B.; Fried, Nathaniel M.

2017-02-01

A miniature ureteroscope has the potential to eliminate need for full anesthesia and dilation, increase comfort and safety of laser lithotripsy via ureteroscopy, and reduce hospital costs via an office based procedure. A prototype, 4.5 Fr (1.5-mm-OD), five channel ureteroscope tip was developed, housing a 200-μm-ID central channel for insertion of small, 100-μm-core fibers and four surrounding channels, each with 510-μm-ID for instrumentation, irrigation, imaging, and illumination, respectively. Common urological instruments (including fibers, guidewires, and stone baskets) were inserted through tip's working channels to demonstrate feasibility. Low irrigation rates were measured, revealing a need for manual pump-assisted irrigation. Imaging was conducted using 3k, 6k, and 10k pixel miniature flexible endoscopes with 0.4, 0.6, and 0.9 mm outer diameters, respectively. The 3k pixel endoscope with integrated illumination was inserted through the prototype unimpeded, and successfully demonstrated ability to differentiate between hard tissues (e.g. kidney stones) and soft tissues (e.g. ureter wall), for visibility and safety during potential clinical application. Based on both image quality and instrument diameter, the 6k pixel endoscope provided an optimal solution for miniature ureteroscopy.

Analysis and Support Initiative for Structural Technology (ASIST) Delivery Order 0016: USAF Damage Tolerant Design Handbook: Guidelines For the Analysis and Design of Damage Tolerant Aircraft Structures

DTIC Science & Technology

2002-11-01

hand crack tip (point B) and with angular displacement from the x-axis. As the stress element is moved closer to the crack tip, the stresses are...on the methods of obtaining the required relationships are presented by Broek [1974]. The necessary relationships for Vσ, VF, Vp and Vst ...4.5.18. Geometrical and Displacement Parameters Relative to the Crack Tip 4.5.21 Vσ + VF + Vp = Vst (4.5.15) substituting the expressions 4.5.6

Monitoring of temperature fatigue failure mechanism for polyvinyl alcohol fiber concrete using acoustic emission sensors.

PubMed

Li, Dongsheng; Cao, Hai

2012-01-01

The applicability of acoustic emission (AE) techniques to monitor the mechanism of evolution of polyvinyl alcohol (PVA) fiber concrete damage under temperature fatigue loading is investigated. Using the temperature fatigue test, real-time AE monitoring data of PVA fiber concrete is achieved. Based on the AE signal characteristics of the whole test process and comparison of AE signals of PVA fiber concretes with different fiber contents, the damage evolution process of PVA fiber concrete is analyzed. Finally, a qualitative evaluation of the damage degree is obtained using the kurtosis index and b-value of AE characteristic parameters. The results obtained using both methods are discussed.

Monitoring of Temperature Fatigue Failure Mechanism for Polyvinyl Alcohol Fiber Concrete Using Acoustic Emission Sensors

PubMed Central

Li, Dongsheng; Cao, Hai

2012-01-01

The applicability of acoustic emission (AE) techniques to monitor the mechanism of evolution of polyvinyl alcohol (PVA) fiber concrete damage under temperature fatigue loading is investigated. Using the temperature fatigue test, real-time AE monitoring data of PVA fiber concrete is achieved. Based on the AE signal characteristics of the whole test process and comparison of AE signals of PVA fiber concretes with different fiber contents, the damage evolution process of PVA fiber concrete is analyzed. Finally, a qualitative evaluation of the damage degree is obtained using the kurtosis index and b-value of AE characteristic parameters. The results obtained using both methods are discussed. PMID:23012555

High Power Spark Delivery System Using Hollow Core Kagome Lattice Fibers

PubMed Central

Dumitrache, Ciprian; Rath, Jordan; Yalin, Azer P.

2014-01-01

This study examines the use of the recently developed hollow core kagome lattice fibers for delivery of high power laser pulses. Compared to other photonic crystal fibers (PCFs), the hollow core kagome fibers have larger core diameter (~50 µm), which allows for higher energy coupling in the fiber while also maintaining high beam quality at the output (M2 = 1.25). We have conducted a study of the maximum deliverable energy versus laser pulse duration using a Nd:YAG laser at 1064 nm. Pulse energies as high as 30 mJ were transmitted for 30 ns pulse durations. This represents, to our knowledge; the highest laser pulse energy delivered using PCFs. Two fiber damage mechanisms were identified as damage at the fiber input and damage within the bulk of the fiber. Finally, we have demonstrated fiber delivered laser ignition on a single-cylinder gasoline direct injection engine. PMID:28788155

Seismic damage identification for steel structures using distributed fiber optics.

PubMed

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

2009-08-01

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

Research on Damage Models for Continuous Fiber Composites

DTIC Science & Technology

1988-07-01

r ~.F (~ Mechanics and Materials Center TEXAS A&M UNIVERSITY College Station, Texas RESEARCH ON DAMAGE MODELS FOR CONTINUOUS FIBER COMPOSITES Final...Washington, DC 20332 11. TITLE (Include Security Clas=fication) Research on Damage Models for Continuous Fiber Composites - Final Technical Report 1...GROUP SUB-GROU ::=, COMPOsites ) continuum mechanics , ~ idamage, internal state variables V experimental mechanics, laminated composites o 19. ABSTRACT

A methodology to predict damage initiation, damage growth and residual strength in titanium matrix composites

NASA Technical Reports Server (NTRS)

Bakuckas, J. G., Jr.; Johnson, W. S.

1994-01-01

In this research, a methodology to predict damage initiation, damage growth, fatigue life, and residual strength in titanium matrix composites (TMC) is outlined. Emphasis was placed on micromechanics-based engineering approaches. Damage initiation was predicted using a local effective strain approach. A finite element analysis verified the prevailing assumptions made in the formulation of this model. Damage growth, namely, fiber-bridged matrix crack growth, was evaluated using a fiber bridging (FB) model which accounts for thermal residual stresses. This model combines continuum fracture mechanics and micromechanics analyses yielding stress-intensity factor solutions for fiber-bridged matrix cracks. It is assumed in the FB model that fibers in the wake of the matrix crack are idealized as a closure pressure, and an unknown constant frictional shear stress is assumed to act along the debond length of the bridging fibers. This frictional shear stress was used as a curve fitting parameter to the available experimental data. Fatigue life and post-fatigue residual strength were predicted based on the axial stress in the first intact 0 degree fiber calculated using the FB model and a three-dimensional finite element analysis.

Characteristics of Pool Boiling on Graphite-Copper Composite Surfaces

NASA Technical Reports Server (NTRS)

Zhang, Nengli; Chao, David F.; Yang, Wen-Jei

2002-01-01

Nucleate pool boiling performance of different liquids on graphite-copper composite (Gr-Cu) surfaces has been experimentally studied and modeled. Both highly wetting fluids, such as freon-113 and pentane, and a moderately wetting fluid (water) were tested on the Gr-Cu surfaces with different graphite-fiber volume fractions to reveal the enhancement effects of the composite surfaces on the nucleate pool boiling. Results of the experiments show that the graphite-fiber volume fraction has an optimum value. The Gr-Cu composite surface with 25 percent graphite-fiber volume (f=0.25) has a maximum enhancement effect on the nucleate boiling heat transfer comparing to the pure copper surface. For the highly wetting fluid, the nucleate boiling heat transfer is generally enhanced on the Gr- Cu composite surfaces by 3 to 6 times shown. In the low heat flux region, the enhancement is over 6 times, but in the high heat flux region, the enhancement is reduced to about 40%. For the moderately wetting fluid (water), stronger enhancement of nucleate boiling heat transfer is achieved on the composite surface. It shown the experimental results in which one observes the nucleate boiling heat transfer enhancement of 5 to 10 times in the low heat flux region and an enhancement of 3 to 5 times in the high heat flux region. Photographs of bubble departure during the initial stage of nucleate boiling indicate that the bubbles detached from the composite surface are much smaller in diameter than those detached from the pure copper surface. Typical photographs are presented.It shows that the bubbles departed from the composite surface have diameters of only O(0.1) mm, while those departed from the pure copper surface have diameters of O(1) mm. It is also found that the bubbles depart from the composite surface at a much higher frequency, thus forming vapor columns. These two phenomena combined with high thermal conductivity of the graphite fiber are considered the mechanisms for such a significant augmentation in nucleate boiling heat transfer on the composite surfaces. A physical model is developed to describe the phenomenon of bubble departure from the composite surface: The preferred site of bubble nucleation is the fiber tip because of higher tip temperature than the surrounding copper base and poor wettability of the graphite tip compared with that of the base material (copper). The high evaporation rate near the contact line produces the vapor cutback due to the vapor recoil pushing the three-phase line outwards from the fiber tip, and so a neck of the bubble is formed near the bubble bottom. Evaporation and surface tension accelerate the necking process and finally result in the bubble departure while a new small bubble is formed at the tip when the surface tension pushes the three-phase line back to the tip. The process is schematically shown. The proposed model is based on and confirmed by experimental results.

Impact resistance of composite fan blades

NASA Technical Reports Server (NTRS)

1974-01-01

Results are presented of a program to determine the impact resistance of composite fan blades subjected to foreign object damage (FOD) while operating under conditions simulating a short take-off and landing (STOL) engine at takeoff. The full-scale TF39 first-stage fan blade was chosen as the base design for the demonstration component since its configuration and operating tip speeds are similar to a typical STOL fan blade several composite configurations had already been designed and evaluated under previous programs. The first portion of the program was devoted toward fabricating and testing high impact resistant, aerodynamically acceptable composite blades which utilized only a single material system in any given blade. In order to increase the blade impact capability beyond this point, several mixed material (hybrid) designs were investigated using S-glass and Kevlar as well as boron and graphite fibers. These hybrid composite blades showed a marked improvement in resistance to bird impact over those blades made of a single composite material. The work conducted under this program has demonstrated substantial improvement in composite fan blades with respect to FOD resistance and has indicated that the hybrid design concept, which utilizes different types of fibers in various portions of a fan blade design depending on the particular requirements of the different areas and the characteristics of the different fibers involved, shows a significant improvement over those designs utilizing only one material system.

Evaluation of long carbon fiber reinforced concrete to mitigate earthquake damage of infrastructure components.

DOT National Transportation Integrated Search

2013-06-01

The proposed study involves investigating long carbon fiber reinforced concrete as a method of mitigating earthquake damage to : bridges and other infrastructure components. Long carbon fiber reinforced concrete has demonstrated significant resistanc...

Southwestern Pine Tip Moth

Treesearch

Daniel T. Jennings; Robert E. Stevens

1982-01-01

The southwestern pine tip moth, Rhyacionia neomexicana (Dyar), injures young ponderosa pines (Pinus ponderosa Dougl. ex Laws) in the Southwest, central Rockies, and midwestern plains. Larvae feed on and destroy new, expanding shoots, often seriously reducing terminal growth of both naturally regenerated and planted pines. The tip moth is especially damaging to trees on...

A Progressive Damage Methodology for Residual Strength Predictions of Center-Crack Tension Composite Panels

NASA Technical Reports Server (NTRS)

Coats, Timothy William

1996-01-01

An investigation of translaminate fracture and a progressive damage methodology was conducted to evaluate and develop a residual strength prediction capability for laminated composites with through penetration notches. This is relevant to the damage tolerance of an aircraft fuselage that might suffer an in-flight accident such as an uncontained engine failure. An experimental characterization of several composite materials systems revealed an R-curve type of behavior. Fractographic examinations led to the postulate that this crack growth resistance could be due to fiber bridging, defined here as fractured fibers of one ply bridged by intact fibers of an adjacent ply. The progressive damage methodology is currently capable of predicting the initiation and growth of matrix cracks and fiber fracture. Using two difference fiber failure criteria, residual strength was predicted for different size panel widths and notch lengths. A ply discount fiber failure criterion yielded extremely conservative results while an elastic-perfectly plastic fiber failure criterion showed that the fiber bridging concept is valid for predicting residual strength for tensile dominated failure loads. Furthermore, the R-curves predicted by the model using the elastic-perfectly plastic fiber criterion compared very well with the experimental R-curves.

Investigating the Mechanisms and Potential of Silk Fiber Metallization

DTIC Science & Technology

2013-09-30

in an ALD process, when using the modified metal infiltration process as outlined by Lee et al., the titanium isopropoxide (TIP) precursor...these fibers exhibited >2-fold increase in strain to breakage, and >4.5-fold increase in strength when infiltrated with zinc, titanium , or aluminum...fibers exhibited >2-fold increase in strain to breakage, and >4.5-fold increase in strength when infiltrated with zinc, titanium , or aluminum

Force deficits and breakage rates after single lengthening contractions of single fast fibers from unconditioned and conditioned muscles of young and old rats.

PubMed

Lynch, Gordon S; Faulkner, John A; Brooks, Susan V

2008-07-01

The deficit in force generation is a measure of the magnitude of damage to sarcomeres caused by lengthening contractions of either single fibers or whole muscles. In addition, permeabilized single fibers may suffer breakages. Our goal was to understand the interaction between breakages and force deficits in "young" and "old" permeabilized single fibers from control muscles of young and old rats and "conditioned" fibers from muscles that completed a 6-wk program of in vivo lengthening contractions. Following single lengthening contractions of old-control fibers compared with young-control fibers, the twofold greater force deficits at a 10% strain support the concept of an age-related increase in the susceptibility of fibers to mechanical damage. In addition, the much higher breakage rates for old fibers at all strains tested indicate an increase with aging in the number of fibers at risk of being severely injured during any given stretch. Following the 6-wk program of lengthening contractions, young-conditioned fibers and old-conditioned fibers were not different with respect to force deficit or the frequency of breakages. A potential mechanism for the increased resistance to stretch-induced damage of old-conditioned fibers is that, through intracellular damage and subsequent degeneration and regeneration, weaker sarcomeres were replaced by stronger sarcomeres. These data indicate that, despite the association of high fiber breakage rates and large force deficits with aging, the detrimental characteristics of old fibers were improved by a conditioning program that altered both sarcomeric characteristics as well as the overall structural integrity of the fibers.

Effects of Carriers, Emulsifiers, and Biopesticides for Direct Silk Treatments on Caterpillar Feeding Damage and Ear Development in Sweet Corn.

PubMed

Westgate, P J; Schultz, B B; Hazzard, R V

2017-04-01

In the northeastern United States, control of Lepidopteran pests of sweet corn, particularly corn earworm [Helicoverpa zea (Boddie)], is difficult using organic methods. The direct application of corn oil and Bacillus thuringiensis (Bt) to corn silk has been shown to reduce ear damage from corn earworm in past studies; these studies sought to optimize this method by evaluating additional carrier and biopesticide mixtures that comply with the United States Federal Insecticide, Fungicide, and Rodenticide Act and National Organic Standards. Carriers, which are liquids used to dissolve the biopesticide and deliver it into the tip of the ear, may have phytotoxic or insecticidal properties. Experiments conducted from 2001 to 2005 evaluated caterpillar damage and ear development effects from carriers (vegetable and paraffinic oils and carrageenan), biopesticides (Bt, spinsosad, and neem), and three emulsifiers in various combinations when applied directly to the tips of the ears 5-7 d after silk initiation. There were no effects of emulsifiers on ear quality, except for slight reduction in caterpillar damage in one of the two years. There were no differences among corn, soy, canola, and safflower oils in corn earworm control or tip development. The carrageenan carrier had the least effect upon ear development as measured by the length of nonpollinated kernels at the tip, compared to corn oil or paraffinic oil (JMS Stylet Oil), which caused the greatest tip damage as well as an oily discoloration. The carrier-pesticide combinations with the best ear quality overall were spinosad in carrageenan or corn oil, and Bt in carrageenan. © The Authors 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Laser pulse power transmission limits of silica fibers with antireflective coating

NASA Astrophysics Data System (ADS)

Meister, St.; Wosniok, A.; Seewald, G.; Scharfenorth, Ch.; Eichler, H. J.

2005-04-01

Multimode optical fibers are used for the transmission of high power laser pulses and as phase conjugated mirrors by stimulated Brillouin scattering. Both applications are enhanced by antireflection coatings on the fiber end-faces. Fiber transmissions reach more than 99.5% for pulse energies below the threshold of stimulated Brillouin scattering. Laser-induced damage thresholds of the fibers coated with Ta2O5 / SiO2 were measured at 1064 nm and 24 ns pulse duration. A damage threshold of up to 101 J/cm2 could be achieved. The damage morphology was investigated using atomic force microscopy and scanning electron microscopy.

Stressed Oxidation of C/SiC Composites

NASA Technical Reports Server (NTRS)

Halbig, Michael C.; Brewer, David N.; Eckel, Andrew J.; Cawley, James D.

1997-01-01

Constant load, stressed oxidation testing was performed on T-300 C/SiC composites with a SiC seal coat. Test conditions included temperatures ranging from 350 C to 1500 C at stresses of 69 MPa and 172 MPa (10 and 25 ksi). The coupon subjected to stressed oxidation at 550 C/69 MPa for 25 hours had a room temperature residual strength one-half that of the as-received coupons. The coupon tested at the higher stress and all coupons tested at higher temperatures failed in less than 25 hr. Microstructural analysis of the fracture surfaces, using SEM (scanning electron microscopy), revealed the formation of reduced cross-sectional fibers with pointed tips. Analysis of composite cross-sections show pathways for oxygen ingress. The discussion will focus on fiber/matrix interphase oxidation and debonding as well as the formation and implications of the fiber tip morphology.

Supercontinuum as a light source for miniaturized endoscopes.

PubMed

Lu, M K; Lin, H Y; Hsieh, C C; Kao, F J

2016-09-01

In this work, we have successfully implemented supercontinuum based illumination through single fiber coupling. The integration of a single fiber illumination with a miniature CMOS sensor forms a very slim and powerful camera module for endoscopic imaging. A set of tests and in vivo animal experiments are conducted accordingly to characterize the corresponding illuminance, spectral profile, intensity distribution, and image quality. The key illumination parameters of the supercontinuum, including color rendering index (CRI: 72%~97%) and correlated color temperature (CCT: 3,100K~5,200K), are modified with external filters and compared with those from a LED light source (CRI~76% & CCT~6,500K). The very high spatial coherence of the supercontinuum allows high luminosity conduction through a single multimode fiber (core size~400μm), whose distal end tip is attached with a diffussion tip to broaden the solid angle of illumination (from less than 10° to more than 80°).

Nanospot soldering polystyrene nanoparticles with an optical fiber probe laser irradiating a metallic AFM probe based on the near-field enhancement effect.

PubMed

Cui, Jianlei; Yang, Lijun; Wang, Yang; Mei, Xuesong; Wang, Wenjun; Hou, Chaojian

2015-02-04

With the development of nanoscience and nanotechnology for the bottom-up nanofabrication of nanostructures formed from polystyrene nanoparticles, joining technology is an essential step in the manufacturing and assembly of nanodevices and nanostructures in order to provide mechanical integration and connection. To study the nanospot welding of polystyrene nanoparticles, we propose a new nanospot-soldering method using the near-field enhancement effect of a metallic atomic force microscope (AFM) probe tip that is irradiated by an optical fiber probe laser. On the basis of our theoretical analysis of the near-field enhancement effect, we set up an experimental system for nanospot soldering; this approach is carried out by using an optical fiber probe laser to irradiate the AFM probe tip to sinter the nanoparticles, providing a promising technical approach for the application of nanosoldering in nanoscience and nanotechnology.

Mismatch Considerations in Excitation of Single-Mode Circular Core Parabolic Index Fiber by Laser Diode via Upside Down Tapered Hemispherical Microlens on the Tip of the Fiber

NASA Astrophysics Data System (ADS)

Das, Bishuddhananda; Middya, Tapas Ranjan; Gangopadhyay, Sankar

2017-12-01

We report the theoretical investigation of the coupling optics involving laser diode to single-mode circular core parabolic index fiber via upside down tapered hemispherical microlens on the tip of the fiber in the presence of possible transverse and angular mismatches. Using the relevant ABCD matrix for such tapered hemispherical microlens, we formulate analytical expressions for the coupling efficiencies in the presence of the said two mismatches. Further, the transmitted spot size of the source via the hemispherical lens and the tapered region should match with the spot size of the fiber for obtaining maximum coupling. The investigations have been made for two practical wavelengths, namely 1.3 and 1.5 μm in order to find the tolerance of this coupling device with respect to the said kinds of mismatches at the concerned wavelengths. Although our simple method predicts the concerned coupling optics excellently, the evaluation of the concerned efficiencies and associated losses involve little computations. Thus this user-friendly technique and also the results found thereof will benefit the designers and packagers who are working in the field of optical technology.

Effects of Constituents and Lay-up Configuration on Drop-Weight Tests of Fiber-Metal Laminates

NASA Astrophysics Data System (ADS)

Liu, Yanxiong; Liaw, Benjamin

2010-02-01

Impact responses and damage of various fiber-metal laminates were studied using a drop-weight instrument with the post-impact damage characteristics being evaluated through ultrasonic and mechanical sectioning techniques. The first severe failure induced by the low-velocity drop-weight impact occurred as delamination between the aluminum and fiber-epoxy layers at the non-impact side. It was followed by a visible shear crack in the outer aluminum layer on the non-impact face. Through-thickness shear cracks in the aluminum sheets and severe damage in the fiber laminated layers (including delamination between adjacent fiber-epoxy laminae with different fiber orientations) developed under higher energy impacts. The impact properties of fiber-metal laminates varied with different constituent materials and fiber orientations. Since it was punched through easily, the aramid-fiber reinforced fiber-metal laminates (ARALL) offered poorer impact resistance than the glass-fiber reinforced fiber-metal laminates (GLARE). Tougher and more ductile aluminum alloys improved the impact resistance. GLARE made of cross-ply prepregs provided better impact resistance than GLARE with unidirectional plies.

Meso-Scale Progressive Damage Behavior Characterization of Triaxial Braided Composites under Quasi-Static Tensile Load

NASA Astrophysics Data System (ADS)

Ren, Yiru; Zhang, Songjun; Jiang, Hongyong; Xiang, Jinwu

2018-04-01

Based on continuum damage mechanics (CDM), a sophisticated 3D meso-scale finite element (FE) model is proposed to characterize the progressive damage behavior of 2D Triaxial Braided Composites (2DTBC) with 60° braiding angle under quasi-static tensile load. The modified Von Mises strength criterion and 3D Hashin failure criterion are used to predict the damage initiation of the pure matrix and fiber tows. A combining interface damage and friction constitutive model is applied to predict the interface damage behavior. Murakami-Ohno stiffness degradation scheme is employed to predict the damage evolution process of each constituent. Coupling with the ordinary and translational symmetry boundary conditions, the tensile elastic response including tensile strength and failure strain of 2DTBC are in good agreement with the available experiment data. The numerical results show that the main failure modes of the composites under axial tensile load are pure matrix cracking, fiber and matrix tension failure in bias fiber tows, matrix tension failure in axial fiber tows and interface debonding; the main failure modes of the composites subjected to transverse tensile load are free-edge effect, matrix tension failure in bias fiber tows and interface debonding.

Fatigue testing and damage development in continuous fiber reinforced metal matrix composites

NASA Technical Reports Server (NTRS)

Johnson, W. S.

1988-01-01

A general overview of the fatigue behavior of metal matrix composites (MMC) is presented. The first objective is to present experimental procedures and techniques for conducting a meaningful fatigue test to detect and quantify fatigue damage in MMC. These techniques include interpretation of stress-strain responses, acid etching of the matrix, edge replicas of the specimen under load, radiography, and micrographs of the failure surfaces. In addition, the paper will show how stiffness loss in continuous fiber reinforced metal matrix composites can be a useful parameter for detecting fatigue damage initiation and accumulation. Second, numerous examples of how fatigue damage can initiate and grow in various MMC are given. Depending on the relative fatigue behavior of the fiber and matrix, and the interface properties, the failure modes of MMC can be grouped into four categories: (1) matrix dominated, (2) fiber dominated, (3) self-similar damage growth, and (4) fiber/matrix interfacial failures. These four types of damage will be discussed and illustrated by examples with the emphasis on the fatigue of unnotched laminates.

Fatigue testing and damage development in continuous fiber reinforced metal matrix composites

NASA Technical Reports Server (NTRS)

Johnson, W. S.

1989-01-01

A general overview of the fatigue behavior of metal matrix composites (MMC) is presented. The first objective is to present experimental procedures and techniques for conducting a meaningful fatigue test to detect and quantify fatigue damage in MMC. These techniques include interpretation of stress-strain responses, acid etching of the matrix, edge replicas of the specimen under load, radiography, and micrographs of the failure surfaces. In addition, the paper will show how stiffness loss in continuous fiber reinforced metal matrix composites can be a useful parameter for detecting fatigue damage initiation and accumulation. Second, numerous examples of how fatigue damage can initiate and grow in various MMC are given. Depending on the relative fatigue behavior of the fiber and matrix, and the interface properties, the failure modes of MMC can be grouped into four categories: (1) matrix dominated, (2) fiber dominated, (3) self-similar damage growth, and (4) fiber/matrix interfacial failures. These four types of damage will be discussed and illustrated by examples with the emphasis on the fatigue of unnotched laminates.

Rotational 3D printing of damage-tolerant composites with programmable mechanics.

PubMed

Raney, Jordan R; Compton, Brett G; Mueller, Jochen; Ober, Thomas J; Shea, Kristina; Lewis, Jennifer A

2018-02-06

Natural composites exhibit exceptional mechanical performance that often arises from complex fiber arrangements within continuous matrices. Inspired by these natural systems, we developed a rotational 3D printing method that enables spatially controlled orientation of short fibers in polymer matrices solely by varying the nozzle rotation speed relative to the printing speed. Using this method, we fabricated carbon fiber-epoxy composites composed of volume elements (voxels) with programmably defined fiber arrangements, including adjacent regions with orthogonally and helically oriented fibers that lead to nonuniform strain and failure as well as those with purely helical fiber orientations akin to natural composites that exhibit enhanced damage tolerance. Our approach broadens the design, microstructural complexity, and performance space for fiber-reinforced composites through site-specific optimization of their fiber orientation, strain, failure, and damage tolerance. Copyright © 2018 the Author(s). Published by PNAS.

An Acoustic Emission and Acousto-Ultrasonic Analysis of Impact Damaged Composite Pressure Vessels

NASA Technical Reports Server (NTRS)

Walker, James L.; Workman, Gary L.; Workman, Gary L.

