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Sample records for ablated wall material

  1. Experiment and analysis of ablation and condensation in NIF first wall materials

    SciTech Connect

    Jin, H.; Peterson, P.F.; Turner, R.E.; Anderson, A.T.

    1996-06-14

    Experiments were performed on Nova at Lawrence Livermore National Laboratory to study the ablation and condensation process of National Ignition Facility (NIF) first wall materials. Plates of candidate first wall materials (SiO{sub 2}, B{sub 4}, and Al{sub 2}O{sub 3}) were exposed to x-rays from hohlraums in the Nova chamber. Ablated material was collected and measured on a receiving plate which was blocked form direct x-ray exposure. This article presents the results form these experiments and comparisons with predictions from numerical simulations The net condensation flux was calculated using the TSUNAMI code, which was modified to incorporate the feature of condensation boundaries.

  2. Modeling and experiments of x-ray ablation of National Ignition Facility first wall materials

    SciTech Connect

    Anderson, A.T.; Burnham, A.K.; Tobin, M.T.; Peterson, P.F.

    1996-06-04

    This paper discusses results of modeling and experiments on the x-ray response of selected materials relevant to NIF target chamber design. X-ray energy deposition occurs in such small characteristic depths (on the order of a micron) that thermal conduction and hydrodynamic motion significantly affect the material response, even during the typical 10-ns pulses. The finite-difference ablation model integrates four separate processes: x-ray energy deposition, heat conduction, hydrodynamics, and surface vaporization. Experiments have been conducted at the Nova laser facility in Livermore on response of various materials to NIF-relevant x-ray fluences. Fused silica, Si nitride, B carbide, B, Si carbide, C, Al2O3, and Al were tested. Response was diagnosed using post-shot examinations of the surfaces with SEM and atomic force microscopes. Judgements were made about the dominant removal mechanisms for each material; relative importances of these processes were also studied with the x-ray response model.

  3. Moldable cork ablation material

    NASA Technical Reports Server (NTRS)

    1977-01-01

    A successful thermal ablative material was manufactured. Moldable cork sheets were tested for density, tensile strength, tensile elongation, thermal conductivity, compression set, and specific heat. A moldable cork sheet, therefore, was established as a realistic product.

  4. Method of manufacturing hollow members having uniform wall thickness through use of ablation

    DOEpatents

    Anderson, Paul R.; Downs, Raymond L.; Henderson, Timothy M.

    1982-01-01

    A method of manufacturing a hollow structure of uniform wall thickness comprising the steps of selecting or forming a precursor having one wall surface of desired geometry, treating a portion of the precursor consisting of the one wall surface and a uniform depth of material beneath the wall surface to increase resistance to ablation, and then removing by ablation and discarding the remaining or untreated portion of the precursor.

  5. Radiofrequency ablation of abdominal wall endometrioma.

    PubMed

    Carrafiello, Gianpaolo; Fontana, Federico; Pellegrino, Carlo; Mangini, Monica; Cabrini, Luca; Mariani, Davide; Piacentino, Filippo; Cuffari, Salvatore; Laganà, Domenico; Fugazzola, Carlo

    2009-11-01

    Extraperitoneal endometriosis is the presence of ectopic, functional endometrium outside the peritoneal cavity, and its occurrence is exceedingly rare. Diagnostic imaging--including ultrasound, duplex ultrasonography, and magnetic resonance imaging--in the preoperative assessment of patients with suspected abdominal wall endometriosis (AWE) is helpful for detection and accurate determination of the extent of disease. The treatment of choice for AWE is surgical excision. In addition, medical therapies can be used. We present one case of AWE treated with percutaneous radiofrequency ablation under ultrasound guidance. There were no major complications, and the patient's symptoms improved. In selected patients, radiofrequency ablation can be used safely for the treatment of AWE; however, further studies are needed to confirm this hypothesis. PMID:19184197

  6. Rail gun performance and plasma characteristics due to wall ablation

    NASA Technical Reports Server (NTRS)

    Ray, P. K.

    1986-01-01

    The experiment of Bauer, et al. (1982) is analyzed by considering wall ablation and viscous drag in the plasma. Plasma characteristics are evaluated through a simple fluid-mechanical analysis considering only wall ablation. By equating the energy dissipated in the plasma with the radiation heat loss, the average properties of the plasma are determined as a function of time.

  7. Performance loss due to wall ablation in plasma armature railguns

    NASA Astrophysics Data System (ADS)

    Parker, J. V.; Parsons, W. M.; Cummings, C. E.; Fox, W. E.

    1985-07-01

    Parametric measurements have been performed on a plasma armature railgun at Los Alamos. The railgun is extensively instrumented for studies of the projectile motion and its interaction with the plasma armature. The most important parameter, driving current, was varied from 100 kA to 400 kA. Additional parameters investigated include current waveform, injection velocity, injection gas, wall insulation material, and initial pressure. For all combinations of parameters investigated, the measured performance was substantially below theoretical predictions. A strong correlation was found between performance loss and abnormal plasma armature features such as multiple arc formation, or separation of the armature from the projectile. In extreme cases, the plasma armature was observed to come to rest inside the railgun. A plasma armature model has been developed which successfully accounts for the measured performance loss and for many of the abnormal plasma armature features. By incorporating the ablation of wall material into the armature plasma this model predicts two parasitic forces that dominate the motion of the armature at high velocity. One force is the inertial drag term m dot sub a v. The other is frictional drag between the hot, turbulent plasma and the walls, which increases M sub a v squared. Simple scaling relations, which incorporate the plasma armature model, show that velocities less than 10 km/s will be extremely difficult to achieve with plasma armature railguns unless the effects of ablation are eliminated or carefully controlled.

  8. Effects of material composition on the ablation performance of low density elastomeric ablators

    NASA Technical Reports Server (NTRS)

    Tompkins, S. S.; Kabana, W. P.

    1973-01-01

    The ablation performance of materials composed of various concentrations of nylon, hollow silica spheres, hollow phenolic spheres, and four elastomeric resins was determined. Both blunt-body and flat-panel specimens were used, the cold-wall heating-rate ranges being 0.11 to 0.8 MW/sq m, respectively. The corresponding surface pressure ranges for these tests were 0.017 to 0.037 atmosphere and 0.004 to 0.005 atmosphere. Some of the results show that (1) the addition of nylon significantly improved the ablation performance, but the nylon was not compatible with one resin system; (2) panel and blunt-body specimen data do not show the same effect of phenolic sphere content on ablation effectiveness; and (3) there appears to be an optimum concentration of hollow silica spheres for good ablation performance. The composition of an efficient, nonproprietary ablator for lifting body application is identified and the ablation performance of this ablator is compared with the performance of three commercially available materials.

  9. Ablative system

    NASA Technical Reports Server (NTRS)

    Gray, V. H. (Inventor)

    1973-01-01

    A carrier liquid containing ablative material bodies is connected to a plenum chamber wall with openings to a high temperature environment. The liquid and bodies pass through the openings of the wall to form a self replacing ablative surface. The wall is composed of honeycomb layers, spheres containing ablative whiskers or wads, and a hardening catalyst for the carrier liquid. The wall also has woven wicks of ablative material fibers that extend through the wall openings and into plenum chamber which contains the liquid.

  10. Thermal Ablation Modeling for Silicate Materials

    NASA Technical Reports Server (NTRS)

    Chen, Yih-Kanq

    2016-01-01

    A general thermal ablation model for silicates is proposed. The model includes the mass losses through the balance between evaporation and condensation, and through the moving molten layer driven by surface shear force and pressure gradient. This model can be applied in the ablation simulation of the meteoroid and the glassy ablator for spacecraft Thermal Protection Systems. Time-dependent axisymmetric computations are performed by coupling the fluid dynamics code, Data-Parallel Line Relaxation program, with the material response code, Two-dimensional Implicit Thermal Ablation simulation program, to predict the mass lost rates and shape change. The predicted mass loss rates will be compared with available data for model validation, and parametric studies will also be performed for meteoroid earth entry conditions.

  11. Femtosecond lasers for machining of transparent, brittle materials: ablative vs. non-ablative femtosecond laser processing

    NASA Astrophysics Data System (ADS)

    Hendricks, F.; Matylitsky, V. V.

    2016-03-01

    This paper focuses on precision machining of transparent materials by means of ablative and non-ablative femtosecond laser processing. Ablation technology will be compared with a newly developed patent pending non-ablative femtosecond process, ClearShapeTM, using the Spectra-Physics Spirit industrial femtosecond laser.

  12. Thermal Ablation Modeling for Silicate Materials

    NASA Technical Reports Server (NTRS)

    Chen, Yih-Kanq

    2016-01-01

    A thermal ablation model for silicates is proposed. The model includes the mass losses through the balance between evaporation and condensation, and through the moving molten layer driven by surface shear force and pressure gradient. This model can be applied in ablation simulations of the meteoroid or glassy Thermal Protection Systems for spacecraft. Time-dependent axi-symmetric computations are performed by coupling the fluid dynamics code, Data-Parallel Line Relaxation program, with the material response code, Two-dimensional Implicit Thermal Ablation simulation program, to predict the mass lost rates and shape change. For model validation, the surface recession of fused amorphous quartz rod is computed, and the recession predictions reasonably agree with available data. The present parametric studies for two groups of meteoroid earth entry conditions indicate that the mass loss through moving molten layer is negligibly small for heat-flux conditions at around 1 MW/cm(exp. 2).

  13. Alternate nozzle ablative materials program

    NASA Technical Reports Server (NTRS)

    Kimmel, N. A.

    1984-01-01

    Four subscale solid rocket motor tests were conducted successfully to evaluate alternate nozzle liner, insulation, and exit cone structural overwrap components for possible application to the Space Shuttle Solid Rocket Motor (SRM) nozzle asasembly. The 10,000 lb propellant motor tests were simulated, as close as practical, the configuration and operational environment of the full scale SRM. Fifteen PAN based and three pitch based materials had no filler in the phenolic resin, four PAN based materials had carbon microballoons in the resin, and the rest of the materials had carbon powder in the resin. Three nozzle insulation materials were evaluated; an aluminum oxide silicon oxide ceramic fiber mat phenolic material with no resin filler and two E-glass fiber mat phenolic materials with no resin filler. It was concluded by MTI/WD (the fabricator and evaluator of the test nozzles) and NASA-MSFC that it was possible to design an alternate material full scale SRM nozzle assembly, which could provide an estimated 360 lb increased payload capability for Space Shuttle launches over that obtainable with the current qualified SRM design.

  14. New Combined Laser Ablation Platform Determines Cell Wall Chemistry (Fact Sheet)

    SciTech Connect

    Not Available

    2011-09-01

    NREL has designed and developed a combined laser ablation/pulsed sample introduction/mass spectrometry platform that integrates pyrolysis and/or laser ablation with resonance-enhanced multiphoton ionization (REMPI) time-of-flight mass spectrometry. Using this apparatus, we can measure the cell wall chemical composition of untreated biomass materials. Understanding the chemical composition of untreated biomass is key to both the biochemical and thermochemical conversion of lignocellulosic biomass to biofuels. In the biochemical conversion process, the new technique provides a better understanding of the chemistry of lignin and will improve accessibility to plant sugars. In thermochemical conversion, the information provided by the new technique may help to reduce the formation of unwanted byproducts during gasification. NREL validated the ability of the system to detect pyrolysis products from plant materials using poplar, a potentially high-impact bioenergy feedstock. In the technique, biomass vapors are produced by laser ablation using the 3rd harmonic of an Nd:YAG laser (355 nm). The resulting vapors are entrained in a free jet expansion of helium, then skimmed and introduced into an ionization region. REMPI is used to ionize the vapors because it is highly sensitive for detecting lignin and aromatic metabolites. The laser ablation method was used to selectively volatilize specific plant tissues and detect lignin-based products from the vapors with enhanced sensitivity. This will allow the determination of lignin distribution in future biomass studies.

  15. Analysis of iodinated contrast delivered during thermal ablation: is material trapped in the ablation zone?

    NASA Astrophysics Data System (ADS)

    Wu, Po-hung; Brace, Chris L.

    2016-08-01

    Intra-procedural contrast-enhanced CT (CECT) has been proposed to evaluate treatment efficacy of thermal ablation. We hypothesized that contrast material delivered concurrently with thermal ablation may become trapped in the ablation zone, and set out to determine whether such an effect would impact ablation visualization. CECT images were acquired during microwave ablation in normal porcine liver with: (A) normal blood perfusion and no iodinated contrast, (B) normal perfusion and iodinated contrast infusion or (C) no blood perfusion and residual iodinated contrast. Changes in CT attenuation were analyzed from before, during and after ablation to evaluate whether contrast was trapped inside of the ablation zone. Visualization was compared between groups using post-ablation contrast-to-noise ratio (CNR). Attenuation gradients were calculated at the ablation boundary and background to quantitate ablation conspicuity. In Group A, attenuation decreased during ablation due to thermal expansion of tissue water and water vaporization. The ablation zone was difficult to visualize (CNR  =  1.57  ±  0.73, boundary gradient  =  0.7  ±  0.4 HU mm‑1), leading to ablation diameter underestimation compared to gross pathology. Group B ablations saw attenuation increase, suggesting that iodine was trapped inside the ablation zone. However, because the normally perfused liver increased even more, Group B ablations were more visible than Group A (CNR  =  2.04  ±  0.84, boundary gradient  =  6.3  ±  1.1 HU mm‑1) and allowed accurate estimation of the ablation zone dimensions compared to gross pathology. Substantial water vaporization led to substantial attenuation changes in Group C, though the ablation zone boundary was not highly visible (boundary gradient  =  3.9  ±  1.1 HU mm‑1). Our results demonstrate that despite iodinated contrast being trapped in the ablation zone, ablation visibility

  16. Analysis of iodinated contrast delivered during thermal ablation: is material trapped in the ablation zone?

    PubMed

    Wu, Po-Hung; Brace, Chris L

    2016-08-21

    Intra-procedural contrast-enhanced CT (CECT) has been proposed to evaluate treatment efficacy of thermal ablation. We hypothesized that contrast material delivered concurrently with thermal ablation may become trapped in the ablation zone, and set out to determine whether such an effect would impact ablation visualization. CECT images were acquired during microwave ablation in normal porcine liver with: (A) normal blood perfusion and no iodinated contrast, (B) normal perfusion and iodinated contrast infusion or (C) no blood perfusion and residual iodinated contrast. Changes in CT attenuation were analyzed from before, during and after ablation to evaluate whether contrast was trapped inside of the ablation zone. Visualization was compared between groups using post-ablation contrast-to-noise ratio (CNR). Attenuation gradients were calculated at the ablation boundary and background to quantitate ablation conspicuity. In Group A, attenuation decreased during ablation due to thermal expansion of tissue water and water vaporization. The ablation zone was difficult to visualize (CNR  =  1.57  ±  0.73, boundary gradient  =  0.7  ±  0.4 HU mm(-1)), leading to ablation diameter underestimation compared to gross pathology. Group B ablations saw attenuation increase, suggesting that iodine was trapped inside the ablation zone. However, because the normally perfused liver increased even more, Group B ablations were more visible than Group A (CNR  =  2.04  ±  0.84, boundary gradient  =  6.3  ±  1.1 HU mm(-1)) and allowed accurate estimation of the ablation zone dimensions compared to gross pathology. Substantial water vaporization led to substantial attenuation changes in Group C, though the ablation zone boundary was not highly visible (boundary gradient  =  3.9  ±  1.1 HU mm(-1)). Our results demonstrate that despite iodinated contrast being trapped in the ablation zone, ablation visibility

  17. Materials characterization on efforts for ablative materials

    NASA Technical Reports Server (NTRS)

    Tytula, Thomas P.; Schad, Kristin C.; Swann, Myles H.

    1992-01-01

    Experimental efforts to develop a new procedure to measure char depth in carbon phenolic nozzle material are described. Using a Shor Type D Durometer, hardness profiles were mapped across post fired sample blocks and specimens from a fired rocket nozzle. Linear regression was used to estimate the char depth. Results are compared to those obtained from computed tomography in a comparative experiment. There was no significant difference in the depth estimates obtained by the two methods.

  18. A numerical algorithm for magnetohydrodynamics of ablated materials.

    PubMed

    Lu, Tianshi; Du, Jian; Samulyak, Roman

    2008-07-01

    A numerical algorithm for the simulation of magnetohydrodynamics in partially ionized ablated material is described. For the hydro part, the hyperbolic conservation laws with electromagnetic terms is solved using techniques developed for free surface flows; for the electromagnetic part, the electrostatic approximation is applied and an elliptic equation for electric potential is solved. The algorithm has been implemented in the frame of front tracking, which explicitly tracks geometrically complex evolving interfaces. An elliptic solver based on the embedded boundary method were implemented for both two- and three-dimensional simulations. A surface model on the interface between the solid target and the ablated vapor has also been developed as well as a numerical model for the equation of state which accounts for atomic processes in the ablated material. The code has been applied to simulations of the pellet ablation in a magnetically confined plasma and the laser-ablated plasma plume expansion in magnetic fields. PMID:19051925

  19. Modeling Ablation of Fibrous Materials from Bulk to Knudsen Regime

    NASA Technical Reports Server (NTRS)

    Lachaud, Jean; Mansour, Nagi N.

    2008-01-01

    Material-environment interactions are analyzed at microscopic scale to explain the lower than expected density observed by post-flight analysis of the char layer on the Stardust shield. Mass transfer, ablation (oxidation), and surface recession of fibrous material is simulated in 3D using a Monte-Carlo simulation tool. Ablation is found to occur either at the surface or in volume depending on Knudsen and Thiele number values. This study supports the idea of volume ablation followed by possible carbon fiber spallation that may explain post-flight analyses.

  20. Modeling ultrashort-pulse laser ablation of dielectric materials

    SciTech Connect

    Christensen, B. H.; Balling, P.

    2009-04-15

    An approach to modeling ablation thresholds and depths in dielectric materials is proposed. The model is based on the multiple-rate-equation description suggested by Rethfeld [Phys. Rev. Lett. 92, 187401 (2004)]. This model has been extended to include a description of the propagation of the light into the dielectric sample. The generic model is based on only a few experimental quantities that characterize the native material. A Drude model describing the evolution of the dielectric constant owing to an excitation of the electrons in the material is applied. The model is compared to experimental ablation data for different dielectric materials from the literature.

  1. Ablative Laser Propulsion Using Multi-Layered Material Systems

    NASA Technical Reports Server (NTRS)

    Nehls, Mary; Edwards, David; Gray, Perry; Schneider, T.

    2002-01-01

    Experimental investigations are ongoing to study the force imparted to materials when subjected to laser ablation. When a laser pulse of sufficient energy density impacts a material, a small amount of the material is ablated. A torsion balance is used to measure the momentum produced by the ablation process. The balance consists of a thin metal wire with a rotating pendulum suspended in the middle. The wire is fixed at both ends. Recently, multi-layered material systems were investigated. These multi-layered materials were composed of a transparent front surface and opaque sub surface. The laser pulse penetrates the transparent outer surface with minimum photon loss and vaporizes the underlying opaque layer.

  2. Microscopic Scale Simulation of the Ablation of Fibrous Materials

    NASA Technical Reports Server (NTRS)

    Lachaud, Jean Romain; Mansour, Nagi N.

    2010-01-01

    Ablation by oxidation of carbon-fiber preforms impregnated in carbonized phenolic matrix is modeled at microscopic scale. Direct numerical simulations show that the carbonized phenolic matrix ablates in volume leaving the carbon fibers exposed. This is due to the fact that the reactivity of carbonized phenolic is higher than the reactivity of carbon fibers. After the matrix is depleted, the fibers ablate showing progressive reduction of their diameter. The overall material recession occurs when the fibers are consumed. Two materials with the same carbon-fiber preform, density and chemical composition, but with different matrix distributions are studied. These studies show that at moderate temperatures (< 1000 K) the microstructure of the material influences its recession rate; a fact that is not captured by current models that are based on chemical composition only. Surprisingly, the response of these impregnated-fiber materials is weakly dependent on the microstructure at very high temperatures (e.g., Stardust peak heating conditions: 3360K).

  3. Resin-Impregnated Carbon Ablator: A New Ablative Material for Hyperbolic Entry Speeds

    NASA Technical Reports Server (NTRS)

    Esper, Jaime; Lengowski, Michael

    2012-01-01

    Ablative materials are required to protect a space vehicle from the extreme temperatures encountered during the most demanding (hyperbolic) atmospheric entry velocities, either for probes launched toward other celestial bodies, or coming back to Earth from deep space missions. To that effect, the resin-impregnated carbon ablator (RICA) is a high-temperature carbon/phenolic ablative thermal protection system (TPS) material designed to use modern and commercially viable components in its manufacture. Heritage carbon/phenolic ablators intended for this use rely on materials that are no longer in production (i.e., Galileo, Pioneer Venus); hence the development of alternatives such as RICA is necessary for future NASA planetary entry and Earth re-entry missions. RICA s capabilities were initially measured in air for Earth re-entry applications, where it was exposed to a heat flux of 14 MW/sq m for 22 seconds. Methane tests were also carried out for potential application in Saturn s moon Titan, with a nominal heat flux of 1.4 MW/sq m for up to 478 seconds. Three slightly different material formulations were manufactured and subsequently tested at the Plasma Wind Tunnel of the University of Stuttgart in Germany (PWK1) in the summer and fall of 2010. The TPS integrity was well preserved in most cases, and results show great promise.

  4. Water absorption and desorption in shuttle ablator and insulation materials

    NASA Technical Reports Server (NTRS)

    Whitaker, A. F.; Smith, C. F.; Wooden, V. A.; Cothren, B. E.; Gregory, H.

    1982-01-01

    Shuttle systems ablator and insulation materials underwent water soak with subsequent water desorption in vacuum. Water accumulation in these materials after a soak for 24 hours ranged from +1.1% for orbiter tile to +161% for solid rocket booster MSA-1. After 1 minute in vacuum, water retention ranged from none in the orbiter tile to +70% for solid rocket booster cork.

  5. Development of moldable carbonaceous materials for ablative rocket nozzles.

    NASA Technical Reports Server (NTRS)

    Lockhart, R. J.; Bortz, S. A.; Schwartz, M. A.

    1972-01-01

    Description of a materials system developed for use as low-cost ablative nozzles for NASA's 260-in. solid rocket motor. Petroleum coke and carbon black fillers were employed; high density was achieved by controlling particle size distribution. An alumina catalyzed furfuryl ester resin which produced high carbon residues after pyrolysis was employed as the binder. Staple carbon fibers improved the strength and crack resistance of molded bodies. In static firing tests of two subscale nozzles, this material compared favorably in erosion rate with several other ablative systems.

  6. Transcatheter Arterial Embolization for Tumor Seeding in the Chest Wall After Radiofrequency Ablation for Hepatocellular Carcinoma

    SciTech Connect

    Shibata, Toshiya Shibata, Toyomichi; Maetani, Yoji; Kubo, Takeshi; Nishida, Naoshi; Itoh, Kyo

    2006-06-15

    Tumor seeding in the chest wall was depicted at follow-up CT obtained 9 months after radiofrequency ablation for hepatocellular carcinoma. Transcatheter arterial embolization was successfully performed, injecting emulsion of 10 mg of epirubicin and 1 ml of iodized oil followed by gelatin sponge particles via the microcatheter placed in the right eleventh intercostal artery. The patient died of tumor growth in the liver one year after the embolization, but no progression of the tumor seeding was noted during the follow-up period. We conclude that transcatheter arterial embolization was effective for the control of tumor seeding after radiofrequency ablation for hepatocellular carcinoma.

  7. Solid material evaporation into an ECR source by laser ablation

    SciTech Connect

    Harkewicz, R.; Stacy, J.; Greene, J.; Pardo, R.C.

    1993-09-01

    In an effort to explore new methods of producing ion beams from solid materials, we are attempting to develop a laser-ablation technique for evaporating materials directly into an ECR ion source plasma. A pulsed NdYaG laser with approximately 25 watts average power and peak power density on the order of 10{sup 7} W/cm{sup 2} has been used off-line to measure ablation rates of various materials as a function of peak laser power. The benefits anticipated from the successful demonstration of this technique include the ability to use very small quantities of materials efficiently, improved material efficiency of incorporation into the ECR plasma, and decoupling of the material evaporation process from the ECR source tuning operation. Here we report on the results of these tests and describe the design for incorporating such a system directly with the ATLAS PII-ECR ion source.

  8. Review of Laser Ablation Process for Single Wall Carbon Nanotube Production

    NASA Technical Reports Server (NTRS)

    Arepalli, Sivaram

    2003-01-01

    Different types of lasers are now routinely used to prepare single wall carbon nanotubes (SWCNTs). The original method developed by researchers at Rice University utilized a "double pulse laser oven" process. A graphite target containing about 1 atomic percent of metal catalysts is ablated inside a 1473K oven using laser pulses (10 ns pulse width) in slow flowing argon. Two YAG lasers with a green pulse (532 nm) followed by an IR pulse (1064 nm) with a 50 ns delay are used for ablation. This set up produced single wall carbon nanotube material with about 70% purity having a diameter distribution peaked around 1.4 nm. The impurities consist of fullerenes, metal catalyst clusters (10 to 100 nm diameter) and amorphous carbon. The rate of production with the initial set up was about 60 mg per hour with 10Hz laser systems. Several researchers have used variations of the lasers to improve the rate, consistency and study effects of different process parameters on the quality and quantity of SWCNTs. These variations include one to three YAG laser systems (Green, Green and IR), different pulse widths (nano to microseconds as well as continuous) and different laser wavelengths (Alexandrite, CO, CO2, free electron lasers in the near to far infrared). It is noted that yield from the single laser (Green or IR) systems is only a fraction of the two laser systems. The yield seemed to scale up with the repetition rate of the laser systems (10 to 60 Hz) and depended on the beam uniformity and quality of the laser pulses. The shift to longer wavelength lasers (free electron, CO and CO2) did not improve the quality, but increased the rate of production because these lasers are either continuous (CW) or high repetition rate pulses (kHz to MHz). The average power and the peak power of the lasers seem to influence the yields. Very high peak powers (MegaWatts per square centimeter) are noted to increase ablation of bigger particles with reduced yields of SWCNTs. Increased average powers

  9. Laser Ablation of Materials for Propulsion of Spacecraft

    NASA Technical Reports Server (NTRS)

    Edwards, David L.; Carruth, Ralph; Campbell, Jonathan; Gray, Perry

    2004-01-01

    A report describes experiments performed as part of a continuing investigation of the feasibility of laser ablation of materials as a means of propulsion for small spacecraft. In each experiment, a specimen of ablative material was mounted on a torsion pendulum and irradiated with a laser pulse having an energy of 5 J. The amplitude of the resulting rotation of the torsion pendulum was taken to be an indication of the momentum transferred from the laser beam. Of the ablative materials tested, aluminum foils yielded the smallest rotation amplitudes of the order of 10 degrees. Black coating materials yielded rotation amplitudes of the order of 90 degrees. Samples of silver coated with a fluorinated ethylene propylene (FEP) copolymer yielded the largest rotation amplitudes 6 to 8 full revolutions. The report presents a theory involving heating of a confined plasma followed by escape of the plasma to explain the superior momentum transfer performance of the FEP specimens. It briefly discusses some concepts for optimizing designs of spacecraft engines to maximize the thrust obtainable by exploiting the physical mechanisms of the theory. Also discussed is the use of laser-ablation engines with other types of spacecraft engines.

  10. Patient-specific left atrial wall-thickness measurement and visualization for radiofrequency ablation

    NASA Astrophysics Data System (ADS)

    Inoue, Jiro; Skanes, Allan C.; White, James A.; Rajchl, Martin; Drangova, Maria

    2014-03-01

    INTRODUCTION: For radiofrequency (RF) catheter ablation of the left atrium, safe and effective dosing of RF energy requires transmural left atrium ablation without injury to extra-cardiac structures. The thickness of the left atrial wall may be a key parameter in determining the appropriate amount of energy to deliver. While left atrial wall-thickness is known to exhibit inter- and intra-patient variation, this is not taken into account in the current clinical workflow. Our goal is to develop a tool for presenting patient-specific left atrial thickness information to the clinician in order to assist in the determination of the proper RF energy dose. METHODS: We use an interactive segmentation method with manual correction to segment the left atrial blood pool and heart wall from contrast-enhanced cardiac CT images. We then create a mesh from the segmented blood pool and determine the wall thickness, on a per-vertex basis, orthogonal to the mesh surface. The thickness measurement is visualized by assigning colors to the vertices of the blood pool mesh. We applied our method to 5 contrast-enhanced cardiac CT images. RESULTS: Left atrial wall-thickness measurements were generally consistent with published thickness ranges. Variations were found to exist between patients, and between regions within each patient. CONCLUSION: It is possible to visually determine areas of thick vs. thin heart wall with high resolution in a patient-specific manner.

  11. Improved ablative materials for the ASRM nozzle

    NASA Technical Reports Server (NTRS)

    Canfield, A.; Clinton, R. G.; Armour, W.; Koenig, J.

    1992-01-01

    Rayon precursor carbon-cloth phenolic was developed more than 30 years ago and is used in most nozzles today including the Poseidon, Trident, Peacekeeper, Small ICBM, Space Shuttle, and numerous tactical and space systems. Specifications and manufacturing controls were placed on these materials and, once qualified, a no-change policy was instituted. The current material is acceptable; however, prepreg variability does not always accommodate the requirements of automation. The advanced solid rocket motor requires material with less variability for automated manufacturing. An advanced solid rocket motor materials team, composed of NASA, Thiokol, Aerojet, SRI, and Lockheed specialists, along with materials suppliers ICI Fiberite/Polycarbon, BP Chemicals/Hitco, and Amoco, embarked on a program to improve the current materials. The program consisted of heat treatment studies and standard and low-density material improvements evaluation. Improvements evaluated included fiber/fabric heat treatments, weave variations, resin application methods, process controls, and monitors.

  12. Resonant ablation of single-wall carbon nanotubes by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Arutyunyan, N. R.; Komlenok, M. S.; Kononenko, V. V.; Pashinin, V. P.; Pozharov, A. S.; Konov, V. I.; Obraztsova, E. D.

    2015-01-01

    The thin 50 nm film of bundled arc-discharge single-wall carbon nanotubes was irradiated by femtosecond laser pulses with wavelengths 675, 1350 and 1745 nm corresponding to the absorption band of metallic nanotubes E11M, to the background absorption and to the absorption band of semiconducting nanotubes E11S, respectively. The aim was to induce a selective removal of nanotubes of specific type from the bundled material. Similar to conducted thermal heating experiments, the effect of laser irradiation results in suppression of all radial breathing modes in the Raman spectra, with preferential destruction of the metallic nanotubes with diameters less than 1.26 nm and of the semiconducting nanotubes with diameters 1.36 nm. However, the etching rate of different nanotubes depends on the wavelength of the laser irradiation. It is demonstrated that the relative content of nanotubes of different chiralities can be tuned by a resonant laser ablation of undesired nanotube fraction. The preferential etching of the resonant nanotubes has been shown for laser wavelengths 675 nm (E11M) and 1745 nm (E11S).

  13. Laser ablation process for single-walled carbon nanotube production

    NASA Technical Reports Server (NTRS)

    Arepalli, Sivaram

    2004-01-01

    Different types of lasers are now routinely used to prepare single-walled carbon nanotubes. The original method developed by researchers at Rice University used a "double-pulse laser oven" process. Several researchers have used variations of the lasers to include one-laser pulse (green or infrared), different pulse widths (ns to micros as well as continuous wave), and different laser wavelengths (e.g., CO2, or free electron lasers in the near to far infrared). Some of these variations are tried with different combinations and concentrations of metal catalysts, buffer gases (e.g., helium), oven temperatures, flow conditions, and even different porosities of the graphite targets. This article is an attempt to cover all these variations and their relative merits. Possible growth mechanisms under these different conditions will also be discussed.

  14. Numerical studies of wall-plasma interactions and ionization phenomena in an ablative pulsed plasma thruster

    NASA Astrophysics Data System (ADS)

    Yang, Lei; Zeng, Guangshang; Tang, Haibin; Huang, Yuping; Liu, Xiangyang

    2016-07-01

    Wall-plasma interactions excited by ablation controlled arcs are very critical physical processes in pulsed plasma thrusters (PPTs). Their effects on the ionization processes of ablated vapor into discharge plasma directly determine PPT performances. To reveal the physics governing the ionization phenomena in PPT discharge, a modified model taking into account the pyrolysis effect of heated polytetrafluoroethylene propellant on the wall-plasma interactions was developed. The feasibility of the modified model was analyzed by creating a one-dimensional simulation of a rectangular ablative PPT. The wall-plasma interaction results based on this modified model were found to be more realistic than for the unmodified model; this reflects the dynamic changes of the inflow parameters during discharge in our model. Furthermore, the temporal and spatial variations of the different plasma species in the discharge chamber were numerically studied. The numerical studies showed that polytetrafluoroethylene plasma was mainly composed of monovalent ions; carbon and fluorine ions were concentrated in the upstream and downstream discharge chamber, respectively. The results based on this modified model were in good agreement with the experimental formation times of the various plasma species. A large number of short-lived and highly ionized carbon and fluorine species (divalent and trivalent ions) were created during initial discharge. These highly ionized species reached their peak density earlier than the singly ionized species.

  15. Bursting for enhanced ablation of materials

    NASA Astrophysics Data System (ADS)

    Hendow, Sami; Rea, Edward; Kosa, Nadhir; Bengtsson, Magnus; Shakir, Sami

    2014-03-01

    A significant enhancement in the rate of material removal is demonstrated using a nanosecond-pulsed UV fiber laser in multi-pulsing burst mode, as compared to the case without bursting. Percussion drilling and scribing of thin-film and bulk material tests show that, in general, laser bursts with increased pulse count and reduced pulse spacing show higher rates of material removal. A considerable improvement in removal rate is demonstrated, when bursting is applied to scribing of mono-crystalline silicon (m-Si) and up to 30% in percussion drilling speed. Likewise, improved material removal is demonstrated for scribing of thin film of indium tin oxide (ITO) on glass or metal film on sapphire. Examples of material processing are given with and without bursting at similar experimental conditions of average power, scan speed, and burst/pulse energies. Experimental results included are for m-Si, ITO thin films on glass, and metal films on sapphire.

  16. Aerothermal Testing of Woven TPS Ablative Materials

    NASA Technical Reports Server (NTRS)

    Stackpoole, Mairead; Feldman, Jay; Olson, Michael; Venkatapathy, Ethiraj

    2012-01-01

    Woven Thermal Protection Systems (WTPS) is a new TPS concept that is funded by NASAs Office of the Chief Technologist (OCT) Game Changing Division. The WTPS project demonstrates the potential for manufacturing a variety of TPS materials capable of wide ranging performances demanded by a spectrum of solar system exploration missions. Currently, missions anticipated to encounter heat fluxes in the range of 1500 4000 Watts per square centimeter are limited to using one proven material fully dense Carbon Phenolic. However, fully dense carbon phenolic is only mass efficient at heat fluxes greater than 4000 Watts per square centimeter, and current mission designs suffer this mass inefficiency for lack of an alternative mid-density TPS. WTPS not only bridges this gap but also offers a replacement for carbon phenolic, which itself requires a significant and costly redevelopment effort to re-establish its capability for use in the high heat flux missions recently prioritized in the NRC Decadal survey, including probe missions to Venus, Saturn and Neptune. This poster will summarize some recent arc jet testing to evaluate the performance of WTPS. Both mid density and fully dense WTPS test results will be presented and results compared to heritage carbon phenolic where applicable.

  17. Method for materials deposition by ablation transfer processing

    DOEpatents

    Weiner, Kurt H.

    1996-01-01

    A method in which a thin layer of semiconducting, insulating, or metallic material is transferred by ablation from a source substrate, coated uniformly with a thin layer of said material, to a target substrate, where said material is desired, with a pulsed, high intensity, patternable beam of energy. The use of a patternable beam allows area-selective ablation from the source substrate resulting in additive deposition of the material onto the target substrate which may require a very low percentage of the area to be covered. Since material is placed only where it is required, material waste can be minimized by reusing the source substrate for depositions on multiple target substrates. Due to the use of a pulsed, high intensity energy source the target substrate remains at low temperature during the process, and thus low-temperature, low cost transparent glass or plastic can be used as the target substrate. The method can be carried out atmospheric pressures and at room temperatures, thus eliminating vacuum systems normally required in materials deposition processes. This invention has particular application in the flat panel display industry, as well as minimizing materials waste and associated costs.

  18. Method for materials deposition by ablation transfer processing

    DOEpatents

    Weiner, K.H.

    1996-04-16

    A method in which a thin layer of semiconducting, insulating, or metallic material is transferred by ablation from a source substrate, coated uniformly with a thin layer of said material, to a target substrate, where said material is desired, with a pulsed, high intensity, patternable beam of energy. The use of a patternable beam allows area-selective ablation from the source substrate resulting in additive deposition of the material onto the target substrate which may require a very low percentage of the area to be covered. Since material is placed only where it is required, material waste can be minimized by reusing the source substrate for depositions on multiple target substrates. Due to the use of a pulsed, high intensity energy source the target substrate remains at low temperature during the process, and thus low-temperature, low cost transparent glass or plastic can be used as the target substrate. The method can be carried out atmospheric pressures and at room temperatures, thus eliminating vacuum systems normally required in materials deposition processes. This invention has particular application in the flat panel display industry, as well as minimizing materials waste and associated costs. 1 fig.

  19. 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.

  20. Carbon Nanotube-Enhanced Carbon-Phenenolic Ablator Material

    NASA Technical Reports Server (NTRS)

    Kikolaev, P.; Stackpoole, M.; Fan, W.; Cruden, B. A.; Waid, M.; Moloney, P.; Arepalli, S.; Arnold, J.; Partridge, H.; Yowell, L.

    2006-01-01

    This viewgraph presentation reviews the use of PICA (phenolic impregnated carbon ablator) as the selected material for heat shielding for future earth return vehicles. It briefly reviews the manufacturing of PICA and the advantages for the use of heat shielding, and then explains the reason for using Carbon Nanotubes to improve strength of phenolic resin that binds carbon fibers together. It reviews the work being done to create a carbon nanotube enhanced PICA. Also shown are various micrographic images of the various PICA materials.

  1. Numerical studies of ablation and ionization of railgun materials

    SciTech Connect

    Schnurr, N.M.; Kerrisk, J.F.

    1985-01-01

    The intense radiation from the arc in a railgun may cause vaporization and partial ionization of rail and insulator material. The mass of material added to the arc can have a significant adverse effect on projectile velocity. A numerical model has been developed to predict the change in mass of the arc as a function of several parameters. That model has been incorporated in the Los Alamos Railgun Estimator (LARGE) code and simulations have been run to assess the accuracy of the model. Analytical predictions were found to be in good agreement with experimental data for railgun tests run at Los Alamos. Ablation appears to have a significant effect on railgun performance.

  2. Mechanisms affecting kinetic energies of laser-ablated materials

    SciTech Connect

    Chen, K.R. |; Leboeuf, J.N.; Wood, R.F.; Geohegan, D.B.; Donato, J.M.; Liu, C.L.; Puretzky, A.A.

    1995-12-31

    Laser materials processing techniques are expected to have a dramatic impact on materials science and engineering in the near future and beyond. One of the main laser materials processing techniques is Pulsed Laser Deposition (PLD) for thin film growth. While experimentalists search for optimal approaches for thin film growth with pulsed laser deposition (PLD), a systematic effort in theory and modeling of various processes during PLD is needed. The quality of film deposited depends critically on the range and profile of the kinetic energy and density of the ablated plume. While it is to the advantage of pulsed laser deposition to have high kinetic energy, plumes that are too energetic causes film damage. A dynamic source effect was found to accelerate the plume expansion velocity much higher than that from a conventional free expansion model. A self-similar theory and a hydrodynamic model are developed to study this effect, which may help to explain experimentally observed high front expansion velocity. Background gas can also affect the kinetic energies. High background gas may cause the ablated materials to go backward. Experimentally observed plume splitting is also discussed.

  3. Preparation And Analysis Of Specimens Of Ablative Materials

    NASA Technical Reports Server (NTRS)

    Solomon, William C.

    1994-01-01

    Procedure for chemical analysis of specimens of silicone-based ablative thermal-insulation materials SLA-561 and MA25 involves acid digestion of specimens to prepare them for analysis by inductively-coupled-plasma/atomic-emission spectroscopy (ICP/AES). In comparison with atomic-absorption spectroscopy (AAS), ICP/AES is faster and more accurate than AAS. Results of analyses stored in data base, used to trace variations in concentrations of chemical elements in materials during long-term storage, and used in timely manner in investigations of failures. Acid-digestion portion of procedure applied to other thermal-insulation materials containing room-temperature-vulcanizing silicones and enables instrumental analysis of these materials.

  4. Single-walled carbon nanotubes synthesis: a direct comparison of laser ablation and carbon arc routes.

    PubMed

    Bystrzejewski, M; Rümmeli, M H; Lange, H; Huczko, A; Baranowski, P; Gemming, T; Pichler, T

    2008-11-01

    Carbon arc and chemical vapor deposition are at present the most efficient methods for mass production of single-walled carbon nanotubes. However, laser ablation is renowned for high quality nanotubes with narrow diameter distributions and hence is also of great interest. The aim of this work was to compare both the carbon arc and laser ablation techniques with respect to the quality--and relative yield of the produced SWCNTs. For this comparative study we used Fe as the catalyst, which is known not to be very active in laser ablation. However, we show this is not the case when H2 is included in the reaction. The reactions for both synthesis routes were carried out in a N2-H2 (95-5% vol.) atmosphere. The same homogenous carbon rods with different iron contents, between 1 and 5 at.% were used as the carbon feedstock and catalyst supply in both synthesis routes. Additionally, two types of carbon rods containing 1 at.% Fe with different graphitization degrees were also investigated. In the arc-discharge case, the low-graphitized electrode produced a web-like product rich in SWCNTs, while the high-graphitized carbon rods yielded soot containing carbon-encapsulated iron nanocrystallites, amorphous carbon nanoparticles, and surprisingly a small fraction of SWCNTs. With laser ablation synthesis, the Fe content and the reactor temperature significantly influenced the SWCNTs yield. Carbon arc plasma diagnostics were also performed. By using optical emission and Absorption spectroscopy the plasma temperature, C2 and CN radical content in the arc zone were determined. PMID:19198361

  5. Intumescent-ablators as improved thermal protection materials

    NASA Technical Reports Server (NTRS)

    Sawko, P. M.; Riccitiello, S. R.

    1977-01-01

    Nitroaromatic amine-based intumescent coatings were improved with regard to their thermal protection ability by adding endothermic decomposing fillers with endotherms at or near the exothermic reaction of the intumescent agent, since the effectiveness of the intumescent coatings without fillers is reduced by the exothermic behavior of the coatings during thermal activation. Fillers were dispersed directly in the base coating. Potassium fluoborate, ammonium fluoborate, zinc borate, and ammonium oxalate function as endothermic ablative materials at specific temperature regions, and also enhance the char formation during the intumescent process.

  6. Severe Chest Wall Toxicity From Cryoablation in the Setting of Prior Stereotactic Ablative Radiotherapy.

    PubMed

    Chaudhuri, Aadel A; Binkley, Michael S; Aggarwal, Sonya; Qian, Yushen; Carter, Justin N; Shah, Rajesh; Loo, Billy W

    2016-01-01

    We present the case of a 42-year-old woman with metastatic synovial sarcoma of parotid origin, treated definitively with chemoradiation, who subsequently developed oligometastatic disease limited to the lungs. She underwent multiple left and right lung wedge resections and left lower lobectomy, followed by right lower lobe stereotactic ablative radiotherapy (SABR), 54 Gy in three fractions to a right lower lobe lesion abutting the chest wall. Two years later, she was treated with cryoablation for a separate right upper lobe nodule abutting the chest wall. Two months later, she presented with acute shortness of breath, pleuritic chest pain, decreased peripheral blood O2 saturation, and productive cough. A computed tomography (CT) scan demonstrated severe chest wall necrosis in the area of recent cryoablation that, in retrospect, also received a significant radiation dose from her prior SABR. This case demonstrates that clinicians should exercise caution in using cryoablation when treating lung tumors abutting a previously irradiated chest wall. Note: Drs. Loo and Shah contributed equally as co-senior authors. PMID:27004154

  7. Severe Chest Wall Toxicity From Cryoablation in the Setting of Prior Stereotactic Ablative Radiotherapy

    PubMed Central

    Chaudhuri, Aadel A; Binkley, Michael S; Aggarwal, Sonya; Qian, Yushen; Carter, Justin N; Shah, Rajesh

    2016-01-01

    We present the case of a 42-year-old woman with metastatic synovial sarcoma of parotid origin, treated definitively with chemoradiation, who subsequently developed oligometastatic disease limited to the lungs. She underwent multiple left and right lung wedge resections and left lower lobectomy, followed by right lower lobe stereotactic ablative radiotherapy (SABR), 54 Gy in three fractions to a right lower lobe lesion abutting the chest wall. Two years later, she was treated with cryoablation for a separate right upper lobe nodule abutting the chest wall. Two months later, she presented with acute shortness of breath, pleuritic chest pain, decreased peripheral blood O2 saturation, and productive cough. A computed tomography (CT) scan demonstrated severe chest wall necrosis in the area of recent cryoablation that, in retrospect, also received a significant radiation dose from her prior SABR. This case demonstrates that clinicians should exercise caution in using cryoablation when treating lung tumors abutting a previously irradiated chest wall. Note: Drs. Loo and Shah contributed equally as co-senior authors. PMID:27004154

  8. Modeling of the Ablation of Fibrous Materials in the Knudsen Regime

    NASA Technical Reports Server (NTRS)

    Lachaud, J.; Mansour, N. N.

    2008-01-01

    During atmospheric entry of planetary probes, the thermal protection system (TPS) of the probe is exposed to high temperatures under low pressures. In these conditions, carbonous TPS materials undergo gasification in the Knudsen regime leading to mass loss and wall recession called ablation. This work aims to improve the understanding of materiaVenvironment interactions through a study of the coupling between carbon dioxide transport in the Knudsen regime, heterogeneous oxidation of carbon, and sutface recession. A 3D Monte-Carlo simulation tool is used for this study. The fibrous architecture of the materiils, consisting of high porosity random array of carbon fibers, is numerically reproduced 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 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 results enable extrapolation of laboratory experimental data to actual entry conditions.

  9. Carbon Nanotube-enhanced Carbon-phenolic Ablator Material

    NASA Technical Reports Server (NTRS)

    Nikolaev, P.; Stackpoole, M.; Fan, W.; Cruden, B.; Waid, M.; Maloney, P.; Arepalli, S.; Arnold, J.; Partridge, H.; Yowell, L.

    2006-01-01

    Phenolic impregnated carbon ablator (PICA) is a thermal protection system (TPS) material developed at NASA Ames Research Center in the mid-90 s for Discovery missions. It was used on the Stardust return capsule heat shield which successfully executed the highest speed Earth entry to date on January 15, 2006. PICA is a porous fibrous carbon insulation infiltrated with phenolic resin, and is an excellent ablator that is effective for heating rates up to 1000 W/sq cm. It is one of several candidate TPS materials for the next generation of crewed spacecraft for Lunar and Mars missions. We will describe an ongoing research effort at NASA to improve mechanical properties of the phenolic matrix with carbon nanotubes. The aim is two-fold: to increase overall TPS strength during reentry and to improve Micrometeoroid/Orbital Debris (MMOD) protection in space. The former requires at least a good dispersion of nanotubes in phenolic, while the latter also requires covalent bonding between them to couple and transfer impact energy effectively from matrix to nanotubes. We will discuss the required chemical functionalization of nanotubes, processing issues and test results.

  10. An assessment of the readiness of ablative materials for preflight application to the shuttle orbiter

    NASA Technical Reports Server (NTRS)

    Tompkins, S. S.; Brewer, W. D.; Clark, R. K.; Pittman, C. M.; Brinkley, K. L.

    1980-01-01

    The shuttle orbiter relies primarily on a reusable surface insulation (RSI) thermal protection system (TPS). The RSI is very efficient in its thermal performance; however, the RSI tile system has shown poor mechanical integrity. The state-of-the-art of the ablative TPS is reviewed, and an assessment made of the ablator's readiness for use on the shuttle orbiter. Unresolved technical issues with regard to the ablative TPS are identified. Short time, highly focused analytical and experimental programs were initiated to: (1) identify candidate ablation materials; (2) assess the data base for these materials; (3) evaluate the need and kind of waterproof coating; (4) calculate thermal and other stresses in an ablator tile; (5) identify an acceptable ablator/RSI tile joint filler; and (6) assess the sensitivity of the ablator to sequential heat pulses. Results from some of these programs are discussed.

  11. Pre-ignition laser ablation of nanocomposite energetic materials

    SciTech Connect

    Stacy, S. C.; Massad, R. A.; Pantoya, M. L.

    2013-06-07

    Laser ignition of energetic material composites was studied for initiation with heating rates from 9.5 Multiplication-Sign 10{sup 4} to 1.7 Multiplication-Sign 10{sup 7} K/s. This is a unique heating rate regime for laser ignition studies because most studies employ either continuous wave CO{sub 2} lasers to provide thermal ignition or pulsed Nd:YAG lasers to provide shock ignition. In this study, aluminum (Al) and molybdenum trioxide (MoO{sub 3}) nanoparticle powders were pressed into consolidated pellets and ignited using a Nd:YAG laser (1064 nm wavelength) with varied pulse energy. Results show reduced ignition delay times corresponding to laser powers at the ablation threshold for the sample. Heating rate and absorption coefficient were determined from an axisymmetric heat transfer model. The model estimates absorption coefficients from 0.1 to 0.15 for consolidated pellets of Al + MoO{sub 3} at 1064 nm wavelength. Ablation resulted from fracturing caused by a rapid increase in thermal stress and slowed ignition of the pellet.

  12. Pre-ignition laser ablation of nanocomposite energetic materials

    NASA Astrophysics Data System (ADS)

    Stacy, S. C.; Massad, R. A.; Pantoya, M. L.

    2013-06-01

    Laser ignition of energetic material composites was studied for initiation with heating rates from 9.5 × 104 to 1.7 × 107 K/s. This is a unique heating rate regime for laser ignition studies because most studies employ either continuous wave CO2 lasers to provide thermal ignition or pulsed Nd:YAG lasers to provide shock ignition. In this study, aluminum (Al) and molybdenum trioxide (MoO3) nanoparticle powders were pressed into consolidated pellets and ignited using a Nd:YAG laser (1064 nm wavelength) with varied pulse energy. Results show reduced ignition delay times corresponding to laser powers at the ablation threshold for the sample. Heating rate and absorption coefficient were determined from an axisymmetric heat transfer model. The model estimates absorption coefficients from 0.1 to 0.15 for consolidated pellets of Al + MoO3 at 1064 nm wavelength. Ablation resulted from fracturing caused by a rapid increase in thermal stress and slowed ignition of the pellet.

  13. Chemical models for simulating single-walled nanotube production in arc vaporization and laser ablation processes

    NASA Technical Reports Server (NTRS)

    Scott, Carl D.

    2004-01-01

    Chemical kinetic models for the nucleation and growth of clusters and single-walled carbon nanotube (SWNT) growth are developed for numerical simulations of the production of SWNTs. Two models that involve evaporation and condensation of carbon and metal catalysts, a full model involving all carbon clusters up to C80, and a reduced model are discussed. The full model is based on a fullerene model, but nickel and carbon/nickel cluster reactions are added to form SWNTs from soot and fullerenes. The full model has a large number of species--so large that to incorporate them into a flow field computation for simulating laser ablation and arc processes requires that they be simplified. The model is reduced by defining large clusters that represent many various sized clusters. Comparisons are given between these models for cases that may be applicable to arc and laser ablation production. Solutions to the system of chemical rate equations of these models for a ramped temperature profile show that production of various species, including SWNTs, agree to within about 50% for a fast ramp, and within 10% for a slower temperature decay time.

  14. Comparison of laser-ablation and hot-wall chemical vapour deposition techniques for nanowire fabrication

    NASA Astrophysics Data System (ADS)

    Stern, E.; Cheng, G.; Guthrie, S.; Turner-Evans, D.; Broomfield, E.; Lei, B.; Li, C.; Zhang, D.; Zhou, C.; Reed, M. A.

    2006-06-01

    A comparison of the transport properties of populations of single-crystal, In2O3 nanowires (NWs) grown by unassisted hot-wall chemical vapour deposition (CVD) versus NWs grown by laser-ablation-assisted chemical vapour deposition (LA-CVD) is presented. For nominally identical growth conditions across the two systems, NWs fabricated at 850 °C with laser-ablation had significantly higher average mobilities at the 99.9% confidence level, 53.3 ± 5.8 cm2 V-1 s-1 versus 10.2 ± 1.9 cm2 V-1 s-1. It is also observed that increasing growth temperature decreases mobility for LA-CVD NWs. Transmission electron microscopy studies of CVD-fabricated samples indicate the presence of an amorphous In2O3 region surrounding the single-crystal core. Further, low-temperature measurements verify the presence of ionized impurity scattering in low-mobility CVD-grown NWs.

  15. Spectroscopic studies of laser ablation plumes of artwork materials

    NASA Astrophysics Data System (ADS)

    Oujja, M.; Rebollar, E.; Castillejo, M.

    2003-04-01

    Studies on the plasma plume created during KrF laser (248 nm) ablation of dosimeter tempera samples in vacuum have been carried out to investigate the basic interactions of the laser with paint materials. Time resolved optical emission spectroscopy (OES) was used to measure the translational velocity of electronically excited transients in the plasma plume. Laser-induced fluorescence (LIF) studies using a probe dye laser, allowed to determine the velocities of non-emitting species. The propagation velocities of C 2 in the a 3π u and d 3π g electronic states and of excited atomic species are indicative of a high translational temperature. Differences between the velocities of organic and inorganic species and between emissions from the tempera systems and from the pigments as pellets allow to discuss the participation of photochemical mechanisms in the laser irradiation of the paint systems.

  16. Ablation article and method

    NASA Technical Reports Server (NTRS)

    Erickson, W. D.; Sullivan, E. M. (Inventor)

    1973-01-01

    An ablation article, such as a conical heat shield, having an ablating surface is provided with at least one discrete area of at least one seed material, such as aluminum. When subjected to ablation conditions, the seed material is ablated. Radiation emanating from the ablated seed material is detected to analyze ablation effects without disturbing the ablation surface. By providing different seed materials having different radiation characteristics, the ablating effects on various areas of the ablating surface can be analyzed under any prevailing ablation conditions. The ablating article can be provided with means for detecting the radiation characteristics of the ablated seed material to provide a self-contained analysis unit.

  17. Analysis of fabric materials cut using ultraviolet laser ablation

    NASA Astrophysics Data System (ADS)

    Tsai, Hsin-Yi; Yang, Chih-Chung; Hsiao, Wen-Tse; Huang, Kuo-Cheng; Andrew Yeh, J.

    2016-04-01

    Laser ablation technology has widely been applied in the clothing industry in recent years. However, the laser mechanism would affect the quality of fabric contours and its components. Hence, this study examined carbonization and oxidation conditions and contour variation in nonwoven, cotton, and composite leather fabrics cut by using an ultraviolet laser at a wavelength of 355 nm. Processing parameters such as laser power, pulse frequency, scanning speed, and number of pulses per spot were adjusted to investigate component variation of the materials and to determine suitable cutting parameters for the fabrics. The experimental results showed that the weights of the component changed substantially by pulse frequency but slightly by laser power, so pulse frequency of 100 kHz and laser power of 14 W were the approximate parameters for three fabrics for the smaller carbonization and a sufficient energy for rapidly cutting, which the pulse duration of laser system was fixed at 300 μs and laser irradiance was 0.98 J/mm2 simultaneously. In addition, the etiolate phenomenon of nonwoven was reduced, and the component weight of cotton and composite leather was closed to the value of knife-cut fabric as the scanning speed increased. The approximate scanning speed for nonwoven and composite leather was 200 mm/s, and one for cotton was 150 mm/s, respectively. The sharper and firmer edge is obtained by laser ablation mechanism in comparison with traditional knife cutting. Experimental results can serve as the reference for laser cutting in the clothing industry, for rapidly providing smoother patterns with lower carbonization and oxidation edge in the fashion industry.

  18. A study of the effect of selected material properties on the ablation performance of artificial graphite

    NASA Technical Reports Server (NTRS)

    Maahs, H. G.

    1972-01-01

    Eighteen material properties were measured on 45 different, commercially available, artificial graphites. Ablation performance of these same graphites were also measured in a Mach 2 airstream at a stagnation pressure of 5.6 atm. Correlations were developed, where possible, between pairs of the material properties. Multiple regression equations were then formulated relating ablation performance to the various material properties, thus identifying those material properties having the strongest effect on ablation performance. These regression equations reveal that ablation performance in the present test environment depends primarily on maximum grain size, density, ash content, thermal conductivity, and mean pore radius. For optimization of ablation performance, grain size should be small, ash content low, density and thermal conductivity high, and mean pore radius large.

  19. Remote Recession Sensing of Ablative Heat Shield Materials

    NASA Technical Reports Server (NTRS)

    Winter, Michael W.; Stackpoole, Margaret; Nawaz, Anuscheh; Gonzales, Gregory Lewis; Ho, Thanh

    2014-01-01

    Material recession and charring are two major processes determining the performance of ablative heat shield materials. Even in ground testing, the characterization of these two mechanisms relies on measurements of material thickness before and after testing, thus providing only information integrated over the test time. For recession measurements, optical methods such as imaging the sample surface during testing are under investigation but require high alignment and instrument effort, therefore being not established as a standard measurement method. For char depth measurements, the most common method so far consists in investigation of sectioned samples after testing or in the case of Stardust where core extractions were performed to determine char information. In flight, no reliable recession measurements are available, except total recession after recovering the heat shield on ground. Developments of mechanical recession sensors have been started but require substantial on board instrumentation adding mass and complexity. In this work, preliminary experiments to evaluate the feasibility of remote sensing of material recession and possibly char depth through optically observing the emission signatures of seeding materials in the post shock plasma is investigated. It is shown that this method can provide time resolved recession measurements without the necessity of accurate alignment procedures of the optical set-up and without any instrumentation on board of a spacecraft. Furthermore, recession data can be obtained without recovering flight hardware which would be a huge benefit for inexpensive heat shield material testing on board of small re-entry probes, e.g. on new micro-satellite re-entry probes as a possible future application of Cubesats or RBR

  20. Left lateral free wall pathway ablation complicated by plaque rupture and acute occlusion of the left anterior descending coronary artery.

    PubMed

    Yildiz, Bekir Serhat; Alihanoglu, Yusuf Izzettin; Kilic, Ismail Dogu; Evrengul, Harun

    2014-06-01

    Radiofrequency (RF) ablation of accessory bypass tracts associated with the Wolff-Parkinson-White (WPW) syndrome has become the treatment of choice for many arrhythmias. Complications are unusual and acute coronary artery occlusion is very rare. We here present a 38-year-old male patient with an acute occlusion of proximal left anterior descending (LAD) coronary artery after RF ablation of a left free wall accessory pathway. An interesting feature is the site of the coronary artery occlusion which is remote from the RF application site. The occlusion was successfully treated with the placement of an intracoronary stent. PMID:25029886

  1. Fundamentals of femtosecond laser ablation of dielectric materials

    SciTech Connect

    Byskov-Nielsen, J.; Le, D. Q. S.; Christensen, M. N.; Balling, P.; Christensen, B. H.

    2010-10-08

    The modeling of laser-excited dielectric materials requires a detailed description of the electronic excitation. Dielectric materials do not absorb visible light by traditional linear absorption, so the dynamical generation of conduction-band electrons strongly couples to the absorption. The generation of free electrons is initiated by strong-field excitation and followed by multiplication through impact ionization by energetic electrons heated by the laser. The present paper describes an approach to solving the coupled problem of electron excitation and one-dimensional light propagation. The electronic excitation is described in the so-called multiple-rate-equation model, and the light is absorbed by a combination of strong-field excitation and linear absorption by the excited electrons, which are assumed to behave as a free-electron gas described by a Drude model. The model is generic and based on a few key parameters: the wavelength and the pulse duration of the light, and the band gap of the dielectric medium. This allows parametric investigations of ablation phenomena.

  2. Laser-solid interaction and dynamics of laser-ablated materials

    SciTech Connect

    Chen, K.R.; Neboeuf, J.N.; Wood, R.F.; Geohegan, D.B.; Donato, J.M.; Liu, C.L.; Puretzky, A.A.

    1995-09-01

    An annealing model is extended to treat the vaporization process, and a hydrodynamic model describes the ablated material. We find that dynamic source and ionization effects accelerate the expansion front of the ablated plume with thermal vaporization temperature. The vaporization process and plume propagation in high background gas pressure are studied.

  3. Prediction of engine performance and wall erosion due to film cooling for the 'fast track' ablative thrust chamber

    NASA Technical Reports Server (NTRS)

    Trinh, Huu P.

    1994-01-01

    Efforts have been made at the Propulsion Laboratory (MSFC) to design and develop new liquid rocket engines for small-class launch vehicles. Emphasis of the efforts is to reduce the engine development time with the use of conventional designs while meeting engine reliability criteria. Consequently, the engine cost should be reduced. A demonstrative ablative thrust chamber, called 'fast-track', has been built. To support the design of the 'fast-track' thrust chamber, predictions of the wall temperature and ablation erosion rate of the 'fast-track' thrust chamber have been performed using the computational fluid dynamics program REFLEQS (Reactive Flow Equation Solver). The analysis is intended to assess the amount of fuel to be used for film cooling so that the erosion rate of the chamber ablation does not exceed its allowable limit. In addition, the thrust chamber performance loss due to an increase of the film cooling is examined.

  4. The thermal and mechanical properties of a low density elastomeric ablation material

    NASA Technical Reports Server (NTRS)

    Engelke, W. T.; Robertson, R. W.; Bush, A. L.; Pears, C. D.

    1973-01-01

    Thermal and mechanical properties data were obtained for a low density elastomeric resin based ablation material with phenolic-glass honeycomb reinforcement. Data were obtained for the material in the charred and uncharred state. Ablation material specimens were charred in a laboratory furnace at temperatures in the range from 600 K to 1700 K to obtain char specimens representative of the ablation char layer formed during reentry. These specimens were then used to obtain effective thermal conductivity, heat capacity, porosity, and permeability data at the char formation temperature. This provided a boxing of the data which enables the prediction of the transient response of the material during ablation. Limited comparisons were made between the furnace charred specimens and specimens which had been exposed to simulated reentry conditions.

  5. Femtosecond laser ablation of dielectric materials in the optical breakdown regime: Expansion of a transparent shell

    SciTech Connect

    Garcia-Lechuga, M.; Siegel, J. Hernandez-Rueda, J.; Solis, J.

    2014-09-15

    Phase transition pathways of matter upon ablation with ultrashort laser pulses have been considered to be understood long-since for metals and semiconductors. We provide evidence that also certain dielectrics follow the same pathway, even at high pulse energies triggering optical breakdown. Employing femtosecond microscopy, we observe a characteristic ring pattern within the ablating region that dynamically changes for increasing time delays between pump and probe pulse. These transient Newton rings are related to optical interference of the probe beam reflected at the front surface of the ablating layer with the reflection at the interface of the non-ablating substrate. Analysis of the ring structure shows that the ablation mechanism is initiated by a rarefaction wave leading within a few tens of picoseconds to the formation of a transparent thin shell of reduced density and refractive index, featuring optically sharp interfaces. The shell expands and eventually detaches from the solid material at delays of the order of 100 ps.

  6. Research and application of surface heat treatment for multipulse laser ablation of materials

    NASA Astrophysics Data System (ADS)

    Cai, Song; Chen, Genyu; Zhou, Cong

    2015-11-01

    This study analysed a laser ablation platform and built heat transfer equations for multipulse laser ablation of materials. The equations include three parts: laser emission after the material melt and gasification; end of laser emission after the material melts and there is the presence of a super-hot layer and solid-phase heat transfer changes during material ablation. For each of the three parts, the effects of evaporation, plasma shielding and energy accumulation under the pulse interval were considered. The equations are reasonable, and all the required parameters are only related to the laser parameters and material properties, allowing the model to have a certain versatility and practicability. The model was applied for numerical simulation of the heat transfer characteristics in the multipulse laser ablation of bronze and diamond. Next, experiments were conducted to analyse the topography of a bronze-bonded diamond grinding wheel after multipulse laser ablation. The theoretical analysis and experimental results showed that multipulse laser can merge the truing and dressing on a bronze-bonded diamond grinding wheel. This study provides theoretical guidance for optimising the process parameters in the laser ablation of a bronze-bonded diamond grinding wheel. A comparative analysis showed that the numerical solution to the model is in good agreement with the experimental data, thus verifying the correctness and feasibility of the heat transfer model.

  7. Endometrial ablation

    MedlinePlus

    Hysteroscopy-endometrial ablation; Laser thermal ablation; Endometrial ablation-radiofrequency; Endometrial ablation-thermal balloon ablation; Rollerball ablation; Hydrothermal ablation; Novasure ablation

  8. A parametric study of single-wall carbon nanotube growth by laser ablation

    NASA Technical Reports Server (NTRS)

    Arepalli, Sivaram; Holmes, William A.; Nikolaev, Pavel; Hadjiev, Victor G.; Scott, Carl D.

    2004-01-01

    Results of a parametric study of carbon nanotube production by the double-pulse laser oven process are presented. The effect of various operating parameters on the production of single-wall carbon nanotubes (SWCNTs) is estimated by characterizing the nanotube material using analytical techniques, including scanning electron microscopy, transmission electron microscopy, thermo gravimetric analysis and Raman spectroscopy. The study included changing the sequence of the laser pulses, laser energy, pulse separation, type of buffer gas used, operating pressure, flow rate, inner tube diameter, as well as its material, and oven temperature. It was found that the material quality and quantity improve with deviation from normal operation parameters such as laser energy density higher than 1.5 J/cm2, pressure lower than 67 kPa, and flow rates higher than 100 sccm. Use of helium produced mainly small diameter tubes and a lower yield. The diameter of SWCNTs decreases with decreasing oven temperature and lower flow rates.

  9. Comparative study of the ablation of materials by femtosecond and pico- or nanosecond laser pulses

    SciTech Connect

    Kononenko, Taras V; Konov, Vitalii I; Garnov, Sergei V; Danielius, R; Piskarskas, A; Tamosauskas, G; Dausinger, F

    1999-08-31

    A series of studies was carried out on the ablation of steel, Si{sub 3}N{sub 4} ceramic, and diamond in air by femtosecond (200 and 900 fs) pulses of different wavelengths (532 and 266 nm) and in a wide energy density range (1 - 10{sup 3} J cm{sup -2}). The ablation rates were measured for different geometries of the irradiation surface [a shallow crater and a channel with a high (up to 10) aspect ratio]. The ablation rates (in a shallow crater) and the morphologies of the irradiated surface were compared for femtosecond and longer (220 ps, 7 ns) pulses. The role of the laser-generated plasma in the ablation of materials by subpicosecond pulses as well as the prospects for the practical application of ultrashort laser pulses in the processing of materials are analysed. (interaction of laser radiation with matter. laser plasma)

  10. Gas dynamic and time resolved imaging studies of single-wall carbon nanotubes growth in the laser ablation process

    NASA Astrophysics Data System (ADS)

    Sen, Rahul; Suzuki, S.; Kataura, H.; Achiba, Y.

    2001-10-01

    Single-wall carbon nanotubes (SWNTs) were synthesized by laser ablation of Ni-Co-graphite composite targets at 1200 °C under flowing argon. The effects of the temperature gradient near the target and the gas flow rate on the diameter distribution of SWNTs were studied in order to understand their growth dynamics. The diameter distribution of the SWNTs, analyzed by Raman spectroscopy, was dependent on the gas flow rate when there was a temperature gradient around the target. Time resolved scattering images from the ablated species at different flow rates indicated that velocities of backward moving species increased with increasing flow rate. These findings are used to estimate the time required for nucleation and the growth of SWNTs.

