WorldWideScience

Sample records for ablative materials

  1. Moldable cork ablation material

    Science.gov (United States)

    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.

  2. Femtosecond ablation of ultrahard materials

    Science.gov (United States)

    Dumitru, G.; Romano, V.; Weber, H. P.; Sentis, M.; Marine, W.

    Several ultrahard materials and coatings of definite interest for tribological applications were tested with respect to their response when irradiated with fs laser pulses. Results on cemented tungsten carbide and on titanium carbonitride are reported for the first time and compared with outcomes of investigations on diamond and titanium nitride. The experiments were carried out in air, in a regime of 5-8 J/cm2 fluences, using the beam of a commercial Ti:sapphire laser. The changes induced in the surface morphology were analysed with a Nomarski optical microscope, and with SEM and AFM techniques. From the experimental data and from the calculated incident energy density distributions, the damage and ablation threshold values were determined. As expected, the diamond showed the highest threshold, while the cemented tungsten carbide exhibited typical values for metallic surfaces. The ablation rates determined (under the above-mentioned experimental conditions) were in the range 0.1-0.2 μm per pulse for all the materials investigated.

  3. Mechanism of Spatiotemporal Distribution of Laser Ablated Materials

    Institute of Scientific and Technical Information of China (English)

    XU Rong-Qing; CUI Yi-Ping; LU Jian; NI Xiao-Wu

    2009-01-01

    Interaction between subsequent laser and ablated materials in laser processing changes the laser spatiotemporal distribution and has influences on the efficiency and quality of laser processing. The theoretical and experimental researches on transportation behayiour of ablated materials are provided. It is shown that the velocity distribution of ablated materials is determined by ablation mechanism. The transportation behaviour of ablated materials is controlled by diffusion mechanism and light field force during laser pulse duration while it is only determined by diffusion mechanism when the laser pulse terminates. In addition, the spatiotemporal distribution of ablated materials is presented.

  4. Ablation of carbide materials with femtosecond pulses

    Science.gov (United States)

    Dumitru, Gabriel; Romano, Valerio; Weber, Heinz P.; Sentis, Marc; Marine, Wladimir

    2003-01-01

    The response of cemented tungsten carbide and of titanium carbonitride was investigated with respect to damage and ablation properties, under interaction with ultrashort laser pulses. These carbide materials present high microhardness and are of significant interest for tribological applications. The experiments were carried out in air with a commercial Ti:sapphire laser at energy densities on the target up to 6.5 J/cm 2. The irradiated target surfaces were analyzed with optical, SEM and AFM techniques and the damage and ablation threshold values were determined using the measured spot diameters and the calculated incident energy density distributions.

  5. Thermal Ablation Modeling for Silicate Materials

    Science.gov (United States)

    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).

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

    Science.gov (United States)

    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 was

  7. A numerical algorithm for magnetohydrodynamics of ablated materials.

    Science.gov (United States)

    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.

  8. Morphology Characterization of Uranium Particles From Laser Ablated Uranium Materials

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    In the study, metallic uranium and uranium dioxide material were ablated by laser beam in order to simulate the process of forming the uranium particles in pyrochemical process. The morphology characteristic of uranium particles and the surface of

  9. Ablation-cooled material removal with ultrafast bursts of pulses

    Science.gov (United States)

    Kerse, Can; Kalaycıoğlu, Hamit; Elahi, Parviz; Çetin, Barbaros; Kesim, Denizhan K.; Akçaalan, Önder; Yavaş, Seydi; Aşık, Mehmet D.; Öktem, Bülent; Hoogland, Heinar; Holzwarth, Ronald; Ilday, Fatih Ömer

    2016-09-01

    The use of femtosecond laser pulses allows precise and thermal-damage-free removal of material (ablation) with wide-ranging scientific, medical and industrial applications. However, its potential is limited by the low speeds at which material can be removed and the complexity of the associated laser technology. The complexity of the laser design arises from the need to overcome the high pulse energy threshold for efficient ablation. However, the use of more powerful lasers to increase the ablation rate results in unwanted effects such as shielding, saturation and collateral damage from heat accumulation at higher laser powers. Here we circumvent this limitation by exploiting ablation cooling, in analogy to a technique routinely used in aerospace engineering. We apply ultrafast successions (bursts) of laser pulses to ablate the target material before the residual heat deposited by previous pulses diffuses away from the processing region. Proof-of-principle experiments on various substrates demonstrate that extremely high repetition rates, which make ablation cooling possible, reduce the laser pulse energies needed for ablation and increase the efficiency of the removal process by an order of magnitude over previously used laser parameters. We also demonstrate the removal of brain tissue at two cubic millimetres per minute and dentine at three cubic millimetres per minute without any thermal damage to the bulk.

  10. Ultrafast laser ablation of transparent materials

    Science.gov (United States)

    Bauer, Lara; Russ, Simone; Kaiser, Myriam; Kumkar, Malte; Faißt, Birgit; Weber, Rudolf; Graf, Thomas

    2016-03-01

    The present work investigates the influence of the pulse duration and the temporal spacing between pulses on the ablation of aluminosilicate glass by comparing the results obtained with pulse durations of 0.4 ps and 6 ps. We found that surface modifications occur already at fluences below the single pulse ablation threshold and that laser-induced periodic surface structures (LIPSS) emerge as a result of those surface modifications. For 0.4 ps the ablation threshold fluences is lower than for 6 ps. Scanning electron micrographs of LIPSS generated with 0.4 ps exhibit a more periodic and less coarse structure as compared to structures generated with 6 ps. Furthermore we report on the influence of temporal spacing between the pulses on the occurrence of LIPSS and the impact on the quality of the cutting edge. Keywords: LIPSS,

  11. Interfacial Design of Composite Ablative Materials Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business Innovation Research (SBIR) project proposes the development of a computational software package to provide NASA with advanced materials...

  12. Modeling of multi-burst mode pico-second laser ablation for improved material removal rate

    Science.gov (United States)

    Hu, Wenqian; Shin, Yung C.; King, Galen

    2010-02-01

    This paper deals with the unique phenomena occurring during the multi-burst mode picosecond (ps) laser ablation of metals through modeling and experimental studies. The two-temperature model (TTM) is used and expanded to calculate the ablation depth in the multi-burst mode. A nonlinear increment of ablation volume is found during the multi-burst laser ablation. The deactivation of ablated material and the application of temperature-dependent electron-phonon coupling are demonstrated to be important to provide reliable results. The simulation results based on this expanded laser ablation model are experimentally validated. A significant increase of ablation rate is found in the multi-burst mode, compared with the single-pulse mode under the same total fluence. This numerical model provides a physical perspective into the energy transport process during multi-burst laser ablation and can be used to study the pulse-to-pulse separation time effect on the ablation rate.

  13. Modeling of multi-burst mode pico-second laser ablation for improved material removal rate

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Wenqian; Shin, Yung C.; King, Galen [Purdue University, Center for Laser-based Manufacturing, School of Mechanical Engineering, West Lafayette, IN (United States)

    2010-02-15

    This paper deals with the unique phenomena occurring during the multi-burst mode picosecond (ps) laser ablation of metals through modeling and experimental studies. The two-temperature model (TTM) is used and expanded to calculate the ablation depth in the multi-burst mode. A nonlinear increment of ablation volume is found during the multi-burst laser ablation. The deactivation of ablated material and the application of temperature-dependent electron-phonon coupling are demonstrated to be important to provide reliable results. The simulation results based on this expanded laser ablation model are experimentally validated. A significant increase of ablation rate is found in the multi-burst mode, compared with the single-pulse mode under the same total fluence. This numerical model provides a physical perspective into the energy transport process during multi-burst laser ablation and can be used to study the pulse-to-pulse separation time effect on the ablation rate. (orig.)

  14. The ablation of graphitic materials in the sublimation regime.

    Science.gov (United States)

    Lundell, J. H.; Dickey, R. R.

    1972-01-01

    A large variety of graphitic materials have been tested in an arc heated air stream at a surface pressure of 4.3 atm and a nominal surface temperature of 3925 K. Included were commercial and developmental grades of artificial graphites, both two and three dimensional carbon-carbon composites, composites seeded with refractory compounds, and several special materials such as pyrolytic graphite, mesophase graphite, glassy carbon, and natural graphite. ATJ graphite was used as a control material. Except for the seeded materials which had poor performance, the mass loss rate for all the man-made graphitic materials fell within the range of 17 per cent less to 30 per cent more than the rate for ATJ. Thus it is concluded that wide variations in constituents, processing, fabrication and structure have relatively little effect on the ablation performance of graphitic materials, at least under the conditions of the present tests. Particulate mass loss was observed for all the materials tested and is the dominant mechanism for mass removal at the present test conditions. It is suggested that this mechanism results from physical failure, primarily by compressive thermal stress.

  15. Analysis of fabric materials cut using ultraviolet laser ablation

    Science.gov (United States)

    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.

  16. Ablation of various materials with intense XUV radiation

    Energy Technology Data Exchange (ETDEWEB)

    Juha, Libor E-mail: juha@fzu.cz; Krasa, Josef; Cejnarova, Andrea; Chvostova, Dagmar; Vorlicek, V.; Krzywinski, Jacek; Sobierajski, Ryszard; Andrejczuk, Andrzej; Jurek, Marek; Klinger, Dorota; Fiedorowicz, Henryk; Bartnik, Andrzej; Pfeifer, Miroslav; Kubat, Pavel; Pina, Ladislav; Kravarik, Jozef; Kubes, Pavel; Bakshaev, Y.L.; Korolev, V.D.; Chernenko, A.S.; Ivanov, M.I.; Scholz, Marek; Ryc, Leszek; Feldhaus, Josef; Ullschmied, Jiri; Boody, F.P

    2003-07-11

    Ablation behavior of organic polymer (polymethylmethacrylate) and elemental solid (silicon) irradiated by single pulses of XUV radiation emitted from Z-pinch, plasma-focus, and laser-produced plasmas was investigated. The ablation characteristics measured for these plasma-based sources will be compared with those obtained for irradiation of samples with XUV radiation generated by a free-electron laser.

  17. Femtosecond laser ablation profile near an interface: Analysis based on the correlation with superficial properties of individual materials

    Energy Technology Data Exchange (ETDEWEB)

    Nicolodelli, Gustavo, E-mail: nicolodelli@ursa.ifsc.usp.br [Instituto de Fisica de Sao Carlos, University of Sao Paulo, Grupo de Optica, Av. Trabalhador Sancarlense 400, P.O. Box 369, CEP 13560-970, Sao Carlos, SP (Brazil); Kurachi, Cristina; Bagnato, Vanderlei Salvador [Instituto de Fisica de Sao Carlos, University of Sao Paulo, Grupo de Optica, Av. Trabalhador Sancarlense 400, P.O. Box 369, CEP 13560-970, Sao Carlos, SP (Brazil)

    2011-01-15

    Femtosecond laser ablation of materials is turning to be an important tool for micromachining as well as for selective removal of biological tissues. In a great number of applications, laser ablation has to process through interfaces separating media of different properties. The investigation of the ablation behavior within materials and passing through interfaces is the main aim of this study. Especially, the analysis of the discontinuity in the ablation profile close to interfaces between distinct materials can reveal some of the phenomena involved in the formation of an ablated microcavity geometry. We have used a method that correlates the ablation cross sectional area with the local laser intensity. The effective intensity ablation properties were obtained from surface ablation data of distinct materials. The application of this method allows the prediction of the occurrence of a size discontinuity in the ablation geometry at the interface of distinct media, a fact which becomes important when planning applications in different media.

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

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Lechuga, M.; Siegel, J., E-mail: j.siegel@io.cfmac.csic.es; Hernandez-Rueda, J.; Solis, J. [Laser Processing Group, Instituto de Optica, Serrano 121, 28006 Madrid (Spain)

    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.

  19. Analysis and removal of ITER relevant materials and deposits by laser ablation

    Science.gov (United States)

    Xiao, Qingmei; Huber, Alexander; Philipps, Volker; Sergienko, Gennady; Gierse, Niels; Mertens, Philippe; Hai, Ran; Ding, Hongbin

    2014-12-01

    The analysis of the deposition of eroded wall material on the plasma-facing materials in fusion devices is one of the crucial issues to maintain the plasma performance and to fulfill safety requirements with respect to tritium retention by co-deposition. Laser ablation with minimal damage to the plasma facing material is a promising method for in situ monitoring and removal of the deposition, especially for plasma-shadowed areas which are difficult to reach by other cleaning methods like plasma discharge. It requires the information of ablation process and the ablation threshold for quantitative analysis and effective removal of the different deposits. This paper presents systemic laboratory experimental analysis of the behavior of the ITER relevant materials, graphite, tungsten, aluminum (as a substitution of beryllium) and mixed deposits ablated by a Nd:YAG laser (1064 nm) with different energy densities (1-27 J/cm2, power density 0.3-3.9 GW/cm2). The mixed deposits consisted of W-Al-C layer were deposited on W substrate by magnetron sputtering and arc plasma deposition. The aim was to select the proper parameters for the quantitative analysis and for laser removal of the deposits by investigating the ablation efficiency and ablation threshold for the bulk materials and deposits. The comparison of the ablation and saturation energy thresholds for pure and mixed materials shows that the ablation threshold of the mixed layer depends on the concentration of the components. We propose laser induced breakdown spectroscopy for determination of the elemental composition of deposits and then we select the laser parameters for the layer removal. Comparison of quantitative analysis results from laboratory to that from TEXTOR shows reasonable agreements. The dependence of the spectra on plasma parameters and ambient gas pressure is investigated.

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz, Rocio; Quintana, Iban; Etxarri, Jon [Manufacturing Processes Department, Fundacion TEKNIKER, Av. Otaola 20, 20600, Eibar, Guipuzcoa (Spain); Lejardi, Ainhoa; Sarasua, Jose-Ramon [Department of Mining and Metallurgy Engineering and Materials Science, School of Engineering, University of the Basque Country (EHU-UPV), Alameda de Urquijo s/n, 48013 Bilbao (Spain)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  4. Evaluation of Ablation rate by the change of Sacrificial Material for PECS in EU-APR

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, Do Hyun; Kim, Yong Soo; Lee, Keun Sung [KHNP-CRI, Daejeon (Korea, Republic of)

    2015-05-15

    EU-APR, modified and improved from its original design of APR1400, has been developed to comply with European Utility Requirements (EUR) and nuclear design requirements of the European countries. In EU-APR, Severe Accident Mitigation Systems are dedicated to providing an independent defense line from that of Engineered Safety Feature (ESF) and Diverse Safety Feature (DSF). They consist of Emergency Reactor Depressurization System (ERDS), Passive Ex-vessel corium retaining and Cooling System (PECS), Severe Accident Containment Spray System (SACSS), Hydrogen Mitigation System (HMS) and Containment Filtered Vent System (CFVS). The PECS, so called core catcher, was introduced to prevent the Molten Core Concrete Interaction (MCCI) after Reactor Vessel (RV) failure. The PECS has experienced a lot of changes from its original design. Recently, the most significant change was that as a SM, limestone concrete is installed on PECS's body wall instead of previous sacrificial material rich in Fe{sub 2}O{sub 3}. The main reason of this design change is to overcome the issue that the sacrificial material is ablated rather too fast when reacting with corium that contains a large fraction of Zr metal. Other changes in the geometry of PECS's wall and downcomer design are considered as minor ones. In this paper, the comparison of ablation rates between previous SM and limestone concrete is carried out using MAAP5 code with respective MCCI model according to the material. In this paper, major improvements of MAAP5 model for PECS in EU-APR are presented and the evaluation of ablation rate for the previous SM model and the new LC model is carried out by means of ablation depths with LBLOCA sequence. Two models have respective unique ablation process. The ablation of LC model proceeds at a constant rate regardless of water while the ablation of SM model proceeds at a faster rate before the arrival of cooling water for corium and SM mixture. The change of sacrificial material

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

    Science.gov (United States)

    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.

  6. Material morphological characteristics in laser ablation of alpha case from titanium alloy

    Science.gov (United States)

    Yue, Liyang; Wang, Zengbo; Li, Lin

    2012-08-01

    Alpha case (an oxygen enriched alloy layer) is commonly formed in forged titanium alloys during the manufacturing process and it reduces the service life of the materials. This layer is normally removed mechanically or chemically. This paper reports the feasibility and characteristics of using a short pulsed laser to remove oxygen-enriched alpha case layer from a titanium alloy (Ti6Al4V) substrate. The material removal rate, i.e., ablation rate, and ablation threshold of the alpha case titanium were experimentally determined, and compared with those for the removal of bulk Ti6Al4V. Surface morphologies of laser processed alpha case titanium layer, especially that of cracks at different ablated depths, were carefully examined, and also compared with those for Ti6Al4V. It has been shown that in the alpha case layer, laser ablation has always resulted in crack formation while for laser ablation of alpha case free Ti6Al4V layers, cracking was not present. In addition, the surface is rougher within the alpha case layer and becomes smoother (Ra - 110 nm) once the substrate Ti-alloy is reached. The work has demonstrated that laser is a feasible processing tool for removing alpha case titanium, and could also be used for the rapid detection of the presence of alpha case titanium on Ti6Al4V surfaces in aerospace applications.

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

    Science.gov (United States)

    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.

  8. On single-photon ultraviolet ablation of polymeric materials

    Science.gov (United States)

    Cain, Stephen R.; Burns, F. C.; Otis, C. E.

    1992-05-01

    The nature of uv ablation of organic polymers is discussed in terms of a pseudo-zeroth-order rate law of the form dx/dt = k0e-(Eact/kT), where Eact is assumed to be the strength of the weakest bonds in the polymer and T is the local temperature increase from the incident laser pulse. Equations derived from previous models that assumed nonthermal photodecomposition were duplicated from this photothermal model. Even for the simple case of single-photon absorption, nonideal behavior is affected by radiationless decay, pulse length, and thermal diffusion. These effects were probed. Results indicated that thermal diffusion may have a significant effect on the threshold fluence and to some degree on the shape of the etch depth versus fluence curve. Absorption dynamics (saturation and radiationless decay) appear to be the dominant factor in determining the functional dependence of etch depth on fluence. As a result of competition between absorption saturation and radiationless decay, the penetration depth is intensity dependent. High fluence as well as short temporal pulses (subnanosecond) penetrate more deeply into the polymer than predicted by simple Beer's law absorption. The apparent existence of an optimum pulse length, for a given absorbing system, is another result of the absorption dynamics.