1996-01-01

The research presented herein summarizes the development of acoustic emission (AE) and acousto-ultrasonic (AU) techniques for the nondestructive evaluation of filament wound composite pressure vessels. Vessels fabricated from both graphite and kevlar fibers with an epoxy matrix were examined prior to hydroburst using AU and during hydroburst using AE. A dead weight drop apparatus featuring both blunt and sharp impactor tips was utilized to produce a single known energy 'damage' level in each of the vessels so that the degree to which the effects of impact damage could be measured. The damage levels ranged from barely visible to obvious fiber breakage and delamination. Independent neural network burst pressure prediction models were developed from a sample of each fiber/resin material system. Here, the cumulative AE amplitude distribution data collected from low level proof test (25% of the expected burst for undamaged vessels) were used to measure the effects of the impact on the residual burst pressure of the vessels. The results of the AE/neural network model for the inert propellant filled graphite/epoxy vessels 'IM7/3501-6, IM7/977-2 and IM7/8553-45' demonstrated that burst pressures can be predicted from low level AE proof test data, yielding an average error of 5.0%. The trained network for the IM7/977-2 class vessels was also able to predict the expected burst pressure of taller vessels (three times longer hoop region length) constructed of the same material and using the same manufacturing technique, with an average error of 4.9%. To a lesser extent, the burst pressure prediction models could also measure the effects of impact damage to the kevlar/epoxy 'Kevlar 49/ DPL862' vessels. Here though, due to the higher attenuation of the material, an insufficient amount of AE amplitude information was collected to generate robust network models. Although, the worst case trial errors were less than 6%, when additional blind predictions were attempted, errors as high as 50% were produced. An acousto-ultrasonic robotic evaluation system (AURES) was developed for mapping the effects of damage on filament wound pressure vessels prior to hydroproof testing. The AURES injects a single broadband ultrasonic pulse into each vessel at preprogrammed positions and records the effects of the interaction of that pulse on the material volume with a broadband receiver. A stress wave factor in the form of the energy associated with the 750 to 1000 kHz and 1000 to 1250 kHz frequency bands were used to map the potential failure sites for each vessel. The energy map associated with the graphite/epoxy vessels was found to decrease in the region of the impact damage. The kevlar vessels showed the opposite trend, with the energy values increasing around the damage/failure sites.

International Conference Post Failure Analysis Techniques for Fiber Reinforced Composites Held in Dayton, Ohio on 1-3 July 1985

DTIC Science & Technology

1991-07-01

Massachusetts "A Microscopy Study of Impact Damage on Epoxy-Matrix ..... . . . 8-1 Carbon Fiber Composites " D.J. Boll, W.D. Bascom and J.C. Weidner Hercules...ON EPOXY-MATRIX CARBON FIBER COMPOSITES D.J. Boll, W.D. Bascom and J.C. Weidner Hercules Aerospace Magna, Utah A Microscopy Study of Impact Damage on...Epoxy-Matrix Carbon Fiber Composites D. 3. Boll, W. D. Bascom, J. C. Weidner and W. J. Murri Hercules Aerospace Magna, Utah Abstract The damage

Characterization of laser-driven shock waves in solids using a fiber optic pressure probe

DOE PAGES

Cranch, Geoffrey A.; Lunsford, Robert; Grun, Jacob; ...

2013-11-08

Measurement of laser-driven shock wave pressure in solid blocks of polymethyl methacrylate is demonstrated using fiber optic pressure probes. Three probes based on a fiber Fabry–Perot, fiber Bragg grating, and interferometric fiber tip sensor are tested and compared. Shock waves are generated using a high-power laser focused onto a thin foil target placed in close proximity to the test blocks. The fiber Fabry–Perot sensor appears capable of resolving the shock front with a rise time of 91 ns. As a result, the peak pressure is estimated, using a separate shadowgraphy measurement, to be 3.4 GPa.

Conformal Regge theory

NASA Astrophysics Data System (ADS)

Goncalves, Vasco David Fonseca

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Analytical Applications of Fluorescent Carbon Dots

NASA Astrophysics Data System (ADS)

Goncalves, Helena Maria Rodrigues

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Nanostructured Photoanodes for Solar Cells

NASA Astrophysics Data System (ADS)

Apolinario, Arlete Ondina Alves da Silva

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Chemoselectivity of Immobilized Transition Metal Catalysts

NASA Astrophysics Data System (ADS)

Teixeira, Filipe

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Sources and diagnostics for attosecond science

NASA Astrophysics Data System (ADS)

Miranda, Miguel Nicolau da Costa Ribeiro de

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Holmium laser use in debridement of stable labral lesions: two-year experience in initial 50 patients

NASA Astrophysics Data System (ADS)

Dew, Douglas K.; Risch, E. David

1994-09-01

The purpose of this study is to determine the laser related complication rate for shoulder arthroscopy in the initial clinical experience of 50 patients, and to identify potential advantages of laser use in shoulder arthroscopy. Fifty patients spanning ages 25 to 87 were treated. Surgical debridement was selective and conservative creating a smooth post resection rim. In those that included rotator cuff tears, in addition to arthroscopic debridement, a mini arthrotomy and open acromioplasty were performed. Changes in arthroscopic technique due to laser use included no arthroscopic pump use and use of the shaver only when the fiber could not be easily seen with severe synovitis. We found that the hyper-vascular synovium did not need to be resected last, it could be resected at any point during the procedure. Four hundred and 600 micron fiberoptics were used as well as 20 watts average power. Technical advantage of the laser was felt to be the size of the instrument probe and the availability of excellent hemostasis. Complications include one case of arthroscope damage and one case with a broken fiber tip which was removed with a grasper. Long term follow up of these patients is now underway.

Healthy hair: what is it?

PubMed

Sinclair, Rodney D

2007-12-01

Shiny hair with a smooth texture and clean-cut ends or tapered tips is generally perceived to be healthy. Hair texture and shine relate to hair surface properties, whereas the integrity of hair ends relates to the hair cortex. Hair can be straight, wavy or curly, blonde, black, brown, red, gray white, and its natural variations are important to our identity. Manipulation of the normal structure of the hair shaft is epidemic and dictated by culture, fashion, and above all, celebrity. Although cosmetic procedures are intrinsically safe, there is potential for damage to the hair. Loss of lustre, frizz, split ends, and other hair problems are particularly prevalent among people who repeatedly alter the natural style of their hair or among people with hair that is intrinsically weak. This may be due to individual or racial variation or less commonly an inherited structural abnormality in hair fiber formation. Hair health is also affected by common afflictions of the scalp as well as age-related phenomena such as graying and androgenetic alopecia. Hair products that improve the structural integrity of hair fibers and increase tensile strength are available, as are products that increase hair volume, reduce frizz, improve hair manageability, and stimulate new hair growth.

Rotational 3D printing of damage-tolerant composites with programmable mechanics

PubMed Central

Raney, Jordan R.; Compton, Brett G.; Ober, Thomas J.; Shea, Kristina; Lewis, Jennifer A.

2018-01-01

Natural composites exhibit exceptional mechanical performance that often arises from complex fiber arrangements within continuous matrices. Inspired by these natural systems, we developed a rotational 3D printing method that enables spatially controlled orientation of short fibers in polymer matrices solely by varying the nozzle rotation speed relative to the printing speed. Using this method, we fabricated carbon fiber–epoxy composites composed of volume elements (voxels) with programmably defined fiber arrangements, including adjacent regions with orthogonally and helically oriented fibers that lead to nonuniform strain and failure as well as those with purely helical fiber orientations akin to natural composites that exhibit enhanced damage tolerance. Our approach broadens the design, microstructural complexity, and performance space for fiber-reinforced composites through site-specific optimization of their fiber orientation, strain, failure, and damage tolerance. PMID:29348206

Tip60 degradation by adenovirus relieves transcriptional repression of viral transcriptional activator EIA.

PubMed

Gupta, A; Jha, S; Engel, D A; Ornelles, D A; Dutta, A

2013-10-17

Adenoviruses are linear double-stranded DNA viruses that infect human and rodent cell lines, occasionally transform them and cause tumors in animal models. The host cell challenges the virus in multifaceted ways to restrain viral gene expression and DNA replication, and sometimes even eliminates the infected cells by programmed cell death. To combat these challenges, adenoviruses abrogate the cellular DNA damage response pathway. Tip60 is a lysine acetyltransferase that acetylates histones and other proteins to regulate gene expression, DNA damage response, apoptosis and cell cycle regulation. Tip60 is a bona fide tumor suppressor as mice that are haploid for Tip60 are predisposed to tumors. We have discovered that Tip60 is degraded by adenovirus oncoproteins EIB55K and E4orf6 by a proteasome-mediated pathway. Tip60 binds to the immediate early adenovirus promoter and suppresses adenovirus EIA gene expression, which is a master regulator of adenovirus transcription, at least partly through retention of the virally encoded repressor pVII on this promoter. Thus, degradation of Tip60 by the adenoviral early proteins is important for efficient viral early gene transcription and for changes in expression of cellular genes.

Pressurized air injection in an axial hydro-turbine model for the mitigation of tip leakage cavitation

NASA Astrophysics Data System (ADS)

Rivetti, A.; Angulo, M.; Lucino, C.; Liscia, S.

2015-12-01

Tip leakage vortex cavitation in axial hydro-turbines may cause erosion, noise and vibration. Damage due to cavitation can be found at the tip of the runner blades on the low pressure side and the discharge ring. In some cases, the erosion follows an oscillatory pattern that is related to the number of guide vanes. That might suggest that a relationship exists between the flow through the guide vanes and the tip vortex cavitating core that induces this kind of erosion. On the other hand, it is known that air injection has a beneficial effect on reducing the damage by cavitation. In this paper, a methodology to identify the interaction between guide vanes and tip vortex cavitation is presented and the effect of air injection in reducing this particular kind of erosion was studied over a range of operating conditions on a Kaplan scale model. It was found that air injection, at the expense of slightly reducing the efficiency of the turbine, mitigates the erosive potential of tip leakage cavitation, attenuates the interaction between the flow through the guide vanes and the tip vortex and decreases the level of vibration of the structural components.

Time-of-Flight Tip-Clearance Measurements

NASA Technical Reports Server (NTRS)

Dhadwal, H. S.; Kurkov, A. P.; Janetzke, D. C.

1999-01-01

In this paper a time-of-flight probe system incorporating the two integrated fiber optic probes which are tilted equally relative to the probe holder centerline, is applied for the first time to measure the tip clearance of an advanced fan prototype. Tip clearance is largely independent of the signal amplitude and it relies on timing measurement. This work exposes optical effects associated with the fan blade stagger angle that were absent during the original spin-rig experiment on the zero stagger rotor. Individual blade tip clearances were measured with accuracy of +/- 127-mm (+/- 0.005-in). Probe features are discussed and improvements to the design are suggested.

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

PubMed

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

2015-11-01

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

Development of an optical fiber SERS microprobe for minimally invasive sensing applications

NASA Astrophysics Data System (ADS)

Mamun, Md Abdullah Al; Juodkazis, Saulius; Mahadevan-Jansen, Anita; Stoddart, Paul R.

2018-02-01

Numerous potential biomedical sensing applications of surface-enhanced Raman scattering (SERS) have been reported, but its practical use has been limited by the lack of a robust sensing platform. Optical fiber SERS probes show great promise, but are limited by the prominent silica Raman background, which requires the use of bulky optics for filtering the signal collection and excitation delivery paths. In the present study, a SERS microprobe has been designed and developed to eliminate the bottlenecks outlined above. For efficient excitation and delivery of the SERS signal, both hollow core photonic crystal fiber and double clad fiber have been investigated. While the hollow core fiber was still found to have excessive silica background, the double clad fiber allows efficient signal collection via the multi-mode inner cladding. A micro filtering mechanism has been designed, which can be integrated into the tip of the optical fiber SERS probe, providing filtering to suppress silica Raman background and thus avoiding the need for bulky optics. The design also assists in the efficient collection of SERS signal from the sample by rejecting Rayleigh scattered light from the sample. Optical fiber cleaving using ultra-short laser pulses was tested for improved control of the fiber tip geometry. With this miniaturized and integrated filtering mechanism, it is expected that the developed probe will promote the use of SERS for minimally invasive biomedical monitoring and sensing applications in future. The probe could potentially be placed inside a small gauge hypodermic needle and would be compatible with handheld portable spectrometers.

Effect of the Microstructure on the Fracture Mode of Short-Fiber Reinforced Plastic Composites

NASA Astrophysics Data System (ADS)

Nishikawa, Masaaki; Okabe, Tomonaga; Takeda, Nobuo

A numerical simulation was presented to discuss the microscopic damage and its influence on the strength and energy-absorbing capability of short-fiber reinforced plastic composites. The dominant damage includes matrix crack and/or interfacial debonding, when the fibers are shorter than the critical length for fiber breakage. The simulation addressed the matrix crack with a continuum damage mechanics (CDM) model and the interfacial debonding with an embedded process zone (EPZ) model. Fictitious free-edge effects on the fracture modes were successfully eliminated with the periodic-cell simulation. The advantage of our simulation was pointed out by demonstrating that the simulation with edge effects significantly overestimates the dissipative energy of the composites. We then investigated the effect of the material microstructure on the fracture modes in the composites. The simulated results clarified that the inter-fiber distance affects the breaking strain of the composites and the fiber-orientation angle affects the position of the damage initiation. These factors influence the strength and energy-absorbing capability of short fiber-reinforced composites.

Mesoscopic effect of spectral modulation for the light transmitted by a SNOM tip

NASA Astrophysics Data System (ADS)

Rähn, M.; Pärs, M.; Palm, V.; Jaaniso, R.; Hizhnyakov, V.

2010-06-01

The effect of a tapered metal-coated optical fiber terminated by a sub-wavelength aperture (SWA) on the spectrum of the transmitted light is investigated experimentally. Under certain conditions a remarkable spectral modulation of the transmitted light can be observed. This effect is of a mesoscopic origin, occurring only for a certain interval of SWA diameters. One can conclude that a noticeable modulation appears when the number of the transmitted fiber modes is small but exceeds unity, thus indicating the presence of a phase shift between different modes. To discern between two possible sources of such phase shift, the fiber length dependence of the output spectrum has been studied. According to the results obtained for the used sample of 200 nm SNOM tip, the observed phase shift is mostly caused rather by the inherent modal dispersion of the multimode fiber than by the mode-dependent light slowdown in the tapered region close to SWA due to the coupling to surface plasmons of the metal coating. The SWA acts here mainly as an effective mode filter.

Guided wave and damage detection in composite laminates using different fiber optic sensors.

PubMed

Li, Fucai; Murayama, Hideaki; Kageyama, Kazuro; Shirai, Takehiro

2009-01-01

Guided wave detection using different fiber optic sensors and their applications in damage detection for composite laminates were systematically investigated and compared in this paper. Two types of fiber optic sensors, namely fiber Bragg gratings (FBG) and Doppler effect-based fiber optic (FOD) sensors, were addressed and guided wave detection systems were constructed for both types. Guided waves generated by a piezoelectric transducer were propagated through a quasi-isotropic carbon fiber reinforced plastic (CFRP) laminate and acquired by these fiber optic sensors. Characteristics of these fiber optic sensors in ultrasonic guided wave detection were systematically compared. Results demonstrated that both the FBG and FOD sensors can be applied in guided wave and damage detection for the CFRP laminates. The signal-to-noise ratio (SNR) of guided wave signal captured by an FOD sensor is relatively high in comparison with that of the FBG sensor because of their different physical principles in ultrasonic detection. Further, the FOD sensor is sensitive to the damage-induced fundamental shear horizontal (SH(0)) guided wave that, however, cannot be detected by using the FBG sensor, because the FOD sensor is omnidirectional in ultrasound detection and, in contrast, the FBG sensor is severely direction dependent.

Damage thresholds of silica fibers in holmium:YAG laser energy delivery for medical applications

NASA Astrophysics Data System (ADS)

Marolda, Matthew D.; Perrault, Donald F., Jr.; Pankratov, Michail M.; Shapshay, Stanley M.

1993-07-01

Pulsed Holmium:YAG (Ho:YAG) laser has been approved for some clinical applications and is under investigation for others. There is little published evidence on the durability or damage parameters for the fibers used in delivering energy from pulsed Ho:YAG laser. This study makes an initial attempt to investigate the damage threshold of different silica fibers under various conditions. Three types of fibers supplied by different manufacturers underwent laboratory testing. The overall finding of the study is that a new `perfect' fiber sustains no damage when fired without a target in air or in saline at energies up to 1.5 J/pulse and repetition rate up to 10 Hz. This study suggests that one may need to chose a fiber according to the clinical procedure to be performed: in cases where only soft tissue is to be manipulated - - any fiber may fare well, in cases where bone or calcified tissue is to be lased -- one may need fiber with aluminized or other hard coating. We also conclude that only professional refinishing with the removal of all exposed core-cladding material can insure trouble free performance.

Diabetes: Dental Tips

MedlinePlus

Diabetes: Dental Tips For more copies contact: National Institute of Dental and Craniofacial Research National Oral Health Information Clearinghouse ... damage the gum and bone that hold your teeth in place and may lead to painful chewing ...

Stochastic integrated assessment of climate tipping points indicates the need for strict climate policy

NASA Astrophysics Data System (ADS)

Lontzek, Thomas S.; Cai, Yongyang; Judd, Kenneth L.; Lenton, Timothy M.

2015-05-01

Perhaps the most `dangerous’ aspect of future climate change is the possibility that human activities will push parts of the climate system past tipping points, leading to irreversible impacts. The likelihood of such large-scale singular events is expected to increase with global warming, but is fundamentally uncertain. A key question is how should the uncertainty surrounding tipping events affect climate policy? We address this using a stochastic integrated assessment model, based on the widely used deterministic DICE model. The temperature-dependent likelihood of tipping is calibrated using expert opinions, which we find to be internally consistent. The irreversible impacts of tipping events are assumed to accumulate steadily over time (rather than instantaneously), consistent with scientific understanding. Even with conservative assumptions about the rate and impacts of a stochastic tipping event, today’s optimal carbon tax is increased by ~50%. For a plausibly rapid, high-impact tipping event, today’s optimal carbon tax is increased by >200%. The additional carbon tax to delay climate tipping grows at only about half the rate of the baseline carbon tax. This implies that the effective discount rate for the costs of stochastic climate tipping is much lower than the discount rate for deterministic climate damages. Our results support recent suggestions that the costs of carbon emission used to inform policy are being underestimated, and that uncertain future climate damages should be discounted at a low rate.

Surface crack analysis applied to impact damage in a thick graphite-epoxy composite

NASA Technical Reports Server (NTRS)

Poe, C. C., Jr.; Harris, C. E.; Morris, D. H.

1988-01-01

The residual tensile strength of a thick graphite/epoxy composite with impact damage was predicted using surface crack analysis. The damage was localized to a region directly beneath the impact site and extended only part way through the laminate. The damaged region contained broken fibers, and the locus of breaks in each layer resembled a crack perpendicular to the direction of the fibers. In some cases, the impacts broke fibers without making a visible crater. The impact damage was represented as a semi-elliptical surface crack with length and depth equal to that of the impact damage. The maximum length and depth of the damage were predicted with a stress analysis and a maximum shear stress criterion. The predictions and measurements of strength were in good agreement.

Surface crack analysis applied to impact damage in a thick graphite/epoxy composite

NASA Technical Reports Server (NTRS)

Poe, Clarence C., Jr.; Harris, Charles E.; Morris, Don H.

1990-01-01

The residual tensile strength of a thick graphite/epoxy composite with impact damage was predicted using surface crack analysis. The damage was localized to a region directly beneath the impact site and extended only part way through the laminate. The damaged region contained broken fibers, and the locus of breaks in each layer resembled a crack perpendicular to the direction of the fibers. In some cases, the impacts broke fibers without making a visible crater. The impact damage was represented as a semi-elliptical surface crack with length and depth equal to that of the impact damage. The maximum length and depth of the damage were predicted with a stress analysis and a maximum shear stress criterion. The predictions and measurements of strength were in good agreement.

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

PubMed

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

2016-12-15

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

Radiation Effects on Transmission in Optical Fiber Systems.

DTIC Science & Technology

1981-06-02

TRANSMSSION - ~IN OPTCAL FIBE SYSTEMS UMATED STATE NAVAL ACADEMY * ANNAPOLIS, MARYLAND * 1981 * -~~ Thm dooummt bus bur apwgd hi pubic AWNm mi Imi it dlbutlou...nanometers. Of the fibers studied, two were high purity silica fibers. An important result of the study was that the radiation induced damage was...wavelength related. The induced damage decreased rapidly as the wavelength increased from 800 to 1100 nanometers, with minimal damage noted above 1300

Ultrasonic Assessment of Impact-Induced Damage and Microcracking in Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Gyekanyesi, John (Technical Monitor); Liaw, Benjamin; Villars, Esther; Delmont, Frantz

2003-01-01

The main objective of this NASA Faculty Awards for Research (FAR) project is to conduct ultrasonic assessment of impact-induced damage and microcracking in fiber-metal laminated (FML) composites at various temperatures. It is believed that the proposed study of impact damage assessment on FML composites will benefit several NASA's missions and current interests, such as ballistic impact testing of composite fan containment and high strain rate deformation modeling of polymer matrix composites. Impact-induced damage mechanisms in GLARE and ARALL fiber-metal laminates subject to instrumented drop-weight impacts at various temperatures were studied. GLARE and ARALL are hybrid composites made of alternating layers of aluminum and glass- (for GLARE) and aramid- (for ARALL) fiber reinforced epoxy. Damage in pure aluminum panels impacted by foreign objects was mainly characterized by large plastic deformation surrounding a deep penetration dent. On the other hand, plastic deformation in fiber-metal laminates was often not as severe although the penetration dent was still produced. The more stiff fiber-reinforced epoxy layers provided better bending rigidity; thus, enhancing impact damage tolerance. Severe cracking, however, occurred due to the use of these more brittle fiber-reinforced epoxy layers. Fracture patterns, e.g., crack length and delamination size, were greatly affected by the lay-up configuration rather than by the number of layers, which implies that thickness effect was not significant for the panels tested in this study. Immersion ultrasound techniques were then used to assess damages generated by instrumented drop-weight impacts onto these fiber-metal laminate panels as well as 2024-T3 aluminum/cast acrylic sandwich plates adhered by epoxy. Depending on several parameters, such as impact velocity, mass, temperature, laminate configuration, sandwich construction, etc., various types of impact damage were observed, including plastic deformation, radiating cracks emanating from the impact site, ring cracks surrounding the impact site, partial and full delamination, and combinations of these damages.

Damage to cochlear efferents following AF64A intoxication.

PubMed

Smith, D W; Mount, R J

1993-07-01

Damage to cochlear efferents in chinchillas was assessed using transmission electron microscopy following unilateral treatment with the cholinotoxin ethylcholine mustard aziridinium ion (AF64A). AF64A was diluted in artificial perilymph to concentrations ranging from 0.5 to 100 microM. Survival times ranged from 1 to 12 weeks. At concentrations above 10 microM, widespread damage was noted to efferent fibers within the inner spiral bundle (ISB), tunnel spiral bundle (TSB), tunnel radial fibers (TRF) and efferent terminals at the base of OHCs. This damage included degeneration of fibers and terminals, delamination of mitochondria, vacuolization, and loss of cell membrane. However, at high concentrations, non-specific damage was also noted as thinnings or discontinuities of the membrane of OHCs and afferent fibers. At concentrations between 3 and 10 microM, selective damage was observed to efferent fibers within the ISB, TSB, TRF, and to terminals at the base of the OHCs, with all other structures appearing normal. At concentrations of 0.5 and 1 microM, damage was limited to efferent fibers within the TSB and ISB below the inner hair cells. In general, insult was greatest to middle- and basal-turn efferents, and longer survival times did not produce greater damage to, or loss of, efferents. These data suggest that at low concentrations, AF64A produces a partial yet selective degeneration of cochlear efferents within both the medial and lateral tracts, and that at the lowest concentrations used in these studies, AF64A produces a preferential insult on lateral olivocochlear efferents.

A Damage-Dependent Finite Element Analysis for Fiber-Reinforced Composite Laminates

NASA Technical Reports Server (NTRS)

Coats, Timothy W.; Harris, Charles E.

1998-01-01

A progressive damage methodology has been developed to predict damage growth and residual strength of fiber-reinforced composite structure with through penetrations such as a slit. The methodology consists of a damage-dependent constitutive relationship based on continuum damage mechanics. Damage is modeled using volume averaged strain-like quantities known as internal state variables and is represented in the equilibrium equations as damage induced force vectors instead of the usual degradation and modification of the global stiffness matrix.

Back-illuminate fiber system research for multi-object fiber spectroscopic telescope

NASA Astrophysics Data System (ADS)

Zhou, Zengxiang; Liu, Zhigang; Hu, Hongzhuan; Wang, Jianping; Zhai, Chao; Chu, Jiaru

2016-07-01

In the telescope observation, the position of fiber will highly influence the spectra efficient input in the fiber to the spectrograph. When the fibers were back illuminated on the spectra end, they would export light on the positioner end, so the CCD cameras could capture the photo of fiber tip position covered the focal plane, calculates the precise position information by light centroid method and feeds back to control system. A set of fiber back illuminated system was developed which combined to the low revolution spectro instruments in LAMOST. It could provide uniform light output to the fibers, meet the requirements for the CCD camera measurement. The paper was introduced the back illuminated system design and different test for the light resource. After optimization, the effect illuminated system could compare with the integrating sphere, meet the conditions of fiber position measurement.Using parallel controlled fiber positioner as the spectroscopic receiver is an efficiency observation system for spectra survey, has been used in LAMOST recently, and will be proposed in CFHT and rebuilt telescope Mayall. In the telescope observation, the position of fiber will highly influence the spectra efficient input in the fiber to the spectrograph. When the fibers were back illuminated on the spectra end, they would export light on the positioner end, so the CCD cameras could capture the photo of fiber tip position covered the focal plane, calculates the precise position information by light centroid method and feeds back to control system. After many years on these research, the back illuminated fiber measurement was the best method to acquire the precision position of fibers. In LAMOST, a set of fiber back illuminated system was developed which combined to the low revolution spectro instruments in LAMOST. It could provide uniform light output to the fibers, meet the requirements for the CCD camera measurement and was controlled by high-level observation system which could shut down during the telescope observation. The paper was introduced the back illuminated system design and different test for the light resource. After optimization, the effect illuminated system could compare the integrating sphere, meet the conditions of fiber position measurement.

Electronic equipment vulnerability to fire released carbon fibers

NASA Technical Reports Server (NTRS)

Pride, R. A.; Mchatton, A. D.; Musselman, K. A.

1980-01-01

The vulnerability of electronic equipment to damage by carbon fibers released from burning aircraft type structural composite materials was investigated. Tests were conducted on commercially available stereo power amplifiers which showed that the equipment was damaged by fire released carbon fibers but not by the composite resin residue, soot and products of combustion of the fuel associated with burning the carbon fiber composites. Results indicate that the failure rates of the equipment exposed to the fire released fiber were consistent with predictions based on tests using virgin fibers.