  11. Laser ablation of electronic materials including the effects of energy coupling and plasma interactions

    SciTech Connect

    Zeng, Xianzhong

    2004-12-10

    Many laser ablation applications such as laser drilling and micromachining generate cavity structures. The study of laser ablation inside a cavity is of both fundamental and practical significance. In this dissertation, cavities with different aspect ratios (depth/diameter) were fabricated in fused silica by laser micromachining. Pulsed laser ablation in the cavities was studied and compared with laser ablation on a flat surface. The formation of laser-induced plasmas in the cavities and the effects of the cavities on the ablation processes were investigated. The temperatures and electron number densities of the resulting laser-induced plasmas in the cavities were determined from spectroscopic measurements. Reflection and confinement effects by the cavity walls and plasma shielding were discussed to explain the increased temperature and electron number density with respect to increasing cavity aspect ratio. The temporal variations of the plasma temperature and electron number density inside the cavity decreased more rapidly than outside the cavity. The effect of laser energy on formation of a plasma inside a cavity was also investigated. Propagation of the shock wave generated during pulsed laser ablation in cavities was measured using laser shadowgraph imaging and compared with laser ablation on a flat surface. It is found that outside the cavity, after about 30 ns the radius of the expanding shock wave was proportional to t2/5, which corresponds to a spherical blast wave. The calculated pressures and temperatures of the shocked air outside of the cavities were higher than those obtained on the flat surface. Lasers with femtosecond pulse duration are receiving much attention for direct fabrication of microstructures due to their capabilities of high-precision ablation with minimal damage to the sample. We have also performed experimental studies of pulsed femtosecond laser ablation on the flat surface of silicon samples and compared results with pulsed nanosecond

  12. Estimation of surface heat flux for ablation and charring of thermal protection material

    NASA Astrophysics Data System (ADS)

    Qian, Wei-qi; He, Kai-feng; Zhou, Yu

    2016-07-01

    Ablation of the thermal protection material of the reentry hypersonic flight vehicle is a complex physical and chemical process. To estimate the surface heat flux from internal temperature measurement is much more complex than the conventional inverse heat conduction problem case. In the paper, by utilizing a two-layer pyrogeneration-plane ablation model to model the ablation and charring of the material, modifying the finite control volume method to suit for the numerical simulation of the heat conduction equation with variable-geometry, the CGM along with the associated adjoint problem is developed to estimate the surface heat flux. This estimation method is verified with a numerical example at first, the results show that the estimation method is feasible and robust. The larger is the measurement noise, the greater is the deviation of the estimated result from the exact value, and the measurement noise of ablated surface position has a significant and more direct influence on the estimated result of surface heat flux. Furthermore, the estimation method is used to analyze the experimental data of ablation of blunt Carbon-phenolic material Narmco4028 in an arc-heater. It is shown that the estimated surface heat flux agrees with the heating power value of the arc-heater, and the estimation method is basically effective and potential to treat the engineering heat conduction problem with ablation.

  13. Picosecond laser ablation of poly-L-lactide: Effect of crystallinity on the material response

    SciTech Connect

    Ortiz, Rocio; Quintana, Iban; Etxarri, Jon; Lejardi, Ainhoa; Sarasua, Jose-Ramon

    2011-11-01

    The picosecond laser ablation of poly-L-lactide (PLLA) as a function of laser fluence and degree of crystallinity was examined. The ablation parameters and the surface modifications were analyzed under various irradiation conditions using laser wavelengths ranging from the ultraviolet through the visible. When processing the amorphous PLLA, both energy threshold and topography varied considerably depending on laser wavelength. Laser irradiation showed a reduction in the energy ablation threshold as the degree of crystallinity increased, probably related to photomechanical effects involved in laser ablation with ultra-short pulses and the lower stress accommodation behavior of semicrystalline polymers. In particular, cooperative chain motions are impeded by the higher degree of crystallinity, showing fragile mechanical behavior and lower energy dissipation. The experimental results on ablation rate versus laser energy showed that UV laser ablation on semicrystalline PLLA was more efficient than the visible ablation, i.e., it exhibits higher etch rates over a wide range of pulse energy conditions. These results were interpreted in terms of photo-thermal and photo-chemical response of polymers as a function of material micro-structure and incident laser wavelength. High quality micro-grooves were produced in amorphous PLLA, reveling the potential of ultra-fast laser processing technique in the field of micro-structuring biocompatible and biodegradable polymers for biomedical applications.

  14. Space Vehicle Heat Shield Having Edgewise Strips of Ablative Material

    NASA Technical Reports Server (NTRS)

    Blosser, Max L. (Inventor); Poteet, Carl C. (Inventor); Bouslog, Stan A. (Inventor)

    2015-01-01

    A heat shield for a space vehicle comprises a plurality of phenolic impregnated carbon ablator (PICA) blocks secured to a surface of the space vehicle and arranged in a pattern with gaps therebetween. The heat shield further comprises a plurality of PICA strips disposed in the gaps between the PICA blocks. The PICA strips are mounted edgewise, such that the structural orientation of the PICA strips is substantially perpendicular to the structural orientation of the PICA blocks.

  15. Material properties of lithium fluoride for predicting XUV laser ablation rate and threshold fluence

    NASA Astrophysics Data System (ADS)

    Blejchař, Tomáś; Nevrlý, Václav; Vašinek, Michal; Dostál, Michal; Pečínka, Lukáś; Dlabka, Jakub; Stachoň, Martin; Juha, Libor; Bitala, Petr; Zelinger, Zdeněk.; Pira, Peter; Wild, Jan

    2015-05-01

    This paper deals with prediction of extreme ultraviolet (XUV) laser ablation of lithium fluoride at nanosecond timescales. Material properties of lithium fluoride were determined based on bibliographic survey. These data are necessary for theoretical estimation of surface removal rate in relevance to XUV laser desorption/ablation process. Parameters of XUV radiation pulses generated by the Prague capillary-discharge laser (CDL) desktop system were assumed in this context. Prediction of ablation curve and threshold laser fluence for lithium fluoride was performed employing XUV-ABLATOR code. Quasi-random sampling approach was used for evaluating its predictive capabilities in the means of variance and stability of model outputs in expected range of uncertainties. These results were compared to experimental data observed previously.

  16. Ablation of Metals for Materials Processing via a Channelspark Electron Beam

    NASA Astrophysics Data System (ADS)

    Kovaleski, S. D.; Gilgenbach, R. M.; Rintamaki, J. I.; Ang, L. K.; Spindler, H. L.; Cohen, W. E.; Lau, Y. Y.; Lash, J. S.

    1996-11-01

    Channelspark driven ablation experiments have been designed to characterize ablated species of materials suitable for thin film deposition. The channelspark is a pseudospark device, developed by KFK footnote G. Muller, C. Schultheiss, Proc. of Beams, 2, 833(1994), capable of producing high current, low energy electron beams. The source operates with a 15-20kV accelerating potential and measured e-beam source current less than 2000A. Beam transport through the 5 to 20 mTorr argon background gas has been investigated. Al, Fe, and Ti ablation is being studied through spectroscopy and beam current techniques. Electron beam induced target damage is being compared to laser beam damaged targets. Electron transport and energy deposition in metals are being simulated in the ITS-TIGER code (Sandia Report No. SAND 91-1634) developed at Sandia National Laboratory. The thermodynamics of electron beam ablation of metals is compared to lasers.

  17. Off-Hugoniot characterization of alternative inertial confinement fusion ablator materials.

    NASA Astrophysics Data System (ADS)

    Moore, Alastair S.; Prisbrey, Shon; Baker, Kevin L.; Celliers, Peter M.; Fry, Jonathan; Dittrich, Thomas R.; Wu, Kuang-Jen J.; Kervin, Margaret L.; Schoff, Michael E.; Farrell, Mike; Nikroo, Abbas; Hurricane, Omar A.

    2016-05-01

    The ablation material used during the National Ignition Campaign, a glow- discharge polymer (GDP), does not couple as efficiently as simulations indicated to the multiple- shock inducing radiation drive environment created by laser power profile [1]. We investigate the performance of two other ablators, boron carbide (B4C) and high-density carbon (HDC) and compare with GDP under the same hohlraum conditions. Ablation performance is determined through measurement of the shock speed produced in planar samples of the ablator subjected to the identical multiple-shock inducing radiation drive environments that are similar to a generic three-shock ignition drive. Simulations are in better agreement with the off-Hugoniot performance of B4C than either HDC or GDP.

  18. Replacement of Ablators with Phase-Change Material for Thermal Protection of STS Elements

    NASA Technical Reports Server (NTRS)

    Kaul, Raj K.; Stuckey, Irvin; Munafo, Paul M. (Technical Monitor)

    2002-01-01

    As part of the research and development program to develop new Thermal Protection System (TPS) materials for aerospace applications at NASA's Marshall Space Flight Center (MSFC), an experimental study was conducted on a new concept for a non-ablative TPS material. Potential loss of TPS material and ablation by-products from the External Tank (ET) or Solid Rocket Booster (SRB) during Shuttle flight with the related Orbiter tile damage necessitates development of a non-ablative thermal protection system. The new Thermal Management Coating (TMC) consists of phase-change material encapsulated in micro spheres and a two-part resin system to adhere the coating to the structure material. The TMC uses a phase-change material to dissipate the heat produced during supersonic flight rather than an ablative material. This new material absorbs energy as it goes through a phase change during the heating portion of the flight profile and then the energy is slowly released as the phase-change material cools and returns to its solid state inside the micro spheres. The coating was subjected to different test conditions simulating design flight environments at the NASA/MSFC Improved Hot Gas Facility (IHGF) to study its performance.

  19. Preliminary Evaluation of Techniques to Fabricate Beryllium, Polyimide, and Ge-doped CH/CD Ablator Materials

    SciTech Connect

    Cook, B; Letts, S; Nikroo, A; Nobile, A; McElfresh, M; Cooley, J; Alexander, D

    2004-11-08

    This report including appendices provides information to complete this deliverable. It summarizes the important features of each ablator material, with particular focus to its usefulness for ignition capsules. More detailed discussions of each ablator type are in the Appendix. Included at the end of each separate discussion in the Appendix is a list of all published work with an ICF focus on that ablator type. This report is organized into Be based and polymer (C) based ablators. We summarize status, outstanding issues, and how we plan to address them. Details are in the Appendix. For Be there are two fabrication routes, one by machining bulk pieces into hemi-shells which are then bonded together, and the other by sputtering Be with Cu dopant onto spherical plastic mandrels to build up a wall. This method allows for radial variation in the Cu dopant concentration, while the machining approach is best suited to a uniform doping level. For plastic, we have already made a down select, eliminating polyimide because its performance as an ablator has been seen to be significantly different from that predicted by simulations. The other polymer, GDP (glow discharge polymer or sometimes called plasma polymer) comes in both a normal (hydrogenated) and deuterated form. There are differences between them (besides the H or D) and these will be detailed. The choice between them will be determined in part by cryogenic measurement of the IR absorption spectrum of DT scheduled to occur in the next few months. An initial list of specifications for ignition targets exists. However these specifications are continuing to evolve. This is due to evolving plans for NIF's deliverable energy and to more refined design simulations. Many requirements are not well specified due to lack of knowledge of the effect on the implosion. These requirements include: grain size and texture, fill hole size, fill tube size, bond joint thickness, allowable porosity (size and number), diameter and wall

  20. Low electron temperature in ablating materials formed by picosecond soft x-ray laser pulses

    NASA Astrophysics Data System (ADS)

    Ishino, Masahiko; Hasegawa, Noboru; Nishikino, Masaharu; Pikuz, Tatiana; Skobelev, Igor; Faenov, Anatoly; Inogamov, Nail; Kawachi, Tetsuya; Yamagiwa, Mitsuru

    2015-09-01

    To study the ablation process induced by the soft x-ray laser pulse, we investigated the electron temperature of the ablating material. Focused soft x-ray laser pulses having a wavelength of 13.9 nm and duration of 7 ps were irradiated onto the LiF, Al, and Cu surfaces, and we observed the optical emission from the surfaces by use of an optical camera. On sample surfaces, we could confirm damage structures, but no emission signal in the visible spectral range during ablation could be observed. Then, we estimated the electron temperature in the ablating matter. To consider the radiation from a heated layer, we supposed a black-body radiator as an object. The calculation result was that the electron temperature was estimated to be lower than 1 eV and the process duration was shorter than 1000 ps. The theoretical model calculation suggests the spallative ablation for the interaction between the soft x-ray laser and materials. The driving force for the spallation is an increasing pressure appearing in the heated layer, and the change of the surface is considered to be due to a splash of a molten layer. The model calculation predicts that the soft x-ray laser with the fluence around the ablation threshold can create an electron temperature around 1 eV in a material. The experimental result is in good accordance with the theoretical prediction. Our investigation implies that the spallative ablation occurs in the low electron temperature region of a non-equilibrium state of warm dense matter.

  1. Analytical procedure for characterization of medieval wall-paintings by X-ray fluorescence spectrometry, laser ablation inductively coupled plasma mass spectrometry and Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Syta, Olga; Rozum, Karol; Choińska, Marta; Zielińska, Dobrochna; Żukowska, Grażyna Zofia; Kijowska, Agnieszka; Wagner, Barbara

    2014-11-01

    Analytical procedure for the comprehensive chemical characterization of samples from medieval Nubian wall-paintings by means of portable X-ray fluorescence (pXRF), laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) and Raman spectroscopy (RS) was proposed in this work. The procedure was used for elemental and molecular investigations of samples from archeological excavations in Nubia (modern southern Egypt and northern Sudan). Numerous remains of churches with painted decorations dated back to the 7th-14th century were excavated in the region of medieval kingdoms of Nubia but many aspects of this art and its technology are still unknown. Samples from the selected archeological sites (Faras, Old Dongola and Banganarti) were analyzed in the form of transfers (n = 26), small fragments collected during the excavations (n = 35) and cross sections (n = 15). XRF was used to collect data about elemental composition, LA-ICPMS allowed mapping of selected elements, while RS was used to get the molecular information about the samples. The preliminary results indicated the usefulness of the proposed analytical procedure for distinguishing the substances, from both the surface and sub-surface domains of the wall-paintings. The possibility to identify raw materials from the wall-paintings will be used in the further systematic, archeometric studies devoted to the detailed comparison of various historic Nubian centers.

  2. High spatial resolution mapping of deposition layers on plasma facing materials by laser ablation microprobe time-of-flight mass spectroscopy

    SciTech Connect

    Xiao, Qingmei; Li, Cong; Hai, Ran; Zhang, Lei; Feng, Chunlei; Ding, Hongbin; Zhou, Yan; Yan, Longwen; Duan, Xuru

    2014-05-15

    A laser ablation microprobe time-of-flight mass spectroscopy (LAM-TOF-MS) system with high spatial resolution, ∼20 nm in depth and ∼500 μm or better on the surface, is developed to analyze the composition distributions of deposition layers on the first wall materials or first mirrors in tokamak. The LAM-TOF-MS system consists of a laser ablation microprobe combined with a TOF-MS and a data acquisition system based on a LabVIEW program software package. Laser induced ablation combined with TOF-MS is an attractive method to analyze the depth profile of deposited layer with successive laser shots, therefore, it can provide information for composition reconstruction of the plasma wall interaction process. In this work, we demonstrate that the LAM-TOF-MS system is capable of characterizing the depth profile as well as mapping 2D composition of deposited film on the molybdenum first mirror retrieved from HL-2A tokamak, with particular emphasis on some of the species produced during the ablation process. The presented LAM-TOF-MS system provides not only the 3D characterization of deposition but also the removal efficiency of species of concern.

  3. First-wall/blanket materials selection for STARFIRE tokamak reactor

    SciTech Connect

    Smith, D.L.; Mattas, R.F.; Clemmer, R.G.; Davis, J.W.

    1980-01-01

    The development of the reference STARFIRE first-wall/blanket design involved numerous trade-offs in the materials selection process for the breeding material, coolant structure, neutron multiplier, and reflector. The major parameters and properties that impact materials selection and design criteria are reviewed.

  4. Adding crumb rubber into exterior wall materials.

    PubMed

    Zhu, Han; Thong-On, Norasit; Zhang, Xiong

    2002-10-01

    In Arizona US, most houses are built with walls covered by stuccos/coatings/mortars. This paper presents an explorative investigation of adding crumb rubber into stuccos/coatings/mortars. A series of experiments are conducted to examine the thermal and mechanical performance of the crumb rubber mixes. The results show that, the mixes with crumb rubber do exhibit more desirable performances like being high in crack-resistance and thermal insulation, and low in thermal expansion/contraction. The drawback for the crumb rubber mixes is the reduction in compressive strength, but which can be compensated by other means. As a site experiment, an area of 100 square-feet of crumb rubber coatings for two mix designs is sprayed on a tire-adobe wall. After being sprayed more than 14 months, the coatings apparently are in good condition. Significance of this study is that this practice, if accepted, will yield improved products that consume large quantities of crumb rubber. PMID:12498477

  5. Contribution of material's surface layer on charge state distribution in laser ablation plasma.

    PubMed

    Kumaki, Masafumi; Steski, Dannie; Ikeda, Shunsuke; Kanesue, Takeshi; Okamura, Masahiro; Washio, Masakazu

    2016-02-01

    To generate laser ablation plasma, a pulse laser is focused onto a solid target making a crater on the surface. However, not all the evaporated material is efficiently converted to hot plasma. Some portion of the evaporated material could be turned to low temperature plasma or just vapor. To investigate the mechanism, we prepared an aluminum target coated by thin carbon layers. Then, we measured the ablation plasma properties with different carbon thicknesses on the aluminum plate. The results showed that C(6+) ions were generated only from the surface layer. The deep layers (over 250 nm from the surface) did not provide high charge state ions. On the other hand, low charge state ions were mainly produced by the deeper layers of the target. Atoms deeper than 1000 nm did not contribute to the ablation plasma formation. PMID:26931982

  6. Comparison of Ablation Predictions for Carbonaceous Materials Using CEA and JANAF-Based Species Thermodynamics

    NASA Technical Reports Server (NTRS)

    Milos, Frank S.

    2011-01-01

    In most previous work at NASA Ames Research Center, ablation predictions for carbonaceous materials were obtained using a species thermodynamics database developed by Aerotherm Corporation. This database is derived mostly from the JANAF thermochemical tables. However, the CEA thermodynamics database, also used by NASA, is considered more up to date. In this work, the FIAT code was modified to use CEA-based curve fits for species thermodynamics, then analyses using both the JANAF and CEA thermodynamics were performed for carbon and carbon phenolic materials over a range of test conditions. The ablation predictions are comparable at lower heat fluxes where the dominant mechanism is carbon oxidation. However, the predictions begin to diverge in the sublimation regime, with the CEA model predicting lower recession. The disagreement is more significant for carbon phenolic than for carbon, and this difference is attributed to hydrocarbon species that may contribute to the ablation rate.

  7. Ablation of carbonaceous materials in a hydrogen-helium arc-jet flow

    NASA Technical Reports Server (NTRS)

    Park, C.; Lundell, J. H.; Green, M. J.; Winovich, W.; Covington, M. A.

    1983-01-01

    The stagnation-point ablation rates of a graphite, a carbon-carbon composite, and four carbon-phenolic materials are measured in an arc-jet wind tunnel with a 50% hydrogen-50% helium mixture as the test gas. Flow environments are determined through measurements of static and impact pressures, heat-transfer rates to a calorimeter, and radiation spectra, and through numerical calculation of the flow through the wind tunnel, spectra, and heat-transfer rates. The environments so determined are: impact pressure approx. 3 atm, Mach number approx. 2.1, convective heat-transfer rate approx. 14 kw/sq cm, and radiative heat-transfer rate approx. 7 kw/sq cm in the absence of ablation. Ablation rates are determined from the measured rates of mass loss and recession of the ablation specimens. Compared with the predicted ablation rates obtained by running RASLE and CMA codes, the measured rates are higher by about 15% for all tested materials.

  8. Liquid-assisted laser ablation of advanced ceramics and glass-ceramic materials

    NASA Astrophysics Data System (ADS)

    Garcia-Giron, A.; Sola, D.; Peña, J. I.

    2016-02-01

    In this work, results obtained by laser ablation of advanced ceramics and glass-ceramic materials assisted by liquids are reported. A Q-switched Nd:YAG laser at its fundamental wavelength of 1064 nm with pulse-width in the nanosecond range was used to machine the materials, which were immersed in water and ethylene glycol. Variation in geometrical parameters, morphology, and ablation yields were studied by using the same laser working conditions. It was observed that machined depth and removed volume depended on the thermal, optical, and mechanical features of the processed materials as well as on the properties of the surrounding medium in which the laser processing was carried out. Variation in ablation yields was studied in function of the liquid used to assist the laser process and related to refractive index and viscosity. Material features and working conditions were also related to the obtained results in order to correlate ablation parameters with respect to the hardness of the processed materials.

  9. Characterization of Candidate Materials for Remote Recession Measurements of Ablative Heat Shield Materials

    NASA Technical Reports Server (NTRS)

    Butler, Bradley D.; Winter, Michael; Panerai, Francesco; Martin, Alexandre; Bailey, Sean C. C.; Stackpoole, Margaret; Danehy, Paul M.; Splinter, Scott

    2016-01-01

    A method of remotely measuring surface recession of a material sample in a plasma flow through emission spectroscopy of the post shock layer was characterized through experiments in the NASA Langley HYMETS arc jet facility. Different methods for delivering the seed products into the Phenolic Impregnated Carbon Ablator (PICA) material samples were investigated. Three samples were produced by seeding the PICA material with combinations of Al, Si, HfO2, VB2, Al2O3, SiO2, TiC, HfC, NaCl, and MgCl2 through infusing seed materials into a core of PICA, or through encapsulating seed material in an epoxy disk, mechanically bonding the disk to a PICA sample. The PICA samples seeded with the candidate tracers were then tested at surface temperatures near 2400 K under low pressure air plasma. The emission of Al, Ti, V, Na, and Mg in the post-shock layer was observed in the UV with a high resolution imaging spectrometer viewing the whole stagnation line from the side, and from UV to NIR with a fiber-coupled miniaturized spectrometer observing the sample surface in the wavelength range from 200 nm to 1,100 nm from the front through a collimator. Al, Na, and Mg were found to be emitting in the post-shock spectra even before the recession reached the seeding depth - therefore possibly characterizing the pyrolysis process rather than the recession itself. The appearance of Ti and V emission in the spectra was well correlated with the actual recession which was monitored through a video of the front surface of the sample. The applicability of a seed material as an indicator for recession appears to be related to the melting temperature of the seed material. Future parametric studies will be carried out in low power plasma facilities at the University of Kentucky.

  10. Thermal protection for hypervelocity flight in earth's atmosphere by use of radiation backscattering ablating materials

    NASA Technical Reports Server (NTRS)

    Howe, John T.; Yang, Lily

    1991-01-01

    A heat-shield-material response code predicting the transient performance of a material subject to the combined convective and radiative heating associated with the hypervelocity flight is developed. The code is dynamically interactive to the heating from a transient flow field, including the effects of material ablation on flow field behavior. It accomodates finite time variable material thickness, internal material phase change, wavelength-dependent radiative properties, and temperature-dependent thermal, physical, and radiative properties. The equations of radiative transfer are solved with the material and are coupled to the transfer energy equation containing the radiative flux divergence in addition to the usual energy terms.

  11. Systematic Examination of Stardust Bulbous Track Wall Materials

    NASA Technical Reports Server (NTRS)

    Nakamura-Messenger, K.; Clemett, S. J.; Nguyen, A. N.; Berger, E. L.; Keller, L. P.; Messenger, S.

    2013-01-01

    Analyses of Comet Wild-2 samples returned by NASA's Stardust spacecraft have focused primarily on terminal particles (TPs) or well-preserved fine-grained materials along the track walls [1,2]. However much of the collected material was melted and mixed intimately with the aerogel by the hypervelocity impact [3,4]. We are performing systematic examinations of entire Stardust tracks to establish the mineralogy and origins of all comet Wild 2 components [7,8]. This report focuses on coordinated analyses of indigenous crystalline and amorphous/melt cometary materials along the aerogel track walls, their interaction with aerogel during collection and comparisons with their TPs.

  12. Production of nanodispersed materials and thin films by laser ablation techniques in liquid and in vacuum

    NASA Astrophysics Data System (ADS)

    Tveryanovich, Yu S.; Manshina, A. A.; Tverjanovich, A. S.

    2012-12-01

    The methods of laser ablation of chemical compounds in a liquid medium and in vacuum used for the production of highly dispersed materials and films, respectively, are considered. Features and advantages of these methods are noted and the potential of their application for the design of novel materials is discussed. Examples of application of these methods in scientific research are given. The bibliography includes 177 references.

  13. Micromanufacturing Of Hard To Machine Materials By Physical And Chemical Ablation Processes

    SciTech Connect

    Schubert, A.; Edelmann, J.; Gross, S.; Meichsner, G.; Wolf, N.; Schneider, J.; Zeidler, H.; Hackert, M.

    2011-01-17

    Miniaturization leads to high requirements to the applied manufacturing processes especially in respect to the used hard to machine materials and the aims of structure size and geometrical accuracy. Traditional manufacturing processes reach their limits here. One alternative for these provide thermal and chemical ablation processes. These processes are applied for the production of different microstructures in different materials like hardened steel, carbides and ceramics especially for medical engineering and tribological applications.

  14. Material options for a commercial fusion reactor first wall

    SciTech Connect

    Dabiri, A.E.

    1986-05-01

    A study has been conducted to evaluate the potential of various materials for use as first walls in high-power-density commercial fusion reactors. Operating limits for each material were obtained based on a number of criteria, including maximum allowable structural temperatures, critical heat flux, ultimate tensile strength, and design-allowable stress. The results with water as a coolant indicate that a modified alloy similar to HT-9 may be a suitable candidate for low- and medium-power-density reactor first walls with neutron loads of up to 6 MW/m/sup 2/. A vanadium or copper alloy must be used for high-power-density reactors. The neutron wall load limit for vanadium alloys is about 14 MW/sup 2/, provided a suitable coating material is chosen. The extremely limited data base for radiation effects hinders any quantitative assessment of the limits for copper alloys.

  15. Deuterium plasma-material wall interactions

    NASA Astrophysics Data System (ADS)

    Tien, J. K.; Gross, R. A.

    1981-10-01

    During the final year of this program we completed our study of plasma interactions with material surfaces. Analysis of unipolar arc damage on the microstructure of Ti-6Al-4V was the final part of the study of plasma-metal interactions. Unipolar arcing was found to be the most severe damage mechanism for this alloy and the degree of damage was very sensitive to the metal microstructure. ATJ-S graphite specimens were exposed to hot deuterium plasma and were examined for surface damage. The residual gas in the plasma device was studied using a monopole gas analyzer so as to determine the type and quantity of hydrocarbon species produced by the plasma-graphite interaction.

  16. Momentum and velocity of the ablated material in laser machining of carbon fiber preforms

    NASA Astrophysics Data System (ADS)

    Mucha, P.; Speker, N.; Weber, R.; Graf, T.

    2013-11-01

    The automation in fabrication of CFRP (carbon-fiber-reinforced plastics) parts demands efficient and low-cost machining technologies. In conventional cutting technologies, tool-wear and low process speeds are some of the reasons for high costs. Thus, the use of lasers is an attractive option for cutting CF-preforms. A typical effect degrading the quality in laser cutting CF-preform is a bulged cutting edge. This effect is assumed to be caused by interaction of the fibers with the ablated material, which leaves the kerf at high velocity. Hence, a method for measuring the momentum and the velocity of the vapor is presented in this article. To measure the momentum of the ablated material, the CF-preform is mounted on a precision scale while cutting it with a laser. The direction of the momentum was determined by measuring the momentum parallel and orthogonal to the CF-preform surface. A change of the direction of the momentum with different cutting-speeds is assessed at constant laser-power. Averaged velocities of the ablation products of up to 300 m/s were determined by measuring the ablated mass and the momentum.

  17. Heat generation caused by ablation of dental restorative materials with an ultra short pulse laser (USPL) system

    NASA Astrophysics Data System (ADS)

    Braun, Andreas; Wehry, Richard; Brede, Olivier; Frentzen, Matthias; Schelle, Florian

    2011-03-01

    The aim of this study was to assess heat generation in dental restoration materials following laser ablation using an Ultra Short Pulse Laser (USPL) system. Specimens of phosphate cement (PC), ceramic (CE) and composite (C) were used. Ablation was performed with an Nd:YVO4 laser at 1064 nm and a pulse length of 8 ps. Heat generation during laser ablation depended on the thickness of the restoration material. A time delay for temperature increase was observed in the PC and C group. Employing the USPL system for removal of restorative materials, heat generation has to be considered.

  18. The thermal and mechanical properties of a low-density glass-fiber-reinforced elastomeric ablation material

    NASA Technical Reports Server (NTRS)

    Engelke, W. T.; Robertson, R. W.; Bush, A. L.; Pears, C. D.

    1974-01-01

    An evaluation of the thermal and mechanical properties was performed on a molded low-density elastomeric ablation material designated as Material B. Both the virgin and charred states were examined to provide meaningful inputs to the design of a thermal protection system. Chars representative of the flight chars formed during ablation were prepared in a laboratory furnace from 600 K to 1700 K and properties of effective thermal conductivity, heat capacity, porosity and permeability were determined on the furnace chars formed at various temperature levels within the range. This provided a boxing of the data which will enable the prediction of the transient response of the material during flight ablation.

  19. Discrete Element study of granular material - Bumpy wall interface behavior

    NASA Astrophysics Data System (ADS)

    El Cheikh, Khadija; Rémond, Sébastien; Pizette, Patrick; Vanhove, Yannick; Djelal, Chafika

    2016-09-01

    This paper presents a DEM study of a confined granular material sheared between two parallel bumpy walls. The granular material consists of packed dry spherical particles. The bumpiness is modeled by spheres of a given diameter glued on horizontal planes. Different bumpy surfaces are modeled by varying diameter or concentration of glued spheres. The material is sheared by moving the two bumpy walls at fixed velocity. During shear, the confining pressure applied on each bumpy wall is controlled. The effect of wall bumpiness on the effective friction coefficient and on the granular material behavior at the bumpy walls is reported for various shearing conditions. For given bumpiness and confining pressure that we have studied, it is found that the shear velocity does not affect the shear stress. However, the effective friction coefficient and the behavior of the granular material depend on the bumpiness. When the diameter of the glued spheres is larger than about the average grains diameter of the medium, the latter is uniformly sheared and the effective friction coefficient remains constant. For smaller diameters of the glued spheres, the effective friction coefficient increases with the diameter of glued spheres. The influence of glued spheres concentration is significant only for small glued spheres diameters, typically half of average particle diameter of the granular material. In this case, increasing the concentration of glued spheres leads to a decrease in effective friction coefficient and to shear localization at the interface. For different diameters and concentrations of glued spheres, we show that the effect of bumpiness on the effective friction coefficient can be characterized by the depth of interlocking.

  20. Equations of State for Ablator Materials in Inertial Confinement Fusion Simulations

    NASA Astrophysics Data System (ADS)

    Sterne, P. A.; Benedict, L. X.; Hamel, S.; Correa, A. A.; Milovich, J. L.; Marinak, M. M.; Celliers, P. M.; Fratanduono, D. E.

    2016-05-01

    We discuss the development of the tabular equation of state (EOS) models for ablator materials in current use at Lawrence Livermore National Laboratory in simulations of inertial confinement fusion (ICF) experiments at the National Ignition Facility. We illustrate the methods with a review of current models for ablator materials and discuss some of the challenges in performing hydrocode simulations with high-fidelity multiphase models. We stress the importance of experimental data, as well as the utility of ab initio electronic structure calculations, in regions where data is not currently available. We illustrate why Hugoniot data alone is not sufficient to constrain the EOS models. These cases illustrate the importance of experimental EOS data in multi-megabar regimes, and the vital role they play in the development and validation of EOS models for ICF simulations.

  1. Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron

    PubMed Central

    Helber, Bernd; Chazot, Olivier; Hubin, Annick; Magin, Thierry E.

    2016-01-01

    Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution for future high-speed reentry missions. But despite the advancements made since Apollo, heat flux prediction remains an imperfect science and engineers resort to safety factors to determine the TPS thickness. This goes at the expense of embarked payload, hampering, for example, sample return missions. Ground testing in plasma wind-tunnels is currently the only affordable possibility for both material qualification and validation of material response codes. The subsonic 1.2MW Inductively Coupled Plasmatron facility at the von Karman Institute for Fluid Dynamics is able to reproduce a wide range of reentry environments. This protocol describes a procedure for the study of the gas/surface interaction on ablative materials in high enthalpy flows and presents sample results of a non-pyrolyzing, ablating carbon fiber precursor. With this publication, the authors envisage the definition of a standard procedure, facilitating comparison with other laboratories and contributing to ongoing efforts to improve heat shield reliability and reduce design uncertainties. The described core techniques are non-intrusive methods to track the material recession with a high-speed camera along with the chemistry in the reactive boundary layer, probed by emission spectroscopy. Although optical emission spectroscopy is limited to line-of-sight measurements and is further constrained to electronically excited atoms and molecules, its simplicity and broad applicability still make it the technique of choice for analysis of the reactive boundary layer. Recession of the ablating sample further requires that the distance of the measurement location with respect to the surface is known at all times during the experiment. Calibration of the optical system of the applied three spectrometers allowed quantitative comparison. At the fiber scale

  2. Emission Spectroscopic Boundary Layer Investigation during Ablative Material Testing in Plasmatron.

    PubMed

    Helber, Bernd; Chazot, Olivier; Hubin, Annick; Magin, Thierry E

    2016-01-01

    Ablative Thermal Protection Systems (TPS) allowed the first humans to safely return to Earth from the moon and are still considered as the only solution for future high-speed reentry missions. But despite the advancements made since Apollo, heat flux prediction remains an imperfect science and engineers resort to safety factors to determine the TPS thickness. This goes at the expense of embarked payload, hampering, for example, sample return missions. Ground testing in plasma wind-tunnels is currently the only affordable possibility for both material qualification and validation of material response codes. The subsonic 1.2MW Inductively Coupled Plasmatron facility at the von Karman Institute for Fluid Dynamics is able to reproduce a wide range of reentry environments. This protocol describes a procedure for the study of the gas/surface interaction on ablative materials in high enthalpy flows and presents sample results of a non-pyrolyzing, ablating carbon fiber precursor. With this publication, the authors envisage the definition of a standard procedure, facilitating comparison with other laboratories and contributing to ongoing efforts to improve heat shield reliability and reduce design uncertainties. The described core techniques are non-intrusive methods to track the material recession with a high-speed camera along with the chemistry in the reactive boundary layer, probed by emission spectroscopy. Although optical emission spectroscopy is limited to line-of-sight measurements and is further constrained to electronically excited atoms and molecules, its simplicity and broad applicability still make it the technique of choice for analysis of the reactive boundary layer. Recession of the ablating sample further requires that the distance of the measurement location with respect to the surface is known at all times during the experiment. Calibration of the optical system of the applied three spectrometers allowed quantitative comparison. At the fiber scale

  3. Modeling of plume dynamics in laser ablation processes for thin film deposition of materials

    SciTech Connect

    Leboeuf, J.N.; Chen, K.R.; Donato, J.M.; Geohegan, D.B.; Liu, C.L.; Puretzky, A.A.; Wood, R.F.

    1995-12-31

    The transport dynamics of laser-ablated neutral/plasma plumes are of significant interest for film growth by pulsed-laser deposition of materials since the magnitude and kinetic energy of the species arriving at the deposition substrate are key processing parameters. Dynamical calculations of plume propagation in vacuum and in background gas have been performed using particle-in-cell hydrodynamics, continuum gas dynamics, and scattering models. Results from these calculations are presented and compared with experimental observations.

  4. Development and evaluation of an ablative closeout material for solid rocket booster thermal protection system

    NASA Technical Reports Server (NTRS)

    Patterson, W. J.

    1979-01-01

    A trowellable closeout/repair material designated as MTA-2 was developed and evaluated for use on the Solid Rocket Booster. This material is composed of an epoxy-polysulfide binder and is highly filled with phenolic microballoons for density control and ablative performance. Mechanical property testing and thermal testing were performed in a wind tunnel to simulate the combined Solid Rocket Booster trajectory aeroshear and heating environments. The material is characterized by excellent thermal performance and was used extensively on the Space Shuttle STS-1 and STS-2 flight hardware.

  5. A simulation-based and analytic analysis of the off-Hugoniot response of alternative inertial confinement fusion ablator materials

    NASA Astrophysics Data System (ADS)

    Moore, Alastair S.; Prisbrey, Shon; Baker, Kevin L.; Celliers, Peter M.; Fry, Jonathan; Dittrich, Thomas R.; Wu, Kuang-Jen J.; Kervin, Margaret L.; Schoff, Michael E.; Farrell, Mike; Nikroo, Abbas; Hurricane, Omar A.

    2016-09-01

    The attainment of self-propagating fusion burn in an inertial confinement target at the National Ignition Facility will require the use of an ablator with high rocket-efficiency and ablation pressure. The ablation material used during the National Ignition Campaign (Lindl et al. 2014) [1], a glow-discharge polymer (GDP), does not couple as efficiently as simulations indicated to the multiple-shock inducing radiation drive environment created by laser power profile (Robey et al., 2012). We investigate the performance of two other ablators, boron carbide (B4C) and high-density carbon (HDC) compared to the performance of GDP under the same hohlraum conditions. Ablation performance is determined through measurement of the shock speed produced in planar samples of the ablator material subjected to the identical multiple-shock inducing radiation drive environments that are similar to a generic three-shock ignition drive. Simulations are in better agreement with the off-Hugoniot performance of B4C than either HDC or GDP, and analytic estimations of the ablation pressure indicate that while the pressure produced by B4C and GDP is similar when the ablator is allowed to release, the pressure reached by B4C seems to exceed that of HDC when backed by a Au/quartz layer.

  6. Geometrical modeling of surface profile formation during laser ablation of materials

    NASA Astrophysics Data System (ADS)

    Vatsya, S. R.; Bordatchev, E. V.; Nikumb, S. K.

    2003-06-01

    Recent advances in laser machining technology have made it possible to fabricate parts and features with high accuracy and precision, using high-powered, short-pulsed, Q-switched lasers. To determine the machining parameters to obtain the desired geometrical quality, an understanding of the relationship between the process parameters and the resulting surface profile is necessary. In the present study, we adopt a geometrical approach which, coupled with the material properties and machining process parameters, yields a method to determine the surface profile of the material ablated by a laser pulse. It is reasoned that the energy incident upon an infinitesimal area of the surface at a given time is transferred in the outward normal direction to the surface, and the volume of ablation, centered about the normal, is determined by the laser-material interaction and the process parameters. The direction and depth of ablation determine the modified surface profile an infinitesimal time later, yielding a nonlinear partial differential equation, which is then integrated starting with the initial known surface to determine the profile at an arbitrary time. Theoretical predictions and the experimental results are compared for a test case of metals. The agreement between the two is satisfactory indicating the adequacy of the approach.

  7. Micromachining of transparent materials by laser ablation of organic solution

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Niino, Hiroyuki; Yabe, Akira

    2000-11-01

    Transparent materials such as fused silica, quartz, calcium fluoride, and fluorocarbon polymer were etched upon irradiation of organic solution containing pyrene with a conventional KrF excimer laser. Threshold fluence for etching was 240 mJ/cm2 for fused silica. Etch rate remarkably depended on a concentration of pyrene: higher etch rate with the increase of pyrene concentration. It means that pyrene molecules play an important role in this process. The etch rate can be easily controlled through changing a laser pulse number, a laser fluence and a concentration of solution. The mechanism for this process is discussed by cyclic multiphotonic absorption of pyrene in the excited states, thermal relaxation, and formation of super-heated solution. As the results, it is suggested that the process is based on the combination of two processes in the interface between the transparent materials and the liquid: one is a heating process by a super-heated liquid and the other is an attacking process by a high temperature and pressure vapor.

  8. Optimization of laser ablation and signal enhancement for nuclear material detection

    NASA Astrophysics Data System (ADS)

    LaHaye, Nicole L.

    The purpose of the study was to investigate the role of different laser parameters on laser ablation properties, specifically in terms of performance in laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Many laser parameters affect laser ablation performance, including laser wavelength and pulse duration, as presented here. It was previously thought that wavelength plays no role in ultrafast laser ablation; however, it was found that shorter wavelength yields lower detection limits and ablation threshold. Our results also demonstrate that in the laser pulse duration range of 40 fs to 1 ps, negligible differences occur in signal intensity, elemental ratios, and detection limits. U/Pb and U/Th ratios, which were examined to ensure limited fractionation, give comparable results at all pulse widths investigated. A parametric study of plasma hydrodynamics will also be presented. An elemental detection method combining laser induced breakdown spectroscopy (LIBS) and LA-ICP-MS is developed, with plasma density and temperature actively monitored to investigate how plasma conditions affect ICP-MS results. The combination of these two methods will help to mitigate the disadvantages of using each technique individually. Depth and spatial analysis of thin films was performed using femtosecond LA-ICP-MS to study the stoichiometric distribution of the films. The thin film-substrate interface was probed, revealing intermixing between the two layers. Lastly, the persistence of uranium emission in laser-produced plasmas (LPP) was investigated under various Ar ambient environments. Plasma collisional effects and confinement play a very important role in emission intensity and persistence, yielding important results for future LIBS and laser absorption spectroscopy (LAS) research. Lastly, suggestions for future work are made, which include extension of the LIBS and LA-ICP-MS systems to other samples like oxide thin films and spatial and depth profiling of known

  9. Ablation by-products of dental materials from the Er:YAG laser and the dental handpiece

    NASA Astrophysics Data System (ADS)

    Wigdor, Harvey A.; Visuri, Steven R.; Walsh, Joseph T., Jr.

    1995-05-01

    Recently there has been much interest in lasers and their potential use to replace the dental drill. The research has been directed towards vital dental tissues. It must be understood that any laser to be used in dentistry which will replace the dental drill must also ablate and remove existing dental materials. Some concern exists about the ablation products when the Er:YAG laser is used to ablate dental materials. It is incumbent on the professionals using these lasers to understand the materials being produced by these lasers and protect themselves and their patients from possible toxic products. It is the intent of this paper to evaluate the products produced by the ablation of both dental amalgam and composite dental restorative materials and compare them with those produced by the traditional dental handpiece (drill).

  10. Flight and ground tests of a very low density elastomeric ablative material

    NASA Technical Reports Server (NTRS)

    Olsen, G. C.; Chapman, A. J., III

    1972-01-01

    A very low density ablative material, a silicone-phenolic composite, was flight tested on a recoverable spacecraft launched by a Pacemaker vehicle system; and, in addition, it was tested in an arc heated wind tunnel at three conditions which encompassed most of the reentry heating conditions of the flight tests. The material was composed, by weight, of 71 percent phenolic spheres, 22.8 percent silicone resin, 2.2 percent catalyst, and 4 percent silica fibers. The tests were conducted to evaluate the ablator performance in both arc tunnel and flight tests and to determine the predictability of the albator performance by using computed results from an existing one-dimensional numerical analysis. The flight tested ablator experienced only moderate surface recession and retained a smooth surface except for isolated areas where the char was completely removed, probably following reentry and prior to or during recovery. Analytical results show good agreement between arc tunnel and flight test results. The thermophysical properties used in the analysis are tabulated.

  11. Laser-solid interaction and dynamics of the laser-ablated materials

    SciTech Connect

    Chen, K.R.; Leboeuf, J.N.; Geohegan, D.B.; Wood, R.F.; Donato, J.M.; Liu, C.L.; Puretzky, A.A.

    1995-07-01

    Rapid transformations through the liquid and vapor phases induced by laser-solid interactions are described by the authors` thermal model with the Clausius-Clapeyron equation to determine the vaporization temperature under different surface pressure condition. Hydrodynamic behavior of the vapor during and after ablation is described by gas dynamic equations. These two models are coupled. Modeling results show that lower background pressure results lower laser energy density threshold for vaporization. The ablation rate and the amount of materials removed are proportional to the laser energy density above its threshold. The authors also demonstrate a dynamic source effect that accelerates the unsteady expansion of laser-ablated material in the direction perpendicular to the solid. A dynamic partial ionization effect is studied as well. A self-similar theory shows that the maximum expansion velocity is proportional to c{sub s}{alpha}, where 1 {minus} {alpha} is the slope of the velocity profile. Numerical hydrodynamic modeling is in good agreement with the theory. With these effects, {alpha} is reduced. Therefore, the expansion front velocity is significantly higher than that from conventional models. The results are consistent with experiments. They further study how the plume propagates in high background gas condition. Under appropriate conditions, the plume is slowed down, separates with the background, is backward moving, and hits the solid surface. Then, it splits into two parts when it rebounds from the surface. The results from the modeling will be compared with experimental observations where possible.

  12. Modeling of Heat Transfer and Ablation of Refractory Material Due to Rocket Plume Impingement

    NASA Technical Reports Server (NTRS)

    Harris, Michael F.; Vu, Bruce T.

    2012-01-01

    CR Tech's Thermal Desktop-SINDA/FLUINT software was used in the thermal analysis of a flame deflector design for Launch Complex 39B at Kennedy Space Center, Florida. The analysis of the flame deflector takes into account heat transfer due to plume impingement from expected vehicles to be launched at KSC. The heat flux from the plume was computed using computational fluid dynamics provided by Ames Research Center in Moffet Field, California. The results from the CFD solutions were mapped onto a 3-D Thermal Desktop model of the flame deflector using the boundary condition mapping capabilities in Thermal Desktop. The ablation subroutine in SINDA/FLUINT was then used to model the ablation of the refractory material.

  13. Non-Intrusive Sensor for In-Situ Measurement of Recession Rate of Ablative and Eroding Materials

    NASA Technical Reports Server (NTRS)

    Papadopoulos, George (Inventor); Tiliakos, Nicholas (Inventor); Benel, Gabriel (Inventor); Thomson, Clint (Inventor)

    2014-01-01

    A non-intrusive sensor for in-situ measurement of recession rate of heat shield ablatives. An ultrasonic wave source is carried in the housing. A microphone is also carried in the housing, for collecting the reflected ultrasonic waves from an interface surface of the ablative material. A time phasing control circuit is also included for time-phasing the ultrasonic wave source so that the waves reflected from the interface surface of the ablative material focus on the microphone, to maximize the acoustic pressure detected by the microphone and to mitigate acoustic velocity variation effects through the material through a de-coupling process that involves a software algorithm. A software circuit for computing the location off of which the ultrasonic waves scattered to focus back at the microphone is also included, so that the recession rate of the heat shield ablative may be monitored in real-time through the scan-focus approach.

  14. Laser spectrometry and laser ablation - an ideal solution for the analysis of nuclear materials

    SciTech Connect

    Goodall, P.; Johnson, S.G.

    1996-09-01

    Nuclear materials, consisting primarily of actinides and lanthanides, produce a plethora of emission lines from the ICP. This provides an entertaining problem for the analyst applying ICP-AES. Laser ablation ICP-AES (LA-ICP-AES) offers unique advantages for the analysis of nuclear materials as it allows remote analysis of these materials in heavily shielded environments. The use of high resolution spectrometry, when coupled with LA-ICP-AES, simplifies the spectral chaos normally encountered with these materials. This obviates the requirement for analyte separation which standard ICP-AES instrumentation demands. Examples of the analysis of nuclear fuels and materials used in the reprocessing of that fuel will be presented (e.g., the determination of U, La, Y, Ce and Nd in molten salts.). In addition to bulk (or local) chemical composition, it is also possible to extract isotopic information using high resolution LA-ICP-AES (e.g., the determination of {sup 236}U for the estimation of {open_quotes}burn-up{close_quotes} of {sup 235}U in a nuclear reactor). Laser excited atomic fluorescence (LEAFS) has the advantage of high specificity at the expense of instrumental sophistication but provides one solution to the spectral complexity encountered with nuclear materials. The potential of laser ablation coupled to ICP-LEAFS will be discussed and the determination of lanthanides by LA-ICP-LEAFS described.

  15. Theoretical and experimental modelling of the turbulent dissolution of a vertical ice wall in salty water, and its application to the ablation of icebergs and ice shelves.

    NASA Astrophysics Data System (ADS)

    Kerr, R. C.; McConnochie, C.

    2014-12-01

    We examine theoretically and experimentally the dissolution of a vertical ice wall in the case where the heat and salt transfer is driven by turbulent compositional convection. A theoretical model of the turbulent dissolution is first developed, which predicts the interface temperature, interface concentration and interface dissolution velocity. The analysis is then tested by comparing it with laboratory measurements of the ablation of a vertical ice wall in contact with salty water. The model is found to accurately predict both the dissolution velocity and the interface temperature, for water temperatures up to about 6 degrees Celsius, where there is a transition from turbulent dissolution to turbulent melting. When applied to the ablation of icebergs and ice shelves in contact with seawater, we predict convective dissolution velocities in good agreement with field observations.

  16. Innovative tokamak DEMO first wall and divertor material concepts

    NASA Astrophysics Data System (ADS)

    Wong, C. P. C.

    2009-06-01

    ITER has selected Be as the first wall and C and W as the divertor surface materials. When extrapolated to the DEMO design, C and Be layers will not be suitable due to radiation damage. The remaining material, W, could also suffer radiation damage from helium ion implantation and experience blistering at the first wall and form submicron fine structure at the divertor. In this paper we introduce a new concept called the boron W-mesh (BW-mesh) in which B is infiltrated into a W-mesh. The goal is to use a thin coating of B to protect the W-mesh from helium ion damage and to maintain a sufficient amount of B to protect the W from transient events like edge localized modes (ELMs) and disruptions. Critical issues and corresponding development of this BW-mesh concept have been identified, including the need for real time boronization.

  17. Lightweight Ablative and Ceramic Thermal Protection System Materials for NASA Exploration Systems Vehicles

    NASA Technical Reports Server (NTRS)

    Valentine, Peter G.; Lawrence, Timothy W.; Gubert, Michael K.; Milos, Frank S.; Kiser, James D.; Ohlhorst, Craig W.; Koenig, John R.

    2006-01-01

    As a collaborative effort among NASA Centers, the "Lightweight Nonmetallic Thermal Protection Materials Technology" Project was set up to assist mission/vehicle design trade studies, to support risk reduction in thermal protection system (TPS) material selections, to facilitate vehicle mass optimization, and to aid development of human-rated TPS qualification and certification plans. Missions performing aerocapture, aerobraking, or direct aeroentry rely on advanced heatshields that allow reductions in spacecraft mass by minimizing propellant requirements. Information will be presented on candidate materials for such reentry approaches and on screening tests conducted (material property and space environmental effects tests) to evaluate viable candidates. Seventeen materials, in three classes (ablatives, tiles, and ceramic matrix composites), were studied. In additional to physical, mechanical, and thermal property tests, high heat flux laser tests and simulated-reentry oxidation tests were performed. Space environmental effects testing, which included exposures to electrons, atomic oxygen, and hypervelocity impacts, was also conducted.

  18. Data Report on Material Ablation and Shock Pressure Measurements at ZBL

    SciTech Connect

    Lawrence Livermore National Laboratory

    2007-01-03

    A series of tests were conducted on Z-Beamlet Laser (ZBL) to provide data that can be used to determine the laser coupling coefficient and validate code capabilities. The gauges and cables in the chamber were shielded with conduit and resulted in high fidelity signals. The stress measurements show a clear trend of peak stress attenuation with propagation distance, as would be expected. The aluminum sample stresses measured were in the 4 to 8 Kbar range. This constitutes a good data set for model validation. VISAR was considered as a diagnostic for this test series but predicted stress levels were uncertain and we had good success previously with PVDF at this test facility; plus, the aggressive test schedule and limited number of shots left little opportunity to set up this diagnostic. Shock profile measurements were made with both PVDF and Quartz gauges. The PVDF gauge and the Quartz gauge measured very similar shock pulses transmitted through 1.5-mm thick 2024-T3 samples at a nominal fluence of 400 J/cm{sup 2}. The similarity in the two profiles indicates good correlation between measurement techniques and the differences between the sensor areas allow one to evaluate different parts of the beam. The laser beam ablated the front surfaces of the samples. Surface profile measurements of the ablated surface were used to estimate the depth of material removed. Ablated sample surface and crater formation indicate a non-uniform hot spot in the center of the sample.

  19. Wire Cloth as Porous Material for Transpiration-cooled Walls

    NASA Technical Reports Server (NTRS)

    Eckert, E R G; Kinsler, Martin R; Cochran, Reeves B

    1951-01-01

    The permeability characteristics and tensile strength of a porous material developed from stainless-steel corduroy wire cloth for use in transpiration-cooled walls where the primary stresses are in one direction were investigated. The results of this investigation are presented and compared with similar results obtained with porous sintered metal compacts. A much wider range of permeabilities is obtainable with the wire cloth than with the porous metal compacts considered and the ultimate tensile strength in the direction of the primary stresses for porous materials produced from three mesh sizes of wire cloth are from two to three times the ultimate tensile strengths of the porous metal compacts.

  20. Thermal performance of 625-kg/cu m elastomeric ablative materials on spherically blunted 0.44-radian cones

    NASA Technical Reports Server (NTRS)

    Champman, A. J.

    1972-01-01

    Spherically blunted 0.44-radian (25 deg) half-angle conical models coated with elastomeric ablative materials were tested in supersonic arc-heated wind tunnels to evaluate performance of the ablators over a range of conditions typical of lifting entry. Four test conditions were combinations of stagnation point-heat transfer rates of 2.3 and 4.5 MW/m2 and stagnation pressures of 20 and 2kN/m2. Afterbody values of heat transfer rate and pressure were 0.05 to 0.20 of stagnation point values. Stagnation enthalpy varied from 4.4 to 25 MJ/kg (1900 to 11000 Btu/lbm) and free-stream Mach number was in a range from 3.5 to 4. Ablative materials retained the spherical nose shape throughout tests at the lower heat transfer level, but receded, assuming a flattened nose shape, during tests at the high heat transfer level. The residue layer that formed on the conical after-body was weak, friable, and extensively cracked. The reference ablative material, which contained phenolic microspheres, generally retained the conical shape on the model afterbody. However, a modified ablator, in which phenolic microspheres were replaced with silica microspheres, deformed and separated from the undegraded material, and thereby produced a very uneven surface. Substrate temperatures and ablator recession were in good agreement with values computed by a numerical analysis.

  1. Strain Sensitivity in Single Walled Carbon Nanotubes for Multifunctional Materials

    NASA Technical Reports Server (NTRS)

    Heath, D. M. (Technical Monitor); Smits, Jan M., VI

    2005-01-01

    Single walled carbon nanotubes represent the future of structural aerospace vehicle systems due to their unparalleled strength characteristics and demonstrated multifunctionality. This multifunctionality rises from the CNT's unique capabilities for both metallic and semiconducting electron transport, electron spin polarizability, and band gap modulation under strain. By incorporating the use of electric field alignment and various lithography techniques, a single wall carbon nanotube (SWNT) test bed for measurement of conductivity/strain relationships has been developed. Nanotubes are deposited at specified locations through dielectrophoresis. The circuit is designed such that the central, current carrying section of the nanotube is exposed to enable atomic force microscopy and manipulation in situ while the transport properties of the junction are monitored. By applying this methodology to sensor development a flexible single wall carbon nanotube (SWNT) based strain sensitive device has been developed. Studies of tensile testing of the flexible SWNT device vs conductivity are also presented, demonstrating the feasibility of using single walled HiPCO (high-pressure carbon monoxide) carbon nanotubes as strain sensing agents in a multi-functional materials system.

  2. Photothermal ablation of bone metastasis of breast cancer using PEGylated multi-walled carbon nanotubes

    PubMed Central

    Lin, Zhen; Liu, Yi; Ma, Xueming; Hu, Shaoyu; Zhang, Jiawei; Wu, Qian; Ye, Wenbin; Zhu, Siyuan; Yang, Dehong; Qu, Dongbin; Jiang, Jianming

    2015-01-01

    This study investigates therapeutic efficacy of photothermal therapy (PTT) in an orthotropic xenograft model of bone metastasis of breast cancer. The near-infrared (NIR) irradiation on Multi-Walled Carbon Nanotubes (MWNTs) resulted in a rapid heat generation which increased with the MWNTs concentration up to 100 μg/ml. MWNTs alone exhibited no toxicity, but inclusion of MWNTs dramatically decreased cell viability when combined with laser irradiation. Thermographic observation revealed that treatment with 10 μg MWNTs followed by NIR laser irradiation resulted in a rapid increase in temperature up to 73.4±11.98 °C in an intraosseous model of bone metastasis of breast cancer. In addition, MWNTs plus NIR laser irradiation caused a remarkably greater suppression of tumor growth compared with treatment with either MWNTs injection or NIR irradiation alone, significantly reducing the amount of tumor-induced bone destruction. All these demonstrate the efficacy of PTT with MWNTs for bone metastasis of breast cancer. PMID:26122018

  3. Laser Ablation/Ionisation Mass Spectrometry: Sensitive and Quantitative Chemical Depth Profiling of Solid Materials.

    PubMed

    Riedo, Andreas; Grimaudo, Valentine; Moreno-García, Pavel; Neuland, Maike B; Tulej, Marek; Broekmann, Peter; Wurz, Peter

    2016-01-01

    Direct quantitative and sensitive chemical analysis of solid materials with high spatial resolution, both in lateral and vertical direction is of high importance in various fields of analytical research, ranging from in situ space research to the semiconductor industry. Accurate knowledge of the chemical composition of solid materials allows a better understanding of physical and chemical processes that formed/altered the material and allows e.g. to further improve these processes. So far, state-of-the-art techniques such as SIMS, LA-ICP-MS or GD-MS have been applied for chemical analyses in these fields of research. In this report we review the current measurement capability and the applicability of our Laser Ablation/Ionisation Mass Spectrometer (instrument name LMS) for the chemical analysis of solids with high spatial resolution. The most recent chemical analyses conducted on various solid materials, including e.g. alloys, fossils and meteorites are discussed. PMID:27131112

  4. Laser ablation in liquids as a new technique of sampling in elemental analysis of solid materials

    NASA Astrophysics Data System (ADS)

    Muravitskaya, E. V.; Rosantsev, V. A.; Belkov, M. V.; Ershov-Pavlov, E. A.; Klyachkovskaya, E. V.

    2009-02-01

    Laser ablation in liquid media is considered as a new sample preparation technique in the elemental composition analysis of materials using optical emission spectroscopy of inductively coupled plasma (ICP-OES). Solid samples are transformed into uniform colloidal solutions of nanosized analyte particles using laser radiation focused onto the sample surface. High homogeneity of the resulting solution allows performing the ICP-OES quantitative analysis especially for the samples, which are poorly soluble in acids. The technique is compatible with the conventional solution-based standards.

  5. Ablative material testing for low-pressure, low-cost rocket engines

    NASA Technical Reports Server (NTRS)

    Richter, G. Paul; Smith, Timothy D.

    1995-01-01

    The results of an experimental evaluation of ablative materials suitable for the production of light weight, low cost rocket engine combustion chambers and nozzles are presented. Ten individual specimens of four different compositions of silica cloth-reinforced phenolic resin materials were evaluated for comparative erosion in a subscale rocket engine combustion chamber. Gaseous hydrogen and gaseous oxygen were used as propellants, operating at a nominal chamber pressure of 1138 kPa (165 psi) and a nominal mixture ratio (O/F) of 3.3. These conditions were used to thermally simulate operation with RP-1 and liquid oxygen, and achieved a specimen throat gas temperature of approximately 2456 K (4420 R). Two high-density composition materials exhibited high erosion resistance, while two low-density compositions exhibited approximately 6-75 times lower average erosion resistance. The results compare favorably with previous testing by NASA and provide adequate data for selection of ablatives for low pressure, low cost rocket engines.

  6. [In vitro studies of shock wave effects during ablation of normal and atherosclerotic vascular wall by excimer laser].

    PubMed

    Haase, K K; Hanke, H; Baumbach, A; Wehrmann, M; Rose, C; Karsch, K R

    1993-02-01

    Ablation of atherosclerotic plaque and normal arterial wall was performed using a xenon-chloride-excimer laser with a wavelength of 308 nm and a pulse duration of 115 ns. The light was transmitted via a 600 micron fiber and adjusted to an energy density of 3.5 J/cm2. The acoustic signals generated by the laser pulse were measured with hydrophones consisting of polyvinylidenefluoride with active diameters of 0.3 mm and recorded on a dual-channel digital storage oscilloscope using either a 0.5 m coaxial cable or a broadband transmission system. From 19 cadavers human aortic tissue segments were excised and macroscopically classified as either normal or calcified atherosclerotic plaque. Approximately 500 measurements were performed in saline and blood each. Histological analysis was carried out after the experiments to verify the macroscopic diagnosis and to correlate the acoustic responses with the tissue characteristics. For "normal" arterial segments, maximum peak pressure was 1.25 MPa +/- 0.85 MPa, rise time 163 ns +/- 43 ns, and pressure increase 8.2 kPa +/- 5.4 kPa/ns in saline. For calcified, atheromatous segments a significantly higher maximum pressure (2.20 MPa +/- 1.16 MPa), a significantly shorter rise time (69.9 ns +/- 25.8 ns), and a significantly higher pressure increase (32.3 kPa +/- 21.3 kPa/ns) was found in saline (p < or = 0.0001). In blood, maximum peak pressure was 1.29 MPa +/- 0.43 MPa, rise time 93.3 ns +/- 27.7 ns, and pressure increase 14.6 kPa +/- 5.2 kPa/ns for "normal" arterial segments. Maximum peak pressure (2.28 MPa +/- 0.63 MPa) and pressure increase (32.8 kPa +/- Pa/ns) were significantly higher for calcified tissue segments.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8465570

  7. Experimental performance of an ablative material as an external insulator for a hypersonic research aircraft

    NASA Technical Reports Server (NTRS)

    Puster, R. L.; Chapman, A. J.

    1977-01-01

    An ablative material composed of silica-filled elastomeric silicone was tested to evaluate its thermal and structural performance as an external insulator, or heat shield, for a hypersonic research aircraft. The material was also tested to determine whether it would form a durable char layer when initially heated and thereafter function primarily as an insulator with little further pyrolysis or char removal. Aerothermal tests were representative of nominal Mach 6 cruise conditions of the aircraft, and additional tests were representative of Mach 8 cruise and interference heating conditions. Radiant heating tests were used to simulate the complete nominal Mach 6 surface-temperature history. The silica char that formed during aerothermal tests was not durable. The char experienced a general and preferential surface recession, with the primary mechanism for char removal being erosion. Tests revealed that radiant heating is not a valid technique for simulating aerodynamic heating of the material.

  8. A Short Review of Ablative-Material Response Models and Simulation Tools

    NASA Technical Reports Server (NTRS)

    Lachaud, Jean; Magin, Thierry E.; Cozmuta, Ioana; Mansour, Nagi N.

    2011-01-01

    A review of the governing equations and boundary conditions used to model the response of ablative materials submitted to a high-enthalpy flow is proposed. The heritage of model-development efforts undertaken in the 1960s is extremely clear: the bases of the models used in the community are mathematically equivalent. Most of the material-response codes implement a single model in which the equation parameters may be modified to model different materials or conditions. The level of fidelity of the models implemented in design tools only slightly varies. Research and development codes are generally more advanced but often not as robust. The capabilities of each of these codes are summarized in a color-coded table along with research and development efforts currently in progress.

  9. Near-infrared laser ablation of poly tetrafluoroethylene (Teflon) sensitized by nanoenergetic materials

    SciTech Connect

    Yang Yanqiang; Wang Shufeng; Sun Zhaoyong; Dlott, Dana D.

    2004-08-30

    Laser ablation of Teflon doped with size-selected (30-250 nm) Al nanoparticles is studied. Unlike pure Teflon, which requires a vacuum-ultraviolet or femtosecond excimer laser for ablation, this sensitized Teflon can be ablated with a near-infrared laser. Using 100 ps duration pulses, near-infrared ablation thresholds are lower by about a factor of 10 from excimer ablation of pure Teflon. A mechanism is discussed that involves Teflon decomposition by spherical shock fronts originating at each irradiated nanoparticle. Studies of the distance dependence of this process as a function of particle diameter and oxide layer thickness suggest ways of optimizing the ablation process.

  10. Graphite and ablative material response to CO2 laser, carbon-arc, and xenon-arc radiation

    NASA Technical Reports Server (NTRS)

    Brewer, W. D.

    1976-01-01

    The behavior was investigated of graphite and several charring ablators in a variety of high-radiative heat-flux environments. A commercial-grade graphite and nine state-of-the-art charring ablators were subjected to various radiative environments produced by a CO2 laser and a carbon arc. Graphite was also tested in xenon-arc radiation. Heat-flux levels ranged from 10 to 47 MW/sq m. Tests were conducted in air, nitrogen, helium, and a CO2-N2 mixture which simulated the Venus atmosphere. The experimental results were compared with theoretical results obtained with a one-dimensional charring-ablator analysis and a two-dimensional subliming-ablator analysis. Neither the graphite nor the charring ablators showed significant differences in appearance or microstructure after testing in the different radiative environments. The performance of phenolic nylon and graphite was predicted satisfactorily with existing analyses and published material property data. Good agreement between experimental and analytical results was obtained by using sublimation parameters from a chemical nonequilibrium analysis of graphite sublimation. Some charring ablators performed reasonably well and could withstand radiative fluxes of the level encountered in certain planetary entries. Other materials showed excessive surface recession and/or large amounts of cracking and spalling, and appear to be unsuitable for severe radiative environments.

  11. Automatic classification of scar tissue in late gadolinium enhancement cardiac MRI for the assessment of left-atrial wall injury after radiofrequency ablation

    NASA Astrophysics Data System (ADS)

    Perry, Daniel; Morris, Alan; Burgon, Nathan; McGann, Christopher; MacLeod, Robert; Cates, Joshua

    2012-03-01

    Radiofrequency ablation is a promising procedure for treating atrial fibrillation (AF) that relies on accurate lesion delivery in the left atrial (LA) wall for success. Late Gadolinium Enhancement MRI (LGE MRI) at three months post-ablation has proven effective for noninvasive assessment of the location and extent of scar formation, which are important factors for predicting patient outcome and planning of redo ablation procedures. We have developed an algorithm for automatic classification in LGE MRI of scar tissue in the LA wall and have evaluated accuracy and consistency compared to manual scar classifications by expert observers. Our approach clusters voxels based on normalized intensity and was chosen through a systematic comparison of the performance of multivariate clustering on many combinations of image texture. Algorithm performance was determined by overlap with ground truth, using multiple overlap measures, and the accuracy of the estimation of the total amount of scar in the LA. Ground truth was determined using the STAPLE algorithm, which produces a probabilistic estimate of the true scar classification from multiple expert manual segmentations. Evaluation of the ground truth data set was based on both inter- and intra-observer agreement, with variation among expert classifiers indicating the difficulty of scar classification for a given a dataset. Our proposed automatic scar classification algorithm performs well for both scar localization and estimation of scar volume: for ground truth datasets considered easy, variability from the ground truth was low; for those considered difficult, variability from ground truth was on par with the variability across experts.

  12. Characterization of material ablation driven by laser generated intense extreme ultraviolet light

    NASA Astrophysics Data System (ADS)

    Tanaka, Nozomi; Masuda, Masaya; Deguchi, Ryo; Murakami, Masakatsu; Sunahara, Atsushi; Fujioka, Shinsuke; Yogo, Akifumi; Nishimura, Hiroaki

    2015-09-01

    We present a comparative study on the hydrodynamic behaviour of plasmas generated by material ablation by the irradiation of nanosecond extreme ultraviolet (EUV or XUV) or infrared laser pulses on solid samples. It was clarified that the difference in the photon energy deposition and following material heating mechanism between these two lights result in the difference in the plasma parameters and plasma expansion characteristics. Silicon plate was ablated by either focused intense EUV pulse (λ = 9-25 nm, 10 ns) or laser pulse (λ = 1064 nm, 10 ns), both with an intensity of ˜109 W/cm2. Both the angular distributions and energy spectra of the expanding ions revealed that the photoionized plasma generated by the EUV light differs significantly from that produced by the laser. The laser-generated plasma undergoes spherical expansion, whereas the EUV-generated plasma undergoes planar expansion in a comparatively narrow angular range. It is presumed that the EUV radiation is transmitted through the expanding plasma and directly photoionizes the samples in the solid phase, consequently forming a high-density and high-pressure plasma. Due to a steep pressure gradient along the direction of the target normal, the EUV plasma expands straightforward resulting in the narrower angular distribution observed.

  13. Materials for Multifunctional Balloon Catheters With Capabilities in Cardiac Electrophysiological Mapping and Ablation Therapy

    PubMed Central

    Kim, Dae-Hyeong; Lu, Nanshu; Ghaffari, Roozbeh; Kim, Yun-Soung; Lee, Stephen P.; Xu, Lizhi; Wu, Jian; Kim, Rak-Hwan; Song, Jizhou; Liu, Zhuangjian; Viventi, Jonathan; de Graff, Bassel; Elolampi, Brian; Mansour, Moussa; Slepian, Marvin J.; Hwang, Sukwon; Moss, Joshua D.; Won, Sang-Min; Huang, Younggang; Litt, Brian; Rogers, John A.