  9. Wall ablation of heated compound-materials into non-equilibrium discharge plasmas

    Science.gov (United States)

    Wang, Weizong; Kong, Linghan; Geng, Jinyue; Wei, Fuzhi; Xia, Guangqing

    2017-02-01

    The discharge properties of the plasma bulk flow near the surface of heated compound-materials strongly affects the kinetic layer parameters modeled and manifested in the Knudsen layer. This paper extends the widely used two-layer kinetic ablation model to the ablation controlled non-equilibrium discharge due to the fact that the local thermodynamic equilibrium (LTE) approximation is often violated as a result of the interaction between the plasma and solid walls. Modifications to the governing set of equations, to account for this effect, are derived and presented by assuming that the temperature of the electrons deviates from that of the heavy particles. The ablation characteristics of one typical material, polytetrafluoroethylene (PTFE) are calculated with this improved model. The internal degrees of freedom as well as the average particle mass and specific heat ratio of the polyatomic vapor, which strongly depends on the temperature, pressure and plasma non-equilibrium degree and plays a crucial role in the accurate determination of the ablation behavior by this model, are also taken into account. Our assessment showed the significance of including such modifications related to the non-equilibrium effect in the study of vaporization of heated compound materials in ablation controlled arcs. Additionally, a two-temperature magneto-hydrodynamic (MHD) model accounting for the thermal non-equilibrium occurring near the wall surface is developed and applied into an ablation-dominated discharge for an electro-thermal chemical launch device. Special attention is paid to the interaction between the non-equilibrium plasma and the solid propellant surface. Both the mass exchange process caused by the wall ablation and plasma species deposition as well as the associated momentum and energy exchange processes are taken into account. A detailed comparison of the results of the non-equilibrium model with those of an equilibrium model is presented. The non-equilibrium results

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

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

    2016-06-09

    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

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

    Science.gov (United States)

    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

  13. Numerical simulation of laser ablation for photovoltaic materials

    Science.gov (United States)

    Stein, P.; García, O.; Morales, M.; Huber, H. P.; Molpeceres, C.

    2012-09-01

    The objective of this work is to help understanding the impacts of short laser pulses on materials of interest for photovoltaic applications, namely aluminum and silver. One of the traditional advantages of using shorter laser pulses has been the attempt to reduce the characteristic heat affected zone generated in the interaction process, however the complex physical problem involved limitates the integration of simplified physical models in standard tools for numerical simulation. Here the interaction between short laser pulses and matter is modeled in the commercial finite-element software Abaqus. To describe ps and fs laser pulses properly, the two-temperature model (TTM) is applied considering electrons and lattice as different thermal transport subsystems. The Material has been modeled as two equally sized and meshed but geometrically independent parts, representing each the electron and the lattice domain. That means, both domains match in number and position of the respective elements as well as in their shape and their size. The laser pulse only affects the electron domain so that the lattice domain remains at ambient temperature. The thermal connection is only given by the electron-phonon coupling, depending on the temperature difference between both domains. It will be shown, that melting and heat affected zones getting smaller with decreasing pulse durations.

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

    Science.gov (United States)

    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.

  15. Multiscale Modeling of Ablation and Pyrolysis in PICA-Like materials

    Science.gov (United States)

    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.

  16. An Experimental Research to Study the Microwaves Transmission Characteristics of Ablating Material in Arc-Heated Plasma Flow

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In this paper, an experimental research the effect of ablating material on the reflection and the transmission of microwaves in arc-heated plasma flow is presented by using the C band microwave measuring system. The results show that the ablating material with accidented surface and its high temperature have remarkably affected the reflection and the transmission of microwaves. The experiment proves that the system has outstanding precision and reliability.

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

    Science.gov (United States)

    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.

  18. Selective ablation of photovoltaic materials with UV laser sources for monolithic interconnection of devices based on a-Si:H

    Energy Technology Data Exchange (ETDEWEB)

    Molpeceres, C. [Centro Laser UPM, Univ. Politecnica de Madrid, Crta. de Valencia Km 7.3, 28031 Madrid (Spain)], E-mail: carlos.molpeceres@upm.es; Lauzurica, S.; Garcia-Ballesteros, J.J.; Morales, M.; Guadano, G.; Ocana, J.L. [Centro Laser UPM, Univ. Politecnica de Madrid, Crta. de Valencia Km 7.3, 28031 Madrid (Spain); Fernandez, S.; Gandia, J.J. [Dept. de Energias Renovables, Energia Solar Fotovoltaica, CIEMAT, Avda, Complutense 22, 28040 Madrid (Spain); Villar, F.; Nos, O.; Bertomeu, J. [CeRMAE Dept. Fisica Aplicada i Optica, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona (Spain)

    2009-03-15

    Lasers are essential tools for cell isolation and monolithic interconnection in thin-film-silicon photovoltaic technologies. Laser ablation of transparent conductive oxides (TCOs), amorphous silicon structures and back contact removal are standard processes in industry for monolithic device interconnection. However, material ablation with minimum debris and small heat affected zone is one of the main difficulty is to achieve, to reduce costs and to improve device efficiency. In this paper we present recent results in laser ablation of photovoltaic materials using excimer and UV wavelengths of diode-pumped solid-state (DPSS) laser sources. We discuss results concerning UV ablation of different TCO and thin-film silicon (a-Si:H and nc-Si:H), focussing our study on ablation threshold measurements and process-quality assessment using advanced optical microscopy techniques. In that way we show the advantages of using UV wavelengths for minimizing the characteristic material thermal affection of laser irradiation in the ns regime at higher wavelengths. Additionally we include preliminary results of selective ablation of film on film structures irradiating from the film side (direct writing configuration) including the problem of selective ablation of ZnO films on a-Si:H layers. In that way we demonstrate the potential use of UV wavelengths of fully commercial laser sources as an alternative to standard backscribing process in device fabrication.

  19. Degradation of carbon-based materials under ablative conditions produced by a high enthalpy plasma jet

    Directory of Open Access Journals (Sweden)

    Gilberto Petraconi

    2010-04-01

    Full Text Available A stationary experiment was performed to study the degradation of carbon-based materials by immersion in a plasma jet. In the experiment, graphite and C/C composite were chosen as the target materials, and the reactive plasma jet was generated by an air plasma torch. For macroscopic study of the material degradation, the sample’s mass losses were measured as function of the exposure time under various temperatures on the sample surface. A microscopic analysis was then carried out for the study of microscopic aspects of the erosion of material surface. These experiments showed that the mass loss per unit area is approximately proportional to the exposure time and strongly depends on the temperature of the material surface. The mass erosion rate of graphite was appreciably higher than the C/C composite. The ablation rate in the carbon matrix region in C/C composite was also noticeably higher than that in the fiber region. In addition, the latter varied according to the orientation of fibers relatively to the flow direction. These tests indicated an excellent ablation resistance of the C/C composite, thus being a reliable material for rocket nozzles and heat shielding elements of the protection systems of hypersonic apparatuses from aerodynamic heating.

  20. Effect of High Z material on the performance of an air-breathing laser ablation thruster

    Science.gov (United States)

    Shimamura, Kohei; Kiyono, Inoru; Yokota, Ippei; Ozaki, Naoto; Yokota, Shigeru

    2016-09-01

    A Laser propulsion, such as a Lightcraft, is a candidate for the low cost transportation system between the ground to space instead of the chemical rocket. Using the shock wave induced by focusing laser beam on the ablator in air, the huge fuel is unnecessary to generate the thrust. In this study, the high-Z material was doped into the polystyrene to emphasize the ionization effect in air. We evaluate the intensity of the bremsstrahlung radiation, the plasma parameter, and the thrust performance.

  1. Influence of an Angular Hatching Exposure Strategy on the Surface Roughness During Picosecond Laser Ablation of Hard Materials

    Science.gov (United States)

    Daniel, Christian; Manderla, Jannik; Hallmann, Sina; Emmelmann, Claus

    Innovative chip breakers for cutting tools made of very hard materials require laser ablation and demand a high quality regarding the manufactured surface. When processing materials such as polycrystalline cubic boron-nitride or tungsten carbide the surface roughness by laser ablation reaches Sa = 1,0-2,9 μm compared to Sa = 0,42 μm achieved by grinding. Therefore in the presented research the influence of the hatching exposure strategy on surface roughness during picosecond laser ablation of tungsten carbide is examined. The areal, layerwise ablation process is separated into its elements which are represented by intersection zones between single and multiple laser vectors. Thus two mechanisms of roughness formation are identified and described by model functions. Further the mechanisms are transferred to areal ablation in which surface roughness decreases due to improved hatching angles compared to a commonly used one of φ= 0°/90°. With this approach the roughness is reduced by approximately factor 2,0-3,5 to Sa = 0,82 μm. In conclusion guidelines are derived which present favorable settings for high quality laser ablation processes.

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

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, Nozomi, E-mail: tanaka-n@ile.osaka-u.ac.jp; Masuda, Masaya; Deguchi, Ryo; Murakami, Masakatsu; Fujioka, Shinsuke; Yogo, Akifumi; Nishimura, Hiroaki [Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871 (Japan); Sunahara, Atsushi [Institute for Laser Technology, 2-6 Yamadaoka, Suita, Osaka 565-0871 (Japan)

    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.

  3. Multidisciplinary approach to materials selection for bipropellant thrusters using ablative and radiative cooling

    Indian Academy of Sciences (India)

    A Adami; M Mortazavi; M Nosratollahi

    2016-01-01

    Reduction of costs is a main consideration in every space mission, and propulsion system is an important subsystem of those missions where orbital maneuvers are considered. Lighter propulsions with higher performance are necessary to reduce the mission costs. Bipropellant propulsions have been widely used in launch vehicles and upper-stages as well as deorbit modules because of better performances in comparison with other propulsion systems. Unfortunately heat transfer and thermal control limit bipropellant propulsion performance and maximum performance cannot be achieved. Well-known cooling methods such as regenerative and film cooling increase the cost using extra equipment and high temperature materials. In this paper, a new approach for cooling is presented based on combined ablative and radiative cooling. Governing equations are derived for two or three layers of thermal protection system (TPS) to optimize the TPS mass. The first layer is used as an ablative layer to control the temperature where the second and third layers are used as an insulator to control the heat fluxes. Proposed cooling method has been applied for two real bipropellant thrusters. According to the results, the presented algorithm can suitably predict the heat fluxes and satisfy the wall temperature constraint. Then, the algorithm has been used to minimize the wall temperatures as low as possible and replace high temperature materials (platinum alloy) with common materials (composite or steel). It is shown that selection of TPS materials affects the TPS mass and Isp simultaneously, but conversely. Best solution should be derived by trading off between structure temperature (cost), Isp (performance), and TPS thicknesses (geometry). Multidisciplinary approach to TPS and structure material selection of a bipropellant thruster is presented for a case study. It has been shown that mass and performance penalties of using TPS are acceptable, considering the advantages of using steel alloy instead

  4. Hydrodynamic Mixing of Ablator Material into the Compressed Fuel and Hot Spot of Direct-Drive DT Cryogenic Implosions

    Science.gov (United States)

    Regan, S. P.; Goncharov, V. N.; Epstein, R.; Betti, R.; Bonino, M. J.; Cao, D.; Collins, T. J. B.; Campbell, E. M.; Forrest, C. J.; Glebov, V. Yu.; Harding, D. R.; Marozas, J. A.; Marshall, F. J.; McKenty, P. W.; Sangster, T. C.; Stoeckl, C.; Luo, R. W.; Schoff, M. E.; Farrell, M.

    2016-10-01

    Hydrodynamic mixing of ablator material into the compressed fuel and hot spot of direct-drive DT cryogenic implosions is diagnosed using time-integrated, spatially resolved xray spectroscopy. The laser drive ablates most of the 8- μm-thick CH ablator, which is doped with trace amounts of Ge ( 0.5 at.) and surrounds the cryogenic DT layer. A small fraction of the ablator material is mixed into the compressed shell and the hot spot by the ablation-front Rayleigh-Taylor hydrodynamic instability seeded by laser imprint, the target mounting stalk, and surface debris. The amount of mix mass inferred from spectroscopic analysis of the Ge K-shell emission will be presented. This material is based upon work supported by the Department Of Energy National Nuclear Security Administration under Award Number DE-NA0001944. Part of this work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

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

    Science.gov (United States)

    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.

  6. Determination of additives in PVC material by UV laser ablation inductively coupled plasma atomic emission spectrometry

    Science.gov (United States)

    Hemmerlin, M.; Mermet, J. M.; Bertucci, M.; Zydowicz, P.

    1997-04-01

    UV laser ablation inductively coupled plasma atomic emission spectrometry (LA-ICP-AES) has been applied to the direct determination of additives in solid poly(vinyl chloride) materials. A Nd:YAG laser, operating at its fourth harmonic (266 nm), was used with a beam masking device, in the most reproducible conditions, to introduce solid particles into the plasma torch of a simultaneous ICP-AES system. Emphasis was placed on both precision and accuracy in the analysis of PVC materials by LA-ICP-AES. A series of six in-house PVC reference materials was prepared by incorporating several additives in increasing concentrations. Three alternative methods were evaluated to certify the amount of incorporated elements: ICP-AES with sample dissolution, NAA and XRF. Satisfactory results and good agreement were obtained for seven elements (Al, Ca, Cd, Mg, Sb, Sn and Ti) among the ten incorporated. Sample homogeneity appeared to be satisfactory, and calibration graphs obtained by LA-ICP-AES for several elements are presented. Finally, the performance of the technique in terms of repeatability (1.6-5%), reproducibility (2-5%), and limits of detection was investigated.

  7. Composite material based on an ablative phenolic resin and carbon fibers

    Directory of Open Access Journals (Sweden)

    DIMKO DIMESKI

    2009-04-01

    Full Text Available In this study, a technological procedure for the production of a molding compound based on short carbon fibers and an ablative phenol–formaldehyde resin for high temperature application was optimized. The starting raw materials were characterized and molding compounds with different fiber/matrix ratios and different fiber lengths were obtained. From the different laboratory samples, molded parts were made by thermocompression. The basic mechanical and thermal properties of the composites were determined. From the obtained results, the optimal fiber/matrix ratio was determined for a production of molding compound for high temperature application. The molding process of the composite material was optimized and all the parameters for good mechanical properties and high thermal stability of the composite were obtained. Optimization of the composite molding process was performed by the application of a numerical method for a planned experiment, i.e., a full three-factorial experimental design with variance of all three parameters (fiber length, temperature and time of the press cycle on two levels. The obtained mechanical properties (flexural strength: 247 MPa, modulus: 27.6 GPa, impact resistance: 110 (for test moldings 10 mm´10 mm and 91 kJ/m2 (for test moldings 15 mm´15 mm justified the application of this composite material in the automotive, leisure, military and other industries where high temperature resistance and high mechanical strength is required.

  8. Standard Test Method for Oxyacetylene Ablation Testing of Thermal Insulation Materials

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2008-01-01

    1.1 This test method covers the screening of ablative materials to determine the relative thermal insulation effectiveness when tested as a flat panel in an environment of a steady flow of hot gas provided by an oxyacetylene burner. 1.2 This test method should be used to measure and describe the properties of materials, products, or assemblies in response to heat and flame under controlled laboratory conditions and should not be used to describe or appraise the fire hazard of materials, products, or assemblies under actual fire conditions. However, results of this test method may be used as elements of a fire risk assessment which takes into account all of the factors which are pertinent to an assessment of the fire hazard of a particular end use. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limi...

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, Marcos S. [Departamento de Química, Universidade Federal de São Carlos, Rod. Washington Luís, km 235, 13565-905 São Carlos, SP (Brazil); Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Av. Centenário 303, 13416-000 Piracicaba, SP (Brazil); Schenk, Emily R. [Department of Chemistry and Biochemistry, Florida International University, Miami, FL (United States); International Forensic Research Institute, Florida International University, Miami, FL (United States); Santos, Dário [Departamento de Ciências Exatas e da Terra, Universidade Federal de São Paulo, Rua Professor Arthur Riedel 275, Diadema, SP (Brazil); Krug, Francisco José [Centro de Energia Nuclear na Agricultura, Universidade de São Paulo, Av. Centenário 303, 13416-000 Piracicaba, SP (Brazil); Almirall, José R., E-mail: almirall@fiu.edu [Department of Chemistry and Biochemistry, Florida International University, Miami, FL (United States); International Forensic Research Institute, Florida International University, Miami, FL (United States)

    2014-04-01

    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{sup −1} for Zn to as high as 94 mg kg{sup −1} for K but were generally below 6 mg kg{sup −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. - Highlights: • An evaluation of LA-ICP-OES for the direct analysis of pelleted plant material is reported. • Orange citrus, soy and sugarcane plants were pressed into pellets and sampled directly. • The element menu consisted of Ca, Mg, P, K, Fe, Mn, Zn and B. • LODs for the method ranged from 0.1 mg kg{sup −1} for Zn to 94 mg kg{sup −1} for K. • The precision ranged from 4% RSD for Mn to 17% RSD for Zn (∼ 6.5% RSD average)

  11. Extinction characterization of soot produced by laser ablating carbon fiber composite materials in air flow

    Science.gov (United States)

    Liu, Weiping; Ma, Zhiliang; Zhang, Zhenrong; Zhou, Menglian; Wei, Chenghua

    2015-05-01

    In order to research the dynamic process of energy coupling between an incident laser and a carbon fiber/epoxy resin composite material, an extinction characterization analysis of soot, which is produced by laser ablating and located in an air flow that is tangential to the surface of the composite material, is carried out. By the theory analyses, a relationship of mass extinction coefficient and extinction cross section of the soot is derived. It is obtained that the mass extinction coefficients of soot aggregates are the same as those of the primary particles when they contain only a few primary particles. This conclusion is significant when the soot is located in an air flow field, where the generations of the big soot aggregates are suppressed. A verification experiment is designed. The experiment employs Laser Induced Incandescence technology and laser extinction method for the soot synchronization diagnosis. It can derive a temporal curve of the mass extinction coefficient from the soot concentration and laser transmittance. The experiment results show that the mass extinction coefficient becomes smaller when the air flow velocity is higher. The reason is due to the decrease of the scatter effects of the soot particles. The experiment results agree with the theory analysis conclusion.

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

    Science.gov (United States)

    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.

  13. Diamond nanospherulite: A novel material produced at carbon-water interface by pulsed-laser ablation

    Institute of Scientific and Technical Information of China (English)

    王育煌; 黄群健; 陈忠; 黄荣彬; 郑兰荪

    1997-01-01

    Formation of carbon nanoparticles with perfectly spherical.shape and diamond structure (diamond nanospherulite) by laser-ablating a variety of carbon samples in water is reported for the first time The studies reveal that molten carbon nanoparticles generated by laser ablation are quenched directly by water and end up as diamond nanospherulites,possibly due to the high pressure arising from surface tension and the high stability resulting from termination of dangling bonds with hydrogen atoms.

  14. Demonstration of the improved rocket efficiency in direct-drive implosions using different ablator materials.

    Science.gov (United States)

    Michel, D T; Goncharov, V N; Igumenshchev, I V; Epstein, R; Froula, D H

    2013-12-13

    The success of direct-drive implosions depends critically on the ability to create high ablation pressures (∼100  Mbar) and accelerating the imploding shell to ignition-relevant velocities (>3.7×10(7 ) cm/s) using direct laser illumination. This Letter reports on an experimental study of the conversion of absorbed laser energy into kinetic energy of the shell (rocket efficiency) where different ablators were used to vary the ratio of the atomic number to the atomic mass. The implosion velocity of Be shells is increased by 20% compared to C and CH shells in direct-drive implosions when a constant initial target mass is maintained. These measurements are consistent with the predicted increase in the rocket efficiency of 28% for Be and 5% for C compared to a CH ablator.