Diode laser for endodontic treatment: investigations of light distribution and disinfection efficiency

NASA Astrophysics Data System (ADS)

Stock, Karl; Graser, Rainer; Udart, Martin; Kienle, Alwin; Hibst, Raimund

2011-03-01

Diode lasers are used in dentistry mainly for oral surgery and disinfection of root canals in endodontic treatment. The purpose of this study was to investigate and to improve the laser induced bacteria inactivation in endodontic treatment. An essential prerequisite of the optimization of the irradiation process and device is the knowledge about the determinative factors of bacteria killing: light intensity? light dosis? temperature? In order to find out whether high power NIR laser bacterial killing is caused by a photochemical or a photothermal process we heated bacteria suspensions of E. coli K12 by a water bath and by a diode laser (940 nm) with the same temporal temperature course. Furthermore, bacteria suspensions were irradiated while the temperature was fixed by ice water. Killing of bacteria was measured via fluorescence labeling. In order to optimize the irradiation of the root canal, we designed special fiber tips with radial light emission characteristic by optical ray tracing simulations. Also, we calculated the resulting light distribution in dentin by voxelbased Monte Carlo simulations. Furthermore, we irradiated root canals of extracted human teeth using different fiber tip geometries and measured the resulting light and heat distribution by CCD-camera and thermography. Comparison of killing rates between laser and water based heating shows no significant differences, and irradiation of ice cooled suspensions has no substantial killing effect. Thus, the most important parameter for bacterial killing is the maximum temperature. Irradiation of root canals using fiber tips with radial light emission results in a more defined irradiated area with minor irradiation of the apex and higher intensity and therefore higher temperature increase on root canal surface. In conclusion, our experiments show that at least for E. coli bacteria inactivation by NIR laser irradiation is solely based on a thermal process and that heat distribution in root canal can be significantly improved by specially designed fiber tips.

Characterization of impact damage in woven fiber composites using fiber Bragg grating sensing and NDE

NASA Astrophysics Data System (ADS)

Hiche, Cristobal; Liu, Kuang C.; Seaver, Mark; Wei, Jun; Chattopadhyay, Aditi

2009-03-01

Woven fiber composites are currently being investigated due to their advantages over other materials, making them suitable for low weight, high stiffness, and high interlaminar fracture toughness applications such as missiles, body armor, satellites, and many other aerospace applications. Damage characterization of woven fabrics is a complex task due to their tendency to exhibit different failure modes based on the weave configuration, orientation, ply stacking and other variables. A multiscale model is necessary to accurately predict progressive damage. The present research is an experimental study on damage characterization of three different woven fiber laminates under low energy impact using Fiber Bragg Grating (FBG) sensors and flash thermography. A correlation between the measured strain from FBG sensors and the damaged area obtained from flash thermography imaging has been developed. It was observed that the peak strain in the fabrics were strongly dependent on the weave geometry and decreased at different rates as damage area increased due to dissimilar failure modes. Experimental observations were validated with the development of a multiscale model. A FBG sensor placement model was developed which showed that FBG sensor location and orientation plays a key role in the sensing capabilities of strain on the samples.

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

NASA Astrophysics Data System (ADS)

Minakuchi, Shu; Tsukamoto, Haruka; Takeda, Nobuo

2009-03-01

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

Effects of Friction Reduction on Fiber Damage in a Saw-Type Lint Cleaner

USDA-ARS?s Scientific Manuscript database

U.S. cotton is at a competitive disadvantage from a fiber-quality standpoint, because lint cleaning is required for mechanically harvested cotton, and lint cleaning causes fiber damage. Lint-cleaning research has focused mainly on modifying saw-type lint cleaners, but the work reported here focuses...

Monitoring Damage Propagation in Glass Fiber Composites Using Carbon Nanofibers.

PubMed

Al-Sabagh, Ahmed; Taha, Eman; Kandil, Usama; Nasr, Gamal-Abdelnaser; Reda Taha, Mahmoud

2016-09-10

In this work, we report the potential use of novel carbon nanofibers (CNFs), dispersed during fabrication of glass fiber composites to monitor damage propagation under static loading. The use of CNFs enables a transformation of the typically non-conductive glass fiber composites into new fiber composites with appreciable electrical conductivity. The percolation limit of CNFs/epoxy nanocomposites was first quantified. The electromechanical responses of glass fiber composites fabricated using CNFs/epoxy nanocomposite were examined under static tension loads. The experimental observations showed a nonlinear change of electrical conductivity of glass fiber composites incorporating CNFs versus the stress level under static load. Microstructural investigations proved the ability of CNFs to alter the polymer matrix and to produce a new polymer nanocomposite with a connected nanofiber network with improved electrical properties and different mechanical properties compared with the neat epoxy. It is concluded that incorporating CNFs during fabrication of glass fiber composites can provide an innovative means of self-sensing that will allow damage propagation to be monitored in glass fiber composites.

Effects of Fiber Orientation on the Frictional Properties and Damage of Regenerative Articular Cartilage Surfaces

PubMed Central

Accardi, Mario Alberto; McCullen, Seth D.; Callanan, Anthony; Chung, Sangwon; Cann, Philippa M.

2013-01-01

Articular cartilage provides a low-friction, wear-resistant surface for diarthrodial joints. Due to overloading and overuse, articular cartilage is known to undergo significant wear and degeneration potentially resulting in osteoarthritis (OA). Regenerative medicine strategies offer a promising solution for the treatment of articular cartilage defects and potentially localized early OA. Such strategies rely on the development of materials to restore some aspects of cartilage. In this study, microfibrous poly(ɛ-caprolactone) scaffolds of varying fiber orientations (random and aligned) were cultured with bovine chondrocytes for 4 weeks in vitro, and the mechanical and frictional properties were evaluated. Mechanical properties were quantified using unconfined compression and tensile testing techniques. Frictional properties were investigated at physiological compressive strains occurring in native articular cartilage. Scaffolds were sheared along the fiber direction, perpendicular to the fiber direction and in random orientation. The evolution of damage as a result of shear was evaluated via white light interferometry and scanning electron microscopy. As expected, the fiber orientation strongly affected the tensile properties as well as the compressive modulus of the scaffolds. Fiber orientation did not significantly affect the equilibrium frictional coefficient, but it was, however, a key factor in dictating the evolution of surface damage on the surface. Scaffolds shear tested perpendicular to the fiber orientation displayed the highest surface damage. Our results suggest that the fiber orientation of the scaffold implanted in the joint could strongly affect its resistance to damage due to shear. Scaffold fiber orientation should thus be carefully considered when using microfibrous scaffolds. PMID:23688110

Grating-flanked plasmonic coaxial apertures for efficient fiber optical tweezers.

PubMed

Saleh, Amr A E; Sheikhoelislami, Sassan; Gastelum, Steven; Dionne, Jennifer A

2016-09-05

Subwavelength plasmonic apertures have been foundational for direct optical manipulation of nanoscale specimens including sub-100 nm polymeric beads, metallic nanoparticles and proteins. While most plasmonic traps result in two-dimensional localization, three-dimensional manipulation has been demonstrated by integrating a plasmonic aperture on an optical fiber tip. However, such 3D traps are usually inefficient since the optical mode of the fiber and the subwavelength aperture only weakly couple. In this paper we design more efficient optical-fiber-based plasmonic tweezers combining a coaxial plasmonic aperture with a plasmonic grating coupler at the fiber tip facet. Using full-field finite difference time domain analysis, we optimize the grating design for both gold and silver fiber-based coaxial tweezers such that the optical transmission through the apertures is maximized. With the optimized grating, we show that the maximum transmission efficiency increases from 2.5% to 19.6% and from 1.48% to 16.7% for the gold and silver structures respectively. To evaluate their performance as optical tweezers, we calculate the optical forces and the corresponding trapping potential on dielectric particles interacting with the apertures. We demonstrate that the enahncement in the transmission translates into an equivalent increase in the optical forces. Consequently, the optical power required to achieve stable optical trapping is significantly reduced allowing for efficient localization and 3D manipulation of sub-30 nm dielectric particles.

An embedded fibre optic sensor for impact damage detection in composite materials

NASA Astrophysics Data System (ADS)

Glossop, Neil David William

1989-09-01

A structurally embedded fiber optic damage detection sensor for composite materials is described. The system is designed specifically for the detection of barely visible damage resulting from low velocity impacts in Kevlar-epoxy laminates. By monitoring the light transmission properties of optical fiber embedded in the composite, it was shown that the integrity of the material can be accurately determined. The effect of several parameters on the sensitivity of the system was investigated, including the effect of the optical fiber orientation and depth of embedding within the composite. A novel surface was also developed for the optical fibers to ensure they will fracture at the requisite damage level. The influence of the optical fiber sensors on the tensile and compressive material properties and on the impact resistance of the laminate was also studied. Extensive experimental results from impact tests are reported and a numerical model of the impact event is presented which is able to predict and model the damage mechanism and sensor system. A new and powerful method of nondestructive evaluation for translucent composite materials based on image enhanced backlighting is also described.

Post-Impact Fatigue Damage Monitoring Using Fiber Bragg Grating Sensors

PubMed Central

Shin, Chow-Shing; Liaw, Shien-Kuei; Yang, Shi-Wei

2014-01-01

It has been shown that impact damage to composite materials can be revealed by embedded Fiber Bragg Gratings (FBG) as a broadening and splitting of the latter's characteristic narrow peak reflected spectrum. The current work further subjected the impact damaged composite to cyclic loading and found that the FBG spectrum gradually submerged into a rise of background intensity as internal damages progressed. By skipping the impact, directing the impact to positions away from the FBG and examining the extracted fibers, we concluded that the above change is not a result of deterioration/damage of the sensor. It is caused solely by the damages initiated in the composite by the impact and aggravated by fatigue loading. Evolution of the grating spectrum may therefore be used to monitor qualitatively the development of the incurred damages. PMID:24594609

Endoscopic Photodynamic Therapy: Fiber Optic Delivery For The Treatment Of Esophageal And Bronchial Cancer

NASA Astrophysics Data System (ADS)

Mang, Thomas S.; Nava, Hector R.; Regal, Anne-Marie

1989-06-01

Clinical studies in photodynamic therapy (PDT) have utilized lasers to take advantage of coupling efficiencies to optical fibers allowing light to be delivered to many areas of the body. This is particularly true in endoscopic PDT. Both interstitial and superficial delivery techniques can be applied using one of a variety of delivery fibers available. A fiber with an optically flat end with a lens to produce a spot with a homogeneous intensity is used for superficial applications. Diffusers of various lengths, at the tip of a fiber, produce a cylindrical isotropic pattern and are suited for either intraluminal or interstitial illuminations.

Biomedical and sensing applications of a multi-mode biodegradable phosphate-based optical fiber

NASA Astrophysics Data System (ADS)

Podrazky, Ondřej; Peterka, Pavel; Vytykáčová, SoÅa.; Proboštová, Jana; Kuneš, Martin; Lyutakov, Oleksiy; Ceci-Ginistrelli, Edoardo; Pugliese, Diego; Boetti, Nadia G.; Janner, Davide; Milanese, Daniel

2018-02-01

We report on the employment of a biodegradable phosphate-based optical fiber as a pH sensing probe in physiological environment. The phosphate-based optical fiber preform was fabricated by the rod-in-tube technique. The fiber biodegradability was first tested in-vitro and then its biodegradability and toxicity were tested in-vivo. Optical probes for pH sensing were prepared by the immobilization of a fluorescent dye on the fiber tip by a sol-gel method. The fluorescence response of the pH-sensor was measured as a ratio of the emission intensities at the excitation wavelengths of 405 and 450 nm.

Extensive scarring induced by chronic intrathecal tubing augmented cord tissue damage and worsened functional recovery after rat spinal cord injury.

PubMed

Zhang, Shu-xin; Huang, Fengfa; Gates, Mary; White, Jason; Holmberg, Eric G

2010-08-30

Intrathecal infusion has been widely used to directly deliver drugs or neurotrophins to a lesion site following spinal cord injury. Evidence shows that intrathecal infusion is efficient for 7 days but is markedly reduced after 14 days, due to time dependent occlusion. In addition, extensive fibrotic scarring is commonly observed with intrathecal infusion. These anomalies need to be clearly elucidated in histology. In the present study, all adult Long-Evans rats received a 25 mm contusion injury on spinal cord T10 produced using the NYU impactor device. Immediately after injury, catheter tubing with an outer diameter of 0.38 mm was inserted through a small dural opening at L3 into the subdural space with the tubing tip positioned near the injury site. The tubing was connected to an Alzet mini pump, which was filled with saline solution and was placed subcutaneously. Injured rats without tubing served as control. Rats were behaviorally tested for 6 weeks using the BBB locomotor rating scale and histologically assessed for tissue scarring. Six weeks later, we found that the intrathecal tubing caused extensive scarring and inflammation, related to neutrophils, macrophages and plasma cells. The tubing's tip was occluded by scar tissue and inflammatory cells. The scar tissue surrounding the tubing consists of 20-70 layers of fibroblasts and densely compacted collagen fibers, seriously compressing and damaging the cord tissue. BBB scores of rats with intrathecal tubing were significantly lower than control rats (p<0.01) from 2 weeks after injury, implying serious impairment of functional recovery caused by the scarring. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Anisotropic constitutive model incorporating multiple damage mechanisms for multiscale simulation of dental enamel.

PubMed

Ma, Songyun; Scheider, Ingo; Bargmann, Swantje

2016-09-01

An anisotropic constitutive model is proposed in the framework of finite deformation to capture several damage mechanisms occurring in the microstructure of dental enamel, a hierarchical bio-composite. It provides the basis for a homogenization approach for an efficient multiscale (in this case: multiple hierarchy levels) investigation of the deformation and damage behavior. The influence of tension-compression asymmetry and fiber-matrix interaction on the nonlinear deformation behavior of dental enamel is studied by 3D micromechanical simulations under different loading conditions and fiber lengths. The complex deformation behavior and the characteristics and interaction of three damage mechanisms in the damage process of enamel are well captured. The proposed constitutive model incorporating anisotropic damage is applied to the first hierarchical level of dental enamel and validated by experimental results. The effect of the fiber orientation on the damage behavior and compressive strength is studied by comparing micro-pillar experiments of dental enamel at the first hierarchical level in multiple directions of fiber orientation. A very good agreement between computational and experimental results is found for the damage evolution process of dental enamel. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Multiscale Fiber Kinking: Computational Micromechanics and a Mesoscale Continuum Damage Mechanics Models

NASA Technical Reports Server (NTRS)

Herraez, Miguel; Bergan, Andrew C.; Gonzalez, Carlos; Lopes, Claudio S.

2017-01-01

In this work, the fiber kinking phenomenon, which is known as the failure mechanism that takes place when a fiber reinforced polymer is loaded under longitudinal compression, is studied. A computational micromechanics model is employed to interrogate the assumptions of a recently developed mesoscale continuum damage mechanics (CDM) model for fiber kinking based on the deformation gradient decomposition (DGD) and the LaRC04 failure criteria.

Design of a multifiber light delivery system for photoacoustic-guided surgery.

PubMed

Eddins, Blackberrie; Bell, Muyinatu A Lediju

2017-04-01

This work explores light delivery optimization for photoacoustic-guided minimally invasive surgeries, such as the endonasal transsphenoidal approach. Monte Carlo simulations were employed to study three-dimensional light propagation in tissue, comprising one or two 4-mm diameter arteries located 3 mm below bone, an absorbing metallic drill contacting the bone surface, and a single light source placed next to the 2.4-mm diameter drill shaft with a 2.9-mm diameter spherical drill tip. The optimal fiber distance from the drill shaft was determined from the maximum normalized fluence to the underlying artery. Using this optimal fiber-to-drill shaft distance, Zemax simulations were employed to propagate Gaussian beams through one or more 600 micron-core diameter optical fibers for detection on the bone surface. When the number of equally spaced fibers surrounding the drill increased, a single merged optical profile formed with seven or more fibers, determined by thresholding the resulting light profile images at 1 / e times the maximum intensity. We used these simulations to inform design requirements, build a one to seven multifiber light delivery prototype to surround a surgical drill, and demonstrate its ability to simultaneously visualize the tool tip and blood vessel targets in the absence and presence of bone. The results and methodology are generalizable to multiple interventional photoacoustic applications.

Characterization of a 3D optrode array for infrared neural stimulation

PubMed Central

Abaya, T.V.F.; Diwekar, M.; Blair, S.; Tathireddy, P.; Rieth, L.; Clark, G.A.; Solzbacher, F.

2012-01-01

This paper characterizes the Utah Slant Optrode Array (USOA) as a means to deliver infrared light deep into tissue. An undoped crystalline silicon (100) substrate was used to fabricate 10 × 10 arrays of optrodes with rows of varying lengths from 0.5 mm to 1.5 mm on a 400-μm pitch. Light delivery from optical fibers and loss mechanisms through these Si optrodes were characterized, with the primary loss mechanisms being Fresnel reflection, coupling, radiation losses from the tapered shank and total internal reflection in the tips. Transmission at the optrode tips with different optical fiber core diameters and light in-coupling interfaces was investigated. At λ = 1.55μm, the highest optrode transmittance of 34.7%, relative to the optical fiber output power, was obtained with a 50-μm multi-mode fiber butt-coupled to the optrode through an intervening medium of index n = 1.66. Maximum power is directed into the optrodes when using fibers with core diameters of 200 μm or less. In addition, the output power varied with the optrode length/taper such that longer and less tapered optrodes exhibited higher light transmission efficiency. Output beam profiles and potential impacts on physiological tests were also examined. Future work is expected to improve USOA efficiency to greater than 64%. PMID:23024914

Characterization of a 3D optrode array for infrared neural stimulation.

PubMed

Abaya, T V F; Diwekar, M; Blair, S; Tathireddy, P; Rieth, L; Clark, G A; Solzbacher, F

2012-09-01

This paper characterizes the Utah Slant Optrode Array (USOA) as a means to deliver infrared light deep into tissue. An undoped crystalline silicon (100) substrate was used to fabricate 10 × 10 arrays of optrodes with rows of varying lengths from 0.5 mm to 1.5 mm on a 400-μm pitch. Light delivery from optical fibers and loss mechanisms through these Si optrodes were characterized, with the primary loss mechanisms being Fresnel reflection, coupling, radiation losses from the tapered shank and total internal reflection in the tips. Transmission at the optrode tips with different optical fiber core diameters and light in-coupling interfaces was investigated. At λ = 1.55μm, the highest optrode transmittance of 34.7%, relative to the optical fiber output power, was obtained with a 50-μm multi-mode fiber butt-coupled to the optrode through an intervening medium of index n = 1.66. Maximum power is directed into the optrodes when using fibers with core diameters of 200 μm or less. In addition, the output power varied with the optrode length/taper such that longer and less tapered optrodes exhibited higher light transmission efficiency. Output beam profiles and potential impacts on physiological tests were also examined. Future work is expected to improve USOA efficiency to greater than 64%.

Design of a multifiber light delivery system for photoacoustic-guided surgery

NASA Astrophysics Data System (ADS)

Eddins, Blackberrie; Bell, Muyinatu A. Lediju

2017-04-01

This work explores light delivery optimization for photoacoustic-guided minimally invasive surgeries, such as the endonasal transsphenoidal approach. Monte Carlo simulations were employed to study three-dimensional light propagation in tissue, comprising one or two 4-mm diameter arteries located 3 mm below bone, an absorbing metallic drill contacting the bone surface, and a single light source placed next to the 2.4-mm diameter drill shaft with a 2.9-mm diameter spherical drill tip. The optimal fiber distance from the drill shaft was determined from the maximum normalized fluence to the underlying artery. Using this optimal fiber-to-drill shaft distance, Zemax simulations were employed to propagate Gaussian beams through one or more 600 micron-core diameter optical fibers for detection on the bone surface. When the number of equally spaced fibers surrounding the drill increased, a single merged optical profile formed with seven or more fibers, determined by thresholding the resulting light profile images at 1/e times the maximum intensity. We used these simulations to inform design requirements, build a one to seven multifiber light delivery prototype to surround a surgical drill, and demonstrate its ability to simultaneously visualize the tool tip and blood vessel targets in the absence and presence of bone. The results and methodology are generalizable to multiple interventional photoacoustic applications.

Robust optical fiber patch-cords for in vivo optogenetic experiments in rats.

PubMed

Trujillo-Pisanty, Ivan; Sanio, Christian; Chaudhri, Nadia; Shizgal, Peter

2015-01-01

In vivo optogenetic experiments commonly employ long lengths of optical fiber to connect the light source (commonly a laser) to the optical fiber implants in the brain. Commercially available patch cords are expensive and break easily. Researchers have developed methods to build these cables in house for in vivo experiments with rodents [1-4]. However, the half-life of those patch cords is greatly reduced when they are used with behaving rats, which are strong enough to break the delicate cable tip and to bite through the optical fiber and furcation tubing. Based on [3] we have strengthened the patch-cord tip that connects to the optical implant, and we have incorporated multiple layers of shielding to produce more robust and resistant cladding. Here, we illustrate how to build these patch cords with FC or M3 connectors. However, the design can be adapted for use with other common optical-fiber connectors. We have saved time and money by using this design in our optical self-stimulation experiments with rats, which are commonly several months long and last four to eleven hours per session. The main advantages are: •Long half-life.•Resistant to moderate rodent bites.•Suitable for long in vivo optogenetic experiments with large rodents.

Rational design and validation of a Tip60 histone acetyltransferase inhibitor

NASA Astrophysics Data System (ADS)

Gao, Chunxia; Bourke, Emer; Scobie, Martin; Famme, Melina Arcos; Koolmeister, Tobias; Helleday, Thomas; Eriksson, Leif A.; Lowndes, Noel F.; Brown, James A. L.

2014-06-01

Histone acetylation is required for many aspects of gene regulation, genome maintenance and metabolism and dysfunctional acetylation is implicated in numerous diseases, including cancer. Acetylation is regulated by histone acetyltransferases (HATs) and histone deacetylases and currently, few general HAT inhibitors have been described. We identified the HAT Tip60 as an excellent candidate for targeted drug development, as Tip60 is a key mediator of the DNA damage response and transcriptional co-activator. Our modeling of Tip60 indicated that the active binding pocket possesses opposite charges at each end, with the positive charges attributed to two specific side chains. We used structure based drug design to develop a novel Tip60 inhibitor, TH1834, to fit this specific pocket. We demonstrate that TH1834 significantly inhibits Tip60 activity in vitro and treating cells with TH1834 results in apoptosis and increased unrepaired DNA damage (following ionizing radiation treatment) in breast cancer but not control cell lines. Furthermore, TH1834 did not affect the activity of related HAT MOF, as indicated by H4K16Ac, demonstrating specificity. The modeling and validation of the small molecule inhibitor TH1834 represents a first step towards developing additional specific, targeted inhibitors of Tip60 that may lead to further improvements in the treatment of breast cancer.

Low power femtosecond tip-based nanofabrication with advanced control

NASA Astrophysics Data System (ADS)

Liu, Jiangbo; Guo, Zhixiong; Zou, Qingze

2018-02-01

In this paper, we propose an approach to enable the use of low power femtosecond laser in tip-based nanofabrication (TBN) without thermal damage. One major challenge in laser-assisted TBN is in maintaining precision control of the tip-surface positioning throughout the fabrication process. An advanced iterative learning control technique is exploited to overcome this challenge in achieving high-quality patterning of arbitrary shape on a metal surface. The experimental results are analyzed to understand the ablation mechanism involved. Specifically, the near-field radiation enhancement is examined via the surface-enhanced Raman scattering effect, and it was revealed the near-field enhanced plasma-mediated ablation. Moreover, silicon nitride tip is utilized to alleviate the adverse thermal damage. Experiment results including line patterns fabricated under different writing speeds and an "R" pattern are presented. The fabrication quality with regard to the line width, depth, and uniformity is characterized to demonstrate the efficacy of the proposed approach.

Deep turbulence effects mitigation with coherent combining of 21 laser beams over 7 km.

PubMed

Weyrauch, Thomas; Vorontsov, Mikhail; Mangano, Joseph; Ovchinnikov, Vladimir; Bricker, David; Polnau, Ernst; Rostov, Andrey

2016-02-15

We demonstrate coherent beam combining and adaptive mitigation of atmospheric turbulence effects over 7 km under strong scintillation conditions using a coherent fiber array laser transmitter operating in a target-in-the-loop setting. The transmitter system is composed of a densely packed array of 21 fiber collimators with integrated capabilities for piston, tip, and tilt control of the outgoing beams wavefront phases. A small cat's-eye retro reflector was used for evaluation of beam combining and turbulence compensation performance at the target plane, and to provide the feedback signal for control of piston and tip/tilt phases of the transmitted beams using the stochastic parallel gradient descent maximization of the power-in-the-bucket metric.

An Optical Actuation System and Curvature Sensor for a MR-compatible Active Needle

PubMed Central

Ryu, Seok Chang; Quek, Zhan Fan; Renaud, Pierre; Black, Richard J.; Daniel, Bruce L.; Cutkosky, Mark R.

2015-01-01

A side optical actuation method is presented for a slender MR-compatible active needle. The needle includes an active region with a shape memory alloy (SMA) wire actuator, where the wire generates a contraction force when optically heated by a laser delivered though optical fibers, producing needle tip bending. A prototype, with multiple side heating spots, demonstrates twice as fast an initial response compared to fiber tip heating when 0.8 W of optical power is applied. A single-ended optical sensor with a gold reflector is also presented to measure the curvature as a function of optical transmission loss. Preliminary tests with the sensor prototype demonstrate approximately linear response and a repeatable signal, independent of the bending history. PMID:26509099

A damage tolerance comparison of IM7/8551 and IM8G/8553 carbon/epoxy composites

NASA Technical Reports Server (NTRS)

Lance, D. G.; Nettles, A. T.

1991-01-01

A damage tolerance study of two new toughened carbon fiber/epoxy resin systems was undertaken as a continuation of ongoing work into screening new opposites for resistance to foreign object impact. This report is intended to be a supplement to NASA TP 3029 in which four new fiber/resin systems were tested for damage tolerance. Instrumented drop weight impact testing was used to inflict damage to 16-ply quasi-isotropic specimens. Instrumented output data and cross-sectional examinations of the damage zone were utilized to quantify the damage. It was found that the two fiber/resin systems tested in this study were much more impact resistant than an untoughened composite such as T300/934, but were not as impact resistant as other materials previously studied.

Global Failure Modes in Composite Structures

NASA Technical Reports Server (NTRS)

Knauss, W. G.; Gonzalez, Luis

2001-01-01

Composite materials provide well-known advantages for space and aeronautical applications in terms of strength and rigidity to weight ratios and other mechanical properties. As a consequence, their use has experienced a constant increase in the past decades and it is anticipated that this trend will be maintained in the near future. At the same time, being these materials relatively new compared to metals, and having failure characteristics completely different from them, their damage growth and their failure mechanisms are not as well understood in a predictive sense. For example, while in metals fracture produces "clean" cracks with their well defined analytically stress fields at the crack tip, composite fracture is a more complex phenomenon. Instead of a crack, we confront a "damage zone" that may include fiber breakage, fiber microbuckling, fiber pullout, matrix cracking, delamination, debonding or any combination of all these different mechanisms. These phenomena are prevalent in any failure process through an aircraft structure, whether one addresses a global failure such as the ripping of a fuselage or wing section, or whether one is concerned with the failure initiation near a thickness change at stringers or other reinforcement. Thus the topic that has been under consideration has wide application in any real structure and is considered an essential contribution to the predictive failure analysis capability for aircraft containing composite components. The heterogeneity and the anisotropy of composites are not only advantageous but essential characteristics, yet these same features provide complex stress fields, especially in the presence of geometrical discontinuities such as notches, holes or cutouts or structural elements such as stiffeners, stringers, etc. To properly address the interaction between a damage/crack front and a hole with a stringer it is imperative that the stress and deformation fields of the former be (sufficiently well) characterized. The question of "scaling" is an essential concern in any structural materials investigation. For example, experiments in the past have shown that the "strength" of a composite depends on hole size. As a consequence the validity of traditional fracture mechanics concepts applied to composite materials failure must be questioned. The size of the fibers, the dimensions of the laminae, etc. together with the fact that, because of the layered anisotropy, the stress field is no longer two-dimensional, prevent the otherwise obviously confident use of "similarity concepts". Therefore, the question needs to be raised of whether in composites "size matters or not", i.e., whether the results obtained in a laboratory using small coupons are truly representative of the situation involving a full scale component.