    2011-01-01

    Development of advanced surgical tools for minimally invasive procedures represents an activity of central importance to improvements in human health. A key materials challenge is in the realization of bio-compatible interfaces between the classes of semiconductor and sensor technologies that might be most useful in this context and the soft, curvilinear surfaces of the body. This paper describes a solution based on biocompatible materials and devices that integrate directly with the thin elastic membranes of otherwise conventional balloon catheters, to provide multimodal functionality suitable for clinical use. We present sensors for measuring temperature, flow, tactile, optical and electrophysiological data, together with radio frequency (RF) electrodes for controlled, local ablation of tissue. These components connect together in arrayed layouts designed to decouple their operation from large strain deformations associated with deployment and repeated inflation/deflation. Use of such ‘instrumented’ balloon catheter devices in live animal models and in vitro tests illustrates their operation in cardiac ablation therapy. These concepts have the potential for application in surgical systems of the future, not only those based on catheters but also on other platforms, such as surgical gloves. PMID:21378969

  14. Matrix Effects on Boron Containing Materials due to Laser Ablation Molecular Isotopic Spectrometry (LAMIS)

    NASA Astrophysics Data System (ADS)

    Brown, Staci R.; Akpovo, Charlemagne A.; Martinez, Jorge; Ford, Alan; Herbert, Kenley; Johnson, Lewis

    2014-03-01

    Laser Induced Breakdown Spectroscopy (LIBS) is a spectroscopic technique that is used for the qualitative and quantitative analysis of materials in the liquid, solid, or gas phase. LIBS can also be used for the detection of isotopic shifts in atomic and diatomic species via Laser-Ablation Molecular Isotopic Spectroscopy (LAMIS). However, any additional elements that are entrained into the plasma other than the element of interest, can affect the extent of ablation and quality of spectra and hence, potentially obscure or aid in the relative abundance assessment for a given element. To address the importance of matrix effects, the isotopic analysis of boron obtained from boron oxide (BO) emission originating from different boron-containing compounds, such as boron nitride (BN), boric acid (H3BO3) , and borax (Na2B4O710H2O), via LIBS has been performed here. Each of these materials has different physical properties and elemental composition in order to illustrate possible challenges for the LAMIS method. A calibration-free model similar to that for the original LAMIS work is used to determine properties of the plasma as the matrix is changed. DTRA

  15. Characterization of material ablation driven by laser generated intense extreme ultraviolet light

    SciTech Connect

    Tanaka, Nozomi Masuda, Masaya; Deguchi, Ryo; Murakami, Masakatsu; Fujioka, Shinsuke; Yogo, Akifumi; Nishimura, Hiroaki; Sunahara, Atsushi

    2015-09-14

    We present a comparative study on the hydrodynamic behaviour of plasmas generated by material ablation by the irradiation of nanosecond extreme ultraviolet (EUV or XUV) or infrared laser pulses on solid samples. It was clarified that the difference in the photon energy deposition and following material heating mechanism between these two lights result in the difference in the plasma parameters and plasma expansion characteristics. Silicon plate was ablated by either focused intense EUV pulse (λ = 9–25 nm, 10 ns) or laser pulse (λ = 1064 nm, 10 ns), both with an intensity of ∼10{sup 9 }W/cm{sup 2}. Both the angular distributions and energy spectra of the expanding ions revealed that the photoionized plasma generated by the EUV light differs significantly from that produced by the laser. The laser-generated plasma undergoes spherical expansion, whereas the EUV-generated plasma undergoes planar expansion in a comparatively narrow angular range. It is presumed that the EUV radiation is transmitted through the expanding plasma and directly photoionizes the samples in the solid phase, consequently forming a high-density and high-pressure plasma. Due to a steep pressure gradient along the direction of the target normal, the EUV plasma expands straightforward resulting in the narrower angular distribution observed.

  16. Single Wall Carbon Nanotube-Based Structural Health Sensing Materials

    NASA Technical Reports Server (NTRS)

    Watkins, A. Neal; Ingram, JoAnne L.; Jordan, Jeffrey D.; Wincheski, Russell A.; Smits, Jan M.; Williams, Phillip A.

    2004-01-01

    Single wall carbon nanotube (SWCNT)-based materials represent the future aerospace vehicle construction material of choice based primarily on predicted strength-to-weight advantages and inherent multifunctionality. The multifunctionality of SWCNTs arises from the ability of the nanotubes to be either metallic or semi-conducting based on their chirality. Furthermore, simply changing the environment around a SWCNT can change its conducting behavior. This phenomenon is being exploited to create sensors capable of measuring several parameters related to vehicle structural health (i.e. strain, pressure, temperature, etc.) The structural health monitor is constructed using conventional electron-beam lithographic and photolithographic techniques to place specific electrode patterns on a surface. SWCNTs are then deposited between the electrodes using a dielectrophoretic alignment technique. Prototypes have been constructed on both silicon and polyimide substrates, demonstrating that surface-mountable and multifunctional devices based on SWCNTs can be realized.

  17. Ablative Thermal Protection System Fundamentals

    NASA Technical Reports Server (NTRS)

    Beck, Robin A. S.

    2013-01-01

    This is the presentation for a short course on the fundamentals of ablative thermal protection systems. It covers the definition of ablation, description of ablative materials, how they work, how to analyze them and how to model them.

  18. Hydrogen film cooling of a small hydrogen-oxygen thrust chamber and its effect on erosion rates of various ablative materials

    NASA Technical Reports Server (NTRS)

    Hannum, N.; Roberts, W. E.; Russell, L. M.

    1977-01-01

    An experimental investigation was conducted to determine what arrangement of film-coolant-injection orifices should be used to decrease the erosion rates of small, high temperature, high pressure ablative thrust chambers without incurring a large penalty in combustion performance. All of the film cooling was supplied through holes in a ring between the outer row of injector elements and the chamber wall. The best arrangement, which had twice the number of holes as there were outer row injection elements, was also the simplest. The performance penalties, presented as a reduction in characteristic exhaust velocity efficiency, were 0.8 and 2.8 percentage points for the 10 and 20 percent cooling flows, respectively, The best film-coolant injector was then used to obtain erosion rates for 19 ablative materials. The throat erosion rate was reduced by a factor of 2.5 with a 10 percent coolant flow. Only the more expensive silica phenolic materials had low enough erosion rates to be considered for use in the nozzle throat. However, some of the cheaper materials might qualify for use in other areas of small nozzles with large throat diameters where the higher erosion rates are more acceptable.

  19. Spark ablation-inductively coupled plasma spectrometry for analysis of geologic materials

    USGS Publications Warehouse

    Golightly, D.W.; Montaser, A.; Smith, B.L.; Dorrzapf, A.F., Jr.

    1989-01-01

    Spark ablation-inductively coupled plasma (SA-ICP) spectrometry is applied to the measurement of hafnium-zirconium ratios in zircons and to the determination of cerium, cobalt, iron, lead, nickel and phosphorus in ferromanganese nodules. Six operating parameters used for the high-voltage spark and argon-ICP combination are established by sequential simplex optimization of both signal-to-background ratio and signal-to-noise ratio. The time-dependences of the atomic emission signals of analytes and matrix elements ablated from a finely pulverized sample embedded in a pressed disk of copper demonstrate selective sampling by the spark. Concentration ratios of hafnium to zirconium in zircons are measured with a precision of 4% (relative standard deviation, RSD). For ferromanganese nodules, spectral measurements based on intensity ratios of analyte line to the Mn(II) 257.610 nm line provide precisions of analysis in the range from 7 to 14% RSD. The accuracy of analysis depends on use of standard additions of the reference material USGS Nod P-1, and an independent measurement of the Mn concentration. ?? 1989.

  20. Ablation of high-Z material dust grains in edge plasmas of magnetic fusion devices

    SciTech Connect

    Marenkov, E. D.; Krasheninnikov, S. I.

    2014-12-15

    The model, including shielding effects of high-Z dust grain ablation in tokamak edge plasma, is presented. In a contrast to shielding models developed for pellets ablation in a hot plasma core, this model deals with the dust grain ablation in relatively cold edge plasma. Using some simplifications, a closed set of equations determining the grain ablation rate Γ is derived and analyzed both analytically and numerically. The scaling law for Γ versus grain radius and ambient plasma parameters is obtained and confirmed by the results of numerical solutions. The results obtained are compared with both dust grain models containing no shielding effects and the pellet ablation models.

  1. Ablation of high-Z material dust grains in edge plasmas of magnetic fusion devices

    NASA Astrophysics Data System (ADS)

    Marenkov, E. D.; Krasheninnikov, S. I.

    2014-12-01

    The model, including shielding effects of high-Z dust grain ablation in tokamak edge plasma, is presented. In a contrast to shielding models developed for pellets ablation in a hot plasma core, this model deals with the dust grain ablation in relatively cold edge plasma. Using some simplifications, a closed set of equations determining the grain ablation rate Γ is derived and analyzed both analytically and numerically. The scaling law for Γ versus grain radius and ambient plasma parameters is obtained and confirmed by the results of numerical solutions. The results obtained are compared with both dust grain models containing no shielding effects and the pellet ablation models.

  2. Laser ablation inductively coupled plasma optical emission spectrometry for analysis of pellets of plant materials

    NASA Astrophysics Data System (ADS)

    Gomes, Marcos S.; Schenk, Emily R.; Santos, Dário; Krug, Francisco José; Almirall, José R.

    An evaluation of laser ablation inductively coupled plasma optical emission spectroscopy (LAICP OES) for the direct analysis of pelleted plant material is reported. Ground leaves of orange citrus, soy and sugarcane were comminuted using a high-speed ball mill, pressed into pellets and sampled directly with laser ablation and analyzed by ICP OES. The limits of detection (LODs) for the method ranged from as low as 0.1 mg kg- 1 for Zn to as high as 94 mg kg- 1 for K but were generally below 6 mg kg- 1 for most of the elements of interest. A certified reference material consisting of a similar matrix (NIST SRM 1547 peach leaves) was used to check the accuracy of the calibration and the reported method resulted in an average bias of ~ 5% for all the elements of interest. The precision for the reported method ranged from as low as 4% relative standard deviation (RSD) for Mn to as high as 17% RSD for Zn but averaged ~ 6.5% RSD for all the elements (n = 10). The proposed method was tested for the determination of Ca, Mg, P, K, Fe, Mn, Zn and B, and the results were in good agreement with those obtained for the corresponding acid digests by ICP-OES, no differences being observed by applying a paired t-test at the 95% confidence level. The reported direct solid sampling method provides a fast alternative to acid digestion that results in similar and appropriate analytical figures of merit with regard to sensitivity, accuracy and precision for plant material analysis.

  3. Subscale Testing of Nozzle Ablative Materials in a Supersonic Particle Impingement Environment

    NASA Technical Reports Server (NTRS)

    Howse, S.; Lawrence, T.

    2004-01-01

    Recent efforts to evaluate materials to replace the current NARC rayon used in the nozzle ablative of the NASA's Reusable Solid Rocket Motor (SRM), several tests were developed to look at the performance of supersonic particle impact region of the aft exit cone. It was seen in early testing that some potential candidates did not perform as well as the current NARC based material and so the 24 inch Solid Rocket Motor (SRTM) exit cone design was extended and contoured to induce particle impingement in the aft end. The SRTM testing provided a larger testbed to evaluate the results seen in the Solid Fuel Supersonic Blast Tube. Testing was performed in each test bed on two variants of the final two candidate materials. The materials were a standard prewoven Lyocell, a postwoven Lyocell, an Enka rayon, and Enka rayon processed at a higher carbonization temperature. This paper presents the results of the four materials in the SSBT and the SRTM tests as compared against the NARC baseline. Erosion, char, and plylift results are discussed in detail.

  4. Modeling Initial Stage of Ablation Material Pyrolysis: Graphitic Precursor Formation and Interfacial Effects

    NASA Technical Reports Server (NTRS)

    Desai, Tapan G.; Lawson, John W.; Keblinski, Pawel

    2010-01-01

    Reactive molecular dynamics simulations are used to study initial stage of pyrolysis of ablation materials and their composites with carbon nanotubes and carbon fibers. The products formed during pyrolysis are characterized and water is found as the primary product in all cases. The water formation mechanisms are analyzed and the value of the activation energy for water formation is estimated. A detailed study on graphitic precursor formation reveals the presence of two temperature zones. In the lower temperature zone (less than 2000 K) polymerization occurs resulting in formation of large, stable graphitic precursors, and in the high temperature zone (greater than 2000 K) polymer scission results in formation of short polymer chains/molecules. Simulations performed in the high temperature zone on the phenolic resin composites (with carbon nanotubes and carbon fibers) shows that the presence of interfaces had no substantial effect on the chain scission rate or the activation energy value for water formation.

  5. Single-walled carbon nanotube networks in conductive composite materials.

    PubMed

    Bârsan, Oana A; Hoffmann, Günter G; van der Ven, Leo G J; de With, G Bert

    2014-01-01

    Electrically conductive composite materials can be used for a wide range of applications because they combine the advantages of a specific polymeric material (e.g., thermal and mechanical properties) with the electrical properties of conductive filler particles. However, the overall electrical behaviour of these composite materials is usually much below the potential of the conductive fillers, mainly because by mixing two different components, new interfaces and interphases are created, changing the properties and behaviours of both. Our goal is to characterize and understand the nature and influence of these interfaces on the electrical properties of composite materials. We have improved a technique based on the use of sodium carboxymethyl cellulose (CMC) to disperse single-walled carbon nanotubes (SWCNTs) in water, followed by coating glass substrates, and drying and removing the CMC with a nitric acid treatment. We used electron microscopy and atomic force microscopy techniques to characterize the SWCNT films, and developed an in situ resistance measurement technique to analyse the influence of both the individual components and the mixture of an epoxy/amine system on the electrical behaviour of the SWCNTs. The results showed that impregnating a SWCNT network with a polymer is not the only factor that affects the film resistance; air exposure, temperature, physical and chemical properties of the individual polymer components, and also the formation of a polymeric network, can all have an influence on the macroscopic electrical properties of the initial SWCNT network. These results emphasize the importance of understanding the effects that each of the components can have on each other before trying to prepare an efficient polymer composite material. PMID:25430670

  6. Dynamic materials evaluation by confined plasma ablation and laser-generated shocks

    NASA Astrophysics Data System (ADS)

    Paisley, Dennis L.; Swift, D. C.; Forsman, A. C.; Kyrala, George A.; Johnson, Randall P.; Kopp, Roger A.; Hauer, Allan A.; Wark, Justin S.; Loveridge, A.; Allen, A. M.; Kalantar, Daniel H.

    2000-08-01

    Laser-generated shocks can and have been used to study their effects on single crystal materials during shock compression. While a crystal undergoes shock compression and release, the transient x- ray diffraction (TXD) of the Bragg and Laue signals is indicative of the change in the crystal lattice spacing. The lattice spacing directly relates to the strain in the crystal. From the dynamic lattice data, strain, strain rate, and/or phase change in a material may be determined. Confined ablation plasmas can efficiently launch a flyer plate for direct impact on a target material imparting a well-characterized shock input and generate kilobar to megabar pressure pulses over a wide range of pulse duration (= 20 ns). The laser-launched flyer plates are analogous to those launched by gas guns, but the smaller size provides an experimental method not easily accessible by larger gas gun experiments. With lasers, diagnostic equipment can be easily synchronized to study dynamic material parameters, i.e., single crystal shock dynamics, interfacial bond strengths of thin coatings, grain-interfaces, texture, and high strain rates (106 - 109 sec-1).

  7. Improved model for the angular dependence of excimer laser ablation rates in polymer materials

    SciTech Connect

    Pedder, J. E. A.; Holmes, A. S.; Dyer, P. E.

    2009-10-26

    Measurements of the angle-dependent ablation rates of polymers that have applications in microdevice fabrication are reported. A simple model based on Beer's law, including plume absorption, is shown to give good agreement with the experimental findings for polycarbonate and SU8, ablated using the 193 and 248 nm excimer lasers, respectively. The modeling forms a useful tool for designing masks needed to fabricate complex surface relief by ablation.

  8. Ablation processing of biomedical materials by ultrashort laser pulse ranging from 50 fs through 2 ps

    NASA Astrophysics Data System (ADS)

    Ozono, Kazue; Obara, Minoru; Sakuma, Jun

    2003-06-01

    In recent years, femtosecond laser processing of human hard/soft tissues has been studied. Here, we have demonstrated ablation etching of hydroxyapatite. Hydroxyapatite (Ca10(PO4)6(OH)2) is a key component of human tooth and human bone. The human bone is mainly made of hydroxyapatite oriented along the collagen. The micromachining of hydroxyapatite is highly required for orthopedics and dentistry. The important issue is to preserve the chemical property of the ablated surface. If chemical properties of hydroxyapatite change once, the human bone or tooth cannot grow again after laser processing. As for nanosecond laser ablation (for example excimer laser ablation), the relative content of calcium and phosphorus in (Ca10(PO4)6(OH)2) is found to change after laser ablation. We used here pulsewidth tunable output from 50 fs through 2 ps at 820 nm and 1 kpps. We measured calcium spectrum and phosphorus spectrum of the ablated surface of hydroxyapatite by XPS. As a result, the chemical content of calcium and phosphorus is kept unchanged before and after 50-fs - 2-ps laser ablation. We also demonstrated ablation processing of human tooth with Ti:sapphire laser, and precise ablation processing and microstructure fabrication are realized.

  9. Evaulation of B{sub 4}C as an ablator material for NIF capsules. Revision 1

    SciTech Connect

    Burnham, A.K.; Alford, C.S.; Makowiecki, D.M.; Dittrich, T.R.; Wallace, R.J.; Honea, E.C.; King, C.M.; Steinman, D.

    1997-03-26

    Boron carbide (B{sub 4}C) is examined as a potential fuel container and ablator for implosion capsules on the National Ignition Facility (NIF). A capsule of pure B{sub 4}C encasing a layer of solid DT implodes stably and ignites with anticipated NIF x-ray drives, producing 18 MJ of energy. Thin films of B{sub 4}C were found to be resistant to oxidation and modestly transmitting in the infrared (IR), possibly enabling IR fuel characterization and enhancement for thin permeation barriers but not for full-thickness capsules. Polystyrene mandrels 0.5 mm in diameter were successfully coated with 0.15-2.0 micrometers of B{sub 4}C. Thickness estimated from optical density agreed well with those measured by scanning electron microscopy (SEM). The B{sub 4}C microstructure was columnar but finer than for Be made at the same conditions. B{sub 4}C is a very strong material, with a fiber tensile strength capable of holding NIF fill pressures at room temperature, but it is also very brittle, and microscopic flaws or grain structure may limit the noncryogenic fill pressure. Argon (Ar) permeation rates were measured for a few capsules that had been further coated with 5 micrometers of plasma polymer. The B{sub 4}C coatings tended to crack under tensile load. Some shells filled more slowly than they leaked, suggesting that the cracks open and close under opposite pressure loading. As observed earlier for Ti coatings, 0.15-micrometer layers of B{sub 4}C had better gas retention properties than 2-micrometer layers, possibly because of fewer cracks. Permeation and fill strength issues for capsules with a full ablator thickness of B{sub 4}C are unresolved. 21 refs., 6 figs.

  10. Classification of plastic materials by imaging laser-induced ablation plumes

    NASA Astrophysics Data System (ADS)

    Negre, Erwan; Motto-Ros, Vincent; Pelascini, Frederic; Yu, Jin

    2016-08-01

    A method of rapid classification and identification of plastic materials has been studied in this work. Such method is based on fast spectroscopic imagery of laser-induced ablation plume on plastics to be analyzed. More specifically, a classification schema has been developed first according to the nature of the CC bonds which characterize the polymer matrix. Our results show that the spatial distribution and the evolution of the molecular species in the ablation plume, such as C2 and CN, exhibit clear different behaviors for polymers without any native CC bond, with CC single bonds or with CC double bonds respectively. Therefore the morphological parameters of the populations of the molecular species extracted from the time-resolved spectroscopic images of the plumes provide efficient indicators to classify the polymers characterized by the above mentioned different kinds of CC bonds. When dealing with different polymers with the same kind of CC bond, CC single bond for instance, other indicators should be introduced to provide the further discrimination. Such indicators can be for example a specific native molecular bond other than CC bonds, CN for example, the total emission intensity of which may exhibit specific time evolution. The robustness of the developed classification schema has been then studied with respect to two of the most frequently used additives in plastics fabrication, graphite and titanium. Our results show a negligible influence of these additives in the morphology of the populations of the molecular species when such additives are mixed into the polymer matrix with the percentages usually used in plastics productions, which demonstrates the validity of the developed classification schema for plastics.

  11. Micromachining of optically transparent materials by laser ablation of a solution containing pyrene

    NASA Astrophysics Data System (ADS)

    Yabe, Akira; Niino, Hiroyuki; Wang, Jun

    2001-01-01

    Optically transparent materials such as fused silica, quartz crystal, calcium fluoride, and fluorocarbon polymer were etched upon irradiation of organic solution containing pyrene with a conventional KrF or XeCl excimer laser. Threshold fluences for etching were 240 mJ/cm2 for fused silica, 330 mJ/cm2 for quartz crystal, 740 mJ/cm2 for calcium fluoride, and 45 mJ/cm2 for fluorocarbon polymer. These threshold values were remarkably low compared with those of direct ablation by using conventional lasers. Their etch rates remarkably depended on a concentration of pyrene: the etch rate became higher as the pyrene concentration increased. It means that pyrene molecules play an important role in this process. The mechanisms for this process is discussed by cyclic multiphotonic absorption of pyrene in the excited states, thermal relaxation, and formation of super-heated solution. As the results suggest, the process is based on the combination of two physical processes in the interface between the transparent materials and the liquid: one is a heating process by a super-heated liquid and the other is an attacking process by a high temperature and pressure vapor. The mechanism is also referred to thermal properties of materials.

  12. Femtosecond pulse laser ablation of metallic, semiconducting, ceramic, and biological materials

    NASA Astrophysics Data System (ADS)

    Kautek, Wolfgang; Krueger, Joerg

    1994-09-01

    Production of holes and grooves of < 30 micrometers diameter with high aspect ratio value is a delicate task either for mechanical tools, or for conventional nanosecond pulse lasers like e.g. pulsed Nd:YAG or excimer lasers. They later tend to cause microcracks extending from an annular melting zone, or substantial disruption, respectively. Experimental results are presented which demonstrate that the development of intense ultrashort pulse laser systems (>> 1012 W cm-2, (tau) < 1 ps) opens up possibilities for materials processing by cold plasma generation and ablation of metals, semiconductors, ceramics, composites, and biological materials. A femtosecond and a nanosecond dye laser with pulse durations of 300 fs (< 200 (mu) J) and 7 ns (< 10 mJ), and center wavelengths at 612 and 600 nm, respectively, both focused on an area of the order of 10-5 cm2, have been applied either to absorbing substrates, like polycrystalline gold, silicon (111), aluminum nitride ceramics, or transparent materials, like synthetic and human dental hydroxyapatite composites, bone material, and human cornea transplants. The fs-laser generates its own absorption in transparent materials by a multiphoton absorption process, and thus forces the absorption of visible radiation. Because the time is too short (< ps) for significant transport of mass and energy, the beam interaction generally results in the formation of a thin plasma layer of approximately solid state density. Only after the end of the subpicosecond laser pulse, it expands rapidly away from the surface without any light absorption and further plasma heating. Therefore, energy transfer (heat and impulse) to the target material, and thermal and mechanical disruption are minimized. In contrast to heat- affected zones (HAZ's) generated by conventional nanosecond pulse lasers of the order of 1 - 10 micrometers , HAZ's of less than 0.02 micrometers were observed.

  13. Laser-ablation processes

    SciTech Connect

    Dingus, R.S.

    1992-01-01

    The various mechanisms by which ablation of materials can be induced with lasers are discussed in this paper. The various ablation processes and potential applications are reviewed from the threshold for ablation up to fluxes of about 10{sup 13} W/cm{sup 2}, with emphasis on three particular processes; namely, front-surface spallation, two-dimensional blowoff, and contained vaporization.

  14. Development and Analysis of Synthetic Composite Materials Emulating Patient AAA Wall Material Properties

    NASA Astrophysics Data System (ADS)

    Margossian, Christa M.

    Abdominal Aortic Aneurysm (AAA) rupture accounts for 14,000 deaths a year in the United States. Since the number of ruptures has not decreased significantly in recent years despite improvements in imaging and surgical procedures, there is a need for an accurate, noninvasive technique capable of establishing rupture risk for specific patients and discriminating lesions at high risk. In this project, synthetic composite materials replicating patient-specific wall stiffness and strength were developed and their material properties evaluated. Composites utilizing various fibers were developed to give a range of stiffness from 1825.75 kPa up through 8187.64 kPa with one base material, Sylgard 170. A range of strength from 631.12 kPa to 1083 kPa with the same base material was also found. By evaluating various base materials and various reinforcing fibers, a catalogue of stiffnesses and strengths was started to allow for adaptation to specific patient properties. Three specific patient properties were well-matched with two composites fabricated: silk thread-reinforced Sylgard 170 and silk thread-reinforced Dragon Skin 20. The composites showed similar stiffnesses to the specific patients while reaching target stresses at particular strains. Not all patients were matched with composites as of yet, but recommendations for future matches are able to be determined. These composites will allow for the future evaluation of flow-induced wall stresses in models replicating patient material properties and geometries.

  15. Material Strength Effects on Feedthru of the Ablative Richtmyer-Meshkov Instability

    NASA Astrophysics Data System (ADS)

    Loomis, Eric; Peralta, Pedro; Fortin, Elizabeth; Lynch, Jenna

    2015-11-01

    Mitigating hydrodynamic instabilities in Inertial Confinement Fusion (ICF) is of prime importance for producing self-heating and reaching ignition. One possible mitigation strategy involves the use of metal ablators (e.g., Be) that remain solid following passage of the first shock. Finite material strength in these capsules would alter the feedthru characteristics (oscillation frequency and decay rate) of perturbations initially on the outer surface. To study the physics associated with material strength effects on rippled shock oscillations and feedthru, experiments were performed at the Los Alamos Trident laser. These experiments directly measured the surface height amplitude imprinted by the shock ripple at the opposite free surface with 20 nm precision over a timespan of 25 ns using an in-situ diagnostic called Transient Imaging Displacement Interferometry (TIDI). Simulations from the Lawrence Livermore National Lab code HYDRA predicted that the free surface ripple grows about 3 times more without the use of a strength model in Cu for an initial 5 micron amplitude, 50 micron wavelength sinusoid driven to a free surface velocity of 600 m/s. By increasing the perturbation wavelength we slowed the shock oscillation frequency and decay rate to increase the free surface ripple amplitude to roughly half the perturbations initial amplitude. The time dependent imprinted amplitude was considerably less in high strength Fe versus the softer Cu. This research made possible by a grant from the Office of Fusion Energy Sciences - High Energy Density Laboratory Plasmas.

  16. The kinetics of reaction of the by-products of ablative materials at high temperatures and the rate of heat transfer between hot surfaces and reactive gases

    NASA Technical Reports Server (NTRS)

    Spokes, G. N.; Beadle, P. C.; Gac, N. A.; Golden, D. M.; King, K. D.; Benson, S. W.

    1971-01-01

    Research has been conducted by means of laboratory experiments to enhance understanding of the fundamental mechanisms of heterogeneous and homogeneous chemical reactions taking place during ablative processes that accompany the reentry or manned space vehicles into planetary atmospheres. Fundamental mechanisms of those chemical reactions believed to be important in the thermal degradation of ablative plastic heat shield materials, and the gases evolved, are described.

  17. Performance of a Light-Weight Ablative Thermal Protection Material for the Stardust Mission Sample Return Capsule

    NASA Technical Reports Server (NTRS)

    Covington, M. A.

    2005-01-01

    New tests and analyses are reported that were carried out to resolve testing uncertainties in the original development and qualification of a lightweight ablative material used for the Stardust spacecraft forebody heat shield. These additional arcjet tests and analyses confirmed the ablative and thermal performance of low density Phenolic Impregnated Carbon Ablator (PICA) material used for the Stardust design. Testing was done under conditions that simulate the peak convective heating conditions (1200 W/cm2 and 0.5 atm) expected during Earth entry of the Stardust Sample Return Capsule. Test data and predictions from an ablative material response computer code for the in-depth temperatures were compared to guide iterative adjustment of material thermophysical properties used in the code so that the measured and predicted temperatures agreed. The PICA recession rates and maximum internal temperatures were satisfactorily predicted by the computer code with the revised properties. Predicted recession rates were also in acceptable agreement with measured rates for heating conditions 37% greater than the nominal peak heating rate of 1200 W/sq cm. The measured in-depth temperature response data show consistent temperature rise deviations that may be caused by an undocumented endothermic process within the PICA material that is not accurately modeled by the computer code. Predictions of the Stardust heat shield performance based on the present evaluation provide evidence that the maximum adhesive bondline temperature will be much lower than the maximum allowable of 250 C and an earlier design prediction. The re-evaluation also suggests that even with a 25 percent increase in peak heating rates, the total recession of the heat shield would be a small fraction of the as-designed thickness. These results give confidence in the Stardust heat shield design and confirm the potential of PICA material for use in new planetary probe and sample return applications.

  18. 1-D Transient Thermal Modeling of an Ablative Material (MCC-1) Exposed to a Simulated Convective Titan 4 Launch Environment

    NASA Technical Reports Server (NTRS)

    Reinarts, Thomas R.; Crain, William K.; Stuckey, C. Irvin; Palko, Richard L.

    1998-01-01

    The purpose of the work is to demonstrate that the flat test panel substrate temperatures are consistent with analysis predictions for MCC-1 applied to a aluminum substrate. The testing was performed in an aerothermal facility on samples of three different thicknesses of MCC-1 on an aluminum substrate. The results of the test were compared with a Transient Thermal model. The key assumptions of the Transient Thermal model were: (1) a one-dimensional heat transfer; (2) a constant ablation recession rate (determined from pre and post-test measurements); (3) ablation temperature of 540 degrees F; (4) Char left behind the ablation front; and (5) temperature jump correction for incident heat transfer coefficient. Two methods were used to model the heating of bare MCC-1: (1) Directly input surface temperature as a function of time; and (2) Aerothermal heating using calibration plate data and subtracting the radiation losses to tunnel walls. The results are presented as graphs. This article is presented in Viewgraph format.

  19. X-ray ablation rates in inertial confinement fusion capsule materials

    NASA Astrophysics Data System (ADS)

    Olson, R. E.; Rochau, G. A.; Landen, O. L.; Leeper, R. J.

    2011-03-01

    X-ray ablation rates have been measured in beryllium, copper-doped beryllium, germanium-doped plastic (Ge-doped CH), and diamondlike high density carbon (HDC) for radiation temperatures T in the range of 160-260 eV. In beryllium, the measured ablation rates range from 3 to 12 mg/cm2/ns; in Ge-doped CH, the ablation rates range from 2 to 6 mg/cm2/ns; and for HDC, the rates range from 2 to 9 mg/cm2/ns. The ablation rates follow an approximate T3 dependence and, for T below 230 eV, the beryllium ablation rates are significantly higher than HDC and Ge-doped CH. The corresponding implied ablation pressures are in the range of 20-160 Mbar, scaling as T3.5. The results are found to be well predicted by computational simulations using the physics packages and computational techniques employed in the design of indirect-drive inertial confinement fusion capsules. An iterative rocket model has been developed and used to compare the ablation rate data set to spherical indirect-drive capsule implosion experiments and to confirm the validity of some aspects of proposed full-scale National Ignition Facility ignition capsule designs.

  20. Experimental measurement of ablation rate of wood pieces, undergoing fast pyrolysis by contact with a heated wall

    SciTech Connect

    Lede, J.; Panagopoulos, J.; Villermaux, J.

    1983-01-01

    The conventional pyrolysis of biomass yields about equal amounts of gases, char and tar. When pyrolysis is carried out in severe heating conditions, the reaction products can be almost entirely gaseous and contain significant amounts of light unsaturated hydrocarbons. Authors involved in such research, generally recommend several types of conditions: small wood particles, high temperatures, high heating rates, high heat fluxes, etc. Few of them have associated the idea of ablation regime, to the observation of the fast pyrolysis reaction. Actually, the apparent rate of reaction is a function of two competitive processes within the wood particle: the rate of heat transfer and the rate of chemical decomposition of wood itself. If chemical processes are very fast, the heat transfer is rate controlling: this is the so called ablation regime characterized by a thin superficial layer of reacting wood). Such a regime can be represented by the rate at which the reacting layer moves towards the cold unreacted core of the piece of wood (ablation rate v) and the thickness of this reacting layer (e).

  1. 29 CFR 1926.856 - Removal of walls, floors, and material with equipment.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 29 Labor 8 2012-07-01 2012-07-01 false Removal of walls, floors, and material with equipment. 1926.856 Section 1926.856 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH....856 Removal of walls, floors, and material with equipment. (a) Mechanical equipment shall not be...

  2. 29 CFR 1926.856 - Removal of walls, floors, and material with equipment.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 8 2011-07-01 2011-07-01 false Removal of walls, floors, and material with equipment. 1926.856 Section 1926.856 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH....856 Removal of walls, floors, and material with equipment. (a) Mechanical equipment shall not be...

  3. 29 CFR 1926.856 - Removal of walls, floors, and material with equipment.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ....856 Removal of walls, floors, and material with equipment. (a) Mechanical equipment shall not be used on floors or working surfaces unless such floors or surfaces are of sufficient strength to support... 29 Labor 8 2013-07-01 2013-07-01 false Removal of walls, floors, and material with equipment....

  4. 29 CFR 1926.856 - Removal of walls, floors, and material with equipment.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ....856 Removal of walls, floors, and material with equipment. (a) Mechanical equipment shall not be used on floors or working surfaces unless such floors or surfaces are of sufficient strength to support... 29 Labor 8 2010-07-01 2010-07-01 false Removal of walls, floors, and material with equipment....

  5. 29 CFR 1926.856 - Removal of walls, floors, and material with equipment.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ....856 Removal of walls, floors, and material with equipment. (a) Mechanical equipment shall not be used on floors or working surfaces unless such floors or surfaces are of sufficient strength to support... 29 Labor 8 2014-07-01 2014-07-01 false Removal of walls, floors, and material with equipment....

  6. Dissociation along the principal Hugoniot of the Laser Mégajoule ablator material.

    PubMed

    Colin-Lalu, P; Recoules, V; Salin, G; Plisson, T; Brambrink, E; Vinci, T; Bolis, R; Huser, G

    2016-08-01

    Glow discharge polymer hydrocarbon (GDP-CH) is used as the ablator material in inertial confinement fusion (ICF) capsules for the Laser Mégajoule and National Ignition Facility. Due to its fabrication process, GDP-CH chemical composition and structure differ from commercially available plastics and detailed knowledge of its properties in the warm dense matter regime is needed to achieve accurate design of ICF capsules. First-principles ab initio simulations of the GDP-CH principal Hugoniot up to 8 Mbar were performed using the quantum molecular dynamics (QMD) code abinit and showed that atomic bond dissociation has an effect on the compressibility. Results from these simulations are used to parametrize a quantum semiempirical model in order to generate a tabulated equation of state that includes dissociation. Hugoniot measurements obtained from an experiment conducted at the LULI2000 laser facility confirm QMD simulations as well as EOS modeling. We conclude by showing the EOS model influence on shock timing in a hydrodynamic simulation. PMID:27627404

  7. Multiphysics design optimization model for structural walls incorporating phase-change materials

    NASA Astrophysics Data System (ADS)

    Stockwell, A.; Neithalath, N.; Rajan, S. D.

    2015-03-01

    The development of energy-efficient building envelopes has been an ongoing effort in many countries owing to the pressing need to achieve energy independence. In this study numerical optimization techniques and finite element analysis provide the means to find a compromise point between adding phase-change materials (PCMs) to a concrete wall, the energy savings and the wall's structural capacity. The primary objective is to minimize the overall lifetime cost of a wall by understanding the implications of PCM layer thickness, material properties and position in the wall on the overall energy consumption. While it is difficult to manually configure a typical wall for the lowest total cost, the developed computational framework provides an automated tool for searching for the best design. The results show that successful designs can be obtained where material and energy costs can be minimized through a judicious combination of existing building materials with thermal energy storage materials.

  8. ECO-WALL SYSTEMS: USING RECYCLED MATERIAL IN THE DESIGN OF COMMERCIAL INTERIOR WALL SYSTEMS FOR BUILDINGS

    EPA Science Inventory

    This proposal describes an interdisciplinary project involving students from several academic departments at Miami University in the design of commercial wall systems to be manufactured from recycled materials. The goal of Phase I of the project is to develop and conduct prelimi...

  9. Laser ablation plasmas for diagnostics of structured electronic and optical materials during or after laser processing

    NASA Astrophysics Data System (ADS)

    Russo, Richard E.; Bol'shakov, Alexander A.; Yoo, Jong H.; González, Jhanis J.

    2012-03-01

    Laser induced plasma can be used for rapid optical diagnostics of electronic, optical, electro-optical, electromechanical and other structures. Plasma monitoring and diagnostics can be realized during laser processing in real time by means of measuring optical emission that originates from the pulsed laser-material interaction. In post-process applications, e.g., quality assurance and quality control, surface raster scanning and depth profiling can be realized with high spatial resolution (~10 nm in depth and ~3 μm lateral). Commercial instruments based on laser induced breakdown spectrometry (LIBS) are available for these purposes. Since only a laser beam comes in direct contact with the sample, such diagnostics are sterile and non-disruptive, and can be performed at a distance, e.g. through a window. The technique enables rapid micro-localized chemical analysis without a need for sample preparation, dissolution or evacuation of samples, thus it is particularly beneficial in fabrication of thin films and structures, such as electronic, photovoltaic and electro-optical devices or circuits of devices. Spectrum acquisition from a single laser shot provides detection limits for metal traces of ~10 μg/g, which can be further improved by accumulating signal from multiple laser pulses. LIBS detection limit for Br in polyethylene is 90 μg/g using 50-shot spectral accumulation (halogen detection is a requirement for semiconductor package materials). Three to four orders of magnitude lower detection limits can be obtained with a femtosecond laser ablation - inductively coupled plasma mass spectrometer (LA-ICP-MS), which is also provided on commercial basis. Laser repetition rate is currently up to 20 Hz in LIBS instruments and up to 100 kHz in LA-ICP-MS.

  10. Basic ablation phenomena during laser thrombolysis

    NASA Astrophysics Data System (ADS)

    Sathyam, Ujwal S.; Shearin, Alan; Prahl, Scott A.

    1997-05-01

    This paper presents studies of microsecond ablation phenomena that take place during laser thrombolysis. The main goals were to optimize laser parameters for efficient ablation, and to investigate the ablation mechanism. Gelatin containing an absorbing dye was used as the clot model. A parametric study was performed to identify the optimal wavelength, spot size, pulse energies, and repetition rate for maximum material removal. The minimum radiant exposures to achieve ablation at any wavelength were measured. The results suggest that most visible wavelengths were equally efficient at removing material at radiant exposures above threshold. Ablation was initiated at surface temperatures just above 100 degrees Celsius. A vapor bubble was formed during ablation. Less than 5% of the total pulse energy is coupled into the bubble energy. A large part of the delivered energy is unaccounted for and is likely released partly as acoustic transients from the vapor expansion and partly wasted as heat. The current laser and delivery systems may not be able to completely remove large clot burden that is sometimes encountered in heart attacks. However, laser thrombolysis may emerge as a favored treatment for strokes where the occlusion is generally smaller and rapid recanalization is of paramount importance. A final hypothesis is that laser thrombolysis should be done at radiant exposures close to threshold to minimize any damaging effects of the bubble dynamics on the vessel wall.

  11. Structural characterization of macroscopic single-walled carbon nanotube materials

    NASA Astrophysics Data System (ADS)

    Zhou, Wei

    In this thesis, we studied the structural properties of macroscopic materials of single-walled carbon nanotubes (SWNTs) in the form of fibers, films and suspensions. We characterized the preferred orientations in partially aligned SWNT fibers and films, combining x-ray fiber diagram and polarized Raman scattering. Our texture model consists of an aligned fraction, characterized by the angular distribution width of tube axes, plus a completely unaligned fraction. For neat fibers extruded from SWNT/superacid suspensions through a small orifice, the distribution width and the aligned fraction both improve with decreasing orifice diameter. For magnetic field-aligned SWNT films deposited from surfactant suspensions, the aligning effects of deposition and external magnetic field force in the film plane are additive, the out-of-plane mosaic being narrower than the in-plane one. SWNTs dispersed in superacid or aqueous surfactant solutions are precursors for many applications. In oleum, SWNTs can be charged and protonated by H 2SO4 molecules. X-ray scattering indicates that H2SO 4 molecules align along nanotube axes to form cylindrical shells wrapped around nanotubes. This finding establishes the validity of a long-standing important but still debated physical chemistry concept, "structured solvent shells surrounding dissolved ions". Differential scanning calorimetry confirms that the partly ordered H2SO4 molecules are a new phase, with distinct freezing/melting behavior. X-ray scattering at low temperature further shows that crystallization of the bulk-like acid surrounding the structured shells is templated by the SWNTs. The specific orientation of the acid crystallites provides solid evidence for direct protonation of SWNT. We studied the morphologies of SWNT suspensions using small-angle neutron scattering. We observed rigid rod behavior from SWNTs dispersed in water using sodium dodecylbenzene sulfonate surfactant, suggesting that SWNTs exist mainly as individual tube

  12. Automated in situ trace element analysis of silicate materials by laser ablation inductively coupled plasma mass spectrometry.

    PubMed

    Chen, Z; Canil, D; Longerich, H P

    2000-09-01

    This paper describes the automated in situ trace element analysis of solid materials by laser ablation (LA) inductively coupled plasma mass spectrometry (ICP-MS). A compact computer-controlled solid state Nd:YAG Merchantek EO UV laser ablation (LA) system has been coupled with the high sensitivity VG PQII S ICP-MS. A two-directional communication was interfaced in-house between the ICP-MS and the LA via serial RS-232 port. Each LA-ICP-MS analysis at a defined point includes a 60 s pre-ablation delay, a 60 s ablation, and a 90 s flush delay. The execution of each defined time setting by LA was corresponding to the ICP-MS data acquisition allowing samples to be run in automated cycle sequences like solution auto-sampler ICP-MS analysis. Each analytical cycle consists of four standards, one control reference material, and 15 samples, and requires about 70 min. Data produced by Time Resolved Analysis (TRA) from ICP-MS were later reduced off-line by in-house written software. Twenty-two trace elements from four reference materials (NIST SRM 613, and fused glass chips of BCR-2, SY-4, and G-2) were determined by the automated LA-ICP-MS method. NIST SRM 610 or NIST SRM 613 was used as an external calibration standard, and Ca as an internal standard to correct for drift, differences in transport efficiency and sampling yield. Except for Zr and Hf in G-2, relative standard deviations for all other elements are less than 10%. Results compare well with the data reported from literature with average limits of detection from 1 ng x g(-1) to 455 ng x g(-1) and less than 100 ng x g(-1) for most trace elements. PMID:11220835

  13. Ablation of breast cancer cells using trastuzumab-functionalized multi-walled carbon nanotubes and trastuzumab-diphtheria toxin conjugate.

    PubMed

    Oraki Kohshour, Mojtaba; Mirzaie, Sako; Zeinali, Majid; Amin, Mansour; Said Hakhamaneshi, Mohammad; Jalili, Ali; Mosaveri, Nader; Jamalan, Mostafa

    2014-03-01

    Trastuzumab (Herceptin(®) ) is a monoclonal antibody (mAb) for specific ablation of HER2-overexpressing malignant breast cancer cells. Intensification of antiproliferative activity of trastuzumab through construction of immunotoxins and nano-immunoconjugates is a promising approach for treatment of cancer. In this study, trastuzumab was directly conjugated to diphtheria toxin (DT). Also, conjugates of trastuzumab and multiwalled carbon nanotubes (MWCNT) were constructed by covalent immobilization of trastuzumab onto MWCNTs. Then, antiproliferative activity of the fusion constructs against HER2-overexpressing SK-BR-3 and also HER2-negative MCF-7 cancer cell lines were examined. Cells treated with trastuzumab-MWCNT conjugates were irradiated with near-infrared (NIR) light. Efficient absorption of NIR radiation and its conversion to heat by MWCNTs can be resulted to thermal ablation of cancerous cells. Our results strongly showed that both trastuzumab-MWCNT and trastuzumab-DT conjugates were significantly efficient in the specific killing of SK-BR-3 cells. Targeting of MWCNTs to cancerous cells using trastuzumab followed by exposure of cells to NIR radiation was more efficient in repression of cell proliferation than treatment for cancer cells with trastuzumab-DT. Our results also showed that conjugation linkers can significantly affect the cytotoxicity of MWCNT-immunoconjugates. In conclusion, our data demonstrated that trastuzumab-MWCNT is a promising nano-immunoconjugate for killing of HER2-overexpressing cancerous cells. PMID:24118702

  14. Thermal response and ablation characteristics of lightweight ceramic ablators

    SciTech Connect

    Tran, H.K.; Rasky, D.J.; Esfahani, L.

    1994-11-01

    This paper presents the thermal performance and ablation characteristics of the newly developed lightweight ceramic ablators (LCAs) in a supersonic, high-enthalpy convective environment. Lightweight ceramic ablators were recently conceived and developed at NASA Ames using low-density ceramic or carbon fibrous matrices as substrates for main structural support and organic resins as fillers. These LCAs were successfully produced with densities ranging from approximately 0.224 to 1.282 g/cu cm. Several infiltrants with different char yields were used to study the effect on surface recession. Tests were conducted in the NASA Ames arc-jet facilities. Material thermal performance was evaluated at cold-wall heat fluxes from 113.5 to 1634 W/sq cm, and stagnation pressures of 0.018 to 0.331 atm. Conventional ablators such as SLA-561, Avcoat 5026-39HC, MA-25S, and balsa wood were tested at the same heat fluxes for direct comparison. Surface temperature was measured using optical pyrometers, and the recession rates were obtained from the high-speed films. In-depth temperature data were obtained to determine the thermal penetration depths and conductivity. Preliminary results indicated that most LCAs performed comparably to or better than conventional ablators. At low flux levels (less than 454 W/sq cm), the addition of silicon carbide and polymethyl methacrylate significantly improved the ablation performance of silica substrates. The carbon-based LCAs were the most mass-efficient at high flux levels (greater than 454 W/sq cm). 16 refs.

  15. High-resolution chemical depth profiling of solid material using a miniature laser ablation/ionization mass spectrometer.

    PubMed

    Grimaudo, Valentine; Moreno-García, Pavel; Riedo, Andreas; Neuland, Maike B; Tulej, Marek; Broekmann, Peter; Wurz, Peter

    2015-02-17

    High-resolution chemical depth profiling measurements of copper films are presented. The 10 μm thick copper test samples were electrodeposited on a Si-supported Cu seed under galvanostatic conditions in the presence of particular plating additives (SPS, Imep, PEI, and PAG) used in the semiconductor industry for the on-chip metallization of interconnects. To probe the trend of these plating additives toward inclusion into the deposit upon growth, quantitative elemental mass spectrometric measurements at trace level concentration were conducted by using a sensitive miniature laser ablation ionization mass spectrometer (LIMS), originally designed and developed for in situ space exploration. An ultrashort pulsed laser system (τ ∼ 190 fs, λ = 775 nm) was used for ablation and ionization of sample material. We show that with our LIMS system, quantitative chemical mass spectrometric analysis with an ablation rate at the subnanometer level per single laser shot can be conducted. The measurement capabilities of our instrument, including the high vertical depth resolution coupled with high detection sensitivity of ∼10 ppb, high dynamic range ≥10(8), measurement accuracy and precision, is of considerable interest in various fields of application, where investigations with high lateral and vertical resolution of the chemical composition of solid materials are required, these include, e.g., wafers from semiconductor industry or studies on space weathered samples in space research. PMID:25642789

  16. Evidence for substitutional boron in doped single-walled carbon nanotubes

    SciTech Connect

    Ayala, P.; Pichler, T.; Reppert, J.; Rao, A. M.; Grobosch, M.; Knupfer, M.

    2010-05-03

    Precise determination of acceptors in the laser ablation grown B doped single-walled carbon nanotubes (SWCNTs) has been elusive. Photoemission spectroscopy finds evidence for subpercent substitutional B in this material, which leads to superconductivity in thin film SWNT samples.

  17. Investigation of the particle size distribution of the ejected material generated during the single femtosecond laser pulse ablation of aluminium

    NASA Astrophysics Data System (ADS)

    Wu, Han; Zhang, Nan; Zhu, Xiaonong

    2014-10-01

    Single femtosecond laser pulses are employed to ablate an aluminium target in vacuum, and the particle size distribution of the ablated material deposited on a mica substrate is examined with atomic force microscopy (AFM). The recorded AFM images show that these particles have a mean radius of several tens of nanometres. It is also determined that the mean radius of these deposited nanoparticles increases when the laser fluence at the aluminium target increases from 0.44 J/cm2 to 0.63 J/cm2. The mechanism of the laser-induced nanoparticle generation is thought to be photomechanical tensile stress relaxation. Raman spectroscopy measurements confirm that the nanoparticles thus produced have the same structure as the bulk aluminium.

  18. Radial Movement of Pellet Ablation Material in Tokamaks Due to the Grad-B Effect

    NASA Astrophysics Data System (ADS)

    Parks, P. B.; Sessions, W.; Ventrice, C. A.; Baylor, L. R.

    1998-11-01

    The mass source from a pellet represents a significant disturbance to the plasma. Initially the ablated substance is a highly localized, high-beta (>1) plasmoid, which will polarize and drift towards the low field side of the tokamak. Propagation of shear Alfvén waves brakes the outward motion,(P.B. Parks, Nucl. Fusion 32), 2137 (1992). much like its role as a restoring force in the ballooning mode. The grad-B drift drive will weaken because of pressure relaxation as the ablated substance spreads out along the field lines. The ablation blob will stop before it becomes assimilated into the plasma. An analytic model was developed to predict the stopping distance, i.e., the outward large-R shift for radial, vertical, and inside launch locations. Comparison of the model with experiments on TFTR, JET, DIII--D, and a 3D MHD simulation(H. Strauss, Int. Sherwood Fusion Theory Conf. 1998.) will be presented.

  19. First wall and blanket module safety enhancement by material selection and design decision

    SciTech Connect

    Merrill, B.J.

    1980-01-01

    A thermal/mechanical study has been performed which illustrates the behavior of a fusion reactor first wall and blanket module during a loss of coolant flow event. The relative safety advantages of various material and design options were determined. A generalized first wall-blanket concept was developed to provide the flexibility to vary the structural material (stainless steel vs titanium), coolant (helium vs water), and breeder material (liquid lithium vs solid lithium aluminate). In addition, independent vs common first wall-blanket cooling and coupled adjacent module cooling design options were included in the study. The comparative analyses were performed using a modified thermal analysis code to handle phase change problems.

  20. Summary of SLAC's SEY Measurement On Flat Accelerator Wall Materials

    SciTech Connect

    Le Pimpec, F.; /PSI, Villigen /SLAC

    2007-06-08

    The electron cloud effect (ECE) causes beam instabilities in accelerator structures with intense positively charged bunched beams. Reduction of the secondary electron yield (SEY) of the beam pipe inner wall is effective in controlling cloud formation. We summarize SEY results obtained from flat TiN, TiZrV and Al surfaces carried out in a laboratory environment. SEY was measured after thermal conditioning, as well as after low energy, less than 300 eV, particle exposure.

  1. Modeling and response analysis of thin-walled beam structures constructed of advanced composite materials

    SciTech Connect

    Song, O.

    1990-01-01

    Thin-walled beam structures are adopted as structural members in various fields of modern technology including aeronautical/aerospacial, naval, mechanical and civil ones. With the advent of advanced composite material systems, there is a vital need to reformulate the classical theory of thin-walled beams in a wide framework. In this dissertation, the aeroelastic divergence instability of aircraft wings modeled as thin-walled beams as well as the eigenfrequency problem of cantilevered composite thin-walled beams of closed cross-section are considered in the framework of a refined theory incorporating non-classical effects.

  2. Production of microstructures in wide-band-gap and organic materials using pulsed laser ablation at 157 nm wavelength

    NASA Astrophysics Data System (ADS)

    Haehnel, Falk; Bertram, Rene; Reisse, Guenter; Boettcher, Rene; Weissmantel, Steffen

    2010-11-01

    New results on three-dimensional microstructuring of fused silica, sapphire, calcium fluoride, magnesium fluoride, and PTFE using pulsed laser ablation at 157 nm wavelength are presented. A largely automated high-precision fluorine laser micromachining station was used for the investigations. In some fundamental investigations, threshold fluences of 0.9 J/cm2 for fused silica, 0.6 J/cm2 for sapphire, 1.7 J/cm2 for calcium fluoride, and of 0.05 J/cm2 for PTFE have been determined. The ablation rates at 3 J/cm2 fluence were 60 to 100 nm/pulse for the inorganic insulators and 450 nm/pulse for PTFE. In the second part of the paper, it is shown that on the basis of the knowledge of the ablation rates and the laser beam parameters, bores of a few µm size and complex 3D microstructures with a variety of geometries can be produced in the surface of these materials. Thereby, no cracking occurs if proper parameters are used.

  3. Interaction of graphite and ablative materials with CO2-laser, carbon-arc, and xenon-arc radiation. M.S. Thesis - George Washington Univ., Washington, D. C.

    NASA Technical Reports Server (NTRS)

    Brewer, W. D.

    1975-01-01

    The behavior of graphite and several charring ablators in a variety of high radiative heat flux environments was studied in various radiative environments produced by a CO2 laser and a carbon arc facility. Graphite was also tested in xenon arc radiation. Tests were conducted in air nitrogen, helium, and a mixture of CO2 and nitrogen, simulating the Venus atmosphere. The experimental results are compared with theoretical results obtained with a one dimensional charring ablator analysis and a two dimensional subliming ablator analysis. Photomicroscopy showed no significant differences in appearance or microstructure of the charring ablators or graphite after testing in the three different facilities, indicating that the materials respond fundamentally the same to the radiation of different frequencies. The performance of phenolic nylon and graphite was satisfactorily predicted with existing analyses and published material property data.

  4. INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Comparative study of the ablation of materials by femtosecond and pico- or nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Kononenko, Taras V.; Konov, Vitalii I.; Garnov, Sergei V.; Danielius, R.; Piskarskas, A.; Tamosauskas, G.; Dausinger, F.

    1999-08-01

    A series of studies was carried out on the ablation of steel, Si3N4 ceramic, and diamond in air by femtosecond (200 and 900 fs) pulses of different wavelengths (532 and 266 nm) and in a wide energy density range (1 — 103 J cm-2 ). The ablation rates were measured for different geometries of the irradiation surface [a shallow crater and a channel with a high (up to 10) aspect ratio]. The ablation rates (in a shallow crater) and the morphologies of the irradiated surface were compared for femtosecond and longer (220 ps, 7 ns) pulses. The role of the laser-generated plasma in the ablation of materials by subpicosecond pulses as well as the prospects for the practical application of ultrashort laser pulses in the processing of materials are analysed.

  5. Recognition of wall materials through active thermography coupled with numerical simulations.

    PubMed

    Pietrarca, Francesca; Mameli, Mauro; Filippeschi, Sauro; Fantozzi, Fabio

    2016-09-01

    In the framework of historical buildings, wall thickness as well as wall constituents are not often known a priori, and active IR thermography can be exploited as a nonintrusive method for detecting what kind of material lies beneath the external plaster layer. In the present work, the wall of a historical building is subjected to a heating stimulus, and the surface temperature temporal trend is recorded by an IR camera. A hybrid numerical model is developed in order to simulate the transient thermal response of a wall made of different known materials underneath the plaster layer. When the numerical thermal contrast and the appearance time match with the experimental thermal images, the material underneath the plaster can be qualitatively identified. PMID:27607254

  6. Fluorescent single walled nanotube/silica composite materials

    DOEpatents

    Dattelbaum, Andrew M.; Gupta, Gautam; Duque, Juan G.; Doorn, Stephen K.; Hamilton, Christopher E.; DeFriend Obrey, Kimberly A.

    2013-03-12

    Fluorescent composites of surfactant-wrapped single-walled carbon nanotubes (SWNTs) were prepared by exposing suspensions of surfactant-wrapped carbon nanotubes to tetramethylorthosilicate (TMOS) vapor. Sodium deoxycholate (DOC) and sodium dodecylsulphate (SDS) were the surfactants. No loss in emission intensity was observed when the suspension of DOC-wrapped SWNTs were exposed to the TMOS vapors, but about a 50% decrease in the emission signal was observed from the SDS-wrapped SWNTs nanotubes. The decrease in emission was minimal by buffering the SDS/SWNT suspension prior to forming the composite. Fluorescent xerogels were prepared by adding glycerol to the SWNT suspensions prior to TMOS vapor exposure, followed by drying the gels. Fluorescent aerogels were prepared by replacing water in the gels with methanol and then exposing them to supercritical fluid drying conditions. The aerogels can be used for gas sensing.

  7. Femtosecond laser ablation properties of transparent materials: impact of the laser process parameters on the machining throughput

    NASA Astrophysics Data System (ADS)

    Matylitsky, V. V.; Hendricks, F.; Aus der Au, J.

    2013-03-01

    High average power, high repetition rate femtosecond lasers with μJ pulse energies are increasingly used for bio-medical and material processing applications. With the introduction of femtosecond laser systems such as the SpiritTM platform developed by High Q Lasers and Spectra-Physics, micro-processing of solid targets with femtosecond laser pulses have obtained new perspectives for industrial applications [1]. The unique advantage of material processing with subpicosecond lasers is efficient, fast and localized energy deposition, which leads to high ablation efficiency and accuracy in nearly all kinds of solid materials. The study on the impact of the laser processing parameters on the removal rate for transparent substrate using femtosecond laser pulses will be presented. In particular, examples of micro-processing of poly-L-lactic acid (PLLA) - bio-degradable polyester and XensationTM glass (Schott) machined with SpiritTM ultrafast laser will be shown.

  8. Multiple exciton generation induced enhancement of the photoresponse of pulsed-laser-ablation synthesized single-wall-carbon-nanotube/PbS-quantum-dots nanohybrids.

    PubMed

    Ka, Ibrahima; Le Borgne, Vincent; Fujisawa, Kazunori; Hayashi, Takuya; Kim, Yoong Ahm; Endo, Morinobu; Ma, Dongling; El Khakani, My Ali

    2016-01-01

    The pulsed laser deposition method was used to decorate appropriately single wall carbon nanotubes (SWCNTs) with PbS quantum dots (QDs), leading to the formation of a novel class of SWCNTs/PbS-QDs nanohybrids (NHs), without resorting to any ligand engineering and/or surface functionalization. The number of laser ablation pulses (NLp) was used to control the average size of the PbS-QDs and their coverage on the SWCNTs' surface. Photoconductive (PC) devices fabricated from these SWCNTs/PbS-QDs NHs have shown a significantly enhanced photoresponse, which is found to be PbS-QD size dependent. Wavelength-resolved photocurrent measurements revealed a strong photoconductivity of the NHs in the UV-visible region, which is shown to be due to multiple exciton generation (MEG) in the PbS-QDs. For the 6.5 nm-diameter PbS-QDs (with a bandgap (Eg) = 0.86 eV), the MEG contribution of the NHs based PC devices was shown to lead to a normalized internal quantum efficiency in excess of 300% for photon energies ≥4.5Eg. While the lowest MEG threshold in our NHs based PC devices is found to be of ~2.5Eg, the MEG efficiency reaches values as high as 0.9 ± 0.1. PMID:26830452

  9. Multiple exciton generation induced enhancement of the photoresponse of pulsed-laser-ablation synthesized single-wall-carbon-nanotube/PbS-quantum-dots nanohybrids

    NASA Astrophysics Data System (ADS)

    Ka, Ibrahima; Le Borgne, Vincent; Fujisawa, Kazunori; Hayashi, Takuya; Kim, Yoong Ahm; Endo, Morinobu; Ma, Dongling; El Khakani, My Ali

    2016-02-01

    The pulsed laser deposition method was used to decorate appropriately single wall carbon nanotubes (SWCNTs) with PbS quantum dots (QDs), leading to the formation of a novel class of SWCNTs/PbS-QDs nanohybrids (NHs), without resorting to any ligand engineering and/or surface functionalization. The number of laser ablation pulses (NLp) was used to control the average size of the PbS-QDs and their coverage on the SWCNTs’ surface. Photoconductive (PC) devices fabricated from these SWCNTs/PbS-QDs NHs have shown a significantly enhanced photoresponse, which is found to be PbS-QD size dependent. Wavelength-resolved photocurrent measurements revealed a strong photoconductivity of the NHs in the UV-visible region, which is shown to be due to multiple exciton generation (MEG) in the PbS-QDs. For the 6.5 nm-diameter PbS-QDs (with a bandgap (Eg) = 0.86 eV), the MEG contribution of the NHs based PC devices was shown to lead to a normalized internal quantum efficiency in excess of 300% for photon energies ≥4.5Eg. While the lowest MEG threshold in our NHs based PC devices is found to be of ~2.5Eg, the MEG efficiency reaches values as high as 0.9 ± 0.1.

  10. Multiple exciton generation induced enhancement of the photoresponse of pulsed-laser-ablation synthesized single-wall-carbon-nanotube/PbS-quantum-dots nanohybrids

    PubMed Central

    Ka, Ibrahima; Le Borgne, Vincent; Fujisawa, Kazunori; Hayashi, Takuya; Kim, Yoong Ahm; Endo, Morinobu; Ma, Dongling; El Khakani, My Ali

    2016-01-01

    The pulsed laser deposition method was used to decorate appropriately single wall carbon nanotubes (SWCNTs) with PbS quantum dots (QDs), leading to the formation of a novel class of SWCNTs/PbS-QDs nanohybrids (NHs), without resorting to any ligand engineering and/or surface functionalization. The number of laser ablation pulses (NLp) was used to control the average size of the PbS-QDs and their coverage on the SWCNTs’ surface. Photoconductive (PC) devices fabricated from these SWCNTs/PbS-QDs NHs have shown a significantly enhanced photoresponse, which is found to be PbS-QD size dependent. Wavelength-resolved photocurrent measurements revealed a strong photoconductivity of the NHs in the UV-visible region, which is shown to be due to multiple exciton generation (MEG) in the PbS-QDs. For the 6.5 nm-diameter PbS-QDs (with a bandgap (Eg) = 0.86 eV), the MEG contribution of the NHs based PC devices was shown to lead to a normalized internal quantum efficiency in excess of 300% for photon energies ≥4.5Eg. While the lowest MEG threshold in our NHs based PC devices is found to be of ~2.5Eg, the MEG efficiency reaches values as high as 0.9 ± 0.1. PMID:26830452

  11. Multiple target laser ablation system

    DOEpatents

    Mashburn, Douglas N.

    1996-01-01

    A laser ablation apparatus and method are provided in which multiple targets consisting of material to be ablated are mounted on a movable support. The material transfer rate is determined for each target material, and these rates are stored in a controller. A position detector determines which target material is in a position to be ablated, and then the controller controls the beam trigger timing and energy level to achieve a desired proportion of each constituent material in the resulting film.

  12. Multiple target laser ablation system

    DOEpatents

    Mashburn, D.N.

    1996-01-09

    A laser ablation apparatus and method are provided in which multiple targets consisting of material to be ablated are mounted on a movable support. The material transfer rate is determined for each target material, and these rates are stored in a controller. A position detector determines which target material is in a position to be ablated, and then the controller controls the beam trigger timing and energy level to achieve a desired proportion of each constituent material in the resulting film. 3 figs.

  13. Characterization and field emission properties of multi-walled carbon nanotubes with fine crystallinity prepared by CO2 laser ablation

    NASA Astrophysics Data System (ADS)

    Yuge, Ryota; Toyama, Kiyohiko; Ichihashi, Toshinari; Ohkawa, Tetsuya; Aoki, Yasushi; Manako, Takashi

    2012-07-01

    Multi-walled carbon nanotubes (MWNTs) were synthesized by irradiating of a CO2 laser in continuous wave mode onto a boron-containing graphite target at room temperature. The pressure of Ar atmosphere was controlled in 50, 150, 400, or 760 Torr. The diameter of obtained MWNTs was in the range of 5-40 nm. The quantity and degree of graphitization of synthesized MWNTs increased with the Ar gas pressure. A large quantity of MWNTs with fine crystalline structure has been synthesized preferentially at the condition of 760 Torr. The MWNTs with the fine crystalinity indicated highly oxidative stability in O2. We also found that a large area field emission device with MWNT cathodes indicated good β value of 3.6 × 104 cm-1, and sufficient reliability for long term operations over 150 h, suggesting promising application to field emission devices.

  14. Wall-collision line broadening of molecular oxygen within nanoporous materials

    SciTech Connect

    Xu, Can T.; Lewander, Maerta; Andersson-Engels, Stefan; Svensson, Tomas; Svanberg, Sune; Adolfsson, Erik

    2011-10-15

    Wall-collision broadening of near-infrared absorption lines of molecular oxygen confined in nanoporous zirconia is studied by employing high-resolution diode-laser spectroscopy. The broadening is studied for pores of different sizes under a range of pressures, providing new insights on how wall collisions and intermolecular collisions influence the total spectroscopic line profile. The pressure series show that wall-collision broadening is relatively more prominent under reduced pressures, enabling sensitive means to probe pore sizes of porous materials. In addition, we show that the total wall-collision-broadened profile strongly deviates from a Voigt profile and that wall-collision broadening exhibits an additive-like behavior to the pressure and Doppler broadening.

  15. Synergistic enhancement of cancer therapy using a combination of docetaxel and photothermal ablation induced by single-walled carbon nanotubes

    PubMed Central

    Wang, Lei; Zhang, Mingyue; Zhang, Nan; Shi, Jinjin; Zhang, Hongling; Li, Min; Lu, Chao; Zhang, Zhenzhong

    2011-01-01

    Background Single-walled carbon nanotubes (SWNT) are poorly soluble in water, so their applications are limited. Therefore, aqueous solutions of SWNT, designed by noncovalent functionalization and without toxicity, are required for biomedical applications. Methods In this study, we conjugated docetaxel with SWNT via π-π accumulation and used a surfactant to functionalize SWNT noncovalently. The SWNT were then conjugated with docetaxel (DTX-SWNT) and linked with NGR (Asn-Gly-Arg) peptide, which targets tumor angiogenesis, to obtain a water-soluble and tumor-targeting SWNT-NGR-DTX drug delivery system. Results SWNT-NGR-DTX showed higher efficacy than docetaxel in suppressing tumor growth in a cultured PC3 cell line in vitro and in a murine S180 cancer model. Tumor volumes in the S180 mouse model decreased considerably under near-infrared radiation compared with the control group. Conclusion The SWNT-NGR-DTX drug delivery system may be promising for high treatment efficacy with minimal side effects in future cancer therapy. PMID:22114495

  16. Materials compatibility and wall stresses in hydride storage beds

    SciTech Connect

    Clark, E.A.; Dunn, K.A.; McKillip, S.T.; Bannister, C.E.

    1991-01-01

    Hydrogen isotope handling and storage will be accomplished using solid-state hydride compounds at the Savannah River Site in the new Replacement Tritium Facility (RTF). The hydride powder is contained in a horizontal cylindrical vessel, and the combination of hydride powder, vessel, and associated heating and cooling facilities are termed in a hydride storage bed. The materials compatibility of the storage powder with the stainless steel vessel has been examined, and the stresses developed in the vessel due to expansion of the powder by absorbing hydrogen have been measured.

  17. Materials compatibility and wall stresses in hydride storage beds

    SciTech Connect

    Clark, E.A.; Dunn, K.A.; McKillip, S.T.; Bannister, C.E.

    1991-12-31

    Hydrogen isotope handling and storage will be accomplished using solid-state hydride compounds at the Savannah River Site in the new Replacement Tritium Facility (RTF). The hydride powder is contained in a horizontal cylindrical vessel, and the combination of hydride powder, vessel, and associated heating and cooling facilities are termed in a hydride storage bed. The materials compatibility of the storage powder with the stainless steel vessel has been examined, and the stresses developed in the vessel due to expansion of the powder by absorbing hydrogen have been measured.

  18. Textured coatings as first-wall materials : exposure to energetic ions on RHEPP-1.

    SciTech Connect

    Williams, Brian E.; Renk, Timothy Jerome

    2010-11-01

    The level of energy deposition on future inertial fusion energy (IFE) reactor first walls, particularly in direct-drive scenarios, makes the ultimate survivability of such wall materials a challenge. We investigate the survivability of three-dimensional (3-D) dendritic materials fabricated by chemical vapor deposition (CVD), and exposed to repeated intense helium beam pulses on the RHEPP-1 facility at Sandia National Laboratories. Prior exposures of flat materials have led to what appears to be unacceptable mass loss on timescales insufficient for economical reactor operation. Two potential advantages of such dendritic materials are (a) increased effective surface area, resulting in lowered fluences to most of the wall material surface, and (b) improvement in materials properties for such micro-engineered metals compared to bulk processing. Several dendritic fabrications made with either tungsten and tungsten with rhenium show little or no morphology change after up to 800 pulses of 1 MeV helium at reactor-level thermal wall loading. Since the rhenium is added in a thin surface layer, its use does not appear to raise environmental concerns for fusion designs.

  19. A Study of Ablation-Flowfield Coupling Relevant to the Orion Heatshield

    NASA Technical Reports Server (NTRS)

    Johnston, Christopher O.; Gnoffo, Peter A.; Mazaheri, Alireza

    2009-01-01

    The coupled interaction between an ablating surface and the surrounding aerothermal environment is studied. An equilibrium ablation model is coupled to the LAURA flowfield solver, which allows the char ablation rate (m-dot(sub c)) to be computed as part of the flowfield solution. The wall temperature (T(sub w)) and pyrolysis ablation rate (m-dot(sub g)) may be specified by the user, obtained from the steady-state ablation approximation, or computed from a a material response code. A 32 species thermochemical nonequilibrium flowfield model is applied, which permits the treatment of C, H, O, N, and Si containing species. Coupled ablation cases relevant to the Orion heatshield are studied. These consist of diffusion-limited oxidation cases with Avcoat as the ablation material. The m-dot(sub c) values predicted from the developed coupled ablation analysis were compared with those obtained from a typical uncoupled ablation analysis. The coupled results were found to be as much as 50% greater than the uncoupled values. This is shown to be a result of the cumulative effect of the two fundamental approximations inherent in the uncoupled analysis.