  15. Coupled molecular dynamics-Monte Carlo model to study the role of chemical processes during laser ablation of polymeric materials.

    Science.gov (United States)

    Prasad, Manish; Conforti, Patrick F; Garrison, Barbara J

    2007-08-28

    The coarse grained chemical reaction model is enhanced to build a molecular dynamics (MD) simulation framework with an embedded Monte Carlo (MC) based reaction scheme. The MC scheme utilizes predetermined reaction chemistry, energetics, and rate kinetics of materials to incorporate chemical reactions occurring in a substrate into the MD simulation. The kinetics information is utilized to set the probabilities for the types of reactions to perform based on radical survival times and reaction rates. Implementing a reaction involves changing the reactants species types which alters their interaction potentials and thus produces the required energy change. We discuss the application of this method to study the initiation of ultraviolet laser ablation in poly(methyl methacrylate). The use of this scheme enables the modeling of all possible photoexcitation pathways in the polymer. It also permits a direct study of the role of thermal, mechanical, and chemical processes that can set off ablation. We demonstrate that the role of laser induced heating, thermomechanical stresses, pressure wave formation and relaxation, and thermochemical decomposition of the polymer substrate can be investigated directly by suitably choosing the potential energy and chemical reaction energy landscape. The results highlight the usefulness of such a modeling approach by showing that various processes in polymer ablation are intricately linked leading to the transformation of the substrate and its ejection. The method, in principle, can be utilized to study systems where chemical reactions are expected to play a dominant role or interact strongly with other physical processes.

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

    Science.gov (United States)

    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.

  17. Development of a prediction equation for depth, aspect ratio, and trench roughness pertaining to excimer laser ablation of polymer materials

    Science.gov (United States)

    McGinty, Sean; O'Connor, Gerard M.; Glynn, Thomas J.

    2005-06-01

    Excimer based laser ablation of micro-fluidic circuits for micro-total analysis systems (μTAS) is an alternative to more expensive techniques of LIGA or micro-moulding. In the interests of developing a rapid prototyping method for direct writing of micro-fluidic circuits in polymer materials the ablation process was characterised using Design of Experiment techniques and a robust full factorial model was developed. Input factors of pulse energy, repetition rate, scan speed and number of passes were considered. Output responses of trench bottom width, sidewall angle, trench depth and trench roughness were measured. From this a prediction equation was created to forecast the output responses prior to machining and to allow the development of a process prior to machining. The accuracy of the prediction equation is discussed for four materials; Polystyrene, Polycarbonate, Non-CQ grade PMMA and CQ grade PMMA. For the four materials studied the response of Polystyrene and Polycarbonate were similar while the two grades of PMMA behave differently.

  18. Extreme ultraviolet interferometry of laser plasma material between the critical and ablation surfaces

    Science.gov (United States)

    Gartside, L. M. R.; Tallents, G. J.; Rossall, A. K.; Wagenaars, E.; Whittaker, D. S.; Kozlová, M.; Nejdl, J.; Sawicka, M.; Polan, J.; Kalal, M.; Rus, B.

    2011-06-01

    Interferometric probing using an extreme ultraviolet (EUV) laser has measured both transmission and phase information through laser-irradiated plastic (parylene-N C 8H 8) targets (thickness 350 nm). Unusually, the probe beam is incident longitudinally in approximately the same direction as the incident optical laser. Agreement of the experimental interferometry results has been obtained with two-dimensional radiation hydrodynamic code (h2d) simulations of EUV (21.2 nm) probe transmissions and phase shifts. We show that the transmission of the EUV probe beam provides a measure of the rate of target ablation, as ablated plasma becomes close to transparent when the photon energy is less than the ionization energy of the predominate ion species. Here C 3+ ions with ionization energy 64.5 eV are transparent, while lower carbon ionization stages, present in the unablated target and close to the ablation surface, absorb the 58.5 eV photons. Similarly, we show that refractive indices η below the solid parylene-N ( ηsolid = 0.946) and expected plasma values are produced in the warm dense plasma created by laser irradiation due to bound-free absorption in C +.

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

    Science.gov (United States)

    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.

  20. [Progress in the application of laser ablation ICP-MS to surface microanalysis in material science].

    Science.gov (United States)

    Zhang, Yong; Jia, Yun-hai; Chen, Ji-wen; Shen, Xue-jing; Liu, Ying; Zhao, Leiz; Li, Dong-ling; Hang, Peng-cheng; Zhao, Zhen; Fan, Wan-lun; Wang, Hai-zhou

    2014-08-01

    In the present paper, apparatus and theory of surface analysis is introduced, and the progress in the application of laser ablation ICP-MS to microanalysis in ferrous, nonferrous and semiconductor field is reviewed in detail. Compared with traditional surface analytical tools, such as SEM/EDS (scanning electron microscopy/energy dispersive spectrum), EPMA (electron probe microanalysis analysis), AES (auger energy spectrum), etc. the advantage is little or no sample preparation, adjustable spatial resolution according to analytical demand, multi-element analysis and high sensitivity. It is now a powerful complementary method to traditional surface analytical tool. With the development of LA-ICP-MS technology maturing, more and more analytical workers will use this powerful tool in the future, and LA-ICP-MS will be a super star in elemental analysis field just like LIBS (Laser-induced breakdown spectroscopy).

  1. Determination of Physical Properties of Carbon Materials by Results of Ablative Experiments Con-ducted in the Jets of Gas Dynamic Units

    Directory of Open Access Journals (Sweden)

    V. V. Gorsky

    2015-01-01

    Full Text Available The process of hypersonic vehicles’ movement in the dense layers of the atmosphere is accompanied by the considerable combustion of heat shield, which effects on the aerodynamic, mass-inertial and centering characteristics of the product.For correct calculation of model's movement parameters it is necessary:* Using the theoretical and computation methods for determining ablative characteristics of heat-protective materials;* Taking into account all the basic physical and chemical processes, involved in their ablation, using the above mentioned methods;* Testing these techniques in the wide range of experimental data. This physic-mathematical model of carbon materials (CM aerothermochemical destruction is based on using the following:* Arrhenius equations to calculate carbon kinetic oxidation;* Langmuir-Knudsen formula to calculate the velocity of non-equilibrium carbon’s sublimation;* Carbon erosion law represented as a unique dependence of this process velocity on the gas pressure on the wall.Mathematical description of all major processes included in this formulation of the problem, contains a number of "free" parameters that can be determined only on the basis of comparison of theoretical and experimental data according to total ablation characteristics of these materials.This comparison was performed in the article applicable to the tests conditions of modern CM in the stream of electric arc plant and in combustion products of liquid-propellant rocket engines.As the result, the data of kinetic of carbon oxidation by atomic oxygen at sublimation mode of material ablation were obtained for the first time. Carbon erosion law under high pressure was established for the first time.The new approach to processing of ablation experiments is enunciated. Using this approach allows to turn this experiments for CM from comparative tests into the tests to determine ablation properties of thermal protection. Moreover, it enables us also to use the

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

    Science.gov (United States)

    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. Transient Ablation of Teflon Hemispheres

    Science.gov (United States)

    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.

  4. Catheter Ablation

    Science.gov (United States)

    ... ablation. Visit Cardiac ablation procedures and Cardiac conduction system for more information about this topic. Related ... National Institutes of Health Department of Health and Human Services USA.gov

  5. 纳米改性喷口材料PTFE耐烧蚀性能的研究%Research on Ablation Resistance of Nano Modified Nozzle Material PTFE

    Institute of Scientific and Technical Information of China (English)

    赵训君

    2016-01-01

    为分析纳米改性PTFE的耐电弧烧蚀性能,在PTFE中添加不同质量分数的BN、AlN、MoS2制得PTFE喷口材料,并对其进行烧蚀试验。结果表明:在电弧电流21 A、电弧电压45 V、燃弧间距6 mm、燃弧时间5 s的条件下,添加BN的PTFE耐烧蚀性能最好,添加BN+MoS2的次之,添加AlN的最差,其中添加20%BN填料的PTFE耐烧蚀性能最佳。%A PTFE nozzle material was prepared by adding different mass fraction of BN, AlN, and MoS2 to PTFE, and its arc ablation resistance was studied. The results show that when the arc current, arc voltage, arc length, and arc burning time is 45 V, 6mm, 21 A, and 5 s, respectively, the BN modified PTFE has the best ablation resistance, the BN and MoS2 modified PTFE has the better ablation resis-tance, and the AlN modified PTFE has the worst ablation resistance. While the PTFE modified by 20%of BN has the optimum ablation resistance.

  6. Metallurgical and chemical characterization of copper alloy reference materials within laser ablation inductively coupled plasma mass spectrometry: Method development for minimally-invasive analysis of ancient bronze objects

    Energy Technology Data Exchange (ETDEWEB)

    Walaszek, Damian, E-mail: damian.walaszek@empa.ch [Laboratory for Analytical Chemistry, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf (Switzerland); University of Warsaw, Faculty of Chemistry, Pasteura 1, 02-093 Warsaw (Poland); Senn, Marianne [Laboratory for Analytical Chemistry, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf (Switzerland); Faller, Markus [Laboratory for Jointing Technology and Corrosion, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf (Switzerland); Philippe, Laetitia [Laboratory for Mechanics of Materials and Nanostructures, Swiss Federal Laboratories for Materials Science and Technology, Feuerwerkstrasse 39, CH-3602 Thun (Switzerland); Wagner, Barbara; Bulska, Ewa [University of Warsaw, Faculty of Chemistry, Pasteura 1, 02-093 Warsaw (Poland); Ulrich, Andrea [Laboratory for Analytical Chemistry, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, CH-8600 Dübendorf (Switzerland)

    2013-01-01

    The chemical composition of ancient metal objects provides important information for manufacturing studies and authenticity verification of ancient copper or bronze artifacts. Non- or minimal-destructive analytical methods are preferred to mitigate visible damage. Laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) enables the determination of major elements as well as impurities down to lower ppm-levels, however, accuracy and precision of analysis strongly depend on the homogeneity of reference materials used for calibration. Moreover, appropriate analytical procedures are required e.g. in terms of ablation strategies (scan mode, spot size, etc.). This study reviews available copper alloy (certified) reference materials — (C)RMs from different sources and contributes new metallurgical data on homogeneity and spatial elemental distribution. Investigations of the standards were performed by optical and scanning electron microscopy with X-ray spectrometry (SEM-EDX) for the following copper alloy and bronze (certified) reference materials: NIST 454, BAM 374, BAM 211, BAM 227, BAM 374, BAM 378, BAS 50.01-2, BAS 50.03-4, and BAS 50.04-4. Additionally, the influence of inhomogeneities on different ablation and calibration strategies is evaluated to define an optimum analytical strategy in terms of line scan versus single spot ablation, variation of spot size, selection of the most appropriate RMs or minimum number of calibration reference materials. - Highlights: ► New metallographic data for copper alloy reference materials are provided. ► Influence of RMs homogeneity on quality of LA-ICPMS analysis was evaluated. ► Ablation and calibration strategies were critically discussed. ► An LA-ICPMS method is proposed for analyzing most typical ancient copper alloys.

  7. Towards the Industrial Application of Spark Ablation for Nanostructured Functional Materials

    NARCIS (Netherlands)

    Pfeiffer, T.V.

    2014-01-01

    Nanostructuring of functional materials is an essential part in the design of energy related devices – but the industrial tools we have to make these materials are lacking. This dissertation explores the green, flexible, and scalable spark discharge process for the fabrication of complex nanostructu

  8. Laser ablation of the lysozyme protein: a model system for soft materials

    DEFF Research Database (Denmark)

    Schou, Jørgen; Matei, Andreea; Constantinescu, Catalin;

    ionization) in contrast to many other organic materials. Also the thermal properties, including the heat-induced decomposition behavior are comparatively well-known. For laser-irradiation at wavelengths above 310 nm, no photochemical processes occur initially, but the material is ejected via photothermal...

  9. Recent Studies on the Modification of Resin-matrix Ablative Material by Nano-materials%纳米材料改性树脂基耐烧蚀材料研究新进展

    Institute of Scientific and Technical Information of China (English)

    王富忠; 秦岩; 黄志雄; 王雁冰; 贾金荣

    2012-01-01

    The recent research progress of resin-matrix ablative material modified by nano-materials was reviewed. The effects of the addition of carbon nanotubes, graphene, montmorillonite, nano-silica and nano-carbon black on the properties of the resin-matrix ablative material were introduced. Thermal stabilities, char yield rate, mechanical properties of modified material were detailedly studied and compared. The problems of the modification of re-sin-matrix ablative material were also discussed. And the development trend of resin-matrix ablative material modification by nano-materials was forecasted. It is also put forward that novel nano-materials. especially the carbon nano-materials, modified resin-matrix ablative materials will become a very promising research field which will arouse further attentioa%综述了近年来纳米材料改性树脂基耐烧蚀材料的研究进展.介绍了碳纳米管、石墨烯、蒙脱土、纳米SiO2、纳米碳粉等纳米材料在改性烧蚀材料中的研究近况,详细探讨和比较了改性材料的热稳定性、成炭率、力学性能等,同时分析了纳米材料改性树脂材料中存在的问题,并预测了纳米材料改性耐烧蚀树脂的发展趋势.提出纳米材料,特别是新型的纳米碳材料改性树脂基耐烧蚀材料的研究将是很有发展前景的研究领域,并会进一步得到人们的重视.

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

    Science.gov (United States)

    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.

  11. femtosecond laser ablation

    OpenAIRE

    Margetic, Vanja

    2003-01-01

    Femtosecond laser ablation was investigated as a solid sampling method for elemental chemical analysis. In comparison to the sampling with longer laser pulses, two aspects could be improved by using ultrashort pulses: elimination of the elemental fractionation from the ablation crater, which is necessary for an accurate quantitative analysis, and better control of the material removal (especially for metals), which increases the spatial resolution of microanalysis. Basic aspects of ultrashort...

  12. Condensation of ablated first-wall materials in the cascade inertial confinement fusion reactor

    Energy Technology Data Exchange (ETDEWEB)

    Ladd, A.J.C.

    1985-12-18

    This report concerns problems involved in recondensing first-wall materials vaporized by x rays and pellet debris in the Cascade inertial confinement fusion reactor. It examines three proposed first-wall materials, beryllium oxide (BeO), silicon carbide (SiO), and pyrolytic graphite (C), paying particular attention to the chemical equilibrium and kinetics of the vaporized gases. The major results of this study are as follows. Ceramic materials composed of diatomic molecules, such as BeO and SiC, exist as highly dissociated species after vaporization. The low gas density precludes significant recombination during times of interest (i.e., less than 0.1 s). The dissociated species (Be, O, Si, and C) are, except for carbon, quite volatile and are thermodynamically stable as a vapor under the high temperature and low density found in Cascade. These materials are thus unsuitable as first-wall materials. This difficulty is avoided with pyrolytic graphite. Since the condensation coefficient of monatomic carbon vapor (approx. 0.5) is greater than that of the polyatomic vapor (<0.1), recondensation is assisted by the expected high degree of dissociation. The proposed 10-layer granular carbon bed is sufficient to condense all the carbon vapor before it penetrates to the BeO layer below. The effective condensation coefficient of the porous bed is about 50% greater than that of a smooth wall. An estimate of the mass flux leaving the chamber results in a condensation time for a carbon first wall of about 30 to 50 ms. An experiment to investigate condensation in a Cascade-like chamber is proposed.

  13. Thermogravimetric Determination of Kinetic Parameters for the Thermal Degradation of Several Ablative Materials.

    Science.gov (United States)

    1980-12-01

    Materials by a Multiple Heating Rate Method, " Thermochimica Acta , in press, and also NSWC TR 80-204 (Dahlgren, Va., July 1980). 3. J. H. Flynn and L. A...System," Thermochimica Acta , No. 1, (1970), pp. 29-38. 21 APPENDIX EXPERIMENTAL DATA 23 4-l *~0 0 0 0 8 a 1 0 0 0 0 0 N 0 0 S 3- 0 0 0 0 0 0 0 0 0 0

  14. Redistribution of a material at femtosecond laser ablation of a thin silver film

    Science.gov (United States)

    Danilov, P. A.; Zayarny, D. A.; Ionin, A. A.; Kudryashov, S. I.; Rudenko, A. A.; Kuchmizhak, A. A.; Vitrik, O. B.; Kulchin, Yu. N.; Zhakhovsky, V. V.; Inogamov, N. A.

    2016-12-01

    Energy-dispersive X-ray microspectroscopy is used for the first time to quantitatively study the spatial displacement of the material of a 100-nm silver film irradiated by a single femtosecond laser pulse focused on a small spot in the diffraction limit. The silver mass distribution over radial cross sections is determined and matter balance is analyzed for the resulting radially symmetric submicron structures of a microcone with a nanospike with various heights and a through hole. Hydrodynamic processes and phase transitions inducing the melting of the film, motion of the melt, and its recrystallization within a focal spot are studied.

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

    Science.gov (United States)

    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 (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. Accessible variation of pulse front tilt gives full spatiotemporal control over the intensity distribution at the focus and another degree of freedom in ablation processes. Finally, real-time visualization of the femtosecond machining process is vital for industrial/medical applications, especially in medical where imaging is through scattering materials. At present a secondary imaging laser system is needed in conjunction with the surgical laser. Using complex, off the shelf, refractive optics we have created a real-time, inline (refractive), delivery system that is robust to scattering and integrated

  16. Ablation of solids by femtosecond lasers: ablation mechanism and ablation thresholds for metals and dielectrics

    OpenAIRE

    Gamaly, E. G.; Rode, A. V.; Tikhonchuk, V. T.; Luther-Davies, B.

    2001-01-01

    The mechanism of ablation of solids by intense femtosecond laser pulses is described in an explicit analytical form. It is shown that at high intensities when the ionization of the target material is complete before the end of the pulse, the ablation mechanism is the same for both metals and dielectrics. The physics of this new ablation regime involves ion acceleration in the electrostatic field caused by charge separation created by energetic electrons escaping from the target. The formulae ...

  17. Ablation of solids by femtosecond lasers ablation mechanism and ablation thresholds for metals and dielectrics

    CERN Document Server

    Gamaly, E G; Tikhonchuk, V T; Luther-Davies, B

    2001-01-01

    The mechanism of ablation of solids by intense femtosecond laser pulses is described in an explicit analytical form. It is shown that at high intensities when the ionization of the target material is complete before the end of the pulse, the ablation mechanism is the same for both metals and dielectrics. The physics of this new ablation regime involves ion acceleration in the electrostatic field caused by charge separation created by energetic electrons escaping from the target. The formulae for ablation thresholds and ablation rates for metals and dielectrics, combining the laser and target parameters, are derived and compared to experimental data. The calculated dependence of the ablation thresholds on the pulse duration is in agreement with the experimental data in a femtosecond range, and it is linked to the dependence for nanosecond pulses.