Squirrel Damage to Pines

Treesearch

USDA Forest Service

1981-01-01

Flagging (dead branch tips) on jack pine and red pine may be caused by insects, diseases, or mechanical damage. In the Lake States, flagging is often the result of mechanical damage, sometimes girdling, caused when the cones are torn off by red squirrels.

Light intensity of curved laryngoscope blades in Philadelphia emergency departments.

PubMed

Levitan, Richard M; Kelly, John J; Kinkle, William C; Fasano, Charles

2007-09-01

Laryngoscopy and tracheal intubation requires laryngeal exposure and illumination. The objective of this study is to assess variation in laryngoscope lights across different emergency departments (EDs). A convenience sample of 3 Mac #4 blade and handle pairs in each of 17 Philadelphia area EDs was tested with a digital light meter to derive the median lux at the distal tip. For each blade tested, we characterized blade design (American, English, or German) and light type (fiber-illuminated versus conventional bulb-on-blade) and measured light-to-tip distance. A total of 50 blades and handle pairs were tested (one ED had only 2 Mac #4 blades). American designs were the most common (38/50), followed by English (6/50) and German (3/50) designs. Three blades had hybrid design features and acrylic light-conducting fibers. Median luminance varied from 11 lux to 5,627 lux. The glass fiber-illuminated blades (n=13) produced greater luminance (median 1,205 lux; interquartile range [IQR] 726 to 2,176 lux) than bulb-on-blade designs (median 689 lux; IQR 290 to 906 lux). German fiber-illuminated blades produced the highest luminance (median 1,937 lux; IQR 1,453 to 3,782 lux). English bulb-on-blade designs produced more luminance (median 915 lux; IQR 745 to 1270 lux) than American (median 689 lux; IQR 269 to 807 lux). German and English blades had shorter light-to-tip distances (median 51 mm and 47 mm, respectively) than American blades (65 mm). Curved laryngoscope blades in different EDs have marked variation in light intensity. The contribution of luminance to laryngoscopy performance warrants investigation.

Effect of stacking angles on mechanical properties and damage propagation of plain woven carbon fiber laminates

NASA Astrophysics Data System (ADS)

Zhuang, Weimin; Ao, Wenhong

2018-03-01

Damage propagation induced failure is a predominant damage mechanism. This study is aimed at assessing the damage state and damage propagation induced failure with different stacking angles, of woven carbon fiber/epoxy laminates subjected to quasi-static tensile and bending load. Different stages of damage processing and damage behavior under the bending load are investigated by Scanning Electron Microscopy (SEM). The woven carbon fiber/epoxy laminates which are stacked at six different angles (0°, 15°, 30°, 45°, 60°, 75°) with eight plies have been analyzed: [0]8, [15]8, [30]8, [45]8, [60]8, [75]8. Three-point bending test and quasi-static tensile test are used in validating the woven carbon fiber/epoxy laminates’ mechanical properties. Furthermore, the damage propagation and failure modes observed under flexural loading is correlated with flexural force and load-displacement behaviour respectively for the laminates. The experimental results have indicated that [45]8 laminate exhibits the best flexural performance in terms of energy absorption duo to its pseudo-ductile behaviour but the tensile strength and flexural strength drastically decreased compared to [0]8 laminate. Finally, SEM micrographs of specimens and fracture surfaces are used to reveal the different types of damage of the laminates with different stacking angles.

Fatigue damage development of various CFRP-laminates

NASA Technical Reports Server (NTRS)

Schulte, K.; Baron, CH.

1988-01-01

The chronic strength and fatigue behavior of a woven carbon-fiber reinforced laminate in a balanced eight-shaft satin weave style was compared to nonwoven laminates with an equivalent cross-ply layup. Half the fibers were arranged in the direction of the load and the other half perpendicular to it. Two types of nonwoven laminates consisting of continuous fibers and aligned discontinuous fibers, both produced from carbon fiber prepregs, were studied. The cross-ply laminate with continuous fiber showed the best characteristics with regard to both static strength and fatigue. The similarities and differences in damage mechanisms in the laminates are described.

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

NASA Astrophysics Data System (ADS)

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

2017-04-01

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

Isothermal Damage and Fatigue Behavior of SCS-6/Timetal 21S [0/90](Sub S) Composite at 650 Deg C

NASA Technical Reports Server (NTRS)

Castelli, Michael G.

1994-01-01

The isothermal fatigue damage and life behaviors of SCS-6/Timetal 21S (0/90)s were investigated at 650 C. Strain ratcheting and degradation of the composite's static elastic modulus were carefully monitored as functions of cycles to indicate damage progression. Extensive fractographic and metallographic analyses were conducted to determine damage/failure mechanisms. Resulting fatigue lives show considerable reductions in comparison to (0) reinforced titanium matrix composites subjected to comparable conditions. Notable stiffness degradations were found to occur after the first cycle of loading, even at relatively low maximum stress levels, where cyclic lives are greater than 25,000 cycles. This was attributed to the extremely weak fiber/matrix bond which fails under relatively low transverse loads. Stiffness degradations incurred on first cycle loadings and degradations thereafter were found to increase with increasing maximum stress. Environmental effects associated with oxidation of the (90) fiber interfaces clearly played a role in the damage mechanisms as fracture surfaces revealed environment assisted matrix cracking along the (90) fibers. Metallographic analysis indicated that all observable matrix fatigue cracks initiated at the (90) fiber/matrix interfaces. Global de-bonding in the loading direction was found along the (90) fibers. No surface initiated cracks were evident and minimal if any (0) fiber cracking was visible.

Self-Reporting Fiber-Reinforced Composites That Mimic the Ability of Biological Materials to Sense and Report Damage.

PubMed

Rifaie-Graham, Omar; Apebende, Edward A; Bast, Livia K; Bruns, Nico

2018-05-01

Sensing of damage, deformation, and mechanical forces is of vital importance in many applications of fiber-reinforced polymer composites, as it allows the structural health and integrity of composite components to be monitored and microdamage to be detected before it leads to catastrophic material failure. Bioinspired and biomimetic approaches to self-sensing and self-reporting materials are reviewed. Examples include bruising coatings and bleeding composites based on dye-filled microcapsules, hollow fibers, and vascular networks. Force-induced changes in color, fluorescence, or luminescence are achieved by mechanochromic epoxy resins, or by mechanophores and force-responsive proteins located at the interface of glass/carbon fibers and polymers. Composites can also feel strain, stress, and damage through embedded optical and electrical sensors, such as fiber Bragg grating sensors, or by resistance measurements of dispersed carbon fibers and carbon nanotubes. Bioinspired composites with the ability to show autonomously if and where they have been damaged lead to a multitude of opportunities for aerospace, automotive, civil engineering, and wind-turbine applications. They range from safety features for the detection of barely visible impact damage, to the real-time monitoring of deformation of load-bearing components. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

NASA Astrophysics Data System (ADS)

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

2006-08-01

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

Lab-on-Fiber biosensing for cancer biomarker detection

NASA Astrophysics Data System (ADS)

Ricciardi, A.; Severino, R.; Quero, G.; Carotenuto, B.; Consales, M.; Crescitelli, A.; Esposito, E.; Ruvo, M.; Sandomenico, A.; Borriello, A.; Giordano, M.; Sansone, L.; Granata, Carmine; Cutolo, A.; Cusano, A.

2015-09-01

This work deals with a novel Lab-on-Fiber biosensor able to detect in real time thyroid carcinomas biomarkers. The device is based on a gold nanostructure supporting localized surface plasmon resonances (LSPR) directly fabricated on the fiber tip by means of electron beam lithography and lift-off process. Following a suitable chemical and biological functionalization of the sensing area, human Thyroglobulin has been detected at nanomolar concentrations. Also, compatibility with full baseline restoration, achieved through biomarkers/bioreceptors dissociation, has been demonstrated.

Even Illumination from Fiber-Optic-Coupled Laser Diodes

NASA Technical Reports Server (NTRS)

Howard, Richard T.

2006-01-01

A method of equipping fiber-optic-coupled laser diodes to evenly illuminate specified fields of view has been proposed. The essence of the method is to shape the tips of the optical fibers into suitably designed diffractive optical elements. One of the main benefits afforded by the method would be more nearly complete utilization of the available light. Diffractive optics is a relatively new field of optics in which laser beams are shaped by use of diffraction instead of refraction.

Microfluidic flow rate detection based on integrated optical fiber cantilever.

PubMed

Lien, Victor; Vollmer, Frank

2007-10-01

We demonstrate an integrated microfluidic flow sensor with ultra-wide dynamic range, suitable for high throughput applications such as flow cytometry and particle sorting/counting. A fiber-tip cantilever transduces flow rates to optical signal readout, and we demonstrate a dynamic range from 0 to 1500 microL min(-1) for operation in water. Fiber-optic sensor alignment is guided by preformed microfluidic channels, and the dynamic range can be adjusted in a one-step chemical etch. An overall non-linear response is attributed to the far-field angular distribution of single-mode fiber output.

Simple refractometer based on in-line fiber interferometers

NASA Astrophysics Data System (ADS)

Esteban, Ó.; Martínez Manuel, R.; Shlyagin, M. G.

2015-09-01

A very simple but accurate optical fiber refractometer based on the Fresnel reflection in the fiber tip and two in-line low-reflective mirrors for light intensity referencing is reported. Each mirror was generated by connecting together 2 fiber sections with FC/PC and FC/APC connectors using the standard FC/PC mating sleeve. For the sensor interrogation, a standard DFB diode laser pumped with a sawtooth-wave current was used. A resolution of 6 x 10-4 was experimentally demonstrated using different liquids. A simple sensor construction and the use of low cost components make the reported system interesting for many applications.

SiC Fibers and SiCf/SiC Ceramic Matrix Minicomposites Damage Behavior

NASA Technical Reports Server (NTRS)

Almansour, Amjad S.

2017-01-01

Silicon Carbide based Ceramic Matrix Composites (CMCs) are attractive materials for use in high-temperature applications in the aerospace industry. Performance and durability of CMCs depend on the properties of its constituents such as fibers and matrix. Therefore, CMCs constituents limitations and damage mechanisms are discussed and characterized in representative simulated application conditions and dominant damage mechanisms are identified at elevated temperatures. In this work, the initiation and evolution of damage in Hi-Nicalon type S fiber-reinforced minicomposites with different interphases thicknesses from different manufacturers were investigated employing several nondestructive evaluation techniques such as acoustic emission, electrical resistance and microscopy. Moreover, the tensile creep behavior of single Hi-Nicalon Type S SiC fibers were tested and characterized and creep parameters were extracted. Fibers creep tests were performed in air or vacuum at 1200-1482 C under high stresses. Creep parameters was then used in understanding load sharing and lifing of ceramic matrix minicomposites. Future work plans will be reviewed.

Modeling Strength Degradation of Fiber-Reinforced Ceramic-Matrix Composites Subjected to Cyclic Loading at Elevated Temperatures in Oxidative Environments

NASA Astrophysics Data System (ADS)

Longbiao, Li

2018-02-01

In this paper, the strength degradation of non-oxide and oxide/oxide fiber-reinforced ceramic-matrix composites (CMCs) subjected to cyclic loading at elevated temperatures in oxidative environments has been investigated. Considering damage mechanisms of matrix cracking, interface debonding, interface wear, interface oxidation and fibers fracture, the composite residual strength model has been established by combining the micro stress field of the damaged composites, the damage models, and the fracture criterion. The relationships between the composite residual strength, fatigue peak stress, interface debonding, fibers failure and cycle number have been established. The effects of peak stress level, initial and steady-state interface shear stress, fiber Weibull modulus and fiber strength, and testing temperature on the degradation of composite strength and fibers failure have been investigated. The evolution of residual strength versus cycle number curves of non-oxide and oxide/oxide CMCs under cyclic loading at elevated temperatures in oxidative environments have been predicted.

Evaluation of residual strength in the basalt fiber reinforced composites under impact damage

NASA Astrophysics Data System (ADS)

Kim, Yun-Hae; Lee, Jin-Woo; Moon, Kyung-Man; Yoon, Sung-Won; Baek, Tae-Sil; Hwang, Kwang-Il

2015-03-01

Composites are vulnerable to the impact damage by the collision as to the thickness direction, because composites are being manufactured by laminating the fiber. The understanding about the retained strength after the impact damage of the material is essential in order to secure the reliability of the structure design using the composites. In this paper, we have tried to evaluate the motion of the material according to the kinetic energy and potential energy and the retained strength after impact damage by testing the free fall test of the basalt fiber reinforced composite in the limelight as the environment friendly characteristic.

Hierarchical damage mechanisms in composite materials subjected to fatigue loadings

NASA Astrophysics Data System (ADS)

D'Amore, Alberto; Grassia, Luigi

2018-02-01

The strength degradation of fiber reinforced composites subjected to constant amplitude (CA) fatigue loadings can be described by a two-parameter residual strength model. From the analytical approach it results that under moderate loadings the multiple damage mechanisms develop with different kinetics and manifest their effectiveness at different time scales highlighting the three-Stage hierarchical nature of damage accumulation in composites. The model captures the sequence of damage accumulation mechanisms from diffuse matrix cracking (I), to fiber/matrix interface failure (II) to fiber and ply rupture and delamination (III). Further, by increasing the loading severity it appears that the different mechanisms superpose witnessing their simultaneous co-existence.

Design and optimization of a flexible high-peak-power laser-to-fiber coupled illumination system used in digital particle image velocimetry

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

Robinson, Ronald A.; Ilev, Ilko K.

We present a study on the design and parameter optimization of a flexible high-peak-power fiber-optic laser delivery system using commercially available solid-core silica fibers and an experimental glass hollow waveguide (HW). The fiber-optic delivery system provides a flexible, safe, and easily and precisely positioned laser irradiation for many applications including uniform illumination for digital particle image velocimetry (DPIV). The delivery fibers, when coupled through a line-generating lens, produce a uniform thin laser sheet illumination for accurate and repeatable DPIV two-dimensional velocity measurements. We report experimental results on homogenizing the laser beam profile using various mode-mixing techniques. Furthermore, because a fundamentalmore » problem for fiber-optic-based high-peak-power laser delivery systems is the possible damage effects of the fiber material, we determine experimentally the peak power density damage threshold of various delivery fibers designed for the visible spectral range at a typical DPIV laser wavelength of 532 nm. In the case of solid-core silica delivery fibers using conventional lens-based laser-to-fiber coupling, the damage threshold varies from 3.7 GW/cm{sup 2} for a 100-{mu}m-core-diameter high-temperature fiber to 3.9 GW/cm{sup 2} for a 200-{mu}m-core-diameter high-power delivery fiber, with a total output laser energy delivered of at least 3-10 mJ for those respective fibers. Therefore, these fibers are marginally suitable for most macro-DPIV applications. However, to improve the high-power delivery capability for close-up micro-DPIV applications, we propose and validate an experimental fiber link with much higher laser power delivery capability than the solid-core fiber links. We use an uncoated grazing-incidence-based tapered glass funnel coupled to a glass HW with hollow air-core diameter of 700 {mu}m, a low numerical aperture of 0.05, and a thin inside cladding of cyclic olefin polymer coating for optimum transmission at 532 nm. Because of the mode homogenizing effect and lower power density, the taper-waveguide laser delivery technique ensured high damage threshold for the delivery HW, and as a result, no damage occurred at the maximum measured input laser energy of 33 mJ used in this study.« less

Intermediate Temperature Stress Rupture of a Woven Hi-Nicalon, BN-Interphase, SiC Matric Composite in Air

NASA Technical Reports Server (NTRS)

Morscher, Gregory N.; Hurst, Janet; Brewer, David

1999-01-01

Woven Hi-Nicalon (TM) reinforced melt-infiltrated SiC matrix composites were tested under tensile stress-rupture conditions in air at intermediate temperatures. A comprehensive examination of the damage state and the fiber properties at failure was performed. Modal acoustic emission analysis was used to monitor damage during the experiment. Extensive microscopy of the composite fracture surfaces and the individual fiber fracture surfaces was used to determine the mechanisms leading to ultimate failure. The rupture properties of these composites were significantly worse than expected compared to the fiber properties under similar conditions. This was due to the oxidation of the BN interphase. Oxidation occurred through the matrix cracks that intersected the surface or edge of a tensile bar. These oxidation reactions resulted in minor degradation to fiber strength and strong bonding of the fibers to one another at regions of near fiber-to-fiber contact. It was found that two regimes for rupture exist for this material: a high stress regime where rupture occurs at a fast rate and a low stress regime where rupture occurs at a slower rate. For the high stress regime, the matrix damage state consisted of through thickness cracks. The average fracture strength of fibers that were pulled-out (the final fibers to break before ultimate failure) was controlled by the slow-crack growth rupture criterion in the literature for individual Hi-Nicalon (TM) fibers. For the low stress regime, the matrix damage state consisted of microcracks which grew during the rupture test. The average fracture strength of fibers that were pulled-out in this regime was the same as the average fracture strength of individual fibers pulled out in as-produced composites tested at room temperature.

Laser pulse transmission and damage threshold of silica fibers with antireflective coatings

NASA Astrophysics Data System (ADS)

Meister, Stefan; Wosniok, Alexander; Riesbeck, Thomas; Scharfenorth, Chris; Eichler, Hans J.

2005-03-01

Standard 200 μm multimode fibers with Ta2O5/SiO2 antireflective coatings reach a transmission of more than 99.5% below the threshold of stimulated Brillouin scattering. The laser-induced damage threshold measured at 1064 nm and 24 ns pulse duration was about half than the LIDT of uncoated fibers.

Microshell-tipped optical fibers as sensors of high-pressure pulses in adverse environments

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

Benjamin, R.F.; Mayer, F.J.; Maynard, R.L.

1984-01-01

An optical-fiber sensor for detecting the arrival of strong pressure pulses was developed. The sensor consists of an optical fiber, tipped with a gas-filled microballoon. They have been used successfully in adverse environments including explosives, ballistics and electromagnetic pulses (EMP). The sensor produces a bright optical pulse caused by the rapid shock-heating of a gas, typically argon or xenon, which is confined in the spherical glass or plastic microballoon. The light pulse is transmitted via the optical fiber to a photo detector, usually a streak camera or photomultiplier tube. The microballoon optical sensor (called an optical pin by analogy tomore » standard electrical pins), was originally developed for diagnosing an explosive, pulsed-power generator. Optical pins are required due to the EMP. The optical pins are economical arrival-time indicators because many channels can be recorded by one streak camera. The generator tests and related experiments, involving projectile velocities and detonation velocities of several kilometers per sec have demonstrated the usefulness of the sensors in explosives and ballistics applications. The technical and cost advantages of this optical pin make it potentially useful for many electromagnetic, explosive, and ballistics applications.« less

A low-cost, computer-interfaced drawing pad for FMRI studies of dysgraphia and dyslexia.

PubMed

Reitz, Frederick; Richards, Todd; Wu, Kelvin; Boord, Peter; Askren, Mary; Lewis, Thomas; Berninger, Virginia

2013-04-17

We have developed a pen and writing tablet for use by subjects during fMRI scanning. The pen consists of two jacketed, multi-mode optical fibers routed to the tip of a hollowed-out ball-point pen. The pen has been further modified by addition of a plastic plate to maintain a perpendicular pen-tablet orientation. The tablet is simply a non-metallic frame holding a paper print of continuously varying color gradients. The optical fibers are routed out of the MRI bore to a light-tight box in an adjacent control room. Within the box, light from a high intensity LED is coupled into one of the fibers, while the other fiber abuts a color sensor. Light from the LED exits the pen tip, illuminating a small spot on the tablet, and the resulting reflected light is routed to the color sensor. Given a lookup table of position for each color on the tablet, the coordinates of the pen on the tablet may be displayed and digitized in real-time. While simple and inexpensive, the system achieves sufficient resolution to grade writing tasks testing dysgraphic and dyslexic phenomena.

Optical fiber sensors technology for supervision, control and protection of high power systems

NASA Astrophysics Data System (ADS)

Nascimento, Ivo Maciel

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Analysis of Plasmonics Based Fiber Optic Sensing Structures

NASA Astrophysics Data System (ADS)

Moayyed, Hamed

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Fiber sensing based on new structures and post-processing enhancement

NASA Astrophysics Data System (ADS)

Ferreira, Marta Sofia dos Anjos

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Optical Sensing: Fiber Structures and Interrogation Techniques

NASA Astrophysics Data System (ADS)

Carvalho, Joel Pedro

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Fiber optic structures for refractive index and gas sensing

NASA Astrophysics Data System (ADS)

Silva, Susana Ferreira de Oliveira

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Fractography of composite delamination

NASA Technical Reports Server (NTRS)

Bascom, W. D.

1990-01-01

The microdamage that occurs for Mode 1 and Mode 2 delamination was examined by potting delaminated specimens in a clear epoxy, sectioning through the damage, polishing the cut sections and examining using light microscopy. For Mode 1 delamination of unidirectional carbon fiber reinforced plastic (CFRP) composites, the major observation was fiber bridging including large ligaments of fiber bundles. The Mode 2 delamination of unidirectional laminates revealed a very narrow crack opening with only occasional fiber bridging. Impact testing by repetitive impacts with increasing energy was studied and it was found that this technique does not discern changes in the type of damage with increasing cumulative impact energy. Instead, the changes in the impact response, notably stiffness, are the result of changes in the extent of damage. For laminates with a brittle thermoplastic matrix, 3501-6, there were distinct changes in stiffness that corresponded to the development of through the thickness damage and then to the extension of the damage to the specimen edges. For PEEK and polycarbonate, the changes in stiffness were not as abrupt as for the thermoset. None the less, the damage progressed in the same manner.

Small, Lightweight Inspection Robot With 12 Degrees Of Freedom

NASA Technical Reports Server (NTRS)

Lee, Thomas S.; Ohm, Timothy R.; Hayati, Samad

1996-01-01

Small serpentine robot weighs only 6 lbs. and has link diameter of 1.5 in. Designed to perform inspections. Multiple degrees of freedom enables it to reach around obstacles and through small openings into simple or complexly shaped confined spaces to positions where difficult or impossible to perform inspections by other means. Fiber-optic borescope incorporated into robot arm, with inspection tip of borescope located at tip of arm. Borescope both conveys light along robot arm to illuminate scene inspected at tip and conveys image of scene back along robot arm to external imaging equipment.

Microscopy with multimode fibers

NASA Astrophysics Data System (ADS)

Moser, Christophe; Papadopoulos, Ioannis; Farahi, Salma; Psaltis, Demetri

2013-04-01

Microscopes are usually thought of comprising imaging elements such as objectives and eye-piece lenses. A different type of microscope, used for endoscopy, consists of waveguiding elements such as fiber bundles, where each fiber in the bundle transports the light corresponding to one pixel in the image. Recently a new type of microscope has emerged that exploits the large number of propagating modes in a single multimode fiber. We have successfully produced fluorescence images of neural cells with sub-micrometer resolution via a 200 micrometer core multimode fiber. The method for achieving imaging consists of using digital phase conjugation to reproduce a focal spot at the tip of the multimode fiber. The image is formed by scanning the focal spot digitally and collecting the fluorescence point by point.

Means and methods for cytometric therapies

DOEpatents

Gillies, George T.; Fillmore, Helen; Broaddus, William C.; Evans, III, Boyd M.; Allison, Stephen W.

2013-03-26

A functionalized tip is incorporated into catheters for the cytometric delivery of cells into the brain and other body parts. For use in the brain, the tip forms part of a neurosurgical probe having a proximal end and a distal end. In addition to the functionalized tip, the probe has at least one cell slurry delivery lumen and a plurality of optical fibers configured along the probe, terminating in the tip to provide the photo-optical capability needed to monitor the viability and physiological behavior of the grafted cells as well as certain characteristics of the cellular environment. Details are also presented of the use of a neurocatheter having a cytometric tip of the type disclosed in the invention, as employed within the context of a feedback and control system for regulating the number of cells delivered to the brain of a patient.

Low velocity instrumented impact testing of four new damage tolerant carbon/epoxy composite systems

NASA Technical Reports Server (NTRS)

Lance, D. G.; Nettles, A. T.

1990-01-01

Low velocity drop weight instrumented impact testing was utilized to examine the damage resistance of four recently developed carbon fiber/epoxy resin systems. A fifth material, T300/934, for which a large data base exists, was also tested for comparison purposes. A 16-ply quasi-isotropic lay-up configuration was used for all the specimens. Force/absorbed energy-time plots were generated for each impact test. The specimens were cross-sectionally analyzed to record the damage corresponding to each impact energy level. Maximum force of impact versus impact energy plots were constructed to compare the various systems for impact damage resistance. Results show that the four new damage tolerant fiber/resin systems far outclassed the T300/934 material. The most damage tolerant material tested was the IM7/1962 fiber/resin system.

Ultrasonic Assessment of Impact-Induced Damage and Microcracking in Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Liaw, Benjamin; Villars, Esther; Delmont, Frantz; Bowles, Kenneth J. (Technical Monitor)

2001-01-01

The main objective of this NASA FAR project is to conduct ultrasonic assessment of impact-induced damage and microcracking in polymer matrix composites at various temperatures. It is believed that the proposed study of impact damage assessment on polymer matrix composites will benefit several NASA missions and current interests, such as ballistic impact testing of composite fan containment and high strain rate deformation modeling of polymer matrix composites. Impact-induced damage mechanisms in GLARE and ARALL fiber-metal laminates subject to instrumented drop-weight impacts at various temperatures were studied. GLARE and ARALL are hybrid composites made of alternating layers of aluminum and glass (for GLARE) and aramid- (for ARALL) fiber-reinforced epoxy. Damage in pure aluminum panels impacted by foreign objects was mainly characterized by large plastic deformation surrounding a deep penetration dent. On the other hand, plastic deformation in fiber-metal laminates was often not as severe although the penetration dent was still produced. The more stiff fiber-reinforced epoxy layers provided better bending rigidity; thus, enhancing impact damage tolerance. Severe cracking, however, occurred due to the use of these more brittle fiber-reinforced epoxy layers. Fracture patterns, e.g., crack length and delamination size, were greatly affected by the lay-up configuration rather than by the number of layers, which implies that thickness effect was not significant for the panels tested in this study. Immersion ultrasound techniques were then used to assess damages generated by instrumented drop-weight impacts onto these fiber-metal laminate panels as well as 6061-T6 aluminum/cast acrylic sandwich plates adhered by epoxy. Depending on several parameters, such as impact velocity, mass, temperature, laminate configuration, sandwich construction, etc., various types of impact damage were observed, including plastic deformation, radiating cracks emanating from the impact site, ring cracks surrounding the impact site, partial and full delamination, and combinations of these damages.