  20. Excimer laser ablation of ferrites

    NASA Astrophysics Data System (ADS)

    Tam, A. C.; Leung, W. P.; Krajnovich, D.

    1991-02-01

    Laser etching of ferrites was previously done by scanning a focused continuous-wave laser beam on a ferrite sample in a chemical environment. We study the phenomenon of photo-ablation of Ni-Zn or Mn-Zn ferrites by pulsed 248-nm KrF excimer laser irradiation. A transfer lens system is used to project a grating pattern of a mask irradiated by the pulsed KrF laser onto the ferrite sample. The threshold fluence for ablation at the ferrite surface is about 0.3 J/cm2. A typical fluence of 1 J/cm2 is used. The etched grooves produced are typically 20-50 μm wide, with depths achieved as deep as 70 μm . Groove straightness is good as long as a sharp image is projected onto the sample surface. The wall angle is steeper than 60 degrees. Scanning electron microscopy of the etched area shows a ``glassy'' skin with extensive microcracks and solidified droplets being ejected that is frozen in action. We found that this skin can be entirely removed by ultrasonic cleaning. A fairly efficient etching rate of about 10 nm/pulse for a patterned area of about 2 mm×2 mm is obtained at a fluence of 1 J/cm2. This study shows that projection excimer laser ablation is useful for micromachining of ferrite ceramics, and indicates that a hydrodynamic sputtering mechanism involving droplet emission is a cause of material removal.

  1. Transient Ablation of Teflon Hemispheres

    NASA Technical Reports Server (NTRS)

    Arai, Norio; Karashima, Kei-ichi; Sato, Kiyoshi

    1997-01-01

    For high-speed entry of space vehicles into atmospheric environments, ablation is a practical method for alleviating severe aerodynamic heating. Several studies have been undertaken on steady or quasi-steady ablation. However, ablation is a very complicated phenomenon in which a nonequilibrium chemical process is associated with an aerodynamic process that involves changes in body shape with time. Therefore, it seems realistic to consider that ablation is an unsteady phenomenon. In the design of an ablative heat-shield system, since the ultimate purpose of the heat shield is to keep the internal temperature of the space vehicle at a safe level during entry, the transient heat conduction characteristics of the ablator may be critical in the selection of the material and its thickness. This note presents an experimental study of transient ablation of Teflon, with particular emphasis on the change in body shape, the instantaneous internal temperature distribution, and the effect of thermal expansion on ablation rate.

  2. Mineralogical determination in situ of a highly heterogeneous material using a miniaturized laser ablation mass spectrometer with high spatial resolution

    NASA Astrophysics Data System (ADS)

    Neubeck, Anna; Tulej, Marek; Ivarsson, Magnus; Broman, Curt; Riedo, Andreas; McMahon, Sean; Wurz, Peter; Bengtson, Stefan

    2016-04-01

    Techniques enabling in situ elemental and mineralogical analysis on extraterrestrial planets are strongly required for upcoming missions and are being continuously developed. There is ample need for quantitative and high-sensitivity analysis of elemental as well as isotopic composition of heterogeneous materials. Here we present in situ spatial and depth elemental profiles of a heterogeneous rock sample on a depth-scale of nanometres using a miniaturized laser ablation mass spectrometer (LMS) designed for planetary space missions. We show that the LMS spectra alone could provide highly detailed compositional, three-dimensional information and oxidation properties of a natural, heterogeneous rock sample. We also show that a combination of the LMS and Raman spectroscopy provide comprehensive mineralogical details of the investigated sample. These findings are of great importance for future space missions where quick, in situ determination of the mineralogy could play a role in the process of selecting a suitable spot for drilling.

  3. Depolarization of D-T plasmas by recycling in material walls

    SciTech Connect

    Greenside, H.S.; Budny, R.V.; Post, D.E.

    1984-02-01

    The feasibility of using polarized deuterium (D) and tritium (T) plasmas in fusion reactors may be seriously affected by recycling in material walls. Theoretical and experimental results are reviewed which show how the depolarization rates of absorbed D and T depend on first wall parameters such as the temperature, the bulk and surface diffusivities, the density of electronic states at the Fermi surface, the spectral density of microscopic fluctuating electric field gradients, and the concentration of paramagnetic impurities. Nuclear magnetic resonance (NMR) spectroscopy of hydrogenated and deuterated amorphous semiconductors suggests that low-Z nonmetallic materials may provide a satisfactory first wall or limiter coating under reactor conditions with characteristic depolarization times of several seconds. Experiments are proposed to test the consequences of our analysis.

  4. NMR study of domain wall pinning in a magnetically ordered material

    NASA Astrophysics Data System (ADS)

    Pleshakov, I. V.; Popov, P. S.; Kuz'min, Yu. I.; Dudkin, V. I.

    2016-01-01

    The use of nuclear magnetic resonance in the form of spin echo in combination with magnetic field pulses applied to a magnetically ordered material sample offers a convenient tool for studying characteristics of the centers of domain-wall pinning. Possibilities of this method have been demonstrated in experiments with lithium-zinc ferrite.

  5. Laser ablation and high precision patterning of biomaterials and intraocular lenses

    NASA Astrophysics Data System (ADS)

    Serafetinides, A. A.; Spyratou, E.; Makropoulou, M.

    2010-10-01

    The use of intraocular lenses (IOL) is the most promising method for restoring excellent vision in cataract surgery. In addition, multifocal intraocular lenses for good distant and near vision are investigated. Several new materials, techniques and patterns are studied for the formation and etching of intraocular lenses in order to improve their optical properties and reduce the diffractive aberrations. As pulsed laser ablation is well established as a universal tool for surface processing of organic polymer materials, this study was focused in using laser ablation with short and ultra short laser pulses for surface modification of PMMA and intraocular lenses, instead of using other conventional techniques. The main advantage of using very short laser pulses, e.g. of ns, ps or fs duration, is that heat diffusion into the polymer material is negligible. As a result high precision patterning of the sample, without thermal damage of the surroundings, becomes possible. In this study, laser ablation was performed using commercially available hydrophobic acrylic IOLs, hydrophilic acrylic IOLs, and PMMA IOLs, with various diopters. We investigated the ablation efficiency and the phenomenology of the etched patterns by testing the ablation rate, versus laser energy fluence, at several wavelengths and the surface modification with atomic force microscopy (AFM), or scanning electron microscopy (SEM). The irradiated polymers have different optical properties, at the applied wavelengths, and therefore, present different ablation behaviour and morphology of the laser ablated crater walls and surrounding surfaces. The experimental results, some theoretical assumptions for mathematical modeling of the relevant ablation mechanisms are discussed.

  6. Micromechanics of the equine hoof wall: optimizing crack control and material stiffness through modulation of the properties of keratin.

    PubMed

    Kasapi, M A; Gosline, J M

    1999-02-01

    Small-scale components of the equine hoof wall were tested to determine their mechanical roles in the morphological hierarchy. Macroscale tensile tests conducted on samples of the inner wall tubules and intertubular material showed a sixfold difference in mean initial stiffnesses (0.47 and 0.08 GPa, respectively), indicating that the inner wall tubules stiffen the wall along its longitudinal axis. The similarity in material properties of tubule and intertubular samples from the mid-wall suggests that tubules in this region offer only minor reinforcement along the longitudinal axis. Microscale tests conducted on rows of keratin strands from the inner wall tubules and intertubular material, and on intertubular keratin strands of the mid-wall, produced estimates of the stiffnesses of the hydrated matrix (0.03 GPa) and intermediate filament (IF; 3-4 GPa) components of the nanoscale ( &agr; -keratin) composite. The results from these tests also suggest that the properties of the keratin composite vary through the wall thickness. Birefringence measurements on inner wall and mid-wall regions agree with these observations and suggest that, although the keratin IF volume fraction is locally constant, the volume fraction changes through the thickness of the wall. These findings imply that modulation of the hoof wall properties has been achieved by varying the IF volume fraction, countering the effects of specific IF alignments which serve another function and would otherwise adversely affect the modulus of a particular region. PMID:9914146

  7. High-gravity-assisted pulsed laser ablation system for the fabrication of functionally graded material thin film.

    PubMed

    Nishiyama, T; Morinaga, S; Nagayama, K

    2009-03-01

    This paper describes a novel method for the fabrication of a thin film deposited on an appropriate substrate having a continuous composition gradient. The composition gradient was achieved by a combination of pulsed laser ablation (PLA) of the target material with a very strong acceleration field generated on a moving disk rotating at a very high speed. The PLA process was used to produce a cloud of high-energy particles of the target material that will be deposited on a substrate placed on the rotating disk. After deposition, the particles will diffuse on the surface of the thin film under a strong acceleration field. The high energy of the particles and their diffusion on the substrate surface in a high-vacuum environment produces a macroscopic composition distribution in the thin film. We have constructed an experimental apparatus consisting of a vacuum chamber in which a circular disk made of titanium is driven by a high-frequency inductive motor. An acceleration field of up to 10,000 G can be generated by this apparatus. Functionally graded material thin films of FeSi(2) with a continuous concentration gradient were successfully fabricated by this method under a gravity field of 5400 G. A significant advantage of this method is that it allows us to fabricate graded thin films with a very smooth surface covered by few droplets. PMID:19334931

  8. Systematic conversion of single walled carbon nanotubes into n-type thermoelectric materials by molecular dopants.

    PubMed

    Nonoguchi, Yoshiyuki; Ohashi, Kenji; Kanazawa, Rui; Ashiba, Koji; Hata, Kenji; Nakagawa, Tetsuya; Adachi, Chihaya; Tanase, Tomoaki; Kawai, Tsuyoshi

    2013-01-01

    Thermoelectrics is a challenging issue for modern and future energy conversion and recovery technology. Carbon nanotubes are promising active thermoelectic materials owing to their narrow bandgap energy and high charge carrier mobility, and they can be integrated into flexible thermoelectrics that can recover any waste heat. We here report air-stable n-type single walled carbon nanotubes with a variety of weak electron donors in the range of HOMO level between ca. -4.4 eV and ca. -5.6 eV, in which partial uphill electron injection from the dopant to the conduction band of single walled carbon nanotubes is dominant. We display flexible films of the doped single walled carbon nanotubes possessing significantly large thermoelectric effect, which is applicable to flexible ambient thermoelectric modules. PMID:24276090

  9. Microencapsulation of canola oil by lentil protein isolate-based wall materials.

    PubMed

    Chang, C; Varankovich, N; Nickerson, M T

    2016-12-01

    The overall goal was to encapsulate canola oil using a mixture of lentil protein isolate and maltodextrin with/without lecithin and/or sodium alginate by spray drying. Initially, emulsion and microcapsule properties as a function of oil (20%-30%), protein (2%-8%) and maltodextrin concentration (9.5%-18%) were characterized by emulsion stability, droplet size, viscosity, surface oil and entrapment efficiency. Microcapsules with 20% oil, 2% protein and 18% maltodextrin were shown to have the highest entrapment efficiency, and selected for further re-design using different preparation conditions and wall ingredients (lentil protein isolate, maltodextrin, lecithin and/or sodium alginate). The combination of the lentil protein, maltodextrin and sodium alginate represented the best wall material to produce microcapsules with the highest entrapment efficiency (∼88%). The lentil protein-maltodextrin-alginate microcapsules showed better oxidative stability and had a stronger wall structure than the lentil protein-maltodextrin microcapsules. PMID:27374532

  10. TPS Ablator Technologies for Interplanetary Spacecraft

    NASA Technical Reports Server (NTRS)

    Curry, Donald M.

    2004-01-01

    This slide presentation reviews the status of Thermal Protection System (TPS) Ablator technologies and the preparation for use in interplanetary spacecraft. NASA does not have adequate TPS ablatives and sufficient selection for planned missions. It includes a comparison of shuttle and interplanetary TPS requirements, the status of mainline TPS charring ablator materials, a summary of JSC SBIR accomplishments in developing advanced charring ablators and the benefits of SBIR Ablator/fabrication technology.

  11. On-line double isotope dilution laser ablation inductively coupled plasma mass spectrometry for the quantitative analysis of solid materials.

    PubMed

    Fernández, Beatriz; Rodríguez-González, Pablo; García Alonso, J Ignacio; Malherbe, Julien; García-Fonseca, Sergio; Pereiro, Rosario; Sanz-Medel, Alfredo

    2014-12-01

    We report on the determination of trace elements in solid samples by the combination of on-line double isotope dilution and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The proposed method requires the sequential analysis of the sample and a certified natural abundance standard by on-line IDMS using the same isotopically-enriched spike solution. In this way, the mass fraction of the analyte in the sample can be directly referred to the certified standard so the previous characterization of the spike solution is not required. To validate the procedure, Sr, Rb and Pb were determined in certified reference materials with different matrices, including silicate glasses (SRM 610, 612 and 614) and powdered samples (PACS-2, SRM 2710a, SRM 1944, SRM 2702 and SRM 2780). The analysis of powdered samples was carried out both by the preparation of pressed pellets and by lithium borate fusion. Experimental results for the analysis of powdered samples were in agreement with the certified values for all materials. Relative standard deviations in the range of 6-21% for pressed pellets and 3-21% for fused solids were obtained from n=3 independent measurements. Minimal sample preparation, data treatment and consumption of the isotopically-enriched isotopes are the main advantages of the method over previously reported approaches. PMID:25440666

  12. Tungsten carbide precursors as an example for influence of a binder on the particle formation in the nanosecond laser ablation of powdered materials.

    PubMed

    Holá, Markéta; Mikuska, Pavel; Hanzlíková, Renáta; Kaiser, Jozef; Kanický, Viktor

    2010-03-15

    A study of LA-ICP-MS analysis of pressed powdered tungsten carbide precursors was performed to show the advantages and problems of nanosecond laser ablation of matrix-unified samples. Five samples with different compositions were pressed into pellets both with silver powder as a binder serving to keep the matrix unified, and without any binder. The laser ablation was performed by nanosecond Nd:YAG laser working at 213 nm. The particle formation during ablation of both sets of pellets was studied using an optical aerosol spectrometer allowing the measurement of particle concentration in two size ranges (10-250 nm and 0.25-17 microm) and particle size distribution in the range of 0.25-17 microm. Additionally, the structure of the laser-generated particles was studied after their collection on a filter using a scanning electron microscope (SEM) and the particle chemical composition was determined by an energy dispersive X-ray spectroscope (EDS). The matrix effect was proved to be reduced using the same silver powdered binder for pellet preparation in the case of the laser ablation of powdered materials. The LA-ICP-MS signal dependence on the element content present in the material showed an improved correlation for Co, Ti, Ta and Nb of the matrix-unified samples compared to the non-matrix-unified pellets. In the case of W, the ICP-MS signal of matrix-unified pellets was influenced by the changes in the particle formation. PMID:20152424

  13. Thermal performance and radio-frequency transmissivity of candidate ablation materials for S-band antenna window application on manned spacecraft

    NASA Technical Reports Server (NTRS)

    Tillian, D. J.; Cubley, H. D.

    1970-01-01

    A test program was conducted in the MSC 1.5 MW arc-heated facility to evaluate the thermal performance of ablation materials having potential application as radio frequency windows. These tests were conducted for the improvement of omnidirectional antenna operating characteristics during atmospheric reentry. Since a full scale model of the Apollo command service module was available for antenna tests, this mockup was used as a basic for the tests. Test models were subjected to heating conditions simulating the nominal lunar return trajectory (AS-501) and the design trajectories, high heat load and high heating rate. RF measurements were made before and after the arc jet tests to measure attenuation effects due to the thermal degradation of the materials under consideration. The test program demonstrated that additional development is required in materials technology to achieve an ablative system with both good RF transmission characteristics and thermal-structural integrity.

  14. Problems in obtaining precise and accurate Sr isotope analysis from geological materials using laser ablation MC-ICPMS

    PubMed Central

    van der Wagt, B.; Koornneef, J. M.; Davies, G. R.

    2007-01-01

    This paper reviews the problems encountered in eleven studies of Sr isotope analysis using laser ablation multicollector inductively coupled plasma mass spectrometry (LA-MC-ICPMS) in the period 1995–2006. This technique has been shown to have great potential, but the accuracy and precision are limited by: (1) large instrumental mass discrimination, (2) laser-induced isotopic and elemental fractionations and (3) molecular interferences. The most important isobaric interferences are Kr and Rb, whereas Ca dimer/argides and doubly charged rare earth elements (REE) are limited to sample materials which contain substantial amounts of these elements. With modern laser (193 nm) and MC-ICPMS equipment, minerals with >500 ppm Sr content can be analysed with a precision of better than 100 ppm and a spatial resolution (spot size) of approximately 100 μm. The LA MC-ICPMS analysis of 87Sr/86Sr of both carbonate material and plagioclase is successful in all reported studies, although the higher 84Sr/86Sr ratios do suggest in some cases an influence of Ca dimer and/or argides. High Rb/Sr (>0.01) materials have been successfully analysed by carefully measuring the 85Rb/87Rb in standard material and by applying the standard-sample bracketing method for accurate Rb corrections. However, published LA-MC-ICPMS data on clinopyroxene, apatite and sphene records differences when compared with 87Sr/86Sr measured by thermal ionisation mass spectrometry (TIMS) and solution MC-ICPMS. This suggests that further studies are required to ensure that the most optimal correction methods are applied for all isobaric interferences. PMID:18080118

  15. A comparison of prosthetic materials used to repair abdominal wall defects.

    PubMed

    Mori, N; Takano, K; Miyake, T; Nishio, T; Muto, S; Koshizuka, K; Nakagomi, H; Kubo, M; Tada, Y

    1998-09-01

    Large abdominal wall defects may require a prosthesis for closure. The aim of our study was to identify the best material for abdominoplasty in pediatric patients. One hundred twenty-eight Wistar KY strain male rats (3 weeks old) were used. All animals underwent celiotomy via a midline skin incision. They were divided into seven groups as follows: the animals in groups 1 through 6 underwent full-thickness abdominal wall excision 3 cm in diameter. The animals in group 1 underwent primary closure. In groups 2 through 6 the defect was closed with prosthetic material. In Group 7, a sham operation was performed. Daily weights were measured. The animals were killed after 3 and 9 weeks. Adhesion scores were assigned for each group. Vicryl mesh resulted in the fewest adhesions and had no effect on weight gain in the developing rats. PMID:9716675

  16. Effect of wall material on the antioxidant activity and physicochemical properties of Rubus fruticosus juice microcapsules.

    PubMed

    Díaz, Dafne I; Beristain, Cesar I; Azuara, Ebner; Luna, Guadalupe; Jimenez, Maribel

    2015-01-01

    Blackberry (Rubus fruticosus) juice possesses compounds with antioxidant activity, which can be protected by different biopolymers used in the microencapsulation. Therefore, the effects of cell wall material including maltodextrin (MD), Arabic gum (GA) and whey protein concentrate (WPC) were evaluated on the physicochemical and antioxidant properties of encapsulated blackberries using a spray-drying technique. Anthocyanin concentration, polymeric colour, total polyphenols, radical scavenging activity of the 1,1-diphenyl-2-picrilhydrazil radical, reducing power and the stability at different storage conditions were evaluated. GA and MD conferred a similar protection to the antioxidant compounds when the microcapsules were stored at low water activities (aw < 0.515) in contrast to at a high moisture content (aw > 0.902), whereas WPC presented a high protection. Therefore, the selection of the best wall material for blackberry juice encapsulation depends of the conditions of storage of the powder. PMID:26006741

  17. Simultaneous spatial and temporal focusing of femtosecond pulses: A new paradigm for material processing and tissue ablation

    NASA Astrophysics Data System (ADS)

    Block, Erica K.

    Femtosecond lasers are now prolific in many disciplines. While the mechanisms of femtosecond-material interactions are widely understood, femtosecond lasers as industrial and medical tools still have shortcomings. Currently conventional state of the art platforms are unable to support low numerical aperture (NA) beams (that provide large focal volumes and long working distances) without sacrificing axial precision. Furthermore inline (refractive) delivery systems that are necessary for industrial and clinical medical applications are currently hindered by nonlinear effects when delivering femtosecond pulses with tens of microJoule pulse energies and greater. In this thesis Simultaneous Space Time Focusing (SSTF) is presented as a new paradigm to move the field of femtosecond micromachining significantly forward. With this system we have delivered microjoule femtosecond pulses with low numerical aperture geometries (<0.05 NA) with characteristics that are significantly improved compared to standard focusing paradigms. Nonlinear effects that would normally result in focal plane shifts and focal spot distortion are mitigated when SSTF is employed. As a result, it is shown that SSTF will enable surgical implementations that are presently inhibited. Initial ablation experiments of ocular tissue show unprecedented performance with this technique. Implementation of SSTF, in the past, has been overly complicated. Multiple compressors and diffraction gratings resulted in low throughput efficiency. In the second part of this thesis we have focused on significantly streamlining the SSTF design into a flexible, single grating, integrated SSTF/chirped-pulse amplification system with an inline (refractive) delivery system to move towards industrial and clinical medical applications. For the first time this design also allows for variation of the beam aspect ratio of an SSTF beam, and thus the degree of pulse-front tilt at focus, while maintaining a net zero-dispersion system

  18. The Influence of SiC on the Ablation Response of Advanced Refractory Composite Materials

    NASA Technical Reports Server (NTRS)

    Bull, Jeffrey D.; Rasky, Daniel J. (Technical Monitor)

    1994-01-01

    In continuing our studies of advanced refractory composite materials we have recently completed an arc-jet test series of a diverse group of ceramics and ceramic matrix composites. The compositions range from continuous fiber reinforced ceramics to monoliths. Many of these materials contain SiC and one objective of this test series was to identify the influence of SiC oxidation mechanisms on material performance. Hence the arc heater was operated at two conditions; one in which the passive oxidation of SiC would be dominant and the other where the active oxidation of SiC would be dominant. It is shown here that the active oxidation mechanism of SiC does not dominate material performance when it is present at levels equal to or below 20 volume percent.

  19. Technique for Evaluating the Erosive Properties of Ablative Internal Insulation Materials

    NASA Technical Reports Server (NTRS)

    McComb, J. C.; Hitner, J. M.

    1989-01-01

    A technique for determining the average erosion rate versus Mach number of candidate internal insulation materials was developed for flight motor applications in 12 inch I.D. test firing hardware. The method involved the precision mounting of a mechanical measuring tool within a conical test cartridge fabricated from either a single insulation material or two non-identical materials each of which constituted one half of the test cartridge cone. Comparison of the internal radii measured at nine longitudinal locations and between eight to thirty two azimuths, depending on the regularity of the erosion pattern before and after test firing, permitted calculation of the average erosion rate and Mach number. Systematic criteria were established for identifying erosion anomalies such as the formation of localized ridges and for excluding such anomalies from the calculations. The method is discussed and results presented for several asbestos-free materials developed in-house for the internal motor case insulation in solid propellant rocket motors.

  20. Convergent ablator performance measurements

    SciTech Connect

    Hicks, D. G.; Spears, B. K.; Braun, D. G.; Sorce, C. M.; Celliers, P. M.; Collins, G. W.; Landen, O. L.; Olson, R. E.

    2010-10-15

    The velocity and remaining ablator mass of an imploding capsule are critical metrics for assessing the progress toward ignition of an inertially confined fusion experiment. These and other convergent ablator performance parameters have been measured using a single streaked x-ray radiograph. Traditional Abel inversion of such a radiograph is ill-posed since backlighter intensity profiles and x-ray attenuation by the ablated plasma are unknown. To address this we have developed a regularization technique which allows the ablator density profile {rho}(r) and effective backlighter profile I{sub 0}(y) at each time step to be uniquely determined subject to the constraints that {rho}(r) is localized in radius space and I{sub 0}(y) is delocalized in object space. Moments of {rho}(r) then provide the time-resolved areal density, mass, and average radius (and thus velocity) of the remaining ablator material. These results are combined in the spherical rocket model to determine the ablation pressure and mass ablation rate during the implosion. The technique has been validated on simulated radiographs of implosions at the National Ignition Facility [Miller et al., Nucl. Fusion 44, 228 (2004)] and implemented on experiments at the OMEGA laser facility [Boehly et al., Opt. Commun. 133, 495 (1997)].

  1. Convergent ablator performance measurements

    NASA Astrophysics Data System (ADS)

    Hicks, D. G.; Spears, B. K.; Braun, D. G.; Olson, R. E.; Sorce, C. M.; Celliers, P. M.; Collins, G. W.; Landen, O. L.

    2010-10-01

    The velocity and remaining ablator mass of an imploding capsule are critical metrics for assessing the progress toward ignition of an inertially confined fusion experiment. These and other convergent ablator performance parameters have been measured using a single streaked x-ray radiograph. Traditional Abel inversion of such a radiograph is ill-posed since backlighter intensity profiles and x-ray attenuation by the ablated plasma are unknown. To address this we have developed a regularization technique which allows the ablator density profile ρ(r ) and effective backlighter profile I0(y) at each time step to be uniquely determined subject to the constraints that ρ(r ) is localized in radius space and I0(y) is delocalized in object space. Moments of ρ(r ) then provide the time-resolved areal density, mass, and average radius (and thus velocity) of the remaining ablator material. These results are combined in the spherical rocket model to determine the ablation pressure and mass ablation rate during the implosion. The technique has been validated on simulated radiographs of implosions at the National Ignition Facility [Miller et al., Nucl. Fusion 44, 228 (2004)] and implemented on experiments at the OMEGA laser facility [Boehly et al., Opt. Commun. 133, 495 (1997)].

  2. Use of a compact fiber optic spectrometer for spectral feedback during the laser ablation of dental hard tissues and restorative materials

    NASA Astrophysics Data System (ADS)

    Cheng, Joyce Y.; Fan, Kenneth; Fried, Daniel

    2006-02-01

    One perceived disadvantage of caries removal using lasers is the loss of the tactile feedback associated with the handpiece. However, alternative methods of acoustic and optical feedback become available with the laser that can be exploited to provide information about the chemical composition of the material ablated, the ablation efficiency and rate, the depth of the incision, and the surface and plume temperature during ablation. Such information can be used to increase the selectivity of ablation, avoid peripheral thermal damage and excessive heat deposition in the tooth, and provide a mechanism of robotic automation. The objective of this study was to test the hypothesis that a compact fiberoptic spectrometer could be used to differentiate between the ablation of sound and carious enamel and dentin and between dental hard tissues and composite. Sound and carious tooth surfaces along with composite restorative materials were scanned with λ=0.355, 2.79 and 9.3 μm laser pulses at irradiation intensities ranging from 0.5-100 J/cm2 and spectra were acquired from λ=250-900-nm using a compact fiber-optic spectrometer. Emission spectra varied markedly with the laser wavelength and pulse duration. Optical feedback was not successful in differentiating between sound and carious enamel and dentin even with the addition of various chromophores to carious lesion areas. However, the spectral feedback was successfully used to differentiate between composites and sound enamel and dentin enabling the selective removal of composite from tooth surfaces using a computer controlled λ=9.3-μm pulsed CO II laser and scanning system.

  3. Special regime of liquid-assisted laser ablation of ceramics

    NASA Astrophysics Data System (ADS)

    Sinev, D. A.; Dobrina, D. A.; Strusevich, A. V.; Veiko, V. P.; Baranov, M. A.; Yakusheva, A. A.

    2016-05-01

    Results of experimental study the peculiarities of liquid-assisted laser ablation of alumina-silicate ceramics are reported giving attention particularly to effect of thin-wall glass macrosphere appearance at the end of irradiation onto a formed hole in bulk material. Typical times of formation, size and temperature dynamics, and chemical composition were determined; kinetics and mechanism of formation are discussed in presented paper.

  4. Influence of material properties on the hygrothermal performance of a high-rise residential wall

    SciTech Connect

    Karagiozis, A.N.; Salonvaara, M.

    1995-08-01

    Knowledge of the expected long-term performance of building envelopes subjected to the simultaneous heat and moisture transport is critical during the design stage. Increased incidents of rapid deterioration of high-rise building envelopes have further extended this concern to the rehabilitation of such structures. For durable and energy-efficient constructions, the knowledge of how the structure/construction behaves when subjected to a persistently harsh environment is needed. Recently this behavior has been simulated by sophisticated computer models that incorporate the transport physics of heat and moisture in porous construction materials. This paper investigates the influence of the variability of measured moisture transport properties on the overall hygrothermal performance of a high-rise construction wall. The analysis was carried out using a state-of-the-art hygrothermal model. The LATENITE model is a two-dimensional heat and moisture transport program tailored specifically for building envelop investigations. For the present simulations, the model was adapted for one-dimensional conditions and hourly simulations were predicted for a one-year performance of a high-rise wall section. Three types of facade cladding were used: two with red brick (one with an extremely high water vapor permeance, one with normal permeance) and one with a sandlime stone facade. Several cases for the wall systems were tested to determine the relative influence of moisture transport properties of the wall on the predicted results.

  5. Seven-wavelength pyrometer for determining surface temperature of ablation materials

    NASA Technical Reports Server (NTRS)

    Yi, H.

    1985-01-01

    Results which were achieved by a seven-wavelength pyrometer last year are reported in this paper. These studies are directed toward the development of a method for determining the real surface temperature of thermal protection materials and for evaluating its emittance under varieties of reentry environment. A description of the data processing method and apparatus is also included.

  6. Enchanced hohlraum radiation drive through reduction of wall losses with high-Z mixture "cocktail" wall materials

    SciTech Connect

    Schein, J; Jones, O; Rosen, M; Dewald, E; Glenzer, S; Gunther, J; Hammel, B; Landen, O; Suter, L; Wallace, R

    2006-05-17

    We present results from experiments, numerical simulations and analytic modeling, demonstrating enhanced hohlraum performance. Care in the fabrication and handling of hohlraums with walls consisting of high-Z mixtures (cocktails) has led to our demonstration, for the first time, of a significant increase in radiation temperature (up to +7eV at 300 eV) compared to a pure Au hohlraum, in agreement with predictions and ascribable to reduced wall losses. The data extrapolated to full NIF suggest we can expect an 18% reduction in wall loss for the current ignition design by switching to cocktail hohlraums, consistent with requirements for ignition with 1MJ laser energy.

  7. Development of a novel synthetic material to close abdominal wall defects.

    PubMed

    Cnota, M A; Aliabadi-Wahle, S; Choe, E U; Jacob, J T; Flint, L M; Ferrara, J J

    1998-05-01

    To compare the efficacy of a novel synthetic material (TMS-2) with polytetrafluoroethylene, polypropylene (Marlex), and primary closure of experimentally fashioned clean and contaminated abdominal wounds, 1-cm2 abdominal wall defects were created in each of the four abdominal quadrants of rats (n = 10). Patches of each material were used to repair three of these defects, the fourth being primarily closed. A second group of rats (n = 7) underwent the same operative protocol; however, peritonitis was induced at the time of surgery using a fecal inoculation technique. Animals were killed 2 weeks later, and surface area and severity of formed adhesions were assessed by a "blinded" observer. All closure techniques were successful insofar as none demonstrated fascial dehiscence. Compared with each synthetic material, the surface area of formed adhesions was smaller after primary closure in clean and in contaminated conditions; however, the three synthetic materials were equally matched regarding surface area of adhesions under both conditions. In the face of fecal contamination, TMS-2 proved identical to primary closure, each generating significantly (P < 0.02) milder adhesions than the other prosthetic materials. It is concluded that the TMS-2 may prove of clinical benefit to repair abdominal wall defects. PMID:9585774

  8. Assessment of skin dose for breast chest wall radiotherapy as a function of bolus material

    NASA Astrophysics Data System (ADS)

    Hsu, Shu-Hui; Roberson, Peter L.; Chen, Yu; Marsh, Robin B.; Pierce, Lori J.; Moran, Jean M.

    2008-05-01

    Skin dose assessment for chest wall radiotherapy is important to ensure sufficient dose to the surface target volume without excessive skin reaction. This study quantified changes to the surface doses as a function of bolus material for conventional and intensity modulated radiation therapy (IMRT) tangential fields. Three types of bolus materials (2 mm solid, 2 mm fine mesh and 3.2 mm large mesh Aquaplast) were compared with Superflab. Surface dose measurements were performed using an Attix parallel plate chamber in a flat solid water phantom at 0°, 45° and 70° incident angles. Over-response correction factors were applied to the Attix chamber results for different incident angles. Surface dose measurements on an anthropomorphic phantom were done using a thermoluminescent dosimeter extrapolation method. Dose characteristics of Superflab and solid Aquaplast were within 2% of solid water material. No significant differences (within 3%) in the surface dose were found between conventional and IMRT tangential techniques. The bolus effect was large for chest wall tangential radiotherapy, with up to an 82% increase using 2 mm fine mesh Aquaplast. The dosimetric effect of different Aquaplast materials has been quantified in this work. These materials can be used to create a custom bolus with potentially better reproducibility of placement.

  9. Preparation of Silicon Nitride Multilayer Ceramic Radome Material and Optimal Design of the Wall Structure

    SciTech Connect

    Chen Fei; Shen Qiang; Zhang Lianmeng

    2008-02-15

    A study of silicon nitride ceramic radomes, which includes preparation of the material and optimal design of the radome wall structure, is presented in this paper. Multilayer radome wall structure with high dielectric constant skins and a low dielectric constant core layer is used for broadband application. As a candidate material for both the skins and core layer, silicon nitride ceramics of controlled dielectric constant in the range 3.0{approx}7.5 were prepared by adding different content of sintering aids such as magnesia, alumina, silica and zirconium phosphate binder and choosing suitable sintering methods. A computer aided design (CAD) for the wall structure of silicon nitride multilayer ceramic radome based on microwave equivalent network method is carried out according to design requirements. By optimizing the thickness of skins and core layer, the power transmission efficiency of such a multilayer Si{sub 3}N{sub 4} ceramic radome is calculated. The calculated results suggest that when the dielectric constant of skins lies in the range 6{approx}7.5 and core layer in the range 3.5{approx}4, the power transmission efficiency is above 85% with frequency of 2{approx}18 GHz while the thickness of skins is less than 0.03{lambda} and the thickness ratio of skins to core layer is less than 1:15.

  10. Laser ablation of concrete.

    SciTech Connect

    Savina, M.

    1998-10-05

    Laser ablation is effective both as an analytical tool and as a means of removing surface coatings. The elemental composition of surfaces can be determined by either mass spectrometry or atomic emission spectroscopy of the atomized effluent. Paint can be removed from aircraft without damage to the underlying aluminum substrate, and environmentally damaged buildings and sculptures can be restored by ablating away deposited grime. A recent application of laser ablation is the removal of radioactive contaminants from the surface and near-surface regions of concrete. We present the results of ablation tests on concrete samples using a high power pulsed Nd:YAG laser with fiber optic beam delivery. The laser-surface interaction was studied on various model systems consisting of Type I Portland cement with varying amounts of either fine silica or sand in an effort to understand the effect of substrate composition on ablation rates and mechanisms. A sample of non-contaminated concrete from a nuclear power plant was also studied. In addition, cement and concrete samples were doped with non-radioactive isotopes of elements representative of cooling waterspills, such as cesium and strontium, and analyzed by laser-resorption mass spectrometry to determine the contamination pathways. These samples were also ablated at high power to determine the efficiency with which surface contaminants are removed and captured. The results show that the neat cement matrix melts and vaporizes when little or no sand or aggregate is present. Surface flows of liquid material are readily apparent on the ablated surface and the captured aerosol takes the form of glassy beads up to a few tens of microns in diameter. The presence of sand and aggregate particles causes the material to disaggregate on ablation, with intact particles on the millimeter size scale leaving the surface. Laser resorption mass spectrometric analysis showed that cesium and potassium have similar chemical environments in the

  11. Method of measuring material properties of rock in the wall of a borehole

    DOEpatents

    Overmier, D.K.

    1984-01-01

    To measure the modulus of elasticity of the rock in the wall of a borehole, a plug is cut in the borehole wall. The plug, its base attached to the surrounding rock, acts as a short column in response to applied forces. A loading piston is applied to the top of the plug and compression of the plug is measured as load is increased. Measurements of piston load and plug longitudinal deformation are made to determine the elastic modulus of the plug material. Poisson's ratio can be determined by simultaneous measurements of longitudinal and lateral deformation of the plug in response to loading. To determine shear modulus, the top of the plug is twisted while measurements are taken of torsional deformation.

  12. Method of measuring material properties of rock in the wall of a borehole

    DOEpatents

    Overmier, David K.

    1985-01-01

    To measure the modulus of elasticity of the rock in the wall of a borehole, a plug is cut in the borehole wall. The plug, its base attached to the surrounding rock, acts as a short column in response to applied forces. A loading piston is applied to the top of the plug and compression of the plug is measured as load is increased. Measurement of piston load and plug longitudinal deformation are made to determine the elastic modulus of the plug material. Poisson's ratio can be determined by simultaneous measurements of longitudinal and lateral deformation of the plug in response to loading. To determine shear modulus, the top of the plug is twisted while measurements are taken of torsional deformation.

  13. Deposition Mitigation of the First Mirrors Exposed in EAST with Metal and Carbon Mixed Wall Materials

    NASA Astrophysics Data System (ADS)

    Yan, Rong; Chen, Junling; Chen, Longwei; Zhu, Dahuan

    2014-09-01

    In order to investigate the effect of aperture geometry on deposition mitigation, stainless steel (SS) first mirrors (FMs) were fixed on the holders of protective aperture geometry with different depth-diameter ratios (DDRs) and exposed in the deposition dominated environment of EAST. A baffle was used during the wall conditioning. The surface properties and reflectivity of the FMs were characterized before and after exposure. It is shown that using aperture geometry and a baffle can effectively mitigate the impurities deposition. The degradation of the surface and specular reflectivity of the FMs is reduced with the increase of DDRs in the range of 0 to 2. The main contaminated elements in a low-Z and high-Z mixed wall materials environment were still carbon and oxygen.

  14. Advanced Ablative TPS

    NASA Technical Reports Server (NTRS)

    Gasch, Matthew J.

    2011-01-01

    Early NASA missions (Gemini, Apollo, Mars Viking) employed new ablative TPS that were tailored for the entry environment. After 40 years, heritage ablative TPS materials using Viking or Pathfinder era materials are at or near their performance limits and will be inadequate for future exploration missions. Significant advances in TPS materials technology are needed in order to enable any subsequent human exploration missions beyond Low Earth Orbit. This poster summarizes some recent progress at NASA in developing families of advanced rigid/conformable and flexible ablators that could potentially be used for thermal protection in planetary entry missions. In particular the effort focuses technologies required to land heavy (approx.40 metric ton) masses on Mars to facilitate future exploration plans.

  15. Ultrasonic characterization of laser ablation

    NASA Astrophysics Data System (ADS)

    Smith, J. A.; Telschow, K. L.

    When a pulsed laser beam strikes the surface of an absorbing material, ultrasonic waves are generated due to thermoelectric expansion and, at higher laser power densities, ablation of the material. These sound generation mechanisms have been the subject of numerous theoretical and experimental studies and are now fairly well understood. In particular, it has been established that at low power densities the thermoelastic mechanism is well described by a surface center of expansion. This mechanism produces a characteristic waveform whose amplitude is proportional to the energy absorbed from the laser pulse and also dependent on the thermal and elastic properties of the material. The ablation ultrasonic source can be described by a point normal force acting on the material surface. For laser power densities near the ablation onset, the time dependence of the source is that of the laser pulse. The resultant waveform recorded on epicenter (source and detector collinear) has a sharp peak determined by the momentum impulse delivered to the material by the ablation process. Particularly in the near ablation onset region, this ultrasonic displacement peak can be used to characterize the ablation process occurring at the material surface. The onset power density for ablation and subsequent ablation dependence on power density are material dependent and thought to be a function of the heat capacity and thermal conductivity of the material. With this in mind, it is possible that these ablation signals could be used to characterize material microstructures, and perhaps material mechanical properties such as hardness, through microstructural changes of the material thermal parameters. This paper explores this question for samples of Type 304 stainless steel with microstructures controlled through work hardening and annealing.

  16. Modeling and analysis of electrostatic adhesion force for climbing robot on dielectric wall materials

    NASA Astrophysics Data System (ADS)

    Mao, Jiu-Bing; Qin, Lan; Zhang, Wan-Xiong; Xie, Li; Wang, Yong

    2015-01-01

    In recent years, electrostatic adhesion technology on the wall climbing robots has attracted many researchers interest for its outstanding characteristics. In this paper, a theoretical analytical model is derived from the electrostatic adhesion field between the dielectric wall and a coplanar array of parallel strip electrodes called inter-digital electrodes (IDE). Due to the polarization on the different dielectric being complicated, the field is divided into four layers in order to obtain corresponding boundaries. Besides, the roughness of the wall surface, alternately polarities applied voltages and different dielectric parameter with different layer, all of which are also taken into account in the model since they have a significant influence on the electrostatic adhesion field. Based on this model, the electrostatic adhesion force (EAF) is calculated utilizing the Maxwell stress tensor (MST) formulation. As we all known, EAF is vital to the climbing robot design. Specially, it is possible for us to optimize the load to weight ratio in next step. Through comparing the finite element method (FEM) simulation with theoretical computation, the simulation and calculated data show that our proposed scheme can achieve desired results. Moreover, experiments of electrostatic adhesion performance for the adhesive on some different dielectric materials are also implemented.

  17. Layer-dependent wall properties of abdominal aortic aneurysms: Experimental study and material characterization.

    PubMed

    Sassani, Sophia G; Kakisis, John; Tsangaris, Sokrates; Sokolis, Dimitrios P

    2015-09-01

    Mechanical testing and in-depth characterization of the abdominal aortic aneurysm wall from fifteen patients undergoing open surgery was performed to establish the layer-dependent tissue properties that are non-available in the literature. Quantitative microscopic evaluation was performed to identify the spatial organization of collagen-fiber network. Among a number of candidate models, the four-fiber family (microstructure-motivated) model, especially that including dispersions of fiber angles about the main directions, was superior to the Fung- and Gasser-type models in the fitting quality allowed, though it presented a practical difficulty in parameter estimation, so that an analysis was conducted aiding the identification of a more specific diagonal- and circumferential-fiber family model for all three layers. The adventitia was stiffer and stronger than the other layers, owing to its increased collagen content, and its contribution to the response of the intact wall was augmented being under greater residual tension than the media, whereas the intima was under residual compression. All layers were stiffer circumferentially than longitudinally, due to preferential collagen arrangement along that axis. The histologically-guided material characterization of layered wall presented herein is expected to assist clinical decision, by developing reliable criteria to predict the rupture risk of abdominal aortic aneurysms, and optimize endovascular interventions. PMID:26011656

  18. Potential Energy Savings Due to Phase Change Material in a Building Wall Assembly: An Examination of Two Climates

    SciTech Connect

    Childs, Kenneth W; Stovall, Therese K

    2012-03-01

    Phase change material (PCM), placed in an exterior wall, alters the temperature profile within the wall and thus influences the heat transport through the wall. This may reduce the net energy transport through the wall via interactions with diurnal temperature swings in the external environment or reduce the electricity needed to meet the net load through the wall by shifting the time of the peak load to a time when the cooling system operates more efficiently. This study covers a broad range of parameters that can influence the effectiveness of such a merged thermal storage-thermal insulation system. These parameters included climate, PCM location within the wall, amount of PCM, midpoint of the PCM melting and freezing range relative to the indoor setpoint temperature, temperature range over which phase change occurs, and the wall orientation. Two climates are investigated using finite difference and optimization analyses: Phoenix and Baltimore, with two utility rate schedules. Although potential savings for a PCM with optimized properties were greater when the PCM was concentrated near the inside wall surface, other considerations described here lead to a recommendation for a full-thickness application. An examination of the temperature distribution within the walls also revealed the potential for this system to reduce the amount of energy transported through the wall framing. Finally, economic benefits can exceed energy savings when time-of-day utility rates are in effect, reflecting the value of peak load reductions for the utility grid.

  19. Development and evaluation of first wall materials for the National Ignition Facility

    SciTech Connect

    Burnham, A.K.; Tobin, M.T.; Anderson, A.T.; Honea, E.C.; Skulina, K.M.; Milam, D.; Evans, M.; Rainer, F.; Gerassimenko, M.

    1996-06-12

    Several low-Z refractory materials are evaluated for use as the NIF first wall in terms of their cost and ability to survive laser light, target emissions and debris, as well as be cleanable and not outgas excessively. Best performers contain B, C, or both, with B{sub 4}C being the best overall. It appears possible at this time that plasma-sprayed B{sub 4}C can be fabricated with low enough porosity and cost to be preferred to hot-pressed B{sub 4}C, the conservative choice.

  20. The roles of thermal insulation and heat storage in the energy performance of the wall materials: a simulation study

    PubMed Central

    Long, Linshuang; Ye, Hong

    2016-01-01

    A high-performance envelope is the prerequisite and foundation to a zero energy building. The thermal conductivity and volumetric heat capacity of a wall are two thermophysical properties that strongly influence the energy performance. Although many case studies have been performed, the results failed to give a big picture of the roles of these properties in the energy performance of an active building. In this work, a traversal study on the energy performance of a standard room with all potential wall materials was performed for the first time. It was revealed that both heat storage materials and insulation materials are suitable for external walls. However, the importances of those materials are distinct in different situations: the heat storage plays a primary role when the thermal conductivity of the material is relatively high, but the effect of the thermal insulation is dominant when the conductivity is relatively low. Regarding internal walls, they are less significant to the energy performance than the external ones, and they need exclusively the heat storage materials with a high thermal conductivity. These requirements for materials are consistent under various climate conditions. This study may provide a roadmap for the material scientists interested in developing high-performance wall materials. PMID:27052186

  1. The roles of thermal insulation and heat storage in the energy performance of the wall materials: a simulation study.

    PubMed

    Long, Linshuang; Ye, Hong

    2016-01-01

    A high-performance envelope is the prerequisite and foundation to a zero energy building. The thermal conductivity and volumetric heat capacity of a wall are two thermophysical properties that strongly influence the energy performance. Although many case studies have been performed, the results failed to give a big picture of the roles of these properties in the energy performance of an active building. In this work, a traversal study on the energy performance of a standard room with all potential wall materials was performed for the first time. It was revealed that both heat storage materials and insulation materials are suitable for external walls. However, the importances of those materials are distinct in different situations: the heat storage plays a primary role when the thermal conductivity of the material is relatively high, but the effect of the thermal insulation is dominant when the conductivity is relatively low. Regarding internal walls, they are less significant to the energy performance than the external ones, and they need exclusively the heat storage materials with a high thermal conductivity. These requirements for materials are consistent under various climate conditions. This study may provide a roadmap for the material scientists interested in developing high-performance wall materials. PMID:27052186

  2. The roles of thermal insulation and heat storage in the energy performance of the wall materials: a simulation study

    NASA Astrophysics Data System (ADS)

    Long, Linshuang; Ye, Hong

    2016-04-01

    A high-performance envelope is the prerequisite and foundation to a zero energy building. The thermal conductivity and volumetric heat capacity of a wall are two thermophysical properties that strongly influence the energy performance. Although many case studies have been performed, the results failed to give a big picture of the roles of these properties in the energy performance of an active building. In this work, a traversal study on the energy performance of a standard room with all potential wall materials was performed for the first time. It was revealed that both heat storage materials and insulation materials are suitable for external walls. However, the importances of those materials are distinct in different situations: the heat storage plays a primary role when the thermal conductivity of the material is relatively high, but the effect of the thermal insulation is dominant when the conductivity is relatively low. Regarding internal walls, they are less significant to the energy performance than the external ones, and they need exclusively the heat storage materials with a high thermal conductivity. These requirements for materials are consistent under various climate conditions. This study may provide a roadmap for the material scientists interested in developing high-performance wall materials.

  3. Effect of Surface Nonequilibrium Thermochemistry in Simulation of Carbon Based Ablators

    NASA Technical Reports Server (NTRS)

    Chen, Yih-Kang; Gokcen, Tahir

    2012-01-01

    This study demonstrates that coupling of a material thermal response code and a flow solver using finite-rate gas/surface interaction model provides time-accurate solutions for multidimensional ablation of carbon based charring ablators. The material thermal response code used in this study is the Two-dimensional Implicit Thermal Response and Ablation Program (TITAN), which predicts charring material thermal response and shape change on hypersonic space vehicles. Its governing equations include total energy balance, pyrolysis gas momentum conservation, and a three-component decomposition model. The flow code solves the reacting Navier-Stokes equations using Data Parallel Line Relaxation (DPLR) method. Loose coupling between material response and flow codes is performed by solving the surface mass balance in DPLR and the surface energy balance in TITAN. Thus, the material surface recession is predicted by finite-rate gas/surface interaction boundary conditions implemented in DPLR, and the surface temperature and pyrolysis gas injection rate are computed in TITAN. Two sets of gas/surface interaction chemistry between air and carbon surface developed by Park and Zhluktov, respectively, are studied. Coupled fluid-material response analyses of stagnation tests conducted in NASA Ames Research Center arc-jet facilities are considered. The ablating material used in these arc-jet tests was a Phenolic Impregnated Carbon Ablator (PICA). Computational predictions of in-depth material thermal response and surface recession are compared with the experimental measurements for stagnation cold wall heat flux ranging from 107 to 1100 Watts per square centimeter.

  4. Advanced Rigid Ablative TPS

    NASA Technical Reports Server (NTRS)

    Gasch, Matthew J.

    2011-01-01

    NASA Exploration Systems Mission Directorate s (ESMD) Entry, Descent, and Landing (EDL) Technology Development Project (TDP) and the NASA Aeronautics Research Mission Directorate s (ARMD) Hypersonics Project are developing new advanced rigid ablators in an effort to substantially increase reliability, decrease mass, and reduce life cycle cost of rigid aeroshell-based entry systems for multiple missions. Advanced Rigid Ablators combine ablation resistant top layers capable of high heat flux entry and enable high-speed EDL with insulating mass-efficient bottom that, insulate the structure and lower the areal weight. These materials may benefit Commercial Orbital Transportation Services (COTS) vendors and may potentially enable new NASA missions for higher velocity returns (e.g. asteroid, Mars). The materials have been thermally tested to 400-450 W/sq cm at the Laser Hardened Materials Evaluation Lab (LHMEL), Hypersonics Materials Evaluation Test System (HyMETS) and in arcjet facilities. Tested materials exhibit much lower backface temperatures and reduced recession over the baseline materials (PICA). Although the EDL project is ending in FY11, NASA in-house development of advanced ablators will continue with a focus on varying resin systems and fiber/resin interactions.

  5. Species-resolved laser-probing investigations of the hydrodynamics of KrF excimer and copper vapor laser ablation processing of materials

    NASA Astrophysics Data System (ADS)

    Ventzek, Peter L. G.; Gilgenbach, Ronald M.; Ching, Chi H.; Lindley, R. A.

    1993-06-01

    Hydrodynamic phenomena from KrF excimer laser ablation (10-3-20 J/cm2) of polyimide, polyethyleneterephthalate, and aluminum are diagnosed by laser beam deflection, schlieren photography, shadowgraphy, laser-induced-fluorescence and dye-laser- resonance absorption photography (DLRAP). Experiments were performed in vacuum and gaseous environments (10-5 to 760 Torr). In vacuum, the DLRAP diagnostic shows species-resolved plume expansion which is consistent with that of a reflected rarefaction wave. Increasing the background gas pressure reveals the formation of sound/shock compared to CN in the laser-ablated polyimide (Vespel) plume/shock in inert (e.g. argon) and reactive (e.g. air) gases. At low pressures (less than 10 Torr) Al and CN species are in close contact with the shock front. As the pressure increases, the species front tends to recede, until at high pressures (over 200 Torr) the species are restrained to only a few mm above the target surface. After sufficient expansion, Al and CN are no longer detectable; only the shadowgraph of the hot gas plume remains. Since CN is observable in both inert and reactive environments, it can be concluded that CN is not a reaction product between the background gas and the ablated species. By way of comparison to excimer laser ablation processing of materials, copper vapor laser machined polyimide and polymethylmethacrylate (transparent to green and yellow copper vapor laser light) are also investigated. The two polymers are observed to have markedly different machined surfaces. Hydrodynamic effects for the copper vapor laser machined materials are investigated using HeNe laser beam deflection.

  6. Geolaser probe - a versitile laser ablation system for the direct analysis of geological materials by ICP-MS

    SciTech Connect

    Zhu, J.J.; Brenner, I.B.

    1995-12-31

    A description will be given of a new laser ablation system, The CETAC LSX-100, designed specifically for geoanalysis using ICP-MS. The frequency quadrupled ultraviolet Nd-YAG laser, producing 5 - 1000 {mu}m crater diameters, allows the determination of both low elemental contents and isotope ratios in the minerals and isotopic variations and time-resolved measurements of fluid-solid inclusions. A unique feature is an optional high performance petrographic microscope providing both reflected and transmitted illumination for mineral identification prior to laser ablation. Results of studies will be presented.

  7. Microencapsulation of Lactobacillus acidophilus NCFM using polymerized whey proteins as wall material.

    PubMed

    Jiang, Yujun; Zheng, Zhe; Zhang, Tiehua; Hendricks, Gregory; Guo, Mingruo

    2016-09-01

    Survivability of probiotics in foods is essential for developing functional food containing probiotics. We investigated polymerized whey protein (PWP)-based microencapsulation process which is developed for protecting probiotics like Lactobacillus acidophilus NCFM and compared with the method using sodium alginate (SA). The entrapment rate was 89.3 ± 4.8% using PWP, while it was 73.2 ± 1.4% for SA. The microencapsulated NCFM by PWP and SA were separately subjected to digestion juices and post-fermentation storage of fermented cows' and goats' milk using the encapsulated culture. The log viable count of NCFM in PWP-based microencapsulation was 4.56, compared with that of 4.26 in SA-based ones and 3.13 for free culture. Compared with using SA as wall material, PWP was more effective in protecting probiotic. Microencapsulation of L. acidophilus NCFM using PWP as wall material can be exploited in the development of fermented dairy products with better survivability of probiotic organism. PMID:27309796

  8. Material Behavior Based Hybrid Process for Sheet Draw-Forging Thin Walled Magnesium Alloys

    SciTech Connect

    Sheng, Z.Q.; Shivpuri, R.

    2005-08-05

    Magnesium alloys are conventionally formed at the elevated temperatures. The thermally improved formability is sensitive to the temperature and strain rate. Due to limitations in forming speeds, tooling strength and narrow processing windows, complex thin walled parts cannot be made by traditional warm drawing or hot forging processes. A hybrid process, which is based on the deformation mechanism of magnesium alloys at the elevated temperature, is proposed that combines warm drawing and hot forging modes to produce an aggressive geometry at acceptable forming speed. The process parameters, such as temperatures, forming speeds etc. are determined by the FEM modeling and simulation. Sensitivity analysis under the constraint of forming limits of Mg alloy sheet material and strength of tooling material is carried out. The proposed approach is demonstrated on a conical geometry with thin walls and with bottom features. Results show that designed geometry can be formed in about 8 seconds, this cannot be formed by conventional forging while around 1000s is required for warm drawing. This process is being further investigated through controlled experiments.

  9. Solid state 1H NMR studies of cell wall materials of potatoes

    NASA Astrophysics Data System (ADS)

    Tang, Huiru; Belton, Peter S.; Ng, Annie; Waldron, Keith W.; Ryden, Peter

    1999-04-01

    Cell wall materials from potatoes ( Solanum tuberosum) prepared by two different methods have been studied using NMR proton relaxation times. Spin lattice relaxation in both the rotating and laboratory frames as well as transverse relaxation have been measured over a range of temperatures and hydration levels. It was observed that the sample prepared using a DMSO extraction showed anomalous behaviour of spin lattice relaxation in the laboratory frame probably due to residual solvent in the sample. Spin lattice relaxation in the laboratory frame is the result of hydroxymethyl rotation and another unidentified high frequency motion. In the rotating frame relaxation is adequately explained by hydroxymethyl rotation alone. In neither experiment is methyl group rotation observed, calculation suggests that this is due to the low density of methyl groups in the sample. Non-freezing water in potato cell walls, α-cellulose and pectin was found about 0.2, 0.04 and 0.18 g per gram dry matter, indicating preferable hydration of pectin compared to cellulose. The effects of hydration are most noticeable in the measurements that reflect low frequency motions, particularly transverse relaxation, where both second moments and the relative intensity of signals arising from immobile material are reduced by hydration.

  10. Physicochemical Properties and Storage Stability of Microencapsulated DHA-Rich Oil with Different Wall Materials.

    PubMed

    Chen, Wuxi; Wang, Haijun; Zhang, Ke; Gao, Feng; Chen, Shulin; Li, Demao

    2016-08-01

    This study aimed to evaluate the physicochemical properties and storage stability of microencapsulated DHA-rich oil spray dried with different wall materials: model 1 (modified starch, gum arabic, and maltodextrin), model 2 (soy protein isolate, gum arabic, and maltodextrin), and model 3 (casein, glucose, and lactose). The results indicated that model 3 exhibited the highest microencapsulation efficiency (98.66 %) and emulsion stability (>99 %), with a moisture content and mean particle size of 1.663 % and 14.173 μm, respectively. Differential scanning calorimetry analysis indicated that the Tm of DHA-rich oil microcapsules was high, suggesting that the entire structure of the microcapsules remained stable during thermal processing. A thermogravimetric analysis curve showed that the product lost 5 % of its weight at 172 °C and the wall material started to degrade at 236 °C. The peroxide value of microencapsulated DHA-rich oil remained at one ninth after accelerated oxidation at 45 °C for 8 weeks to that of the unencapsulated DHA-rich oil, thus revealing the promising oxidation stability of DHA-rich oil in microcapsules. PMID:27003283

  11. Novel Materials Containing Single-Wall Carbon Nanotubes Wrapped in Polymer Molecules

    NASA Technical Reports Server (NTRS)

    Smalley, Richard E.; O'Connell, Michael J.; Smith, Kenneth; Colbert, Daniel T.

    2009-01-01

    In this design, single-wall carbon nanotubes (SWNTs) have been coated in polymer molecules to create a new type of material that has low electrical conductivity, but still contains individual nanotubes, and small ropes of individual nanotubes, which are themselves good electrical conductors and serve as small conducting rods immersed in an electrically insulating matrix. The polymer is attached through weak chemical forces that are primarily non-covalent in nature, caused primarily through polarization rather than the sharing of valence electrons. Therefore, the electronic structure of the SWNT involved is substantially the same as that of free, individual (and small ropes of) SWNT. Their high conductivity makes the individual nanotubes extremely electrically polarizable, and materials containing these individual, highly polarizable molecules exhibit novel electrical properties including a high dielectric constant.

  12. LIFE Materials: Topical Assessment Report for LIFE Volume 1 TOPIC: Solid First Wall and Structural Components TASK: Radiation Effects on First Wall

    SciTech Connect

    Caro, A

    2008-11-26

    This report consists of the following chapters: CHAPTER A: LIFE Requirements for Materials. Part 1: The structure of the First Wall--Basic requirements; A qualitative view of the challenge; The candidate materials; and Base-line material's properties. CHAPTER B: Summary of Existing Knowledge--Brief historical introduction; Design window; The temperature window; Evolution of the design window with damage; Damage calculations; He and H production; Swelling resistance; Incubation dose for swelling; Design criterion No. 1, Strength; Design criterion No. 2, Corrosion resistance; Design criterion No. 3, Creep resistance; Design criterion No. 4, Radiation induced embrittlement; and Conclusions. CHAPTER C: Identification of Gaps in Knowledge & Vulnerabilities. CHAPTER D: Strategy and Future Work.

  13. Endometrial ablation

    MedlinePlus

    ... can be seen on the video screen. Small tools can be used through the scope to remove abnormal growths or tissue for examination. Ablation uses heat, cold, or electricity to destroy the lining of the womb. The ...

  14. NASA-JSC Protocol for the Characterization of Single Wall Carbon Nanotube Material Quality

    NASA Technical Reports Server (NTRS)

    Arepalli, Sivaram; Nikolaev, Pasha; Gorelik, Olga; Hadjiev, Victor; Holmes, William; Devivar, Rodrigo; Files, Bradley; Yowell, Leonard

    2010-01-01

    It is well known that the raw as well as purified single wall carbon nanotube (SWCNT) material always contain certain amount of impurities of varying composition (mostly metal catalyst and non-tubular carbon). Particular purification method also creates defects and/or functional groups in the SWCNT material and therefore affects the its dispersability in solvents (important to subsequent application development). A number of analytical characterization tools have been used successfully in the past years to assess various properties of nanotube materials, but lack of standards makes it difficult to compare these measurements across the board. In this work we report the protocol developed at NASA-JSC which standardizes measurements using TEM, SEM, TGA, Raman and UV-Vis-NIR absorption techniques. Numerical measures are established for parameters such as metal content, homogeneity, thermal stability and dispersability, to allow easy comparison of SWCNT materials. We will also report on the recent progress in quantitative measurement of non-tubular carbon impurities and a possible purity standard for SWCNT materials.

  15. Angled Cool-Tip Electrode for Radiofrequency Ablation of Small Superficial Subcapsular Tumors in the Liver: A Feasibility Study

    PubMed Central

    Kim, Il Jung; Lee, Shin Jae; Shin, Min Woo; Shin, Won Sun; Chung, Yong Eun; Kim, Gyoung Min; Kim, Man Deuk; Won, Jong Yun; Lee, Do Yun; Choi, Jin Sub; Han, Kwang-Hyub

    2016-01-01

    Objective To evaluate the feasibility of angled cool-tip electrode for radiofrequency ablation of small superficial subcapsular liver tumors abutting abdominal wall, in order to traverse normal liver parenchyma, and thereby, obtain favorable configuration of ablation margin. Materials and Methods In this study, we retrospectively analyzed 15 small superficial subcapsular liver tumors abutting abdominal wall in 15 patients, treated with radiofrequency ablation from March 2013 to June 2015 using a cool-tip electrode manually modified to create 25–35° angle at the junction between exposed and insulated segments. The tumors were hepatocellular carcinoma (n = 13) and metastases (n = 2: cholangiocellular carcinoma and rectosigmoid cancer), with maximum diameter of 10–26 mm (mean, 15.68 ± 5.29 mm). Under ultrasonographic guidance, the electrode tip was advanced to the depth of the tumors' epicenter about 1 cm from the margin. The tip was re-directed to penetrate the tumor for radiofrequency ablation. Minimal ablation margin was measured at immediate post-treatment CT. Radiological images and medical records were evaluated for success rate, length of minimal ablation margin and complications. Results Technical success rate of obtaining complete necrosis of the tumors was 100%, with no procedure-related complication. Minimal ablation margin ranged from 3–12 mm (mean, 7.07 ± 2.23 mm). CT/MRI follow-up at 21–1022 days (mean, 519.47 ± 304.51 days) revealed no local recurrence, but distant recurrence in 9 patients. Conclusion Using an angled cool-tip electrode for radiofrequency ablation of small superficial subcapsular tumors abutting abdominal wall may be a feasible technique for obtaining adequate ablation margin and lower complication rate. PMID:27587963

  16. Comparison of novel synthetic materials with traditional methods to repair exposed abdominal wall fascial defects.

    PubMed

    Aliabadi-Wahle, S; Cnota, M; Choe, E; Jacob, J T; Flint, L M; Ferrara, J J

    1998-01-01

    Repair of large abdominal wall defects is a challenge, particularly when full-thickness tissue loss prohibits coverage of the fascial repair. Two novel synthetic materials (TMS-1 and TMS-2) have been shown to be better accepted than expanded polytetrafluoroethylene (Gore-Tex), and polypropylene (Marlex) in the closure of clean and contaminated fascial wounds that are immediately covered by skin/soft tissue. Therefore, 1-cm2 abdominal wall defects were created in each of the four quadrants of rat groups. Gore-Tex, Marlex, and TMS-1 or TMS-2 were used to repair three defects, the fourth being primarily closed. To ensure that each repair remained exposed, skin edges were sutured to underlying muscle. Additional animal groups underwent the same protocol; however, peritonitis was induced at surgery using a fecal inoculum technique. Animals were sacrificed 2 weeks later, at which time a blinded observer assessed the surface area and severity of adhesions. In clean wounds, the surface area of formed adhesions was less (p < .004) after primary closure than each synthetic material; among the synthetics, TMS-2 caused significantly (p < .01) less extensive adhesions than Marlex. In addition, the severity of adhesions to TMS-2 was comparable to that of defects closed primarily, and less severe (p < .02) than those formed to Gore-Tex and Marlex. In animals with peritonitis, primary closure caused less extensive (p < .03) adhesions than Marlex and Gore-Tex and significantly (p < .002) less severe adhesions than Marlex, Gore-Tex, and TMS-2. However, the severity of adhesions formed to TMS-1 repairs proved comparable to primarily closed wounds. These experiments reaffirm the tenet that, whenever possible, abdominal wounds should undergo primary fascial closure. When soft tissue coverage over the repair cannot be achieved, TMS-2 is well tolerated in clean wounds. However, the superiority of TMS-1 over the other synthetic materials in contaminated wounds suggests it may also

  17. The direct determination of trace metals in gold and silver materials by laser ablation inductively coupled plasma mass spectrometry without matrix matched standards

    NASA Astrophysics Data System (ADS)

    Kogan, Valentina V.; Hinds, Michael W.; Ramendik, Gregory I.

    1994-04-01

    Typically, accurate trace element determination in solid samples by laser ablation ICP-MS requires calibration with matrix matched standards. Trace metal analysis was performed in high purity gold, high purity silver and 14 karat gold-silver alloys. A Nd : YAG laser was used to evaporate solid samples of precious metals into an inductively coupled plasma mass spectrometer. Analytical data and a study of the crater sizes indicated that approximately the same amount of material for both gold and silver samples was vaporized by a Nd : YAG laser operated in a Q-switched mode with the following parameters: 210 mJ laser energy; 8 Hz repetition rate; and focused 7 mm below the sample surface. High purity gold and silver, and a 14 karat gold-silver alloy were analyzed for trace metals common to gold and silver reference materials. In general, the determination of Fe, Ni, Cu, Zn, Pd, Pt, Pb, and Bi did not strongly depend on whether gold or silver reference materials were used for calibration. This permits these trace metals to be determined directly with only one set of reference materials, by laser ablation ICP-MS, in a wide variety of gold-silver alloys.

  18. Ablative thermal protection systems

    NASA Technical Reports Server (NTRS)

    Vaniman, J.; Fisher, R.; Wojciechowski, C.; Dean, W.

    1983-01-01

    The procedures used to establish the TPS (thermal protection system) design of the SRB (solid rocket booster) element of the Space Shuttle vehicle are discussed. A final evaluation of the adequacy of this design will be made from data obtained from the first five Shuttle flights. Temperature sensors installed at selected locations on the SRB structure covered by the TPS give information as a function of time throughout the flight. Anomalies are to be investigated and computer design thermal models adjusted if required. In addition, the actual TPS ablator material loss is to be measured after each flight and compared with analytically determined losses. The analytical methods of predicting ablator performance are surveyed.

  19. Material migration studies with an ITER first wall panel proxy on EAST

    DOE PAGESBeta

    Ding, R.; Pitts, R. A.; Borodin, D.; Carpentier, S.; Ding, F.; Gong, X. Z.; Guo, H. Y.; Kirschner, A.; Kocan, M.; Li, J. G.; et al

    2015-01-23

    The ITER beryllium (Be) first wall (FW) panels are shaped to protect leading edges between neighbouring panels arising from assembly tolerances. This departure from a perfectly cylindrical surface automatically leads to magnetically shadowed regions where eroded Be can be re-deposited, together with co-deposition of tritium fuel. To provide a benchmark for a series of erosion/re-deposition simulation studies performed for the ITER FW panels, dedicated experiments have been performed on the EAST tokamak using a specially designed, instrumented test limiter acting as a proxy for the FW panel geometry. Carbon coated molybdenum plates forming the limiter front surface were exposed tomore » the outer midplane boundary plasma of helium discharges using the new Material and Plasma Evaluation System (MAPES). Net erosion and deposition patterns are estimated using ion beam analysis to measure the carbon layer thickness variation across the surface after exposure. The highest erosion of about 0.8 µm is found near the midplane, where the surface is closest to the plasma separatrix. No net deposition above the measurement detection limit was found on the proxy wall element, even in shadowed regions. The measured 2D surface erosion distribution has been modelled with the 3D Monte Carlo code ERO, using the local plasma parameter measurements together with a diffusive transport assumption. In conclusion, excellent agreement between the experimentally observed net erosion and the modelled erosion profile has been obtained.« less

  20. Material migration studies with an ITER first wall panel proxy on EAST

    SciTech Connect

    Ding, R.; Pitts, R. A.; Borodin, D.; Carpentier, S.; Ding, F.; Gong, X. Z.; Guo, H. Y.; Kirschner, A.; Kocan, M.; Li, J. G.; Luo, G. -N.; Mao, H. M.; Qian, J. P.; Stangeby, P. C.; Wampler, W. R.; Wang, H. Q.; Wang, W. Z.; Chen, J. L.; Gan, K. F.