  18. Power Laser Ablation Symposia

    CERN Document Server

    Phipps, Claude

    2007-01-01

    Laser ablation describes the interaction of intense optical fields with matter, in which atoms are selectively driven off by thermal or nonthermal mechanisms. The field of laser ablation physics is advancing so rapidly that its principal results are seen only in specialized journals and conferences. This is the first book that combines the most recent results in this rapidly advancing field with authoritative treatment of laser ablation and its applications, including the physics of high-power laser-matter interaction. Many practical applications exist, ranging from inertial confinement fusion to propulsion of aerostats for pollution monitoring to laser ignition of hypersonic engines to laser cleaning nanoscale contaminants in high-volume computer hard drive manufacture to direct observation of the electronic or dissociative states in atoms and molecules, to studying the properties of materials during 200kbar shocks developed in 200fs. Selecting topics which are representative of such a broad field is difficu...

  19. PLC控制步进电机在绝热材料烧蚀仪中的应用%Application of Stepping Motor Controlled by PLC in Adiabatic Material Ablation

    Institute of Scientific and Technical Information of China (English)

    王林狮; 胡锡梅; 胡志新; 王震武

    2011-01-01

    利用可编程控制器(PLC)控制步进电机和烧蚀枪,实现了绝热材料烧蚀过程的自动化控制.克服了目前烧蚀仪采用普通电机-继电器控制,具有接线复杂、体积大、自动化程度低、计时精度低等缺点.利用PLC控制步进电机的转向和转速,从而控制烧蚀枪的运动轨迹,通过烧蚀试验得出可靠的烧蚀规范参数.经过烧蚀试验证明,研制出的新型绝热材料烧蚀仪噪声小,升降速过程快,能够实现烧蚀枪的精确定位,对提高系统的可靠性和工作效率具有重要意义.%The stepping motor and ablating gun controlled by PLC system can realize automatic control of the ablation for adia-batic material. The traditional ablating instrument with general motor relay-contactor has disadvantages of complex circuit, big volume and low degree of automation, which have been overcame. Adopting PLC to control the stepping motor turning speed and direction as well as the motion curve of ablating gun, and a group of typical ablating parameters can be obtained by the ablating experiment. The ablating test shows that the new ablating equipment for adiabatic material has advantages of small noise and fast speed in acceleration and deceleration, which is of great significance for enhancing the system reliability and efficiency.

  20. Hetero-epitaxial growth of the cubic single crystalline HfO 2 film as high k materials by pulsed laser ablation

    Science.gov (United States)

    Zhang, Xinqiang; Tu, Hailing; Wang, Xiaona; Xiong, Yuhua; Yang, Mengmeng; Wang, Lei; Du, Jun

    2010-10-01

    We report a hetero-epitaxial growth of cubic single crystalline HfO 2 film on Si substrates as high k materials by pulse laser ablation (PLA) at 820 °C. To eliminate the interfacial defects, the HfO 2 film has then been annealed at 900 °C for 5 min in N 2. Reflection high-energy electron diffraction (RHEED) results indicate orientation of the HfO 2 film on Si substrates corresponding to (∥( and [∥[. An interface layer has been revealed by high-resolution transmission electron microscope (HRTEM). Through capacitance-voltage ( C- V) and current-voltage ( I- V), it has been obtained that the leakage current of the HfO 2 gate insulator with dielectric constant of 26 is 5×10 -6 A/cm 2 at -1 V.

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

    Science.gov (United States)

    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.

  2. Femtosecond laser ablation of silicon in air and vacuum

    Institute of Scientific and Technical Information of China (English)

    Zehua Wu; Nan Zhang; Mingwei Wang; Xiaonong Zhu

    2011-01-01

    Femtosecond (fs) pulse laser ablation of silicon targets in air and in vacuum is investigated using a time-resolved shadowgraphic method. The observed dynamic process of the fs laser ablation of silicon in air is significantly different from that in vacuum. Similar to the ablation of metallic targets, while the shock wave front and a series of nearly concentric and semicircular stripes, as well as the contact front, are clearly identifiable in the process of ablation under 1 x 105 Pa, these phenomena are no longer observed when the ablation takes place in vacuum. Although the ambient air around the target strongly affects the evolution of the ablation plume, the three rounds of material ejection clearly observed in the shadowgraphs of fs laser ablation in standard air can also be distinguished in the process of ablation in vacuum. It is proven that the three rounds of material ejection are caused by different ablation mechanisms.%@@ Femtosecond(fs)pulse laser ablation of silicon targets in air and in vacuum is investigated using a timeresolved shadowgraphic method.The observed dynamic process of the fs laser ablation of silicon in air is significantly different from that in vacuum.Similar to the ablation of metallic targets,while the shock wave front and a series of nearly concentric and semicircular stripes,as well as the contact front,are clearly identifiable in the process of ablation under 1 x 105 Pa,these phenomena are no longer observed when the ablation takes place in vacuum.Although the ambient air around the target strongly affects the evolution of the ablation plume,the three rounds of material ejection clearly observed in the shadowgraphs of fs laser ablation in standard air can also be distinguished in the process of ablation in vacuum.It is proven that the three rounds of material ejection are caused by different ablation mechanisms.

  3. Femtosecond laser ablation of enamel

    Science.gov (United States)

    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.

  4. Characterization of a 50kW Inductively Coupled Plasma Torch for Testing of Ablative Thermal Protection Materials

    Science.gov (United States)

    Greene, Benton R.; Clemens, Noel T.; Varghese, Philip L.; Bouslog, Stanley A.; Del Papa, Steven V.

    2017-01-01

    With the development of new manned spaceflight capabilities including NASA's Orion capsule and the Space-X Dragon capsule, there is a renewed importance of understanding the dynamics of ablative thermal protection systems. To this end, a new inductively coupled plasma torch facility is being developed at UT-Austin. The torch operates on argon and/or air at plasma powers up to 50 kW. In the present configuration the flow issues from a low-speed subsonic nozzle and the hot plume is characterized using slug calorimetry and emission spectroscopy. Preliminary measurements using emission spectroscopy have indicated that the torch is capable of producing an air plasma with a temperature between 6,000 K and 8,000 K depending on the power and flow settings and an argon plasma with a temperature of approximately 12,000 K. The operation envelope was measured, and heat flux measured for every point within the envelope using both a slug calorimeter and a Gardon gauge heat flux sensor. The torch was found to induce a stagnation point heat flux of between 90 and 225 W/sq cm.

  5. Colloids and composite materials Au/Pvp and Ag/Pvp generated by laser ablation in polymeric liquid environment

    Energy Technology Data Exchange (ETDEWEB)

    Larez, J.; Rojas, C. [Universidad Central de Venezuela, Faculty of Science, Center of Experimental Solid State Physics, Paseo Los Ilustres, Los Chaguaramos, Apdo. Postal 20513, Caracas 1020-A (Venezuela, Bolivarian Republic of); Castell, R., E-mail: jlarez@fisica.ciens.ucv.ve [Universidad Simon Bolivar, Department of Physics, Plasma and Laser Spectroscopy Laboratory, Valle de Sartenejas, Baruta, Apdo. Postal 89000, Caracas 1080-A (Venezuela, Bolivarian Republic of)

    2016-11-01

    Pulsed laser ablation of silver and gold targets, immersed in a polymeric solution of Polyvinylpyrrolidone (Pvp), is used to generate colloids and composite metal-polymer. Solutions of Pvp in deionized water at different concentrations are employed. Two Pvp number average molecular weights were considered, 10000 g/mol and 55000 g/mol. The high purity targets are irradiated between 20 min and 40 min with the third harmonic (Thg) (λ = 335 nm) of a Nd:YAG laser operating at a rate of 10 Hz with pulses of 8 ns. Optical spectroscopy in UV and vis regions, scanning electron microscopy, high resolution scanning electron microscopy and X-ray are used to identify and determine the shape and size of the produced particles. Very stable sub-micrometric spherical particles for Au/Pvp and Ag/Pvp samples are obtained with diameters of 0.72 μm and 0.40 μm, respectively. The preparation of colloids is performed in one step and no surfactant or dispersing agent is used in this process. (Author)

  6. 非烧蚀型防热材料烧蚀性能初步试验研究%Preliminary tests of non-ablative thermal protection materials

    Institute of Scientific and Technical Information of China (English)

    刘初平; 孟松鹤; 杜百合; 王国林

    2009-01-01

    介绍了在CARDC等离子体风洞中开展的非烧蚀型防热材料超高温陶瓷(UHTC)的试验研究结果.对Φ20mm平头圆柱体试验模型,采用亚声速驻点试验技术,在驻点热流478W/cm2,气流焓值27.9MJ/kg,环境压力18kPa条件下,分别对代号C(15、10)型、Y型、S(30、15、10)型3种材料模型进行了试验研究,并对模型试验前后的长度变化、质量变化以及模型表面温度进行了测量,初步分析了模型的表观变化、抗氧化特性和表面辐射特性.结果表明:Y型模型试验前后表观变化不大,表面温度达到1930℃;S型模型表面生成一层薄氧化层,稳定情形下模型表面温度达到1964℃;C型模型表面烧蚀严重,模型表面温度达到2462℃,防热性能最差.%The test results of non-ablative ultra-high temperature ceramic materials (UHTC) in one of the plasma wind tunnels of CARDC are introduced in this paper. Three types of materials, namely model C (15、10) ,Y and S(30、15、10),were tested under a subsonic condition with stagnation point heat flux of 478W/ cm2,enthalpy of 27.9 MJ/kg and stagnation point pressure of 18kPa. The test models were in flat cylinder shape with a diameter of 20mm. The length variation and mass loss and surface temperature of each test model were measured .Test results showed that model Y surface temperature reached 1930℃ with little surface char-acteristics change,model S surface temperature reached 1964℃ with an oxidation layer formed and model C surface temperature reached 2462℃ yet experienced severe ablation. Preliminary analyses of the tested materi-als in terms of surface characteristics change, anti-oxidation characteristics and surface radiation characteristics are also presented.

  7. VUV laser ablation of polymers. Photochemical aspect

    Science.gov (United States)

    Castex, M. C.; Bityurin, N.; Olivero, C.; Muraviov, S.; Bronnikova, N.; Riedel, D.

    2000-12-01

    A photochemical theory of laser ablation owing to the direct chain scission process is considered in quite general form taking into account the modification of material. The formulas obtained can be used for estimating mechanisms of VUV laser ablation of polymers.

  8. Attachment and proliferation of human osteoblast-like cells (MG-63) on laser-ablated titanium implant material

    Energy Technology Data Exchange (ETDEWEB)

    Györgyey, Ágnes; Ungvári, Krisztina [Department of Oral Biology and Experimental Dental Research, Faculty of Dentistry, University of Szeged, H-6720 Szeged (Hungary); Kecskeméti, Gabriella; Kopniczky, Judit [Department of Optics and Quantum Electronics, Faculty of Science and Informatics, University of Szeged, H-6720 Szeged (Hungary); Hopp, Béla [Research Group on Laser Physics, Hungarian Academy of Sciences and University of Szeged, H-6720 Szeged (Hungary); Oszkó, Albert [Department of Physical Chemistry and Materials Science, Faculty of Science and Informatics, University of Szeged, H-6720 Szeged (Hungary); Pelsöczi, István; Rakonczay, Zoltán [Department of Oral Biology and Experimental Dental Research, Faculty of Dentistry, University of Szeged, H-6720 Szeged (Hungary); Nagy, Katalin [Department of Oral Surgery, Faculty of Dentistry, University of Szeged, H-6720 Szeged (Hungary); Turzó, Kinga, E-mail: kturzo@yahoo.com [Department of Oral Biology and Experimental Dental Research, Faculty of Dentistry, University of Szeged, H-6720 Szeged (Hungary)

    2013-10-15

    Demand is increasing for shortening the long (3–6 months) osseointegration period to rehabilitate patients' damaged chewing apparatus in as short a time as possible. For dental implants, as for biomaterials in general, the bio- and osseointegration processes can be controlled at molecular and cellular levels by modification of the implant surface. One of the most promising of such surface modifications is laser ablation, as demonstrated by our previous results [46]. Commercially pure (CP4) sand-blasted, acid-etched titanium disks (Denti® System Ltd., Hungary) were irradiated with a KrF excimer laser (248 nm, fluence 0.4 J/cm{sup 2}, FWHM 18 ns, 2000 pulses), or with a Nd:YAG laser (532 nm, 1.3 J/cm{sup 2}, 10 ns, 200 pulses) then examined by SEM, AFM, and XPS. In vitro attachment (24 h) and proliferation (72 h) of MG-63 osteoblast cells were investigated via dimethylthiazol-diphenyl tetrazolium bromide (MTT), alamarBlue (AB) assays alkaline phosphatase quantification (ALP) and SEM. SEM and AFM revealed significant changes in morphology and roughness. XPS confirmed the presence of TiO{sub 2} on each sample; after Nd:YAG treatment a reduced state of Ti (Ti{sup 3+}) was also observed. MTT, AB and ALP measurements detected an increase in the number of cells between the 24- and 72 hour observations; however, laser treatment did not affect cell attachment and proliferation significantly. - Highlights: • CP4 titanium implant surfaces were modified with Nd:YAG and KrF excimer laser. • SEM and AFM revealed significant changes in morphology and roughness. • XPS confirmed the presence of TiO{sub 2} on each sample; after Nd:YAG treatment a reduced state of Ti (Ti{sup 3+}) was found. • Cell proliferation experiments detected an increased number of MG-63 cells between the 24 h and 72 h observations. • Laser treatments neither disturbed, nor enhanced MG-63 cell attachment and proliferation significantly.

  9. Ablative Ceramic Foam Based TPS Project

    Data.gov (United States)

    National Aeronautics and Space Administration — A novel composite material ablative TPS for planetary vehicles that can survive a dual heating exposure is proposed. NextGen's TPS concept is a bi-layer functional...

  10. Transarterial embolization (TAE) as add-on to percutaneous radiofrequency ablation (RFA) for the treatment of renal tumors: Review of the literature, overview of state-of-the-art embolization materials and further perspective of advanced image-guided tumor ablation.

    Science.gov (United States)

    Sommer, C M; Pallwein-Prettner, L; Vollherbst, D F; Seidel, R; Rieder, C; Radeleff, B A; Kauczor, H U; Wacker, F; Richter, G M; Bücker, A; Rodt, T; Massmann, A; Pereira, P L

    2017-01-01

    Percutaneous radiofrequency ablation (RFA) for the treatment of stage I renal cell carcinoma has recently gained significant attention as the now available long-term and controlled data demonstrate that RFA can result in disease-free and cancer-specific survival comparable with partial and/or radical nephrectomy. In the non-controlled single center trials, however, the rates of treatment failure vary. Operator experience and ablation technique may explain some of the different outcomes. In the controlled trials, a major limitation is the lack of adequate randomization. In case reports, original series and overview articles, transarterial embolization (TAE) before percutaneous RFA was promising to increase tumor control and to reduce complications. The purpose of this study was to systematically review the literature on TAE as add-on to percutaneous RFA for renal tumors. Specific data regarding technique, tumor and patient characteristics as well as technical, clinical and oncologic outcomes have been analyzed. Additionally, an overview of state-of-the-art embolization materials and the radiological perspective of advanced image-guided tumor ablation (TA) will be discussed. In conclusion, TAE as add-on to percutaneous RFA is feasible and very effective and safe for the treatment of T1a tumors in difficult locations and T1b tumors. Advanced radiological techniques and technologies such as microwave ablation, innovative embolization materials and software-based solutions are now available, or will be available in the near future, to reduce the limitations of bland RFA. Clinical implementation is extremely important for performing image-guided TA as a highly standardized effective procedure even in the most challenging cases of localized renal tumors.

  11. Photochemical Ablation of Organic Solids

    Science.gov (United States)

    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).

  12. Laser Ablation Propulsion A Study

    Science.gov (United States)

    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

  13. Ablation of GaN Using a Femtosecond Laser

    Institute of Scientific and Technical Information of China (English)

    刘伟民; 朱荣毅; 钱土雄; 袁述; 张国义

    2002-01-01

    We study the pulsed laser ablation of wurtzite gallium nitride (GaN) films grown on sapphire, using the fem tosecond laser beam at a central wavelength of 800nm as the source for the high-speed ablation of GaN films. By measuring the backscattered Raman spectrum of ablated samples, the dependence of the ablation depth on laser fluence with one pulse was obtained. The threshold laser fluence for the ablation of GaN films was determined to be about 0.25J/cm2. Laser ablation depth increases with the increasing laser fluence until the amount of removed material is not further increased. The ablated surface was investigated by an optical surface interference profile meter.

  14. Near-field ablation threshold of cellular samples at mid-IR wavelengths

    CERN Document Server

    Raghu, Deepa; Gamari, Benjamin; Reeves, M E

    2012-01-01

    We report the near-field ablation of material from cellulose acetate coverslips in water and my- oblast cell samples in growth media, with a spot size as small as 1.5 {\\mu}m under 3 {\\mu}m wavelength radiation. The power dependence of the ablation process has been studied and comparisons have been made to models of photomechanical and plasma-induced ablation. The ablation mechanism is mainly dependent on the acoustic relaxation time and optical properties of the materials. We find that for all near-field experiments, the ablation thresholds are very high, pointing to plasma-induced ablation as the dominant mechanism.

  15. Ablation Performance of a Novel Super-hybrid Composite

    Institute of Scientific and Technical Information of China (English)

    Jun QIU; Xiaoming CAO; Chong TIAN; Jinsong ZHANG

    2005-01-01

    A novel super-hybrid composite (NSHC) was boron-modified phenolic resin (BPR) with three-dimensional reticulated SiC ceramic (3DRC) and high silica fibers. Ablation performance of the NSHC was studied. The results show that the linear ablation rate of NSHC was lower than that of pure BPR and the high silica/BPR composite. Its linear ablation rate is 1/17 of the high silica/BPR. Mass ablation rate of the NSHC is very close to that of the pure BPR and the high silica/BPR composite. Scanning electron microscope (SEM) analysis indicates that 3DRC has scarcely changed its shape at the ablation temperature. Its special reticulated structure can restrict the materials deformation and prevent high velocity heat flow from eroding the surface of the materials largely and thus increase ablation resistance of the NSHC.

  16. Laser ablation in analytical chemistry - A review

    Energy Technology Data Exchange (ETDEWEB)

    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. Laser ablation principles and applications

    CERN Document Server

    1994-01-01

    Laser Ablation provides a broad picture of the current understanding of laser ablation and its many applications, from the views of key contributors to the field. Discussed are in detail the electronic processes in laser ablation of semiconductors and insulators, the post-ionization of laser-desorbed biomolecules, Fourier-transform mass spectroscopy, the interaction of laser radiation with organic polymers, laser ablation and optical surface damage, laser desorption/ablation with laser detection, and laser ablation of superconducting thin films.