Brain MRI fiber-tracking reveals white matter alterations in hypertensive patients without damage at conventional neuroimaging.

PubMed

Carnevale, Lorenzo; D'Angelosante, Valentina; Landolfi, Alessandro; Grillea, Giovanni; Selvetella, Giulio; Storto, Marianna; Lembo, Giuseppe; Carnevale, Daniela

2018-06-12

Hypertension is one of the main risk factor for dementia. The subtle damage provoked by chronic high blood pressure in the brain is usually evidenced by conventional magnetic resonance imaging (MRI), in terms of white matter (WM) hyperintensities or cerebral atrophy. However, it is clear that by the time brain damage is visible, it may be too late hampering neurodegeneration. Aim of this study was to characterize a signature of early brain damage induced by hypertension, before the neurodegenerative injury manifests. This work was conducted on hypertensive and normotensive subjects with no sign of structural damage at conventional neuroimaging and no diagnosis of dementia revealed by neuropsychological assessment. All individuals underwent cardiological clinical examination in order to define the hypertensive status and the related target organ damage. Additionally, patients were subjected to DTI-MRI scan to identify microstructural damage of WM by probabilistic fiber-tracking. To gain insights in the neurocognitive profile of patients a specific battery of tests was administered. As primary outcome of the study we aimed at finding any specific signature of fiber-tracts alterations in hypertensive patients, associated with an impairment of the related cognitive functions. Hypertensive patients showed significant alterations in three specific WM fiber-tracts: the anterior thalamic radiation, the superior longitudinal fasciculus and the forceps minor. Hypertensive patients also scored significantly worse in the cognitive domains ascribable to brain regions connected through those WM fiber-tracts, showing decreased performances in executive functions, processing speed, memory, and paired associative learning tasks. Overall, WM fiber-tracking on MRI evidenced an early signature of damage in hypertensive patients when otherwise undetectable by conventional neuroimaging. In perspective, this approach could allow identifying those patients that are in initial stages of brain damage and could benefit of therapies aimed at limiting the transition to dementia and neurodegeneration.

DDT spray for control of the ponderosa pine tip moth (Rhyacionia zozana [Kearfott])

Treesearch

Robert E. Stevens

1965-01-01

A water emulsion spray of DDT applied by hand sprayer to young trees infested with eggs and early-instar larvae of the ponderosa pine tip moth halted further larval activity and effectively prevented all damage.

Vis- and NIR-based instruments for detection of black-tip damaged wheat kernels: A comparative study

USDA-ARS?s Scientific Manuscript database

Black-tip (BT) present in wheat kernels is a non-mycotoxic fungus that attacks the kernels wherein any of a number of molds forms a dark brown or black sooty mold at the tip of the wheat kernel. Three spectrometers covering the spectral ranges 950-1636nm (Spec1), 600-1045nm (Spec2), and 380-780nm (S...

Optical Sensing using Fiber Bragg Gratings for Monitoring Structural Damage in Composite Over-Wrapped Vessels

NASA Technical Reports Server (NTRS)

Grant, Joseph

2005-01-01

Composite Over-Wrap Vessels are widely used in the aerospace community. They are made of thin-walled bottles that are over wrapped with high strength fibers embedded in a matrix material. There is a strong drive to reduce the weight of space borne vehicles and thus pushes designers to adopt COPVs that are over wrapped with graphite fibers embedded in its epoxy matrix. Unfortunately, this same fiber-matrix configuration is more susceptible to impact damage than others and to make matters worse; there is a regime where impacts that damage the over wrap leave no visible scar on the COPV surface. In this paper FBG sensors are presented as a means of monitoring and detecting these types of damage. The FBG sensors are surface mounted to the COPVs and optically interrogated to explore the structural properties of these composite pressure vessels. These gratings optically inscribed into the core of a single mode fiber are used as a tool to monitor the stress strain relation in the composite matrix. The response of these fiber-optic sensors is investigated by pressurizing the cylinder up to its burst pressure of around 4500 psi. A Fiber Optic Demodulation System built by Blue Road Research, is used for interrogation of the Bragg gratings.

Synergistic Effects of Temperature, Oxidation and Multicracking Modes on Damage Evolution and Life Prediction of 2D Woven Ceramic-Matrix Composites under Tension-Tension Fatigue Loading

NASA Astrophysics Data System (ADS)

Longbiao, Li

2017-08-01

In this paper, the synergistic effects of temperature, oxidation and multicracking modes on damage evolution and life prediction in 2D woven ceramic-matrix composites (CMCs) have been investigated. The damage parameter of fatigue hysteresis dissipated energy and the interface shear stress were used to monitor the damage evolution inside of CMCs. Under cyclic fatigue loading, the fibers broken fraction was determined by combining the interface/fiber oxidation model, interface wear model and fibers statistical failure model at elevated temperature, based on the assumption that the fiber strength is subjected to two-parameter Weibull distribution and the load carried by broken and intact fibers satisfy the Global Load Sharing (GLS) criterion. When the broken fibers fraction approaches to the critical value, the composite fatigue fractures. The evolution of fatigue hysteresis dissipated energy, the interface shear stress and broken fibers fraction versus cycle number, and the fatigue life S-N curves of SiC/SiC at 1000, 1200 and 1300 °C in air and steam condition have been predicted. The synergistic effects of temperature, oxidation, fatigue peak stress, and multicracking modes on the evolution of interface shear stress and fatigue hysteresis dissipated energy versus cycle numbers curves have been analyzed.

Objective-lens-free Fiber-based Position Detection with Nanometer Resolution in a Fiber Optical Trapping System.

PubMed

Ti, Chaoyang; Ho-Thanh, Minh-Tri; Wen, Qi; Liu, Yuxiang

2017-10-13

Position detection with high accuracy is crucial for force calibration of optical trapping systems. Most existing position detection methods require high-numerical-aperture objective lenses, which are bulky, expensive, and difficult to miniaturize. Here, we report an affordable objective-lens-free, fiber-based position detection scheme with 2 nm spatial resolution and 150 MHz bandwidth. This fiber based detection mechanism enables simultaneous trapping and force measurements in a compact fiber optical tweezers system. In addition, we achieved more reliable signal acquisition with less distortion compared with objective based position detection methods, thanks to the light guiding in optical fibers and small distance between the fiber tips and trapped particle. As a demonstration of the fiber based detection, we used the fiber optical tweezers to apply a force on a cell membrane and simultaneously measure the cellular response.

Critical Coupling Between Optical Fibers and WGM Resonators

NASA Technical Reports Server (NTRS)

Matsko, Andrey; Maleki, Lute; Itchenko, Vladimir; Savchenkov, Anatoliy

2009-01-01

Two recipes for ensuring critical coupling between a single-mode optical fiber and a whispering-gallery-mode (WGM) optical resonator have been devised. The recipes provide for phase matching and aperture matching, both of which are necessary for efficient coupling. There is also a provision for suppressing intermodal coupling, which is detrimental because it drains energy from desired modes into undesired ones. According to one recipe, the tip of the single-mode optical fiber is either tapered in diameter or tapered in effective diameter by virtue of being cleaved at an oblique angle. The effective index of refraction and the phase velocity at a given position along the taper depend on the diameter (or effective diameter) and the index of refraction of the bulk fiber material. As the diameter (or effective diameter) decreases with decreasing distance from the tip, the effective index of refraction also decreases. Critical coupling and phase matching can be achieved by placing the optical fiber and the resonator in contact at the proper point along the taper. This recipe is subject to the limitation that the attainable effective index of refraction lies between the indices of refraction of the bulk fiber material and the atmosphere or vacuum to which the resonator and fiber are exposed. The other recipe involves a refinement of the previously developed technique of prism coupling, in which the light beam from the optical fiber is collimated and focused onto one surface of a prism that has an index of refraction greater than that of the resonator. Another surface of the prism is placed in contact with the resonator. The various components are arranged so that the collimated beam is focused at the prism/resonator contact spot. The recipe includes the following additional provisions:

1-mm catheterscope

NASA Astrophysics Data System (ADS)

Seibel, Eric J.

2008-02-01

Flexible endoscopes use one sensor element per display pixel. When diameter is reduced to the size of a catheter, there is a significant reduction in the number of pixels within the image. By placing a sub-millimeter microscanner at the tip of a catheter, image quality can be significantly improved. The microscanner consists of a 0.4 mm diameter piezoelectric tube with quadrant electrodes, surrounding a cantilevered singlemode optical fiber. At the distal end, the fiber microscanner is sealed with a 0.9 mm diameter lens assembly, creating a rigid length less than 10 mm at the tip of a highly flexible shaft. The cantilevered fiber is vibrated at the first mode of resonance for bending to generate a circular scan pattern. A spiral scan pattern is generated that constitutes an image frame by modulating the piezoelectric drive signals. By using a custom optical fiber at 80 microns cladding diameter, >10 KHz resonant scanning is achieved, resulting in a 30 Hz frame rate. Red (635 nm), green (532 nm), and blue (442 nm) laser light is scanned by coupling to the fiber scanner. The scanned illumination is detected in a non-confocal arrangement by having one or more optical fibers collecting the backscattered light at MHz pixel rates. Current 1-mm diameter catheterscopes generate 500-line images at maximum fields of view of 100 degrees and spatial resolutions of <20 microns with image zooming. Shaft length of four meters have been fabricated with flexibility of <10 mm bending radius to image previously inaccessible regions of the body.

A high sensitivity fiber optic macro-bend based gas flow rate transducer for low flow rates: Theory, working principle, and static calibration

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

Schena, Emiliano; Saccomandi, Paola; Silvestri, Sergio

2013-02-15

A novel fiber optic macro-bend based gas flowmeter for low flow rates is presented. Theoretical analysis of the sensor working principle, design, and static calibration were performed. The measuring system consists of: an optical fiber, a light emitting diode (LED), a Quadrant position sensitive Detector (QD), and an analog electronic circuit for signal processing. The fiber tip undergoes a deflection in the flow, acting like a cantilever. The consequent displacement of light spot center is monitored by the QD generating four unbalanced photocurrents which are function of fiber tip position. The analog electronic circuit processes the photocurrents providing voltage signalmore » proportional to light spot position. A circular target was placed on the fiber in order to increase the sensing surface. Sensor, tested in the measurement range up to 10 l min{sup -1}, shows a discrimination threshold of 2 l min{sup -1}, extremely low fluid dynamic resistance (0.17 Pa min l{sup -1}), and high sensitivity, also at low flow rates (i.e., 33 mV min l{sup -1} up to 4 l min{sup -1} and 98 mV min l{sup -1} from 4 l min{sup -1} up to 10 l min{sup -1}). Experimental results agree with the theoretical predictions. The high sensitivity, along with the reduced dimension and negligible pressure drop, makes the proposed transducer suitable for medical applications in neonatal ventilation.« less

Giant Pulse Phenomena in a High Gain Erbium Doped Fiber Amplifier

NASA Technical Reports Server (NTRS)

Li, Stephen X.; Merritt, Scott; Krainak, Michael A.; Yu, Anthony

2018-01-01

High gain Erbium Doped Fiber Amplifiers (EDFAs), while revolutionizing optical communications, remain vulnerable to optical damage when unseeded, e.g. due to nonlinear effects that produce random pulses with high peak power, i.e. giant pulses. Giant pulses can damage the components in a high gain EDFA or external components and systems coupled to the EDFA. We explore the conditions under which a reflective, polarization-maintaining (PM), core-pumped high gain EDFA generates giant pulses, provide details on conditions under which normal pulses evolve into giant pulses, and provide results on the transient effects of giant pulses on amplifier's fused-fiber couplers, an effect which we call Fiber Overload Induced Leakage (FOIL). While FOIL's effect on fused-fiber couplers is temporary, its damage to forward pump lasers in a high gain EDFA can be permanent.

Giant Pulse Phenomena in a High Gain Erbium Doped Fiber Amplifier

NASA Technical Reports Server (NTRS)

Li, Stephen X.; Merritt, Scott; Krainak, Michael A.; Yu, Anthony

2018-01-01

High gain Erbium Doped Fiber Amplifiers (EDFAs) are vulnerable to optical damage when unseeded, e.g. due to nonlinear effects that produce random, spontaneous Q-switched (SQS) pulses with high peak power, i.e. giant pulses. Giant pulses can damage either the components within a high gain EDFA or external components and systems coupled to the EDFA. We explore the conditions under which a reflective, polarization-maintaining (PM), core-pumped high gain EDFA generates giant pulses, provide details on the evolution of normal pulses into giant pulses, and provide results on the transient effects of giant pulses on an amplifier's fused-fiber couplers, an effect which we call Fiber Overload Induced Leakage (FOIL). While FOIL's effect on fused-fiber couplers is temporary, its damage to forward pump lasers in a high gain EDFA can be permanent.

Al2O3 fiber strength degradation in metal and intermetallic matrix composites

NASA Technical Reports Server (NTRS)

Draper, S. L.; Locci, I. E.

1994-01-01

The mechanisms for fiber damage in single crystal Al2O3 fiber-reinforced composites were investigated. Both fiber fragmentation and fiber strength degradation were observed in composites with a variety of matrix compositions. Four mechanisms that may be contributing to the fiber strength loss have been proposed and include matrix reaction, reaction with binders, residual stress-induced damage, and pressure from hot pressing. The effect of matrix reaction was separated from the other three effects by sputter-coating the matrices on cleaned fibers and annealing with a temperature profile that simulates processing conditions. These experiments revealed that Y and Cr in FeCrAlY base alloys and Zr in NiAl alloys reacted with the fiber, and grooves and adherent particles were formed on the fiber surface which were responsible for the strength loss. The effects of the matrix reaction appeared to dominate over the other possible mechanisms, although evidence for reaction with binders was also found. Ridges on the fiber surface, which reflected the grain boundaries of the matrix, were also observed. In order for single-crystal Al2O3 to be used as a fiber in MMC's and IMC's, a matrix or protective coating which minimizes matrix reaction during processing will be necessary. Of the matrices investigated, the Thermo-span(sup TM) alloy was the least damaging to fiber properties.

Disbond detection with piezoelectric wafer active sensors in RC structures strengthened with FRP composite overlays

NASA Astrophysics Data System (ADS)

Giurgiutiu, Victor; Harries, Kent; Petrou, Michael; Bost, Joel; Quattlebaum, Josh B.

2003-12-01

The capability of embedded piezoelectric wafer active sensors (PWAS) to perform in-situ nondestructive evaluation (NDE) for structural health monitoring (SHM) of reinforced concrete (RC) structures strengthened with fiber reinforced polymer (FRP) composite overlays is explored. First, the disbond detection method were developed on coupon specimens consisting of concrete blocks covered with an FRP composite layer. It was found that the presence of a disbond crack drastically changes the electromechanical (E/M) impedance spectrum measured at the PWAS terminals. The spectral changes depend on the distance between the PWAS and the crack tip. Second, large scale experiments were conducted on a RC beam strengthened with carbon fiber reinforced polymer (CFRP) composite overlay. The beam was subject to an accelerated fatigue load regime in a three-point bending configuration up to a total of 807,415 cycles. During these fatigue tests, the CFRP overlay experienced disbonding beginning at about 500,000 cycles. The PWAS were able to detect the disbonding before it could be reliably seen by visual inspection. Good correlation between the PWAS readings and the position and extent of disbond damage was observed. These preliminary results demonstrate the potential of PWAS technology for SHM of RC structures strengthened with FRP composite overlays.

Structural Mechanics of Thin-Ply Laminated Composites

NASA Astrophysics Data System (ADS)

Arteiro, Albertino

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Detection and Characterization of Defects in Composite Materials Using Thermography

NASA Astrophysics Data System (ADS)

Silva, Antonio Jose Ramos

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

PCM energy storage modelling: Case study for a solar-ejector cooling cycle

NASA Astrophysics Data System (ADS)

Allouche, Yosr

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

The relationship between heating energy use, indoor temperature and heating energy demand under reference conditions in residential buildings

NASA Astrophysics Data System (ADS)

Magalhaes, Sara Moreira Coelho de

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Decision support methodology for national energy planning in developing countries: an implementation focused approach

NASA Astrophysics Data System (ADS)

Lee, Nathan Coenen

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

High Resolution Satellite Image Analysis and Rapid 3D Model Extraction for Urban Change Detection

NASA Astrophysics Data System (ADS)

Abduelmola, Abdunaser E.

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Novel dual-colour architecture for ultrafast spin dynamics measurements in sub-8 fs regime

NASA Astrophysics Data System (ADS)

Goncalves, Cledson Santana Lopes

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Predictors of Attitudes and Knowledge of Students in PISA 2006: A Comparison Between Different Cultural Contexts

NASA Astrophysics Data System (ADS)

Tinnaworn, Piyathip

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Continuum Modelling and Numerical Simulation of Hexagonal Close-Packed Materials

NASA Astrophysics Data System (ADS)

Wu, Shenghua

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Development of chemo-sensing schemes based on analyte-triggered modulation of CdTe quantum dots photoluminescence for analytical purposes

NASA Astrophysics Data System (ADS)

Rodrigues, Sandra Sofia Mota

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

General Relativity in the framework of exact gravito-electromagnetic analogies

NASA Astrophysics Data System (ADS)

Costa, Luis Filipe

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Tirania-silica composite materials for self-cleaning applications on monumental stones

NASA Astrophysics Data System (ADS)

Pinho, Luis

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Provision of advanced ancillary services through demand side integration

NASA Astrophysics Data System (ADS)

Heleno, Miguel Luis Delgado

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Exoplanets: Gaia and the importance of spectroscopic follow-up

NASA Astrophysics Data System (ADS)

Benamati, Lisa

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Delivery of biomolecules by functionalized inorganic/organic nanoparticles

NASA Astrophysics Data System (ADS)

Coelho, Silvia Maria de Castro

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Development of fluorescent silica nanoparticles encapsulating organic and inorganic fluorophores; synthesis and characterization

NASA Astrophysics Data System (ADS)

Neves, Cristina Sofia dos Santos

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Kinematic GNSS Precise Point Positioning: Application to Marine Platforms

NASA Astrophysics Data System (ADS)

Marreiros, Joao Paulo Ramalho

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Biosensors for the detection and quantification of aquatic bacterial contamination in waters for human use

NASA Astrophysics Data System (ADS)

Queiros, Raquel Barbosa

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Galaxy Assembly through Mergers: Uncovering Dry and Non-dry Mergers in the SDSS

NASA Astrophysics Data System (ADS)

Brochado, Paula

2012-03-01

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

Computational Generation and Homogenization of Random Close Packed Materials

NASA Astrophysics Data System (ADS)

Miranda, H. David

The work described in this PhD Thesis focuses on the post-processing of optical fibers and their enhancement as sensing element. Since the majority of sensors presented are based in Fabry-Perot interferometers, an historical overview of this category of optical fiber sensors is firstly presented. This review considers the works published since the early years, in the beginning of the 1980s, until the middle of 2015. The incorporation of microcavities at the tip of a single mode fiber was extensively studied, particularly for the measurement of nitrogen and methane gas pressure. These cavities were fabricated using hollow core silica tubes and a hollow core photonic crystal fiber. Following a different approach, the microcavities were incorporated between two sections of single mode fiber. In this case, the low sensitivity to temperature makes these microcavities highly desirable for the measurement of strain at high temperatures. Competences in post-processing techniques such as the chemical etching and the writing of periodical structures in the fiber core by means of an excimer or a femtosecond laser were also acquired in the course of the PhD programme. One of the works consisted in the design and manufacturing of a double clad optical fiber. The refractive index of the inner cladding was higher than the one of the outer cladding and the core. Thus, light was guided in the inner cladding instead of propagating in the core. This situation was overcome by applying chemical etching, thus removing the inner cladding. The core, surrounded by air, was then able to guide light. Two different applications were found for this fiber, as a temperature sensor and as an optical refractometer. In the last, the optical phase changes with the liquid refractive index. Two different types of fiber Bragg gratings were characterized in strain and temperature. Sensing structures obtained through the phase mask technique at the tip of an optical fiber were subjected to chemical etching. In this case, an excimer laser was used. Extremely thin fiber tips were obtained, with an ultra-high sensitivity to strain. The other technique employed to fabricate the fiber Bragg gratings was the point-by-point femtosecond laser inscription. In this case, the sensing elements are very stable at high temperatures and can be used to measure strain in harsh conditions. The employment of optical fiber lasers as sensing elements was also considered in this Thesis. Two laser cavities were studied, one based on the ring configuration and the other based on a figure-of-eight configuration. From these works, the quality of the laser emission, namely the signal-to-noise ratio, the reduced full-width at half maximum and the stability should be highlighted. These characteristics allowed the measurement of different physical parameters, such as strain, temperature and torsion. Lastly, the possibility to use microspheres as sensing elements was considered. Using the electric arc of a fusion splicer, it is possible to create microspheres at the tip of an optical fiber. Furthermore, with this technique it is chains of microspheres can be obtained, constituting Mach-Zehnder-type interferometers which are sensitive to physical parameters like strain and temperature. The preliminary results obtained by introducing silica microspheres in a support structure are also presented. In this case, the sensors were subjected to temperature variations. All the experimental work was combined with the respective theoretical considerations. Many questions have been raised with the course of this PhD, and there are still some without a definite answer. Thus, new research paths can be followed, having their basis grounded in the configurations here presented.

FIBER OPTIC BIOSENSOR FOR DNA DAMAGE

EPA Science Inventory

This paper describes a fiber optic biosensor for the rapid and sensitive detection of radiation-induced or chemically-induced oxidative DNA damage. The assay is based on the hybridization and temperature-induced dissociation (melting curves) of synthetic oligonucleotides. The...

TU-CD-BRB-05: Radiation Damage Signature of White Matter Fiber Bundles Using Diffusion Tensor Imaging (DTI)

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

Zhu, T; Chapman, C; Lawrence, T

2015-06-15

Purpose: To develop an automated and scalable approach and identify temporal, spatial and dosimetric patterns of radiation damage of white matter (WM) fibers following partial brain irradiation. Methods: An automated and scalable approach was developed to extract DTI features of 22 major WM fibers from 33 patients with low-grade/benign tumors treated by radiation therapy (RT). DTI scans of the patients were performed pre-RT, 3- and 6-week during RT, and 1, 6 and 18 months after RT. The automated tractography analysis was applied to 198 datasets as: (1) intra-subject registration of longitudinal DTI, (2) spatial normalization of individual-patient DTI to themore » Johns Hopkins WM Atlas, (3) automatic fiber tracking regulated by the WM Atlas, and (4) segmentation of WM into 22 major tract profiles. Longitudinal percentage changes in fractional anisotropy (FA), and mean, axial and radial diffusivity (MD/AD/RD) of each tract from pre-RT were quantified and correlated to 95%, 90% and 80% percentiles of doses and mean doses received by the tract. Heatmaps were used to identify clusters of significant correlation and reveal temporal, spatial and dosimetric signatures of WM damage. A multivariate linear regression was further carried out to determine influence of clinical factors. Results: Of 22 tracts, AD/MD changes in 12 tracts had significant correlation with doses, especially at 6 and 18 months post-RT, indicating progressive radiation damage after RT. Most interestingly, the DTI-index changes in the elongated tracts were associated with received maximum doses, suggesting a serial-structure behavior; while short association fibers were affected by mean doses, indicating a parallel-structure response. Conclusion: Using an automated DTI-tractography analysis of whole brain WM fibers, we reveal complex radiation damage patterns of WM fibers. Damage in WM fibers that play an important role in the neural network could be associated with late neurocognitive function declines after brain irradiation. NIH NS064973.« less

Investigating of the Field Emission Performance on Nano-Apex Carbon Fiber and Tungsten Tips

NASA Astrophysics Data System (ADS)

Mousa, Marwan S.; Alnawasreh, Shadi; Madanat, Mazen A.; Al-Rabadi, Anas N.

2015-10-01

Field electron emission measurements have been performed on carbon-based and tungsten microemitters. Several samples of both types of emitters with different apex radii have been obtained employing electrolytic etching techniques using sodium hydroxide (NaOH) solution with different molarities depending on the material used. A suitable, home-built, field electron microscope (FEM) with 10 mm tip to screen separation distance was used to electrically characterize the electron emitters. Measurements were carried out under ultra high vacuum (UHV) conditions with base pressure of 10-9 mbar. The current-voltage characteristics (I-V) presented as Fowler-Nordheim (FN) type plots, and field electron emission images have been recorded. In this work, initial comparison of the field electron emission performance of these micro and nanoemitters has been carried out, with the aim of obtaining a reliable, stable and long life powerful electron source. We compare the apex radii measured from the micrographs obtained from the SEM images to those extracted from the FN-type _I-V_plots for carbon fibers and tungsten tips.

Laser and acoustic lens for lithotripsy

DOEpatents

Visuri, Steven R.; Makarewicz, Anthony J.; London, Richard A.; Benett, William J.; Krulevitch, Peter; Da Silva, Luiz B.

2002-01-01

An acoustic focusing device whose acoustic waves are generated by laser radiation through an optical fiber. The acoustic energy is capable of efficient destruction of renal and biliary calculi and deliverable to the site of the calculi via an endoscopic procedure. The device includes a transducer tip attached to the distal end of an optical fiber through which laser energy is directed. The transducer tip encapsulates an exogenous absorbing dye. Under proper irradiation conditions (high absorbed energy density, short pulse duration) a stress wave is produced via thermoelastic expansion of the absorber for the destruction of the calculi. The transducer tip can be configured into an acoustic lens such that the transmitted acoustic wave is shaped or focused. Also, compressive stress waves can be reflected off a high density/low density interface to invert the compressive wave into a tensile stress wave, and tensile stresses may be more effective in some instances in disrupting material as most materials are weaker in tension than compression. Estimations indicate that stress amplitudes provided by this device can be magnified more than 100 times, greatly improving the efficiency of optical energy for targeted material destruction.

A Hybrid Approach to Composite Damage and Failure Analysis Combining Synergistic Damage Mechanics and Peridynamics

DTIC Science & Technology

2016-09-30

far from uniform . The final nonuniform distribution of fibers consists of clustered regions and resin pockets. The clustered fiber regions promote...period. Approach and Results A novel procedure has been devised to create nonuniform fiber distributions from the initial fiber bundle (with...used in simulations to produce nonuniform configurations. 2 . , •• ... . .. ·~ · . .. 000 8oa~.f𔄂oo o0~&mt~ go ... ·~· %(1 "’ ,~o ooif-l /j

Photon theory hypothesis about photon tunneling microscope's subwavelength resolution

NASA Astrophysics Data System (ADS)

Zhu, Yanbin; Ma, Junfu

1995-09-01

The foundation for the invention of the photon scanning tunneling microscope (PSTM) are the near field scanning optical microscope, the optical fiber technique, the total internal reflection, high sensitive opto-electronic detecting technique and computer technique etc. Recent research results show the subwavelength resolution of 1 - 3 nm is obtained. How to explain the PSTM has got such high subwavelength resolution? What value is the PSTM's limiting of subwavelength resolution? For resolving these problems this paper presented a photon theory hypothesis about PSTM that is based on the following two basic laws: (1) Photon is not only a carrier bringing energy and optical information, but also is a particle occupied fixed space size. (2) When a photon happened reflection, refraction, scattering, etc., only changed its energy and optical information carried, its particle size doesn't change. g (DOT) pphoton equals constant. Using these two basic laws to PSTM, the `evanescent field' is practically a weak photon distribution field and the detecting fiber tip diameter is practically a `gate' which size controlled the photon numbers into fiber tip. Passing through some calculation and inference, the following three conclusions can be given: (1) Under the PSTM's detection system sensitivity is high enough, the diameter D of detecting fiber tip and the near field detecting distance Z are the two most important factors to decide the subwavelength resolution of PSTM. (2) The limiting of PSTM's resolution will be given upon the conditions of D equals pphoton and Z equals pphoton, where pphoton is one photon size. (2) The final resolution limit R of PSTM will be lim R equals pphoton, D yields pphoton, Z yields pphoton.