    2015-01-23

    The ITER beryllium (Be) first wall (FW) panels are shaped to protect leading edges between neighbouring panels arising from assembly tolerances. This departure from a perfectly cylindrical surface automatically leads to magnetically shadowed regions where eroded Be can be re-deposited, together with co-deposition of tritium fuel. To provide a benchmark for a series of erosion/re-deposition simulation studies performed for the ITER FW panels, dedicated experiments have been performed on the EAST tokamak using a specially designed, instrumented test limiter acting as a proxy for the FW panel geometry. Carbon coated molybdenum plates forming the limiter front surface were exposed to the outer midplane boundary plasma of helium discharges using the new Material and Plasma Evaluation System (MAPES). Net erosion and deposition patterns are estimated using ion beam analysis to measure the carbon layer thickness variation across the surface after exposure. The highest erosion of about 0.8 µm is found near the midplane, where the surface is closest to the plasma separatrix. No net deposition above the measurement detection limit was found on the proxy wall element, even in shadowed regions. The measured 2D surface erosion distribution has been modelled with the 3D Monte Carlo code ERO, using the local plasma parameter measurements together with a diffusive transport assumption. In conclusion, excellent agreement between the experimentally observed net erosion and the modelled erosion profile has been obtained.

  1. Material migration studies with an ITER first wall panel proxy on EAST

    NASA Astrophysics Data System (ADS)

    Ding, R.; Pitts, R. A.; Borodin, D.; Carpentier, S.; Ding, F.; Gong, X. Z.; Guo, H. Y.; Kirschner, A.; Kocan, M.; Li, J. G.; Luo, G.-N.; Mao, H. M.; Qian, J. P.; Stangeby, P. C.; Wampler, W. R.; Wang, H. Q.; Wang, W. Z.

    2015-02-01

    The ITER beryllium (Be) first wall (FW) panels are shaped to protect leading edges between neighbouring panels arising from assembly tolerances. This departure from a perfectly cylindrical surface automatically leads to magnetically shadowed regions where eroded Be can be re-deposited, together with co-deposition of tritium fuel. To provide a benchmark for a series of erosion/re-deposition simulation studies performed for the ITER FW panels, dedicated experiments have been performed on the EAST tokamak using a specially designed, instrumented test limiter acting as a proxy for the FW panel geometry. Carbon coated molybdenum plates forming the limiter front surface were exposed to the outer midplane boundary plasma of helium discharges using the new Material and Plasma Evaluation System (MAPES). Net erosion and deposition patterns are estimated using ion beam analysis to measure the carbon layer thickness variation across the surface after exposure. The highest erosion of about 0.8 µm is found near the midplane, where the surface is closest to the plasma separatrix. No net deposition above the measurement detection limit was found on the proxy wall element, even in shadowed regions. The measured 2D surface erosion distribution has been modelled with the 3D Monte Carlo code ERO, using the local plasma parameter measurements together with a diffusive transport assumption. Excellent agreement between the experimentally observed net erosion and the modelled erosion profile has been obtained.

  2. Evaluation of a Thermoprotective Gel for Hydrodissection During Percutaneous Microwave Ablation: In Vivo Results

    SciTech Connect

    Moreland, Anna J. Lubner, Meghan G. Ziemlewicz, Timothy J. Kitchin, Douglas R. Hinshaw, J. Louis Johnson, Alexander D. Lee, Fred T. Brace, Christopher L.

    2015-06-15

    PurposeTo evaluate whether thermoreversible poloxamer 407 15.4 % in water (P407) can protect non-target tissues adjacent to microwave (MW) ablation zones in a porcine model.Materials and MethodsMW ablation antennas were placed percutaneously into peripheral liver, spleen, or kidney (target tissues) under US and CT guidance in five swine such that the expected ablation zones would extend into adjacent diaphragm, body wall, or bowel (non-target tissues). For experimental ablations, P407 (a hydrogel that transitions from liquid at room temperature to semi-solid at body temperature) was injected into the potential space between target and non-target tissues, and the presence of a gel barrier was verified on CT. No barrier was used for controls. MW ablation was performed at 65 W for 5 min. Thermal damage to target and non-target tissues was evaluated at dissection.ResultsAntennas were placed 7 ± 3 mm from the organ surface for both control and gel-protected ablations (p = 0.95). The volume of gel deployed was 49 ± 27 mL, resulting in a barrier thickness of 0.8 ± 0.5 cm. Ablations extended into non-target tissues in 12/14 control ablations (mean surface area = 3.8 cm{sup 2}) but only 4/14 gel-protected ablations (mean surface area = 0.2 cm{sup 2}; p = 0.0005). The gel barrier remained stable at the injection site throughout power delivery.ConclusionWhen used as a hydrodissection material, P407 protected non-targeted tissues and was successfully maintained at the injection site for the duration of power application. Continued investigations to aid clinical translation appear warranted.

  3. Subcellular analysis by laser ablation electrospray ionization mass spectrometry

    DOEpatents

    Vertes, Akos; Stolee, Jessica A; Shrestha, Bindesh

    2014-12-02

    In various embodiments, a method of laser ablation electrospray ionization mass spectrometry (LAESI-MS) may generally comprise micro-dissecting a cell comprising at least one of a cell wall and a cell membrane to expose at least one subcellular component therein, ablating the at least one subcellular component by an infrared laser pulse to form an ablation plume, intercepting the ablation plume by an electrospray plume to form ions, and detecting the ions by mass spectrometry.

  4. Fracture toughness of irradiated candidate materials for ITER first wall/blanket structures

    SciTech Connect

    Alexander, D.J.; Pawel, J.E.; Grossbeck, M.L.; Rowcliffe, A.F.; Shiba, Kiyoyuki

    1994-12-31

    Disk compact specimens of candidate materials for first wall/blanket structures in ITER have been irradiated to damage levels of about 3 dpa at nominal irradiation temperatures of either 90 or 250{degrees}C. These specimens have been tested over a temperature range from 20 to 250{degrees}C to determine J-integral values and tearing moduli. The results show that irradiation at these temperatures reduces the fracture toughness of austenitic stainless steels, but the toughness remains quite high. The toughness decreases as the test temperature increases. Irradiation at 250{degrees}C is more damaging than at 90{degrees}C, causing larger decreases in the fracture toughness. Ferritic-martensitic steels are embrittled by the irradiation, and show the lowest toughness at room temperature.

  5. Fracture toughness of irradiated candidate materials for ITER first wall/blanket structures: Summary report

    SciTech Connect

    Alexander, D.J.; Pawel, J.E.; Grossbeck, M.L.; Rowcliffe, A.F.

    1996-04-01

    Disk compact specimens of candidate materials for first wall/blanket structures in ITER have been irradiated to damage levels of about 3 dpa at nominal irradiation temperatures of either 90 250{degrees}C. These specimens have been tested over a temperature range from 20 to 250{degrees}C to determine J-integral values and tearing moduli. The results show that irradiation at these temperatures reduces the fracture toughness of austenic stainless steels, but the toughness remains quite high. The toughness decreases as the temperature increases. Irradiation at 250{degrees}C is more damaging that at 90{degrees}C, causing larger decreases in the fracture toughness. The ferritic-martensitic steels HT-9 and F82H show significantly greater reductions in fracture toughness that the austenitic stainless steels.

  6. [The Interaction of Oil Microcapsule Wall Materials between Whey Protein and Acacia].

    PubMed

    Shi, Yan; Li, Ru-yi; Wang, Hui; Li, Qian; Li, De-jun; Tu, Zong-cai

    2015-03-01

    The interaction between whey protein and acacia which were used as wall material was studied on the formation of the oils microcapsules by the FTIR Spectroscopy and Computer Aided Analysis. The results indicated that whey protein changed obviously in amide A and amide I by high pressured homogenization and spray-drying. The amide A moved from 3 406.5 cm(-1) to 3 425.4 cm(-1) which was possibly due to covalent cross-linking between whey protein and acacia. Furthermore the amide I moved from 1 648.6 cm(-1) to 1 654.7 cm(-1) for intramolecular hydrogen bonding of protein had been weaken. After Gaussian fitting on amide I , it was found that the content of secondary structure of α-helix content and β-folding in whey protein reduced from 19.55% to 17.50% and from 30.59% to 25.63%, respectively. This suggests that protein intramolecular hydrogen bonding force was abated, resulting in abating the rigid structure of the protein molecules and enhancing of the toughness structure. The protein molecules showed some flexibility. The result of SDS-PAGE electrophoresis showed that whey protein--gum Arabic complexes produced covalent products in larger molecular weight. During the spray-drying process, covalent cross-linking produced between whey protein and gum Arabic which improved emulsifying activity of the complex whey protein and gum Arabic produced covalent cross-linking and improved the complex emulsifying activity. Observing the surface structure of the fish oil microcapsule by SEM, the compound of whey protein and acacia as wall material was proved better toughness, less micropore, and more compact structure. PMID:26117866

  7. Multi-walled carbon nanotubes as electrode material for microbial fuel cells.

    PubMed

    Thepsuparungsikul, N; Phonthamachai, N; Ng, H Y

    2012-01-01

    The microbial fuel cell (MFC) is a novel and innovative technology that could allow direct harvesting of energy from wastewater through microbial activity with simultaneous oxidation of organic matter in wastewater. Among all MFC parts, electrode materials play a crucial role in electricity generation. A variety of electrode materials have been used, including plain graphite, carbon paper and carbon cloth. However, these electrode materials generated only limited electricity or power. Recently, many research studies have been conducted on carbon nanotubes (CNTs) because of their unique physical and chemical properties that include high conductivity, high surface area, corrosion resistance, and electrochemical stability. These properties make them extremely attractive for fabricating electrodes and catalyst supports. In this study, CNT-based electrodes had been developed to improve MFC performance in terms of electricity generation and treatment efficiency. Multi-walled carbon nanotubes (MWCNTs) with carboxyl groups have been employed to fabricate electrodes for single-chamber air-cathode MFCs. The quality of the prepared MWCNTs-based electrodes was evaluated by morphology, electrical conductivity and specific surface area using a field emission scanning electron microscope, four-probe method and Brunauer-Emmerr-Teller method, respectively. The performance of MFCs equipped with MWCNT-based electrodes was evaluated by chemical analysis and electrical monitoring and calculation. In addition, the performance of these MFCs, using MWCNTs as electrodes, was compared against that using commercial carbon cloth. PMID:22437017

  8. Nanometer-scale ablation using focused, coherent extreme ultraviolet/soft x-ray light

    DOEpatents

    Menoni, Carmen S.; Rocca, Jorge J.; Vaschenko, Georgiy; Bloom, Scott; Anderson, Erik H.; Chao, Weilun; Hemberg, Oscar

    2011-04-26

    Ablation of holes having diameters as small as 82 nm and having clean walls was obtained in a poly(methyl methacrylate) on a silicon substrate by focusing pulses from a Ne-like Ar, 46.9 nm wavelength, capillary-discharge laser using a freestanding Fresnel zone plate diffracting into third order is described. Spectroscopic analysis of light from the ablation has also been performed. These results demonstrate the use of focused coherent EUV/SXR light for the direct nanoscale patterning of materials.

  9. 230Th/U dating of Last Interglacial brain corals from Bonaire (southern Caribbean) using bulk and theca wall material

    NASA Astrophysics Data System (ADS)

    Obert, J. Christina; Scholz, Denis; Felis, Thomas; Brocas, William M.; Jochum, Klaus P.; Andreae, Meinrat O.

    2016-04-01

    We compared the suitability of two skeletal materials of the Atlantic brain coral Diploria strigosa for 230Th/U-dating: the commonly used bulk material comprising all skeletal elements and the denser theca wall material. Eight fossil corals of presumably Last Interglacial age from Bonaire, southern Caribbean Sea, were investigated, and several sub-samples were dated from each coral. For four corals, both the ages and the activity ratios of the bulk material and theca wall agree within uncertainty. Three corals show significantly older ages for their bulk material than for their theca wall material as well as substantially elevated 232Th content and (230Th/238U) ratios. The bulk material samples of another coral show younger ages and lower (230Th/238U) ratios than the corresponding theca wall samples. This coral also contains a considerable amount of 232Th. The application of the available open-system models developed to account for post-depositional diagenetic effects in corals shows that none of the models can successfully be applied to the Bonaire corals. The most likely explanation for this observation is that the assumptions of the models are not fulfilled by our data set. Comparison of the theca wall and bulk material data enables us to obtain information about the open-system processes that affected the corals. The corals showing apparently older ages for their bulk material were probably affected by contamination with a secondary (detrital) phase. The most likely source of the detrital material is carbonate sand. The higher (230Th/232Th) ratio of this material implies that detrital contamination would have a much stronger impact on the ages than a contaminant with a bulk Earth (230Th/232Th) ratio and that the threshold for the commonly applied 232Th reliability criterion would be much lower than the generally used value of 1 ng g-1. The coral showing apparently younger ages for its bulk material was probably influenced by more than one diagenetic process. A

  10. The physicochemical properties of microwave-assisted encapsulated anthocyanins from Ipomoea batatas as affected by different wall materials

    PubMed Central

    Mohd Nawi, Norazlina; Muhamad, Ida Idayu; Mohd Marsin, Aishah

    2015-01-01

    This study focuses on the impact of different wall materials on the physicochemical properties of microwave-assisted encapsulated anthocyanins from Ipomoea batatas. Using the powder characterization technique, purple sweet potato anthocyanin (PSPAs) powders were analysed for moisture content, water activity, dissolution time, hygroscopicity, color and morphology. PSPAs were produced using different wall materials: maltodextrin (MD), gum arabic (GA) and a combination of gum arabic and maltodextrin (GA + MD) at a 1:1 ratio. Each of the wall materials was homogenized to the core material at a core/wall material ratio of 5 and were microencapsulated by microwave-assisted drying at 1100 W. Results indicated that encapsulated powder with the GA and MD combination presented better quality of powder with the lowest value of moisture content and water activity. With respect to morphology, the microcapsule encapsulated with GA + MD showed several dents in coating surrounding its core material, whereas other encapsulated powders showed small or slight dents entrapped onto the bioactive compound. Colorimetric analysis showed changes in values of L, a*, b*, hue and chroma in the reconstituted powder compared to the initial powder. PMID:25838887

  11. Behavior of thin-walled beams made of advanced composite materials and incorporating non-classical effects

    NASA Astrophysics Data System (ADS)

    Librescu, Liviu; Song, Ohseop

    1991-11-01

    Several results concerning the refined theory of thin-walled beams of arbitrary closed cross-section incorporating nonclassical effects are presented. These effects are related both with the exotic properties characterizing the advanced composite material structures and the nonuniform torsional model. A special case of the general equations is used to study several problems of cantilevered thin-walled beams and to assess the influence of the incorporated effects. The results presented in this paper could be useful toward a more rational design of aeronautical or aerospace constructions, as well as of helicopter or tilt rotor blades constructed of advanced composite materials.

  12. Investigation of oxidation resistance of carbon based first-wall liner materials of fusion reactors

    NASA Astrophysics Data System (ADS)

    Moormann, R.; Hinssen, H. K.; Krüssenberg, A.-K.; Stauch, B.; Wu, C. H.

    1994-09-01

    One important aspect in selection of carbon based first-wall liner materials in fusion reactors is a sufficient oxidation resistance against steam and oxygen; this is because during accidents like loss of coolant into vacuum or loss of vacuum these oxidizing media can enter the vacuum vessel and may cause some corrosion of carbon followed by release of adsorbed tritium; in addition other consequences of oxidation like formation of burnable gases and their explosions have to be examined. Based on extensive experience on nuclear graphite oxidation in HTRs KFA has started in cooperation with NET some experimental investigations on oxidation of fusion reactor carbons. Results of first experiments on CFCs, Ti- and Si-doped carbons and graphites in steam (1273-1423 K) and oxygen (973 K) are reported. It was found that most materials have a similar reactivity as HTR nuclear graphites (which is much smaller than those of usual technical carbons); Si-doped CFCs however have a remarkably better oxidation resistance than those, which is probably due to the formation of a protecting layer of SiO 2. The measured kinetic data will be used in safety analyses for above mentioned accidents.

  13. Volatile Retention and Morphological Properties of Microencapsulated Tributyrin Varied by Wall Material and Drying Method.

    PubMed

    Donovan, Joseph D; Cadwallader, Keith R; Lee, Youngsoo

    2016-03-01

    Butyric acid is an important short-chain fatty acid for intestinal health and has been shown to improve certain intestinal disease states. A triglyceride containing 3 butyric acid esters, tributyrin (TB) can serve as a source of butyric acid; however, the need to target intestinal delivery and mitigate unpleasant sensory qualities has limited its use in food. Microencapsulation, the entrapment of one or more cores within a matrix, may provide a solution to the aforementioned challenge. This research primarily focused on the influence of (1) wall material: whey and soy protein isolate (WPI and SPI, respectively) and gamma-cyclodextrin (GCD), (2) wall additives: inulin of varying chain length, and (3) processing method: spray or oven drying (SD or OD, respectively) on the morphological properties and volatile retention of TB within microcapsules. SPI-based microcapsules retained significantly less (P < 0.001) TB compared to WPI-based microcapsules as measured by gas chromatography. The inclusion of inulin in the SD WPI-based microcapsules increased (P < 0.001) TB retention over WPI-based microcapsules without inulin. Inulin inclusion into WPI-based microcapsules resulted in a smoother, minimally-dented, circular morphology as compared to noninulin containing WPI-based microcapsules as shown by scanning electron microscopy. GCD and TB OD microcapsules retained more (P < 0.001) TB (94.5% ± 1.10%) than all other WPI, WPI-inulin, and GCD TB SD microcapsules. When spray dried, the GCD-based microcapsules exhibited (P < 0.001) TB retention than all other microcapsules, indicating the GCD may be unsuitable for spray drying. These findings demonstrate that microencapsulated TB in GCD can lead to minimal TB losses during processing that could be utilized in functional food applications for intestinal health. PMID:26878682

  14. Preliminary characterisation of new glass reference materials (GSA-1G, GSC-1G, GSD-1G and GSE-1G) by laser ablation-inductively coupled plasma-mass spectrometry using 193 nm, 213 nm and 266 nm wavelengths

    USGS Publications Warehouse

    Guillong, M.; Hametner, K.; Reusser, E.; Wilson, S.A.; Gunther, D.

    2005-01-01

    New glass reference materials GSA-1G, GSC-1G, GSD-1G and GSE-1G have been characterised using a prototype solid state laser ablation system capable of producing wavelengths of 193 nm, 213 nm and 266 nm. This system allowed comparison of the effects of different laser wavelengths under nearly identical ablation and ICP operating conditions. The wavelengths 213 nm and 266 nm were also used at higher energy densities to evaluate the influence of energy density on quantitative analysis. In addition, the glass reference materials were analysed using commercially available 266 nm Nd:YAG and 193 nm ArF excimer lasers. Laser ablation analysis was carried out using both single spot and scanning mode ablation. Using laser ablation ICP-MS, concentrations of fifty-eight elements were determined with external calibration to the NIST SRM 610 glass reference material. Instead of applying the more common internal standardisation procedure, the total concentration of all element oxide concentrations was normalised to 100%. Major element concentrations were compared with those determined by electron microprobe. In addition to NIST SRM 610 for external calibration, USGS BCR-2G was used as a more closely matrix-matched reference material in order to compare the effect of matrix-matched and non matrix-matched calibration on quantitative analysis. The results show that the various laser wavelengths and energy densities applied produced similar results, with the exception of scanning mode ablation at 266 nm without matrix-matched calibration where deviations up to 60% from the average were found. However, results acquired using a scanning mode with a matrix-matched calibration agreed with results obtained by spot analysis. The increased abundance of large particles produced when using a scanning ablation mode with NIST SRM 610, is responsible for elemental fractionation effects caused by incomplete vaporisation of large particles in the ICP.

  15. Microwave Ablation Compared with Radiofrequency Ablation for Breast Tissue in an Ex Vivo Bovine Udder Model

    SciTech Connect

    Tanaka, Toshihiro; Westphal, Saskia; Isfort, Peter; Braunschweig, Till; Penzkofer, Tobias Bruners, Philipp; Kichikawa, Kimihiko; Schmitz-Rode, Thomas Mahnken, Andreas H.

    2012-08-15

    Purpose: To compare the effectiveness of microwave (MW) ablation with radiofrequency (RF) ablation for treating breast tissue in a nonperfused ex vivo model of healthy bovine udder tissue. Materials and Methods: MW ablations were performed at power outputs of 25W, 35W, and 45W using a 915-MHz frequency generator and a 2-cm active tip antenna. RF ablations were performed with a bipolar RF system with 2- and 3-cm active tip electrodes. Tissue temperatures were continuously monitored during ablation. Results: The mean short-axis diameters of the coagulation zones were 1.34 {+-} 0.14, 1.45 {+-} 0.13, and 1.74 {+-} 0.11 cm for MW ablation at outputs of 25W, 35W, and 45W. For RF ablation, the corresponding values were 1.16 {+-} 0.09 and 1.26 {+-} 0.14 cm with electrodes having 2- and 3-cm active tips, respectively. The mean coagulation volumes were 2.27 {+-} 0.65, 2.85 {+-} 0.72, and 4.45 {+-} 0.47 cm{sup 3} for MW ablation at outputs of 25W, 35W, and 45W and 1.18 {+-} 0.30 and 2.29 {+-} 0.55 cm{sup 3} got RF ablation with 2- and 3-cm electrodes, respectively. MW ablations at 35W and 45W achieved significantly longer short-axis diameters than RF ablations (P < 0.05). The highest tissue temperature was achieved with MW ablation at 45W (P < 0.05). On histological examination, the extent of the ablation zone in MW ablations was less affected by tissue heterogeneity than that in RF ablations. Conclusion: MW ablation appears to be advantageous with respect to the volume of ablation and the shape of the margin of necrosis compared with RF ablation in an ex vivo bovine udder.

  16. Dual beam optical system for pulsed laser ablation film deposition

    DOEpatents

    Mashburn, D.N.

    1996-09-24

    A laser ablation apparatus having a laser source outputting a laser ablation beam includes an ablation chamber having a sidewall, a beam divider for dividing the laser ablation beam into two substantially equal halves, and a pair of mirrors for converging the two halves on a surface of the target from complementary angles relative to the target surface normal, thereby generating a plume of ablated material emanating from the target. 3 figs.

  17. Aluminum 2219-T87 and 5456-H116 - A comparative study of spacecraft wall materials in dual-wall structures under hypervelocity impact

    NASA Technical Reports Server (NTRS)

    Schonberg, William P.

    1992-01-01

    All earth-orbiting spacecraft are susceptible to high-speed impacts by pieces of orbital debris. To prevent mission failure and possibly loss of life, protection against perforation by high-speed orbital debris particles must be included in the spacecraft design. Although any number of materials can be used to manufacture perforation-resistant structures, aluminum is often used in such systems because of its relatively high strength-to-weight ratio. This paper presents the results of a study in which the high speed impact response characteristics of dual-wall structures made from two different aluminum alloys were analyzed to determine which alloy would be more suitable for use in a perforation-resistant dual-wall structural system that is to be exposed to the orbital debris environment. Impact response characteristics were obtained numerically and experimentally. At impact speeds below 7 km/s, it was found that the two aluminum alloys considered contributed similar levels of perforation resistance; at speeds in excess of 7 km/s, aluminum 2219-T87 was superior to aluminum 5546-H116 in preventing perforation of dual-wall structural systems.

  18. Aluminum 2219-T87 and 5456-H116 - A comparative study of spacecraft wall materials in dual-wall structures under hypervelocity impact

    NASA Astrophysics Data System (ADS)

    Schonberg, William P.

    1992-11-01

    All earth-orbiting spacecraft are susceptible to high-speed impacts by pieces of orbital debris. To prevent mission failure and possibly loss of life, protection against perforation by high-speed orbital debris particles must be included in the spacecraft design. Although any number of materials can be used to manufacture perforation-resistant structures, aluminum is often used in such systems because of its relatively high strength-to-weight ratio. This paper presents the results of a study in which the high speed impact response characteristics of dual-wall structures made from two different aluminum alloys were analyzed to determine which alloy would be more suitable for use in a perforation-resistant dual-wall structural system that is to be exposed to the orbital debris environment. Impact response characteristics were obtained numerically and experimentally. At impact speeds below 7 km/s, it was found that the two aluminum alloys considered contributed similar levels of perforation resistance; at speeds in excess of 7 km/s, aluminum 2219-T87 was superior to aluminum 5546-H116 in preventing perforation of dual-wall structural systems.

  19. Electromechanical Behavior of Chemically Reduced Graphene Oxide and Multi-walled Carbon Nanotube Hybrid Material

    NASA Astrophysics Data System (ADS)

    Benchirouf, Abderrahmane; Müller, Christian; Kanoun, Olfa

    2016-01-01

    In this paper, we propose strain-sensitive thin films based on chemically reduced graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) without adding any further surfactants. In spite of the insulating properties of the thin-film-based GO due to the presence functional groups such as hydroxyl, epoxy, and carbonyl groups in its atomic structure, a significant enhancement of the film conductivity was reached by chemical reduction with hydro-iodic acid. By optimizing the MWCNT content, a significant improvement of electrical and mechanical thin film sensitivity is realized. The optical properties and the morphology of the prepared thin films were studied using ultraviolet-visible spectroscopy (UV-Vis) and scanning electron microscope (SEM). The UV-Vis spectra showed the ability to tune the band gap of the GO by changing the MWCNT content, whereas the SEM indicated that the MWCNTs were well dissolved and coated by the GO. Investigations of the piezoresistive properties of the hybrid nanocomposite material under mechanical load show a linear trend between the electrical resistance and the applied strain. A relatively high gauge factor of 8.5 is reached compared to the commercial metallic strain gauges. The self-assembled hybrid films exhibit outstanding properties in electric conductivity, mechanical strength, and strain sensitivity, which provide a high potential for use in strain-sensing applications.

  20. Structure, physicochemical properties and in vitro fermentation of enzymatically degraded cell wall materials from apples.

    PubMed

    Förster, S; Dongowski, G; Kunzek, H

    2002-06-01

    Cell wall materials (CWM) prepared from apple parenchyma tissue by treatment with commercial enzymes for maceration, mash fermentation and liquefaction were characterised with regard to their composition and structure as well as their physicochemical and physiological properties. Increasing enzymatic degradation of the CWM resulted in growing loss of the pectin matrix, decreasing porosity as well as increasing particle aggregation. Due to these structural alterations the water binding, the viscoelastic properties of the CWM-water-suspensions and the in vitro fermentation, forming short chain fatty acids, were reduced. The investigations showed that interrelations exist between enzymatic treatment and changes of (i) structure and state of matrices (evaluated by means of thermal analysis), (ii) physicochemical properties and (iii) physiological properties. So the application of liquefying enzymes can lead to a complete removal of the pectin matrix, causing an essentially improved thermal stability of the CWM preparation, but strongly reduced water binding and reduced structure-forming properties into the CWM-water-suspensions. The formation of short-chain fatty acids during in vitro fermentation of the CWM preparations by fresh human faeces flora depended on the portion and the state of the pectin matrix and the cellulose network, respectively. PMID:12108214

  1. Electromechanical Behavior of Chemically Reduced Graphene Oxide and Multi-walled Carbon Nanotube Hybrid Material.

    PubMed

    Benchirouf, Abderrahmane; Müller, Christian; Kanoun, Olfa

    2016-12-01

    In this paper, we propose strain-sensitive thin films based on chemically reduced graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) without adding any further surfactants. In spite of the insulating properties of the thin-film-based GO due to the presence functional groups such as hydroxyl, epoxy, and carbonyl groups in its atomic structure, a significant enhancement of the film conductivity was reached by chemical reduction with hydro-iodic acid. By optimizing the MWCNT content, a significant improvement of electrical and mechanical thin film sensitivity is realized. The optical properties and the morphology of the prepared thin films were studied using ultraviolet-visible spectroscopy (UV-Vis) and scanning electron microscope (SEM). The UV-Vis spectra showed the ability to tune the band gap of the GO by changing the MWCNT content, whereas the SEM indicated that the MWCNTs were well dissolved and coated by the GO. Investigations of the piezoresistive properties of the hybrid nanocomposite material under mechanical load show a linear trend between the electrical resistance and the applied strain. A relatively high gauge factor of 8.5 is reached compared to the commercial metallic strain gauges. The self-assembled hybrid films exhibit outstanding properties in electric conductivity, mechanical strength, and strain sensitivity, which provide a high potential for use in strain-sensing applications. PMID:26732277

  2. Thermographic imaging of material loss in boiler water-wall tubing by application of scanning line source

    NASA Astrophysics Data System (ADS)

    Cramer, K. Elliott; Winfree, William P.

    2000-06-01

    Localized wall thinning due to corrosion in utility boiler water-wall tubing is a significant inspection concern for boiler operators. Historically, conventional ultrasonics has been used for inspection of these tubes. This technique has proven to be very manpower and time intensive. This has resulted in a 'spot check' approach to inspections, documenting thickness measurements over a relatively small percentage of the total boiler wall area. NASA Langley Research Center has developed a thermal NDE technique designed to image and quantitatively characterize the amount of material thinning present in steel tubing. The technique involves the movement of a thermal line source across the outer surface of the tubing followed by an infrared imager at a fixed distance behind the line source. Quantitative images of the material loss due to corrosion are reconstructed from measurements of the induced surface temperature variations. This paper will present a discussion of the development of the thermal imaging system as well as the techniques used to reconstruct images of flaws. The application of the thermal line source coupled with the analysis technique represents a significant improvement in the inspection speed for large structures such as boiler water-walls. A theoretical basis for the technique will be presented which explains the quantitative nature of the technique. Further, a dynamic calibration system will be presented for the technique that allows the extraction of thickness information from the temperature data. Additionally, the results of applying this technology to actual water-wall tubing samples and in situ inspections will be presented.

  3. Thermographic Imaging of Material Loss in Boiler Water-Wall Tubing by Application of Scanning Line Source

    NASA Technical Reports Server (NTRS)

    Cramer, K. Elliott; Winfree, William P.

    2000-01-01

    Localized wall thinning due to corrosion in utility boiler water-wall tubing is a significant inspection concern for boiler operators. Historically, conventional ultrasonics has been used for inspection of these tubes. This technique has proven to be very manpower and time intensive. This has resulted in a spot check approach to inspections, documenting thickness measurements over a relatively small percentage of the total boiler wall area. NASA Langley Research Center has developed a thermal NDE technique designed to image and quantitatively characterize the amount of material thinning present in steel tubing. The technique involves the movement of a thermal line source across the outer surface of the tubing followed by an infrared imager at a fixed distance behind the line source. Quantitative images of the material loss due to corrosion are reconstructed from measurements of the induced surface temperature variations. This paper will present a discussion of the development of the thermal imaging system as well as the techniques used to reconstruct images of flaws. The application of the thermal line source coupled with the analysis technique represents a significant improvement in the inspection speed for large structures such as boiler water-walls. A theoretical basis for the technique will be presented which explains the quantitative nature of the technique. Further, a dynamic calibration system will be presented for the technique that allows the extraction of thickness information from the temperature data. Additionally, the results of applying this technology to actual water-wall tubing samples and in situ inspections will be presented.

  4. Laser ablation based fuel ignition

    DOEpatents

    Early, J.W.; Lester, C.S.

    1998-06-23

    There is provided a method of fuel/oxidizer ignition comprising: (a) application of laser light to a material surface which is absorptive to the laser radiation; (b) heating of the material surface with the laser light to produce a high temperature ablation plume which emanates from the heated surface as an intensely hot cloud of vaporized surface material; and (c) contacting the fuel/oxidizer mixture with the hot ablation cloud at or near the surface of the material in order to heat the fuel to a temperature sufficient to initiate fuel ignition. 3 figs.

  5. Laser ablation based fuel ignition

    DOEpatents

    Early, James W.; Lester, Charles S.

    1998-01-01

    There is provided a method of fuel/oxidizer ignition comprising: (a) application of laser light to a material surface which is absorptive to the laser radiation; (b) heating of the material surface with the laser light to produce a high temperature ablation plume which emanates from the heated surface as an intensely hot cloud of vaporized surface material; and (c) contacting the fuel/oxidizer mixture with the hot ablation cloud at or near the surface of the material in order to heat the fuel to a temperature sufficient to initiate fuel ignition.

  6. Investigation of molybdenum-44.5%rhenium as cell wall material in an AMTEC based space power system

    NASA Astrophysics Data System (ADS)

    Kramer, Daniel P.; Ruhkamp, Joe D.; McNeil, Dennis C.; Howell, Edwin I.; Williams, Melvin K.; McDougal, James R.; Booher, Robert A.

    2000-01-01

    A new generation of radioisotope space power systems based on AMTEC (Alkali Metal Thermal to Electrical Conversion) technology is presently being developed. The future application of this technology, as the electrical power system for outer planet deep space missions, is ultimately dependent on it being robust enough to withstand the mission's operational environments (high temperatures, dynamic loadings, long mission durations etc). One of the critical material selections centers on the cell wall whose physical and chemical properties must provide it with sufficient strength and material compatibility to successfully complete the mission. Niobium-1%zirconium has been selected as the baseline cell wall material with a molybdenum/rhenium alloy being the cell wall backup material. While these refractory materials have been commercially available for a number of years, several of their physical and mechanical properties have not been completely characterized especially within the expected operating parameters of an AMTEC based space power system. Additional characterization of the selected refractory alloys was initiated by fabricating mechanical test specimens out of ~0.5 mm (0.020'') thick sheets of material. Test specimens were heat treated at 1073K and 1198K for up to 150 hours under an argon cover gas containing small concentrations of oxygen. Room temperature and high temperature (1073K/1198K) mechanical tests were performed to determine the effect of time, temperature, and atmosphere on the mechanical properties of the refractory alloys. In addition, since the fabrication of AMTEC cell walls requires the welding of sheet material into a cylindrical shape, preliminary electron beam welding studies were performed. Comparison of the various test results obtained on Mo-44.5%Re and Nb-1%Zr samples are discussed. .

  7. X-ray ablation measurements and modeling for ICF applications

    SciTech Connect

    Anderson, A.T.

    1996-09-01

    X-ray ablation of material from the first wall and other components of an ICF (Inertial Confinement Fusion) chamber is a major threat to the laser final optics. Material condensing on these optics after a shot may cause damage with subsequent laser shots. To ensure the successful operation of the ICF facility, removal rates must be predicted accurately. The goal for this dissertation is to develop an experimentally validated x-ray response model, with particular application to the National Ignition Facility (NIF). Accurate knowledge of the x-ray and debris emissions from ICF targets is a critical first step in the process of predicting the performance of the target chamber system. A number of 1-D numerical simulations of NIF targets have been run to characterize target output in terms of energy, angular distribution, spectrum, and pulse shape. Scaling of output characteristics with variations of both target yield and hohlraum wall thickness are also described. Experiments have been conducted at the Nova laser on the effects of relevant x-ray fluences on various materials. The response was diagnosed using post-shot examinations of the surfaces with scanning electron microscope and atomic force microscope instruments. Judgments were made about the dominant removal mechanisms for each material. Measurements of removal depths were made to provide data for the modeling. The finite difference ablation code developed here (ABLATOR) combines the thermomechanical response of materials to x-rays with models of various removal mechanisms. The former aspect refers to energy deposition in such small characteristic depths ({approx} micron) that thermal conduction and hydrodynamic motion are significant effects on the nanosecond time scale. The material removal models use the resulting time histories of temperature and pressure-profiles, along with ancillary local conditions, to predict rates of surface vaporization and the onset of conditions that would lead to spallation.

  8. Laser Ablation of Alumina in Water

    SciTech Connect

    Musaev, O.; Midgley, A; Wrobel, J; Kruger, M

    2010-01-01

    Bulk {alpha}-alumina immersed in distilled water was ablated by pulsed UV laser radiation. The resulting colloidal solution contained micron and submicron size particles. X-ray diffraction and Raman spectra of the ablated and original material are similar. Hence, most of the ablated material is {alpha}-alumina. From transmission electron microscope images, most of the submicron and all of the micron-sized particles have sharp edges and do not have spherical shapes, indicating that the dominant ablation mechanism is due to crack propagation. Some spherical particles of diameter less than 100 nm are observed, indicating that they were formed from the liquid state.

  9. Left Atrial Anatomy Relevant to Catheter Ablation

    PubMed Central

    Sánchez-Quintana, Damián; Cabrera, José Angel; Saremi, Farhood

    2014-01-01

    The rapid development of interventional procedures for the treatment of arrhythmias in humans, especially the use of catheter ablation techniques, has renewed interest in cardiac anatomy. Although the substrates of atrial fibrillation (AF), its initiation and maintenance, remain to be fully elucidated, catheter ablation in the left atrium (LA) has become a common therapeutic option for patients with this arrhythmia. Using ablation catheters, various isolation lines and focal targets are created, the majority of which are based on gross anatomical, electroanatomical, and myoarchitectual patterns of the left atrial wall. Our aim was therefore to review the gross morphological and architectural features of the LA and their relations to extracardiac structures. The latter have also become relevant because extracardiac complications of AF ablation can occur, due to injuries to the phrenic and vagal plexus nerves, adjacent coronary arteries, or the esophageal wall causing devastating consequences. PMID:25057427

  10. Specific bloch wall area of tape wound cores of amorphous and crystalline material

    NASA Astrophysics Data System (ADS)

    Winner, H.; Grosse-Nobis, W.; Reinhardt, M.

    1984-02-01

    At low magnetizing frequencies not the total available domain wall area is instantaneously in motion. A method is presented to separate the simultaneously irreversibly moved domain wall area (specific area Sirr) from that wall area which is elastically attached at pinning centres. For tape wound cores of iron silicon and of metallic glass Sirr was determined as function of the magnetizing frequency by measuring the complex core impedance and applying a simple domain model. At very low magnetizing frequencies fm<10 -2s -1 the quantity Sirr is found to be approximately proportional to f0.8m.

  11. Investigation of gelatin/multi-walled carbon nanotube nanocomposite films as packaging materials

    PubMed Central

    Kavoosi, Gholamreza; Dadfar, Seyed Mohammad Mahdi; Dadfar, Seyed Mohammad Ali; Ahmadi, Farhad; Niakosari, Mehrdad

    2014-01-01

    Gelatin composite films were prepared from gelatin solutions (10% w/v) containing multi-walled carbon nanotubes (MWCNT, 0.5, 1, 1.5, and 2% w/w gelatin) as nanofiller. The water solubility, water swelling, water uptake, water vapor permeability (WVP), mechanical, and antibacterial properties of the films were examined. Water solubility, water swelling, water uptake, and WVP for gelatin films were 45 ± 1%, 821 ± 42%, 45 ± 1.1%, and 0.4 ± 0.022 g mm/m2 kPa h, respectively. Incorporation of MWCNT caused a significant decrease in water solubility, water swelling, water uptake, and WVP. Gelatin/MWCNT films containing 1–1.5% MWCNT showed the lowest water vapor transmission. Tensile strength, elongation at break, and Young's modulus for gelatin films were 13.4 ± 1.2 MPa, 95 ± 5%, and 45.4 ± 7 MPa, respectively. Incorporation of MWCNT caused a significant increase in tensile strength and decrease in the elongation at break. The largest mechanical strength was found at 1.5% MWCNT. All gelatin/MWCNT films showed significant antibacterial activities against both gram-positive and gram-negative bacteria. Our results suggest that the gelatin/MWCNT composites films could be used as a very attractive alternative to traditional materials for different biomedical and food applications. PMID:24804066

  12. Overall evaluation study for isotropic graphite as fusion first wall material in japan

    NASA Astrophysics Data System (ADS)

    Yamashina, Toshiro; Hino, Tomoaki

    1989-04-01

    Isotropie graphite has been widely used as first wall material in present large fusion devices. For isotropic graphites with different properties, however, overall evaluations with respect to vacuum engineering properties, thermal-mechanical properties and interations with plasmas have not been performed systematically. In 1986, under the support of the Ministry of Education, Science and Culture, the "Graphite Project Team" was organized. Fifteen institutions participated in this project and eighteen isotropic graphites supplied from seven graphite manufactures of Japan were studied as "common samples". From each company, both high- and low-density graphites were supplied since it was presumed that the vacuum engineering and thermal-mechanical properties depended on the density. During an approximately two years research period, we have obtained several interesting results on surface roughness, gas desorption, hydrogen permeation, failure due to heat load and fracture toughness. It was found that the vacuum engineering properties such as the surface area, the gas desorption and the hydrogen permeation depended significanly on the pore structure of the graphite. The surface area increased with the bulk density and the hydrogen permeation rate decreased with the bulk density. The gas desorption was very small for the graphite baked in vacuum. Treated in the same way, the amount of gas released from low-density graphite was smaller. The ash content of the graphite could be reduced to ppm levels by halogen gas treatment. The heat load experiments showed that most of the graphites failed at roughly the same heat load. The measured value of the fracture toughness was approximately the same. The change of the surface morphology by hydrogen ion irradiation and the desorption of trapped ions are also discussed.

  13. Quantitative analysis of trace elements in environmental powders with laser ablation inductively coupled mass spectrometry using non-sample-corresponding reference materials for signal evaluation

    NASA Astrophysics Data System (ADS)

    Bauer, Gerald; Limbeck, Andreas

    2015-11-01

    Laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS) is an attractive alternative to traditional procedures for the analysis of environmental samples (i.e., conventional liquid measurement after sample digestion). However, for accurate quantification, certified reference materials (CRM) are necessary which match the composition of the sample and include all elements of interest at the required concentration levels. The limited availability of appropriate CRMs hampers therefore substantial application. In this work, an LA-ICP-MS procedure allowing for accurate determination of trace element contents in powdered environmental samples is presented. For LA-ICP-MS analysis, the samples are mixed with an internal standard (silver oxide) and a binder (sodium tetra borate) and subsequently pressed to pellets. Quantification is accomplished using a calibration function determined using CRMs with varying matrix composition and analyte content, pre-treated and measured in the same way as the samples. With this approach, matrix-induced ablation differences resulting from varying physical/chemical properties of the individual CRMs could be compensated. Furthermore, ICP-related matrix-effects could be minimized using collision/reaction cell technology. Applicability of the procedure has been demonstrated by assessment of Cd, Cu, Ni, and Zn in four different environmental CRMs (NIST SRM1648a (urban particulate matter), NIST SRM2709 (San Joaquin Soil), BCR144 (sewage sludge), and BCR723 (road dust)). Signal evaluation was performed by alternative use of three CRMs for calculation of the calibration function whereas the remaining fourth CRM acted as unknown sample, resulting in a good agreement between measured and certified values for all elements and reference materials.

  14. Pedestal and edge localized mode characteristics with different first wall materials and nitrogen seeding in ASDEX Upgrade

    NASA Astrophysics Data System (ADS)

    Schneider, P. A.; Barrera Orte, L.; Burckhart, A.; Dunne, M. G.; Fuchs, C.; Gude, A.; Kurzan, B.; Suttrop, W.; Wolfrum, E.; the ASDEX Upgrade Team

    2015-01-01

    A comparison of ASDEX Upgrade (AUG) discharges performed with carbon and the full tungsten wall shows that the pedestal performance at low triangularity is not altered without gas puffing. The pedestal electron pressure is the same for both wall materials as is the confinement. With the tungsten wall the natural density is higher even without an additional gas puff. In typical operation with gas puffing the density is again higher in tungsten. This results in a higher collisionality with the tungsten wall. Pedestal pressure and plasma confinement, however, are not degraded until very large amounts of deuterium are puffed. The edge localized mode (ELM) crash in typical AUG discharges is observed to be composed of two independent phases. This is observed for both the carbon and the tungsten wall. The 1st phase of the crash is unaffected by scans of the plasma parameters as long as the pedestal pressure remains constant. The duration of the 2nd phase is strongly anti-correlated with the separatrix density and can be suppressed by the application of nitrogen seeding for divertor cooling. A consistent explanation for the two phases of the ELM crash does not seem possible when considering only the pre-ELM pedestal profiles. The scrape off layer (SOL) plasma provides the necessary free parameter for a consistent explanation, indicating the importance of the SOL in understanding the ELM crash evolution.

  15. Analytical and numerical investigation of structural response of compliant wall materials, part 2

    NASA Technical Reports Server (NTRS)

    Balasubramanian, R.

    1978-01-01

    Theoretical analysis of an electrostatically driven wall system for a compliant wall drag reduction program is reported. The electrostatic wall system is capable of producing deflections of many orders greater than the wall thicknesses and at small wavelengths. An intermediate large response theory is used for structural analysis. The theoretical predictions are compared to bench test results, and good agreement between the two is obtained. The effects of aerodynamic loads and perturbation electric fields on the theoretical solutions are considered. It is shown that for very small wavelengths (lambda almost equals 2 mm) the aerodynamic effects can be estimated using potential theory without loss of accuracy, and the perturbation electric fields do not effect solutions as long as the deflections are less than one percent of the wavelength. Resonance effects for this type of structure are shown to be fairly small.

  16. A Numerical study of ablative flow driven by thermodynamics and kinetics

    NASA Astrophysics Data System (ADS)

    Crocker, Ryan; Dubief, Yves; White, Christopher

    2012-11-01

    The main focus of this research is to elucidate the relationship between ablative/erosive flows and their interaction with a spatially dynamic boundary conditions. The fluid-solid interface is described by a level-set (LS) approach, enabling efficient and accurate computation of wall-normal vectors and other geometrical properties. Boundary conditions at the interface are imposed using immersed boundary methods (IBM). Our LS/IBM ablation algorithm is able to simulate various ablation processes, in particular ablation by chemical reactions and phase-change. The momentum boundary conditions are handled through cut cell IBM applied implicitly. This method is fully mass conserving and eliminates issues with spurious pressure oscillations. Scalar boundary conditions are simulated with a form of the ghost fluid method, with known thermal and chemical physics, to interpolate values across the fluid/solid interface after they are decoupled. We will discuss two applications of this algorithm. The first is the simulation of an experiment of the oxidation of a carbon material at around 1000K conducted at NASA AMES. The second focuses on the interactions between heated wall-turbulence and a low-melting point material in collaboration with parallel experiments at University of New Hampshire. We gratefully acknowledge the financial support of NSF, grand No. CBET 0967857, and NASA, grant No. NNX11AM07A, and the computational support of the Vermont Advanced Computing Center at the University of Vermont.

  17. Femtosecond laser ablation of enamel

    NASA Astrophysics Data System (ADS)

    Le, Quang-Tri; Bertrand, Caroline; Vilar, Rui

    2016-06-01

    The surface topographical, compositional, and structural modifications induced in human enamel by femtosecond laser ablation is studied. The laser treatments were performed using a Yb:KYW chirped-pulse-regenerative amplification laser system (560 fs and 1030 nm) and fluences up to 14 J/cm2. The ablation surfaces were studied by scanning electron microscopy, grazing incidence x-ray diffraction, and micro-Raman spectroscopy. Regardless of the fluence, the ablation surfaces were covered by a layer of resolidified material, indicating that ablation is accompanied by melting of hydroxyapatite. This layer presented pores and exploded gas bubbles, created by the release of gaseous decomposition products of hydroxyapatite (CO2 and H2O) within the liquid phase. In the specimen treated with 1-kHz repetition frequency and 14 J/cm2, thickness of the resolidified material is in the range of 300 to 900 nm. The micro-Raman analysis revealed that the resolidified material contains amorphous calcium phosphate, while grazing incidence x-ray diffraction analysis allowed detecting traces of a calcium phosphate other than hydroxyapatite, probably β-tricalcium phosphate Ca3), at the surface of this specimen. The present results show that the ablation of enamel involves melting of enamel's hydroxyapatite, but the thickness of the altered layer is very small and thermal damage of the remaining material is negligible.

  18. The Pack Method for Compressive Tests of Thin Specimens of Materials Used in Thin-Wall Structures

    NASA Technical Reports Server (NTRS)

    Aitchison, C S; Tuckerman, L B

    1939-01-01

    The strength of modern lightweight thin-wall structures is generally limited by the strength of the compression members. An adequate design of these members requires a knowledge of the compressive stress-strain graph of the thin-wall material. The "pack" method was developed at the National Bureau of Standards with the support of the National Advisory Committee for Aeronautics to make possible a determination of compressive stress-strain graphs for such material. In the pack test an odd number of specimens are assembled into a relatively stable pack, like a "pack of cards." Additional lateral stability is obtained from lateral supports between the external sheet faces of the pack and outside reactions. The tests seems adequate for many problems in structural research.

  19. Excimer laser ablation of the lens.

    PubMed

    Nanevicz, T M; Prince, M R; Gawande, A A; Puliafito, C A

    1986-12-01

    Ablation of the bovine crystalline lens was studied using radiation from an excimer laser at four ultraviolet wave lengths as follows: 193 nm (argon fluoride), 248 nm (krypton fluoride), 308 nm (xenon chloride), and 351 nm (xenon fluoride). The ablation process was quantitated by measuring mass ablated with an electronic balance, and characterized by examining ablation craters with scanning electron microscopy. The highest ablation rate was observed at 248 nm with lower rates at 193 and 308 nm. No ablation was observed at 351 nm. Scanning electron microscopy revealed the smoothest craters at 193 nm while at 248 nm there was vacuolization in the crater walls and greater disruption of surrounding tissue. The craters made at 308 nm did not have as smooth a contour as the 193-nm lesions. The spectral absorbance of the bovine lens was calculated at the wavelengths used for ablation and correlated with ablation rates and thresholds. High peak-power, pulsed ultraviolet laser radiation may have a role in surgical removal of the lens. PMID:3789982

  20. Analytical and numerical investigation of structural response of compliant wall materials

    NASA Technical Reports Server (NTRS)

    Goglia, G. L.; Balasubramanian, R.

    1978-01-01

    Theoretical analysis of an electrostatically driven wall system for a compliant wall drag reduction program is reported. The electrostatic wall system is capable of producing deflections of many orders greater than the thicknesses and at small wavelengths. An intermediate large response theory was used for structural analysis. The theoretical predictions were compared to bench test results, and good agreement between the two was obtained. The effects of aerodynamic loads and perturbation electric fields on the theoretical solutions were considered. It was shown that for very small wavelengths (approximately 2mm) the aerodynamic effects can be estimated using potential theory without loss of accuracy, and the perturbation electric fields do not affect solutions as long as the deflections are less than one percent of the wavelength. Resonance effects for this type of structure were shown to be fairly small.

  1. Hyaluronic acid biodegradable material for reconstruction of vascular wall: a preliminary study in rats.

    PubMed

    Pandis, Laura; Zavan, Barbara; Bassetto, Franco; Ferroni, Letizia; Iacobellis, Laura; Abatangelo, Giovanni; Lepidi, Sandro; Cortivo, Roberta; Vindigni, Vincenzo

    2011-02-01

    The objective of this preliminary study was to develop a reabsorbable vascular patch that did not require in vitro cell or biochemical preconditioning for vascular wall repair. Patches were composed only of hyaluronic acid (HA). Twenty male Wistar rats weighing 250-350 g were used. The abdominal aorta was exposed and isolated. A rectangular breach (1 mm × 5 mm) was made on vessel wall and arterial defect was repaired with HA made patch. Performance was assessed at 1, 2, 4, 8, and 16 weeks after surgery by histology and immunohistochemistry. Extracellular matrix components were evaluated by molecular biological methods. After 16 weeks, the biomaterial was almost completely degraded and replaced by a neoartery wall composed of endothelial cells, smooth muscle cells, collagen, and elastin fibers organized in layers. In conclusion, HA patches provide a provisional three-dimensional support to interact with cells for the control of their function, guiding the spatially and temporally multicellular processes of artery regeneration. PMID:21268111

  2. Laser ablation studies of concrete

    SciTech Connect

    Savina, M.; Xu, Z.; Wang, Y.; Reed, C.; Pellin, M.

    1999-10-20

    Laser ablation was studied as a means of removing radioactive contaminants from the surface and near-surface regions of concrete. The authors present the results of ablation tests on cement and concrete samples using a 1.6 kW pulsed Nd:YAG laser with fiber optic beam delivery. The laser-surface interaction was studied using cement and high density concrete as targets. Ablation efficiency and material removal rates were determined as functions of irradiance and pulse overlap. Doped samples were also ablated to determine the efficiency with which surface contaminants were removed and captured in the effluent. The results show that the cement phase of the material melts and vaporizes, but the aggregate portion (sand and rock) fragments. The effluent consists of both micron-size aerosol particles and chunks of fragmented aggregate material. Laser-induced optical emission spectroscopy was used to analyze the surface during ablation. Analysis of the effluent showed that contaminants such as cesium and strontium were strongly segregated into different regions of the particle size distribution of the aerosol.

  3. Effect of Non-Equilibrium Surface Thermochemistry in Simulation of Carbon Based Ablators

    NASA Technical Reports Server (NTRS)

    Chen, Yih-Kanq; Gokcen, Tahir

    2012-01-01

    This study demonstrates that coupling of a material thermal response code and a flow solver using non-equilibrium gas/surface interaction model provides time-accurate solutions for the multidimensional ablation of carbon based charring ablators. The material thermal response code used in this study is the Two-dimensional Implicit Thermal-response and AblatioN Program (TITAN), which predicts charring material thermal response and shape change on hypersonic space vehicles. Its governing equations include total energy balance, pyrolysis gas mass conservation, and a three-component decomposition model. The flow code solves the reacting Navier-Stokes equations using Data Parallel Line Relaxation (DPLR) method. Loose coupling between the material response and flow codes is performed by solving the surface mass balance in DPLR and the surface energy balance in TITAN. Thus, the material surface recession is predicted by finite-rate gas/surface interaction boundary conditions implemented in DPLR, and the surface temperature and pyrolysis gas injection rate are computed in TITAN. Two sets of nonequilibrium gas/surface interaction chemistry between air and the carbon surface developed by Park and Zhluktov, respectively, are studied. Coupled fluid-material response analyses of stagnation tests conducted in NASA Ames Research Center arc-jet facilities are considered. The ablating material used in these arc-jet tests was Phenolic Impregnated Carbon Ablator (PICA). Computational predictions of in-depth material thermal response and surface recession are compared with the experimental measurements for stagnation cold wall heat flux ranging from 107 to 1100 Watts per square centimeter.

  4. Sensors measure surface ablation rate of reentry vehicle heat shield

    NASA Technical Reports Server (NTRS)

    Russel, J. M., III

    1966-01-01

    Sensors measure surface erosion rate of ablating material in reentry vehicle heat shield. Each sensor, which is placed at precise depths in the heat shield is activated when the ablator surface erodes to the location of a sensing point. Sensor depth and activation time determine ablator surface erosion rate.

  5. Plasma protein corona modulates the vascular wall interaction of drug carriers in a material and donor specific manner.

    PubMed

    Sobczynski, Daniel J; Charoenphol, Phapanin; Heslinga, Michael J; Onyskiw, Peter J; Namdee, Katawut; Thompson, Alex J; Eniola-Adefeso, Omolola

    2014-01-01

    The nanoscale plasma protein interaction with intravenously injected particulate carrier systems is known to modulate their organ distribution and clearance from the bloodstream. However, the role of this plasma protein interaction in prescribing the adhesion of carriers to the vascular wall remains relatively unknown. Here, we show that the adhesion of vascular-targeted poly(lactide-co-glycolic-acid) (PLGA) spheres to endothelial cells is significantly inhibited in human blood flow, with up to 90% reduction in adhesion observed relative to adhesion in simple buffer flow, depending on the particle size and the magnitude and pattern of blood flow. This reduced PLGA adhesion in blood flow is linked to the adsorption of certain high molecular weight plasma proteins on PLGA and is donor specific, where large reductions in particle adhesion in blood flow (>80% relative to buffer) is seen with ∼60% of unique donor bloods while others exhibit moderate to no reductions. The depletion of high molecular weight immunoglobulins from plasma is shown to successfully restore PLGA vascular wall adhesion. The observed plasma protein effect on PLGA is likely due to material characteristics since the effect is not replicated with polystyrene or silica spheres. These particles effectively adhere to the endothelium at a higher level in blood over buffer flow. Overall, understanding how distinct plasma proteins modulate the vascular wall interaction of vascular-targeted carriers of different material characteristics would allow for the design of highly functional delivery vehicles for the treatment of many serious human diseases. PMID:25229244

  6. Advances in Quantitative Analyses and Reference Materials Related to Laser Ablation ICP-MS: A Look at Methods and New Directions

    NASA Astrophysics Data System (ADS)

    Koenig, A. E.; Ridley, W. I.

    2009-12-01

    The role of laser ablation ICP-MS (LA-ICP-MS) continues to expand both in geological sciences and other fields. As the technique continues to gain popularity, so too does the need for good reference materials and methods development and validation. Matrix matched reference materials (RMs) are required for calibration and quality control of LA-ICP-MS analyses. New advances in technology such as <200nm lasers and femtosecond lasers have reduced the dependence on matrix matching to some degree, but general matrix matching is still preferred. Much work has revolved around the available RMs such as the NIST 61x silicate glasses and several series of basaltic composition glasses such as the USGS natural basaltic glasses BCR-2g and synthetic basaltic glasses, the GS series (e.g. GSD-1g). While many quantitative hurdles have been recognized by analogous techniques such as EPMA and SIMS, some of these hurdles have not been fully addressed or validated for some cases of LA-ICP-MS. Trace element mapping by LA-ICP-MS is rapidly becoming more widespread for samples. Here relative differences in raw signal can be easily and rapidly obtained. However as too often is the case the magnitude of the relative differences in raw intensity are a function of different ablation yields, sample density or other factors. Methods of quantification for trace element mapping will be presented. The USGS has been developing microanalytical RMs intended for LA-ICP-MS for several years. The widely popular basaltic rock powders BCR-2, BIR-1 and BHVO-2 have all been successfully converted to homogeneous glasses suitable for LA-ICP-MS and have been in use by many workers. The newer synthetic basaltic glass GS series consists of 4 glasses of basaltic composition artificially doped at nominal concentrations of almost of trace elements at 400, 40, 4 and < 1 ppm. Additional developments in non-silcate or basaltic materials include the previously released MASS-1 Cu, Fe, Zn sulfide calibration RM (Wilson et

  7. Export of cyst wall material and Golgi organelle neogenesis in Giardia lamblia depend on endoplasmic reticulum exit sites.

    PubMed

    Faso, Carmen; Konrad, Christian; Schraner, Elisabeth M; Hehl, Adrian B

    2013-04-01

    Giardia lamblia parasitism accounts for the majority of cases of parasitic diarrheal disease, making this flagellated eukaryote the most successful intestinal parasite worldwide. This organism has undergone secondary reduction/elimination of entire organelle systems such as mitochondria and Golgi. However, trophozoite to cyst differentiation (encystation) requires neogenesis of Golgi-like secretory organelles named encystation-specific vesicles (ESVs), which traffic, modify and partition cyst wall proteins produced exclusively during encystation. In this work we ask whether neogenesis of Golgi-related ESVs during G. lamblia differentiation, similarly to Golgi biogenesis in more complex eukaryotes, requires the maintenance of distinct COPII-associated endoplasmic reticulum (ER) subdomains in the form of ER exit sites (ERES) and whether ERES are also present in non-differentiating trophozoites. To address this question, we identified conserved COPII components in G. lamblia cells and determined their localization, quantity and dynamics at distinct ERES domains in vegetative and differentiating trophozoites. Analogous to ERES and Golgi biogenesis, these domains were closely associated to early stages of newly generated ESV. Ectopic expression of non-functional Sar1 GTPase variants caused ERES collapse and, consequently, ESV ablation, leading to impaired parasite differentiation. Thus, our data show how ERES domains remain conserved in G. lamblia despite elimination of steady-state Golgi. Furthermore, the fundamental eukaryotic principle of ERES to Golgi/Golgi-like compartment correspondence holds true in differentiating Giardia presenting streamlined machinery for secretory organelle biogenesis and protein trafficking. However, in the Golgi-less trophozoites ERES exist as stable ER subdomains, likely as the sole sorting centres for secretory traffic. PMID:23094658

  8. Characterizing moisture-dependent mechanical properties of organic materials: humidity-controlled static and dynamic nanoindentation of wood cell walls

    NASA Astrophysics Data System (ADS)

    Bertinetti, Luca; Hangen, Ude D.; Eder, Michaela; Leibner, Petra; Fratzl, Peter; Zlotnikov, Igor

    2015-06-01

    Nanoindentation is an ideal technique to study local mechanical properties of a wide range of materials on the sub-micron scale. It has been widely used to investigate biological materials in the dry state; however, their properties are strongly affected by their moisture content, which until now has not been consistently controlled. In the present study, we developed an experimental set-up for measuring local mechanical properties of materials by nanoindentation in a controlled environment of relative humidity (RH) and temperature. The significance of this new approach in studying biological materials was demonstrated for the secondary cell wall layer (S2) in Spruce wood (Picea abies). The hardness of the cell wall layer decreased from an average of approximately 0.6 GPa at 6% RH down to approximately 0.2 GPa at 79% RH, corresponding to a reduction by a factor of 3. Under the same conditions, the indentation modulus also decreased by about 40%. The newly designed experimental set-up has a strong potential for a variety of applications involving the temperature- and humidity-dependent properties of biological and artificial organic nanocomposites.

  9. Indirect-drive ablative Richtmyer Meshkov node scaling

    NASA Astrophysics Data System (ADS)

    Landen, O. L.; Baker, K. L.; Clark, D. S.; Goncharov, V. N.; Hammel, B. A.; Ho, D. D.; Hurricane, O. A.; Lindl, J. D.; Loomis, E. N.; Masse, L.; Mauche, C.; Milovich, J. L.; Peterson, J. L.; Smalyuk, V. A.; Yi, S. A.; Velikovich, A. L.; Weber, C.

    2016-05-01

    The ablation front Rayleigh Taylor hydroinstability growth dispersion curve for indirect-drive implosions has been shown to be dependent on the Richtmyer Meshkov growth during the first shock transit phase. In this paper, a simplified treatment of the first shock ablative Richtmyer-Meshkov (ARM) growth dispersion curve is used to extract differences in ablation front perturbation growth behavior as function of foot pulse shape and ablator material for comparing the merits of various ICF design option.

  10. Analytical and numerical investigation of structural response of compliant wall materials, part 1

    NASA Technical Reports Server (NTRS)

    Balasubramanian, R.

    1978-01-01

    Surface motion of compliant walls in drag reduction experiments was analyzed. Critical comparison was made between the dynamic motion of the structure and the postulated mechanism of drag reduction. The spectrum of surface motion indicated that membranes over deep cavities respond at low frequencies and large wavelengths. The membrane over a deep cavity is therefore found not to yield the desired response predicted by the postulated mechanism. The membrane over a thin air gap is found to act as a wavelength chopper, and analysis of the nonlinear response of that compliant surface indicated its possible suitability for compliant wall experiments. Periodic structures are found to lock in the desired wavelengths of motion, and it was shown that at least in Kramer's initial experiments they produced high frequency surface motions. Laminated structures are found to be very ineffective as compliant models, except when there is no bonding between the membrane and the backing. Computer programs developed for these analyses are documented.

  11. Analytical and numerical investigation of structural response of compliant wall materials

    NASA Technical Reports Server (NTRS)

    Goglia, G. L.; Balasubramanian, R.

    1977-01-01

    Surface motion of compliant walls in drag reduction experiments was analyzed. The spectrum of surface motion indicates that membranes over deep cavities respond at low frequencies and large wavelengths. The membrane over a deep cavity is therefore found not to yield the desired reponse predicted by the postulated mechanism. The membrane over a thin air gap is found to act as a wavelength chopper, and analysis of the nonlinear response of the compliant surface indicates its possible suitability for compliant wall experiments. Periodic structures are found to lock in the desired wavelengths of motion. Laminated structures are found to be very ineffective as compliant models, except when there is no bonding between the membrane and the backing. Computer programs developed for these analyses are documented.

  12. Phenolic Impregnated Carbon Ablators (PICA) as Thermal Protection Systems for Discovery Missions

    NASA Technical Reports Server (NTRS)

    Tran, Huy K.; Johnson, Christine E.; Rasky, Daniel J.; Hui, Frank C. L.; Hsu, Ming-Ta; Chen, Timothy; Chen, Y. K.; Paragas, Daniel; Kobayashi, Loreen

    1997-01-01

    This paper presents the development of the light weight Phenolic Impregnated Carbon Ablators (PICA) and its thermal performance in a simulated heating environment for planetary entry vehicles. The PICA material was developed as a member of the Light Weight Ceramic Ablators (LCA's), and the manufacturing process of this material has since been significantly improved. The density of PICA material ranges from 14 to 20 lbm/ft(exp 3), having uniform resin distribution with and without a densified top surface. The thermal performance of PICA was evaluated in the Ames arc-jet facility at cold wall heat fluxes from 375 to 2,960 BtU/ft(exp 2)-s and surface pressures of 0.1 to 0.43 atm. Heat loads used in these tests varied from 5,500 to 29,600 BtU/ft(exp 2) and are representative of the entry conditions of the proposed Discovery Class Missions. Surface and in-depth temperatures were measured using optical pyrometers and thermocouples. Surface recession was also measured by using a template and a height gage. The ablation characteristics and efficiency of PICA are quantified by using the effective heat of ablation, and the thermal penetration response is evaluated from the thermal soak data. In addition, a comparison of thermal performance of standard and surface densified PICA is also discussed.

  13. A Self-Limiting Electro-Ablation Technique for the Top-Down Synthesis of Large-Area Monolayer Flakes of 2D Materials

    PubMed Central

    Das, Saptarshi; Bera, Mrinal K.; Tong, Sheng; Narayanan, Badri; Kamath, Ganesh; Mane, Anil; Paulikas, Arvydas P.; Antonio, Mark R.; Sankaranarayanan, Subramanian K. R. S.; Roelofs, Andreas K.

    2016-01-01

    We report the discovery of an electrochemical process that converts two dimensional layered materials of arbitrary thicknesses into monolayers. The lateral dimensions of the monolayers obtained by the process within a few seconds time at room temperature were as large as 0.5 mm. The temporal and spatial dynamics of this physical phenomenon, studied on MoS2 flakes using ex-situ AFM imaging, Raman mapping, and photoluminescence measurements trace the origin of monolayer formation to a substrate-assisted self-limiting electrochemical ablation process. Electronic structure and atomistic calculations point to the interplay between three essential factors in the process: (1) strong covalent interaction of monolayer MoS2 with the substrate; (2) electric-field induced differences in Gibbs free energy of exfoliation; (3) dispersion of MoS2 in aqueous solution of hydrogen peroxide. This process was successful in obtaining monolayers of other 2D transition metal dichalcogenides, like WS2 and MoTe2 as well. PMID:27323877

  14. A Self-Limiting Electro-Ablation Technique for the Top-Down Synthesis of Large-Area Monolayer Flakes of 2D Materials

    NASA Astrophysics Data System (ADS)

    Das, Saptarshi; Bera, Mrinal K.; Tong, Sheng; Narayanan, Badri; Kamath, Ganesh; Mane, Anil; Paulikas, Arvydas P.; Antonio, Mark R.; Sankaranarayanan, Subramanian K. R. S.; Roelofs, Andreas K.

    2016-06-01

    We report the discovery of an electrochemical process that converts two dimensional layered materials of arbitrary thicknesses into monolayers. The lateral dimensions of the monolayers obtained by the process within a few seconds time at room temperature were as large as 0.5 mm. The temporal and spatial dynamics of this physical phenomenon, studied on MoS2 flakes using ex-situ AFM imaging, Raman mapping, and photoluminescence measurements trace the origin of monolayer formation to a substrate-assisted self-limiting electrochemical ablation process. Electronic structure and atomistic calculations point to the interplay between three essential factors in the process: (1) strong covalent interaction of monolayer MoS2 with the substrate; (2) electric-field induced differences in Gibbs free energy of exfoliation; (3) dispersion of MoS2 in aqueous solution of hydrogen peroxide. This process was successful in obtaining monolayers of other 2D transition metal dichalcogenides, like WS2 and MoTe2 as well.

  15. A Self-Limiting Electro-Ablation Technique for the Top-Down Synthesis of Large-Area Monolayer Flakes of 2D Materials.

    PubMed

    Das, Saptarshi; Bera, Mrinal K; Tong, Sheng; Narayanan, Badri; Kamath, Ganesh; Mane, Anil; Paulikas, Arvydas P; Antonio, Mark R; Sankaranarayanan, Subramanian K R S; Roelofs, Andreas K

    2016-01-01

    We report the discovery of an electrochemical process that converts two dimensional layered materials of arbitrary thicknesses into monolayers. The lateral dimensions of the monolayers obtained by the process within a few seconds time at room temperature were as large as 0.5 mm. The temporal and spatial dynamics of this physical phenomenon, studied on MoS2 flakes using ex-situ AFM imaging, Raman mapping, and photoluminescence measurements trace the origin of monolayer formation to a substrate-assisted self-limiting electrochemical ablation process. Electronic structure and atomistic calculations point to the interplay between three essential factors in the process: (1) strong covalent interaction of monolayer MoS2 with the substrate; (2) electric-field induced differences in Gibbs free energy of exfoliation; (3) dispersion of MoS2 in aqueous solution of hydrogen peroxide. This process was successful in obtaining monolayers of other 2D transition metal dichalcogenides, like WS2 and MoTe2 as well. PMID:27323877

  16. Safety Analysis Using Lebesgue Strain Measure of Thick-Walled Cylinder for Functionally Graded Material under Internal and External Pressure

    PubMed Central

    Aggarwal, A. K.; Sharma, Richa; Sharma, Sanjeev

    2013-01-01

    Safety analysis has been done for thick-walled circular cylinder under internal and external pressure using transition theory which is based on the concept of generalized principal Lebesgue strain measure. Results have been analyzed theoretically and discussed numerically. From the analysis, it can be concluded that circular cylinder made of functionally graded material is on the safer side of the design as compared to homogeneous cylinder with internal and external pressure, which leads to the idea of “stress saving” that minimizes the possibility of fracture of cylinder. PMID:24089605

  17. Ablation of NIF Targets and Diagnostic Components by High Power Lasers and X-Rays from High Temperature Plasmas

    SciTech Connect

    Eder, D.C; Anderson, A.T.; Braun, D.G; Tobin, M.T.