  18. Phenolic Impregnated Carbon Ablator (PICA) Gap Filler for Heat Shield Assemblies Project

    Data.gov (United States)

    National Aeronautics and Space Administration — During this program, Fiber Materials, Inc. (FMI) will develop practical methods for preparing Phenolic Impregnated Carbon Ablator (PICA) materials for joining...

  19. Phenolic Impregnated Carbon Ablator (PICA) Gap Filler for Heat Shield Assemblies Project

    Data.gov (United States)

    National Aeronautics and Space Administration — During this program Fiber Materials, Inc. (FMIREG) will develop practical methods for preparing Phenolic Impregnated Carbon Ablator (PICA) materials for joining...

  20. Hard tissue ablation with a spray-assisted mid-IR laser

    Energy Technology Data Exchange (ETDEWEB)

    Kang, H W [American Medical Systems, Minnetonka, MN (United States); Rizoiu, I [BioLase Technology, Irvine, CA (United States); Welch, A J [Department of Biomedical Engineering, University of Texas at Austin, Austin, TX (United States)

    2007-12-21

    The objective of this study was to understand the dominant mechanism(s) for dental enamel ablation with the application of water spray. A free-running Er,Cr:YSGG (yttrium, scandium, gallium, garnet) laser was used to ablate human enamel tissue at various radiant exposures. During dental ablation, distilled water was sprayed on the sample surface, and these results were compared to ablation without a spray (dry ablation). In order to identify dominant ablation mechanisms, transient acoustic waves were compared to ablation thresholds and the volume of material removed. The ablation profile and depth were measured using optical coherence tomography (OCT). Irregular surface modification, charring and peripheral cracks were associated with dry ablation, whereas craters for spray samples were relatively clean without thermal damage. In spite of a 60% higher ablation threshold for spray associated irradiations owing to water absorption, acoustic peak pressures were six times higher and ablation volume was up to a factor of 2 larger compared to dry ablation. The enhanced pressure and ablation performance of the spray-assisted process was the result of rapid water vaporization, material ejection with recoil stress, interstitial water explosion and possibly liquid-jet formation. With water cooling and abrasive/disruptive mechanical effects, the spray ablation can be a safe and efficient modality for dental treatment.

  1. Ablation of steel using picosecond laser pulses in burst mode

    Science.gov (United States)

    Lickschat, Peter; Demba, Alexander; Weissmantel, Steffen

    2017-02-01

    Results obtained in picosecond laser processing of steel applying the burst mode are presented. Using the burst mode, pulse trains, i.e., bursts, consisting of a number of picosecond pulses with an inter-pulse delay of 12.5 ns and 10 ps pulse duration are applied for material processing. Small cavities with sizes in the range of the laser beam diameter made by single-burst ablation are compared to quadratic cavities of 0.5 × 0.5 mm² produced by multiburst ablation and simultaneous scanning of the laser beam across the steel sample surface. The ablated volume per pulse within the burst was calculated either from the ablated volume per burst or from the ablation depth of the quadratic cavities. With the second to fourth pulses in the bursts, a reduction of the ablated volume per pulse in comparison with the first pulse in the bursts (i.e., to the use of single pulses) was found for both single- and multiburst ablation, which is assumed to be due to plasma shielding. By contrast, the ablated volume per pulse within the bursts increases for the fifth to eighth pulses. Heat accumulation effect and the influence of the heated plasma can be assumed to be the reason for these higher ablation rates. SEM micrographs also show that there is a higher melt ejection out of the laser processed area. This is indicated by the formation of bulges about the ablated area.

  2. Effects of laser ablation on cemented tungsten carbide surface quality

    Energy Technology Data Exchange (ETDEWEB)

    Tan, J.L.; Butler, D.L.; Sim, L.M.; Jarfors, A.E.W. [Singapore Institute of Manufacturing Technology, Singapore (Singapore)

    2010-11-15

    Although laser micromachining has been touted as being the most promising way to fabricate micro tools, there has been no proper evaluation of the effects of laser ablation on bulk material properties. The current work demonstrates the effects of laser ablation on the properties of a cemented tungsten carbide surface. Of particular interest is the resultant increase in compressive residual stresses in the ablated surface. From this study it is seen that there are no adverse effects from laser ablation of cemented tungsten carbide that would preclude its use for the fabrication of micro-tools but a finishing process may not be avoidable. (orig.)

  3. Effects of laser ablation on cemented tungsten carbide surface quality

    Science.gov (United States)

    Tan, J. L.; Butler, D. L.; Sim, L. M.; Jarfors, A. E. W.

    2010-11-01

    Although laser micromachining has been touted as being the most promising way to fabricate micro tools, there has been no proper evaluation of the effects of laser ablation on bulk material properties. The current work demonstrates the effects of laser ablation on the properties of a cemented tungsten carbide surface. Of particular interest is the resultant increase in compressive residual stresses in the ablated surface. From this study it is seen that there are no adverse effects from laser ablation of cemented tungsten carbide that would preclude its use for the fabrication of micro-tools but a finishing process may not be avoidable.

  4. Testing of Advanced Conformal Ablative TPS

    Science.gov (United States)

    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

  5. Cold ablation driven by localized forces in alkali halides

    NARCIS (Netherlands)

    Hada, Masaki; Zhang, Dongfang; Pichugin, Kostyantyn; Hirscht, Julian; Kochman, Micha A.; Hayes, Stuart A.; Manz, Stephanie; Gengler, Regis Y. N.; Wann, Derek A.; Seki, Toshio; Moriena, Gustavo; Morrison, Carole A.; Matsuo, Jiro; Sciaini, German; Miller, R. J. Dwayne

    2014-01-01

    Laser ablation has been widely used for a variety of applications. Since the mechanisms for ablation are strongly dependent on the photoexcitation level, so called cold material processing has relied on the use of high-peak-power laser fluences for which nonthermal processes become dominant; often r

  6. Ablative Rocket Deflector Testing and Computational Modeling

    Science.gov (United States)

    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.

  7. Radiofrequency ablation in dermatology

    Directory of Open Access Journals (Sweden)

    Sachdeva Silonie

    2007-01-01

    Full Text Available Radiofreqeuency ablation is a versatile dermatosurgical procedure used for surgical management of skin lesions by using various forms of alternating current at an ultra high frequency. The major modalities in radiofrequency are electrosection, electrocoagulation, electrodessication and fulguration. The use of radiofrequency ablation in dermatosurgical practice has gained importance in recent years as it can be used to treat most of the skin lesions with ease in less time with clean surgical field due to adequate hemostasis and with minimal side effects and complications. This article focuses on the major tissue effects and factors influencing radiofrequency ablation and its application for various dermatological conditions.

  8. Numerical Modeling of Ablation Heat Transfer

    Science.gov (United States)

    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.

  9. 纳秒激光刻蚀复合材料基金属薄膜机制研究%Mechanism of Nano-Second Laser Ablation of Metallic Thin Film on Composite Material

    Institute of Scientific and Technical Information of China (English)

    杨建平; 陈学康; 吴敢; 王瑞

    2011-01-01

    The processings of laser energy absorption and thermal conduct are analyzed, and a mechanism of metallic film/composite substrate interface separation while metallic film in solid state due to the composite material thermal decomposition is also proposed subsequently. A new method of improving laser ablation accuracy using this mechanism and laser power distribution transform technology is proposed. Laser wavefront diffraction transform technology is employed to convert the ablation laser power density and its distribution, and the confirmed experiment is carried out.%通过分析激光脉冲作用于金属薄膜后的能量吸收及演化过程,提出了金属薄膜/复合材料组合体系在纳秒级脉冲激光作用下,因复合材料易气化的特性而存在的特有的薄膜/基底界面分离现象.提出利用这一特有的界面分离过程,可通过控制激光能量密度实现对这种结构体系的高精度、无损伤的刻蚀.利用波前衍射变换技术整形过的刻蚀激光进行了验证实验,实验结果证实了这一方法的可行性.

  10. Spectroscopy Measurements on Ablation Testing in High Enthalpy Plasma Flows

    Science.gov (United States)

    2010-11-01

    stagnation point, are located on the ablative material sample. 3.5 InfraRed THERMOGRAPHY Surface temperature measurement is a topic of great concern...high temperature material at two different narrow wavelengths. The temperature is calculated by building the ratio of the radiation intensities. The...this work is to develop the capability of testing and characterization of ablative materials exposed to high enthalpy plasma flows including both

  11. Percutaneous Microwave Ablation of Renal Angiomyolipomas

    Energy Technology Data Exchange (ETDEWEB)

    Cristescu, Mircea, E-mail: mcristescu@uwhealth.org [University of Wisconsin, Department of Radiology (United States); Abel, E. Jason, E-mail: abel@urology.wisc.edu [University of Wisconsin, Department of Urology (United States); Wells, Shane, E-mail: swells@uwhealth.org; Ziemlewicz, Timothy J., E-mail: tziemlewicz@uwhealth.org [University of Wisconsin, Department of Radiology (United States); Hedican, Sean P., E-mail: hedican@surgery.wisc.edu [University of Wisconsin, Department of Urology (United States); Lubner, Megan G., E-mail: mlubner@uwhealth.org; Hinshaw, J. Louis, E-mail: jhinshaw@uwhealth.org; Brace, Christopher L., E-mail: cbrace@uwhealth.org; Lee, Fred T., E-mail: flee@uwhealth.org [University of Wisconsin, Department of Radiology (United States)

    2016-03-15

    PurposeTo evaluate the safety and efficacy of US-guided percutaneous microwave (MW) ablation in the treatment of renal angiomyolipoma (AML).Materials and MethodsFrom January 2011 to April 2014, seven patients (5 females and 2 males; mean age 51.4) with 11 renal AMLs (9 sporadic type and 2 tuberous sclerosis associated) with a mean size of 3.4 ± 0.7 cm (range 2.4–4.9 cm) were treated with high-powered, gas-cooled percutaneous MW ablation under US guidance. Tumoral diameter, volume, and CT/MR enhancement were measured on pre-treatment, immediate post-ablation, and delayed post-ablation imaging. Clinical symptoms and creatinine were assessed on follow-up visits.ResultsAll ablations were technically successful and no major complications were encountered. Mean ablation parameters were ablation power of 65 W (range 60–70 W), using 456 mL of hydrodissection fluid per patient, over 4.7 min (range 3–8 min). Immediate post-ablation imaging demonstrated mean tumor diameter and volume decreases of 1.8 % (3.4–3.3 cm) and 1.7 % (27.5–26.3 cm{sup 3}), respectively. Delayed imaging follow-up obtained at a mean interval of 23.1 months (median 17.6; range 9–47) demonstrated mean tumor diameter and volume decreases of 29 % (3.4–2.4 cm) and 47 % (27.5–12.1 cm{sup 3}), respectively. Tumoral enhancement decreased on immediate post-procedure and delayed imaging by CT/MR parameters, indicating decreased tumor vascularity. No patients required additional intervention and no patients experienced spontaneous bleeding post-ablation.ConclusionOur early experience with high-powered, gas-cooled percutaneous MW ablation demonstrates it to be a safe and effective modality to devascularize and decrease the size of renal AMLs.

  12. Chemical and Spectroscopic Aspects of Polymer Ablation-Special Features and Novel Directions-

    Science.gov (United States)

    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.

  13. Metal particles produced by laser ablation for ICP-MSmeasurements

    Energy Technology Data Exchange (ETDEWEB)

    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. Fundamental studies of pulsed laser ablation

    CERN Document Server

    Claeyssens, F

    2001-01-01

    dopant) have resulted in a coherent view of the resulting plume, which exhibits a multi-component structure correlated with different regimes of ablation, which are attributed to ejection from ZnO and ablation from a Zn melt. OES measurements show that the emitting Zn component within the plume accelerates during expansion in vacuum - an observation attributable to the presence of hot, fast electrons in the plume. The same acceleration behaviour is observed in the case of Al atomic emissions resulting from ablation of an Al target in vacuum. Deposition conditions, substrate temperature and background gas pressure were all varied in a quest for optimally aligned, high quality ZnO thin films. Initial ab initio calculations were performed also, to aid in understanding the stability of these c-axis aligned films. The pulsed ultraviolet (lambda = 193, 248 nm) laser ablation of graphite, polycrystalline diamond and ZnO targets has been investigated. Characteristics of the resulting plumes of ablated material have b...

  15. Thermochemical Ablation Analysis of the Orion Heatshield

    Science.gov (United States)

    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

  16. Graded Density Carbon Bonded Carbon Fiber (CBCF) Preforms for Lightweight Ablative Thermal Protection Systems (TPS) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — FMI has developed graded density CBCF preforms for graded density phenolic impregnated carbon ablator (PICA) material to meet NASA's future exploration mission...

  17. Graded Density Carbon Bonded Carbon Fiber (CBCF) Preforms for Lightweight Ablative Thermal Protection Systems (TPS) Project

    Data.gov (United States)

    National Aeronautics and Space Administration — FMI currently manufactures Phenolic Impregnated Carbon Ablator (PICA) material for Thermal Protection Systems (TPS) systems, such as the Stardust Sample Return...

  18. Ultrasound-guided percutaneous thermal ablation of hepatocellular carcinoma using microwave and radiofrequency ablation

    Energy Technology Data Exchange (ETDEWEB)

    Xu, H.-X.; Xie, X.-Y.; Lu, M.-D. E-mail: lumd@21cn.com; Chen, J.-W.; Yin, X.-Y.; Xu, Z.-F.; Liu, G.-J

    2004-01-01

    AIM: To investigate the therapeutic efficacy of thermal ablation for treatment of hepatocellular carcinoma (HCC) using microwave and radiofrequency (RF) energy application. MATERIALS AND METHODS: A total of 190 nodules in 97 patients (84 male, 13 female; mean age 53.4 years, range 24-74 years) with HCC were treated with microwave or RF ablation in the last 4 years. The applicators were introduced into the tumours under conscious analgesic sedation by intravenous administration of fentanyl citrate and droperidol and local anaesthesia in both thermal ablation procedures. The patients were then followed up with contrast-enhanced computed tomography (CT) to evaluate treatment response. Survival was analysed using the Kaplan-Meier method. RESULTS: Complete ablation was obtained in 92.6% (176/190) nodules. The complete ablation rates were 94.6% (106/112) in microwave ablation and 89.7% (70/78) in RF ablation. The complete ablation rates in tumours{<=}2.0, 2.1-3.9 and {>=}4.0 cm were 93.1, 93.8 and 86.4%, respectively. Local recurrence was found in 9.5% nodules and the rates in tumours{<=}2.0, 2.1-3.9 and {>=}4.0 cm in diameter were 3.4, 9.9 and 31.8%, respectively. In the follow-up period, 7.1% nodules ablated by microwave and 12.8% by RF presented local recurrence. The 1, 2 and 3-year distant recurrence-free survivals were 47.2, 34.9 and 31.0%, respectively. Estimated mean survival was 32 months, and 1, 2 and 3-year cumulative survivals were 75.6, 58.5, and 50.0%, respectively. One and 2 years survivals of Child-Pugh class A, B and C patients were 83.8 and 70.4%, 78.2 and 53.2%, 36.3 and 27.3%, respectively. CONCLUSION: Thermal ablation therapy by means of microwave and RF energy application is an effective and safe therapeutic technique for hepatocellular carcinoma. Large tumours can be completely ablated, but have a significantly higher risk of local recurrence at follow-up.

  19. Laser ablation with applied magnetic field for electric propulsion

    Science.gov (United States)

    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.

  20. Solar cell contact formation using laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    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

    Energy Technology Data Exchange (ETDEWEB)

    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. Sand laser-ablation as source of elements laser isotope separation: preliminary results

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, N.A.S.; Destro, M.G.; Vasconcelos, G; Neri, J.W.; Silveira, C.A.B.; Riva, R. [Institute for Advanced Studies, Sao Jose dos Campos, SP (Brazil)]. E-mail: nicolau@ieav.cta.br

    2008-07-01

    This paper presents preliminary results of emission spectroscopy experiments, performed with the aim to verify the presence of monoatomic neutral material in the jet produced by laser ablation of simple and complex targets. All studied materials (copper, graphite, alumina and beach sand) showed emission of single atoms, indicating the presence of monoatomic material in the ablated plume. (author)

  3. Universal threshold for femtosecond laser ablation with oblique illumination

    Science.gov (United States)

    Liu, Xiao-Long; Cheng, Weibo; Petrarca, Massimo; Polynkin, Pavel

    2016-10-01

    We quantify the dependence of the single-shot ablation threshold on the angle of incidence and polarization of a femtosecond laser beam, for three dissimilar solid-state materials: a metal, a dielectric, and a semiconductor. Using the constant, linear value of the index of refraction, we calculate the laser fluence transmitted through the air-material interface at the point of ablation threshold. We show that, in spite of the highly nonlinear ionization dynamics involved in the ablation process, the so defined transmitted threshold fluence is universally independent of the angle of incidence and polarization of the laser beam for all three material types. We suggest that angular dependence of ablation threshold can be utilized for profiling fluence distributions in ultra-intense femtosecond laser beams.

  4. XUV-laser induced ablation of PMMA with nano-, pico-, and femtosecond pulses

    Energy Technology Data Exchange (ETDEWEB)

    Juha, L. [Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8 (Czech Republic)]. E-mail: juha@fzu.cz; Bittner, M. [Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8 (Czech Republic); Faculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 3, 121 16 Prague 2 (Czech Republic); Chvostova, D. [Institute of Physics, Academy of Sciences of the Czech Republic, Na Slovance 2, 182 21 Prague 8 (Czech Republic)] (and others)

    2005-06-15

    For conventional wavelength (UV-vis-IR) lasers delivering radiation energy to the surface of materials, ablation thresholds, etch (ablation) rates, and the quality of ablated structures often differ dramatically between short (typically nanosecond) and ultrashort (typically femtosecond) pulses. Various very short-wavelength ({lambda} < 100 nm) lasers, emitting pulses with durations ranging from {approx}10 fs to {approx}1 ns, have recently been placed into routine operation. This has facilitated the investigation of how ablation characteristics depend on the pulse duration in the XUV spectral region. Ablation of poly(methyl methacrylate) (PMMA) induced by three particular short-wavelength lasers emitting pulses of various durations, is reported in this contribution.

  5. Tumor ablations in IMRI

    Institute of Scientific and Technical Information of China (English)

    Roberto Blanco Sequeiros

    2002-01-01

    @@ IntroductionMagnetic resonance imaging based guidance control and monitoring of minimally invasive intervention has developed from a hypothetical concept to a practical possibility. Magnetic-resonance-guided interstitial therapy in principle is defined as a treatment technique for ablating deepseated tumors in the human body.

  6. Solar cell contact formation using laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    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.