Application of carbon nanotubes to topographical resolution enhancement of tapered fiber scanning near field optical microscopy probes

NASA Astrophysics Data System (ADS)

Huntington, S. T.; Jarvis, S. P.

2003-05-01

Scanning near field optical microscopy (SNOM) probes are typically tapered optical fibers with metallic coatings. The tip diameters are generally in excess of 300 nm and thus provide poor topographical resolution. Here we report on the attachment multiwalled carbon nanotubes to the probes in order to substantially enhance the topographical resolution, without adversely affecting the optical resolution.

Cellular functions of TIP60.

PubMed

Sapountzi, Vasileia; Logan, Ian R; Robson, Craig N

2006-01-01

TIP60 was originally identified as a cellular acetyltransferase protein that interacts with HIV-1 Tat. As a consequence, the role of TIP60 in transcriptional regulation has been investigated intensively. Recent data suggest that TIP60 has more divergent functions than originally thought and roles for TIP60 in many processes, such as cellular signalling, DNA damage repair, cell cycle and checkpoint control and apoptosis are emerging. TIP60 is a tightly regulated transcriptional coregulator, acting in a large multiprotein complex for a range of transcription factors including androgen receptor, Myc, STAT3, NF-kappaB, E2F1 and p53. This usually involves recruitment of TIP60 acetyltransferase activities to chromatin. Additionally, in response to DNA double strand breaks, TIP60 is recruited to DNA lesions where it participates both in the initial as well as the final stages of repair. Here, we describe how TIP60 is a multifunctional enzyme involved in multiple nuclear transactions.

Four-probe measurements with a three-probe scanning tunneling microscope.

PubMed

Salomons, Mark; Martins, Bruno V C; Zikovsky, Janik; Wolkow, Robert A

2014-04-01

We present an ultrahigh vacuum (UHV) three-probe scanning tunneling microscope in which each probe is capable of atomic resolution. A UHV JEOL scanning electron microscope aids in the placement of the probes on the sample. The machine also has a field ion microscope to clean, atomically image, and shape the probe tips. The machine uses bare conductive samples and tips with a homebuilt set of pliers for heating and loading. Automated feedback controlled tip-surface contacts allow for electrical stability and reproducibility while also greatly reducing tip and surface damage due to contact formation. The ability to register inter-tip position by imaging of a single surface feature by multiple tips is demonstrated. Four-probe material characterization is achieved by deploying two tips as fixed current probes and the third tip as a movable voltage probe.

Stiffness degradation-based damage model for RC members and structures using fiber-beam elements

NASA Astrophysics Data System (ADS)

Guo, Zongming; Zhang, Yaoting; Lu, Jiezhi; Fan, Jian

2016-12-01

To meet the demand for an accurate and highly efficient damage model with a distinct physical meaning for performance-based earthquake engineering applications, a stiffness degradation-based damage model for reinforced concrete (RC) members and structures was developed using fiber beam-column elements. In this model, damage indices for concrete and steel fibers were defined by the degradation of the initial reloading modulus and the low-cycle fatigue law. Then, section, member, story and structure damage was evaluated by the degradation of the sectional bending stiffness, rod-end bending stiffness, story lateral stiffness and structure lateral stiffness, respectively. The damage model was realized in Matlab by reading in the outputs of OpenSees. The application of the damage model to RC columns and a RC frame indicates that the damage model is capable of accurately predicting the magnitude, position, and evolutionary process of damage, and estimating story damage more precisely than inter-story drift. Additionally, the damage model establishes a close connection between damage indices at various levels without introducing weighting coefficients or force-displacement relationships. The development of the model has perfected the damage assessment function of OpenSees, laying a solid foundation for damage estimation at various levels of a large-scale structure subjected to seismic loading.

Mitigation of tip vortex cavitation by means of air injection on a Kaplan turbine scale model

NASA Astrophysics Data System (ADS)

Rivetti, A.; Angulo, M.; Lucino, C.; Liscia, S.

2014-03-01

Kaplan turbines operating at full-load conditions may undergo excessive vibration, noise and cavitation. In such cases, damage by erosion associated to tip vortex cavitation can be observed at the discharge ring. This phenomenon involves design features such as (1) overhang of guide vanes; (2) blade profile; (3) gap increasing size with blade opening; (4) suction head; (5) operation point; and (6) discharge ring stiffness, among others. Tip vortex cavitation may cause erosion at the discharge ring and draft tube inlet following a wavy pattern, in which the number of vanes can be clearly identified. Injection of pressurized air above the runner blade centerline was tested as a mean to mitigate discharge ring cavitation damage on a scale model. Air entrance was observed by means of a high-speed camera in order to track the air trajectory toward its mergence with the tip vortex cavitation core. Post-processing of acceleration signals shows that the level of vibration and the RSI frequency amplitude decrease proportionally with air flow rate injected. These findings reveal the potential mitigating effect of air injection in preventing cavitation damage and will be useful in further tests to be performed on prototype, aiming at determining the optimum air flow rate, size and distribution of the injectors.

Micromechanical Fatigue Visco-Damage Model for Short Glass Fiber Reinforced Polyamide-66

NASA Astrophysics Data System (ADS)

Despringre, N.; Chemisky, Y.; Robert, G.; Meraghni, F.

This work presents a micromechanical fatigue damage model developed for short glass fiber reinforced PA66. It has been developed to predict the high cycle fatigue behavior of PA66/GF30. The model is based on an extended Mori-Tanaka method which includes coated inclusions, matrix viscoelasticity and the evolution of micro-scale damage. The developed model accounts for the nonlinear matrix viscoelasticity and the reinforcement orientation. The description of the damage processes is based on the experimental investigation of damage mechanisms previously performed through in-situ SEM tests and X-ray micro-computed tomography observations. Damage chronologies have been proposed involving three different processes: interface debonding/coating, matrix micro-cracking and fiber breakages. Their occurrence strongly depends on the microstructure and the relative humidity. Each damage mechanism is introduced through an evolution law coupled to local stress fields. The developed model is implemented using a UMAT subroutine. Its experimental validation is achieved under stress or strain controlled fatigue tests.

Friction and wear behavior of graphite fiber reinforced polymide composites

NASA Technical Reports Server (NTRS)

Fusaro, R. L.; Sliney, H. E.

1977-01-01

The friction and wear rate characteristics of 50/50 (weight percent) graphite fiber polyimide composites were studied by sliding metallic hemispherically tipped riders against disks made from the composites. Two different polyimides and two different graphite fibers were evaluated. Also studied were such variables as the effect of moisture in an air atmosphere; the effect of temperature; and the effect of different sliding speeds. In general, wear to the the metallic riders was negligible, and composite wear increased at a constant rate as a function of number of sliding cycles.

Computational Implementation of a Thermodynamically Based Work Potential Model For Progressive Microdamage and Transverse Cracking in Fiber-Reinforced Laminates

NASA Technical Reports Server (NTRS)

Pineda, Evan J.; Waas, Anthony M.; Bednarcyk, Brett A.; Collier, Craig S.

2012-01-01

A continuum-level, dual internal state variable, thermodynamically based, work potential model, Schapery Theory, is used capture the effects of two matrix damage mechanisms in a fiber-reinforced laminated composite: microdamage and transverse cracking. Matrix microdamage accrues primarily in the form of shear microcracks between the fibers of the composite. Whereas, larger transverse matrix cracks typically span the thickness of a lamina and run parallel to the fibers. Schapery Theory uses the energy potential required to advance structural changes, associated with the damage mechanisms, to govern damage growth through a set of internal state variables. These state variables are used to quantify the stiffness degradation resulting from damage growth. The transverse and shear stiffness of the lamina are related to the internal state variables through a set of measurable damage functions. Additionally, the damage variables for a given strain state can be calculated from a set of evolution equations. These evolution equations and damage functions are implemented into the finite element method and used to govern the constitutive response of the material points in the model. Additionally, an axial failure criterion is included in the model. The response of a center-notched, buffer strip-stiffened panel subjected to uniaxial tension is investigated and results are compared to experiment.

The Impact of a 940 nm Diode Laser with Radial Firing Tip and Bare End Fiber Tip on Enterococcus faecalis in the Root Canal Wall Dentin of Bovine Teeth: An In Vitro Study.

PubMed

Schulte-Lünzum, Ruth; Gutknecht, Norbert; Conrads, Georg; Franzen, Rene

2017-07-01

This in vitro study aimed to compare the bactericidal effect of two different laser delivery systems, a radial firing tip (RFT) and bare end fiber tip (BFT) used with the 940 nm diode laser on Enterococcus faecalis inoculated onto bovine radicular dentin. A total of 100 bovine dentin slices with a defined thickness of 500 and 1000 μm were prepared. They were assigned into four test groups together with untreated samples served as control for each slice thickness. The slices were inoculated on one side with 1 μL E. faecalis suspension and laser irradiation was performed indirectly on the opposite side with the 940 nm diode laser delivered with a 200 μm RFT and a BFT at 1 and 1.5 W in continuous wave mode for 8 sec per cycle and repeated four times. After irradiation, the remaining bacteria were detached and the produced suspension was diluted and plated onto blood agar plates with 5% sheep blood and incubated overnight at 37°C in a CO 2 -rich atmosphere. The colony-forming units of E. faecalis were counted and the bacterial reduction was analyzed. The diode laser equipped with RFT fiber design further reduced the number of vital E. faecalis cells significantly compared with BFT design, regardless of the used power and dentin thickness (p < 0.0001). The highest average value of 4 log kills was observed in 500 μm slice thickness irradiated with RFT at 1.5 W. Temperature measurements on the external root surface at 1 mm from the apex did not elicit a harmful temperature elevation in both power settings and fiber designs. Within the studied parameters, 940 nm diode laser in conjugation with RFT showed a satisfactory bactericidal effect without any thermal side effect to the tooth-supporting tissues.

Physics of light and lasers.

PubMed

Absten, G T

1991-09-01

Because most laser procedures use the heating effect of the light and given the number of parameters that may be varied--such as power density, power, pulsing, and heating of fiber tips and probes--significant overlap in applications of the various lasers can result. This is readily apparent in the conflicting claims of laser manufacturers seen in promotional materials. Despite this, each type has its strengths. The CO2 laser is a specialty instrument, particularly for microscopic applications in neurosurgery, otolaryngology, and gynecology. Its hemostasis and vaporizing abilities allow its use in dermatology and in general surgery for tumor resection and hemostasis. In gynecology it seems best for colposcopy (cervical and vaginal) and, through a micromanipulator, for laparotomy. The beam is focused and delivered by handpieces and micromanipulators on microscopes. Through the laparoscope, it requires the use of a special laser coupler on a special laser laparoscope to allow for line-of-sight delivery of the beam through the operating channel. Waveguide delivery systems have been introduced for CO2 laser laparoscopy using standard laparoscopes. These function as hollow, slender tubes through which the beam is transmitted by means of hundreds of glancing internal reflections in the tube, which emits the beam at its tip. This eliminates many of the alignment problems of coupler cube-type systems and allows the beam to be delivered close to the target. The Nd:YAG laser is the primary endoscopic instrument in pulmonology, gastroenterology, and urology. The use of contact tips, though not a panacea, increases its applications, particularly in general surgery. Its primary use in gynecology is for endometrial ablation with bare fibers for deep coagulation. Its use for laparoscopy with contact probes or sculpted fibers is quickly growing. Green light lasers (argon and KTP) are color-selective photocoagulators and may be used to cut tissue. They are fiberoptically delivered like the Nd:YAG laser. Their best use in gynecology appears to be a versatile instruments for operative laparoscopy and the simple treatment of endometriosis. A standard quartz fiber with these lasers is usually more versatile than a contact tip with an Nd:YAG laser when used for cutting.

Simultaneous life extension and crack monitoring of fatigue-damaged steel members using multifunctional carbon nanotube based composites

NASA Astrophysics Data System (ADS)

Ahmed, Shafique; Schumacher, Thomas; Thostenson, Erik T.; McConnell, Jennifer

2017-04-01

Steel structures including bridges are susceptible to cracking, particularly due to fatigue-sensitive details found in older designs. Therefore, one of the major challenges to keep those steel bridges in service is to rehabilitate existing and potential fatigue damage. There are several conventional approaches to extend the fatigue-life of damaged steel members, e.g., drilling a crack stop-hole to reduce the stress concentration at the crack tip as well as welding and bolting of steel plates or adhesive-bonding of fiber-reinforced polymers (FRP) to reduce the overall stresses. Improvement in material properties of FRP and adhesives make them a viable candidate to apply for extending the fatigue-life of steel members. However, drawbacks include the potential for debonding of the adhesive layer and/or interfaces between adhesive and adherents as well as difficulty in monitoring fatigue crack growth after rehabilitation. In this research, a holistic approach is proposed and evaluated for simultaneous extension of fatigue-life and monitoring by integrating a carbon nanotube (CNT)-based sensing layer with an adhesively-bonded FRP reinforcement. CNT-based sensing layers have a nerve-like electric resistance network, which enables distributed sensing capabilities to monitor stress levels, crack growth, and damage progression. Using laboratory-scale experiments, the simultaneous fatigue-life extension and crack monitoring capability of multifunctional CNT-based composites was evaluated. This paper introduces the fundamental concept of integrated fatigue-rehabilitation and monitoring of steel members, presents a laboratory-scale experiment to demonstrate the feasibility and effectiveness, and discusses challenges for implementation in real structures.

Crack Propagation Calculations for Optical Fibers under Static Bending and Tensile Loads Using Continuum Damage Mechanics

PubMed Central

Chen, Yunxia; Cui, Yuxuan; Gong, Wenjun

2017-01-01

Static fatigue behavior is the main failure mode of optical fibers applied in sensors. In this paper, a computational framework based on continuum damage mechanics (CDM) is presented to calculate the crack propagation process and failure time of optical fibers subjected to static bending and tensile loads. For this purpose, the static fatigue crack propagation in the glass core of the optical fiber is studied. Combining a finite element method (FEM), we use the continuum damage mechanics for the glass core to calculate the crack propagation path and corresponding failure time. In addition, three factors including bending radius, tensile force and optical fiber diameter are investigated to find their impacts on the crack propagation process and failure time of the optical fiber under concerned situations. Finally, experiments are conducted and the results verify the correctness of the simulation calculation. It is believed that the proposed method could give a straightforward description of the crack propagation path in the inner glass core. Additionally, the predicted crack propagation time of the optical fiber with different factors can provide effective suggestions for improving the long-term usage of optical fibers. PMID:29140284

Crack Propagation Calculations for Optical Fibers under Static Bending and Tensile Loads Using Continuum Damage Mechanics.

PubMed

Chen, Yunxia; Cui, Yuxuan; Gong, Wenjun

2017-11-15

Static fatigue behavior is the main failure mode of optical fibers applied in sensors. In this paper, a computational framework based on continuum damage mechanics (CDM) is presented to calculate the crack propagation process and failure time of optical fibers subjected to static bending and tensile loads. For this purpose, the static fatigue crack propagation in the glass core of the optical fiber is studied. Combining a finite element method (FEM), we use the continuum damage mechanics for the glass core to calculate the crack propagation path and corresponding failure time. In addition, three factors including bending radius, tensile force and optical fiber diameter are investigated to find their impacts on the crack propagation process and failure time of the optical fiber under concerned situations. Finally, experiments are conducted and the results verify the correctness of the simulation calculation. It is believed that the proposed method could give a straightforward description of the crack propagation path in the inner glass core. Additionally, the predicted crack propagation time of the optical fiber with different factors can provide effective suggestions for improving the long-term usage of optical fibers.

Damage tolerance of candidate thermoset composites for use on single stage to orbit vehicles

NASA Technical Reports Server (NTRS)

Nettles, A. T.; Lance, D.; Hodge, A.

1994-01-01

Four fiber/resin systems were compared for resistance to damage and damage tolerance. One toughened epoxy and three toughened bismaleimide (BMI) resins were used, all with IM7 carbon fiber reinforcement. A statistical design of experiments technique was used to evaluate the effects of impact energy, specimen thickness, and impactor diameter on the damage area, as computed by C-scans, and residual compression-after-impact (CAI) strength. Results showed that two of the BMI systems sustained relatively large damage zones yet had an excellent retention of CAI strength.

Optical stimulation of the prostate nerves: A potential diagnostic technique

NASA Astrophysics Data System (ADS)

Tozburun, Serhat

There is wide variability in sexual potency rates (9--86%) after nerve-sparing prostate cancer surgery due to limited knowledge of the location of the cavernous nerves (CN's) on the prostate surface, which are responsible for erectile function. Thus, preservation of the CN's is critical in preserving a man's ability to have spontaneous erections following surgery. Nerve-mapping devices, utilizing conventional Electrical Nerve Stimulation (ENS) techniques, have been used as intra-operative diagnostic tools to assist in preservation of the CN. However, these technologies have proven inconsistent and unreliable in identifying the CN's due to the need for physical contact, the lack of spatial selectivity, and the presence of electrical artifacts in measurements. Optical Nerve Stimulation (ONS), using pulsed infrared laser radiation, is studied as an alternative to ENS. The objective of this study is sevenfold: (1) to develop a laparoscopic laser probe for ONS of the CN's in a rat model, in vivo; (2) to demonstrate faster ONS using continuous-wave infrared laser radiation; (3) to describe and characterize the mechanism of successful ONS using alternative laser wavelengths; (4) to test a compact, inexpensive all-single-mode fiber configuration for optical stimulation of the rat CN studies; (5) to implement fiber optic beam shaping methods for comparison of Gaussian and flat-top spatial beam profiles during ONS; (6) to demonstrate successful ONS of CN's through a thin layer of fascia placed over the nerve and prostate gland; and (7) to verify the experimentally determined therapeutic window for safe and reliable ONS without thermal damage to the CN's by comparison with a computational model for thermal damage. A 5.5-Watt Thulium fiber laser operated at 1870 nm and two pigtailed, single mode, near-IR diode lasers (150-mW, 1455-nm laser and 500-mW, 1550-nm laser) were used for non-contact stimulation of the rat CN's. Successful laser stimulation, as measured by an intracavernous pressure (ICP) response in the penis, was achieved with the laser operating in CW mode. CW optical nerve stimulation provides a significantly faster ICP response time using a lower laser power laser than conventional pulsed stimulation. An all-single-mode fiber design was successfully tested in a rat model. The CN reached a threshold temperature of ˜ 42 °C, with response times as short as 3 s, and ICP responses in the rat penis of up to 50 mmHg compared to a baseline of 5--10 mmHg. Chemical etching of the distal single-mode-fiber tip produced a concave shape and transformed the Gaussian to a flat-top spatial beam profile, resulting in simplified alignment of the laser beam with the nerve. This novel, all-single-mode-fiber laser nerve stimulation system introduces several advantages including: (1) a less expensive and more compact ONS configuration; (2) elimination of alignment and cleaning bulk optical components; and (3) improved spatial beam profile for simplified alignment. For the fascia layers over the CN's (240--600 microm), the 1550 nm laser with an optical penetration depth of ˜ 930 microm in water was substituted for the 1455 nm laser. Successful ONS was achieved, for the first time, in fascia layers up to 450 microm thick which is critical for future clinical translation of this method for intra-operative identification and preservation of CN's during prostate cancer surgery. In order to define the upper limit of the therapeutic window for ONS of CN in a rat model, in vivo, identification of the thermal damage threshold for the CN after laser irradiation was investigated by direct comparison of the visible thermal damage data with a theoretical thermal damage calculation utilizing a standard Arrhenius integral model.

Metal-coated optical fiber damage sensors

NASA Astrophysics Data System (ADS)

Chang, Chia-Chen; Sirkis, James S.

1993-07-01

A process which uses electroplating methods has been developed to fabricate metal coated optical fiber sensors. The elastic-plastic characteristics of the metal coatings have been exploited to develop a sensor capable of `remembering' low velocity impact damage. These sensors have been investigated under uniaxial tension testing of unembedded sensors and under low velocity impact of graphite/epoxy specimens with embedded sensors using both Michelson and polarimetric optical arrangements. The tests show that coating properties alter the optical fiber sensor performance and that the permanent deformation in the coating can be used to monitor composite delamination/impact damage.

Thermomechanical testing of high-temperature composites - Thermomechanical fatigue (TMF) behavior of SiC(SCS-6)/Ti-15-3

NASA Technical Reports Server (NTRS)

Castelli, Michael G.; Bartolotta, Paul; Ellis, John R.

1992-01-01

Thermomechanical testing techniques recently developed for monolithic structural alloys were successfully extended to continuous fiber reinforced composite materials in plate form. The success of this adaptation was verified on a model metal matrix composite (MMC) material, namely SiC(SCS-6)/Ti-15V-3Cr-3Al-3Sn. Effects of heating system type and specimen preparation are also addressed. Cyclic lives determined under full thermomechanical conditions were shown to be significantly reduced from those obtained under comparable isothermal and in-phase bi-thermal conditions. Fractography and metallography from specimens subjected to isothermal, out-of-phase and in-phase conditions reveal distinct differences in damage-failure modes. Isothermal metallography revealed extensive matrix cracking associated with fiber damage throughout the entire cross-section of the specimen. Out-of-phase metallography revealed extensive matrix damage associated with minimal (if any) fiber cracking. However, the damage was located exclusively at surface and near-surface locations. In-phase conditions produced extensive fiber cracking throughout the entire cross-section, associated with minimal (if any) matrix damage.

Thermomechanical testing techniques for high-temparature composites: TMF behavior of SiC(SCS-6)/Ti-15-3

NASA Technical Reports Server (NTRS)

Castelli, Michael G.; Ellis, J. Rodney; Bartolotta, Paul A.

1990-01-01

Thermomechanical testing techniques recently developed for monolithic structural alloys were successfully extended to continuous fiber reinforced composite materials in plate form. The success of this adaptation was verified on a model metal matrix composite (MMC) material, namely SiC(SCS-6)/Ti-15V-3Cr-3Al-3Sn. Effects of heating system type and specimen preparation are also addressed. Cyclic lives determined under full thermo-mechanical conditions were shown to be significantly reduced from those obtained under comparable isothermal and in-phase bi-thermal conditions. Fractography and metallography from specimens subjected to isothermal, out-of-phase and in-phase conditions reveal distinct differences in damage-failure modes. Isothermal metallography revealed extensive matrix cracking associated with fiber damage throughout the entire cross-section of the specimen. Out-of-phase metallography revealed extensive matrix damage associated with minimal (if any) fiber cracking. However, the damage was located exclusively at surface and near-surface locations. In-phase conditions produced extensive fiber cracking throughout the entire cross-section, associated with minimal (if any) matrix damage.

Impact response of graphite/epoxy fabric structures

NASA Technical Reports Server (NTRS)

Lagace, Paul A.; Kraft, Michael J.

1990-01-01

The impact damage resistance and damage tolerance of graphite/epoxy fabric plate (coupon) and cylinder structures were investigated and compared in an analytical and experimental study. Hercules A370-5H/3501-6 five-harness satin weave cloth in a quasi-isotropic (0,45)(sub s) laminate configuration was utilized. Specimens were impacted with 12.7 mm diameter steel spheres at velocities ranging from 10 m/s to 100 m/s. Damage resistance of the specimens was determined through the use of dye penetrant enhanced x-radiography, sectioning, epoxy burnoff, and visual methods. Damage tolerance of the flat plate structures was assessed in a residual tensile test while damage tolerance of the cylinder structures was assessed via pressurization tests. Impacted fabric laminates exhibited matrix crushing, fiber breakage, delamination, and fiber bundle disbonds; the latter being a unique damage mode for fabric laminates. Plate delamination and bundle disbonding was found to be more extensive around the central core area of fiber damage in the coupon specimens than in the cylinder specimens which showed a cleaner damage area due to impact. Damage resistance and damage tolerance were predicted by utilizing a five-step analysis approach previously utilized for coupon configurations. Two of the five steps were adapted to account for the effects of the structural configuration of the pressurized cylinder. The damage resistance analysis provided good correlation to the fiber damage region of both the coupon and cylinder specimens. There was little difference in the size of this region in the two specimen types. However, the analysis was not able to predict the distribution of damage through-the-thickness. This was important in assessing the damage tolerance of the cylinders. The damage tolerance analysis was able to predict the residual tensile strength of the coupons. A general methodology to predict the impact damage resistance and damage tolerance of composite structures utilizing coupon data is presented.

Fiber optic sensor employing successively destroyed coupled points or reflectors for detecting shock wave speed and damage location

DOEpatents

Weiss, Jonathan D.

1995-01-01

A shock velocity and damage location sensor providing a means of measuring shock speed and damage location. The sensor consists of a long series of time-of-arrival "points" constructed with fiber optics. The fiber optic sensor apparatus measures shock velocity as the fiber sensor is progressively crushed as a shock wave proceeds in a direction along the fiber. The light received by a receiving means changes as time-of-arrival points are destroyed as the sensor is disturbed by the shock. The sensor may comprise a transmitting fiber bent into a series of loops and fused to a receiving fiber at various places, time-of-arrival points, along the receiving fibers length. At the "points" of contact, where a portion of the light leaves the transmitting fiber and enters the receiving fiber, the loops would be required to allow the light to travel backwards through the receiving fiber toward a receiving means. The sensor may also comprise a single optical fiber wherein the time-of-arrival points are comprised of reflection planes distributed along the fibers length. In this configuration, as the shock front proceeds along the fiber it destroys one reflector after another. The output received by a receiving means from this sensor may be a series of downward steps produced as the shock wave destroys one time-of-arrival point after another, or a nonsequential pattern of steps in the event time-of-arrival points are destroyed at any point along the sensor.

Fiber optic sensor employing successively destroyed coupled points or reflectors for detecting shock wave speed and damage location

DOEpatents

Weiss, J.D.

1995-08-29

A shock velocity and damage location sensor providing a means of measuring shock speed and damage location is disclosed. The sensor consists of a long series of time-of-arrival ``points`` constructed with fiber optics. The fiber optic sensor apparatus measures shock velocity as the fiber sensor is progressively crushed as a shock wave proceeds in a direction along the fiber. The light received by a receiving means changes as time-of-arrival points are destroyed as the sensor is disturbed by the shock. The sensor may comprise a transmitting fiber bent into a series of loops and fused to a receiving fiber at various places, time-of-arrival points, along the receiving fibers length. At the ``points`` of contact, where a portion of the light leaves the transmitting fiber and enters the receiving fiber, the loops would be required to allow the light to travel backwards through the receiving fiber toward a receiving means. The sensor may also comprise a single optical fiber wherein the time-of-arrival points are comprised of reflection planes distributed along the fibers length. In this configuration, as the shock front proceeds along the fiber it destroys one reflector after another. The output received by a receiving means from this sensor may be a series of downward steps produced as the shock wave destroys one time-of-arrival point after another, or a nonsequential pattern of steps in the event time-of-arrival points are destroyed at any point along the sensor. 6 figs.