    2000-04-19

    The National Ignition Facility (NIF) will consist of 192 laser beams that have a total energy of up to 1.8 MJ in the 3rd harmonic ({lambda} = 0.35 {micro}m) with the amount of 2nd harmonic and fundamental light depending on the pulse shape. Material near best focus of the 3rd harmonic light will be vaporized/ablated very rapidly, with a significant fraction of the laser energy converted into plasma x rays. Additional plasma x rays can come from imploding/igniting capsule inside Inertial Confinement Fusion (ICF) hohlraums. Material from outer portions of the target, diagnostic components, first-wall material, and optical components, are ablated by the plasma x rays. Material out to a radius of order 3 cm from target center is also exposed to a significant flux of 2nd harmonic and fundamental laser light. Ablation can accelerate the remaining material to high velocities if it has been fragmented or melted. In addition, the high velocity debris wind of the initially vaporized material pushes on the fragments/droplets and increases their velocity. The high velocity shrapnel fragments/droplets can damage the fused silica shields protecting the final optics in NIF. We discuss modeling efforts to calculate vaporization/ablation, x-ray generation, shrapnel production, and ways to mitigate damage to the shields.

  18. Halogenation of microcapsule walls

    NASA Technical Reports Server (NTRS)

    Davis, T. R.; Schaab, C. K.; Scott, J. C.

    1972-01-01

    Procedure for halogenation of confining walls of both gelatin and gelatin-phenolic resin capsules is similar to that used for microencapsulation. Ten percent halogen content renders capsule wall nonburning; any higher content enhances flame-retardant properties of selected internal phase material. Halogenation decreases permeability of wall material to encapsulated materials.

  19. Composite of single walled carbon nanotube and sulfosalicylic acid doped polyaniline: a thermoelectric material

    NASA Astrophysics Data System (ADS)

    Jana Chatterjee, Mukulika; Banerjee, Dipali; Chatterjee, Krishanu

    2016-08-01

    Nanocomposites containing single walled carbon nanotubes (SWCNTs) and highly ordered polyaniline (PANI) have been synthesized employing an in situ polymerization using different weight percentages of single-walled carbon nanotube (SWCNT) as template and aniline as a reactant. The composites show homogeneously dispersed SWCNTs which are uniformly coated with PANI through a strong interface interaction. Structural characterization shows that the PANI cultivated along the surface of the SWCNTs in an ordered manner during the SWCNT-directed polymerization process. Measurements at room temperature displayed a significant enhancement in both the electrical conductivity and thermoelectric power which could be attributed to the more ordered chain structures of the PANI on SWCNT. As a result, the power factor of the composite is improved which increases with temperature. At the same time, the measured value of thermal conductivity at room temperature being lowest among the reported values, has resulted in best ZT at room temperature. The lowest value of thermal conductivity is attributed to the large phonon scattering due to the introduction of nanointerfaces.

  20. Report on the joint meeting of the Division of Development and Technology Plasma/Wall Interaction and High Heat Flux Materials and Components Task Groups

    SciTech Connect

    Wilson, K.L.

    1985-10-01

    This report of the Joint Meeting of the Division of Development and Technology Plasma/Wall Interaction and High Heat Flux Materials and Components Task Groups contains contributing papers in the following areas: Plasma/Materials Interaction Program and Technical Assessment, High Heat Flux Materials and Components Program and Technical Assessment, Pumped Limiters, Ignition Devices, Program Planning Activities, Compact High Power Density Reactor Requirements, Steady State Tokamaks, and Tritium Plasma Experiments. All these areas involve the consideration of High Heat Flux on Materials and the Interaction of the Plasma with the First Wall. Many of the Test Facilities are described as well. (LSP)

  1. Electrochemical biosensing of galactose based on carbon materials: graphene versus multi-walled carbon nanotubes.

    PubMed

    Dalkıran, Berna; Erden, Pınar Esra; Kılıç, Esma

    2016-06-01

    In this study, two enzyme electrodes based on graphene (GR), Co3O4 nanoparticles and chitosan (CS) or multi-walled carbon nanotubes (MWCNTs), Co3O4 nanoparticles, and CS, were fabricated as novel biosensing platforms for galactose determination, and their performances were compared. Galactose oxidase (GaOx) was immobilized onto the electrode surfaces by crosslinking with glutaraldehyde. Optimum working conditions of the biosensors were investigated and the analytical performance of the biosensors was compared with respect to detection limit, linearity, repeatability, and stability. The MWCNTs-based galactose biosensor provided about 1.6-fold higher sensitivity than its graphene counterpart. Moreover, the linear working range and detection limit of the MWCNTs-based galactose biosensor was superior to the graphene-modified biosensor. The successful application of the purposed biosensors for galactose biosensing in human serum samples was also investigated. PMID:27074783

  2. An Approximate Ablative Thermal Protection System Sizing Tool for Entry System Design

    NASA Technical Reports Server (NTRS)

    Dec, John A.; Braun, Robert D.

    2006-01-01

    A computer tool to perform entry vehicle ablative thermal protection systems sizing has been developed. Two options for calculating the thermal response are incorporated into the tool. One, an industry-standard, high-fidelity ablation and thermal response program was integrated into the tool, making use of simulated trajectory data to calculate its boundary conditions at the ablating surface. Second, an approximate method that uses heat of ablation data to estimate heat shield recession during entry has been coupled to a one-dimensional finite-difference calculation that calculates the in-depth thermal response. The in-depth solution accounts for material decomposition, but does not account for pyrolysis gas energy absorption through the material. Engineering correlations are used to estimate stagnation point convective and radiative heating as a function of time. The sizing tool calculates recovery enthalpy, wall enthalpy, surface pressure, and heat transfer coefficient. Verification of this tool is performed by comparison to past thermal protection system sizings for the Mars Pathfinder and Stardust entry systems and calculations are performed for an Apollo capsule entering the atmosphere at lunar and Mars return speeds.

  3. An Approximate Ablative Thermal Protection System Sizing Tool for Entry System Design

    NASA Technical Reports Server (NTRS)

    Dec, John A.; Braun, Robert D.

    2005-01-01

    A computer tool to perform entry vehicle ablative thermal protection systems sizing has been developed. Two options for calculating the thermal response are incorporated into the tool. One, an industry-standard, high-fidelity ablation and thermal response program was integrated into the tool, making use of simulated trajectory data to calculate its boundary conditions at the ablating surface. Second, an approximate method that uses heat of ablation data to estimate heat shield recession during entry has been coupled to a one-dimensional finite-difference calculation that calculates the in-depth thermal response. The in-depth solution accounts for material decomposition, but does not account for pyrolysis gas energy absorption through the material. Engineering correlations are used to estimate stagnation point convective and radiative heating as a function of time. The sizing tool calculates recovery enthalpy, wall enthalpy, surface pressure, and heat transfer coefficient. Verification of this tool is performed by comparison to past thermal protection system sizings for the Mars Pathfinder and Stardust entry systems and calculations are performed for an Apollo capsule entering the atmosphere at lunar and Mars return speeds.

  4. Photochemical Ablation of Organic Solids

    NASA Astrophysics Data System (ADS)

    Garrison, Barbara

    2004-03-01

    As discovered by Srinivasan in 1982, irradiation of materials by far UV laser light can lead to photochemical ablation, a process distinct from normal thermal ablation in which the laser primarily heats the material. A versatile mesoscopic model for molecular dynamics simulations of the laser ablation phenomena is presented. The model incorporates both the thermal and photochemical events, that is, both heating of the system and UV induced bond-cleavage followed by abstraction and radical-radical recombination reactions. The results from the simulations are compared to experimental data and the basic physics and chemistry for each irradiation regime are discussed. Initial results from polymer ablation simulations will be presented. L. V. Zhigilei, P. B. S. Kodali and B. J. Garrison, J. Phys. Chem. B, 102, 2845-2853 (1998); L. V. Zhigilei and B. J. Garrison, Journal of Applied Physics, 88, 1281-1298 (2000). Y. G. Yingling, L. V. Zhigilei and B. J. Garrison, J. Photochemistry and Photobiology A: Chemistry, 145, 173-181 (2001); Y. G. Yingling and B. J. Garrison, Chem. Phys. Lett., 364, 237-243 (2002).

  5. Photoacoustic characterization of radiofrequency ablation lesions

    NASA Astrophysics Data System (ADS)

    Bouchard, Richard; Dana, Nicholas; Di Biase, Luigi; Natale, Andrea; Emelianov, Stanislav

    2012-02-01

    Radiofrequency ablation (RFA) procedures are used to destroy abnormal electrical pathways in the heart that can cause cardiac arrhythmias. Current methods relying on fluoroscopy, echocardiography and electrical conduction mapping are unable to accurately assess ablation lesion size. In an effort to better visualize RFA lesions, photoacoustic (PA) and ultrasonic (US) imaging were utilized to obtain co-registered images of ablated porcine cardiac tissue. The left ventricular free wall of fresh (i.e., never frozen) porcine hearts was harvested within 24 hours of the animals' sacrifice. A THERMOCOOLR Ablation System (Biosense Webster, Inc.) operating at 40 W for 30-60 s was used to induce lesions through the endocardial and epicardial walls of the cardiac samples. Following lesion creation, the ablated tissue samples were placed in 25 °C saline to allow for multi-wavelength PA imaging. Samples were imaged with a VevoR 2100 ultrasound system (VisualSonics, Inc.) using a modified 20-MHz array that could provide laser irradiation to the sample from a pulsed tunable laser (Newport Corp.) to allow for co-registered photoacoustic-ultrasound (PAUS) imaging. PA imaging was conducted from 750-1064 nm, with a surface fluence of approximately 15 mJ/cm2 maintained during imaging. In this preliminary study with PA imaging, the ablated region could be well visualized on the surface of the sample, with contrasts of 6-10 dB achieved at 750 nm. Although imaging penetration depth is a concern, PA imaging shows promise in being able to reliably visualize RF ablation lesions.

  6. [Chest wall moulages for radiotherapy of resected breast cancer with fast electrons: comparative tests of different materials].

    PubMed

    Niewald, M; Lehmann, W; Tkocz, H J; Scharding, B; Uhlmann, U; Schnabel, K; Leetz, H K

    1986-10-01

    Irradiation of the thoracic wall with high-speed electrons is one of the standard methods of prophylaxis and therapy of local recurrences and cutaneous metastases of an operated mammary carcinoma. The surface dose, however, is only 85% of the maximum dose, due to the depth dose curve of the electron beams with the preponderantly applied energy of 7MeV. This is a poor value, since most of all recurrences appear near to the surface and so the risk of giving an insufficient dose is involved. The dose distribution could be essentially improved by the use of moulages on the chest. These moulages were made of different materials which were tested and compared with respect to their suitability for radiotherapeutic purposes. The best materials proved to be "Urgo-Plastan" (manufacturer: Holphar, Sulzbach) and "Orthoplast" (manufacturer: Johnson & Johnson, Düsseldorf). Both materials are synthetic substances which after heating can easily be adapted to the body shape and which offer a good stability, little inconvenience for the patient and a relative easy handling. With these moulage materials, the surface dose is increased to 98% ("Urgo-Plastan") and 99% ("Orthoplast") of the maximum dose. PMID:3095940

  7. Measurements of preheat and shock melting in Be ablators during the first few nanoseconds of a National Ignition Facility ignition drive using the Omega laser

    SciTech Connect

    Bradley, D. K.; Prisbrey, S. T.; Page, R. H.; Braun, D. G.; Edwards, M. J.; Hibbard, R.; Moreno, K. A.; Mauldin, M. P.; Nikroo, A.

    2009-04-15

    A scaled Hohlraum platform was used to experimentally measure preheat in ablator materials during the first few nanoseconds of a radiation drive proposed for ignition experiments at the National Ignition Facility [J. A. Paisner et al., Laser Focus World 30, 75 (1994)]. The platform design approximates the radiation environment of the pole of the capsule by matching both the laser spot intensity and illuminated Hohlraum wall fraction in scaled halfraums driven by the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. Back surface motion measured via VISAR reflecting from the rear surface of the sample was used to measure sample motion prior to shock breakout. The experiments show that the first {approx}20 {mu}m of a Be ablator will be melted by radiation preheat, with subsequent material melted by the initial shock, in agreement with simulations. The experiments also show no evidence of anomalous heating of buried high-Z doped layers in the ablator.

  8. Wall Covering

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The attractive wall covering shown below is one of 132 styles in the Mirror Magic II line offered by The General Tire & Rubber Company, Akron, Ohio. The material is metallized plastic fabric, a spinoff from space programs. Wall coverings are one of many consumer applications of aluminized plastic film technology developed for NASA by a firm later bought by King-Seeley Thermos Company, Winchester, Massachusetts, which now produces the material. The original NASA use was in the Echo 1 passive communications satellite, a "space baloon" made of aluminized mylar; the high reflectivity of the metallized coating enabled relay of communications signals from one Earth station to another by "bouncing" them off the satellite. The reflectivity feature also made the material an extremely efficient insulator and it was subsequently widely used in the Apollo program for such purposes as temperature control of spacecraft components and insulation of tanks for fuels that must be maintained at very low temperatures. I Used as a wall covering, the aluminized material offers extra insulation, reflects light and I resists cracking. In addition to General Tire, King-Seeley also supplies wall covering material to Columbus Coated Fabrics Division of Borden, Incorporated, Columbus, Ohio, among others.

  9. Laser Ablation Propulsion A Study

    NASA Astrophysics Data System (ADS)

    Irfan, Sayed A.; Ugalatad, Akshata C.

    Laser Ablation Propulsion (LAP) will serve as an alternative propulsion system for development of microthrusters. The principle of LAP is that when a laser (pulsed or continuous wave) with sufficient energy (more than the vaporization threshold energy of material) is incident on material, ablation or vaporization takes place which leads to the generation of plasma. The generated plasma has the property to move away from the material hence pressure is generated which leads to the generation of thrust. Nowadays nano satellites are very common in different space and defence applications. It is important to build micro thruster which are useful for orienting and re-positioning small aircraft (like nano satellites) above the atmosphere. modelling of LAP using MATLAB and Mathematica. Schematic is made for the suitable optical configuration of LAP. Practical experiments with shadowgraphy and self emission techniques and the results obtained are analysed taking poly (vinyl-chloride) (PVC) as propellant to study the

  10. Laser ablation of blepharopigmentation

    SciTech Connect

    Tanenbaum, M.; Karas, S.; McCord, C.D. Jr. )

    1988-01-01

    This article discusses laser ablation of blepharopigmentation in four stages: first, experimentally, where pigment vaporization is readily achieved with the argon blue-green laser; second, in the rabbit animal model, where eyelid blepharopigmentation markings are ablated with the laser; third, in human subjects, where the argon blue-green laser is effective in the ablation of implanted eyelid pigment; and fourth, in a case report, where, in a patient with improper pigment placement in the eyelid, the laser is used to safely and effectively ablate the undesired pigment markings. This article describes in detail the new technique of laser ablation of blepharopigmentation. Potential complications associated with the technique are discussed.

  11. Effect of varieties composition of wall material on physical and chemistry characteristics of microcapsulated kaffir lime leave oleoresin (Citrus hystrix DC)

    NASA Astrophysics Data System (ADS)

    Latifatunissa, Zhulfani Nur; Kawiji, Khasanah, Lia Umi; Utami, Rohula

    2016-02-01

    This study aimed to determine the effect of variety composition of wall material on characteristic of micro capsulated kaffir lime leave oleoresin which includes yield, water content, and solubility in water, microstructure, residual solvent content and active compound content. This study used variety composition of maltodextrin and carrageenan (100%: 0%; 97%: 3%; 95%: 5%; 90%: 10%) as wall material, and kaffir lime leave oleoresin as core material which was extracted by maceration using ethanol as solvent. Analysis's result showed that the varieties composition of wall material influenced on yield and water content significantly. However, there was no significant influence discovered in solubility in water and residual solvent content. Active compounds contained in the product of oleoresin microcapsules kaffir lime leaves are citronella, citronellol, citronellyl acetate, nerolidol, phytol, farnesol while the levels of residual solvents in this study ranged from 0.01-0.015%. Based on experiment result showed that use carrageenan can produce preferable microstructure.

  12. Influence of frequency of the excitation magnetic field and material's electric conductivity on domain wall dynamics in ferromagnetic materials

    NASA Astrophysics Data System (ADS)

    Chávez-González, A. F.; Pérez-Benítez, J. A.; Espina-Hernández, J. H.; Grössinger, R.; Hallen, J. M.

    2016-03-01

    The present work analyzes the influence of electric conductivity on the Magnetic Barkhausen Noise (MBN) signal using a microscopic model which includes the influence of eddy currents. This model is also implemented to explain the dependence of MBN on the frequency of the applied magnetic field. The results presented in this work allow analyzing the influence of eddy currents on MBN signals for different values of the material's electric conductivity and for different frequencies of applied magnetic field. Additionally, the outcomes of this research can be used as a reference to differentiate the influence of eddy currents from that of second phase particles in the MBN signal, which has been reported in previous works.

  13. Microwave ablation versus laser ablation in occluding lateral veins in goats.

    PubMed

    Wang, Xu-hong; Wang, Xiao-ping; Su, Wen-juan; Yuan, Yuan

    2016-02-01

    Increasing number of endovenous techniques are available for the treatment of saphenous vein reflux and endovenous laser ablation (EVLA) is a frequently used method. A newly developed alternative, based on thermal therapy, is endovenous microwave ablation (EMA). This study evaluated the effect of the two procedures, in terms of coagulation and histological changes, in occluding lateral veins in goats. Twelve animals were randomized into two group, with 6 treated with EMA (EMA group), and the rest 6 with EVLA (EVLA group). Results of coagulation, including coagulation, fibrinolysis and platelet activation, were assessed at three or four different time points: before, immediately after, 24 h (and 48 h) after ablation. The diameter change, a measure of efficacy, was ultrasonographically measured before and 1 month after the ablation. Histological changes were grossly and microscopically evaluated immediately, 1 and 3 month(s) after the ablation. The length of the ablated vein and preoperative average diameter were comparable between the two groups. In both EMA and EVLA groups, several coagulation parameters, fibrinolysis and platelet activation parameters only underwent slight changes. Ultrasound imaging displayed that the diameter reduction of the veins treated by EMA was significantly larger than by EVLA, in consistent with the results of macroscopic examination. Microscopic examination revealed necrosis and thickening of the vein wall, and occlusion of the lumen within 3 months after ablation in both EMA and EVLA groups. It is concluded that EMA is a minimally invasive therapy, which appears to be safe and effective for treatment of lateral veins in goats. PMID:26838749

  14. Bio-based hyperbranched thermosetting polyurethane/triethanolamine functionalized multi-walled carbon nanotube nanocomposites as shape memory materials.

    PubMed

    Kalita, Hemjyoti; Karak, Niranjan

    2014-07-01

    Here, bio-based shape memory polymers have generated immense interest in recent times. Here, Bio-based hyperbranched polyurethane/triethanolamine functionalized multi-walled carbon nanotube (TEA-f-MWCNT) nanocomposites were prepared by in-situ pre-polymerization technique. The Fourier transform infrared spectroscopy and the transmission electron microscopic studies showed the strong interfacial adhesion and the homogeneous distribution of TEA-f-MWCNT in the polyurethane matrix. The prepared epoxy cured thermosetting nanocomposites exhibited enhanced tensile strength (6.5-34.5 MPa), scratch hardness (3.0-7.5 kg) and thermal stability (241-288 degrees C). The nanocomposites showed excellent shape fixity and shape recovery. The shape recovery time decreases (24-10 s) with the increase of TEA-f-MWCNT content in the nanocomposites. Thus the studied nanocomposites have potential to be used as advanced shape memory materials. PMID:24758045

  15. Transient and steady-state velocity of domain walls for a complete range of drive fields. [in magnetic material

    NASA Technical Reports Server (NTRS)

    Bourne, H. C., Jr.; Bartran, D. S.

    1974-01-01

    Approximate analytic solutions for transient and steady-state 180 deg domain-wall motion in bulk magnetic material are obtained from the dynamic torque equations with a Gilbert damping term. The results for the Walker region in which the transient solution approaches the familiar Walker steady-state solution are presented in a slightly new form for completeness. An analytic solution corresponding to larger drive fields predicts an oscillatory motion with an average value of the velocity which decreases with drive field for reasonable values of the damping parameter. These results agree with those obtained by others from a computer solution of the torque equation and those obtained by others with the assumption of a very large anisotropy field.

  16. Physics-Based Simulation and Experiment on Blast Protection of Infill Walls and Sandwich Composites Using New Generation of Nano Particle Reinforced Materials

    NASA Astrophysics Data System (ADS)

    Irshidat, Mohammad

    A critical issue for the development of nanotechnology is our ability to understand, model, and simulate the behavior of small structures and to make the connection between nano structure properties and their macroscopic functions. Material modeling and simulation helps to understand the process, to set the objectives that could guide laboratory efforts, and to control material structures, properties, and processes at physical implementation. These capabilities are vital to engineering design at the component and systems level. In this research, experimental-computational-analytical program was employed to investigate the performance of the new generation of polymeric nano-composite materials, like nano-particle reinforced elastomeric materials (NPREM), for the protection of masonry structures against blast loads. New design tools for using these kinds of materials to protect Infill Walls (e.g. masonry walls) against blast loading were established. These tools were also extended to cover other type of panels like sandwich composites. This investigation revealed that polymeric nano composite materials are strain rate sensitive and have large amount of voids distributed randomly inside the materials. Results from blast experiments showed increase in ultimate flexural resistance achieved by both unreinforced and nano reinforced polyurea retrofit systems applied to infill masonry walls. It was also observed that a thin elastomeric coating on the interior face of the walls could be effective at minimizing the fragmentation resulting from blast. More conclusions are provided with recommended future research.

  17. Electron Beam Ablation of Metals

    NASA Astrophysics Data System (ADS)

    Kovaleski, S. D.; Gilgenbach, R. M.; Rintamaki, J. I.; Ang, L. K.; Spindler, H. L.; Cohen, W. E.; Lau, Y. Y.; Lash, J. S.

    1996-10-01

    An experiment has recently been devised for material ablation using a channelspark electron beam. The ultimate goal of this experiment is to deposit thin films by electron beam ablation. The channelspark is a pseudospark device developed by Forschungszentrum Karlsruhe (G. Muller, C. Schultheiss, Proc. of Beams, 2, 833(1994)) for production of high current, low energy electron beams. The channelspark has the following operating parameters: a 15-20kV accelerating potential and measured source current of <2000A. Initial experiments have concentrated on characterizing ion-focused electron beam current transport through the necessary background fill gas (typically 5-50 mTorr of Argon). Ablation of Al, Fe, and Ti is being studied with spectroscopy and electron beam current diagnostics. Physical beam target damage is also being investigated and compared to laser ablated targets. Simulations of electron transport and energy deposition are being conducted via the ITS-TIGER code (Sandia Report No. SAND 91-1634) developed at Sandia National Laboratory.

  18. BUILDING MATERIAL CHARACTERIZATION USING A CONCRETE FLOOR AND WALL CONTAMINATION PROFILING TECHNOLOGY

    SciTech Connect

    Aggarwal, Dr. S.,; Charters, G.; Thacker, Dr. D.

    2003-02-27

    Certain radioisotopes can penetrate concrete and contaminate the concrete well below the surface. The challenge is to determine the extent and magnitude of the contamination problem in real-time. The concrete profiling technology, TRUPROSM in conjunction with portable radiometric instrumentation produces a profile of radiological or chemical contamination through the material being studied. The data quality, quantity, and representativeness may be used to produce an activity profile from the hot spot surface into the material being sampled. This activity profile may then be expanded to ultimately characterize the facility and expedite waste segregation and facility closure at a reduced cost and risk. Performing a volumetric concrete or metal characterization safer and faster (without lab intervention) is the objective of this characterization technology. This way of determining contamination can save considerable time and money. Currently, concrete core bores are shipped to certified laboratories where the concrete residue is run through a battery of tests to determine the contaminants. The existing core boring operation volatilizes or washes out some of the contaminants (like tritium) and oftentimes cross-contaminates the area around the core bore site. The volatilization of the contaminants can lead to airborne problems in the immediate vicinity of the core bore. Cross-contamination can increase the contamination area and thereby increase the amount of waste generated. The goal is to avoid those field activities that could cause this type of release.

  19. 1064 nm FT-Raman spectroscopy for investigations of plant cell walls and other biomass materials

    PubMed Central

    Agarwal, Umesh P.

    2014-01-01

    Raman spectroscopy with its various special techniques and methods has been applied to study plant biomass for about 30 years. Such investigations have been performed at both macro- and micro-levels. However, with the availability of the Near Infrared (NIR) (1064 nm) Fourier Transform (FT)-Raman instruments where, in most materials, successful fluorescence suppression can be achieved, the utility of the Raman investigations has increased significantly. Moreover, the development of several new capabilities such as estimation of cellulose-crystallinity, ability to analyze changes in cellulose conformation at the local and molecular level, and examination of water-cellulose interactions have made this technique essential for research in the field of plant science. The FT-Raman method has also been applied to research studies in the arenas of biofuels and nanocelluloses. Moreover, the ability to investigate plant lignins has been further refined with the availability of near-IR Raman. In this paper, we present 1064-nm FT-Raman spectroscopy methodology to investigate various compositional and structural properties of plant material. It is hoped that the described studies will motivate the research community in the plant biomass field to adapt this technique to investigate their specific research needs. PMID:25295049

  20. Nonequilibrium Ablation of Phenolic Impregnated Carbon Ablator

    NASA Technical Reports Server (NTRS)

    Milos, Frank S.; Chen, Yih K.; Gokcen, Tahir

    2012-01-01

    In previous work, an equilibrium ablation and thermal response model for Phenolic Impregnated Carbon Ablator was developed. In general, over a wide range of test conditions, model predictions compared well with arcjet data for surface recession, surface temperature, in-depth temperature at multiple thermocouples, and char depth. In this work, additional arcjet tests were conducted at stagnation conditions down to 40 W/sq cm and 1.6 kPa. The new data suggest that nonequilibrium effects become important for ablation predictions at heat flux or pressure below about 80 W/sq cm or 10 kPa, respectively. Modifications to the ablation model to account for nonequilibrium effects are investigated. Predictions of the equilibrium and nonequilibrium models are compared with the arcjet data.

  1. Effect of wall thickness and material on flexural fatigue of hollow rolling elements

    NASA Technical Reports Server (NTRS)

    Bamberger, E. N.; Parker, R. J.

    1978-01-01

    Hollow cylindrical bars were tested in a rolling-contact fatigue tester to determine the effects of material and outside diameter to inside diameter (OD/ID) ratios on fatigue failure mode and subsequent failure propagation. The range of applied loads with OD/ID ratios of 2.0, 1.6, 1.4, and 1.2 resulted in maximum tangential tensile stresses ranging from 165 to 655 MPa at the bore surface. Flexural failures of the hollow test bars occurred when this bore stress was 490 MPa or greater with AISI 52100 hollow bars and 338 MPa or greater with AISI M-50 hollow bars. Good correlation was obtained in relating the failures of these hollow bars with flexural failures of drilled balls from full-scale bearing test published previously.

  2. Composite wall concept for high temperature turbine shrouds: Survey of low modulus strain isolator materials

    NASA Technical Reports Server (NTRS)

    Bill, R. C.; Allen, G. P.; Wisander, D. W.

    1980-01-01

    Plasma sprayed yttria stabilized zirconium oxide turbine seal specimens, incorporating various low modulus porous metal strain isolator pads between the zirconium oxide and a dense metal substrate, were subjected to cyclic thermal shock testing. Specimens that had a low modulus pad composed of sintered FeNiCrAlY fibermetal survived 1000 thermal shock cycles without spalling of the ceramic. A figure of merit for the low modulus pad materials taking into consideration the elastic modulus, thermal conductivity, strength, and oxidation resistance of the pad was proposed, and showed reasonable agreement with the thermal shock results. A potential surface distress problem on the zirconium oxide, associated with nonuniform temperature distribution and rapid stress relaxation was identified. One approach to solving the surface distress problem through application of laser surface fusion of the zirconium oxide layer showed some promise, but improvements in the laser surface fusion process are necessary to prevent process associated damage to the ceramic.

  3. Subpicosecond laser ablation of dental enamel

    NASA Astrophysics Data System (ADS)

    Rode, A. V.; Gamaly, E. G.; Luther-Davies, B.; Taylor, B. T.; Dawes, J.; Chan, A.; Lowe, R. M.; Hannaford, P.

    2002-08-01

    Laser ablation of dental enamel with subpicosecond laser pulses has been studied over the intensity range of (0.1-1.4) x1014 W/cm2 using 95 and 150 fs pulses at a pulse repetition rate of 1 kHz. The experimentally determined ablation threshold of 2.2plus-or-minus0.1 J/cm2 was in good agreement with theoretical predictions based on an electrostatic ablation model. The ablation rate increased linearly with the laser fluence for up to 15 times the ablation threshold. The absence of collateral damage was observed using optical and scanning electron microscopy. Pulpal temperature measurements showed an increase of about 10 degC during the 200 s course of ablation. However, air cooling at a rate of 5 l/min resulted in the intrapulpal temperature being maintained below the pulpal damage threshhold of 5.5 degC. The material removal rates for subpicosecond precision laser ablation of dental enamel are compared with other techniques.

  4. On the Ablation Models of Fuel Pellets

    SciTech Connect

    Rozhansky, V.A.; Senichenkov, I.Yu.

    2005-12-15

    The neutral gas shielding model and neutral-gas-plasma shielding model are analyzed qualitatively. The main physical processes that govern the formation of the shielding gas cloud and, consequently, the ablation rate are considered. For the neutral gas shielding model, simple formulas relating the ablation rate and cloud parameters to the parameters of the pellet and the background plasma are presented. The estimates of the efficiency of neutral gas shielding and plasma shielding are compared. It is shown that the main portion of the energy flux of the background electrons is released in the plasma cloud. Formulas for the ablation rate and plasma parameters are derived in the neutral-gas-plasma shielding model. The question is discussed as to why the neutral gas shielding model describes well the ablation rate of the pellet material, although it does not take into account the ionization effects and the effects associated with the interaction of ionized particles with the magnetic field. The reason is that the ablation rate depends weakly on the energy flux of hot electrons; as a result, the attenuation of this flux by the electrostatic shielding and plasma shielding has little effect on the ablation rate. This justifies the use of the neutral gas shielding model to estimate the ablation rate (to within a factor of about 2) over a wide range of parameters of the pellet and the background plasma.

  5. Radiofrequency catheter ablation of accessory pathways in infants.

    PubMed Central

    Benito, F.; Sánchez, C.

    1997-01-01

    OBJECTIVE: To evaluate the indications, results and complications of radiofrequency catheter ablation in small infants with supraventricular tachycardia due to an accessory atrioventricular pathway. METHODS: Five infants less than 9 months old underwent radiofrequency catheter ablation of accessory pathways. Ablation was done for medically refractory tachyarrhythmia associated with aborted sudden death in two patients, left ventricular dysfunction in one, failure of antiarrhythmic drugs in one, and planned cardiac surgery in one. All five patients underwent a single successful procedure. Three left free wall pathways were ablated by transseptal approach, a right posteroseptal pathway was ablated from the inferior vena cava, and a left posteroseptal pathway was approached from the inferior vena cava into the coronary sinus. A deflectable 5F bipolar electrode catheter with a 3 mm tip was used. RESULTS: A sudden increment in impedance indicative of coagulum formation was observed in two procedures. One patient developed a transient ischaemic complication after ablation of a left lateral accessory pathway by transseptal approach. This patient had mild pericardial effusion after the procedure. Moderate pericardial effusion was also noted in another patient. After a mean follow up of 18.4 months all patients are symptom free without treatment. CONCLUSIONS: Radiofrequency catheter ablation can be performed successfully in infants. Temperature monitoring in 5F ablation catheters would be desirable to prevent the development of coagulum. Echocardiography must be performed after the ablation procedure to investigate pericardial effusion. Images PMID:9326990

  6. Fracture in Phenolic Impregnated Carbon Ablator

    NASA Technical Reports Server (NTRS)

    Agrawal, Parul; Chavez-Garcia, Jose; Pham, John

    2013-01-01

    This paper describes the development of a novel technique to understand the failure mechanisms inside thermal protection materials. The focus of this research is on the class of materials known as phenolic impregnated carbon ablators. It has successfully flown on the Stardust spacecraft and is the thermal protection system material chosen for the Mars Science Laboratory and SpaceX Dragon spacecraft. Although it has good thermal properties, structurally, it is a weak material. To understand failure mechanisms in carbon ablators, fracture tests were performed on FiberForm(Registered TradeMark) (precursor), virgin, and charred ablator materials. Several samples of these materials were tested to investigate failure mechanisms at a microstructural scale. Stress-strain data were obtained simultaneously to estimate the tensile strength and toughness. It was observed that cracks initiated and grew in the FiberForm when a critical stress limit was reached such that the carbon fibers separated from the binder. However, both for virgin and charred carbon ablators, crack initiation and growth occurred in the matrix (phenolic) phase. Both virgin and charred carbon ablators showed greater strength values compared with FiberForm samples, confirming that the presence of the porous matrix helps in absorbing the fracture energy.

  7. Femtosecond laser ablation of brass in air and liquid media

    NASA Astrophysics Data System (ADS)

    Shaheen, M. E.; Gagnon, J. E.; Fryer, B. J.

    2013-06-01

    Laser ablation of brass in air, water, and ethanol was investigated using a femtosecond laser system operating at a wavelength of 785 nm and a pulse width less than 130 fs. Scanning electron and optical microscopy were used to study the efficiency and quality of laser ablation in the three ablation media at two different ablation modes. With a liquid layer thickness of 3 mm above the target, ablation rate was found to be higher in water and ethanol than in air. Ablation under water and ethanol showed cleaner surfaces and less debris re-deposition compared to ablation in air. In addition to spherical particles that are normally formed from re-solidified molten material, micro-scale particles with varying morphologies were observed scattered in the ablated structures (craters and grooves) when ablation was conducted under water. The presence of such particles indicates the presence of a non-thermal ablation mechanism that becomes more apparent when ablation is conducted under water.

  8. Nanochemical effects in femtosecond laser ablation of metals

    SciTech Connect

    Vorobyev, A. Y.; Guo, Chunlei

    2013-02-18

    We study chemical energy released from the oxidation of aluminum in multipulse femtosecond laser ablation in air and oxygen. Our study shows that the released chemical energy amounts to about 13% of the incident laser energy, and about 50% of the ablated material is oxidized. The ablated material mass per laser pulse is measured to be on the nanogram scale. Our study indicates that femtosecond laser ablation is capable of inducing nanochemical reactions since the femtosecond laser pulse can controllably produce nanoparticles, clusters, and atoms from a solid target.

  9. Renal Ablation Update

    PubMed Central

    Khiatani, Vishal; Dixon, Robert G.

    2014-01-01

    Thermal ablative technologies have evolved considerably in the recent past and are now an important component of current clinical guidelines for the treatment of small renal masses. Both radiofrequency ablation and cryoablation have intermediate-term oncologic control that rivals surgical options, with favorable complication profiles. Studies comparing cryoablation and radiofrequency ablation show no significant difference in oncologic control or complication profile between the two modalities. Early data from small series with microwave ablation have shown similar promising results. Newer technologies including irreversible electroporation and high-intensity–focused ultrasound have theoretical advantages, but will require further research before becoming a routine part of the ablation armamentarium. The purpose of this review article is to discuss the current ablative technologies available, briefly review their mechanisms of action, discuss technical aspects of each, and provide current data supporting their use. PMID:25049445

  10. Renal ablation update.

    PubMed

    Khiatani, Vishal; Dixon, Robert G

    2014-06-01

    Thermal ablative technologies have evolved considerably in the recent past and are now an important component of current clinical guidelines for the treatment of small renal masses. Both radiofrequency ablation and cryoablation have intermediate-term oncologic control that rivals surgical options, with favorable complication profiles. Studies comparing cryoablation and radiofrequency ablation show no significant difference in oncologic control or complication profile between the two modalities. Early data from small series with microwave ablation have shown similar promising results. Newer technologies including irreversible electroporation and high-intensity-focused ultrasound have theoretical advantages, but will require further research before becoming a routine part of the ablation armamentarium. The purpose of this review article is to discuss the current ablative technologies available, briefly review their mechanisms of action, discuss technical aspects of each, and provide current data supporting their use. PMID:25049445

  11. Features of the synthesis of nanocolloid oxides by laser ablation of bulk metal targets in solutions

    NASA Astrophysics Data System (ADS)

    Lapin, Ivan N.; Svetlichnyi, Valery A.

    2015-12-01

    Laser ablation of bulk targets in a fluid -- a promising new method for the synthesis of "pure" nanocolloids. Nanocrystalline materials produced by laser ablation are widely used in biology, medicine, and catalysis. High local temperature during ablation and large surface area of the particles promote chemical reactions and the formation of a complex composition of nanoparticles. In this paper the characteristics of the process of ablation and the obtaining of nanoparticles in a liquid by laser ablation of active materials (Zn, Ce, Ti, Si) were studied. Ways of increasing the productivity of laser ablation were discussed. Characterization of nanocolloids and nanocrystalline powders were performed.

  12. Effect of material properties on the strain to failure of thick-walled cylinders subjected to internal pressure

    SciTech Connect

    Roach, D.P.; Priddy, T.G. )

    1994-05-01

    The determination of the fully plastic response and pressure limit of a pressure vessel is of considerable importance in design, especially in autofrettage considerations. This paper presents the results of an experimental study which measured the maximum internal pressure which can be applied to thick-walled cylindrical vessels. Both aluminum and steel, with material properties ranging from ductile to brittle, were tested at stress levels through plastic and strain hardening ranges to fracture. From these tests, the pressure-expansion and through-thickness yielding characteristics were determined for these specimens. It is shown that a strain-to-failure criterion, based on the triaxiality of stress in the critical region, can be used to predict the complete pressure versus strain relations and maximum pressure for these cylinders. A simple tension-true stress-strain relation of the material is employed to analytically predict the response of the cylinder into the plastic regime. Finally, simplified theoretical and empirical formulas for bursting pressures are checked against the experimental results.

  13. Radiofrequency Ablation of Cancer

    PubMed Central

    Friedman, Marc; Mikityansky, Igor; Kam, Anthony; Libutti, Steven K.; Walther, McClellan M.; Neeman, Ziv; Locklin, Julia K.; Wood, Bradford J.

    2008-01-01

    Radiofrequency ablation (RFA) has been used for over 18 years for treatment of nerve-related chronic pain and cardiac arrhythmias. In the last 10 years, technical developments have increased ablation volumes in a controllable, versatile, and relatively inexpensive manner. The host of clinical applications for RFA have similarly expanded. Current RFA equipment, techniques, applications, results, complications, and research avenues for local tumor ablation are summarized. PMID:15383844

  14. Radiofrequency Ablation of Cancer

    SciTech Connect

    Friedman, Marc; Mikityansky, Igor; Kam, Anthony; Libutti, Steven K.; Walther, McClellan M.; Neeman, Ziv; Locklin, Julia K.; Wood, Bradford J.

    2004-09-15

    Radiofrequency ablation (RFA) has been used for over 18 years for treatment of nerve-related chronic pain and cardiac arrhythmias. In the last 10 years, technical developments have increased ablation volumes in a controllable, versatile, and relatively inexpensive manner. The host of clinical applications for RFA have similarly expanded. Current RFA equipment, techniques, applications, results, complications, and research avenues for local tumor ablation are summarized.

  15. Lung Ablation: Whats New?

    PubMed

    Xiong, Lillian; Dupuy, Damian E

    2016-07-01

    Lung cancer had an estimated incidence of 221,200 in 2015, making up 13% of all cancer diagnoses. Tumor ablation is an important treatment option for nonsurgical lung cancer and pulmonary metastatic patients. Radiofrequency ablation has been used for over a decade with newer modalities, microwave ablation, cryoablation, and irreversible electroporation presenting as additional and possibly improved treatment options for patients. This minimally invasive therapy is best for small primary lesions or favorably located metastatic tumors. These technologies can offer palliation and sometimes cure of thoracic malignancies. This article discusses the current available technologies and techniques available for tumor ablation. PMID:27050331

  16. Laser ablation in analytical chemistry - A review

    SciTech Connect

    Russo, Richard E.; Mao, Xianglei; Liu, Haichen; Gonzalez, Jhanis; Mao, Samuel S.

    2001-10-10

    Laser ablation is becoming a dominant technology for direct solid sampling in analytical chemistry. Laser ablation refers to the process in which an intense burst of energy delivered by a short laser pulse is used to sample (remove a portion of) a material. The advantages of laser ablation chemical analysis include direct characterization of solids, no chemical procedures for dissolution, reduced risk of contamination or sample loss, analysis of very small samples not separable for solution analysis, and determination of spatial distributions of elemental composition. This review describes recent research to understand and utilize laser ablation for direct solid sampling, with emphasis on sample introduction to an inductively coupled plasma (ICP). Current research related to contemporary experimental systems, calibration and optimization, and fractionation is discussed, with a summary of applications in several areas.

  17. Effects of Laser Wavelength on Ablator Testing

    NASA Technical Reports Server (NTRS)

    White, Susan M.

    2014-01-01

    Wavelength-dependent or spectral radiation effects are potentially significant for thermal protection materials. NASA atmospheric entry simulations include trajectories with significant levels of shock layer radiation which is concentrated in narrow spectral lines. Tests using two different high powered lasers, the 10.6 micron LHMEL I CO2 laser and the near-infrared 1.07 micron fiber laser, on low density ablative thermal protection materials offer a unique opportunity to evaluate spectral effects. Test results indicated that the laser wavelength can impact the thermal response of an ablative material, in terms of bond-line temperatures, penetration times, mass losses, and char layer thicknesses.

  18. Stagnation-point ablation of carbonaceous flat disks. I Theory

    NASA Technical Reports Server (NTRS)

    Park, C.

    1983-01-01

    The process of ablation is calculated for the stagnation region of a flat disk in a radiation-dominated, massive-blowing environment produced in a ballistic range filled with argon. Flow environments are determined by solving the boundary-layer equations while radiative transfer is calculated through a line-by-line spectral computation. The resulting wall heat-transfer rates are coupled with an existing material's response code to determine surface recession and char thickness. The calculation is performed for six 5-cm-diam models made of carbon-phenolic and carbon-carbon composite launched in the Track-G facility at the Arnold Engineering Development Center. Significant surface recessions are predicted to occur for these models due mostly to radiative heating.

  19. Ablation of Myocardial Tissue With Nanosecond Pulsed Electric Fields

    PubMed Central

    Xie, Fei; Varghese, Frency; Pakhomov, Andrei G.; Semenov, Iurii; Xiao, Shu; Philpott, Jonathan; Zemlin, Christian

    2015-01-01

    Background Ablation of cardiac tissue is an essential tool for the treatment of arrhythmias, particularly of atrial fibrillation, atrial flutter, and ventricular tachycardia. Current ablation technologies suffer from substantial recurrence rates, thermal side effects, and long procedure times. We demonstrate that ablation with nanosecond pulsed electric fields (nsPEFs) can potentially overcome these limitations. Methods We used optical mapping to monitor electrical activity in Langendorff-perfused New Zealand rabbit hearts (n = 12). We repeatedly inserted two shock electrodes, spaced 2–4 mm apart, into the ventricles (through the entire wall) and applied nanosecond pulsed electric fields (nsPEF) (5–20 kV/cm, 350 ns duration, at varying pulse numbers and frequencies) to create linear lesions of 12–18 mm length. Hearts were stained either with tetrazolium chloride (TTC) or propidium iodide (PI) to determine the extent of ablation. Some stained lesions were sectioned to obtain the three-dimensional geometry of the ablated volume. Results In all animals (12/12), we were able to create nonconducting lesions with less than 2 seconds of nsPEF application per site and minimal heating (< 0.2°C) of the tissue. The geometry of the ablated volume was smoother and more uniform throughout the wall than typical for RF ablation. The width of the lesions could be controlled up to 6 mm via the electrode spacing and the shock parameters. Conclusions Ablation with nsPEFs is a promising alternative to radiofrequency (RF) ablation of AF. It may dramatically reduce procedure times and produce more consistent lesion thickness than RF ablation. PMID:26658139

  20. Microwave Ablation of Hepatic Malignancy

    PubMed Central

    Lubner, Meghan G.; Brace, Christopher L.; Ziemlewicz, Tim J.; Hinshaw, J. Louis; Lee, Fred T.

    2013-01-01

    Microwave ablation is an extremely promising heat-based thermal ablation modality that has particular applicability in treating hepatic malignancies. Microwaves can generate very high temperatures in very short time periods, potentially leading to improved treatment efficiency and larger ablation zones. As the available technology continues to improve, microwave ablation is emerging as a valuable alternative to radiofrequency ablation in the treatment of hepatic malignancies. This article reviews the current state of microwave ablation including technical and clinical considerations. PMID:24436518

  1. Numerical simulation of film-cooled ablative rocket nozzles

    NASA Technical Reports Server (NTRS)

    Landrum, D. B.; Beard, R. M.

    1996-01-01

    The objective of this research effort was to evaluate the impact of incorporating an additional cooling port downstream between the injector and nozzle throat in the NASA Fast Track chamber. A numerical model of the chamber was developed for the analysis. The analysis did not model ablation but instead correlated the initial ablation rate with the initial nozzle wall temperature distribution. The results of this study provide guidance in the development of a potentially lighter, second generation ablative rocket nozzle which maintains desired performance levels.

  2. Quality evaluation of peony seed oil spray-dried in different combinations of wall materials during encapsulation and storage.

    PubMed

    Shi, Yan; Wang, Shu-Jie; Tu, Zong-Cai; Wang, Hui; Li, Ru-Yi; Zhang, Lu; Huang, Tao; Su, Ting; Li, Cui

    2016-06-01

    This study aimed at evaluating the performance of peony seed oil microencapsulated by spray drying during encapsulation and storage. Four different combinations of gum arabic (GA), corn syrup (CS), whey protein concentrate (WPC) and sodium caseinate (CAS) were used to encapsulate peony seed oil. The best encapsulation efficiency was obtained for CAS/CS followed by the CAS/GA/CS combination with the encapsulation ratio of 93.71 and 92.80 %, respectively, while the lowest encapsulation efficiency was obtained for WPC/GA/CS (85.96 %). Scanning electron microscopy and confocal laser scanning microscopy revealed that the particles were spherical in shape and did not exhibit apparent cracks or fissures, and gum arabic was uniformly distributed across the wall of the microcapsules. Oxidative stability study indicated that the CAS/GA/CS combination presented the best protection against lipid oxidation and the smallest loss of polyunsaturated fatty acid content among all of the formulas as measured by gas chromatography. Therefore, CAS/GA/CS could be promising materials encapsulate peony seed oil with high encapsulation efficiency and minimal lipid oxidation. PMID:27478215

  3. Clinical Significance of Additional Ablation of Atrial Premature Beats after Catheter Ablation for Atrial Fibrillation

    PubMed Central

    Kim, In-Soo; Yang, Pil-Sung; Kim, Tae-Hoon; Park, Junbeum; Park, Jin-Kyu; Uhm, Jae Sun; Joung, Boyoung; Lee, Moon Hyoung

    2016-01-01

    Purpose The clinical significance of post-procedural atrial premature beats immediately after catheter ablation for atrial fibrillation (AF) has not been clearly determined. We hypothesized that the provocation of immediate recurrence of atrial premature beats (IRAPB) and additional ablation improves the clinical outcome of AF ablation. Materials and Methods We enrolled 200 patients with AF (76.5% males; 57.4±11.1 years old; 64.3% paroxysmal AF) who underwent catheter ablation. Post-procedure IRAPB was defined as frequent atrial premature beats (≥6/min) under isoproterenol infusion (5 µg/min), monitored for 10 min after internal cardioversion, and we ablated mappable IRAPBs. Post-procedural IRAPB provocations were conducted in 100 patients. We compared the patients who showed IRAPB with those who did not. We also compared the IRAPB provocation group with 100 age-, sex-, and AF-type-matched patients who completed ablation without provocation (No-Test group). Results 1) Among the post-procedural IRAPB provocation group, 33% showed IRAPB and required additional ablation with a longer procedure time (p=0.001) than those without IRAPB, without increasing the complication rate. 2) During 18.0±6.6 months of follow-up, the patients who showed IRAPB had a worse clinical recurrence rate than those who did not (27.3% vs. 9.0%; p=0.016), in spite of additional IRAPB ablation. 3) However, the clinical recurrence rate was significantly lower in the IRAPB provocation group (15.0%) than in the No-Test group (28.0%; p=0.025) without lengthening of the procedure time or raising complication rate. Conclusion The presence of post-procedural IRAPB was associated with a higher recurrence rate after AF ablation. However, IRAPB provocation and additional ablation might facilitate a better clinical outcome. A further prospective randomized study is warranted. PMID:26632385

  4. Comparative analysis of the biaxial mechanical behavior of carotid wall tissue and biological and synthetic materials used for carotid patch angioplasty.

    PubMed

    Kamenskiy, Alexey V; Pipinos, Iraklis I; MacTaggart, Jason N; Kazmi, Syed A Jaffar; Dzenis, Yuris A

    2011-11-01

    Patch angioplasty is the most common technique used for the performance of carotid endarterectomy. A large number of patching materials are available for use while new materials are being continuously developed. Surprisingly little is known about the mechanical properties of these materials and how these properties compare with those of the carotid artery wall. Mismatch of the mechanical properties can produce mechanical and hemodynamic effects that may compromise the long-term patency of the endarterectomized arterial segment. The aim of this paper was to systematically evaluate and compare the biaxial mechanical behavior of the most commonly used patching materials. We compared PTFE (n  =  1), Dacron (n  =  2), bovine pericardium (n  =  10), autogenous greater saphenous vein (n  =  10), and autogenous external jugular vein (n  =  9) with the wall of the common carotid artery (n  =  18). All patching materials were found to be significantly stiffer than the carotid wall in both the longitudinal and circumferential directions. Synthetic patches demonstrated the most mismatch in stiffness values and vein patches the least mismatch in stiffness values compared to those of the native carotid artery. All biological materials, including the carotid artery, demonstrated substantial nonlinearity, anisotropy, and variability; however, the behavior of biological and biologically-derived patches was both qualitatively and quantitatively different from the behavior of the carotid wall. The majority of carotid arteries tested were stiffer in the circumferential direction, while the opposite anisotropy was observed for all types of vein patches and bovine pericardium. The rates of increase in the nonlinear stiffness over the physiological stress range were also different for the carotid and patching materials. Several carotid wall samples exhibited reverse anisotropy compared to the average behavior of the carotid tissue. A similar characteristic was

  5. Porous wall hollow glass microspheres as a medium or substrate for storage and formation of novel materials

    DOEpatents

    Wicks, George G; Serkiz, Steven M.; Zidan, Ragaiy; Heung, Leung K.

    2014-06-24

    Porous wall hollow glass microspheres are provided as a template for formation of nanostructures such as carbon nanotubes, In addition, the carbon nanotubes in combination with the porous wall hollow glass microsphere provides an additional reaction template with respect to carbon nanotubes.

  6. Ultrafast laser ablation for targeted atherosclerotic plaque removal

    NASA Astrophysics Data System (ADS)

    Lanvin, Thomas; Conkey, Donald B.; Descloux, Laurent; Frobert, Aurelien; Valentin, Jeremy; Goy, Jean-Jacques; Cook, Stéphane; Giraud, Marie-Noelle; Psaltis, Demetri

    2015-07-01

    Coronary artery disease, the main cause of heart disease, develops as immune cells and lipids accumulate into plaques within the coronary arterial wall. As a plaque grows, the tissue layer (fibrous cap) separating it from the blood flow becomes thinner and increasingly susceptible to rupturing and causing a potentially lethal thrombosis. The stabilization and/or treatment of atherosclerotic plaque is required to prevent rupturing and remains an unsolved medical problem. Here we show for the first time targeted, subsurface ablation of atherosclerotic plaque using ultrafast laser pulses. Excised atherosclerotic mouse aortas were ablated with ultrafast near-infrared (NIR) laser pulses. The physical damage was characterized with histological sections of the ablated atherosclerotic arteries from six different mice. The ultrafast ablation system was integrated with optical coherence tomography (OCT) imaging for plaque-specific targeting and monitoring of the resulting ablation volume. We find that ultrafast ablation of plaque just below the surface is possible without causing damage to the fibrous cap, which indicates the potential use of ultrafast ablation for subsurface atherosclerotic plaque removal. We further demonstrate ex vivo subsurface ablation of a plaque volume through a catheter device with the high-energy ultrafast pulse delivered via hollow-core photonic crystal fiber.

  7. Streaked radiography measurements of convergent ablator performance (invited)

    SciTech Connect

    Hicks, D. G.; Spears, B. K.; Braun, D. G.; Olson, R. E.; Sorce, C. M.; Celliers, P. M.; Collins, G. W.; Landen, O. L.

    2010-10-15

    The velocity and remaining ablator mass of an imploding capsule are critical metrics for assessing the progress toward ignition of an inertially confined fusion experiment. These and other ablator rocket parameters have been measured using a single streaked x-ray radiograph. A regularization technique has been used to determine the ablator density profile {rho}(r) at each time step; moments of {rho}(r) then provide the areal density, average radius, and mass of the unablated, or remaining, ablator material, with the velocity determined from the time derivative of the average radius. The technique has been implemented on experiments at the OMEGA laser facility.

  8. Femtosecond laser lithotripsy: feasibility and ablation mechanism

    NASA Astrophysics Data System (ADS)

    Qiu, Jinze; Teichman, Joel M. H.; Wang, Tianyi; Neev, Joseph; Glickman, Randolph D.; Chan, Kin Foong; Milner, Thomas E.

    2010-03-01

    Light emitted from a femtosecond laser is capable of plasma-induced ablation of various materials. We tested the feasibility of utilizing femtosecond-pulsed laser radiation (λ=800 nm, 140 fs, 0.9 mJ/pulse) for ablation of urinary calculi. Ablation craters were observed in human calculi of greater than 90% calcium oxalate monohydrate (COM), cystine (CYST), or magnesium ammonium phosphate hexahydrate (MAPH). Largest crater volumes were achieved on CYST stones, among the most difficult stones to fragment using Holmium:YAG (Ho:YAG) lithotripsy. Diameter of debris was characterized using optical microscopy and found to be less than 20 μm, substantially smaller than that produced by long-pulsed Ho:YAG ablation. Stone retropulsion, monitored by a high-speed camera system with a spatial resolution of 15 μm, was negligible for stones with mass as small as 0.06 g. Peak shock wave pressures were less than 2 bars, measured by a polyvinylidene fluoride (PVDF) needle hydrophone. Ablation dynamics were visualized and characterized with pump-probe imaging and fast flash photography and correlated to shock wave pressures. Because femtosecond-pulsed laser ablates urinary calculi of soft and hard compositions, with micron-sized debris, negligible stone retropulsion, and small shock wave pressures, we conclude that the approach is a promising candidate technique for lithotripsy.

  9. [The use of prosthetic materials placed intraperitoneally in the repair of large defects of the abdominal wall, reflections on a limited case series].

    PubMed

    Miro, A G; Auciello, I; Loffredo, D; Arenga, G; Lombardi, D

    1999-01-01

    To evaluate the best prosthetic material in direct contact with intestinal loops in the repair of large abdominal wall defects, four cases were reevaluated and an extensive review of the literature was undertake to point out the pathophysiology of prosthetic materials in abdominal wall surgery. For its intrinsic features, Gore-Tex represents the best prosthetic material to locate intraperitoneally, but the slow foreign body reaction is responsible for postoperative complications (e.g. hematoma, seroma, dehiscence). Marlex should not be used in direct contact with intestine because of the risk of multiple fistulas, very difficult to treat, while, the intense foreign body reaction rapidly integrate the mesh into the abdominal wall. To treat large abdominal wall defects are now been proposed mixed prostheses (Gore-Tex in intraperitoneal location, Marlex at the exterior) and dual mesh Gore-Tex (two textures at different microporosity on each side of the mesh). Preliminary studies have shown the safety and utility of these prostheses. PMID:10434463

  10. Flexible Ablators: Applications and Arcjet Testing

    NASA Technical Reports Server (NTRS)

    Arnold, James O.; Venkatapathy, Ethiraj; Beck, Robin A S.; Mcguire, Kathy; Prabhu, Dinesh K.; Gorbunov, Sergey

    2011-01-01

    Flexible ablators were conceived in 2009 to meet the technology pull for large, human Mars Exploration Class, 23 m diameter hypersonic inflatable aerodynamic decelerators. As described elsewhere, they have been recently undergoing initial technical readiness (TRL) advancement by NASA. The performance limits of flexible ablators in terms of maximum heat rates, pressure and shear remain to be defined. Further, it is hoped that this emerging technology will vastly expand the capability of future NASA missions involving atmospheric entry systems. This paper considers four topics of relevance to flexible ablators: (1) Their potential applications to near/far term human and robotic missions (2) Brief consideration of the balance between heat shield diameter, flexible ablator performance limits, entry vehicle controllability and aft-body shear layer impingement of interest to designers of very large entry vehicles, (3) The approach for developing bonding processes of flexible ablators for use on rigid entry bodies and (4) Design of large arcjet test articles that will enable the testing of flexible ablators in flight-like, combined environments (heat flux, pressure, shear and structural tensile loading). Based on a review of thermal protection system performance requirements for future entry vehicles, it is concluded that flexible ablators have broad applications to conventional, rigid entry body systems and are enabling to large deployable (both inflatable and mechanical) heat shields. Because of the game-changing nature of flexible ablators, it appears that NASA's Office of the Chief Technologist (OCT) will fund a focused, 3-year TRL advancement of the new materials capable of performance in heat fluxes in the range of 200-600 W/sq. cm. This support will enable the manufacture and use of the large-scale arcjet test designs that will be a key element of this OCT funded activity.

  11. Testing of Advanced Conformal Ablative TPS

    NASA Technical Reports Server (NTRS)

    Gasch, Matthew; Agrawal, Parul; Beck, Robin

    2013-01-01

    In support of the CA250 project, this paper details the results of a test campaign that was conducted at the Ames Arcjet Facility, wherein several novel low density thermal protection (TPS) materials were evaluated in an entry like environment. The motivation for these tests was to investigate whether novel conformal ablative TPS materials can perform under high heat flux and shear environment as a viable alternative to rigid ablators like PICA or Avcoat for missions like MSL and beyond. A conformable TPS over a rigid aeroshell has the potential to solve a number of challenges faced by traditional rigid TPS materials (such as tiled Phenolic Impregnated Carbon Ablator (PICA) system on MSL, and honeycomb-based Avcoat on the Orion Multi Purpose Crew Vehicle (MPCV)). The compliant (high strain to failure) nature of the conformable ablative materials will allow better integration of the TPS with the underlying aeroshell structure and enable monolithic-like configuration and larger segments to be used in fabrication.A novel SPRITE1 architecture, developed by the researchers at NASA Ames was used for arcjet testing. This small probe like configuration with 450 spherecone, enabled us to test the materials in a combination of high heat flux, pressure and shear environment. The heat flux near the nose were in the range of 500-1000 W/sq cm whereas in the flank section of the test article the magnitudes were about 50 of the nose, 250-500W/sq cm range. There were two candidate conformable materials under consideration for this test series. Both test materials are low density (0.28 g/cu cm) similar to Phenolic Impregnated Carbon Ablator (PICA) or Silicone Impregnated Refractory Ceramic Ablator (SIRCA) and are comprised of: A flexible carbon substrate (Carbon felt) infiltrated with an ablative resin system: phenolic (Conformal-PICA) or silicone (Conformal-SICA). The test demonstrated a successful performance of both the conformable ablators for heat flux conditions between 50

  12. A New Ablative Heat Shield Sensor Suite Project

    NASA Technical Reports Server (NTRS)

    Bose, Deepak

    2014-01-01

    A new sensor suite is developed to measure performance of ablative thermal protection systems used in planetary entry vehicles for robotic and human exploration. The new sensor suite measures ablation of the thermal protection system under extreme heating encountered during planetary entry. The sensor technology is compatible with a variety of thermal protection materials, and is applicable over a wide range of entry conditions.

  13. Ablative shielding for hypervelocity projectiles

    NASA Technical Reports Server (NTRS)

    Rucker, Michelle A. (Inventor)

    1993-01-01

    A hypervelocity projectile shield which includes a hollow semi-flexible housing fabricated from a plastic like, or otherwise transparent membrane which is filled with a fluid (gas or liquid) is presented. The housing has a inlet valve, similar to that on a tire or basketball, to introduce an ablating fluid into the housing. The housing is attached by a Velcro mount or double-sided adhesive tape to the outside surface of a structure to be protected. The housings are arrayed in a side-by-side relationship for complete coverage of the surface to be protected. In use, when a hypervelocity projectile penetrates the outer wall of a housing it is broken up and then the projectile is ablated as it travels through the fluid, much like a meteorite 'burns up' as it enters the earth's atmosphere, and the housing is deflated. The deflated housing can be easily spotted for replacement, even from a distance. Replacement is then accomplished by simply pulling a deflated housing off the structure and installing a new housing.

  14. Higher Order Chemistry Models in the CFD Simulation of Laser-Ablated Carbon Plumes

    NASA Technical Reports Server (NTRS)

    Greendyke, R. B.; Creel, J. R.; Payne, B. T.; Scott, C. D.

    2005-01-01

    Production of single-walled carbon nanotubes (SWNT) has taken place for a number of years and by a variety of methods such as laser ablation, chemical vapor deposition, and arc-jet ablation. Yet, little is actually understood about the exact chemical kinetics and processes that occur in SWNT formation. In recent time, NASA Johnson Space Center has devoted a considerable effort to the experimental evaluation of the laser ablation production process for SWNT originally developed at Rice University. To fully understand the nature of the laser ablation process it is necessary to understand the development of the carbon plume dynamics within the laser ablation oven. The present work is a continuation of previous studies into the efforts to model plume dynamics using computational fluid dynamics (CFD). The ultimate goal of the work is to improve understanding of the laser ablation process, and through that improved understanding, refine the laser ablation production of SWNT.

  15. Tumor Ablation and Nanotechnology

    PubMed Central

    Manthe, Rachel L.; Foy, Susan P.; Krishnamurthy, Nishanth; Sharma, Blanka; Labhasetwar, Vinod

    2010-01-01

    Next to surgical resection, tumor ablation is a commonly used intervention in the treatment of solid tumors. Tumor ablation methods include thermal therapies, photodynamic therapy, and reactive oxygen species (ROS) producing agents. Thermal therapies induce tumor cell death via thermal energy and include radiofrequency, microwave, high intensity focused ultrasound, and cryoablation. Photodynamic therapy and ROS producing agents cause increased oxidative stress in tumor cells leading to apoptosis. While these therapies are safe and viable alternatives when resection of malignancies is not feasible, they do have associated limitations that prevent their widespread use in clinical applications. To improve the efficacy of these treatments, nanoparticles are being studied in combination with nonsurgical ablation regimens. In addition to better thermal effect on tumor ablation, nanoparticles can deliver anticancer therapeutics that show synergistic anti-tumor effect in the presence of heat and can also be imaged to achieve precision in therapy. Understanding the molecular mechanism of nanoparticle-mediated tumor ablation could further help engineer nanoparticles of appropriate composition and properties to synergize the ablation effect. This review aims to explore the various types of nonsurgical tumor ablation methods currently used in cancer treatment and potential improvements by nanotechnology applications. PMID:20866097

  16. Ablative Rocket Deflector Testing and Computational Modeling

    NASA Technical Reports Server (NTRS)

    Allgood, Daniel C.; Lott, Jeffrey W.; Raines, Nickey

    2010-01-01

    A deflector risk mitigation program was recently conducted at the NASA Stennis Space Center. The primary objective was to develop a database that characterizes the behavior of industry-grade refractory materials subjected to rocket plume impingement conditions commonly experienced on static test stands. The program consisted of short and long duration engine tests where the supersonic exhaust flow from the engine impinged on an ablative panel. Quasi time-dependent erosion depths and patterns generated by the plume impingement were recorded for a variety of different ablative materials. The erosion behavior was found to be highly dependent on the material s composition and corresponding thermal properties. For example, in the case of the HP CAST 93Z ablative material, the erosion rate actually decreased under continued thermal heating conditions due to the formation of a low thermal conductivity "crystallization" layer. The "crystallization" layer produced near the surface of the material provided an effective insulation from the hot rocket exhaust plume. To gain further insight into the complex interaction of the plume with the ablative deflector, computational fluid dynamic modeling was performed in parallel to the ablative panel testing. The results from the current study demonstrated that locally high heating occurred due to shock reflections. These localized regions of shock-induced heat flux resulted in non-uniform erosion of the ablative panels. In turn, it was observed that the non-uniform erosion exacerbated the localized shock heating causing eventual plume separation and reversed flow for long duration tests under certain conditions. Overall, the flow simulations compared very well with the available experimental data obtained during this project.

  17. Fluidized wall for protecting fusion chamber walls

    SciTech Connect

    Maniscalco, J.A.; Meier, W.R.

    1982-08-17

    Apparatus for protecting the inner wall of a fusion chamber from microexplosion debris, x-rays, neutrons, etc. Produced by deuterium-tritium (DT) targets imploded within the fusion chamber. The apparatus utilizes a fluidized wall similar to a waterfall comprising liquid lithium or solid pellets of lithiumceramic, the waterfall forming a blanket to prevent damage of the structural materials of the chamber.

  18. Effect of Temperature on the Desorption of Lithium from Molybdenum(110) Surfaces: Implications for Fusion Reactor First Wall Materials.

    PubMed

    Chen, Mohan; Roszell, John; Scoullos, Emanuel V; Riplinger, Christoph; Koel, Bruce E; Carter, Emily A

    2016-07-01

    Determining the strength of Li binding to Mo is critical to assessing the survivability of Li as a potential first wall material in fusion reactors. We present the results of a joint experimental and theoretical investigation into how Li desorbs from Mo(110) surfaces, based on what can be deduced from temperature-programmed desorption measurements and density functional theory (DFT). Li desorption peaks measured at temperatures ranging from 711 K (1 monolayer, ML) to 1030 K (0.04 ML), with corresponding desorption onsets from 489 to 878 K, follow a trend similar to predicted Gibbs free energies for Li adsorption. Bader charge analysis of DFT densities reveals that repulsive forces between neighboring positively charged Li atoms increase with coverage and thus reduce the bond strength between Mo and Li, thereby lowering the desorption temperature as the coverage increases. Additionally, DFT predicts that Li desorbs at higher temperatures from a surface with vacancies than from a perfect surface, offering an explanation for the anomalously high desorption temperatures for the last Li to desorb from Mo(110). Analysis of simulated local densities of states indicates that the stronger binding to the defective surface is correlated with enhanced interaction between Li and Mo, involving the Li 2s electrons and not only the Mo 4d electrons as in the case of the pristine surface, but also the Mo 5s electrons in the case with surface vacancies. We suggest that steps and kinks present on the Mo(110) surface behave similarly and contribute to the high desorption temperatures. These findings imply that roughened Mo surfaces may strengthen Li film adhesion at higher temperatures. PMID:27027820

  19. Navigation Systems for Ablation

    PubMed Central

    Wood, B. J.; Kruecker, J.; Abi-Jaoudeh, N; Locklin, J.; Levy, E.; Xu, S.; Solbiati, L.; Kapoor, A.; Amalou, H.; Venkatesan, A.

    2010-01-01

    Navigation systems, devices and intra-procedural software are changing the way we practice interventional oncology. Prior to the development of precision navigation tools integrated with imaging systems, thermal ablation of hard-to-image lesions was highly dependent upon operator experience, spatial skills, and estimation of positron emission tomography-avid or arterial-phase targets. Numerous navigation systems for ablation bring the opportunity for standardization and accuracy that extends our ability to use imaging feedback during procedures. Existing systems and techniques are reviewed, and specific clinical applications for ablation are discussed to better define how these novel technologies address specific clinical needs, and fit into clinical practice. PMID:20656236

  20. Ablation of kidney tumors.

    PubMed

    Karam, Jose A; Ahrar, Kamran; Matin, Surena F

    2011-04-01

    While surgical excision remains the gold standard for curative treatment of small renal cell carcinomas, ablative therapy has a place as a minimally invasive, kidney function-preserving therapy in carefully selected patients who are poor candidates for surgery. Although laparoscopic cryoablation and percutaneous radiofrequency ablation (RFA) are commonly performed, percutaneous cryoablation and laparoscopic RFA are reportedly being performed with increasing frequency. The renal function and complication profiles following ablative therapy are favorable, while oncologic outcomes lag behind those of surgery, thus reinforcing the need for careful patient selection. PMID:21377587

  1. Numerical Modeling of Ablation Heat Transfer

    NASA Technical Reports Server (NTRS)

    Ewing, Mark E.; Laker, Travis S.; Walker, David T.