  7. Ablation behavior and mechanism analysis of C/SiC composites

    Directory of Open Access Journals (Sweden)

    Yang Wang

    2016-04-01

    Full Text Available Ablation is an erosive phenomenon with removal of material by a combination of thermo-mechanical, thermo-chemical, and thermo-physical factors with high temperature, pressure, and velocity of combustion flame. Materials with outstanding thermo-mechanical and thermo-chemical properties are required for future high-temperature components. C/SiC is a kind of great potential high-temperature structural material in aeronautics and astronautics with low specific weight, high specific strength, good thermal stability, oxidation resistance and excellent resistance to ablation. In this paper, the ablation phenomenon and mechanisms were summarized adequately. The ablated surface of C/SiC composites could be divided into three regions from center to external. In general, the higher the density, the lower the ablation rate; the lower the ablation temperature and less time, the lower the ablation rate, and the preparation methods also had a great influence on the ablation property. Thermo-physical and thermo-mechanical attacks were the main ablation behavior in the center region; oxidation was the main ablation behavior in the transition region and the border oxidation region.

  8. 3D Multifunctional Ablative Thermal Protection System

    Science.gov (United States)

    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.

  9. Diagnosing Implosion Velocity and Ablator Dynamics at NIF

    Science.gov (United States)

    Grim, Gary; Hayes, Anna; Jungman, Jerry; Wilson, Doug; Wilhelmy, Jerry; Bradley, Paul; Rundberg, Bob; Cerjan, Charlie

    2009-10-01

    An enhanced understanding of the environment in a burning NIF capsule is of interest to both astrophysics and thermonuclear ignition. In this talk we introduce a new diagnostic idea, designed to measure dynamic aspects of the capsule implosion that are not currently accessible. During the burn,the NIF capsule ablator is moving relative to the 14.1 MeV dt neutrons that are traversing the capsule. The resulting neutron-ablator Doppler shift causes a few unique nuclear reactions to become sensitive detectors of the ablator velocity at peak burn time. The ``point-design'' capsule at the NIF will be based on a ^9Be ablator, and the ^9Be(n,p)^9Li reaction has an energy threshold of 14.2 MeV, making it the ideal probe. As discussed in detail below, differences in the ablator velocity lead to significant differences in the rate of ^9Li production. We present techniques for measuring this ^9Li implosion velocity diagnostic at the NIF. The same experimental techniques, measuring neutron reactions on the ablator material, will allow us to determine other important dynamical quantities, such as the areal density and approximate thickness of the ablator at peak burn.

  10. Lesion size in relation to ablation site during radiofrequency ablation

    DEFF Research Database (Denmark)

    Petersen, H H; Chen, X; Pietersen, A;

    1998-01-01

    convective cooling by induction of a flow around the electrode tip increases lesion dimensions and power consumptions. Furthermore we conclude that for the given target temperature the power consumption is positively correlated with lesion volume (p ...This study was designed to investigate the effect of the convective cooling of the tip of the ablation electrode during temperature controlled radiofrequency ablation. In vivo two different application sites in the left ventricle of anaesthetised pigs were ablated and in vitro ablation...... larger for septal applications than apical applications (p convective cooling by induction of flow yielded larger lesion volume, depth and width (p

  11. 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

    Science.gov (United States)

    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.

  12. Radiofrequency ablation of pulmonary tumors

    Energy Technology Data Exchange (ETDEWEB)

    Crocetti, Laura, E-mail: l.crocetti@med.unipi.i [Division of Diagnostic Imaging and Intervention, Department of Liver Transplants, Hepatology and Infectious Diseases, Pisa University School of Medicine (Italy); Lencioni, Riccardo [Division of Diagnostic Imaging and Intervention, Department of Liver Transplants, Hepatology and Infectious Diseases, Pisa University School of Medicine (Italy)

    2010-07-15

    The development of image-guided percutaneous techniques for local tumor ablation has been one of the major advances in the treatment of solid tumors. Among these methods, radiofrequency (RF) ablation is currently established as the primary ablative modality at most institutions. RF ablation is accepted as the best therapeutic choice for patients with early-stage hepatocellular carcinoma when liver transplantation or surgical resection are not suitable options and is considered as a viable alternate to surgery for inoperable patients with limited hepatic metastatic disease, especially from colorectal cancer. Recently, RF ablation has been demonstrated to be a safe and valuable treatment option for patients with unresectable or medically inoperable lung malignancies. Resection should remain the standard therapy for non-small cell lung cancer (NSCLC) but RF ablation may be better than conventional external-beam radiation for the treatment of the high-risk individual with NSCLC. Initial favourable outcomes encourage combining radiotherapy and RF ablation, especially for treating larger tumors. In the setting of colorectal cancer lung metastases, survival rates provided by RF ablation in selected patients, are substantially higher than those obtained with any chemotherapy regimens and provide indirect evidence that RF ablation therapy improves survival in patients with limited lung metastatic disease.

  13. Thin film growing by the laser ablation technique: possibilities for growing of dosimetric materials; Crecimiento de capas delgadas por la tecnica de ablacion laser: posibilidades para crecimiento de materiales dosimetricos

    Energy Technology Data Exchange (ETDEWEB)

    Rojas R, E.M.; Melo M, M.; Enriquez Z, E.; Fernandez G, M.; Haro P, E.; Hernandez P, J.L. [UAM-I, Laboratorio de Optica Cuantica, 09340 Mexico D.F. (Mexico)

    2005-07-01

    In this talk we will present the basics about the laser ablation technique and how it is used for thin film growing, either as a single film or a stack of thin films, as well as some methods to characterize in real time the film thickness. Finally, we will discuss the possibilities of using laser ablation for growing thin films with applications to dosimetry. (Author)

  14. Similarities and differences in ablative and non-ablative iron oxide nanoparticle hyperthermia cancer treatment

    Science.gov (United States)

    Petryk, Alicia A.; Misra, Adwiteeya; Kastner, Elliot J.; Mazur, Courtney M.; Petryk, James D.; Hoopes, P. Jack

    2015-03-01

    The use of hyperthermia to treat cancer is well studied and has utilized numerous delivery techniques, including microwaves, radio frequency, focused ultrasound, induction heating, infrared radiation, warmed perfusion liquids (combined with chemotherapy), and recently, metallic nanoparticles (NP) activated by near infrared radiation (NIR) and alternating magnetic field (AMF) based platforms. It has been demonstrated by many research groups that ablative temperatures and cytotoxicity can be produced with locally NP-based hyperthermia. Such ablative NP techniques have demonstrated the potential for success. Much attention has also been given to the fact that NP may be administered systemically, resulting in a broader cancer therapy approach, a lower level of tumor NP content and a different type of NP cancer therapy (most likely in the adjuvant setting). To use NP based hyperthermia successfully as a cancer treatment, the technique and its goal must be understood and utilized in the appropriate clinical context. The parameters include, but are not limited to, NP access to the tumor (large vs. small quantity), cancer cell-specific targeting, drug carrying capacity, potential as an ionizing radiation sensitizer, and the material properties (magnetic characteristics, size and charge). In addition to their potential for cytotoxicity, the material properties of the NP must also be optimized for imaging, detection and direction. In this paper we will discuss the differences between, and potential applications for, ablative and non-ablative magnetic nanoparticle hyperthermia.

  15. Plasma mediated ablation of biological tissues with ultrashort laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Oraevsky, A.A. [Lawrence Livermore National Lab., CA (United States)]|[Rice Univ., Houston, TX (United States). Dept. of Electrical Engineering; DaSilva, L.B.; Feit, M.D. [Lawrence Livermore National Lab., CA (United States)] [and others

    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. Thermal Performance of Ablative/ Ceramic Composite

    Directory of Open Access Journals (Sweden)

    Adriana STEFAN

    2014-12-01

    Full Text Available A hybrid thermal protection system for atmospheric earth re-entry based on ablative materials on top of ceramic matrix composites is investigated for the protection of the metallic structure in oxidative and high temperature environment of the space vehicles. The paper focuses on the joints of ablative material (carbon fiber based CALCARB® or cork based NORCOAT TM and Ceramic Matrix Composite (CMC material (carbon fibers embedded in silicon carbide matrix, Cf/SiC, SICARBON TM or C/C-SiC using commercial high temperature inorganic adhesives. To study the thermal performance of the bonded materials the joints were tested under thermal shock at the QTS facility. For carrying out the test, the sample is mounted into a holder and transferred from outside the oven at room temperature, inside the oven at the set testing temperature (1100°C, at a heating rate that was determined during the calibration stage. The dwell time at the test temperature is up to 2 min at 1100ºC at an increasing rate of temperature up to ~ 9,5°C/s. Evaluating the atmospheric re-entry real conditions we found that the most suited cooling method is the natural cooling in air environment as the materials re-entering the Earth atmosphere are subjected to similar conditions. The average weigh loss was calculated for all the samples from one set, without differentiating the adhesive used as the weight loss is due to the ablative material consumption that is the same in all the samples and is up to 2%. The thermal shock test proves that, thermally, all joints behaved similarly, the two parts withstanding the test successfully and the assembly maintaining its integrity.

  17. Radiofrequency ablation of osteoid osteoma

    NARCIS (Netherlands)

    Vanderschueren, Geert Maria Joris Michael

    2009-01-01

    The main purpose of this thesis was to evaluate the effectiveness and safety of CT-guided radiofrequency ablation for the treatment of spinal and non-spinal osteoid osteomas. Furthermore, the technical requirements needed for safe radiofrequency ablation and the clinical outcome after radiofrequency

  18. Laser ablation in analytical chemistry.

    Science.gov (United States)

    Russo, Richard E; Mao, Xianglei; Gonzalez, Jhanis J; Zorba, Vassilia; Yoo, Jong

    2013-07-02

    In 2002, we wrote an Analytical Chemistry feature article describing the Physics of Laser Ablation in Microchemical Analysis. In line with the theme of the 2002 article, this manuscript discusses current issues in fundamental research, applications based on detecting photons at the ablation site (LIBS and LAMIS) and by collecting particles for excitation in a secondary source (ICP), and directions for the technology.

  19. Radiofrequency ablation of atrial fibrillation

    NARCIS (Netherlands)

    Wiesfeld, ACP; Tan, ES; Van Veldhuisen, DJ; Crijns, HJGM; Van Gelder, IC

    2004-01-01

    Twenty-five patients (16 males, mean age 46 years.) underwent radiofrequency ablation because of either paroxysmal (13 patients) or persistent atrial fibrillation (12 patients). Ablation aimed at earliest activation of spontaneous and catheter-induced repetitive ectopy in left and right atria and ap

  20. Simulation of Pellet Ablation

    Science.gov (United States)

    Parks, P. B.; Ishizaki, Ryuichi

    2000-10-01

    In order to clarify the structure of the ablation flow, 2D simulation is carried out with a fluid code solving temporal evolution of MHD equations. The code includes electrostatic sheath effect at the cloud interface.(P.B. Parks et al.), Plasma Phys. Contr. Fusion 38, 571 (1996). An Eulerian cylindrical coordinate system (r,z) is used with z in a spherical pellet. The code uses the Cubic-Interpolated Psudoparticle (CIP) method(H. Takewaki and T. Yabe, J. Comput. Phys. 70), 355 (1987). that divides the fluid equations into non-advection and advection phases. The most essential element of the CIP method is in calculation of the advection phase. In this phase, a cubic interpolated spatial profile is shifted in space according to the total derivative equations, similarly to a particle scheme. Since the profile is interpolated by using the value and the spatial derivative value at each grid point, there is no numerical oscillation in space, that often appears in conventional spline interpolation. A free boundary condition is used in the code. The possibility of a stationary shock will also be shown in the presentation because the supersonic ablation flow across the magnetic field is impeded.

  1. Ablation characteristics of electrospun core-shell nanofiber by femtosecond laser.

    Science.gov (United States)

    Park, ChangKyoo; Xue, Ruipeng; Lannutti, John J; Farson, Dave F

    2016-08-01

    This study examined the femtosecond laser ablation properties of core and shell polymers their relationship to the ablation characteristics of core-shell nanofibers. The single-pulse ablation threshold of bulk polycaprolactone (PCL) was measured to be 2.12J/cm(2) and that of bulk polydimethylsiloxane (PDMS) was 4.07J/cm(2). The incubation coefficients were measured to be 0.82±0.02 for PCL and 0.53±0.03 for PDMS. PDMS-PCL core-shell and pure PCL nanofibers were fabricated by electrospinning. The energy/volume of pure PCL and PDMS-PCL core-shell nanofiber ablation was investigated by measuring linear ablation grooves made at different scanning speeds. At large scanning speed, higher energy/volume was required for machining PDMS-PCL nanofiber than for PCL nanofiber. However, at small scanning speed, comparable energy/volume was measured for PDMS-PCL and PCL nanofiber ablation. Additionally, in linear scanned ablation of PDMS-PCL fibers at small laser pulse energy and large scanning speed, there were partially ablated fibers where the shell was ablated but the core remained. This was attributed to the lower ablation threshold of the shell material.

  2. Increasing the penetration depth for ultrafast laser tissue ablation using glycerol based optical clearing

    Science.gov (United States)

    Gabay, Ilan; Subramanian, Kaushik G.; Martin, Chris; Yildirim, Murat; Tuchin, Valery V.; Ben-Yakar, Adela

    2016-03-01

    Background: Deep tissue ablation is the next challenge in ultrafast laser microsurgery. By focusing ultrafast pulses below the tissue surface one can create an ablation void confined to the focal volume. However, as the ablation depth increases in a scattering tissue, increase in the required power can trigger undesired nonlinear phenomena out of focus that restricts our ability to ablate beyond a maximum ablation depth of few scattering lengths. Optical clearing (OC) might reduce the intensity and increase the maximal ablation depth by lowering the refractive index mismatch, and therefore reducing scattering. Some efforts to ablate deeper showed out of focus damage, while others used brutal mechanical methods for clearing. Our clinical goal is to create voids in the scarred vocal folds and inject a biomaterial to bring back the tissue elasticity and restore phonation. Materials and methods: Fresh porcine vocal folds were excised and applied a biocompatible OC agent (75% glycerol). Collimated transmittance was monitored. The tissue was optically cleared and put under the microscope for ablation threshold measurements at different depths. Results: The time after which the tissue was optically cleared was roughly two hours. Fitting the threshold measurements to an exponential decay graph indicated that the scattering length of the tissue increased to 83+/-16 μm, which is more than doubling the known scattering length for normal tissue. Conclusion: Optical clearing with Glycerol increases the tissue scattering length and therefore reduces the energy for ablation and increases the maximal ablation depth. This technique can potentially improve clinical microsurgery.

  3. The physical processes of the metallic materials in nanosecond laser ablation%纳秒激光脉冲烧蚀金属铜的物理过程分析

    Institute of Scientific and Technical Information of China (English)

    陶淑芬

    2011-01-01

    In order to study the effect of laser irradiation on metal target material,it is analyzed the ablation process and the surface characteristics of metal materials analysis under the action of nanosecond laser pulse.The research shows that the heat deposited of nanosecond laser pulse in the metal surface is very thin(several micrometers),the temperature distribution from the outside to inside can be divided into superheated liquid,vaporization and melting state.Due to the rapid heat deposition of laser pulse,explosive boiling(phase explosion) will occur and deep pits will be formed.At the same time,the metal vapor will cooled around the hole and form a discoloration area.In the role of the region,the periodic ripple structure will be formed due to thermal tension.In this process,the role of laser plasma shock accelerated the discharge of vaporized material.%为了研究强激光辐照金属靶材料的效应,用纳秒激光脉冲烧蚀金属铜,对表面特征进行观测以及对其物理过程进行分析。研究发现:纳秒激光脉冲对金属铜作用时,热量沉积在金属表面很薄(几个微米)的范围,使得其温度分布由外到内分别为超热、汽化和熔化状态,由于激光脉冲的快速沉积,会发生剧烈的沸腾性爆炸(相爆炸)效应,形成较深的坑状破坏,同时汽化物在点坑周围再冷却,形成色变区。在熔化区域由于热张力作用,形成周期性波纹结构。在这个过程中,激光等离子体的冲击作用加速了汽化物的排出。

  4. Ultrafast properties of femtosecond-laser-ablated GaAs and its application to terahertz optoelectronics.

    Science.gov (United States)

    Madéo, Julien; Margiolakis, Athanasios; Zhao, Zhen-Yu; Hale, Peter J; Man, Michael K L; Zhao, Quan-Zhong; Peng, Wei; Shi, Wang-Zhou; Dani, Keshav M

    2015-07-15

    We report on the first terahertz (THz) emitter based on femtosecond-laser-ablated gallium arsenide (GaAs), demonstrating a 65% enhancement in THz emission at high optical power compared to the nonablated device. Counter-intuitively, the ablated device shows significantly lower photocurrent and carrier mobility. We understand this behavior in terms of n-doping, shorter carrier lifetime, and enhanced photoabsorption arising from the ablation process. Our results show that laser ablation allows for efficient and cost-effective optoelectronic THz devices via the manipulation of fundamental properties of materials.

  5. Femtosecond laser bone ablation with a high repetition rate fiber laser source.

    Science.gov (United States)

    Mortensen, Luke J; Alt, Clemens; Turcotte, Raphaël; Masek, Marissa; Liu, Tzu-Ming; Côté, Daniel C; Xu, Chris; Intini, Giuseppe; Lin, Charles P

    2015-01-01

    Femtosecond laser pulses can be used to perform very precise cutting of material, including biological samples from subcellular organelles to large areas of bone, through plasma-mediated ablation. The use of a kilohertz regenerative amplifier is usually needed to obtain the pulse energy required for ablation. This work investigates a 5 megahertz compact fiber laser for near-video rate imaging and ablation in bone. After optimization of ablation efficiency and reduction in autofluorescence, the system is demonstrated for the in vivo study of bone regeneration. Image-guided creation of a bone defect and longitudinal evaluation of cellular injury response in the defect provides insight into the bone regeneration process.

  6. Thermal melting and ablation of silicon by femtosecond laser radiation

    Energy Technology Data Exchange (ETDEWEB)

    Ionin, A. A.; Kudryashov, S. I., E-mail: sikudr@lebedev.ru; Seleznev, L. V.; Sinitsyn, D. V. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Bunkin, A. F.; Lednev, V. N.; Pershin, S. M. [Russian Academy of Sciences, General Physics Institute (Russian Federation)

    2013-03-15

    The space-time dynamics of thermal melting, subsurface cavitation, spallative ablation, and fragmentation ablation of the silicon surface excited by single IR femtosecond laser pulses is studied by timeresolved optical reflection microscopy. This dynamics is revealed by monitoring picosecond and (sub)nanosecond oscillations of probe pulse reflection, which is modulated by picosecond acoustic reverberations in the dynamically growing surface melt subjected to ablation and having another acoustic impedance, and by optical interference between the probe pulse replicas reflected by the spalled layer surface and the layer retained on the target surface. The acoustic reverberation periods change during the growth and ablation of the surface melt film, which makes it possible to quantitatively estimate the contributions of these processes to the thermal dynamics of the material surface. The results on the thermal dynamics of laser excitation are supported by dynamic measurements of the ablation parameters using noncontact ultrasonic diagnostics, scanning electron microscopy, atomic force microscopy, and optical interference microscopy of the modified regions appearing on the silicon surface after ablation.