Mathematical modeling of damage in unidirectional composites

NASA Technical Reports Server (NTRS)

Goree, J. G.; Dharani, L. R.; Jones, W. F.

1983-01-01

Extending the work of Goree and Gross (1979), solutions are given for a two-dimensional region of unidirectional fibers embedded in an elastic matrix whose initial flaw may take the form of a transverse notch, a rectangular cutout, or a circular hole. Subsequent flaw-induced damage is generated by remote stresses acting parallel to the fibers. For the case of such ductile matrix composites as boron/aluminum, present results indicate that both longitudinal matrix yielding and transverse notch extension must be included in order for the model to agree with experimental results. Little difference is found for the three types of initial damage considered. In all cases, the presence of additional damage changes the nature of stress distribution through the unbroken fibers.

The Nantucket pine tip moth: old problems, new research. Proceedings of an informal conference, the Entomological Society of America, annual meeting. 1999 December 12-16

Treesearch

C. Wayne Berisford; Donald M. Grosman; [Editors

2002-01-01

The Nantucket pine tip moth, Rhyacionia frustrana (Comstock) has become a more prevalent pest in the South as pine plantation management has intensified. The Pine Tip Moth Research Consortium was formed in 1995 to increase basic knowledge about the moth and to explore ways to reduce damage. A conference was held in 1999 at the Entomological Society...

Impact damage resistance and residual property assessment of (0/+/-45/90)s SCS-6/Timetal 21S

NASA Technical Reports Server (NTRS)

Miller, Jennifer L.; Portanova, Marc A.; Johnson, W. Steven

1995-01-01

The impact damage resistance and residual mechanical properties of (0/ +/- 45/90)s SCS-6/Timetal 21S composites were evaluated. Both quasi-static indentation and drop-weight impact tests were used to investigate the impact behavior at two nominal energy levels (5.5 and 8.4 J) and determine the onset of internal damage. Through x-ray inspection, the extent of internal damage was characterized non-destructively. The composite strength and constant amplitude fatigue response were evaluated to assess the effects of the sustained damage. Scanning electron microscopy was used to characterize internal damage from impact in comparison to damage that occurs during mechanical loading alone. The effect of stacking sequence was examined by using specimens with the long dimension of the specimen both parallel (longitudinal) and perpendicular (transverse) to the 0 deg fiber direction. Damage in the form of longitudinal and transverse cracking occurred in all longitudinal specimens tested at energies greater than 6.3 J. Similar results occurred in the transverse specimens tested above 5.4 J. Initial load drop, characteristic of the onset of damage, occurred on average at 6.3 J in longitudinal specimens and at 5.0 J in transverse specimens. X-ray analysis showed broken fibers in the impacted region in specimens tested at the higher impact energies. At low impact energies, visible matrix cracking may occur, but broken fibers may not. Matrix cracking was noted along fiber swims and it appeared to depend on the surface quality of composite. At low impact energies, little damage has been incurred by the composite and the residual strength and residual life is not greatly reduced as compared to an undamaged composite. At higher impact energies, more damage occurred and a greater effect of the impact damage was observed.

Modeling damage evolution in a hybrid ceramic matrix composite under static tensile load

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

Bonora, N.; Newaz, G.

In this investigation, damage evolution in a unidirectional hybrid ceramic composite made from Nicalon and SiC fibers in a Lithium Aluminosilicate (LAS) glass matrix was studied. The static stress-strain response of the composite exhibited a linear response followed by load drop in a progressive manner. Careful experiments were conducted stopping the tests at various strain levels and using replication technique, scanning and optical microscopy to monitor the evolution of damage in these composites. It was observed that the constituents of the composite failed in a sequential manner at increasing strain levels. The matrix cracks were followed by SiC fiber failuresmore » near ultimate tensile stress. After that, the load drop was associated with progressive failure of the Nicalon fibers. Identification of these failure modes were critical to the development of a concentric cylinder model representing all three constituent phases to predict the constitutive response of the CMC computationally. The strain-to-failure of the matrix and fibers were used to progressively fail the constituents in the model and the overall experimental constitutive response of the CMC was recovered. A strain based analytical representation was developed relating stiffness loss to applied strain. Based on this formulation, damage evolution and its consequence on tensile stress-strain response was predicted for room temperature behavior of hybrid CMCs. The contribution of the current work is that the proposed strain-damage phenomenological model can capture the damage evolution and the corresponding material response for continuous fiber-reinforced CMCs. The modeling approach shows much promise for the complex damage processes observed in hybrid CMCs.« less

Off-fault tip splay networks: a genetic and generic property of faults indicative of their long-term propagation, and a major component of off-fault damage

NASA Astrophysics Data System (ADS)

Perrin, C.; Manighetti, I.; Gaudemer, Y.

2015-12-01

Faults grow over the long-term by accumulating displacement and lengthening, i.e., propagating laterally. We use fault maps and fault propagation evidences available in literature to examine geometrical relations between parent faults and off-fault splays. The population includes 47 worldwide crustal faults with lengths from millimeters to thousands of kilometers and of different slip modes. We show that fault splays form adjacent to any propagating fault tip, whereas they are absent at non-propagating fault ends. Independent of parent fault length, slip mode, context, etc, tip splay networks have a similar fan shape widening in direction of long-term propagation, a similar relative length and width (~30 and ~10 % of parent fault length, respectively), and a similar range of mean angles to parent fault (10-20°). Tip splays more commonly develop on one side only of the parent fault. We infer that tip splay networks are a genetic and a generic property of faults indicative of their long-term propagation. We suggest that they represent the most recent damage off-the parent fault, formed during the most recent phase of fault lengthening. The scaling relation between parent fault length and width of tip splay network implies that damage zones enlarge as parent fault length increases. Elastic properties of host rocks might thus be modified at large distances away from a fault, up to 10% of its length. During an earthquake, a significant fraction of coseismic slip and stress is dissipated into the permanent damage zone that surrounds the causative fault. We infer that coseismic dissipation might occur away from a rupture zone as far as a distance of 10% of the length of its causative fault. Coseismic deformations and stress transfers might thus be significant in broad regions about principal rupture traces. This work has been published in Comptes Rendus Geoscience under doi:10.1016/j.crte.2015.05.002 (http://www.sciencedirect.com/science/article/pii/S1631071315000528).

The mechanics of delamination in fiber-reinforced composite materials. Part 2: Delamination behavior and fracture mechanics parameters

NASA Technical Reports Server (NTRS)

Wang, S. S.; Choi, I.

1983-01-01

Based on theories of laminate anisotropic elasticity and interlaminar fracture, the complete solution structure associated with a composite delamination is determined. Fracture mechanics parameters characterizing the interlaminar crack behavior are defined from asymptotic stress solutions for delaminations with different crack-tip deformation configurations. A numerical method employing singular finite elements is developed to study delaminations in fiber composites with any arbitrary combinations of lamination, material, geometric, and crack variables. The special finite elements include the exact delamination stress singularity in its formulation. The method is shown to be computationally accurate and efficient, and operationally simple. To illustrate the basic nature of composite delamination, solutions are shown for edge-delaminated (0/-0/-0/0) and (+ or - 0/+ or - 0/90/90 deg) graphite-epoxy systems under uniform axial extenstion. Three-dimensional crack-tip stress intensity factors, associated energy release rates, and delamination crack-closure are determined for each individual case. The basic mechanics and mechanisms of composite delamination are studied, and fundamental characteristics unique to recently proposed tests for interlaminar fracture toughness of fiber composite laminates are examined.

Theoretical analysis of a novel ultrasound generator on an optical fiber tip

NASA Astrophysics Data System (ADS)

Wu, Nan; Wang, Wenhui; Tian, Ye; Guthy, Charles; Wang, Xingwei

2010-04-01

A novel ultrasound generator consisting of a single mode optical fiber with a layer of gold nanoparticles on its tip has been designed. The generator utilizes the optical and photo-acoustic properties of gold nanoparticles. When heated by laser pulses, a thin absorption layer made up of these nanoparticles at the cleaved surface of a single mode fiber generates a mechanical shock wave caused by thermal expansion. Mie's theory was applied in a MATLAB simulation to determine the relationship between the absorption efficiency and the optical resonance wavelengths of a layer of gold nanospheres. Results showed that the absorption efficiency and related resonance wavelengths of gold nanospheres varied based on the size of the gold nanosphere particles. In order to obtain the bandwidths associated with ultrasound, another MATLAB simulation was run to study the relationship between the power of the laser being used, the size of the gold nanosphere, and the energy decay time. The results of this and the previous simulation showed that the energy decay time is picoseconds in length.

A Blade Tip Timing Method Based on a Microwave Sensor

PubMed Central

Zhang, Jilong; Duan, Fajie; Niu, Guangyue; Jiang, Jiajia; Li, Jie

2017-01-01

Blade tip timing is an effective method for blade vibration measurements in turbomachinery. This method is increasing in popularity because it is non-intrusive and has several advantages over the conventional strain gauge method. Different kinds of sensors have been developed for blade tip timing, including optical, eddy current and capacitance sensors. However, these sensors are unsuitable in environments with contaminants or high temperatures. Microwave sensors offer a promising potential solution to overcome these limitations. In this article, a microwave sensor-based blade tip timing measurement system is proposed. A patch antenna probe is used to transmit and receive the microwave signals. The signal model and process method is analyzed. Zero intermediate frequency structure is employed to maintain timing accuracy and dynamic performance, and the received signal can also be used to measure tip clearance. The timing method uses the rising and falling edges of the signal and an auto-gain control circuit to reduce the effect of tip clearance change. To validate the accuracy of the system, it is compared experimentally with a fiber optic tip timing system. The results show that the microwave tip timing system achieves good accuracy. PMID:28492469

A Blade Tip Timing Method Based on a Microwave Sensor.

PubMed

Zhang, Jilong; Duan, Fajie; Niu, Guangyue; Jiang, Jiajia; Li, Jie

2017-05-11

Blade tip timing is an effective method for blade vibration measurements in turbomachinery. This method is increasing in popularity because it is non-intrusive and has several advantages over the conventional strain gauge method. Different kinds of sensors have been developed for blade tip timing, including optical, eddy current and capacitance sensors. However, these sensors are unsuitable in environments with contaminants or high temperatures. Microwave sensors offer a promising potential solution to overcome these limitations. In this article, a microwave sensor-based blade tip timing measurement system is proposed. A patch antenna probe is used to transmit and receive the microwave signals. The signal model and process method is analyzed. Zero intermediate frequency structure is employed to maintain timing accuracy and dynamic performance, and the received signal can also be used to measure tip clearance. The timing method uses the rising and falling edges of the signal and an auto-gain control circuit to reduce the effect of tip clearance change. To validate the accuracy of the system, it is compared experimentally with a fiber optic tip timing system. The results show that the microwave tip timing system achieves good accuracy.

Four-probe measurements with a three-probe scanning tunneling microscope

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

Salomons, Mark; Martins, Bruno V. C.; Zikovsky, Janik

2014-04-15

We present an ultrahigh vacuum (UHV) three-probe scanning tunneling microscope in which each probe is capable of atomic resolution. A UHV JEOL scanning electron microscope aids in the placement of the probes on the sample. The machine also has a field ion microscope to clean, atomically image, and shape the probe tips. The machine uses bare conductive samples and tips with a homebuilt set of pliers for heating and loading. Automated feedback controlled tip-surface contacts allow for electrical stability and reproducibility while also greatly reducing tip and surface damage due to contact formation. The ability to register inter-tip position bymore » imaging of a single surface feature by multiple tips is demonstrated. Four-probe material characterization is achieved by deploying two tips as fixed current probes and the third tip as a movable voltage probe.« less

DETECTION OF DNA DAMAGE USING A FIBEROPTIC BIOSENSOR

EPA Science Inventory

A rapid and sensitive fiber optic biosensor assay for radiation-induced DNA damage is reported. For this assay, a biotin-labeled capture oligonucleotide (38 mer) was immobilized to an avidin-coated quartz fiber. Hybridization of a dye-labeled complementary sequence was observed...

Repair of impact damaged utility poles with fiber reinforced polymers (FRP), phase II.

DOT National Transportation Integrated Search

2015-06-01

Vehicle collisions with steel or aluminum utility poles are common occurrences that yield substantial but often repairable : damage. This project investigates the use of a fiber-reinforced polymer (FRP) composite system for in situ repair that : mini...

Characterization of Scintillating X-ray Optical Fiber Sensors

PubMed Central

Sporea, Dan; Mihai, Laura; Vâţă, Ion; McCarthy, Denis; O'Keeffe, Sinead; Lewis, Elfed

2014-01-01

The paper presents a set of tests carried out in order to evaluate the design characteristics and the operating performance of a set of six X-ray extrinsic optical fiber sensors. The extrinsic sensor we developed is intended to be used as a low energy X-ray detector for monitoring radiation levels in radiotherapy, industrial applications and for personnel dosimetry. The reproducibility of the manufacturing process and the characteristics of the sensors were assessed. The sensors dynamic range, linearity, sensitivity, and reproducibility are evaluated through radioluminescence measurements, X-ray fluorescence and X-ray imaging investigations. Their response to the operating conditions of the excitation source was estimated. The effect of the sensors design and implementation, on the collecting efficiency of the radioluminescence signal was measured. The study indicated that the sensors are efficient only in the first 5 mm of the tip, and that a reflective coating can improve their response. Additional tests were done to investigate the concentricity of the sensors tip against the core of the optical fiber guiding the optical signal. The influence of the active material concentration on the sensor response to X-ray was studied. The tests were carried out by measuring the radioluminescence signal with an optical fiber spectrometer and with a Multi-Pixel Photon Counter. PMID:24556676

Optical cross-talk and surface characterization of SERS nanoimaging bundle substrates

NASA Astrophysics Data System (ADS)

Kiser, John B.; Cullum, Brian M.

2010-04-01

Due to the narrow vibrational bandwidths and unique molecular fingerprints, Raman spectroscopy can be an information rich transduction technique for chemical imaging. Dynamic systems are often difficult to measure using spontaneous Raman due to the relatively weak scattering cross-sections. Using a Raman enhancement mechanism such as surface enhanced Raman scattering (SERS), exposure times can be reduced to a reasonable level for dynamic imaging, due to the increased Raman signal intensity. This paper will discuss the development of a novel SERS substrate, fabricated on the tips of fiber-optic imaging bundles, which can be integrated into a multispectral imaging system for non-scanning chemical imaging. These substrates are fabricated by mechanically tapering a polished fiber optic imaging bundle consisting of 30,000 individual elements; producing 100-nm or smaller diameter core elements on the distal tip. Chemical etching with hydrofluoric acid creates uniform cladding spikes onto which a SERS active metal is vacuum deposited, forming the SERS active surface. By varying the size of the silver islands deposited on the cladding peaks active, surface plasmons can be tuned to various excitation frequencies. The surface of these tapered fiber optic probes will be evaluated by analysis of the SERS signal, location and shape of the active surface plasmons. The cross talk between the fiber elements will also be evaluated.

Capillary-Channeled Polymer (C-CP) Fibers as a Stationary Phase for Sample Clean-Up of Protein Solutions for Matrix-Assisted Laser/Desorption Ionization Mass Spectrometry

NASA Astrophysics Data System (ADS)

Manard, Benjamin T.; Marcus, R. Kenneth

2012-08-01

Capillary-channeled polymer (C-CP) fibers are employed in a micropipette tip format to affect a stationary phase for the solid phase extraction (SPE) of proteins from buffer solutions prior to MALDI-MS analysis. Proteins readily adsorb to the polypropylene (PP) C-CP fibers while buffer species are easily washed off the tips using DI-H2O. Elution of the solutes is achieved with an aliquot of 50:50 ACN:H2O, which is compatible with the subsequent spotting on the MALDI target with the matrix solution. Lysozyme and cytochrome c are used as test species, with a primary buffer composition of 100 mM Tris-HCl. In this case, direct MALDI-MS produces no discernible protein signals. SPE on the C-CP fibers yields high fidelity mass spectra for 1 μL sample volumes. Limits of detection for cytochrome c in 100 mM Tris-HCl are on the order of 40 nM. Extraction of cytochrome c from buffer concentrations of up to 1 M Tris-HCl, provides signal recoveries that are suppressed by only ~50 % versus neat protein solutions. Finally, extraction of 3.1 μM cytochrome c from a synthetic urine matrix exhibits excellent recovery.

Multiscale Modeling of Ablation and Pyrolysis in PICA-Like materials

NASA Technical Reports Server (NTRS)

Lachaud, Jean; Mansour, Nagi N.

2008-01-01

During atmospheric entry of planetary probes, the thermal protection system (TIPS) of the probe is exposed to high temperatures under low pressures. In these conditions, carbonous fibrous TIPS materials may undergo oxidation leading to mass loss and wall recession called ablation. This work aims to improve the understanding of material/environment interactions through a study of the coupling between oxygen transport in the Knudsen regime, heterogeneous oxidation of carbon, and surface recession. A 3D Random Walk Monte Carlo simulation tool is used for this study. The fibrous architecture of a model material, consisting of high porosity random array of carbon fibers, is numerically represented on a 3D Cartesian grid. Mass transport in the Knudsen regime from the boundary layer to the surface, and inside this porous material is simulated by random walk. A reaction probability is used to simulate the heterogeneous oxidation reaction. The surface recession of the fibers is followed by front tracking using a simplified marching cube approach. The output data of the simulations are ablation velocity and dynamic evolution of the material porosity. A parametric study is carried out to analyze the material behavior as a function of Knudsen number for the porous media (length of the mean free path compared to the mean pore diameter) and the intrinsic reactivity of the carbon fibers. The model is applied to Stardust mission reentry conditions and explains the unexpected behavior of the TIPS material that underwent mass loss in volume.

Impact Characteristics of Candidate Materials for Single-Stage-to-Orbit (SSTO) Technology

NASA Technical Reports Server (NTRS)

Nettles, Alan

1995-01-01

Four fiber/resin systems were compared for resistance to damage and damage tolerance. One toughened epoxy and three toughened bismaleimide (BMI) resins were used., all with IM7 carbon fiber reinforcement. A statistical design of experiments technique was used to evaluate the effects of impact energy, specimen thickness and tup diameter on the damage area and residual compression-after-impact (CAI) strength. Results showed that two of the BMI systems sustained relatively large damage areas yet had an excellent retention of CAI strength.

Fabrication and characterization of a nanometer-sized optical fiber electrode based on selective chemical etching for scanning electrochemical/optical microscopy.

PubMed

Maruyama, Kenichi; Ohkawa, Hiroyuki; Ogawa, Sho; Ueda, Akio; Niwa, Osamu; Suzuki, Koji

2006-03-15

We have already reported a method for fabricating ultramicroelectrodes (Suzuki, K. JP Patent, 2004-45394, 2004). This method is based on the selective chemical etching of optical fibers. In this work, we undertake a detailed investigation involving a combination of etched optical fibers with various types of tapered tip (protruding-shape, double- (or pencil-) shape and triple-tapered electrode) and insulation with electrophoretic paint. Our goal is to establish a method for fabricating nanometer-sized optical fiber electrodes with high reproducibility. As a result, we realized pencil-shaped and triple-tapered electrodes that had radii in the nanometer range with high reproducibility. These nanometer-sized electrodes showed well-defined sigmoidal curves and stable diffusion-limited responses with cyclic voltammetry. The pencil-shaped optical fiber, which has a conical tip with a cone angle of 20 degrees , was effective for controlling the electrode radius. The pencil-shaped electrodes had higher reproducibility and smaller electrode radii (r(app) < 1.0 nm) than those of other etched optical fiber electrodes. By using a pencil-shaped electrode with a 105-nm radius as a probe, we obtained simultaneous electrochemical and optical images of an implantable interdigitated array electrode. We achieved nanometer-scale resolution with a combination of scanning electrochemical microscopy SECM and optical microscopy. The resolution of the electrochemical and optical images indicated sizes of 300 and 930 nm, respectively. The neurites of living PC12 cells were also successfully imaged on a 1.6-microm scale by using the negative feedback mode of an SECM.

In vivo study of partial liver resection on pigs using a 1.9 μm thulium fiber laser

NASA Astrophysics Data System (ADS)

Theisen-Kunde, D.; Wolken, H.; Danicke, V.; Brinkmann, R.; Bruch, H.; Kleemann, M.

2011-07-01

Dissection of liver tissue can be performed by different techniques (ultrasound, mono and bipolar dissection, water jet dissection and by stapler). In this animal study the potential of a Thulium fiber laser system was investigated for open parenchyma dissection. Based on a cw Thulium fiber laser (IPG laser GmbH, Burbach, Germany), emitting a wavelength at 1.9 μm and a maximal power at 50 W, a surgical dissection device was developed at the Medical Laser Centre Luebeck. Cw laser radiation (40 Watt) was transmitted via a 365 μm fiber with a polished distal fiber tip. Procedure was performed in contact mode; irradiance at the distal fiber tip was 38.2 kW/cm2. After general anesthesia and a median laparotomy an atypical laser resection of the liver was performed in 3 pigs. Healing process was controlled after 2-3 weeks by histological analysis (H&E staining). The final evaluation data included total resection time, blood loss, bile leakage and mass of dissected tissue. All animals treated in this study were cared for in accordance to the European convention on animal care. In general the dissection with the 1.9 μm laser radiation was easily performed. Hemostasis was highly sufficient so blood loss and bile leakage was negligible. Total resection time including hemostasis of the remaining tissue was 26 +/- 12 min. Weight of resected tissue was 17 +/- 8 g. During survival period no complications (bleeding or inflammation) occurred. After 2 weeks histology showed ongoing scar formation about 1 - 2 mm in depth of the dissected area.

High-speed photography during laser-based gall bladder stone lithotripsy

NASA Astrophysics Data System (ADS)

Kokaj, Jahja O.

2001-04-01

Shadowgraphy of gall bladder stone, which is held by a basket and immersed in a civete is performed. The exposure time is determined by the time of a N-Dye laser pulse used as a lightening source for photography. The shadowgram is projected in the objective of a camera which is connected to a microscope. The light coming from the laser, illuminates the civete collecting optical information of the stone and physical phenomena appearing above the stone. On top of the stone a tip of optical fiber is fixed, which is used for transmitting Ho:Yag laser power to the stone. Using a computer and time delay the laser pulses used for destruction and illumination are synchronized. Since the N-Dye laser pulse is pico-second range and the Ho:Yag laser pulse is in the range of micro-second, many image frames are obtained within the time of one pulse applied during the destruction. It is known that in the process of stone destruction several phenomena like plume, plasma, shock wave and bubble formation take place. However, the physical mechanism of the stone destruction is not yet completely understood. From the obtained results the above phenomena are studied which gives new information and clue for understanding some of the mentioned phenomena. The laser power which is guided by an optical fiber into the gall bladder or kidney of the human body can damage the living tissue and cause some serious health problems. For this reason the fiber needs to be oriented properly during the action of the laser power.

Dynamics of laser-induced channel formation in water and influence of pulse duration on the ablation of biotissue under water with pulsed erbium-laser radiation

NASA Astrophysics Data System (ADS)

Ith, M.; Pratisto, H.; Altermatt, H. J.; Frenz, M.; Weber, H. P.

1994-12-01

The ability to use fiber-delivered erbium-laser radiation for non-contact arthroscopic meniscectomy in a liquid environment was studied. The laser radiation is transmitted through a water-vapor channel created by the leading part of the laser pulse. The dynamics of the channel formation around a submerged fiber tip was investigated with time-resolved flash photography. Strong pressure transients with amplitudes up to a few hundreds of bars measured with a needle hydrophone were found to accompany the channel formation process. Additional pressure transients in the range of kbars were observed after the laser pulse associated with the collapse of the vapor channel. Transmission measurements revealed that the duration the laser-induced channel stays open, and therefore the energy transmittable through it, is substantially determined by the laser pulse duration. The optimum pulse duration was found to be in the range between 250 and 350 µS. This was confirmed by histological evaluations of the laser incisions in meniscus: Increasing the pulse duration from 300 to 800 µs leads to a decrease in the crater depth from 1600 to 300 µm. A comparison of the histological examination after laser treatment through air and through water gave information on the influence of the vapor channel on the ablation efficiency, the cutting quality and the induced thermal damage in the adjacent tissue. The study shows that the erbium laser combined with an adequate fiber delivery system represents an effective surgical instrument liable to become increasingly accepted in orthopedic surgery.

Method of making single crystal fibers

NASA Technical Reports Server (NTRS)

Westfall, Leonard J. (Inventor)

1990-01-01

Single crystal fibers are made from miniature extruded ceramic feed rods. A decomposable binder is mixed with powders to inform a slurry which is extruded into a small rod which may be sintered, either in air or in vacuum, or it may be used in the extruded and dried condition. A pair of laser beams focuses onto the tip of the rod to melt it thereby forming a liquid portion. A single crystal seed fiber of the same material as the feed rod contacts this liquid portion to establish a zone of liquid material between the feed rod and the single crystal seed fiber. The feed rod and the single crystal feed fiber are moved at a predetermined speed to solidify the molten zone onto the seed fiber while simultaneously melting additional feed rod. In this manner a single crystal fiber is formed from the liquid portion.

A comprehensive review of lossy mode resonance-based fiber optic sensors

NASA Astrophysics Data System (ADS)

Wang, Qi; Zhao, Wan-Ming

2018-01-01

This review paper presents the achievements and present developments in lossy mode resonances-based optical fiber sensors in different sensing field, such as physical, chemical and biological, and briefly look forward to its future development trend in the eyes of the author. Lossy mode resonances (LMR) is a relatively new physical optics phenomenon put forward in recent years. Fiber sensors utilizing LMR offered a new way to improve the sensing capability. LMR fiber sensors have diverse structures such as D-shaped, cladding-off, fiber tip, U-shaped and tapered fiber structures. Major applications of LMR sensors include refraction sensors and biosensors. LMR-based fiber sensors have attracted considerable research and development interest, because of their distinct advantages such as high sensitivity and label-free measurement. This kind of sensor is also of academic interest and many novel and great ideas are continuously developed.

Stiffness monitoring and damage assessment of bridges under moving vehicular loads using spatially-distributed optical fiber sensors

NASA Astrophysics Data System (ADS)

Wu, Bitao; Wu, Gang; Lu, Huaxi; Feng, De-chen

2017-03-01

Fiber optic sensing technology has been widely used in civil infrastructure health monitoring due to its various advantages, e.g., anti-electromagnetic interference, corrosion resistance, etc. This paper investigates a new method for stiffness monitoring and damage identification of bridges under moving vehicle loads using spatially-distributed optical fiber sensors. The relationship between the element stiffness of the bridge and the long-gauge strain history is firstly studied, and a formula which is expressed by the long-gauge strain history is derived for the calculation of the bridge stiffness. Meanwhile, the stiffness coefficient from the formula can be used to identify the damage extent of the bridge. In order to verify the proposed method, a model test of a 1:10 scale bridge-vehicle system is conducted and the long-gauge strain history is obtained through fiber Bragg grating sensors. The test results indicate that the proposed method is suitable for stiffness monitoring and damage assessment of bridges under moving vehicular loads.