    2013-01-01

    A unique numerical method has been developed for solving one-dimensional ablation heat transfer problems. This paper provides a comprehensive description of the method, along with detailed derivations of the governing equations. This methodology supports solutions for traditional ablation modeling including such effects as heat transfer, material decomposition, pyrolysis gas permeation and heat exchange, and thermochemical surface erosion. The numerical scheme utilizes a control-volume approach with a variable grid to account for surface movement. This method directly supports implementation of nontraditional models such as material swelling and mechanical erosion, extending capabilities for modeling complex ablation phenomena. Verifications of the numerical implementation are provided using analytical solutions, code comparisons, and the method of manufactured solutions. These verifications are used to demonstrate solution accuracy and proper error convergence rates. A simple demonstration of a mechanical erosion (spallation) model is also provided to illustrate the unique capabilities of the method.

  2. Compositional analysis of Chinese water chestnut (Eleocharis dulcis) cell-wall material from parenchyma, epidermis, and subepidermal tissues.

    PubMed

    Grassby, Terri; Jay, Andrew J; Merali, Zara; Parker, Mary L; Parr, Adrian J; Faulds, Craig B; Waldron, Keith W

    2013-10-01

    Chinese water chestnut (Eleocharis dulcis (Burman f.) Trin ex Henschel) is a corm consumed globally in Oriental-style cuisine. The corm consists of three main tissues, the epidermis, subepidermis, and parenchyma; the cell walls of which were analyzed for sugar, phenolic, and lignin content. Sugar content, measured by gas chromatography, was higher in the parenchyma cell walls (931 μg/mg) than in the subepidermis (775 μg/mg) or epidermis (685 μg/mg). The alkali-extractable phenolic content, measured by high-performance liquid chromatography, was greater in the epidermal (32.4 μg/mg) and subepidermal cell walls (21.7 μg/mg) than in the cell walls of the parenchyma (12.3 μg/mg). The proportion of diferulic acids was higher in the parenchyma. The Klason lignin content of epidermal and subepidermal cell walls was ~15%. Methylation analysis of Chinese water chestnut cell-wall polysaccharides identified xyloglucan as the predominant hemicellulose in the parenchyma for the first time, and also a significant pectin component, similar to other nongraminaceous monocots. PMID:24066627

  3. Numerical simulations of the flow of wood polypropylene composites with wall slipping in a profile die: The significance of material data

    NASA Astrophysics Data System (ADS)

    Gooneie, Ali; Schuschnigg, Stephan; Duretek, Ivica; Holzer, Clemens

    2015-05-01

    This paper demonstrates the importance of the careful selection of the input material data for the calculation of the flow behavior of wood polypropylene composites. To this goal, the rheological data of un-dried samples were measured, utilizing a commercial high pressure capillary rheometer equipped with slit dies of different gap heights. The data were incorporated in finite-difference and finite-element methods in order to predict the pressure drop along a profile die and compared to measurements on an extruder at different flow rates. While the un-dried sample is expected to undergo wall slippage during flow, the simulation results on the slit and profile dies indicate that neither a fully slipping plug flow nor a fully adhering shear flow is capable of providing reasonable results. By utilizing ANSYS Polyflow software, a combination of both flow types was incorporated in a 3-dimensional FEM analysis to simulate the pressure drops. The results show that by using the shear viscosity data from capillary measurements the calculated pressure drops are lower than the experimental data and close to the fully shear flow case. It was noted that the traditional experimental method of shear viscosity measurement could not be applied in the presence of wall slippage phenomenon due to the fact that the entire velocity profile in the slit die changes and the resulting flow curves of the material is gap-dependent. Therefore, an optimization procedure was used to evaluate the shear viscosity which was found to be capable of capturing the flow behavior of the material in the presence of wall slippage. This research clearly points out the significance of using a combination of shear and plug flows in such simulations through applying shear viscosity and wall slippage coefficients, respectively. Moreover, it emphasizes that the data from the capillary rheometry should be treated carefully in the presence of the wall slip.

  4. Factors influencing the ablative efficiency of high intensity focused ultrasound (HIFU) treatment for adenomyosis: A retrospective study.

    PubMed

    Gong, Chunmei; Yang, Bin; Shi, Yarong; Liu, Zhongqiong; Wan, Lili; Zhang, Hong; Jiang, Denghua; Zhang, Lian

    2016-08-01

    Objectives The aim of this study was to investigate factors affecting ablative efficiency of high intensity focused ultrasound (HIFU) for adenomyosis. Materials and methods In all, 245 patients with adenomyosis who underwent ultrasound guided HIFU (USgHIFU) were retrospectively reviewed. All patients underwent dynamic contrast-enhanced magnetic resonance imaging (MRI) before and after HIFU treatment. The non-perfused volume (NPV) ratio, energy efficiency factor (EEF) and greyscale change were set as dependent variables, while the factors possibly affecting ablation efficiency were set as independent variables. These variables were used to build multiple regression models. Results A total of 245 patients with adenomyosis successfully completed HIFU treatment. Enhancement type on T1 weighted image (WI), abdominal wall thickness, volume of adenomyotic lesion, the number of hyperintense points, location of the uterus, and location of adenomyosis all had a linear relationship with the NPV ratio. Distance from skin to the adenomyotic lesion's ventral side, enhancement type on T1WI, volume of adenomyotic lesion, abdominal wall thickness, and signal intensity on T2WI all had a linear relationship with EEF. Location of the uterus and abdominal wall thickness also both had a linear relationship with greyscale change. Conclusion The enhancement type on T1WI, signal intensity on T2WI, volume of adenomyosis, location of the uterus and adenomyosis, number of hyperintense points, abdominal wall thickness, and distance from the skin to the adenomyotic lesion's ventral side can all be used as predictors of HIFU for adenomyosis. PMID:27385316

  5. Improved laser ablation model for asteroid deflection

    NASA Astrophysics Data System (ADS)

    Vasile, Massimiliano; Gibbings, Alison; Watson, Ian; Hopkins, John-Mark

    2014-10-01

    This paper presents an improved laser ablation model and compares the performance - momentum coupling and deflection system mass - of laser ablation against contactless deflection methods based on ion-propulsion. The deflection of an asteroid through laser ablation is achieved by illuminating the surface of the asteroid with high intensity laser light. The absorbed energy induces the sublimation of the surface material and the generation of a plume of gas and ejecta. Similar to a rocket engine, the flow of expelled material produces a continuous and controllable thrust that could be used to modify the trajectory and tumbling motion of the asteroid. Recent results gained from a series of laser ablation experiments were used to improve the sublimation and deflection models. In each experiment a terrestrial olivine sample was ablated, under vacuum, with a 90 W continuous wave laser. The paper presents a model that better fits the outcomes of the experimental campaign, in particular in terms of mass flow rate and spot temperature.

  6. Ventricular dysfunction following direct-current shock atrioventricular junction ablation.

    PubMed

    Warren, R J; Vohra, J K; Chan, W; Lichtenstein, M; Mond, H G; Hunt, D

    1991-02-01

    Catheter-induced His bundle ablation for refractory supraventricular arrhythmias is most commonly performed with direct-current shock energy of 200-300 joules. The high energy pulse delivered by direct-current shock produces a lesion in the atrioventricular node by fulguration, with the residual energy being dissipated as a pressure wave. The effect of direct-current shock His bundle ablation on global and regional ventricular function was assessed in 14 consecutive patients by radionuclide ventriculography performed before and after ablation and again three months later. All studies were performed with ventricular pacing at 110 bpm. Global left ventricular ejection fraction was found to be significantly reduced at the three month study (0.43 +/- 0.03 vs 0.50 +/- 0.03, pre ablation, p = 0.02). A significant reduction in wall-motion score was also seen in six of the seven patients who had normal wall motion in pacing rhythm prior to ablation. Deterioration was mainly seen at the left and right ventricular apices. The observed reduction in ventricular function that follows direct-current shock His bundle ablation may result from myocardial damage from electro-coagulation or from barotrauma and supports continued investigation into alternative, less traumatic energy sources for the procedure. PMID:2036072

  7. Ablative skin resurfacing.

    PubMed

    Agrawal, Nidhi; Smith, Greg; Heffelfinger, Ryan

    2014-02-01

    Ablative laser resurfacing has evolved as a safe and effective treatment for skin rejuvenation. Although traditional lasers were associated with significant thermal damage and lengthy recovery, advances in laser technology have improved safety profiles and reduced social downtime. CO2 lasers remain the gold standard of treatment, and fractional ablative devices capable of achieving remarkable clinical improvement with fewer side effects and shorter recovery times have made it a more practical option for patients. Although ablative resurfacing has become safer, careful patient selection and choice of suitable laser parameters are essential to minimize complications and optimize outcomes. This article describes the current modalities used in ablative laser skin resurfacing and examines their efficacy, indications, and possible side effects. PMID:24488638

  8. Cardiac ablation procedures

    MedlinePlus

    ... Accessory pathway, such as Wolff-Parkinson-White Syndrome Atrial fibrillation and atrial flutter Ventricular tachycardia ... consensus statement on catheter and surgical ablation of atrial fibrillation: ... for personnel, policy, procedures and follow-up. ...

  9. Laser ablation loading of a surface-electrode ion trap

    SciTech Connect

    Leibrandt, David R.; Clark, Robert J.; Labaziewicz, Jaroslaw; Antohi, Paul; Bakr, Waseem; Brown, Kenneth R.; Chuang, Isaac L.

    2007-11-15

    We demonstrate loading of {sup 88}Sr{sup +} ions by laser ablation into a mm-scale surface-electrode ion trap. The laser used for ablation is a pulsed, frequency-tripled Nd:YAG with pulse energies of 1-10 mJ and durations of 4 ns. An additional laser is not required to photoionize the ablated material. The efficiency and lifetime of several candidate materials for the laser ablation target are characterized by measuring the trapped ion fluorescence signal for a number of consecutive loads. Additionally, laser ablation is used to load traps with a trap depth (40 meV) below where electron impact ionization loading is typically successful (> or approx. 500 meV)

  10. Chemical and Spectroscopic Aspects of Polymer Ablation-Special Features and Novel Directions-

    NASA Astrophysics Data System (ADS)

    Lippert, Thomas

    2004-03-01

    Laser ablation of polymers has become an established technique in the electronic industry and the large number of studies published annually indicates that this is still an attractive area of research. Several new approaches with new techniques and materials have given new insights in the ablation process. One of these approaches is the development of polymers designed specifically for laser ablation which are a unique tool for probing the ablation mechanisms as well as for improving ablation properties. These novel polymers exhibit very low thresholds of ablation, with high ablation rates (even at low fluences), and excellent ablation quality. New commercial applications will require improved ablation rates and control of undesirable surface effects, such as debris. The complexity of the interactions between polymers and laser photons are illustrated by the various processes associated with different irradiation conditions. i) Photothermal-photochemical laser ablation under excimer laser irradiation. ii) Dopant-induced laser ablation. iii) Photo-oxidative etching with lamps in an oxidizing atmosphere. iv) VUV etching in the absence of oxidizing conditions. v) Photokinetic etching with CW UV lasers. vi) Ultrafast laser ablation, affected by pulse length, wavelength, and possibly shock waves. vii) Shock assisted photothermal ablation on picosecond time scales. viii) VUV laser ablation: purely photochemical? ix) Synchrotron structuring. x) Mid-IR ablation (FEL and CO2 laser), the influence of exciting various functional groups. Several of these new approaches and processes will be discussed to emphasize the importance of different approaches but also to review some fundamental processes. The combination of various experimental techniques (new approaches and 'well-known') with materials made to measure has given new insights in the ablation mechanisms, but has also shown new possible future directions of laser polymer ablation.

  11. Plant material features responsible for bamboo's excellent mechanical performance: a comparison of tensile properties of bamboo and spruce at the tissue, fibre and cell wall levels

    PubMed Central

    Wang, Xiaoqing; Keplinger, Tobias; Gierlinger, Notburga; Burgert, Ingo

    2014-01-01

    Background and Aims Bamboo is well known for its fast growth and excellent mechanical performance, but the underlying relationships between its structure and properties are only partially known. Since it lacks secondary thickening, bamboo cannot use adaptive growth in the same way as a tree would in order to modify the geometry of the stem and increase its moment of inertia to cope with bending stresses caused by wind loads. Consequently, mechanical adaptation can only be achieved at the tissue level, and this study aims to examine how this is achieved by comparison with a softwood tree species at the tissue, fibre and cell wall levels. Methods The mechanical properties of single fibres and tissue slices of stems of mature moso bamboo (Phyllostachys pubescens) and spruce (Picea abies) latewood were investigated in microtensile tests. Cell parameters, cellulose microfibril angles and chemical composition were determined using light and electron microscopy, wide-angle X-ray scattering and confocal Raman microscopy. Key Results Pronounced differences in tensile stiffness and strength were found at the tissue and fibre levels, but not at the cell wall level. Thus, under tensile loads, the differing wall structures of bamboo (multilayered) and spruce (sandwich-like) appear to be of minor relevance. Conclusions The superior tensile properties of bamboo fibres and fibre bundles are mainly a result of amplified cell wall formation, leading to a densely packed tissue, rather than being based on specific cell wall properties. The material optimization towards extremely compact fibres with a multi-lamellar cell wall in bamboo might be a result of a plant growth strategy that compensates for the lack of secondary thickening growth at the tissue level, which is not only favourable for the biomechanics of the plant but is also increasingly utilized in terms of engineering products made from bamboo culms. PMID:25180290

  12. Suitability of a tumour-mimicking material for the evaluation of high-intensity focused ultrasound ablation under magnetic resonance guidance

    NASA Astrophysics Data System (ADS)

    Pichardo, S.; Kivinen, J.; Melodelima, D.; Curiel, L.

    2013-04-01

    This study tests the suitability of a tumour-mimic for targeting magnetic resonance (MR)-guided high-intensity focused ultrasound (HIFU). An agarose-based tumour-mimic was injected as a warm solution that polymerized in tissue. Thermal characteristics and acoustic absorption of the mimic were observed within the values reported for tissues. The relaxation times at 3T were 1679 ± 15 ms for T1 and 41 ± 1 ms for T2. The mimic was clearly visible on in vivo images. With lower contrast the tumour-mimic was visible on T2-weighted images, where it was possible to detect the ablated tissue surrounding the mimic after sonications. HIFU sonications were performed to induce thermal ablation on and around the mimic using a Sonalleve system (Philips). MR thermometry maps were performed during HIFU. The average temperature when the sonication was done at the tumour-mimic was 67.6 ± 8.0 °C in vitro and 67.6 ± 5.0 °C in vivo. The average temperature for sonications at tissues was 68.4 ± 8.7 °C in vitro (liver) and 66.0 ± 2.6 °C in vivo (muscle), with no significant difference between tissue and tumour-mimic (p > 0.05). The tumour-mimic behaviour when using MR-guided HIFU was similar to tissues, showing that this mimic can be used as an alternative to tumour models for validating MR-guided HIFU devices targeting.

  13. Metal particles produced by laser ablation for ICP-MSmeasurements

    SciTech Connect

    Gonzalez, Jhanis J.; Liu, Chunyi; Wen, Sy-Bor; Mao, Xianglei; Russo, Richard E.

    2007-06-01

    Pulsed laser ablation (266nm) was used to generate metal particles of Zn and Al alloys using femtosecond (150 fs) and nanosecond (4 ns) laser pulses with identical fluences of 50 J cm{sup -2}. Characterization of particles and correlation with Inductively Coupled Plasma Mass Spectrometer (ICP-MS) performance was investigated. Particles produced by nanosecond laser ablation were mainly primary particles with irregular shape and hard agglomerates (without internal voids). Particles produced by femtosecond laser ablation consisted of spherical primary particles and soft agglomerates formed from numerous small particles. Examination of the craters by white light interferometric microscopy showed that there is a rim of material surrounding the craters formed after nanosecond laser ablation. The determination of the crater volume by white light interferometric microscopy, considering the rim of material surrounding ablation craters, revealed that the volume ratio (fs/ns) of the craters on the selected samples was approximately 9 (Zn), 7 (NIST627 alloy) and 5 (NIST1711 alloy) times more ablated mass with femtosecond pulsed ablation compared to nanosecond pulsed ablation. In addition, an increase of Al concentration from 0 to 5% in Zn base alloys caused a large increase in the diameter of the particles, up to 65% while using nanosecond laser pulses. When the ablated particles were carried in argon into an ICP-MS, the Zn and Al signals intensities were greater by factors of {approx} 50 and {approx} 12 for fs vs. ns ablation. Femtosecond pulsed ablation also reduced temporal fluctuations in the {sup 66}Zn transient signal by a factor of ten compared to nanosecond laser pulses.

  14. Ultrashort laser ablation of PMMA and intraocular lenses

    NASA Astrophysics Data System (ADS)

    Serafetinides, A. A.; Makropoulou, M.; Fabrikesi, E.; Spyratou, E.; Bacharis, C.; Thomson, R. R.; Kar, A. K.

    2008-10-01

    The use of intraocular lenses (IOLs) is the most promising method to restore vision after cataract surgery. Several new materials, techniques, and patterns have been studied for forming and etching IOLs to improve their optical properties and reduce diffractive aberrations. This study is aimed at investigating the use of ultrashort laser pulses to ablate the surface of PMMA and intraocular lenses, and thus provide an alternative to conventional techniques. Ablation experiments were conducted using various polymer substrates (PMMA samples, hydrophobic acrylic IOL, yellow azo dye doped IOL, and hydrophilic acrylic IOL consist of 25% H2O). The irradiation was performed using 100 fs pulses of 800 nm radiation from a regeneratively amplified Ti:sapphire laser system. We investigated the ablation efficiency and the phenomenology of the ablated patterns by probing the ablation depth using a profilometer. The surface modification was examined using a high resolution optical microscope (IOLs) or atomic force microscope—AFM (PMMA samples). It was found that different polymers exhibited different ablation characteristics, a result that we attribute to the differing optical properties of the materials. In particular, it was observed that the topography of the ablation tracks created on the hydrophilic intraocular lenses was smoother in comparison to those created on the PMMA and hydrophobic lens. The yellow doped hydrophobic intraocular lenses show higher ablation efficiency than undoped hydrophobic acrylic lenses.

  15. General Model for Multicomponent Ablation Thermochemistry

    NASA Technical Reports Server (NTRS)

    Milos, Frank S.; Marschall, Jochen; Rasky, Daniel J. (Technical Monitor)

    1994-01-01

    A previous paper (AIAA 94-2042) presented equations and numerical procedures for modeling the thermochemical ablation and pyrolysis of thermal protection materials which contain multiple surface species. This work describes modifications and enhancements to the Multicomponent Ablation Thermochemistry (MAT) theory and code for application to the general case which includes surface area constraints, rate limited surface reactions, and non-thermochemical mass loss (failure). Detailed results and comparisons with data are presented for the Shuttle Orbiter reinforced carbon-carbon oxidation protection system which contains a mixture of sodium silicate (Na2SiO3), silica (SiO2), silicon carbide (SiC), and carbon (C).

  16. A simulation study to compare the phase-shift angle radiofrequency ablation mode with bipolar and unipolar modes in creating linear lesions for atrial fibrillation ablation.

    PubMed

    Yan, Shengjie; Wu, Xiaomei; Wang, Weiqi

    2016-05-01

    Purpose In pulmonary veins (PVs) isolation (PVI), radiofrequency (RF) energy is often used to create a linear lesion for blocking the accessory conduction pathways around PVs. By using transient finite element analysis, this study compared the effectiveness of phase-shift mode (PsM) ablation with bipolar mode (BiM) and unipolar mode (UiM) in creating a continuous lesion and lesion depth in a 5-mm thick atrial wall. Materials and methods Computer models were developed to study the temperature distributions and lesion dimensions in atrial walls created through PsM, BiM, and UiM. Four phase-shift angles - 45°, 90°, 135°, and 180° - were considered in PsM ablation (hereafter, PsM-45°, PsM-90°, PsM-135°, and PsM-180°, respectively). Results At 60 s/30 V peak value of RF voltage, UiM and PsM-45° did not create an effective lesion, whereas BiM created a lesion of maximum depth and width approximately 1.01 and 1.62 mm, respectively. PsM-135° and PsM-180° not only created transmural lesions in 5-mm thick atrial walls but also created continuous lesions between electrodes spaced 4 mm apart; similarly, PsM-90° created a continuous lesion with a maximum depth and width of nearly 4.09 and 6.12 mm. Conclusions Compared with UiM and BiM, PsM-90°, PsM-135° and PsM-180° created continuous and larger lesions in a single ablation procedure and at 60 s/30 V peak value of RF voltage. Therefore, the proposed PsM ablation method is suitable for PVI and linear isolation at the left atrial roof for treating atrial fibrillation. PMID:26915712

  17. [The incidence of ventricular arrhythmia following direct current ablation, high-frequency current ablation and laser photo-ablation].

    PubMed

    Hindricks, G; Haverkamp, W; Dute, U; Gülker, H

    1988-11-01

    Incidence and severity of ventricular arrhythmias (VA) following transvenous catheter ablation have so far not been fully elucidated. In the present study we evaluated the comparative incidence of postablation ventricular arrhythmias following high voltage-direct current electrical ablation (DCA), radiofrequency-ablation (RFA), and laser-photoablation (LPA). Experiments were performed on a total of 26 anesthetized mongrel dogs (BW: 20-30 kg). DCA (n = 14; 150-200 J) and RFA (n = 7; 38.5-72.5 J) were performed unipolarly via a 6F USCI catheter, LPA (n = 5; 40-80 J) was delivered through a quarz core fiber (diameter 0.4 mm) housed within a special designed catheter. Energies were delivered to various sites of free wall and apical endocardium of the left ventricle. Immediately after DCA fast runs of ventricular tachycardia (VT) developed in 13 out of 14 dogs degenerating into ventricular fibrillation in two animals. Mean cycle length of induced VT was 298 +/- 86 ms. Persistent VA, morphologically mainly characterized by an accelerated idioventricular rhythm interrupted by runs of ventricular salvoes, occurred in 12 animals (mean rate: 78 +/- 13 VPB/min 3 h after ablation). During VT early endocardial activations were recorded from the ablation site. No significant correlation between total applied energy (150-550 J) and incidence of arrhythmogenic effects was observed. RFA and LPA induced ventricular salvoes and runs of non-sustained ventricular tachycardia, in one animal ventricular fibrillation occurred during RFA; however, no persistent arrhythmic activity developed after RFA and LPA, respectively.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3213137

  18. Ablative therapies for renal tumors

    PubMed Central

    Ramanathan, Rajan; Leveillee, Raymond J.

    2010-01-01

    Owing to an increased use of diagnostic imaging for evaluating patients with other abdominal conditions, incidentally discovered kidney masses now account for a majority of renal tumors. Renal ablative therapy is assuming a more important role in patients with borderline renal impairment. Renal ablation uses heat or cold to bring about cell death. Radiofrequency ablation and cryoablation are two such procedures, and 5-year results are now emerging from both modalities. Renal biopsy at the time of ablation is extremely important in order to establish tissue diagnosis. Real-time temperature monitoring at the time of radiofrequency ablation is very useful to ensure adequacy of ablation. PMID:21789083

  19. Simulation of Double-Pulse Laser Ablation

    SciTech Connect

    Povarnitsyn, Mikhail E.; Khishchenko, Konstantin V.; Levashov, Pavel R.; Itina, Tatian E.

    2010-10-08

    We investigate the physical reasons of a strange decrease in the ablation depth observed in femtosecond double-pulse experiments with increasing delay between the pulses. Two ultrashort pulses of the same energy produce the crater which is less than that created by a single pulse. Hydrodynamic simulation shows that the ablation mechanism is suppressed when the delay between the pulses exceeds the electron-ion relaxation time. In this case, the interaction of the second laser pulse with the expanding target material leads to the formation of the second shock wave suppressing the rarefaction wave created by the first pulse. The modeling of the double-pulse ablation for different delays between pulses confirms this explanation.

  20. Specific Impulse Definition for Ablative Laser Propulsion

    NASA Technical Reports Server (NTRS)

    Herren, Kenneth A.; Gregory, Don A.

    2004-01-01

    The term "specific impulse" is so ingrained in the field of rocket propulsion that it is unlikely that any fundamental argument would be taken seriously for its removal. It is not an ideal measure but it does give an indication of the amount of mass flow (mass loss/time), as in fuel rate, required to produce a measured thrust over some time period This investigation explores the implications of being able to accurately measure the ablation rate and how the language used to describe the specific impulse results may have to change slightly, and recasts the specific impulse as something that is not a time average. It is not currently possible to measure the ablation rate accurately in real time so it is generally just assumed that a constant amount of material will be removed for each laser pulse delivered The specific impulse dependence on the ablation rate is determined here as a correction to the classical textbook definition.

  1. Low temperature ablation models made by pressure/vacuum application

    NASA Technical Reports Server (NTRS)

    Fischer, M. C.; Heier, W. C.

    1970-01-01

    Method developed employs high pressure combined with strong vacuum force to compact ablation models into desired conical shape. Technique eliminates vapor hazard and results in high material density providing excellent structural integrity.

  2. Transport properties associated with carbon-phenolic ablators

    NASA Technical Reports Server (NTRS)

    Biolsi, L.

    1982-01-01

    Entry vehicle heat shields designed for entry into the atmosphere of the outer planets are usually made of carbonaceous material such as carbon-phenolic ablator. Ablative injection of this material is an important mechanism for reducing the heat at the surface of the entry vehicle. Conductive transport properties in the shock layer are important for some entry conditions. The kinetic theory of gases has been used to calculate the transport properties for 17 gaseous species obtained from the ablation of carbon-phenolic heat shields. Results are presented for the pure species and for the gas mixture.

  3. Ablation by ultrashort laser pulses: Atomistic and thermodynamic analysis of the processes at the ablation threshold

    SciTech Connect

    Upadhyay, Arun K.; Inogamov, Nail A.; Rethfeld, Baerbel; Urbassek, Herbert M.

    2008-07-15

    Ultrafast laser irradiation of solids may ablate material off the surface. We study this process for thin films using molecular-dynamics simulation and thermodynamic analysis. Both metals and Lennard-Jones (LJ) materials are studied. We find that despite the large difference in thermodynamical properties between these two classes of materials--e.g., for aluminum versus LJ the ratio T{sub c}/T{sub tr} of critical to triple-point temperature differs by more than a factor of 4--the values of the ablation threshold energy E{sub abl} normalized to the cohesion energy, {epsilon}{sub abl}=E{sub abl}/E{sub coh}, are surprisingly universal: all are near 0.3 with {+-}30% scattering. The difference in the ratio T{sub c}/T{sub tr} means that for metals the melting threshold {epsilon}{sub m} is low, {epsilon}{sub m}<{epsilon}{sub abl}, while for LJ it is high, {epsilon}{sub m}>{epsilon}{sub abl}. This thermodynamical consideration gives a simple explanation for the difference between metals and LJ. It explains why despite the universality in {epsilon}{sub abl}, metals thermomechanically ablate always from the liquid state. This is opposite to LJ materials, which (near threshold) ablate from the solid state. Furthermore, we find that immediately below the ablation threshold, the formation of large voids (cavitation) in the irradiated material leads to a strong temporary expansion on a very slow time scale. This feature is easily distinguished from the acoustic oscillations governing the material response at smaller intensities, on the one hand, and the ablation occurring at larger intensities, on the other hand. This finding allows us to explain the puzzle of huge surface excursions found in experiments at near-threshold laser irradiation.

  4. Thermochemical Ablation Analysis of the Orion Heatshield

    NASA Technical Reports Server (NTRS)

    Sixel, William

    2015-01-01

    The Orion Multi-Purpose Crew Vehicle will one day carry astronauts to the Moon and beyond, and Orion's heatshield is a critical component in ensuring their safe return to Earth. The Orion heatshield is the structural component responsible for absorbing the intense heating environment caused by re-entry to Earth's atmosphere. The heatshield is primarily composed of Avcoat, an ablative material that is consumed during the re-entry process. Ablation is primarily characterized by two processes: pyrolysis and recession. The decomposition of in-depth virgin material is known as pyrolysis. Recession occurs when the exposed surface of the heatshield reacts with the surrounding flow. The Orion heatshield design was changed from an individually filled Avcoat honeycomb to a molded block Avcoat design. The molded block Avcoat heatshield relies on an adhesive bond to keep it attached to the capsule. In some locations on the heatshield, the integrity of the adhesive bond cannot be verified. For these locations, a mechanical retention device was proposed. Avcoat ablation was modelled in CHAR and the in-depth virgin material temperatures were used in a Thermal Desktop model of the mechanical retention device. The retention device was analyzed and shown to cause a large increase in the maximum bondline temperature. In order to study the impact of individual ablation modelling parameters on the heatshield sizing process, a Monte Carlo simulation of the sizing process was proposed. The simulation will give the sensitivity of the ablation model to each of its input parameters. As part of the Monte Carlo simulation, statistical uncertainties on material properties were required for Avcoat. Several properties were difficult to acquire uncertainties for: the pyrolysis gas enthalpy, non-dimensional mass loss rate (B´c), and Arrhenius equation parameters. Variability in the elemental composition of Avcoat was used as the basis for determining the statistical uncertainty in pyrolysis gas

  5. Image guided thermal ablation of tumors increases the plasma level of IL-6 and IL-10

    PubMed Central

    Erinjeri, Joseph P; Thomas, Contessa T; Samoila, Alaiksandra; Fleisher, Martin; Gonen, Mithat; Sofocleous, Constantinos T.; Thornton, Raymond H; Siegelbaum, Robert H.; Covey, Anne M.; Brody, Lynn A.; Alago, William; Maybody, Majid; Brown, Karen T.; Getrajdman, George; Solomon, Stephen B.

    2014-01-01

    PURPOSE To identify changes in plasma cytokine levels following image-guided thermal ablation of human tumors and to identify the factors that independently predict changes in plasma cytokine levels. MATERIALS AND METHODS Whole blood samples were collected from 36 patients at 3 time points: pre-ablation, post-ablation (within 48 hours), and in follow-up (1–5 weeks after ablation). Plasma levels of IL-1a, IL-2, IL-6, IL-10 and TNFa were measured using a multiplex immunoassay. Univariate and multivariate analyses were performed using cytokine level as the dependent variable and sample collection, time, age, sex, primary diagnosis, metastatic status, ablation site, and ablation type as the independent variables. RESULTS There was a significant increase in the plasma level of IL-6 post-ablation when compared to pre-ablation (9.6+/−31 fold, p<0.002). IL-10 also showed a significant increase postablation (1.9 +/−2.8 fold, p<0.02). Plasma levels of IL-1a, IL-2, and TNFa were not significantly changed after ablation. Cryoablation resulted in the largest change in IL-6 level (>54 fold), while radiofrequency and microwave ablation showed 3.6 and 3.4-fold changes, respectively. Ablation of melanomas showed the largest change in IL-6 48 hours after ablation (92×), followed by ablation of kidney (26×), liver (8×), and lung (6×) cancers. Multivariate analysis revealed that ablation type (p<0.0003), and primary diagnosis (p<0.03) were independent predictors of changes to IL-6 following ablation. Age was the only independent predictor of IL-10 levels following ablation (p<0.019). CONCLUSION Image guided thermal ablation of tumors increases the plasma level of IL-6 and IL-10, without increasing the plasma level of IL-1a, IL-2, or TNFa. PMID:23582441

  6. Atrial fibrillation ablation.

    PubMed

    Pappone, Carlo; Santinelli, Vincenzo

    2012-06-01

    Atrial fibrillation is the commonest cardiac arrhythmia, with significant morbidity related to symptoms, heart failure, and thromboembolism, which is associated with excess mortality. Over the past 10 years, many centers worldwide have reported high success rates and few complications after a single ablation procedure in patients with paroxysmal atrial fibrillation. Recent studies indicate a short-term and long-term superiority of catheter ablation as compared with conventional antiarrhythmic drug therapy in terms of arrhythmia recurrence, quality of life, and arrhythmia progression. As a result, catheter ablation is evolving to a front-line therapy in many patients with atrial fibrillation. However, in patients with persistent long-standing atrial fibrillation catheter ablation strategy is more complex and time-consuming, frequently requiring repeat procedures to achieve success rates as high as in paroxysmal atrial fibrillation. In the near future, however, with growing experience and evolving technology, catheter ablation of atrial fibrillation may be extended also to patients with long-standing atrial fibrillation. PMID:22541284

  7. Infrared laser bone ablation

    SciTech Connect

    Nuss, R.C.; Fabian, R.L.; Sarkar, R.; Puliafito, C.A.

    1988-01-01

    The bone ablation characteristics of five infrared lasers, including three pulsed lasers (Nd:YAG, lambda = 1064 micron; Hol:YSGG, lambda = 2.10 micron; and Erb:YAG, lambda = 2.94 micron) and two continuous-wave lasers (Nd:YAG, lambda = 1.064 micron; and CO/sub 2/, lambda = 10.6 micron), were studied. All laser ablations were performed in vitro, using moist, freshly dissected calvarium of guinea pig skulls. Quantitative etch rates of the three pulsed lasers were calculated. Light microscopy of histologic sections of ablated bone revealed a zone of tissue damage of 10 to 15 micron adjacent to the lesion edge in the case of the pulsed Nd:YAG and the Erb:YAG lasers, from 20 to 90 micron zone of tissue damage for bone ablated by the Hol:YSGG laser, and 60 to 135 micron zone of tissue damage in the case of the two continuous-wave lasers. Possible mechanisms of bone ablation and tissue damage are discussed.

  8. Reflecting ablating heat shields for planetary entry.

    NASA Technical Reports Server (NTRS)

    Peterson, D. L.; Nachtsheim, P. R.; Howe, J. T.

    1972-01-01

    Heat shielding for planetary entry probes of future Jovian and Venusian missions will encounter heating levels well beyond those previously experienced. These entries are typically dominated by radiative heating from the shock layer. This paper demonstrates the potential of reflecting this incident radiation diffusely from an ablating material. This technique contrasts with the absorption experienced by char-forming or graphitic ablators. Two dielectric materials, Teflon (polytetra-fluoroethylene) and boron nitride, are examined for their ablative performance, including reflection, in a combined convective- and radiative-heating environment. For Teflon, at the conditions obtained, superimposition of radiative heating upon a convective stream causes no additional increase in surface recession over the convective only results. For boron nitride, an excellent room-temperature reflector in the visible spectrum, a decrease in reflectivity from 90 to 55 percent is experienced when the surface undergoes sublimation at high temperatures. The process of reflection in each of these materials is described in terms of backscattering from crystals. The significance of a sizable reflection as a mode of energy accommodation is demonstrated for Venusian entries as a potential reduction in mass loss due to ablation.

  9. Renal Artery Embolization Combined With Radiofrequency Ablation in a Porcine Kidney Model: Effect of Small and Narrowly Calibrated Microparticles as Embolization Material on Coagulation Diameter, Volume, and Shape

    SciTech Connect

    Sommer, C. M. Kortes, N.; Zelzer, S.; Arnegger, F. U.; Stampfl, U.; Bellemann, N.; Gehrig, T.; Nickel, F.; Kenngott, H. G.; Mogler, C.; Longerich, T.; Meinzer, H. P.; Richter, G. M.; Kauczor, H. U.; Radeleff, B. A.

    2011-02-15

    The purpose of this study was to evaluate the effect of renal artery embolization with small and narrowly calibrated microparticles on the coagulation diameter, volume, and shape of radiofrequency ablations (RFAs) in porcine kidneys. Forty-eight RFAs were performed in 24 kidneys of 12 pigs. In 6 animals, bilateral renal artery embolization was performed with small and narrowly calibrated microparticles. Upper and lower kidney poles were ablated with identical system parameters. Applying three-dimensional segmentation software, RFAs were segmented on registered 2 mm-thin macroscopic slices. Length, depth, width, volume{sub s}egmented, and volume{sub c}alculated were determined to describe the size of the RFAs. To evaluate the shape of the RFAs, depth-to-width ratio (perfect symmetry-to-lesion length was indicated by a ratio of 1), sphericity ratio (perfect sphere was indicated by a sphericity ratio of 1), eccentricity (perfect sphere was indicated by an eccentricity of 0), and circularity (perfect circle was indicated by a circularity of 1) were determined. Embolized compared with nonembolized RFAs showed significantly greater depth (23.4 {+-} 3.6 vs. 17.2 {+-} 1.8 mm; p < 0.001) and width (20.1 {+-} 2.9 vs. 12.6 {+-} 3.7 mm; p < 0.001); significantly larger volume{sub s}egmented (8.6 {+-} 3.2 vs. 3.0 {+-} 0.7 ml; p < 0.001) and volume{sub c}alculated (8.4 {+-} 3.0 ml vs. 3.3 {+-} 1.1 ml; p < 0.001); significantly lower depth-to-width (1.17 {+-} 0.10 vs. 1.48 {+-} 0.44; p < 0.05), sphericity (1.55 {+-} 0.44 vs. 1.96 {+-} 0.43; p < 0.01), and eccentricity (0.84 {+-} 0.61 vs. 1.73 {+-} 0.91; p < 0.01) ratios; and significantly greater circularity (0.62 {+-} 0.14 vs. 0.45 {+-} 0.16; p < 0.01). Renal artery embolization with small and narrowly calibrated microparticles affected the coagulation diameter, volume, and shape of RFAs in porcine kidneys. Embolized RFAs were significantly larger and more spherical compared with nonembolized RFAs.

  10. Clinical Experience with Cone Beam CT Navigation for Tumor Ablation

    PubMed Central

    Abi-Jaoudeh, Nadine; Venkatesan, Aradhana M.; Van der Sterren, William; Radaelli, Alessandro; Carelsen, Bart; Wood, Bradford J.

    2015-01-01

    Purpose To describe clinical use and potential benefits of Cone Beam Computed Tomography (CBCT) navigation to perform image guided percutaneous tumor ablations. Materials and Methods All ablations performed between February 2011 and February 2013 using CBCT navigation, were included. Sixteen patients underwent 20 ablations for 29 lesions. CBCT ablation planning capabilities include multimodality image fusion and tumor segmentation for visualization, depiction of the predicted ablation zones for intra-procedural planning and segmentation of the ablated area for immediate post-treatment verification. Number and purpose of CBCT were examined. The initial ablation plan defined as number of probes and duration of energy delivery was recorded for 20/29 lesions. Technical success and local recurrences were recorded. Primary and secondary effectiveness rates were calculated. Results Image fusion was utilized for 16 lesions and intra-procedural ultrasound for 4. Of the 20/29 lesions, where the ablation plans were recorded, there was no deviation from the plan in 14. In the remaining 6/20, iterative planning was needed for complete tumor coverage. An average of 8.7 ± 3.2 CBCT were performed per procedure, including 1.3 ± 0.5 for tumor segmentation and planning, 1.7 ± 0.7 for probe position confirmation, 3.9 ± 2 to ensure complete coverage. Mean follow-up was 18.6 ± 6.5 months. 28/29 ablations were technically successful (96.5%). Of ablations performed with curative intent, technical effectiveness at one-month was 25/26 (96.1%) and 22/26 (84.6%) at last follow-up. Local tumor progression was observed in 11.5% (3/26). Conclusion CBCT navigation may add information to assist and improve ablation guidance and monitoring. PMID:25645409

  11. Laser ablation with applied magnetic field for electric propulsion

    NASA Astrophysics Data System (ADS)

    Batishcheva, Alla; Batishchev, Oleg; Cambier, Jean-Luc

    2012-10-01

    Using ultrafast lasers with tera-watt-level power allows efficient ablation and ionization of solid-density materials [1], creating dense and hot (˜100eV) plasma. We propose ablating small droplets in the magnetic nozzle configurations similar to mini-helicon plasma source [2]. Such approach may improve the momentum coupling compared to ablation of solid surfaces and facilitate plasma detachment. Results of 2D modeling of solid wire ablation in the applied magnetic field are presented and discussed. [4pt] [1] O. Batishchev et al, Ultrafast Laser Ablation for Space Propulsion, AIAA technical paper 2008-5294, -16p, 44th JPC, Hartford, 2008.[0pt] [2] O. Batishchev and J.L. Cambier, Experimental Study of the Mini-Helicon Thruster, Air Force Research Laboratory Report, AFRL-RZ-ED-TR-2009-0020, 2009.

  12. Ablation of CsI by XUV Capillary Discharge Laser

    NASA Astrophysics Data System (ADS)

    Pira, Peter; Zelinger, Zdenek; Burian, Tomas; Vysin, Ludek; Wild, Jan; Juha, Libor; Lancok, Jan; Nevrly, Vaclav

    2015-09-01

    XUV capillary discharge laser (CDL) is suitable source for ablation of ionic crystals as material which is difficult to ablate by conventional laser. Single crystal of CsI was irradiated by 2.5 ns pulses of a 46.9 nm radiation at 2 Hz. The CDL beam was focused by Sc/Si multilayer spherical mirror. Attenuation length of CsI for this wavelength is 38 nm. Ablation rate was calculated after irradiation of 10, 20, 30, 50 and 100 pulses. Depth of the craters was measured by optical profiler (white light interferometry). Ablation threshold was determined from craters after irradiation with the changing fluence and compared with modeling by XUV-ABLATOR.

  13. Nozzle designs with pitch precursor ablatives

    NASA Technical Reports Server (NTRS)

    Blevins, H. R.; Bedard, R. J.

    1976-01-01

    Recent developments in carbon phenolic ablatives for solid rocket motor nozzles have yielded a pitch precursor carbon fiber offering significant raw material availability and cost saving advantages as compared to conventional rayon precursor material. This paper discusses the results of an experimental program conducted to assess the thermal performance and characterize the thermal properties of pitch precursor carbon phenolic ablatives. The end result of this program is the complete thermal characterization of pitch fabric, pitch mat, hybrid pitch/rayon fabric and pitch mat molding compound. With these properties determined an analytic capability now exists for predicting the thermal performance of these materials in rocket nozzle liner applications. Further planned efforts to verify material performance and analytical prediction procedures through actual rocket motor firings are also discussed.

  14. Liquid Wall Chambers

    SciTech Connect

    Meier, W R

    2011-02-24

    The key feature of liquid wall chambers is the use of a renewable liquid layer to protect chamber structures from target emissions. Two primary options have been proposed and studied: wetted wall chambers and thick liquid wall (TLW) chambers. With wetted wall designs, a thin layer of liquid shields the structural first wall from short ranged target emissions (x-rays, ions and debris) but not neutrons. Various schemes have been proposed to establish and renew the liquid layer between shots including flow-guiding porous fabrics (e.g., Osiris, HIBALL), porous rigid structures (Prometheus) and thin film flows (KOYO). The thin liquid layer can be the tritium breeding material (e.g., flibe, PbLi, or Li) or another liquid metal such as Pb. TLWs use liquid jets injected by stationary or oscillating nozzles to form a neutronically thick layer (typically with an effective thickness of {approx}50 cm) of liquid between the target and first structural wall. In addition to absorbing short ranged emissions, the thick liquid layer degrades the neutron flux and energy reaching the first wall, typically by {approx}10 x x, so that steel walls can survive for the life of the plant ({approx}30-60 yrs). The thick liquid serves as the primary coolant and tritium breeding material (most recent designs use flibe, but the earliest concepts used Li). In essence, the TLW places the fusion blanket inside the first wall instead of behind the first wall.

  15. Tumour ablation: technical aspects

    PubMed Central

    Bodner, Gerd; Bale, Reto

    2009-01-01

    Abstract Image-guided percutaneous radiofrequency ablation (RFA) is a minimally invasive, relatively low-risk procedure for tumour treatment. Local recurrence and survival rates depend on the rate of complete ablation of the entire tumour including a sufficient margin of surrounding healthy tissue. Currently a variety of different RFA devices are available. The interventionalist must be able to predict the configuration and extent of the resulting ablation necrosis. Accurate planning and execution of RFA according to the size and geometry of the tumour is essential. In order to minimize complications, individualized treatment strategies may be necessary for tumours close to vital structures. This review examines the state-of-the art of different device technologies, approaches, and treatment strategies for percutaneous RFA of liver tumours. PMID:19965296

  16. Behavior of multi-walled carbon nanotubes on the porosity and microstructure of cement-based materials

    NASA Astrophysics Data System (ADS)

    Nochaiya, Thanongsak; Chaipanich, Arnon

    2011-01-01

    The porosity and microstructure of a Portland cement-multi-walled carbon nanotube composite were investigated. Multi-walled carbon nanotubes (CNTs), up to 1 wt.% of cement, synthesized by infusion chemical vapor deposition, and Portland cement type I (PC) were used to produce pastes with a water to cement ratio of 0.5. Mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) were used to characterize Portland cement-CNTs systems. MIP analysis of the results indicates that total porosity of the mixes with CNTs was found to decrease with increasing CNTs content. Moreover, an important effect of additional CNTs was a reduction in the number of mesopores, while SEM technique showed dispersion of CNTs between the hydration phases of Portland cement pastes.

  17. The temperature dependence of ultra-cold neutron wall losses in material bottles coated with deuterated polystryene

    SciTech Connect

    Cooper, Martiin D; Bagdasarova, Yelena; Clayton, Steven M; Currie, Scott A; Griffith, William C; Ito, Takeyasu; Makela, Mark F; Morris, Cheistopher; Rahaman, Mohamad S; Ramsey, John C; Saunders, Alexander; Rios, Raymond

    2011-01-18

    Ultra-cold neutrons (UCN) from the LANSCE super-thermal deuterium source were used to fill an acrylic bottle coated with deuterated polystyrene. The bottle was constructed to minimize losses through the filling valve. The storage time was extracted from a series of measurements where the number of neutrons was counted after they were held in the bottle for durations varying from 60-1200 s. The data were collected at temperatures of 18, 40, 65, 105, and 295 K. The data has been analyzed in terms of the ratio of the imaginary to real part of the wall potential. The analysis considers the velocity dependence of the probability per bounce of wall loss. The implication of these measurements for the SNS electric dipole moment search will be presented.

  18. Shuttle subscale ablative nozzle tests

    NASA Technical Reports Server (NTRS)

    Powers, L. B.; Bailey, R. L.

    1980-01-01

    Recent subscale nozzle tests have identified new and promising carbon phenolic nozzle ablatives which utilize staple rayon, PAN, and pitch based carbon cloth. A 4-inch throat diameter submerged test nozzle designed for the 48-inch Jet Propulsion Laboratory char motor was used to evaluate five different designs incorporating 20 candidate ablatives. Test results indicate that several pitch and PAN-based carbon phenolic ablatives can provide erosion and char performance equivalent or superior to the present continuous rayon-based SRM ablative.

  19. A study of angular dependence in the ablation rate of polymers by nanosecond pulses

    NASA Astrophysics Data System (ADS)

    Pedder, James E. A.; Holmes, Andrew S.

    2006-02-01

    Measurements of ablation rate have traditionally been carried out only at normal incidence. However, in real-world applications ablation is often carried out at oblique angles, and it is useful to have prior knowledge of the ablation rate in this case. Detailed information about the angular dependence is also important for the development of ablation simulation tools, and can provide additional insight into the ablation mechanism. Previously we have reported on the angular dependence of direct-write ablation at 266 nm wavelength in solgel and polymer materials. In this paper we present a systematic study of angular dependence for excimer laser ablation of two polymer materials of interest for microfabrication: polycarbonate and SU8 photoresist. The results are used to improve simulation models to aid in mask design.

  20. Solar cell contact formation using laser ablation

    DOEpatents

    Harley, Gabriel; Smith, David D.; Cousins, Peter John

    2015-07-21

    The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline material layer; and forming conductive contacts in the plurality of contact holes.

  1. Solar cell contact formation using laser ablation

    DOEpatents

    Harley, Gabriel; Smith, David; Cousins, Peter

    2012-12-04

    The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline material layer; and forming conductive contacts in the plurality of contact holes.

  2. Thermal protection system ablation sensor

    NASA Technical Reports Server (NTRS)

    Gorbunov, Sergey (Inventor); Martinez, Edward R. (Inventor); Scott, James B. (Inventor); Oishi, Tomomi (Inventor); Fu, Johnny (Inventor); Mach, Joseph G. (Inventor); Santos, Jose B. (Inventor)

    2011-01-01

    An isotherm sensor tracks space vehicle temperatures by a thermal protection system (TPS) material during vehicle re-entry as a function of time, and surface recession through calibration, calculation, analysis and exposed surface modeling. Sensor design includes: two resistive conductors, wound around a tube, with a first end of each conductor connected to a constant current source, and second ends electrically insulated from each other by a selected material that becomes an electrically conductive char at higher temperatures to thereby complete an electrical circuit. The sensor conductors become shorter as ablation proceeds and reduced resistance in the completed electrical circuit (proportional to conductor length) is continually monitored, using measured end-to-end voltage change or current in the circuit. Thermocouple and/or piezoelectric measurements provide consistency checks on local temperatures.

  3. Amalgam ablation with the Er:YAG laser

    NASA Astrophysics Data System (ADS)

    Wigdor, Harvey A.; Visuri, Steven R.; Walsh, Joseph T., Jr.

    1995-04-01

    Any laser that will be used by dentist to replace the dental drill (handpiece) must remove dental hard tissues safely. These lasers must also have the ability to ablate the restorative dental materials which are present in the teeth being treated. Prior to any laser being used to treat humans a thorough knowledge of the effects of the laser treatment on dental materials must be understood. Cores of dental amalgam were created and sliced into thin wafers for this experiment. Ablation efficiency and thermal changes were evaluated with and without water. It appears as if the Er:YAG laser can effectively ablate amalgam dental material with and without water. The water prevents the temperature from increasing much above baseline and does not reduce efficiency of ablation.

  4. Modeling of anisotropic ablation of the concrete during Molten Core Concrete Interaction

    NASA Astrophysics Data System (ADS)

    Kang, Kyoung Min

    This work proposes a model to explain concrete anisotropic ablation by corium during a Molten Corium Concrete Interaction (MCCI). As a result of recent MCCI prototypic material experiments, CCI and VULCANO tests, one observes that concrete ablation behavior consistently depends on the concrete materials used in the experiments. Specifically, tests with Limestone-Common-Sand (LCS) concrete yielded isotropic concrete ablation; i.e., equal axial and radial concrete erosion. This is in comparison to anisotropic ablation in tests with Siliceous (SIL) concrete, where radial ablation was much larger than axial ablation. This was an unexpected result, because prior results of many MCCI simulant experiments indicated that nearly isotropic ablation was expected in prototypic material experiments regardless of concrete type. A new phenomenological model is proposed in this work based on a hypothesis that unifies the result of both previous simulant and prototypic material experiments; i.e., heat transfer area enhancement and delayed gas release caused by the presence of un-melted solid aggregate material that enters the molten pool. This model offers a logical and phenomenological explanation concerning anisotropic ablation as well as the capability to simulate anisotropic ablation. This model is implemented into the CORQUENCH code as part of this work. Comparisons of simulation results obtained with this new model to the CCI experiments for cases with siliceous concrete and anisotropic ablation show better agreement with the test data than the existing model.

  5. Wall Finishes; Carpentry: 901895.

    ERIC Educational Resources Information Center

    Dade County Public Schools, Miami, FL.

    The course outline is designed to provide instruction in selecting, preparing, and installing wall finishing materials. Prerequisites for the course include mastery of building construction plans, foundations and walls, and basic mathematics. Intended for use in grades 11 and 12, the course contains five blocks of study totaling 135 hours of…

  6. Fluidized wall for protecting fusion chamber walls

    SciTech Connect

    Maniscalco, James A.; Meier, Wayne R.

    1982-01-01

    Apparatus for protecting the inner wall of a fusion chamber from microexplosion debris, x-rays, neutrons, etc. produced by deuterium-tritium (DT) targets imploded within the fusion chamber. The apparatus utilizes a fluidized wall similar to a waterfall comprising liquid lithium or solid pellets of lithium-ceramic, the waterfall forming a blanket to prevent damage of the structural materials of the chamber.

  7. UV laser ablation patterns in intraocular lenses

    NASA Astrophysics Data System (ADS)

    Lagiou, D. P.; Evangelatos, Ch.; Apostolopoulos, A.; Spyratou, E.; Bacharis, C.; Makropoulou, M.; Serafetinides, A. A.

    2013-03-01

    The aim of this work is to investigate the effect of UV solid state laser radiation on intraocular lens (IOL) polymer surfaces as an alternative method to conventional surface shaping techniques for IOLs customization. Laser ablation experiments were performed on PMMA plates and commercially available hydrophobic and hydrophilic acrylic IOLs with the 5th harmonic of a Q-switched Nd:YAG laser (λ=213 nm). Circular arrays of holes were drilled on the polymer surface, covering the centre and the peripheries of the IOL. The morphology of the ablated IOL surface was examined with a conventional optical microscope (Leitz GMBH Wetzlar) and with a scanning electron microscope (SEM, Fei - Innova Nanoscope) at various laser parameters. Quantitative measurements of ablation rates were performed with a contact profilometer (Dektak-150), in which a mechanical stylus scanned across the surface of gold-coated IOLs (after SEM imaging) to measure variationsF in surface height. Laser interaction with IOLs depends on optical and mechanical material properties, in addition to laser radiation parameters. The exact ablation mechanism is discussed. Some polymer materials, depending on their properties, are more susceptible to the photothermal mechanism than the photochemical one or vice versa. In summary, every IOL polymer exhibits specific attributes in its interaction with the 5th harmonic of Nd:YAG laser.

  8. Measurement of Preheat and Shock Melting in Be Ablators During the First Few ns of the NIF Ignition Pulse

    SciTech Connect

    Bradley, D K; Prisbrey, S T; Page, R H; Braun, D G; Edwards, M J; Hibbard, R L; Moreno, K A; Mauldin, M P; Nikroo, A

    2008-05-28

    We have developed a scaled hohlraum platform to experimentally measure preheat in ablator materials during the first few nanoseconds of the radiation drive proposed for ignition experiments at the National Ignition Facility [J. A. Paisner, J. D. Boyes, S. A. Kumpan, et al., Laser Focus World 30, 75 (1994)]. The platform design approximates the radiation environment of the pole of the capsule by matching both the laser spot intensity and illuminated hohlraum wall fraction in scaled halfraums driven by the OMEGA laser system [T. R. Boehly, D. L. Brown, R. S. Craxton, et al., Optics Communications 133, 495 (1997)]. A VISAR reflecting from the rear surface of the sample was used to measure sample motion prior to shock breakout. The experiments show that the first {approx}20 {micro}m of a Be ablator will be melted by radiation preheat, with subsequent material melted by the initial shock, in agreement with simulations. The experiments also show no evidence of anomalous heating of buried high-z doped layers in the ablator.

  9. Therapeutic stimulation versus ablation.

    PubMed

    Hariz, Marwan I; Hariz, Gun-Marie

    2013-01-01

    The renaissance of functional stereotactic neurosurgery was pioneered in the mid 1980s by Laitinen's introduction of Leksell's posteroventral pallidotomy for Parkinson´s disease (PD). This ablative procedure experienced a worldwide spread in the 1990s, owing to its excellent effect on dyskinesias and other symptoms of post-l-dopa PD. Modern deep brain stimulation (DBS), pioneered by Benabid and Pollak in 1987 for the treatment of tremor, first became popular when it was applied to the subthalamic nucleus (STN) in the mid 1990s, where it demonstrated a striking effect on all cardinal symptoms of advanced PD, and permitted reduced dosages of medication. DBS, as a nondestructive, adaptable, and reversible procedure that is proving safe in bilateral surgery on basal ganglia, has great appeal to clinicians and patients alike, despite the fact that it is expensive, laborious, and relies on very strict patient selection criteria, especially for STN DBS. Psychiatric surgery has experienced the same phenomenon, with DBS supplanting completely stereotactic ablative procedures. This chapter discusses the pros and cons of ablation versus stimulation and investigates the reasons why DBS has overshadowed proven efficient ablative procedures such as pallidotomy for PD, and capsulotomy and cingulotomy for obsessive-compulsive disorder and depression. PMID:24112885

  10. A novel radial anode layer ion source for inner wall pipe coating and materials modification—Hydrogenated diamond-like carbon coatings from butane gas

    NASA Astrophysics Data System (ADS)

    Murmu, Peter P.; Markwitz, Andreas; Suschke, Konrad; Futter, John

    2014-08-01

    We report a new ion source development for inner wall pipe coating and materials modification. The ion source deposits coatings simultaneously in a 360° radial geometry and can be used to coat inner walls of pipelines by simply moving the ion source in the pipe. Rotating parts are not required, making the source ideal for rough environments and minimizing maintenance and replacements of parts. First results are reported for diamond-like carbon (DLC) coatings on Si and stainless steel substrates deposited using a novel 360° ion source design. The ion source operates with permanent magnets and uses a single power supply for the anode voltage and ion acceleration up to 10 kV. Butane (C4H10) gas is used to coat the inner wall of pipes with smooth and homogeneous DLC coatings with thicknesses up to 5 μm in a short time using a deposition rate of 70 ± 10 nm min-1. Rutherford backscattering spectrometry results showed that DLC coatings contain hydrogen up to 30 ± 3% indicating deposition of hydrogenated DLC (a-C:H) coatings. Coatings with good adhesion are achieved when using a multiple energy implantation regime. Raman spectroscopy results suggest slightly larger disordered DLC layers when using low ion energy, indicating higher sp3 bonds in DLC coatings. The results show that commercially interesting coatings can be achieved in short time.

  11. A volume averaged global model study of the influence of the electron energy distribution and the wall material on an oxygen discharge

    NASA Astrophysics Data System (ADS)

    Toneli, D. A.; Pessoa, R. S.; Roberto, M.; Gudmundsson, J. T.

    2015-12-01

    A low pressure high density oxygen discharge is studied through a global (volume averaged) model in the pressure range 0.5-100 mTorr. The goal of this work is to evaluate the dependence of collisional energy loss per electron-ion pair created, effective electron temperature, mean density of species, and mean electronegativity on the electron energy distribution function. Differences in the results for Maxwellian and non-Maxwellian distributions show the importance of using a proper electron energy distribution function in discharge modelling. We also explore the differences due to different reactor wall materials comparing the results for an anodized aluminium reactor with a stainless steel reactor. Due to the low recombination coefficient for oxygen atoms on the anodized aluminium walls, the yield of atomic oxygen in anodized aluminium reactors increases significantly as compared to stainless steel reactors. However, the difference of the yield of atomic oxygen in these reactors decreases as pressure increases. Thus, anodized aluminium reactors can be desired for applications where a high concentration of atomic oxygen is required. Finally, the importance of quenching coefficient for plasma modelling is stressed through the quenching coefficient at the walls for {{\\text{O}}2} ({{\\text{b}}1}Σ\\text{g}+ ). Low quenching coefficients result in high densities of {{\\text{O}}2} ({{\\text{b}}1}Σ\\text{g}+ ) affecting the mean electronegativity of the plasma due to the decrease in the density of \\text{O}2- .

  12. A novel radial anode layer ion source for inner wall pipe coating and materials modification--hydrogenated diamond-like carbon coatings from butane gas.

    PubMed

    Murmu, Peter P; Markwitz, Andreas; Suschke, Konrad; Futter, John

    2014-08-01

    We report a new ion source development for inner wall pipe coating and materials modification. The ion source deposits coatings simultaneously in a 360° radial geometry and can be used to coat inner walls of pipelines by simply moving the ion source in the pipe. Rotating parts are not required, making the source ideal for rough environments and minimizing maintenance and replacements of parts. First results are reported for diamond-like carbon (DLC) coatings on Si and stainless steel substrates deposited using a novel 360° ion source design. The ion source operates with permanent magnets and uses a single power supply for the anode voltage and ion acceleration up to 10 kV. Butane (C4H10) gas is used to coat the inner wall of pipes with smooth and homogeneous DLC coatings with thicknesses up to 5 μm in a short time using a deposition rate of 70 ± 10 nm min(-1). Rutherford backscattering spectrometry results showed that DLC coatings contain hydrogen up to 30 ± 3% indicating deposition of hydrogenated DLC (a-C:H) coatings. Coatings with good adhesion are achieved when using a multiple energy implantation regime. Raman spectroscopy results suggest slightly larger disordered DLC layers when using low ion energy, indicating higher sp(3) bonds in DLC coatings. The results show that commercially interesting coatings can be achieved in short time. PMID:25173323

  13. New Ablation Technologies and Techniques

    PubMed Central

    Berte, Benjamin; Yamashita, Seigo; Derval, Nicolas; Denis, Arnaud; Shah, Ashok; Amraoui, Sana; Hocini, Meleze; Haissaguerre, Michel; Jais, Pierre; Sacher, Frederic

    2014-01-01

    Catheter ablation is an established treatment strategy for a range of different cardiac arrhythmias. Over the past decade two major areas of expansion have been ablation of atrial fibrillation (AF) and ventricular tachycardia (VT) in the context of structurally abnormal hearts. In parallel with the expanding role of catheter ablation for AF and VT, multiple novel technologies have been developed which aim to increase safety and procedural success. Areas of development include novel catheter designs, novel navigation technologies and higher resolution imaging techniques. The aim of the present review is to provide an overview of novel developments in AF ablation and VT ablation in patients with of structural cardiac diseases. PMID:26835075

  14. New Ablation Technologies and Techniques.

    PubMed

    Mahida, Saagar; Berte, Benjamin; Yamashita, Seigo; Derval, Nicolas; Denis, Arnaud; Shah, Ashok; Amraoui, Sana; Hocini, Meleze; Haissaguerre, Michel; Jais, Pierre; Sacher, Frederic

    2014-08-01

    Catheter ablation is an established treatment strategy for a range of different cardiac arrhythmias. Over the past decade two major areas of expansion have been ablation of atrial fibrillation (AF) and ventricular tachycardia (VT) in the context of structurally abnormal hearts. In parallel with the expanding role of catheter ablation for AF and VT, multiple novel technologies have been developed which aim to increase safety and procedural success. Areas of development include novel catheter designs, novel navigation technologies and higher resolution imaging techniques. The aim of the present review is to provide an overview of novel developments in AF ablation and VT ablation in patients with of structural cardiac diseases. PMID:26835075

  15. An experimental investigation of the damping contribution of an elastomeric ablator on aluminum beams

    NASA Technical Reports Server (NTRS)

    Howell, W. E.

    1974-01-01

    Damping results are presented for an elastometric ablation material bonded to an aluminum alloy substrate. Tests were conducted on aluminum beams 0.159, 0.318, and 0.476 cm thick, and with and without an ablator. Ablation-material thickness varied from 0.159 to 0.953 cm. Comparative damping data were obtained by using variations of the free-free beam technique with strain gages and piezoelectric transducers. Of the two test arrangements employed, the technique using strain gages produced results that indicated less restraint of the beams. Ablation material, in thicknesses less than 1 cm, substantially increased the damping parameter of the aluminum beams.

  16. Ion extraction from positively biased laser-ablation plasma

    NASA Astrophysics Data System (ADS)

    Isono, Fumika; Nakajima, Mitsuo; Hasegawa, Jun; Horioka, Kazuhiko

    2016-07-01

    Ions were extracted through a grounded grid from a positively biased laser-ablation plasma and the behaviors were investigated. Since the plasma was positively biased against the grounded wall, we could extract the ions without insulated gap. We confirmed formation of a virtual anode when we increased the distance between the grid and the ion collector. Results also indicated that when the ion flux from the ablation plasma exceeded a critical value, the current was strongly suppressed to the space charge limited level due to the formation of virtual anode.

  17. Percutaneous Ablation of Adrenal Tumors

    PubMed Central

    Venkatesan, Aradhana M.; Locklin, Julia; Dupuy, Damian E.; Wood, Bradford J.

    2010-01-01

    Adrenal tumors comprise a broad spectrum of benign and malignant neoplasms, and include functional adrenal adenomas, pheochromocytomas, primary adrenocortical carcinoma and adrenal metastases. Percutaneous ablative approaches that have been described and used in the treatment of adrenal tumors include percutaneous radiofrequency ablation (RFA), cryoablation, microwave ablation and chemical ablation. Local tumor ablation in the adrenal gland presents unique challenges, secondary to the adrenal gland’s unique anatomic and physiologic features. The results of clinical series employing percutaneous ablative techniques in the treatment of adrenal tumors are reviewed in this article. Clinical and technical considerations unique to ablation in the adrenal gland are presented, including approaches commonly used in our practices, and risks and potential complications are discussed. PMID:20540918

  18. Overview of the CHarring Ablator Response (CHAR) Code

    NASA Technical Reports Server (NTRS)

    Amar, Adam J.; Oliver, A. Brandon; Kirk, Benjamin S.; Salazar, Giovanni; Droba, Justin

    2016-01-01

    An overview of the capabilities of the CHarring Ablator Response (CHAR) code is presented. CHAR is a one-, two-, and three-dimensional unstructured continuous Galerkin finite-element heat conduction and ablation solver with both direct and inverse modes. Additionally, CHAR includes a coupled linear thermoelastic solver for determination of internal stresses induced from the temperature field and surface loading. Background on the development process, governing equations, material models, discretization techniques, and numerical methods is provided. Special focus is put on the available boundary conditions including thermochemical ablation, surface-to-surface radiation exchange, and flowfield coupling. Finally, a discussion of ongoing development efforts is presented.

  19. Overview of the CHarring Ablator Response (CHAR) Code

    NASA Technical Reports Server (NTRS)

    Amar, Adam J.; Oliver, A. Brandon; Kirk, Benjamin S.; Salazar, Giovanni; Droba, Justin

    2016-01-01

    An overview of the capabilities of the CHarring Ablator Response (CHAR) code is presented. CHAR is a one-, two-, and three-dimensional unstructured continuous Galerkin finite-element heat conduction and ablation solver with both direct and inverse modes. Additionally, CHAR includes a coupled linear thermoelastic solver for determination of internal stresses induced from the temperature field and surface loading. Background on the development process, governing equations, material models, discretization techniques, and numerical methods is provided. Special focus is put on the available boundary conditions including thermochemical ablation and contact interfaces, and example simulations are included. Finally, a discussion of ongoing development efforts is presented.

  20. Ablation of film stacks in solar cell fabrication processes

    SciTech Connect

    Harley, Gabriel; Kim, Taeseok; Cousins, Peter John

    2013-04-02

    A dielectric film stack of a solar cell is ablated using a laser. The dielectric film stack includes a layer that is absorptive in a wavelength of operation of the laser source. The laser source, which fires laser pulses at a pulse repetition rate, is configured to ablate the film stack to expose an underlying layer of material. The laser source may be configured to fire a burst of two laser pulses or a single temporally asymmetric laser pulse within a single pulse repetition to achieve complete ablation in a single step.

  1. Solar cell contact formation using laser ablation

    DOEpatents

    Harley, Gabriel; Smith, David D.; Cousins, Peter John

    2014-07-22

    The formation of solar cell contacts using a laser is described. A method of fabricating a back-contact solar cell includes forming a poly-crystalline material layer above a single-crystalline substrate. The method also includes forming a dielectric material stack above the poly-crystalline material layer. The method also includes forming, by laser ablation, a plurality of contacts holes in the dielectric material stack, each of the contact holes exposing a portion of the poly-crystalline materiat layer; and forming conductive contacts in the plurality of contact holes.

  2. Guiding and Ionization Blueshift in Ablative Capillary Waveguide Accelerators

    SciTech Connect

    McGuffey, Chris; Matsuoka, Takeshi; Bulanov, Stepan; Chvykov, Vladimir; Kalintchenko, Galina; Rousseau, Pascal; Yanovsky, Victor; Maksimchuk, Anatoly; Krushelnick, Karl; Levin, Michael; Zigler, Arie

    2009-01-22

    Laser wakefield acceleration (LWFA) in plasmas has been demonstrated with gradients which are orders of magnitude greater than the limit on conventional Radio Frequency accelerators. However, the acceleration length is limited by two factors, the dephasing length and the Rayleigh range of the laser pulse. Dephasing length is the distance in which electrons overtake the laser pulse and can be increased by decreasing plasma density. Alternatively the interaction length can be extended by orders of magnitude by using ablative wall discharge capillary targets, in which a plasma is preformed with a transverse density profile capable of guiding the focused laser. We have demonstrated guiding of high intensity laser pulses from the HERCULES laser over 3 cm for powers up to 35 TW. The quality of the laser spot can be retained and the intensity remains high even at the exit of the capillary. The transmitted laser spectrum shows blueshifting due to field ionization by the laser pulse. This ionization might enhance electron injection at low electron density for LWFA GeV accelerators. The field ionization affects carbon atoms and ions from the ablated capillary, which are not present in hydrogen-filled capillaries. This creates an additional challenge to guiding compared to hydrogen-filled capillaries. However, the setup and materials are easier to come by. The use of these capillary targets may also be of interest to other high intensity laser-plasma interactions requiring long interaction lengths such as high harmonic generation from gases and plasmas, or x-ray lasing in underdense plasmas.