  7. The effect of asteroid topography on surface ablation deflection

    Science.gov (United States)

    McMahon, Jay W.; Scheeres, Daniel J.

    2017-02-01

    Ablation techniques for deflecting hazardous asteroids deposit energy into the asteroid's surface, causing an effective thrust on the asteroid as the ablating material leaves normal to the surface. Although it has long been recognized that surface topography plays an important role in determining the deflection capabilities, most studies to date have ignored this aspect of the model. This paper focuses on understanding the topography for real asteroid shapes, and how this topography can change the deflection performance of an ablation technique. The near Earth asteroids Golevka, Bennu, and Itokawa are used as the basis for this study, as all three have high-resolution shape models available. This paper shows that naive targeting of an ablation method without accounting for the surface topography can lower the deflection performance by up to 20% in the cases studied in terms of the amount of acceleration applied in the desired direction. If the ablation thrust level is assumed to be 100 N, as used elsewhere in the literature, this misapplication of thrust translates to tens of kilometers per year in decreased semimajor axis change. However, if the ablation method can freely target any visible point on the surface of the asteroid, almost all of this performance can be recovered.

  8. EUV ablation of organic polymers at a high fluence

    Institute of Scientific and Technical Information of China (English)

    Chiara; Liberatore; Klaus; Mann; Matthias; Mller; Ladislav; Pina; Libor; Juha; Jorge; J.Rocca; Akira; Endo; Tomas; Mocek

    2014-01-01

    A preliminary investigation on short-wavelength ablation mechanisms of poly(methyl methacrylate)(PMMA) and poly(1,4-phenylene ether ether-sulfone)(PPEES) by extreme ultraviolet(EUV) radiation at 13.5 nm using a table-top laserproduced plasma from a gas-puff target at LLG(Gttingen) and at 46.9 nm by a 10 Hz desktop capillary discharge laser operated at the Institute of Physics(Prague) is presented.Ablation of polymer materials is initiated by photoinduced polymer chain scissions.The ablation occurs due to the formation of volatile products by the EUV radiolysis removed as an ablation plume from the irradiated material into the vacuum.In general,cross-linking of polymer molecules can compete with the chain decomposition.Both processes may influence the efficiency and quality of micro(nano)structuring in polymer materials.Wavelength is a critical parameter to be taken into account when an EUV ablation process occurs,because different wavelengths result in different energy densities in the near-surface region of the polymer exposed to nanosecond pulses of intense EUV radiation.

  9. Radiofrequency Ablation for the Treatment of Hepatocellular Carcinoma in Patients with Transjugular Intrahepatic Portosystemic Shunts

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jonathan K., E-mail: jonathan.park09@gmail.com [David Geffen School of Medicine at UCLA, Department of Radiology (United States); Al-Tariq, Quazi Z., E-mail: qat200@gmail.com [Stanford University School of Medicine, Department of Radiology (United States); Zaw, Taryar M., E-mail: taryar.zaw@gmail.com; Raman, Steven S., E-mail: sraman@mednet.ucla.edu; Lu, David S.K., E-mail: dlu@mednet.ucla.edu [David Geffen School of Medicine at UCLA, Department of Radiology (United States)

    2015-10-15

    PurposeTo assess radiofrequency (RF) ablation efficacy, as well as the patency of transjugular intrahepatic portosystemic shunts (TIPSs), in patients with hepatocellular carcinoma (HCC).Materials and MethodsRetrospective database review of patients with pre-existing TIPS undergoing RF ablation of HCC was conducted over a 159-month period ending in November 2013. TIPS patency pre- and post-RF ablation was assessed by ultrasound, angiography, and/or contrast-enhanced CT or MRI. Patient demographics and immediate post-RF ablation outcomes and complications were also reviewed.Results19 patients with 21 lesions undergoing 25 RF ablation sessions were included. Child-Pugh class A, B, and C scores were seen in 1, 13, and 5 patients, respectively. Eleven patients (58 %) ultimately underwent liver transplantation. Immediate technical success was seen in all ablation sessions without residual tumor enhancement (100 %). No patients (0 %) suffered liver failure within 1 month of ablation. Pre-ablation TIPS patency was demonstrated in 22/25 sessions (88 %). Of 22 cases with patent TIPS prior to ablation, post-ablation patency was demonstrated in 22/22 (100 %) at immediate post-ablation imaging and in 21/22 (95 %) at last follow-up (1 patient was incidentally noted to have occlusion 31 months later). No immediate complications were observed.ConclusionAblation efficacy was similar to the cited literature values for patients without TIPS. Furthermore, TIPS patency was preserved in the majority of cases. Patients with both portal hypertension and HCC are not uncommonly encountered, and a pre-existing TIPS does not appear to be a definite contraindication for RF ablation.

  10. Radiative Ablation of Disks Around Massive Stars

    CERN Document Server

    Kee, N D

    2015-01-01

    Hot, massive stars (spectral types O and B) have extreme luminosities ($10^4 -10^6 L_\\odot$) 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...

  11. A comparison of the characteristics of excimer and femtosecond laser ablation of acrylonitrile butadiene styrene (ABS)

    Science.gov (United States)

    See, Tian Long; Liu, Zhu; Li, Lin; Zhong, Xiang Li

    2016-02-01

    This paper presents an investigation on the ablation characteristics of excimer laser (λ = 248 nm, τ = 15 ns) and femtosecond laser (λ = 800 nm, τ = 100 fs) on ABS polymer sheets. The laser-material interaction parameters (ablation threshold, optical penetration depth and incubation factor) and the changes in material chemical properties were evaluated and compared between the two lasers. The work shows that the ablation threshold and effective optical penetration depth values are dependent on the wavelength of laser beam (photon energy) and the pulse width. The ablation threshold value is lower for the excimer laser ablation of ABS (Fth = 0.087 J/cm2) than that for the femtosecond laser ablation of ABS (Fth = 1.576 J/cm2), demonstrating a more dominating role of laser wavelength than the pulse width in influencing the ablation threshold. The ablation depth versus the logarithmic scale of laser fluence shows two linear regions for the fs laser ablation, not previously known for polymers. The effective optical penetration depth value is lower for excimer laser ablation (α-1 = 223 nm) than that for femtosecond laser ablation (α-1 = 2917 nm). The ablation threshold decreases with increasing number of pulses (NOP) due to the chain scission process that shortens the polymeric chains, resulting in a weaker polymeric configuration and the dependency is governed by the incubation factor. Excimer laser treatment of ABS eliminates the Cdbnd C bond completely through the chain scission process whereas Cdbnd C bond is partially eliminated through the femtosecond laser treatment due to the difference in photon energy of the two laser beams. A reduction in the Cdbnd C bond through the chain scission process creates free radical carbons which then form crosslinks with each other or react with oxygen, nitrogen and water in air producing oxygen-rich (Csbnd O and Cdbnd O bond) and nitrogen-rich (Csbnd N) functional groups.

  12. Diagnosing implosion velocity and ablator dynamics at NIF (u)

    Energy Technology Data Exchange (ETDEWEB)

    Hayes, Anna [Los Alamos National Laboratory; Grim, Gary [Los Alamos National Laboratory; Jungnam, Jerry [Los Alamos National Laboratory; Bradley, Paul [Los Alamos National Laboratory; Rundberg, Bob [Los Alamos National Laboratory; Wilhelmy, Jerry [Los Alamos National Laboratory; Wilson, Doug [Los Alamos National Laboratory

    2009-07-09

    An enhanced understanding of the unique physics probed in a burning NIP capsule is important for both nuclear weapons physics and thermonuclear ignition. In this talk we introduce a new diagnostic idea, designed to measure dynamic aspects of the capsule implosion that are not currently accessible. The current set of diagnostics for the NIF experiments includes reaction history (a time resolved measure of the d + t burn), neutron time-of-flight and spectrometry and spatial imaging of the neutron production and scattering. Although valuable, this abbreviated set of diagnostics cannot determine key dynamical properties of the implosion, such as implosion velocity (v{sub impl}) and ablator thickness. To surpass the present limits of {approx} 10{sup 15} d+t reactions, it will be necessary to increase significantly the implosion energy delivered to the DT fuel by finely tuning the balance between the remaining (imploding) ablator mass and velocity. If too much mass remains, the implosion velocity will be too slow, and the subsecpwnt PdV work will not be sufficient to overcome cooling via conduction and radiation. If too little mass remains, hydrodynamic instabilities will occur, resulting in unpredictable and degraded performance. Detailed calculations suggest the ablator must reach an implosion velocity of 3-4 x 10{sup 7} cm/sec and an areal density of {rho}{Delta}R {approx}200 mg/cm{sup 2} in order to achieve ignition. The authors present a new scheme to measure these important quantities using neutron reactions on the ablator material. During the burn, the ablator is moving relative to the 14.1 MeV d+t neutrons that are traversing the capsule. The resulting neutron-ablator Doppler shift causes a few unique nuclear reactions to become sensitive detectors of the ablator velocity at peak burn time. The 'point-design' capsule at the NIF will be based on a {sup 9}Be ablator, and the {sup 9}Be(n,p){sup 9}Li reaction has an energy threshold of 14.2 MeV, making it

  13. Magnetic and robotic navigation for catheter ablation: "joystick ablation".

    Science.gov (United States)

    Ernst, Sabine

    2008-10-01

    Catheter ablation has become the treatment of choice to cure various arrhythmias in the last decades. The newest advancement of this general concept is made on the navigation ability using remote-controlled ablation catheters. This review summarizes the concept of the two currently available systems, followed by a critical review of the published clinical reports for each system, respectively. Despite the limited amount of data, an attempt to compare the two systems is made.

  14. Fractional ablative erbium YAG laser

    DEFF Research Database (Denmark)

    Taudorf, Elisabeth H; Haak, Christina S; Erlendsson, Andrés M

    2014-01-01

    BACKGROUND AND OBJECTIVES: Treatment of a variety of skin disorders with ablative fractional lasers (AFXL) is driving the development of portable AFXLs. This study measures micropore dimensions produced by a small 2,940 nm AFXL using a variety of stacked pulses, and determines a model correlating...... laser parameters with tissue effects. MATERIALS AND METHODS: Ex vivo pig skin was exposed to a miniaturized 2,940 nm AFXL, spot size 225 µm, density 5%, power levels 1.15-2.22 W, pulse durations 50-225 microseconds, pulse repetition rates 100-500 Hz, and 2, 20, or 50 stacked pulses, resulting in pulse...... 190 to 347 µm. CONCLUSIONS: Pulse stacking with a small, low power 2,940 nm AFXL created reproducible shallow to deep micropores, and influenced micropore configuration. Mathematical modeling established relations between laser settings and micropore dimensions, which assists in choosing laser...

  15. Interfacial Design of Composite Ablative Materials Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This Phase I Small Business Innovative Research project proposes to develop a multiscale computational methodology capable of accurate prediction of the properties...

  16. Field enhancement induced laser ablation

    DEFF Research Database (Denmark)

    Fiutowski, Jacek; Maibohm, Christian; Kjelstrup-Hansen, Jakob

    Sub-diffraction spatially resolved, quantitative mapping of strongly localized field intensity enhancement on gold nanostructures via laser ablation of polymer thin films is reported. Illumination using a femtosecond laser scanning microscope excites surface plasmons in the nanostructures...

  17. Radiofrequency Ablation in Barrett's Esophagus

    Directory of Open Access Journals (Sweden)

    Vani J.A. Konda

    2014-01-01

    Full Text Available Radiofrequency ablation (RFA is an endoscopic modality used in the treatment of Barrett's esophagus. RFA may be performed using a balloon-based catheter or using one of the probe catheters that attaches to the distal end of the endoscope. Here we demonstrate step-by-step instruction in using radiofrequency ablation in the treatment of Barrett's esophagus and highlight key concepts in the technique.

  18. Ablative Approaches for Pulmonary Metastases.

    Science.gov (United States)

    Boyer, Matthew J; Ricardi, Umberto; Ball, David; Salama, Joseph K

    2016-02-01

    Pulmonary metastases are common in patients with cancer for which surgery is considered a standard approach in appropriately selected patients. A number of patients are not candidates for surgery due to a medical comorbidities or the extent of surgery required. For these patients, noninvasive or minimally invasive approaches to ablate pulmonary metastases are potential treatment strategies. This article summarizes the rationale and outcomes for non-surgical treatment approaches, including radiotherapy, radiofrequency and microwave ablation, for pulmonary metastases.

  19. A comparison of the characteristics of excimer and femtosecond laser ablation of acrylonitrile butadiene styrene (ABS)

    Energy Technology Data Exchange (ETDEWEB)

    See, Tian Long, E-mail: tianlong.see@postgrad.manchester.ac.uk [Corrosion and Protection Centre, School of Materials, The Mill, The University of Manchester, M13 9PL Manchester (United Kingdom); Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, M13 9PL Manchester (United Kingdom); Liu, Zhu [Corrosion and Protection Centre, School of Materials, The Mill, The University of Manchester, M13 9PL Manchester (United Kingdom); Li, Lin [Laser Processing Research Centre, School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, M13 9PL Manchester (United Kingdom); Zhong, Xiang Li [Corrosion and Protection Centre, School of Materials, The Mill, The University of Manchester, M13 9PL Manchester (United Kingdom)

    2016-02-28

    Highlights: • Ablation threshold for excimer laser is lower compared to femtosecond laser. • Effective optical penetration depth for excimer laser is lower compared to femtosecond laser. • Two ablation characteristic regimes are observed for femtosecond laser ablation. • Reduction of C=C bond following excimer or fs laser ablation is observed. • Addition of oxygen- and nitrogen-rich functional groups is observed. - Abstract: This paper presents an investigation on the ablation characteristics of excimer laser (λ = 248 nm, τ = 15 ns) and femtosecond laser (λ = 800 nm, τ = 100 fs) on ABS polymer sheets. The laser–material interaction parameters (ablation threshold, optical penetration depth and incubation factor) and the changes in material chemical properties were evaluated and compared between the two lasers. The work shows that the ablation threshold and effective optical penetration depth values are dependent on the wavelength of laser beam (photon energy) and the pulse width. The ablation threshold value is lower for the excimer laser ablation of ABS (F{sub th} = 0.087 J/cm{sup 2}) than that for the femtosecond laser ablation of ABS (F{sub th} = 1.576 J/cm{sup 2}), demonstrating a more dominating role of laser wavelength than the pulse width in influencing the ablation threshold. The ablation depth versus the logarithmic scale of laser fluence shows two linear regions for the fs laser ablation, not previously known for polymers. The effective optical penetration depth value is lower for excimer laser ablation (α{sup −1} = 223 nm) than that for femtosecond laser ablation (α{sup −1} = 2917 nm). The ablation threshold decreases with increasing number of pulses (NOP) due to the chain scission process that shortens the polymeric chains, resulting in a weaker polymeric configuration and the dependency is governed by the incubation factor. Excimer laser treatment of ABS eliminates the C=C bond completely through the chain scission process whereas

  20. Evaluation of the analytical capability of NIR femtosecond laser ablation-inductively coupled plasma mass spectrometry.

    Science.gov (United States)

    Hirata, Takafumi; Kon, Yoshiaki

    2008-03-01

    A laser ablation-inductively coupled plasma-mass spectrometric (LA-ICPMS) technique utilizing a titanium-sapphire (TiS) femtosecond laser (fs-laser) has been developed for elemental and isotopic analysis. The signal intensity profile, depth of the ablation pit and level of elemental fractionation were investigated in order to evaluate the analytical capability of the present fs-laser ablation-ICPMS technique. The signal intensity profile of (57)Fe, obtained from iron sulfide (FeS(2)), demonstrated that the resulting signal intensity of (57)Fe achieved by the fs-laser ablation was almost 4-times higher than that obtained by ArF excimer laser ablation under a similar energy fluence (5 J/cm(2)). In fs-laser ablation, there is no significant difference in a depth of the ablation pit between glass and zircon material, while in ArF laser ablation, the resulting crater depth on the zircon crystal was almost half the level than that obtained for glass material. Both the thermal-induced and particle size-related elemental fractionations, which have been thought to be main sources of analytical error in the LA-ICPMS analysis, were measured on a Harvard 91500 zircon crystal. The resulting fractionation indexes on the (206)Pb/(238)U (f(Pb/U)) and (238)U/(232)Th (f(U/Th)) ratios obtained by the present fs-laser ablation system were significantly smaller than those obtained by a conventional ArF excimer laser ablation system, demonstrative of smaller elemental fractionation. Using the present fs-laser ablation technique, the time profile of the signal intensity of (56)Fe and the isotopic ratios ((57)Fe/(54)Fe and (56)Fe/(54)Fe) have been measured on a natural pyrite (FeS(2)) sample. Repeatability in signal intensity of (56)Fe achieved by the fs-laser ablation system was significantly better than that obtained by ArF excimer laser ablation. Moreover, the resulting precision in (57)Fe/(54)Fe and (56)Fe/(54)Fe ratio measurements could be improved by the fs-laser ablation system

  1. Formation of nanostructures under femtosecond laser ablation of metals

    Energy Technology Data Exchange (ETDEWEB)

    Ashitkov, S I; Romashevskii, S A; Komarov, P S; Burmistrov, A A; Agranat, M B [Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow (Russian Federation); Zhakhovskii, V V [All-Russian Institute of Automatics, Moscow (Russian Federation); Inogamov, N A [Landau Institute for Theoretical Physics, Russian Academy of Sciences, Chernogolovka, Moscow region (Russian Federation)

    2015-06-30

    We present the results of studying the morphology of the modified surface of aluminium, nickel and tantalum after ablation of the surface layer by a femtosecond laser pulse. The sizes of characteristic elements of a cellular nanostructure are found to correlate with thermo-physical properties of the material and the intensity of laser radiation. (superstrong light fields)

  2. Effect of air-flow on the evaluation of refractive surgery ablation patterns.

    Science.gov (United States)

    Dorronsoro, Carlos; Schumacher, Silvia; Pérez-Merino, Pablo; Siegel, Jan; Mrochen, Michael; Marcos, Susana

    2011-02-28

    An Allegretto Eye-Q laser platform (Wavelight GmbH, Erlangen, Germany) was used to study the effect of air-flow speed on the ablation of artificial polymer corneas used for testing refractive surgery patterns. Flat samples of two materials (PMMA and Filofocon A) were ablated at four different air flow conditions. The shape and profile of the ablated surfaces were measured with a precise non-contact optical surface profilometer. Significant asymmetries in the measured profiles were found when the ablation was performed with the clinical air aspiration system, and also without air flow. Increasing air-flow produced deeper ablations, improved symmetry, and increased the repeatability of the ablation pattern. Shielding of the laser pulse by the plume of smoke during the ablation of plastic samples reduced the central ablation depth by more than 40% with no-air flow, 30% with clinical air aspiration, and 5% with 1.15 m/s air flow. A simple model based on non-inertial dragging of the particles by air flow predicts no central shielding with 2.3 m/s air flow, and accurately predicts (within 2 μm) the decrease of central ablation depth by shielding. The shielding effects for PMMA and Filofocon A were similar despite the differences in the ablation properties of the materials and the different full-shielding transmission coefficient, which is related to the number of particles ejected and their associated optical behavior. Air flow is a key factor in the evaluation of ablation patterns in refractive surgery using plastic models, as significant shielding effects are found with typical air-flow levels used under clinical conditions. Shielding effects can be avoided by tuning the air flow to the laser repetition rate.