Fatigue damage monitoring for basalt fiber reinforced polymer composites using acoustic emission technique

NASA Astrophysics Data System (ADS)

Wang, Wentao; Li, Hui; Qu, Zhi

2012-04-01

Basalt fiber reinforced polymer (BFRP) is a structural material with superior mechanical properties. In this study, unidirectional BFRP laminates with 14 layers are made with the hand lay-up method. Then, the acoustic emission technique (AE) combined with the scanning electronic microscope (SEM) technique is employed to monitor the fatigue damage evolution of the BFRP plates in the fatigue loading tests. Time-frequency analysis using the wavelet transform technique is proposed to analyze the received AE signal instead of the peak frequency method. A comparison between AE signals and SEM images indicates that the multi-frequency peaks picked from the time-frequency curves of AE signals reflect the accumulated fatigue damage evolution and fatigue damage patterns. Furthermore, seven damage patterns, that is, matrix cracking, delamination, fiber fracture and their combinations, are identified from the time-frequency curves of the AE signals.

Mode division multiplexing technology for single-fiber optical trapping axial-position adjustment.

PubMed

Liu, Zhihai; Wang, Lei; Liang, Peibo; Zhang, Yu; Yang, Jun; Yuan, Libo

2013-07-15

We demonstrate trapped yeast cell axial-position adjustment without moving the optical fiber in a single-fiber optical trapping system. The dynamic axial-position adjustment is realized by controlling the power ratio of the fundamental mode beam (LP01) and the low-order mode beam (LP11) generated in a normal single-core fiber. In order to separate the trapping positions produced by the two mode beams, we fabricate a special fiber tapered tip with a selective two-step method. A yeast cell of 6 μm diameter is moved along the optical axis direction for a distance of ~3 μm. To the best of our knowledge, this is the first demonstration of the trapping position adjustment without moving the fiber for single-fiber optical tweezers. The excitation and utilization of multimode beams in a single fiber constitutes a new development for single-fiber optical trapping and makes possible more practical applications in biomedical research fields.

Comparison of efficiency and feedback characteristics of techniques of coupling semiconductor lasers into single-mode fiber.

PubMed

Wenke, G; Zhu, Y

1983-12-01

The coupling of CSP lasers to single-mode fibers with different coupling structures made on the fiber face is investigated. In this case easy to make coupling arrangements such as tapers and microlenses, result in a high launching efficiency (approximately 2-dB loss), in contrast to launching from gain-guided lasers with strong astigmatism and a broader far-field pattern. Index-guiding lasers exhibit, however, a higher sensitivity to optical feedback. Laser output power and wavelength are changed due to reflections from the fiber tip. Critical distances exist which lead to a highly unstable laser spectrum. A comparison of the influence of various fiber faces on laser power and wavelength stability is presented. It is concluded that a tapered fiber end with a large working distance reduces the influence on the laser's performance.

Progressive Fracture of Fiber Composite Thin Shell Structures Under Internal Pressure and Axial Loads

NASA Technical Reports Server (NTRS)

Gotsis, Pascal K.; Chamis, Christos C.; Minnetyan, Levon

1996-01-01

Graphite/epoxy composite thin shell structures were simulated to investigate damage and fracture progression due to internal pressure and axial loading. Defective and defect-free structures (thin cylinders) were examined. The three different laminates examined had fiber orientations of (90/0/+/-0)(sub s), where 0 is 45, 60, and 75 deg. CODSTRAN, an integrated computer code that scales up constituent level properties to the structural level and accounts for all possible failure modes, was used to simulate composite degradation under loading. Damage initiation, growth, accumulation, and propagation to fracture were included in the simulation. Burst pressures for defective and defect-free shells were compared to evaluate damage tolerance. The results showed that damage initiation began with matrix failure whereas damage and/or fracture progression occurred as a result of additional matrix failure and fiber fracture. In both thin cylinder cases examined (defective and defect-free), the optimum layup configuration was (90/0/+/-60)(sub s) because it had the best damage tolerance with respect to the burst pressure.

Nondestructive evaluation and characterization of damage and repair to continuous-fiber ceramic composite panels.

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

Sun, J. G.; Petrak, D. R.; Pillai, T. A. K.

1998-04-01

Continuous fiber ceramic matrix composites are currently being developed for a variety of high-temperature applications. Because of the high costs of making these components, minor damage incurred during manufacturing or operation must be rewired in order to extend the life of the components. In this study, five ceramic-grade Nicalon{trademark} fiber/SiNC-matrix composite panels were intentionally damaged with a pendulum-type impactor during an impact test. The damaged panels were then repaired at Dow Corning Corporation. Three nondestructive evaluation (NDE) methods were used to study the characteristics of the panels after the damage and again after the panels were repaired. The NDE methodsmore » were X-ray radiography, infrared thermal imaging, and air-coupled ultrasound. The results showed that the impact test induced various types of damage in the panels. The NDE data that were obtained by the three NDE methods were correlated with each other.« less

Response Growth With Sound Level in Auditory-Nerve Fibers After Noise-Induced Hearing Loss

PubMed Central

Heinz, Michael G.; Young, Eric D.

2010-01-01

People with sensorineural hearing loss are often constrained by a reduced acoustic dynamic range associated with loudness recruitment; however, the neural correlates of loudness and recruitment are still not well understood. The growth of auditory-nerve (AN) activity with sound level was compared in normal-hearing cats and in cats with a noise-induced hearing loss to test the hypothesis that AN-fiber rate-level functions are steeper in impaired ears. Stimuli included best-frequency and fixed-frequency tones, broadband noise, and a brief speech token. Three types of impaired responses were observed. 1) Fibers with rate-level functions that were similar across all stimuli typically had broad tuning, consistent with outer-hair-cell (OHC) damage. 2) Fibers with a wide dynamic range and shallow slope above threshold often retained sharp tuning, consistent with primarily inner-hair-cell (IHC) damage. 3) Fibers with very steep rate-level functions for all stimuli had thresholds above approximately 80 dB SPL and very broad tuning, consistent with severe IHC and OHC damage. Impaired rate-level slopes were on average shallower than normal for tones, and were steeper in only limited conditions. There was less variation in rate-level slopes across stimuli in impaired fibers, presumably attributable to the lack of suppression-induced reductions in slopes for complex stimuli relative to BF-tone slopes. Sloping saturation was observed less often in impaired fibers. These results illustrate that AN fibers do not provide a simple representation of the basilar-membrane I/O function and suggest that both OHC and IHC damage can affect AN response growth. PMID:14534289

Fiber optic cables for transmission of high-power laser pulses in spaceflight applications

NASA Astrophysics Data System (ADS)

Thomes, W. J.; Ott, M. N.; Chuska, R. F.; Switzer, R. C.; Blair, D. E.

2017-11-01

Lasers with high peak power pulses are commonly used in spaceflight missions for a wide range of applications, from LIDAR systems to optical communications. Due to the high optical power needed, the laser has to be located on the exterior of the satellite or coupled through a series of free space optics. This presents challenges for thermal management, radiation resistance, and mechanical design. Future applications will require multiple lasers located close together, which further complicates the design. Coupling the laser energy into a fiber optic cable allows the laser to be relocated to a more favorable position on the spacecraft. Typical fiber optic termination procedures are not sufficient for injection of these high-power laser pulses without catastrophic damage to the fiber endface. In the current study, we will review the causes of fiber damage during high-power injection and discuss our new manufacturing procedures that overcome these issues to permit fiber use with high reliability in these applications. We will also discuss the proper methods for launching the laser pulses into the fiber to avoid damage and how this is being implemented for current spaceflight missions.

Fiber Optic Cables for Transmission of High-Power Laser Pulses in Spaceflight Applications

NASA Technical Reports Server (NTRS)

Thomes, W. J., Jr.; Ott, M. N.; Chuska, R. F.; Switzer, R. C.; Blair, D. E.

2010-01-01

Lasers with high peak power pulses are commonly used in spaceflight missions for a wide range of applications, from LIDAR systems to optical communications. Due to the high optical power needed, the laser has to be located on the exterior of the satellite or coupled through a series of free space optics. This presents challenges for thermal management, radiation resistance, and mechanical design. Future applications will require multiple lasers located close together, which further complicates the design. Coupling the laser energy into a fiber optic cable allows the laser to be relocated to a more favorable position on the spacecraft. Typical fiber optic termination procedures are not sufficient for injection of these high-power laser pulses without catastrophic damage to the fiber endface. In the current study, we will review the causes of fiber damage during high-power injection and discuss our new manufacturing procedures that overcome these issues to permit fiber use with high reliability in these applications. We will also discuss the proper methods for launching the laser pulses into the fiber to avoid damage and how this is being implemented for current spaceflight missions.

Adhesion design maps for bio-inspired attachment systems.

PubMed

Spolenak, Ralph; Gorb, Stanislav; Arzt, Eduard

2005-01-01

Fibrous surface structures can improve the adhesion of objects to other surfaces. Animals, such as flies and geckos, take advantage of this principle by developing "hairy" contact structures which ensure controlled and repeatable adhesion and detachment. Mathematical models for fiber adhesion predict pronounced dependencies of contact performance on the geometry and the elastic properties of the fibers. In this paper the limits of such contacts imposed by fiber strength, fiber condensation, compliance, and ideal contact strength are modeled for spherical contact tips. Based on this, we introduce the concept of "adhesion design maps" which visualize the predicted mechanical behavior. The maps are useful for understanding biological systems and for guiding experimentation to achieve optimum artificial contacts.

A Micro Bubble Structure Based Fabry–Perot Optical Fiber Strain Sensor with High Sensitivity and Low-Cost Characteristics

PubMed Central

Yan, Lu; Gui, Zhiguo; Wang, Guanjun; An, Yongquan; Gu, Jinyu; Zhang, Meiqin; Liu, Xinglin; Wang, Zhibin; Wang, Gao; Jia, Pinggang

2017-01-01

A high-sensitivity, low-cost, ultrathin, hollow fiber micro bubble structure was proposed; such a bubble can be used to develop a high-sensitivity strain sensor based on a Fabry–Perot interferometer (FPI). The micro bubble is fabricated at the fiber tip by splicing a glass tube to a single mode fiber (SMF) and then the glass tube is filled with gas in order to expand and form a micro bubble. The sensitivity of the strain sensor with a cavity length of about 155 μm and a bubble wall thickness of about 6 μm was measured to be up to 8.14 pm/με. PMID:28282960

A Micro Bubble Structure Based Fabry-Perot Optical Fiber Strain Sensor with High Sensitivity and Low-Cost Characteristics.

PubMed

Yan, Lu; Gui, Zhiguo; Wang, Guanjun; An, Yongquan; Gu, Jinyu; Zhang, Meiqin; Liu, Xinglin; Wang, Zhibin; Wang, Gao; Jia, Pinggang

2017-03-09

A high-sensitivity, low-cost, ultrathin, hollow fiber micro bubble structure was proposed; such a bubble can be used to develop a high-sensitivity strain sensor based on a Fabry-Perot interferometer (FPI). The micro bubble is fabricated at the fiber tip by splicing a glass tube to a single mode fiber (SMF) and then the glass tube is filled with gas in order to expand and form a micro bubble. The sensitivity of the strain sensor with a cavity length of about 155 μm and a bubble wall thickness of about 6 μm was measured to be up to 8.14 pm/μϵ.

Characterization of failure processes in tungsten copper composites under fatigue loading conditions

NASA Technical Reports Server (NTRS)

Kim, Yong-Suk; Verrilli, Michael J.; Gabb, Timothy P.

1989-01-01

A fractographic and metallographic investigation was performed on specimens of a tungsten fiber reinforced copper matrix composite (9 vol percent), which had experienced fatigue failures at elevated temperatures. Major failure modes and possible failure mechanisms, with an emphasis placed on characterizing fatigue damage accumulation, were determined. Metallography of specimens fatigued under isothermal cyclic loading suggested that fatigue damage initiates in the matrix. Cracks nucleated within the copper matrix at grain boundaries, and they propagated through cavity coalescence. The growing cracks subsequently interacted with the reinforcing tungsten fibers, producing a localized ductile fiber failure. Examinations of interrupted tests before final failure confirmed the suggested fatigue damage processes.

Flow/Damage Surfaces for Fiber-Reinforced Metals Having Different Periodic Microstructures

NASA Technical Reports Server (NTRS)

Lissenden, Cliff J.; Arnold, Steven M.; Iyer, Saiganesh K.

1998-01-01

Flow/damage surfaces can be defined in terms of stress, inelastic strain rate, and internal variables using a thermodynamics framework. A macroscale definition relevant to thermodynamics and usable in an experimental program is employed to map out surfaces of constant inelastic power in various stress planes. The inelastic flow of a model silicon carbide/ titanium composite system having rectangular, hexagonal, and square diagonal fiber packing arrays subjected to biaxial stresses is quantified by flow/damage surfaces that are determined numerically from micromechanics, using both finite element analysis and the generalized method of cells. Residual stresses from processing are explicitly included and damage in the form of fiber-matrix debonding under transverse tensile and/or shear loading is represented by a simple interface model. The influence of microstructural architecture is largest whenever fiber-matrix debonding is not an issue; for example in the presence of transverse compressive stresses. Additionally, as the fiber volume fraction increases, so does the effect of microstructural architecture. With regard to the micromechanics analysis, the overall inelastic flow predicted by the generalized method of cells is in excellent agreement with that predicted using a large number of displacement-based finite elements.

Flow/Damage Surfaces for Fiber-Reinforced Metals having Different Periodic Microstructures

NASA Technical Reports Server (NTRS)

Lissenden, Cliff J.; Arnold, Steven M.; Iyer, Saiganesh K.

1998-01-01

Flow/damage surfaces can be defined in terms of stress, inelastic strain rate, and internal variables using a thermodynamics framework. A macroscale definition relevant to thermodynamics and usable in an experimental program is employed to map out surfaces of constant inelastic power in various stress planes. The inelastic flow of a model silicon carbide/ titanium composite system having rectangular, hexagonal, and square diagonal fiber packing, arrays subjected to biaxial stresses is quantified by flow/damage surfaces that are determined numerically from micromechanics. using both finite element analysis and the generalized method of cells. Residual stresses from processing are explicitly included and damage in the form of fiber-matrix debonding under transverse tensile and/or shear loading is represented by a simple interface model. The influence of microstructural architecture is largest whenever fiber-matrix debonding is not an issue, for example in the presence of transverse compressive stresses. Additionally, as the fiber volume fraction increases, so does the effect of microstructural architecture. With regard to the micromechanics analysis, the overall inelastic flow predicted by the generalized method of cells is in excellent agreement with that predicted using a large number of displacement-based finite elements.

Progressive Fracture of Laminated Fiber-Reinforced Composite Stiffened Plate Under Pressure

NASA Technical Reports Server (NTRS)

Gotsis, Pascalis K.; Abdi, Frank; Chamis, Christos C.; Tsouros, Konstantinos

2007-01-01

S-Glass/epoxy laminated fiber-reinforced composite stiffened plate structure with laminate configuration (0/90)5 was simulated to investigate damage and fracture progression, under uniform pressure. For comparison reasons a simple plate was examined, in addition with the stiffened plate. An integrated computer code was used for the simulation. The damage initiation began with matrix failure in tension, continuous with damage and/or fracture progression as a result of additional matrix failure and fiber fracture and followed by additional interply delamination. Fracture through the thickness began when the damage accumulation was 90%. After that stage, the cracks propagate rapidly and the structures collapse. The collapse load for the simple plate is 21.57 MPa (3120 psi) and for the stiffened plate 25.24 MPa (3660 psi).

A parametric study of fracture toughness of fibrous composite materials

NASA Technical Reports Server (NTRS)

Poe, C. C., Jr.

1987-01-01

Impacts to fibrous composite laminates by objects with low velocities can break fibers giving crack-like damage. The damage may not extend completely through a thick laminate. The tension strength of these damage laminates is reduced much like that of cracked metals. The fracture toughness depends on fiber and matrix properties, fiber orientations, and stacking sequence. Accordingly, a parametric study was made to determine how fiber and matrix properties and fiber orientations affect fracture toughness and notch sensitivity. The values of fracture toughness were predicted from the elastic constants of the laminate and the failing strain of the fibers using a general fracture toughness parameter developed previously. For a variety of laminates, values of fracture toughness from tests of center-cracked specimens and values of residual strength from tests of thick laminates with surface cracks were compared to the predictions to give credibility to the study. In contrast to the usual behavior of metals, it is shown that both ultimate tensile strength and fracture toughness of composites can be increased without increasing notch sensitivity.

The Effect of General Statistical Fiber Misalignment on Predicted Damage Initiation in Composites

NASA Technical Reports Server (NTRS)

Bednarcyk, Brett A.; Aboudi, Jacob; Arnold, Steven M.

2014-01-01

A micromechanical method is employed for the prediction of unidirectional composites in which the fiber orientation can possess various statistical misalignment distributions. The method relies on the probability-weighted averaging of the appropriate concentration tensor, which is established by the micromechanical procedure. This approach provides access to the local field quantities throughout the constituents, from which initiation of damage in the composite can be predicted. In contrast, a typical macromechanical procedure can determine the effective composite elastic properties in the presence of statistical fiber misalignment, but cannot provide the local fields. Fully random fiber distribution is presented as a special case using the proposed micromechanical method. Results are given that illustrate the effects of various amounts of fiber misalignment in terms of the standard deviations of in-plane and out-of-plane misalignment angles, where normal distributions have been employed. Damage initiation envelopes, local fields, effective moduli, and strengths are predicted for polymer and ceramic matrix composites with given normal distributions of misalignment angles, as well as fully random fiber orientation.

Ultrasonic Nondestructive Evaluation of Damage in Continuous Fiber Composites

DTIC Science & Technology

1989-01-01

Security Classification) Ultrasonic Nondestructive Evalustion of Damage in Continuous Fiber Composites 12. PERSONAL AUTHOR(S) Vikram K. Kinra 13a...Attenuatiorn Composites , Damage / " UltrasonicNondestructive Evaluation. \\ ’k 19. ABSTRACT (Continue on reverse if necessary and identify by block n,,ber) A...n SIrIE -~ 2 4IiCUi’.ZIEfEi Ultrasonic nondestructive evaluation of fibre-reinforced composite materials - a review VIKRAM K KINRA and VINAY DAYAL

Fabrication of boronate-decorated polyhedral oligomeric silsesquioxanes grafted cotton fiber for the selective enrichment of nucleosides in urine.

PubMed

Gao, Li; Wei, Yinmao

2016-06-01

Various cotton fiber based boronate-affinity adsorbents are recently developed for the sample pretreatment of cis-diol-containing biomolecules, but most do not have efficient capacity due to limited binding sites on the surface of cotton fibers. To increase the density of boronate groups on the surface of cotton fiber, polyhedral oligomeric silsesquioxanes were used to modify cotton fiber to provide plentiful reactive sites for subsequent functionalization with 4-formylphenylboronic acid. The new adsorbent showed special recognition ability towards cis-diols and high adsorption capacity (175 μg/g for catechol, 250 μg/g for dopamine, 400 μg/g for adenosine). The in-pipette-tip solid-phase extraction was investigated under different conditions, including pH and ionic strength of solution, adsorbent amount, pipette times, washing solvent, and elution solvent. The in-pipette-tip solid-phase extraction coupled with high-performance liquid chromatography was used to analyze four nucleosides in urine samples. Under the optimal extraction conditions, the detection limits were determined to be between 5.1 and 6.1 ng/mL (S/N  =  3), and the linearity ranged from 20 to 500 ng/mL for these analytes. The accuracy of the analytical method was examined by studying the relative recoveries of analytes in real urine samples with recoveries varying from 83 to 104% (RSD = 3.9-10.2%, n = 3). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Modeling the roles of damage accumulation and mechanical healing on rainfall-induced landslides

NASA Astrophysics Data System (ADS)

Fan, Linfeng; Lehmann, Peter; Or, Dani

2014-05-01

The abrupt release of rainfall-induced shallow landslides is preceded by local failures that may abruptly coalesce and form a continuous failure plane within a hillslope. The mechanical status of hillslopes reflects a competition between the extent of severity of accumulated local damage during prior rainfall events and the rates of mechanically healing (i.e. regaining of strength) by closure of micro-cracks, regrowth of roots, etc. The interplay of these processes affects the initial conditions for landslide modeling and shapes potential failure patterns during future rainfall events. We incorporated these competing mechanical processes in a hydro-mechanical landslide triggering model subjected to a sequence of rainfall scenarios. The model employs the Fiber Bundle Model (FBM) with bonds (fiber bundle) with prescribed threshold linking adjacent soil columns and soil to bedrock. Prior damage was represented by a fraction of broken fibers during previous rainfall events, and the healing of broken fibers was described by strength regaining models for soil and roots at different characteristic time scales. Results show that prior damage and healing introduce highly nonlinear response to landslide triggering. For small prior damage, mechanical bonds at soil-bedrock interface may fail early in next rainfall event but lead to small perturbations onto lateral bonds without triggering a landslide. For more severe damage weakening lateral bonds, excess load due to failure at soil-bedrock interface accumulates at downslope soil columns resulting in early soil failure with patterns strongly correlated with prior damage distribution. Increasing prior damage over the hillslope decreases the volume of first landslide and prolongs the time needed to trigger the second landslide due to mechanical relaxation of the system. The mechanical healing of fibers diminishes effects of prior damage on the time of failure, and shortens waiting time between the first and second landslides. These findings highlight the need to improve definition of initial conditions and the shortcomings of assuming pristine hillslopes.

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.

Seismic damage identification using multi-line distributed fiber optic sensor system

NASA Astrophysics Data System (ADS)

Ou, Jinping; Hou, Shuang

2005-06-01

Determination of the actual nonlinear inelastic response mechanisms developed by civil structures such as buildings and bridges during strong earthquakes and post-earthquake damage assessment of these structures represent very difficult challenges for earthquake structural engineers. One of the main reasons is that the traditional sensor can't serve for such a long period to cover an earthquake and the seismic damage location in the structure can't be predicted in advance definitely. It is thought that the seismic damage of reinforced concrete (RC) structure can be related to the maximum response the structure, which can also be related to the cracks on the concrete. A distributed fiber optic sensor was developed to detect the cracks on the reinforced concrete structure under load. Fiber optic couples were used in the sensor system to extend the sensor system's capacity from one random point detection to more. An optical time domain reflectometer (OTDR) is employed for interrogation of the sensor signal. Fiber optic sensors are attached on the surface of the concrete by the epoxy glue. By choosing the strength of epoxy, the damage state of the concrete can be responded to the occurrence of the Fresnel scattering in the fiber optic sensor. Experiments involved monotonic loading to failure. Finally, the experimental results in terms of crack detection capability are presented and discussed.

A Finite Element Analysis of a Carbon Fiber Composite Micro Air Vehicle Wing

DTIC Science & Technology

2012-03-22

3. Errors in the manufacturing of the laminate resulting in errors in ply orientation. Each of these was examined in order to determine a root ...material properties. 4.2.4. Vein Width The widths of the individual veins of the manufactured wing were varied linearly from root to tip of the...wing. In the sizing of the engineered wing, the width of the veins were varied linearly from the root of the vein to the tip. For manufacturing

Large core fiber optic cleaver

DOEpatents

Halpin, John M.

1996-01-01

The present invention relates to a device and method for cleaving optical fibers which yields cleaved optical fiber ends possessing high damage threshold surfaces. The device can be used to cleave optical fibers with core diameters greater than 400 .mu.m.

Fiber Optic Sensor Embedment Study for Multi-Parameter Strain Sensing

PubMed Central

Drissi-Habti, Monssef; Raman, Venkadesh; Khadour, Aghiad; Timorian, Safiullah

2017-01-01

The fiber optic sensors (FOSs) are commonly used for large-scale structure monitoring systems for their small size, noise free and low electrical risk characteristics. Embedded fiber optic sensors (FOSs) lead to micro-damage in composite structures. This damage generation threshold is based on the coating material of the FOSs and their diameter. In addition, embedded FOSs are aligned parallel to reinforcement fibers to avoid micro-damage creation. This linear positioning of distributed FOS fails to provide all strain parameters. We suggest novel sinusoidal sensor positioning to overcome this issue. This method tends to provide multi-parameter strains in a large surface area. The effectiveness of sinusoidal FOS positioning over linear FOS positioning is studied under both numerical and experimental methods. This study proves the advantages of the sinusoidal positioning method for FOS in composite material’s bonding. PMID:28333117

Injection-Molded Long-Fiber Thermoplastic Composites: From Process Modeling to Prediction of Mechanical Properties

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

Nguyen, Ba Nghiep; Kunc, Vlastimil; Jin, Xiaoshi

2013-12-18

This article illustrates the predictive capabilities for long-fiber thermoplastic (LFT) composites that first simulate the injection molding of LFT structures by Autodesk® Simulation Moldflow® Insight (ASMI) to accurately predict fiber orientation and length distributions in these structures. After validating fiber orientation and length predictions against the experimental data, the predicted results are used by ASMI to compute distributions of elastic properties in the molded structures. In addition, local stress-strain responses and damage accumulation under tensile loading are predicted by an elastic-plastic damage model of EMTA-NLA, a nonlinear analysis tool implemented in ABAQUS® via user-subroutines using an incremental Eshelby-Mori-Tanaka approach. Predictedmore » stress-strain responses up to failure and damage accumulations are compared to the experimental results to validate the model.« less

Light triggered interfacial damage self-healing of poly(p-phenylene benzobisoxazole) fiber composites.

PubMed

Hu, Zhen; Shao, Qing; Huang, Yudong; Yu, Long; Zhang, Dayu; Xu, Xirong; Lin, Jing; Liu, Hu; Guo, Zhanhu

2018-05-04

The interfacial microcracks in the resin matrix composites are difficult to be detected and repaired. However, the self-healing concept provides opportunities to fabricate composites with unusual properties. In the present study, photothermal conversion Ag-Cu 2 S nanoparticles were immobilized onto poly(p-phenylene benzobisoxazole) (PBO) fibers via a polydopamine chemistry. Benefitting from the photothermal effects of Ag-Cu 2 S, the obtained PBO fibers (Ag-Cu 2 S-PBO) efficiently converted the light energy into heat under Xenon lamp irradiation. Then, single PBO fiber composites were prepared using thermoplastic polyurethane as the matrix. It was found that the interfacial damage caused by single fiber pull-out was simply self-healed by Xe light irradiation. This wonderful interfacial damage self-healing property was mainly attributed to the in situ heating generation via photothermal effects of Ag-Cu 2 S in the composite interface. This paper reports a novel strategy to construct advanced composites with light-triggered self-healing properties, which will provide inspiration for preparing high performance composite materials.