  3. Optimization of the generator settings for endobiliary radiofrequency ablation

    PubMed Central

    Barret, Maximilien; Leblanc, Sarah; Vienne, Ariane; Rouquette, Alexandre; Beuvon, Frederic; Chaussade, Stanislas; Prat, Frederic

    2015-01-01

    AIM: To determine the optimal generator settings for endobiliary radiofrequency ablation. METHODS: Endobiliary radiofrequency ablation was performed in live swine on the ampulla of Vater, the common bile duct and in the hepatic parenchyma. Radiofrequency ablation time, “effect”, and power were allowed to vary. The animals were sacrificed two hours after the procedure. Histopathological assessment of the depth of the thermal lesions was performed. RESULTS: Twenty-five radiofrequency bursts were applied in three swine. In the ampulla of Vater (n = 3), necrosis of the duodenal wall was observed starting with an effect set at 8, power output set at 10 W, and a 30 s shot duration, whereas superficial mucosal damage of up to 350 μm in depth was recorded for an effect set at 8, power output set at 6 W and a 30 s shot duration. In the common bile duct (n = 4), a 1070 μm, safe and efficient ablation was obtained for an effect set at 8, a power output of 8 W, and an ablation time of 30 s. Within the hepatic parenchyma (n = 18), the depth of tissue damage varied from 1620 μm (effect = 8, power = 10 W, ablation time = 15 s) to 4480 μm (effect = 8, power = 8 W, ablation time = 90 s). CONCLUSION: The duration of the catheter application appeared to be the most important parameter influencing the depth of the thermal injury during endobiliary radiofrequency ablation. In healthy swine, the currently recommended settings of the generator may induce severe, supratherapeutic tissue damage in the biliary tree, especially in the high-risk area of the ampulla of Vater. PMID:26566429

  4. Temperature profiles of 980- and 1,470-nm endovenous laser ablation, endovenous radiofrequency ablation and endovenous steam ablation.

    PubMed

    Malskat, W S J; Stokbroekx, M A L; van der Geld, C W M; Nijsten, T E C; van den Bos, R R

    2014-03-01

    Endovenous thermal ablation (EVTA) techniques are very effective for the treatment of varicose veins, but their exact working mechanism is still not well documented. The lack of knowledge of mechanistic properties has led to a variety of EVTA protocols and a commercially driven dissemination of new or modified techniques without robust scientific evidence. The aim of this study is to compare temperature profiles of 980-and 1,470-nm endovenous laser ablation (EVLA), segmental radiofrequency ablation (RFA), and endovenous steam ablation (EVSA). In an experimental setting, temperature measurements were performed using thermocouples; raw potato was used to mimic a vein wall. Two laser wavelengths (980 and 1,470 nm) were used with tulip-tip fibers and 1,470 nm also with a radial-emitting fiber. Different powers and pullback speeds were used to achieve fluences of 30, 60, and 90 J/cm. For segmental RFA, 1 cycle of 20 s was analyzed. EVSA was performed with two and three pulses of steam per centimeter. Maximum temperature increase, time span of relevant temperature increase, and area under the curve of the time of relevant temperature increase were measured. In all EVLA settings, temperatures increased and decreased rapidly. High fluence is associated with significantly higher temperatures and increased time span of temperature rise. Temperature profiles of 980- and 1,470-nm EVLA with tulip-tip fibers did not differ significantly. Radial EVLA showed significantly higher maximum temperatures than tulip-tip EVLA. EVSA resulted in mild peak temperatures for longer durations than EVLA. Maximum temperatures with three pulses per centimeter were significantly higher than with two pulses. RFA temperature rises were relatively mild, resulting in a plateau-shaped temperature profile, similar to EVSA. Temperature increase during EVLA is fast with a high-peak temperature for a short time, where EVSA and RFA have longer plateau phases and lower maximum temperatures. PMID

  5. Onoufrios, the famous XVI's century iconographer, creator of the ``Berati School'': studying the technique and materials used in wall paintings of inscribed churches

    NASA Astrophysics Data System (ADS)

    Pavlidou, E.; Arapi, M.; Zorba, T.; Anastasiou, M.; Civici, N.; Stamati, F.; Paraskevopoulos, K. M.

    2006-06-01

    The study of the materials and techniques employed for wall painting, complementing the information from historical and aesthetic data, contributes to the integrated knowledge of the iconographer and his period. In the 16th century, regarding the iconography in the former Byzantine area, besides the School of Crete and Francos Catelanos and his school, a third artistic personality who also created his own school, Onoufrios, appeared in central Albania and expanded his activity as a painter to northern Greece as well as nearby areas, such as Ohrid. Inscriptions documenting the works of Onoufrios are found in some of the churches that he decorated with wall paintings: “St. Apostles” (1547) Kastoria Greece, “St. Nicolas” Shelcan Albania, “St. Paraskevi” (1554), Valsh Albania, while are attributed to him the church of “St. Theodores” in Berati, Albania (before 1547) and others. He is one of the best icon painters of the whole Balkan region, and the best painter that has ever worked in Albanian territory. Onoufrios managed to combine the local painting tradition with the best tradition of the eastern (Paleologian) and western (Italian) schools, resulting in a realistic and natural depiction. He is the creator of the “Berati School” that expanded to other parts of the peninsula. His individual character can be distinguished in the work of his students: his son Nikolaos (who inherited his style in painting), Onoufrios from Cyprus, etc. Based on careful observations, we extracted number of paint samples from wall paintings of three of the above mentioned churches. Ground and paint layers were examined using micro-FTIR, Optical Microscopy, TXRF and SEM-EDS, to characterize materials and methods used by the artist to create these works. Our findings in each church are discussed and compared with the others in order to understand how and with what material and resources the painter worked and how he developed his technique. The presence of calcium

  6. Accumulated lipids rather than the rigid cell walls impede the extraction of genetic materials for effective colony PCRs in Chlorella vulgaris

    PubMed Central

    2013-01-01

    Background Failure of colony PCRs in green microalga Chlorella vulgaris is typically attributed to the difficulty in disrupting its notoriously rigid cell walls for releasing the genetic materials and therefore the development of an effective colony PCR procedure in C. vulgaris presents a challenge. Results Here we identified that colony PCR results were significantly affected by the accumulated lipids rather than the rigid cell walls of C. vulgaris. The higher lipids accumulated in C. vulgaris negatively affects the effective amplification by DNA polymerase. Based on these findings, we established a simple and extremely effective colony PCR procedure in C. vulgaris. By simply pipetting/votexing the pellets of C. vulgaris in 10 ul of either TE (10 mM Tris/1 mM EDTA) or 0.2% SDS buffer at room temperature, followed by the addition of 10 ul of either hexane or Phenol:Chloroform:Isoamyl Alcohol in the same PCR tube for extraction. The resulting aqueous phase was readily PCR-amplified as genomic DNA templates as demonstrated by successful amplification of the nuclear 18S rRNA and the chloroplast rbcL gene. This colony PCR protocol is effective and robust in C. vulgaris and also demonstrates its effectiveness in other Chlorella species. Conclusions The accumulated lipids rather than the rigid cell walls of C. vulgaris significantly impede the extraction of genetic materials and subsequently the effective colony PCRs. The finding has the potential to aid the isolation of high-quality total RNAs and mRNAs for transcriptomic studies in addition to the genomic DNA isolation in Chlorella. PMID:24219401

  7. Comparison of Combination Therapies in the Management of Hepatocellular Carcinoma: Transarterial Chemoembolization with Radiofrequency Ablation versus Microwave Ablation

    PubMed Central

    Ginsburg, Michael; Zivin, Sean P.; Wroblewski, Kristen; Doshi, Taral; Vasnani, Raj J.; Van Ha, Thuong G.

    2015-01-01

    Purpose To compare retrospectively the outcomes and complications of transcatheter arterial chemoembolization with drug-eluting embolic agents combined with radiofrequency (RF) ablation or microwave (MW) ablation in treatment of hepatocellular carcinoma (HCC). Materials and Methods From 2003–2011, 89 patients with HCC received a combination therapy—transcatheter arterial chemoembolization plus RF ablation in 38 patients and transcatheter arterial chemoembolization plus MW ablation in 51 patients. Local tumor response, tumor progression-free survival (PFS), overall PFS, overall survival (OS), and complications were compared. Overall PFS and OS were compared between the two treatment groups in multivariate analysis controlling for Child-Pugh class, Barcelona Clinic Liver Classification stage, and index tumor size. Results Complete local tumor response was achieved in 37 (80.4%) of the tumors treated with transcatheter arterial chemoembolization plus RF ablation and 49 (76.6%) of the tumors treated with transcatheter arterial chemoembolization plus MW ablation (P = .67). The median tumor PFS and overall PFS were 20.8 months and 9.3 months (P = .72) for transarterial chemoembolization plus RF ablation and 21.8 months and 9.2 months for transarterial chemoembolization plus MW ablation (P = .32). The median OS of the transcatheter arterial chemoembolization plus RF ablation group was 23.3 months, and the median OS of the transcatheter arterial chemoembolization plus MW ablation group was 42.6 months, with no significant difference in the survival experience between the two groups (log-rank test, P = .10). In the multivariate analysis, Barcelona Clinic Liver Classification stage was the only factor associated with overall PFS and OS. One patient in the transcatheter arterial chemoembolization plus RF ablation cohort (3%) and two patients in the transcatheter arterial chemoembolization plus MW ablation cohort (4%) required prolonged hospitalization (< 48 h) for pain

  8. Micropillar fabrication on bovine cortical bone by direct-write femtosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Lim, Yong C.; Altman, Katrina J.; Farson, Dave F.; Flores, Katharine M.

    2009-11-01

    We investigated fabrication of cylindrical micropillars on bovine cortical bone using direct-write femtosecond laser ablation. The ablation threshold of the material was measured by single-pulse ablation tests, and the incubation coefficient was measured from linear scanned ablation tests. A motion system was programmed to apply multiple layers of concentric rings of pulses to machine pillars of various diameters and heights. The diameter of the top surface of the pillar was found to steadily decrease due to incubation of damage from successive layers of pulses during the machining process. Pillar top diameter was predicted based on a paraxial beam fluence approximation and single-pulse ablation threshold and incubation coefficient measurements. Pillar diameters predicted as successive layers of pulses were applied were well-matched to experiments, confirming that femtosecond laser ablation of the cortical bone was well-modeled by single-pulse ablation threshold measurements and an incubation coefficient.

  9. Laser ablation in a liquid-confined environment using a nanosecond laser pulse

    NASA Astrophysics Data System (ADS)

    Kang, Hyun Wook; Lee, Ho; Welch, Ashley J.

    2008-04-01

    Laser ablation of aluminum metal with 1ns, 800nm pulse at low radiant exposures was investigated in air (dry) and water (wet) environments. Compared to dry ablation, an approximately eight times increase in material removal rate was associated with wet ablation. Based on optical reflectance and scanning electron microscope images, bubble formation/collapse was responsible for augmented acoustic pressure and ablation performance. Numerically simulated temperature distributions during wet ablation were consistent with the occurrence of explosive water vaporization near the critical temperature of water. Strong pressure emission during liquid vaporization and jet formation can account for enhanced ablation process. Radial expansion of bubbles minimized the redeposition of debris, leading to improvements in energy coupling to the target and ablation performance.

  10. Percutaneous Radiofrequency Ablation of Hepatocellular Carcinomas Adjacent to the Gallbladder with Internally Cooled Electrodes: Assessment of Safety and Therapeutic Efficacy

    PubMed Central

    Kim, Sang Won; Park, Mihyun; Kim, Heejung; Kim, Young-sun; Choi, Dongil; Lim, Hyo K.

    2009-01-01

    Objective The objective of this study was to evaluate the safety and therapeutic efficacy of percutaneous radiofrequency (RF) ablation for the treatment of hepatocellular carcinomas (HCCs) adjacent to the gallbladder with the use of internally cooled electrodes. Materials and Methods We retrospectively assessed 45 patients with 46 HCCs (mean size, 2.2 cm) adjacent to the gallbladder (≤1.0 cm) treated with RF ablation using an internally cooled electrode system. An electrode was inserted into the tumor either parallel (n = 38) or perpendicular (n = 8) to the gallbladder wall. The safety and therapeutic efficacy of the procedures were assessed with clinical and imaging follow-up examinations. Follow-up with the use of CT ranged from four to 45 months (mean, 19 months). The association between variables (electrode direction, electrode type, tumor size, tumor location, lobar location) and the presence of a residual tumor or local tumor progression was also analyzed. Results There were no major complications and minor complications were noted in three patients (7%) including one case of vasovagal syncope and two cases of bilomas. Wall thickening of the gallbladder adjacent to the RF ablation zone was noted in 14 patients (41%) as determined on immediate follow-up CT imaging. Wall thickening showed complete disappearance on subsequent follow-up CT imaging. The primary technique effectiveness rate was 96% (44/46) based on one-month follow-up CT imaging. Local tumor progression was noted in six (14%) of 44 completely ablated tumors during the follow-up period. The direction of electrode insertion (perpendicular), tumor size (≥3 cm) and tumor location (a tumor that abutted the gallbladder) were associated with an increased risk of early incomplete treatment. No variable was significantly associated with local tumor progression. Conclusion Percutaneous RF ablation of HCCs adjacent to the gallbladder using an internally cooled electrode is a safe and effective treatment

  11. Modeling of nanosecond-laser ablation: calculations based on a nonstationary averaging technique (spatial moments)

    NASA Astrophysics Data System (ADS)

    Arnold, N. D.; Luk'yanchuk, Boris S.; Bityurin, Nikita M.; Baeuerle, D.

    1998-09-01

    Semi-analytical approach to a quantitative analysis of thermal ns laser ablation is presented. It permits one to take into account: (1) Arbitrary temperature dependences of material parameters, such as the specific heat, thermal conductivity, absorptivity, absorption coefficient, etc. (2) Arbitrary temporal profiles of the laser pulse. (3) Strong (Arrhenius- type) dependence of the ablation velocity on the temperature of the ablation front, which leads to a non-steady movement of the ablation boundary during the (single) pulse. (4) Screening of the incoming radiation by the ablated products. (5) Influence of the ablation (vaporization) enthalpy on the heating process. (6) Influence of melting and/or other phase transformations. The nonlinear heat conduction equation is reduced to three ordinary differential equations which describe the evolution of the surface temperature, spatial width of the enthalpy distribution, and the ablated depth. Due to its speed and flexibility, the method provides powerful tool for the fast analysis of the experimental data. The influence of different factors onto ablation curves (ablated depth h vs. fluence (phi) ) is studied. Analytical formulas for (phi) th and h((phi) ) dependences are derived and discussed. The ablation curves reveal three regions of fluence: Arrhenius region, linear region, and screening region. Threshold fluence (phi) th and Arrhenius tails at (phi) less than (phi) th, are affected heavily by the temperature dependences in material parameters, surface evaporation rate, and pulse duration and shape. In contrast, the slope of the ablation curves at (phi) greater than (phi) th, is determined almost exclusively by the latent heat of vaporization, high temperature dependence of absorptivity, and, in the case of screening, by the absorption coefficient of the plume (alpha) g. In the screening region ablated depth increases logarithmically with fluence and its qualitative behavior is weakly affected by the temperature

  12. Pulsed Nd:YAG laser selective ablation of surface enamel caries: I. Photoacoustic response and FTIR spectroscopy

    NASA Astrophysics Data System (ADS)

    Harris, David M.; Fried, Daniel

    2000-03-01

    Enamel caries lesions on extracted teeth were ablated with a pulsed Nd:YAG or Er:YAG laser. Tissue ablation was accompanied by a 'popping' sound (the photoacoustic response). Analysis of the photoacoustic response yields insights into the laser/tissue interactions. Fourier Transform Infrared (FTIR) Spectroscopy of lesions before ablation show a strong protein component associated with organic material (i.e., bacteria). Following ablation this protein component is absent.

  13. Femtosecond laser ablation of bovine cortical bone

    NASA Astrophysics Data System (ADS)

    Cangueiro, Liliana T.; Vilar, Rui; Botelho do Rego, Ana M.; Muralha, Vania S. F.

    2012-12-01

    We study the surface topographical, structural, and compositional modifications induced in bovine cortical bone by femtosecond laser ablation. The tests are performed in air, with a Yb:KYW chirped-pulse-regenerative amplification laser system (500 fs, 1030 nm) at fluences ranging from 0.55 to 2.24 J/cm2. The ablation process is monitored by acoustic emission measurements. The topography of the laser-treated surfaces is studied by scanning electron microscopy, and their constitution is characterized by glancing incidence x-ray diffraction, x-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and micro-Raman spectroscopy. The results show that femtosecond laser ablation allows removing bone without melting, carbonization, or cracking. The structure and composition of the remaining tissue are essentially preserved, the only constitutional changes observed being a reduction of the organic material content and a partial recrystallization of hydroxyapatite in the most superficial region of samples. The results suggest that, within this fluence range, ablation occurs by a combination of thermal and electrostatic mechanisms, with the first type of mechanism predominating at lower fluences. The associated thermal effects explain the constitutional changes observed. We show that femtosecond lasers are a promising tool for delicate orthopaedic surgeries, where small amounts of bone must be cut with negligible damage, thus minimizing surgical trauma.

  14. Laboratory Micrometeroid/Dust Ablation Studies

    NASA Astrophysics Data System (ADS)

    Thomas, E.; Horanyi, M.; Janches, D.; Munsat, T. L.; Plane, J. M. C.; Simolka, J.; Sternovsky, Z.

    2014-12-01

    Each day, somewhere between 5-270 tonnes of meteoric material ablates in Earth's upper atmosphere. Thisenormous range is significant because the Interplanetary Dust Particle (IDP) input has implications in ourunderstanding of meteor transport in the atmosphere, the formation of layers of metal atoms and ions,nucleation of noctilucent clouds, effects on stratospheric aerosols and O3 chemistry, and dust evolution inour solar system. As the dust ablates, it produces light, as well as a plasma trail of ionized atmosphericatoms and electrons. These meteor signatures are detected by photographic means, or by radar, but thereremain uncertainties in the luminous efficiency and ionization coefficient of meteors - two parameters thatare essential to evaluate densities, masses, height distributions and fluxes. Precise measurements of theseparameters would allow for not only an understanding of the layers of metal atoms and ions and meteoricsmoke particles in the mesosphere and lower thermosphere, but also would allow for the Earth's atmosphereto be used as a dust detector to detect and characterize the dust environment in our solar system. This work discusses the preliminary results of the new dust ablation facility at the 3 MV hypervelocity dust accelerator at the Institute for Modeling Plasma, Atmospheres and Cosmic Dust (IMPACT) at the University of Colorado, which aims to characterize the ionization coefficient and luminous efficiency of ablating micrometeroids.

  15. Diffraction modelling of laser ablation using transmission masks

    NASA Astrophysics Data System (ADS)

    Dyer, P. E.; Mackay, J.; Walton, C. D.

    2004-10-01

    We present an analysis of near-field diffraction effects in ablation with transmission masks, based on coupling a simplified form of the Fresnel-Kirchhoff diffraction integral with basic models for material removal. Modelling for square, hexagonal and circular proximity masks is described and compared with previously reported experiments on glass, silicon and polyimide using excimer, femtosecond and CO2 lasers. The model has general applicability and can provide useful insight into the effect of near-field diffraction in ablation patterning.

  16. Kinetic investigation of the oxidation of naval excess hazardous materials in supercritical water for the design of a transpiration-wall reactor

    SciTech Connect

    Rice, S.F.; Hanush, R.G.; Hunter, T.B.

    1997-01-01

    Experiments were conducted in Sandia`s supercritical fluids reactor (SFR) to generate data for the design of a transpiration-wall supercritical water oxidation (SCWO) reactor. The reactor is intended for the disposal of hazardous material generated on naval vessels. The design parameters for the system require an accurate knowledge of destruction efficiency vs. time and temperature. Three candidate materials were selected for testing. The experiments consisted of oxidizing these materials in the SFR at isothermal conditions over the temperature range of 400-550C at 24.1 MPa. A small extrapolation of the results shows that these materials can be adequately destroyed (to 99.9% destruction removal efficiency, DRE, based on total organic carbon (TOC) in the effluent) in approximately 5 seconds at 600C. The results vary smoothly and predictably with temperature such that extrapolation to higher temperatures beyond the experimental capabilities of the SFR can be made with reasonable confidence. The preliminary design of the transpiration-wall reactor has a rapid heat-up section within the reactor vessel that requires the addition of a fuel capable of quickly reacting with oxygen at temperatures below 500C. Candidate alcohols and JP-5 jet fuel were evaluated in this context. Oxidation rates for the alcohols were examined using in situ Raman spectroscopy. In addition, the potential utility of supplying the oxidizer line with hydrogen peroxide as an additive to enhance rapid initiation of the feed at unusually low temperatures was investigated. Experiments were conducted in the Supercritical Constant Volume Reactor (SCVR) using hydrogen peroxide as the initial oxidizing species. The results show that this concept as a method of enhancing low temperature reactivity appears to fail because thermal decomposition of the hydrogen peroxide is more rapid than the fuel oxidation rate at low temperatures. 8 refs., 16 figs., 5 tabs.

  17. 3D Multifunctional Ablative Thermal Protection System

    NASA Technical Reports Server (NTRS)

    Feldman, Jay; Venkatapathy, Ethiraj; Wilkinson, Curt; Mercer, Ken

    2015-01-01

    NASA is developing the Orion spacecraft to carry astronauts farther into the solar system than ever before, with human exploration of Mars as its ultimate goal. One of the technologies required to enable this advanced, Apollo-shaped capsule is a 3-dimensional quartz fiber composite for the vehicle's compression pad. During its mission, the compression pad serves first as a structural component and later as an ablative heat shield, partially consumed on Earth re-entry. This presentation will summarize the development of a new 3D quartz cyanate ester composite material, 3-Dimensional Multifunctional Ablative Thermal Protection System (3D-MAT), designed to meet the mission requirements for the Orion compression pad. Manufacturing development, aerothermal (arc-jet) testing, structural performance, and the overall status of material development for the 2018 EM-1 flight test will be discussed.

  18. Mathematical Modeling of Radiofrequency Ablation for Varicose Veins

    PubMed Central

    Choi, Sun Young; Kwak, Byung Kook

    2014-01-01

    We present a three-dimensional mathematical model for the study of radiofrequency ablation (RFA) with blood flow for varicose vein. The model designed to analyze temperature distribution heated by radiofrequency energy and cooled by blood flow includes a cylindrically symmetric blood vessel with a homogeneous vein wall. The simulated blood velocity conditions are U = 0, 1, 2.5, 5, 10, 20, and 40 mm/s. The lower the blood velocity, the higher the temperature in the vein wall and the greater the tissue damage. The region that is influenced by temperature in the case of the stagnant flow occupies approximately 28.5% of the whole geometry, while the region that is influenced by temperature in the case of continuously moving electrode against the flow direction is about 50%. The generated RF energy induces a temperature rise of the blood in the lumen and leads to an occlusion of the blood vessel. The result of the study demonstrated that higher blood velocity led to smaller thermal region and lower ablation efficiency. Since the peak temperature along the venous wall depends on the blood velocity and pullback velocity, the temperature distribution in the model influences ablation efficiency. The vein wall absorbs more energy in the low pullback velocity than in the high one. PMID:25587351

  19. Assessment of tbe Performance of Ablative Insulators Under Realistic Solid Rocket Motor Operating Conditions (a Doctoral Dissertation)

    NASA Technical Reports Server (NTRS)

    Martin, Heath Thomas

    2013-01-01

    Ablative insulators are used in the interior surfaces of solid rocket motors to prevent the mechanical structure of the rocket from failing due to intense heating by the high-temperature solid-propellant combustion products. The complexity of the ablation process underscores the need for ablative material response data procured from a realistic solid rocket motor environment, where all of the potential contributions to material degradation are present and in their appropriate proportions. For this purpose, the present study examines ablative material behavior in a laboratory-scale solid rocket motor. The test apparatus includes a planar, two-dimensional flow channel in which flat ablative material samples are installed downstream of an aluminized solid propellant grain and imaged via real-time X-ray radiography. In this way, the in-situ transient thermal response of an ablator to all of the thermal, chemical, and mechanical erosion mechanisms present in a solid rocket environment can be observed and recorded. The ablative material is instrumented with multiple micro-thermocouples, so that in-depth temperature histories are known. Both total heat flux and thermal radiation flux gauges have been designed, fabricated, and tested to characterize the thermal environment to which the ablative material samples are exposed. These tests not only allow different ablative materials to be compared in a realistic solid rocket motor environment but also improve the understanding of the mechanisms that influence the erosion behavior of a given ablative material.

  20. Laser ablation for the synthesis of carbon nanotubes

    DOEpatents

    Holloway, Brian C.; Eklund, Peter C.; Smith, Michael W.; Jordan, Kevin C.; Shinn, Michelle

    2010-04-06

    Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces an output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

  1. Laser ablation for the synthesis of carbon nanotubes

    SciTech Connect

    Holloway, Brian C; Eklund, Peter C; Smith, Michael W; Jordan, Kevin C; Shinn, Michelle

    2012-11-27

    Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces and output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

  2. Laser ablation for the synthesis of carbon nanotubes

    NASA Technical Reports Server (NTRS)

    Holloway, Brian C. (Inventor); Eklund, Peter C. (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Shinn, Michelle (Inventor)

    2012-01-01

    Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces and output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

  3. Laser ablation for the synthesis of carbon nanotubes

    NASA Technical Reports Server (NTRS)

    Holloway, Brian C. (Inventor); Eklund, Peter C. (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Shinn, Michelle (Inventor)

    2010-01-01

    Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces an output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of side pumped, preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

  4. Numerical investigation on target implosions driven by radiation ablation and shock compression in dynamic hohlraums

    SciTech Connect

    Xiao, Delong; Sun, Shunkai; Zhao, Yingkui; Ding, Ning; Wu, Jiming; Dai, Zihuan; Yin, Li; Zhang, Yang; Xue, Chuang

    2015-05-15

    In a dynamic hohlraum driven inertial confinement fusion (ICF) configuration, the target may experience two different kinds of implosions. One is driven by hohlraum radiation ablation, which is approximately symmetric at the equator and poles. The second is caused by the radiating shock produced in Z-pinch dynamic hohlraums, only taking place at the equator. To gain a symmetrical target implosion driven by radiation ablation and avoid asymmetric shock compression is a crucial issue in driving ICF using dynamic hohlraums. It is known that when the target is heated by hohlraum radiation, the ablated plasma will expand outward. The pressure in the shocked converter plasma qualitatively varies linearly with the material temperature. However, the ablation pressure in the ablated plasma varies with 3.5 power of the hohlraum radiation temperature. Therefore, as the hohlraum temperature increases, the ablation pressure will eventually exceed the shock pressure, and the expansion of the ablated plasma will obviously weaken the shock propagation and decrease its velocity after propagating into the ablator plasma. Consequently, longer time duration is provided for the symmetrical target implosion driven by radiation ablation. In this paper these processes are numerically investigated by changing drive currents or varying load parameters. The simulation results show that a critical hohlraum radiation temperature is needed to provide a high enough ablation pressure to decelerate the shock, thus providing long enough time duration for the symmetric fuel compression driven by radiation ablation.

  5. Numerical investigation on target implosions driven by radiation ablation and shock compression in dynamic hohlraums

    NASA Astrophysics Data System (ADS)

    Xiao, Delong; Sun, Shunkai; Zhao, Yingkui; Ding, Ning; Wu, Jiming; Dai, Zihuan; Yin, Li; Zhang, Yang; Xue, Chuang

    2015-05-01

    In a dynamic hohlraum driven inertial confinement fusion (ICF) configuration, the target may experience two different kinds of implosions. One is driven by hohlraum radiation ablation, which is approximately symmetric at the equator and poles. The second is caused by the radiating shock produced in Z-pinch dynamic hohlraums, only taking place at the equator. To gain a symmetrical target implosion driven by radiation ablation and avoid asymmetric shock compression is a crucial issue in driving ICF using dynamic hohlraums. It is known that when the target is heated by hohlraum radiation, the ablated plasma will expand outward. The pressure in the shocked converter plasma qualitatively varies linearly with the material temperature. However, the ablation pressure in the ablated plasma varies with 3.5 power of the hohlraum radiation temperature. Therefore, as the hohlraum temperature increases, the ablation pressure will eventually exceed the shock pressure, and the expansion of the ablated plasma will obviously weaken the shock propagation and decrease its velocity after propagating into the ablator plasma. Consequently, longer time duration is provided for the symmetrical target implosion driven by radiation ablation. In this paper these processes are numerically investigated by changing drive currents or varying load parameters. The simulation results show that a critical hohlraum radiation temperature is needed to provide a high enough ablation pressure to decelerate the shock, thus providing long enough time duration for the symmetric fuel compression driven by radiation ablation.

  6. Bumper wall for plasma device

    DOEpatents

    Coultas, Thomas A.

    1977-01-01

    Operation of a plasma device such as a reactor for controlled thermonuclear fusion is facilitated by an improved bumper wall enclosing the plasma to smooth the flow of energy from the plasma as the energy impinges upon the bumper wall. The bumper wall is flexible to withstand unequal and severe thermal shocks and it is readily replaced at less expense than the cost of replacing structural material in the first wall and blanket that surround it.

  7. Radiofrequency Ablation of Metastatic Pheochromocytoma

    PubMed Central

    Venkatesan, Aradhana M.; Locklin, Julia; Lai, Edwin W.; Adams, Karen T.; Fojo, Antonio Tito; Pacak, Karel; Wood, Bradford J.

    2013-01-01

    In the present report on the preliminary safety and effectiveness of radiofrequency (RF) ablation for pheochromocytoma metastases, seven metastases were treated in six patients (mean size, 3.4 cm; range, 2.2–6 cm). α- and β-adrenergic and catecholamine synthesis inhibition and intraprocedural anesthesia monitoring were used. Safety was assessed by recording ablation-related complications. Complete ablation was defined as a lack of enhancement within the ablation zone on follow-up computed tomography. No serious adverse sequelae were observed. Complete ablation was achieved in six of seven metastases (mean follow-up, 12.3 months; range, 2.5–28 months). In conclusion, RF ablation may be safely performed for metastatic pheochromocytoma given careful attention to peri-procedural management. PMID:19875067

  8. OCDR guided laser ablation device

    DOEpatents

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

    2002-01-01

    A guided laser ablation device. The device includes a mulitmode laser ablation fiber that is surrounded by one or more single mode optical fibers that are used to image in the vicinity of the laser ablation area to prevent tissue damage. The laser ablation device is combined with an optical coherence domain reflectometry (OCDR) unit and with a control unit which initializes the OCDR unit and a high power laser of the ablation device. Data from the OCDR unit is analyzed by the control unit and used to control the high power laser. The OCDR images up to about 3 mm ahead of the ablation surface to enable a user to see sensitive tissue such as a nerve or artery before damaging it by the laser.

  9. Calcified lesion modeling for excimer laser ablation

    NASA Astrophysics Data System (ADS)

    Scott, Holly A.; Archuleta, Andrew; Splinter, Robert

    2009-06-01

    Objective: Develop a representative calcium target model to evaluate penetration of calcified plaque lesions during atherectomy procedures using 308 nm Excimer laser ablation. Materials and Methods: An in-vitro model representing human calcified plaque was analyzed using Plaster-of-Paris and cement based composite materials as well as a fibrinogen model. The materials were tested for mechanical consistency. The most likely candidate(s) resulting from initial mechanical and chemical screening was submitted for ablation testing. The penetration rate of specific multi-fiber catheter designs and a single fiber probe was obtained and compared to that in human cadaver calcified plaque. The effects of lasing parameters and catheter tip design on penetration speed in a representative calcified model were verified against the results in human cadaver specimens. Results: In Plaster of Paris, the best penetration was obtained using the single fiber tip configuration operating at 100 Fluence, 120 Hz. Calcified human lesions are twice as hard, twice as elastic as and much more complex than Plaster of Paris. Penetration of human calcified specimens was highly inconsistent and varied significantly from specimen to specimen and within individual specimens. Conclusions: Although Plaster of Paris demonstrated predictable increases in penetration with higher energy density and repetition rate, it can not be considered a totally representative laser ablation model for calcified lesions. This is in part due to the more heterogeneous nature and higher density composition of cadaver intravascular human calcified occlusions. Further testing will require a more representative model of human calcified lesions.

  10. TRANSIENT RESPONSE OF ABLATING AXISYMMETRIC BODIES INCLUDING THE EFFECTS OF SHAPE CHANGE

    NASA Technical Reports Server (NTRS)

    Howser, L. M.

    1994-01-01

    A computer program has been developed to analyze the transient response of an ablating axisymmetric body, including the effect of shape change. The governing differential equation, the boundary conditions for the analysis on which the computer program is based, and the method of solution of the resulting finite-difference equations are discussed in the documentation. Some of the features of the analysis and the associated program are (1) the ablation material is considered to be orthotropic with temperature-dependent thermal properties; (2) the thermal response of the entire body is considered simultaneously; (3) the heat transfer and pressure distribution over the body are adjusted to the new geometry as ablation occurs; (4) the governing equations and several boundary-condition options are formulated in terms of generalized orthogonal coordinates for fixed points in a moving coordinate system; (5) the finite-difference equations are solved implicitly; and (6) other instantaneous body shapes can be displayed with a user-supplied plotting routine. The physical problem to be modeled with the analysis is described by FORTRAN input variables. For example, the external body geometry is described in the W, Z coordinates; material density is given; and the stagnation cold-wall heating rate is given in a time-dependent array. Other input variables are required which control the solution, specify boundary conditions, and determine output from the program. The equations have been programmed so that either the International System of Units or the U. S. Customary Units may be used. This program is written in FORTRAN IV for batch execution and has been implemented on a CDC 6000 Series computer. This program was developed in 1972.

  11. Sensing the Structural Differences in Cellulose from Apple and Bacterial Cell Wall Materials by Raman and FT-IR Spectroscopy

    PubMed Central

    Szymańska-Chargot, Monika; Cybulska, Justyna; Zdunek, Artur

    2011-01-01

    Raman and Fourier Transform Infrared (FT-IR) spectroscopy was used for assessment of structural differences of celluloses of various origins. Investigated celluloses were: bacterial celluloses cultured in presence of pectin and/or xyloglucan, as well as commercial celluloses and cellulose extracted from apple parenchyma. FT-IR spectra were used to estimate of the Iβ content, whereas Raman spectra were used to evaluate the degree of crystallinity of the cellulose. The crystallinity index (XCRAMAN%) varied from −25% for apple cellulose to 53% for microcrystalline commercial cellulose. Considering bacterial cellulose, addition of xyloglucan has an impact on the percentage content of cellulose Iβ. However, addition of only xyloglucan or only pectins to pure bacterial cellulose both resulted in a slight decrease of crystallinity. However, culturing bacterial cellulose in the presence of mixtures of xyloglucan and pectins results in an increase of crystallinity. The results confirmed that the higher degree of crystallinity, the broader the peak around 913 cm−1. Among all bacterial celluloses the bacterial cellulose cultured in presence of xyloglucan and pectin (BCPX) has the most similar structure to those observed in natural primary cell walls. PMID:22163913

  12. Development of an energetic plasma source for simulating edge localized mode plasma interactions with first wall and diverter materials

    NASA Astrophysics Data System (ADS)

    Ruzic, David

    2005-10-01

    Edge Localized Modes (ELMs) pose a significant problem to current and future fusion reactors. One concern in a device such as ITER is that ELMs may be the limiting factor for successful operation. ITER ELMs are predicted to impart between 1 -- 10 MJ/m^2 onto the divertor surface and first wall of the reactor. This may lead to significant erosion of the divertors and possible melting. The ELM Simulating Plasma gun (ESP-gun) in operation at UIUC is intended to produce plasmas similar to those found in TOKAMAK ELM events. ESP-gun operates with several small pulse forming networks (PFN) that are sequentially triggered to produce a ringing, under-damped current waveform with peak currents in excess of 50 kA. Each PFN is connected to the conical theta pinch to produce high Te, high ne plasmas similar to ELM events. A Triple Langmuir Probe (TLP) diagnoses and measures the quality of the plasmas produced by the ESP-gun. To date, an ne of 1(10)^19/m^3 and greater with a Te greater than 50 eV in the target area have been measured. From these measurements, plasma energies can be calculated. Axial magnetic field measurements during the theta pinch at the location of the coil and at a downstream target are accomplished.

  13. Material deposition on inner divertor quartz-micro balances during ITER-like wall operation in JET

    NASA Astrophysics Data System (ADS)

    Esser, H. G.; Philipps, V.; Freisinger, M.; Widdowson, A.; Heinola, K.; Kirschner, A.; Möller, S.; Petersson, P.; Brezinsek, S.; Huber, A.; Matthews, G. F.; Rubel, M.; Sergienko, G.

    2015-08-01

    The migration of beryllium, tungsten and carbon to remote areas of the inner JET-ILW divertor and the accompanying co-deposition of deuterium has been investigated using post-mortem analysis of the housings of quartz-micro balances (QMBs) and their quartz crystals. The analysis of the deposition provides that the rate of beryllium atoms is significantly reduced compared to the analogue deposition rate of carbon during the carbon wall conditions (JET-C) at the same locations of the QMBs. A reduction factor of 50 was found at the entrance gap to the cryo-pumps while it was 14 under tile 5, the semi-horizontal target plate. The deposits consist of C/Be atomic ratios of typically 0.1-0.5 showing an enrichment of carbon in remote areas compared to directly exposed areas with less carbon. The deuterium retention fraction D/Be is between 0.3 and 1 at these unheated locations in the divertor.

  14. Diamagnetic composite material structure for reducing undesired electromagnetic interference and eddy currents in dielectric wall accelerators and other devices

    DOEpatents

    Caporaso, George J.; Poole, Brian R.; Hawkins, Steven A.

    2015-06-30

    The devices, systems and techniques disclosed here can be used to reduce undesired effects by magnetic field induced eddy currents based on a diamagnetic composite material structure including diamagnetic composite sheets that are separated from one another to provide a high impedance composite material structure. In some implementations, each diamagnetic composite sheet includes patterned conductor layers are separated by a dielectric material and each patterned conductor layer includes voids and conductor areas. The voids in the patterned conductor layers of each diamagnetic composite sheet are arranged to be displaced in position from one patterned conductor layer to an adjacent patterned conductor layer while conductor areas of the patterned conductor layers collectively form a contiguous conductor structure in each diamagnetic composite sheet to prevent penetration by a magnetic field.

  15. Multi-scale finite element model for a new material inspired by the mechanics and structure of wood cell-walls

    NASA Astrophysics Data System (ADS)

    Saavedra Flores, E. I.; Friswell, M. I.

    2012-07-01

    This paper proposes a fully coupled multi-scale finite element model for the constitutive description of an alumina/magnesium alloy/epoxy composite inspired in the mechanics and structure of the wall of wood cells. The mechanical response of the composite (the large scale continuum) is described by means of a representative volume element (RVE, corresponding to the intermediate scale) in which the fibre is represented as a periodic alternation of alumina and magnesium alloy fractions. Furthermore, at a lower scale the overall constitutive behavior of the alumina/magnesium alloy fibre is modelled as a single material defined by a large number of RVEs (the smallest material scale) at the Gauss point (intermediate) level. Numerical material tests show that this new composite maximises its toughness when the hierarchical design of wood cellulose fibres is replicated. The above results provide for the first time new clues into the understanding of how trees and plants optimise their microstructures at the cellulose level in order to absorb a large amount of strain energy before failure. These findings are likely to shed more light into natural materials and bio-inspired design strategies, which are still not well-understood at present.

  16. Thermal Ablation of Lung Tissue: In Vivo Experimental Comparison of Microwave and Radiofrequency

    SciTech Connect

    Crocetti, Laura Bozzi, Elena; Faviana, Pinuccia; Cioni, Dania; Della Pina, Clotilde; Sbrana, Alberto; Fontanini, Gabriella; Lencioni, Riccardo

    2010-08-15

    This study was designed to compare feasibility, safety, and effectiveness of microwave (MW) ablation versus radiofrequency (RF) ablation of lung tissue in a rabbit model. Twenty New Zealand White rabbits were submitted to MW (n = 10, group A) or RF ablation (n = 10, group B). The procedures were performed with a prototype MW ablation device with a 1.6-cm radiating section antenna (Valleylab MW Ablation System) and with a 2-cm exposed-tip RF electrode (Cool-tip RF Ablation System). At immediate computed tomography increase in density, maximum diameters (D1-D3) of ablation zones were measured and ablation volume was calculated. Histopathologic assessment was performed 3 and 7 days after the procedure. Technical success was achieved in nine of 10 rabbits in each group. One death occurred in group B. Complications included pneumothorax (group A, n = 4; group B, n = 4), abscess (group A, n = 1; group B, n = 1), and thoracic wall burn (group A, n = 4). No significant differences were demonstrated in attenuation increase (P = 0.73), dimensions (P = 0.28, 0.86, 0.06, respectively, comparing D1-D3) and volume (P = 0.17). At histopathology, ablation zones were similar, with septal necrosis, edema, hemorrhage, and peripheral lymphocytic infiltrate. Complete thrombosis of more than 90% of vessels up to 2 mm in diameter was depicted at the periphery of the ablation zone in group A specimens. In group B specimens, complete thrombosis was depicted in 20% of vessels. Feasibility and safety of MW and RF ablation are similar in a lung rabbit model. MW ablation produces a greater damage to peripheral small vessels inducing thrombosis.

  17. Wire ablation dynamics model and its application to imploding wire arrays of different geometries.

    PubMed

    Esaulov, A A; Kantsyrev, V L; Safronova, A S; Velikovich, A L; Shrestha, I K; Williamson, K M; Osborne, G C

    2012-10-01

    The paper presents an extended description of the amplified wire ablation dynamics model (WADM), which accounts in a single simulation for the processes of wire ablation and implosion of a wire array load of arbitrary geometry and wire material composition. To investigate the role of wire ablation effects, the implosions of cylindrical and planar wire array loads at the university based generators Cobra (Cornell University) and Zebra (University of Nevada, Reno) have been analyzed. The analysis of the experimental data shows that the wire mass ablation rate can be described as a function of the current through the wire and some coefficient defined by the wire material properties. The aluminum wires were found to ablate with the highest rate, while the copper ablation is the slowest one. The lower wire ablation rate results in a higher inward velocity of the ablated plasma, a higher rate of the energy coupling with the ablated plasma, and a more significant delay of implosion for a heavy load due to the ablation effects, which manifest the most in a cylindrical array configuration and almost vanish in a single-planar array configuration. The WADM is an efficient tool suited for wire array load design and optimization in wide parameter ranges, including the loads with specific properties needed for the inertial confinement fusion research and laboratory astrophysics experiments. The data output from the WADM simulation can be used to simplify the radiation magnetohydrodynamics modeling of the wire array plasma. PMID:23214697

  18. Wire ablation dynamics model and its application to imploding wire arrays of different geometries

    NASA Astrophysics Data System (ADS)

    Esaulov, A. A.; Kantsyrev, V. L.; Safronova, A. S.; Velikovich, A. L.; Shrestha, I. K.; Williamson, K. M.; Osborne, G. C.

    2012-10-01

    The paper presents an extended description of the amplified wire ablation dynamics model (WADM), which accounts in a single simulation for the processes of wire ablation and implosion of a wire array load of arbitrary geometry and wire material composition. To investigate the role of wire ablation effects, the implosions of cylindrical and planar wire array loads at the university based generators Cobra (Cornell University) and Zebra (University of Nevada, Reno) have been analyzed. The analysis of the experimental data shows that the wire mass ablation rate can be described as a function of the current through the wire and some coefficient defined by the wire material properties. The aluminum wires were found to ablate with the highest rate, while the copper ablation is the slowest one. The lower wire ablation rate results in a higher inward velocity of the ablated plasma, a higher rate of the energy coupling with the ablated plasma, and a more significant delay of implosion for a heavy load due to the ablation effects, which manifest the most in a cylindrical array configuration and almost vanish in a single-planar array configuration. The WADM is an efficient tool suited for wire array load design and optimization in wide parameter ranges, including the loads with specific properties needed for the inertial confinement fusion research and laboratory astrophysics experiments. The data output from the WADM simulation can be used to simplify the radiation magnetohydrodynamics modeling of the wire array plasma.

  19. Ames Infusion Stories for NASA Annual Technology Report: Development of an Ablative 3D Quartz / Cyanate Ester Composite Multi-Functional Material for the Orion Spacecraft Compression Pad

    NASA Technical Reports Server (NTRS)

    Smith, Brandon; Jan, Darrell Leslie; Venkatapathy, Ethiraj

    2015-01-01

    Vehicles re-entering Earth's atmosphere require protection from the heat of atmospheric friction. The Orion Multi-Purpose Crew Vehicle (MPCV) has more demanding thermal protection system (TPS) requirements than the Low Earth Orbit (LEO) missions, especially in regions where the structural load passes through. The use of 2-dimensional laminate materials along with a metal insert, used in EFT1 flight test for the compression pad region, are deemed adequate but cannot be extended for Lunar return missions.

  20. Single-shot ablation threshold of chromium using UV femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Banerjee, S. P.; Fedosejevs, R.

    2014-07-01

    Single-shot ablation threshold for thin chromium film was studied using 266 nm, femtosecond laser pulses. Chromium is a useful material in the nanotechnology industry and information on ablation threshold using UV femtosecond pulses would help in precise micromachining of the material. The ablation threshold was determined by measuring the ablation crater diameters as a function of incident laser pulse energy. Absorption of 266 nm light on the chromium film was also measured under our experimental conditions, and the absorbed energy single-shot ablation threshold fluence was 46 ± 5 mJ/cm2. The experimental ablation threshold fluence value was compared to time-dependent heat flow calculations based on the two temperature model for ultrafast laser pulses. The model predicts a value of 31.6 mJ/cm2 which is qualitatively consistent with the experimentally obtained value, given the simplicity of the model.

  1. Effect of water to ablative performance under solid rocket exhaust environment

    NASA Astrophysics Data System (ADS)

    Miller, M. J.; Koo, J. H.; Sickler, F. M.; Lecureux, F.; Dash, S. M.

    1993-06-01

    The local environment during a missile firing is particularly hostile. Thermal protection of the missile launcher structure is often achieved with ablatives. Ablatives erode when subjected to high-temperature rocket exhaust, but the backside temperature of the protected structure remains relatively cool due to the insulative nature of ablatives. Multiple missile firings can completely erode the ablative, exposing the launching system components to an extremely high temperature. This investigation addresses the concept of injecting water into the missile plume to reduce the amount of ablative erosion per missile firing. This concept also reduces the amount of ablative materials needed in missile launching systems. Injecting water into the exhaust plume in a controlled laboratory environment was performed. Heat flux and material erosion measurements were compared in this study.

  2. Verification and Validation of EnergyPlus Conduction Finite Difference and Phase Change Material Models for Opaque Wall Assemblies

    SciTech Connect

    Tabares-Velasco, Paulo Cesar; Christensen, Craig; Bianchi, Marcus; Booten, Chuck

    2012-07-01

    Phase change materials (PCMs) represent a potential technology to reduce peak loads and HVAC energy consumption in buildings. There are few building energy simulation programs that have the capability to simulate PCM but their accuracy has not been completely tested. This report summarizes NREL efforts to develop diagnostic tests cases to obtain accurate energy simulations when PCMs are modeled in residential buildings.

  3. Regional Pericarditis Status Post Cardiac Ablation: A Case Report

    PubMed Central

    Orme, Joseph; Eddin, Moneer; Loli, Akil

    2014-01-01

    Context: Regional pericarditis is elusive and difficult to diagnosis. Healthcare providers should be familiar with post-cardiac ablation complications as this procedure is now widespread and frequently performed. The management of regional pericarditis differs greatly from that of acute myocardial infarction. Case report: A 52 year-old male underwent atrial fibrillation ablation and developed severe mid-sternal chest pain the following day with electrocardiographic findings suggestive of acute myocardial infarction, and underwent coronary angiography, a left ventriculogram, and 2D transthoracic echocardiogram, all of which were unremarkable without evidence of obstructive coronary disease, wall motion abnormalities, or pericardial effusions. Ultimately, the patient was diagnosed with regional pericarditis. After diagnosis, the patient's presenting symptoms resolved with treatment including nonsteroidal anti-inflammatory agents and colchicine. Conclusion: This is the first reported case study of regional pericarditis status post cardiac ablation. Electrocardiographic findings were classic for an acute myocardial infarction; however, coronary angiography and left ventriculogram demonstrated no acute coronary occlusion or ventricular wall motion abnormalities. Healthcare professionals must remember that the electrocardiographic findings in pericarditis are not always classic and that pericarditis can occur status post cardiac ablation. PMID:25317395

  4. MRI-guided laser ablation of neuroendocrine tumor hepatic metastases

    PubMed Central

    Perälä, Jukka; Klemola, Rauli; Kallio, Raija; Li, Chengli; Vihriälä, Ilkka; Salmela, Pasi I; Tervonen, Osmo

    2014-01-01

    Background Neuroendocrine tumors (NET) represent a therapeutically challenging and heterogeneous group of malignancies occurring throughout the body, but mainly in the gastrointestinal system. Purpose To describe magnetic resonance imaging (MRI)-guided laser ablation of NET liver metastases and assess its role within the current treatment options and methods. Material and Methods Two patients with NET tumor hepatic metastases were treated with MRI-guided interstitial laser ablation (LITT). Three tumors were treated. Clinical follow-up time was 10 years. Results Both patients were successfully treated. There were no local recurrences at the ablation site during the follow-up. Both patients had survived at 10-year follow-up. One patient is disease-free. Conclusion MRI-guided laser ablation can be used to treat NET tumor liver metastases but combination therapy and a rigorous follow-up schedule are recommended. PMID:24778794

  5. Artificial meteor ablation studies. [for identification of cosmic dust particles

    NASA Technical Reports Server (NTRS)

    Blanchard, M. B.

    1973-01-01

    Artificial meteor ablation was performed on natural minerals, composed predominately of magnetite and hematite, using an arc heated plasma stream of air. Analysis of the ablated debris indicated most was composed of two or more minerals. The more volatile elements were depleted and the relative abundance of Fe increased as a result of both volatile depletion and a reduction in its oxidation state. Hematite was converted to magnetite in the ablation zone, and quartz and apatite minerals were converted to an Fe-rich glass consisting of varying amounts of Si, P, Cl, and Ca, depending upon the accessory minerals available at the time of melting. Artificially created ablation products from iron oxides exhibited unique properties depending on the composition of the original material and the environmental conditions of formation. In addition to the accepted elemental criteria, these properties were morphologic characteristics, textural parameters, and the existence of metastable minerals.

  6. Laser ablation in analytical chemistry-a review.

    PubMed

    Russo, Richard E; Mao, Xianglei; Liu, Haichen; Gonzalez, Jhanis; Mao, Samuel S

    2002-05-24

    Laser ablation is becoming a dominant technology for direct solid sampling in analytical chemistry. Laser ablation refers to the process in which an intense burst of energy delivered by a short laser pulse is used to sample (remove a portion of) a material. The advantages of laser ablation chemical analysis include direct characterization of solids, no chemical procedures for dissolution, reduced risk of contamination or sample loss, analysis of very small samples not separable for solution analysis, and determination of spatial distributions of elemental composition. This review describes recent research to understand and utilize laser ablation for direct solid sampling, with emphasis on sample introduction to an inductively coupled plasma (ICP). Current research related to contemporary experimental systems, calibration and optimization, and fractionation is discussed, with a summary of applications in several areas. PMID:18968642

  7. Novel catheter enabling simultaneous radiofrequency ablation and optical coherence reflectometry

    PubMed Central

    Herranz, D.; Lloret, Juan; Jiménez-Valero, Santiago; Rubio-Guivernau, J. L.; Margallo-Balbás, Eduardo

    2015-01-01

    A novel radiofrequency ablation catheter has been developed with integrated custom designed optics, enabling real-time monitoring of radiofrequency ablation procedures through polarization-sensitive optical coherence reflectometry. The optics allow for proper tissue illumination through a view-port machined in the catheter tip, thus providing lesion depth control over the RF ablation treatment. The system was verified in an in-vitro model of swine myocardium. Optical performance and thermal stability was confirmed after more than 25 procedures, without any damage to the optical assembly induced by thermal stress or material degradation. The use of this catheter in RF ablation treatments may make possible to assess lesion depth during therapy, thus translating into a reduction of potential complications on the procedure. PMID:26417499

  8. High pressure, energy, and impulse loading of the wall in a 1-GJ Laboratory Microfusion Facility

    SciTech Connect

    Harrach, R.J.

    1989-07-24

    A proposed Laboratory Microfusion Facility (LMF) must be able to withstand repeated, low-repetition-rate fusion explosions at the 1-GJ (one-quarter ton) yield level. The energy release will occur at the center of a chamber only a few meters in radius, subjecting the interior or first wall to severe levels of temperature, pressure, and impulse. We show by theory and computation that the wall loading can be ameliorated by interposing a spherical shell of low-Z material between the fuel and the wall. This sacrificial shield converts the source energy components that are most damaging to the wall (soft x-rays and fast ions) to more benign plasma kinetic energy from the vaporized shield, and stretches the time duration over which this energy is delivered to the wall from nanoseconds to microseconds. Numerical calculations emphasize thin, volleyball-sized plastic shields, and much thicker ones of frozen nitrogen. Wall shielding criteria of small (or no) amount of surface ablation, low impulse and pressure loading, minimal shrapnel danger, small expense, and convenience in handling all favor the thin plastic shields. 7 refs., 4 figs.

  9. The effect of external mean flow on sound transmission through double-walled cylindrical shells lined with poroelastic material

    NASA Astrophysics Data System (ADS)

    Zhou, Jie; Bhaskar, Atul; Zhang, Xin

    2014-03-01

    Sound transmission through a system of double shells, lined with poroelastic material in the presence of external mean flow, is studied. The porous material is modeled as an equivalent fluid because shear wave contributions are known to be insignificant. This is achieved by accounting for the energetically most dominant wave types in the calculations. The transmission characteristics of the sandwich construction are presented for different incidence angles and Mach numbers over a wide frequency range. It is noted that the transmission loss exhibits three dips on the frequency axis as opposed to flat panels where there are only two such frequencies—results are discussed in the light of these observations. Flow is shown to decrease the transmission loss below the ring frequency, but increase this above the ring frequency due to the negative stiffness and the damping effect added by the flow. In the absence of external mean flow, porous material provides superior insulation for most part of the frequency band of interest. However, in the presence of external flow, this is true only below the ring frequency—above this frequency, the presence of air gap in sandwich constructions is the dominant factor that determines the acoustic performance. In the absence of external flow, an air gap always improves sound insulation.

  10. Unipolar p-type single-walled carbon nanotube field-effect transistors using TTF-TCNQ as the contact material.

    PubMed

    Xian, Xiaojun; Yan, Kai; Zhou, Wei; Jiao, Liying; Wu, Zhongyun; Liu, Zhongfan

    2009-12-16

    We demonstrate herein that organic metal tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) can serve as an ideal material for source and drain electrodes to build unipolar p-type single-walled carbon nanotube (SWNTs) field-effect transistors (FETs). SWNTs were synthesized by the chemical vapor deposition (CVD) method on silicon wafer and then TTF-TCNQ was deposited by thermal evaporation through a shadow mask to form the source and drain contacts. An SiO2 layer served as the gate dielectric and Si was used as the backgate. Transfer characteristics show that these TTF-TCNQ contacted devices are Schottky barrier transistors just like conventional metal contacted SWNT-FETs. The most interesting characteristic of these SWNT transistors is that all devices demonstrate the unipolar p-type transport behavior. This behavior originates from the unique crystal structure and physical properties of TTF-TCNQ and this device may have potential applications in carbon nanotube electronics. PMID:19923654

  11. Unipolar p-type single-walled carbon nanotube field-effect transistors using TTF-TCNQ as the contact material

    NASA Astrophysics Data System (ADS)

    Xian, Xiaojun; Yan, Kai; Zhou, Wei; Jiao, Liying; Wu, Zhongyun; Liu, Zhongfan

    2009-12-01

    We demonstrate herein that organic metal tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) can serve as an ideal material for source and drain electrodes to build unipolar p-type single-walled carbon nanotube (SWNTs) field-effect transistors (FETs). SWNTs were synthesized by the chemical vapor deposition (CVD) method on silicon wafer and then TTF-TCNQ was deposited by thermal evaporation through a shadow mask to form the source and drain contacts. An SiO2 layer served as the gate dielectric and Si was used as the backgate. Transfer characteristics show that these TTF-TCNQ contacted devices are Schottky barrier transistors just like conventional metal contacted SWNT-FETs. The most interesting characteristic of these SWNT transistors is that all devices demonstrate the unipolar p-type transport behavior. This behavior originates from the unique crystal structure and physical properties of TTF-TCNQ and this device may have potential applications in carbon nanotube electronics.

  12. On sound transmission through double-walled cylindrical shells lined with poroelastic material: Comparison with Zhou's results and further effect of external mean flow

    NASA Astrophysics Data System (ADS)

    Liu, Yu; He, Chuanbo

    2015-12-01

    In this discussion, the corrections to the errors found in the derivations and the numerical code of a recent analytical study (Zhou et al. Journal of Sound and Vibration 333 (7) (2014) 1972-1990) on sound transmission through double-walled cylindrical shells lined with poroelastic material are presented and discussed, as well as the further effect of the external mean flow on the transmission loss. After applying the corrections, the locations of the characteristic frequencies of thin shells remain unchanged, as well as the TL results above the ring frequency where BU and UU remain the best configurations in sound insulation performance. In the low-frequency region below the ring frequency, however, the corrections attenuate the TL amplitude significantly for BU and UU, and hence the BB configuration exhibits the best performance which is consistent with previous observations for flat sandwich panels.

  13. [Chest wall reconstruction after resection of malignant chest wall tumors].

    PubMed

    Ayabe, H; Oka, T; Akamine, S; Takahashi, T; Nagayasu, T

    1998-05-01

    Full-thickness chest wall resection is performed for complete removal of primary and secondary malignant chest wall tumors. Large defects of the chest wall after resection must be repaired to maintain adequate ventilation, to protect important intrathoracic structures, and to preserve cosmetic integrity. Various materials have been utilized over the years to replace the rigid chest wall. At present, Marlex mesh and a composite of Marlex mesh and methylmethacrylate are frequently used to reconstruct rigid chest wall defects. On the other hand, to replace the soft part of the chest wall and cover the rigid materials, pedicled muscle flaps, myocutaneous flaps, or omentum are used. Major pedicled flaps include the pectoralis major, rectus abdominis and latissimus dorsi muscular, and musculocutaneous flaps. Techniques are now available to repair any chest wall site, and to restore chest continuity in patients whose tumors are curatively resected. PMID:9656244

  14. The Influence of Ablation on Radiative Heating for Earth Entry

    NASA Technical Reports Server (NTRS)

    Johnston, Christopher O.; Gnoffo, Peter A.; Sutton, Kenneth

    2008-01-01

    Using the coupled ablation and radiation capability recently included in the LAURA flowfield solver, this paper investigates the influence of ablation on the shock-layer radiative heating for Earth entry. The extension of the HARA radiation model, which provides the radiation predictions in LAURA, to treat a gas consisting of the elements C, H, O, and N is discussed. It is shown that the absorption coefficient of air is increased with the introduction of the C and H elements. A simplified shock layer model is studied to show the impact of temperature, as well as the abundance of C and H, on the net absorption or emission from an ablation contaminated boundary layer. It is found that the ablation species reduce the radiative flux in the vacuum ultraviolet, through increased absorption, for all temperatures. However, in the infrared region of the spectrum, the ablation species increase the radiative flux, through strong emission, for temperatures above 3,000 K. Thus, depending on the temperature and abundance of ablation species, the contaminated boundary layer may either provide a net increase or decrease in the radiative flux reaching the wall. To assess the validity of the coupled ablation and radiation LAURA analysis, a previously analyzed Mars-return case (15.24 km/s), which contains significant ablation and radiation coupling, is studied. Exceptional agreement with previous viscous shock-layer results is obtained. A 40% decrease in the radiative flux is predicted for ablation rates equal to 20% of the free-stream mass flux. The Apollo 4 peak-heating case (10.24 km/s) is also studied. For ablation rates up to 3.4% of the free-stream mass flux, the radiative heating is reduced by up to 19%, while the convective heating is reduced by up to 87%. Good agreement with the Apollo 4 radiometer data is obtained by considering absorption in the radiometer cavity. For both the Mars return and the Apollo 4 cases, coupled radiation alone is found to reduce the radiative

  15. Plasma mediated ablation of biological tissues with ultrashort laser pulses

    SciTech Connect

    Oraevsky, A.A. |; DaSilva, L.B.; Feit, M.D.

    1995-03-08

    Plasma mediated ablation of collagen gels and porcine cornea was studied at various laser pulse durations in the range from 350 fs to 1 ns at 1,053 nm wavelength. A time resolved stress detection technique was employed to measure transient stress profiles and amplitudes. Optical microscopy was used to characterize ablation craters qualitatively, while a wide band acoustic transducer helped to quantify tissue mechanical response and the ablation threshold. The ablation threshold was measured as a function of laser pulse duration and linear absorption coefficient. For nanosecond pulses the ablation threshold was found to have a strong dependence on the linear absorption coefficient of the material. As the pulse length decreased into the subpicosecond regime the ablation threshold became insensitive to the linear absorption coefficient. The ablation efficiency was found to be insensitive to both the laser pulse duration and the linear absorption coefficient. High quality ablation craters with no thermal or mechanical damage to surrounding material were obtained with 350 fs laser pulses. The mechanism of optical breakdown at the tissue surface was theoretically investigated. In the nanosecond regime, optical breakdown proceeds as an electron collisional avalanche ionization initiated by thermal seed electrons. These seed electrons are created by heating of the tissue by linear absorption. In the ultrashort pulse range, optical breakdown is initiated by the multiphoton ionization of the irradiated medium (6 photons in case of tissue irradiated at 1,053 nm wavelength), and becomes less sensitive to the linear absorption coefficient. The energy deposition profile is insensitive to both the laser pulse duration and the linear absorption coefficient.

  16. Ablation and Thermal Response Property Model Validation for Phenolic Impregnated Carbon Ablator

    NASA Technical Reports Server (NTRS)

    Milos, F. S.; Chen, Y.-K.

    2009-01-01

    Phenolic Impregnated Carbon Ablator was the heatshield material for the Stardust probe and is also a candidate heatshield material for the Orion Crew Module. As part of the heatshield qualification for Orion, physical and thermal properties were measured for newly manufactured material, included emissivity, heat capacity, thermal conductivity, elemental composition, and thermal decomposition rates. Based on these properties, an ablation and thermal-response model was developed for temperatures up to 3500 K and pressures up to 100 kPa. The model includes orthotropic and pressure-dependent thermal conductivity. In this work, model validation is accomplished by comparison of predictions with data from many arcjet tests conducted over a range of stagnation heat flux and pressure from 107 Watts per square centimeter at 2.3 kPa to 1100 Watts per square centimeter at 84 kPa. Over the entire range of test conditions, model predictions compare well with measured recession, maximum surface temperatures, and in depth temperatures.

  17. Electrical and Material Characteristics of Low Pressure Chemical-Vapor Deposited Tungsten Films in Cold Wall Systems.

    NASA Astrophysics Data System (ADS)

    Joshi, Rajiv V.

    The kinetics and related mechanisms of non-self limiting nature of Si reduction of WF_6 in cold wall systems are investigated. The growth of such films in Low Pressure Chemical Vapor Deposition (LPCVD) and Ultra High Vacuum (UHV) systems is compared. Based on thermodynamic considerations, the origin of W-O layer is attributed to a secondary reaction between water vapors, WF_6 and substrate Si. The beneficial role played by the W-O layer is that it prevents the volume shrinkage and restricts lateral encroachment. A physical model is proposed which explains the non-self limiting growth of W films based on the microstructure of the film, the process parameters, the presence of W-O, and the Si gradient across the W films. The surface science study in the UHV system has helped in developing this model. It is postulated that the fine grained W structure surrounded by W-O layer formed in the LPCVD system assists in faster out-diffusion of Si through W films compared to an UHV system. This explains why the activation energy (0.2 eV) is lower for Si out-diffusion through films grown in the LPCVD system than that for the UHV system (0.48 eV). This, also, supports the significantly lower values of coefficient for Si out-diffusion in the case of LPCVD system. The out-diffused Si is substituted to W to complete the film growth. The effects of deposition temperature on growth, composition, structure, adhesion properties, stress and resistivity of tungsten films deposited purely by SiH _4 reduction of WF_6 are also reported. Silicon reduced W is characterized electrically by fabricating Schottky Barriers and FET (Field Effect Transistors). Increased diffusion of Si into W as a function of deposition temperature increases the barrier height from 0.60 eV to 0.64 eV. The contact resistances of Si reduced W surrounded by amorphous layer of W-O is very close to that for H_2 reduced W. Raised source and drain are formed on NFET and PFET by low temperature selective epitaxial Si, which

  18. Radiative ablation of disks around massive stars

    NASA Astrophysics Data System (ADS)

    Kee, Nathaniel Dylan

    Hot, massive stars (spectral types O and B) have extreme luminosities (10. 4 -10. 6 L?) that drive strong stellar winds through UV line-scattering.Some massive stars also have disks, formed by either decretion from the star (as in the rapidly rotating "Classical Be stars"), or accretion during the star's formation. This dissertation examines the role of stellar radiation in driving (ablating) material away from these circumstellar disks. A key result is that the observed month to year decay of Classical Be disks can be explained by line-driven ablation without, as previously done, appealing to anomalously strong viscous diffusion. Moreover, the higher luminosity of O stars leads to ablation of optically thin disks on dynamical timescales of order a day, providing a natural explanation for the lack of observed Oe stars. In addition to the destruction of Be disks, this dissertation also introduces a model for their formation by coupling observationally inferred non-radial pulsation modes and rapid stellar rotation to launch material into orbiting Keplerian disks of Be-like densities. In contrast to such Be decretion disks, star-forming accretion disks are much denser and so are generally optically thick to continuum processes. To circumvent the computational challenges associated with radiation hydrodynamics through optically thick media, we develop an approximate method for treating continuum absorption in the limit of geometrically thin disks. The comparison of ablation with and without continuum absorption shows that accounting for disk optical thickness leads to less than a 50% reduction in ablation rate, implying that ablation rate depends mainly on stellar properties like luminosity. Finally, we discuss the role of "thin-shell mixing" in reducing X-rays from colliding wind binaries. Laminar, adiabatic shocks produce well understood X-ray emission, but the emission from radiatively cooled shocks is more complex due to thin-shell instabilities. The parameter

  19. Status of the Ablative Laser Propulsion Studies

    NASA Technical Reports Server (NTRS)

    Herren, Kenneth A.; Lin, Jun; Cohen, Tinothy; Pakhomov, Andrew V.; Thompson, M. Shane

    2004-01-01

    We present a short review of our laser-propulsion research as well as some of the current results of the Ablative Laser Propulsion (ALP) studies currently underway at the University of Alabama in Huntsville. It has been shown that direct surface ablation of a solid material produces high specific impulse (Isp) at relatively high energy conversion efficiency (20 - 40%). We detail measurements of specific impulse, thrust and coupling coefficients for elemental target materials both with single and with double pulse laser shots. We also present measurements taken using three independent methods for determination of Isp. The three methods produce consistent values from ion time-of-flight technique, impulse measurements and imaging of the expansion front of plasma plume. We present a demonstration of our ALP lightcraft, a small free-flying micro-vehicle that is propelled by ablation. For ALP lightcraft we use a subscale thin shell of nickel replicated over a diamond turned mandrel that produces a highly polished self-focusing, truncated at the focus parabolic mirror. The mass of the lightcraft is 54 mg and it is driven by 100-ps wide, 35-mJ laser pulses at 532 nm wavelength. This is an ongoing research. We also present the latest work on laserdriven micro-thrusters and detail some the near term goals of our program.

  20. Thermal Convection on an Ablating Target

    NASA Astrophysics Data System (ADS)

    Mehmedagic, Igbal; Thangam, Siva

    2015-11-01

    Modeling and analysis of thermal convection of a metallic targets subject to radiative flux is of relevance to various manufacturing processes as well as for the development of protective shields. The present work involves the computational modeling of metallic targets subject to high heat fluxes that are both steady and pulsed. Modeling of the ablation and associated fluid dynamics when metallic surfaces are exposed to high intensity pulsed laser fluence at normal atmospheric conditions is considered. The incident energy from the laser is partly absorbed and partly reflected by the surface during ablation and subsequent vaporization of the convecting melt also participates in the radiative exchange. The energy distribution during the process between the bulk and vapor phase strongly depends on optical and thermodynamic properties of the irradiated material, radiation wavelength, and laser pulse intensity and duration. Computational findings based on effective representation and prediction of the heat transfer, melting and vaporization of the targeting material as well as plume formation and expansion are presented and discussed in the context of various ablation mechanisms, variable thermo-physical and optical properties, plume expansion and surface geometry. Funded in part by U. S. Army ARDEC, Picatinny Arsenal, NJ.