  3. Thermal-mechanical modeling of laser ablation hybrid machining

    Science.gov (United States)

    Matin, Mohammad Kaiser

    2001-08-01

    Hard, brittle and wear-resistant materials like ceramics pose a problem when being machined using conventional machining processes. Machining ceramics even with a diamond cutting tool is very difficult and costly. Near net-shape processes, like laser evaporation, produce micro-cracks that require extra finishing. Thus it is anticipated that ceramic machining will have to continue to be explored with new-sprung techniques before ceramic materials become commonplace. This numerical investigation results from the numerical simulations of the thermal and mechanical modeling of simultaneous material removal from hard-to-machine materials using both laser ablation and conventional tool cutting utilizing the finite element method. The model is formulated using a two dimensional, planar, computational domain. The process simulation acronymed, LAHM (Laser Ablation Hybrid Machining), uses laser energy for two purposes. The first purpose is to remove the material by ablation. The second purpose is to heat the unremoved material that lies below the ablated material in order to ``soften'' it. The softened material is then simultaneously removed by conventional machining processes. The complete solution determines the temperature distribution and stress contours within the material and tracks the moving boundary that occurs due to material ablation. The temperature distribution is used to determine the distance below the phase change surface where sufficient ``softening'' has occurred, so that a cutting tool may be used to remove additional material. The model incorporated for tracking the ablative surface does not assume an isothermal melt phase (e.g. Stefan problem) for laser ablation. Both surface absorption and volume absorption of laser energy as function of depth have been considered in the models. LAHM, from the thermal and mechanical point of view is a complex machining process involving large deformations at high strain rates, thermal effects of the laser, removal of

  4. Enthalpy model for heating, melting, and vaporization in laser ablation

    Directory of Open Access Journals (Sweden)

    Vasilios Alexiades

    2010-09-01

    Full Text Available Laser ablation is used in a growing number of applications in various areas including medicine, archaeology, chemistry, environmental and materials sciences. In this work the heat transfer and phase change phenomena during nanosecond laser ablation of a copper (Cu target in a helium (He background gas at atmospheric pressure are presented. An enthalpy model is outlined, which accounts for heating, melting, and vaporization of the target. As far as we know, this is the first model that connects the thermodynamics and underlying kinetics of this challenging phase change problem in a self-consistent way.

  5. Plan for PLEX X-Ray Ablation Experiments and Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Latkowski, J F; Reyes, S

    2001-09-27

    PLEX is a Z-pinch based x-ray source that can produce x-rays with fluences (0.3-18 J/cm{sup 2}), pulselengths (10-30 ns), repetition rates (<10 Hz), and energies (50-500 eV) of interest for IFE chambers and optics. It provides an affordable, dedicated method to advance our understanding of x-ray damage to materials. The PLEX x-ray source will be used to experimentally validate and further develop the ABLATOR x-ray ablation code for use in inertial fusion energy (IFE) studies.

  6. Electrophysiological properties and the results of catheter ablation of symptomatic atrial tachyarrhythmia after surgical ablation of atrial fibrillation

    OpenAIRE

    Bockeria L.A.; Bockeria O.L.; Sergeev A.V.; Melikulov A.Kh.; Klimchuk I.Ya.; Temirbulatov I.A.; Fatulaev Z.F.

    2016-01-01

    Objective. To characterize electrophysiological properties of postablational arrhythmia and to assess shortand long-term efficacy of catheter radiofrequency ablation of these arrhythmias. Material and methods. We analyzed retrospectively 20 consecutive patients with highly symptomatic postsurgical atrial arrhythmia operated on valvular heart disease in conjunction with paroxysmal, persistent, longstanding persistent and permanent forms of atrial fibrillation during 2010–2013. Medi...

  7. Esophageal papilloma: Flexible endoscopic ablation byradiofrequency

    Institute of Scientific and Technical Information of China (English)

    Gianmattia del Genio; Federica del Genio; Pietro Schettino; Paolo Limongelli; Salvatore Tolone; Luigi Brusciano; Manuela Avellino; Chiara Vitiello; Giovanni Docimo; Angelo Pezzullo; Ludovico Docimo

    2015-01-01

    Squamous papilloma of the esophagus is a rare benignlesion of the esophagus. Radiofrequency ablation is anestablished endoscopic technique for the eradication ofBarrett esophagus. No cases of endoscopic ablation ofesophageal papilloma by radiofrequency ablation (RFA)have been reported. We report a case of esophagealpapilloma successfully treated with a single sessionof radiofrequency ablation. Endoscopic ablation ofthe lesion was achieved by radiofrequency using anew catheter inserted through the working channelof endoscope. The esophageal ablated tissue wasremoved by a specifically designed cup. Completeablation was confirmed at 3 mo by endoscopy withbiopsies. This case supports feasibility and safety of asa new potential indication for BarrxTM RFA in patientswith esophageal papilloma.

  8. Insights into secondary reactions occurring during atmospheric ablation of micrometeoroids

    Science.gov (United States)

    Court, Richard W.; Tan, Jonathan

    2016-06-01

    Ablation of micrometeoroids during atmospheric entry yields volatile gases such as water, carbon dioxide, and sulfur dioxide, capable of altering atmospheric chemistry and hence the climate and habitability of the planetary surface. While laboratory experiments have revealed the yields of these gases during laboratory simulations of ablation, the reactions responsible for the generation of these gases have remained unclear, with a typical assumption being that species simply undergo thermal decomposition without engaging in more complex chemistry. Here, pyrolysis-Fourier transform infrared spectroscopy reveals that mixtures of meteorite-relevant materials undergo secondary reactions during simulated ablation, with organic matter capable of taking part in carbothermic reduction of iron oxides and sulfates, resulting in yields of volatile gases that differ from those predicted by simple thermal decomposition. Sulfates are most susceptible to carbothermic reduction, producing greater yields of sulfur dioxide and carbon dioxide at lower temperatures than would be expected from simple thermal decomposition, even when mixed with meteoritically relevant abundances of low-reactivity Type IV kerogen. Iron oxides were less susceptible, with elevated yields of water, carbon dioxide, and carbon monoxide only occurring when mixed with high abundances of more reactive Type III kerogen. We use these insights to reinterpret previous ablation simulation experiments and to predict the reactions capable of occurring during ablation of carbonaceous micrometeoroids in atmospheres of different compositions.

  9. Feasibility evaluation of the monolithic braided ablative nozzle

    Science.gov (United States)

    Director, Mark N.; McPherson, Douglass J., Sr.

    1992-02-01

    The feasibility of the monolithic braided ablative nozzle was evaluated as part of an independent research and development (IR&D) program complementary to the National Aeronautics and Space Administration/Marshall Space Flight Center (NASA/MSFC) Low-Cost, High-Reliability Case, Insulation and Nozzle for Large Solid Rocket Motors (LOCCIN) Program. The monolithic braided ablative nozzle is a new concept that utilizes a continuous, ablative, monolithic flame surface that extends from the nozzle entrance, through the throat, to the exit plane. The flame surface is fabricated using a Through-the-Thickness braided carbon-fiber preform, which is impregnated with a phenolic or phenolic-like resin. During operation, the braided-carbon fiber/resin material ablates, leaving the structural backside at temperatures which are sufficiently low to preclude the need for any additional insulative materials. The monolithic braided nozzle derives its potential for low life cycle cost through the use of automated processing, one-component fabrication, low material scrap, low process scrap, inexpensive raw materials, and simplified case attachment. It also has the potential for high reliability because its construction prevents delamination, has no nozzle bondlines or leak paths along the flame surface, is amenable to simplified analysis, and is readily inspectable. In addition, the braided construction has inherent toughness and is damage-tolerant. Two static-firing tests were conducted using subscale, 1.8 - 2.0-inch throat diameter, hardware. Tests were approximately 15 seconds in duration, using a conventional 18 percent aluminum/ammonium perchlorate propellant. The first of these tests evaluated the braided ablative as an integral backside insulator and exit cone; the second test evaluated the monolithic braided ablative as an integral entrance/throat/exit cone nozzle. Both tests met their objectives. Radial ablation rates at the throat were as predicted, approximately 0.017 in

  10. Percutaneous Renal Tumor Ablation: Radiation Exposure During Cryoablation and Radiofrequency Ablation

    Energy Technology Data Exchange (ETDEWEB)

    McEachen, James C., E-mail: james.mceachen2@gmail.com [Mayo Clinic, Division of Preventive, Occupational, and Aerospace Medicine (United States); Leng, Shuai; Atwell, Thomas D. [Mayo Clinic, Department of Radiology (United States); Tollefson, Matthew K. [Mayo Clinic, Department of Urology (United States); Friese, Jeremy L. [Mayo Clinic, Department of Radiology (United States); Wang, Zhen; Murad, M. Hassan [Mayo Clinic, Division of Preventive, Occupational, and Aerospace Medicine (United States); Schmit, Grant D. [Mayo Clinic, Department of Radiology (United States)

    2016-02-15

    IntroductionOnce reserved solely for non-surgical cases, percutaneous ablation is becoming an increasingly popular treatment option for a wider array of patients with small renal masses and the radiation risk needs to be better defined as this transition continues.Materials and MethodsRetrospective review of our renal tumor ablation database revealed 425 patients who underwent percutaneous ablation for treatment of 455 renal tumors over a 5-year time period. Imparted radiation dose information was reviewed for each procedure and converted to effective patient dose and skin dose using established techniques. Statistical analysis was performed with each ablative technique.ResultsFor the 331 cryoablation procedures, the mean DLP was 6987 mGycm (SD = 2861) resulting in a mean effective dose of 104.7 mSv (SD = 43.5) and the mean CTDI{sub vol} was 558 mGy (SD = 439) resulting in a mean skin dose of 563.2 mGy (SD = 344.1). For the 124 RFA procedures, the mean DLP was 3485 mGycm (SD = 1630) resulting in a mean effective dose of 50.3 mSv (SD = 24.0) and the mean CTDI{sub vol} was 232 mGy (SD = 149) resulting in a mean skin dose of 233.2 mGy (SD = 117.4). The difference in patient radiation exposure between the two renal ablation techniques was statistically significant (p < 0.001).ConclusionBoth cryoablation and RFA imparted an average skin dose that was well below the 2 Gy deterministic threshold for appreciable sequela. Renal tumor cryoablation resulted in a mean skin and effective radiation dose more than twice that for RFA. The radiation exposure for both renal tumor ablation techniques was at the high end of the medical imaging radiation dose spectrum.

  11. Pulmonary Thermal Ablation: Comparison of Radiofrequency and Microwave Devices by Using Gross Pathologic and CT Findings in a Swine Model

    Science.gov (United States)

    Brace, Christopher L.; Hinshaw, J. Louis; Laeseke, Paul F.; Sampson, Lisa A.; Lee, Fred T.

    2009-01-01

    Purpose: To compare the performance of equivalently sized radiofrequency and microwave ablation applicators in a normal porcine lung model. Materials and Methods: All experiments were approved by an institutional animal care and use committee. A total of 18 ablations were performed in vivo in normal porcine lungs. By using computed tomographic (CT) fluoroscopic guidance, a 17-gauge cooled triaxial microwave antenna (n = 9) and a 17-gauge cooled radiofrequency (RF) electrode (n = 9) were placed percutaneously. Ablations were performed for 10 minutes by using either 125 W of microwave power or 200 W of RF power delivered with an impedance-based pulsing algorithm. CT images were acquired every minute during ablation to monitor growth. Animals were sacrificed after the procedure. Ablation zones were then excised and sectioned transverse to the applicator in 5-mm increments. Minimum and maximum diameter, cross-sectional area, length, and circularity were measured from gross specimens and CT images. Comparisons of each measurement were performed by using a mixed-effects model; P ablation and mean cross-sectional area (8.25 cm2 ± 0.92 vs 5.45 cm2 ± 1.14, P ablation, compared with RF ablation. With microwave ablation, the zones of ablation were also significantly more circular in cross section (mean circularity, 0.90 ± 0.06 vs 0.82 ± 0.09; P ablation but stabilized without intervention. Conclusion: Microwave ablation with a 17-gauge high-power triaxial antenna creates larger and more circular zones of ablation than does a similarly sized RF applicator in a preclinical animal model. Microwave ablation may be a more effective treatment of lung tumors. © RSNA, 2009 PMID:19336667

  12. Characterization of the Morphology of RDX Particles Formed by Laser Ablation

    Science.gov (United States)

    2012-02-01

    laser-ablated particle sizes. ...................4 Figure 3. SEM images of laser-ablated M43 propellant grain at (a) 150× magnification and (b) 500...Experimental Method 2.1 Materials The energetic materials studied included an M43 propellant grain that consists of ~76% RDX, 12% cellulose acetate...butyrate (CAB), 8% plasticizer, and 4% nitrocellulose (NC) (26). Class-1 ( m) and class-5 (ឝ m) military-grade and research-grade (i.e

  13. Co:MgF2 laser ablation of tissue: effect of wavelength on ablation threshold and thermal damage.

    Science.gov (United States)

    Schomacker, K T; Domankevitz, Y; Flotte, T J; Deutsch, T F

    1991-01-01

    The wavelength dependence of the ablation threshold of a variety of tissues has been studied by using a tunable pulsed Co:MgF2 laser to determine how closely it tracks the optical absorption length of water. The Co:MgF2 laser was tuned between 1.81 and 2.14 microns, a wavelength region in which the absorption length varies by a decade. For soft tissues the ablation threshold tracks the optical absorption length; for bone there is little wavelength dependence, consistent with the low water content of bone. Thermal damage vs. wavelength was also studied for cornea and bone. Thermal damage to cornea has a weak wavelength dependence, while that to bone shows little wavelength dependence. Framing-camera pictures of the ablation of both cornea and liver show explosive removal of material, but differ as to the nature of the explosion.

  14. THE THERMAL AND ABLATIVE DEGRADATION OF SOME EPOXY RESINS CURED WITH METHYL BICYCLO(2.2.1)HEPTENE-2,3-DICARBOXYLIC ANHYDRIDE (NMA).

    Science.gov (United States)

    ABLATION), (* EPOXY RESINS , (*PYROLYSIS, EPOXY RESINS ), CYCLOALKENES, ANHYDRIDES, CATALYSTS, ADDITIVES, CROSSLINKING(CHEMISTRY), REACTION KINETICS, DEGRADATION, AGING(MATERIALS), INFRARED SPECTRA, CHROMATOGRAPHIC ANALYSIS.

  15. Image and pathological changes after microwave ablation of breast cancer: A pilot study

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Wenbin [Department of Breast Surgery, The First Affiliated Hospital, Nanjing Medical University, 300 Guangzhou Road, Nanjing 210029 (China); Jiang, Yanni [Department of Radiology, The First Affiliated Hospital, Nanjing Medical University, 300 Guangzhou Road, Nanjing 210029 (China); Chen, Lin; Ling, Lijun; Liang, Mengdi; Pan, Hong [Department of Breast Surgery, The First Affiliated Hospital, Nanjing Medical University, 300 Guangzhou Road, Nanjing 210029 (China); Wang, Siqi [Department of Radiology, The First Affiliated Hospital, Nanjing Medical University, 300 Guangzhou Road, Nanjing 210029 (China); Ding, Qiang [Department of Breast Surgery, The First Affiliated Hospital, Nanjing Medical University, 300 Guangzhou Road, Nanjing 210029 (China); Liu, Xiaoan, E-mail: liuxiaoan@126.com [Department of Breast Surgery, The First Affiliated Hospital, Nanjing Medical University, 300 Guangzhou Road, Nanjing 210029 (China); Wang, Shui, E-mail: ws0801@hotmail.com [Department of Breast Surgery, The First Affiliated Hospital, Nanjing Medical University, 300 Guangzhou Road, Nanjing 210029 (China)

    2014-10-15

    Highlights: • We report successful experience of MWA in breast cancer under local anesthesia. • We report MR imaging evaluation of microwave ablation zone in breast cancer. • Pathological changes after microwave ablation in breast cancer was reported. • 2 min MWA caused an ablation zone with three diameters > 2 cm in breast cancer. - Abstract: Purpose: To prospectively assess MR imaging evaluation of the ablation zone and pathological changes after microwave ablation (MWA) in breast cancer. Materials and methods: Twelve enrolled patients, diagnosed with non-operable locally advanced breast cancer (LABC), were treated by MWA and then neoadjuvant chemotherapy, followed by surgery. MR imaging was applied to evaluate the effect of MWA. Hematoxylin-eosin (HE) staining and transmission electron microscopy (TEM) were applied to analyze the ablated area. Results: All MWA procedures were performed successfully under local anesthesia. For a mean duration of 2.15 min, the mean largest, middle and smallest diameters in the ablated zone 24-h post-ablation in MR imaging were 2.98 cm ± 0.53, 2.51 cm ± 0.41 and 2.23 cm ± 0.41, respectively. The general shape of the ablation zone was close to a sphere. The ablated area became gradually smaller in MR imaging. No adverse effects related to MWA were noted in all 12 patients during and after MWA. HE staining could confirm the effect about 3 months after MWA, which was confirmed by TEM. Conclusions: 2 min MWA can cause an ablation zone with three diameters larger than 2 cm in breast cancer, which may be suitable for the local treatment of breast cancer up to 2 cm in largest diameter. However, the long-term effect of MWA in the treatment of small breast cancer should be determined in the future.

  16. Ablation and radar-wave transmission performances of the nitride ceramic matrix composites

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The 2.5 dimensional silica fiber reinforced nitride matrix composites (2.5D SiO2f/Si3N4-BN) were prepared through the preceramic polymer impregnation pyrolysis (PIP) method. The ablation and radar-wave transparent performances of the composite at high temperature were evaluated under arc jet. The composition and ablation surface microstructures were studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that the 2.5D SiO2f/Si3N4-BN composites have a linear ablation rate of 0.33 mm/s and high radar-wave transparent ratio of 98.6%. The fused layer and the matrix are protected by each other, and no fused layer accumulates on the ablation surface. The nitride composite is a high-temperature ablation resistivity and microwave transparent material.

  17. Ablation and radar-wave transmission performances of the nitride ceramic matrix composites

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The 2.5 dimensional silica fiber reinforced nitride matrix composites (2.5D SiO2f/Si3N4-BN) were prepared through the preceramic polymer impregnation pyro- lysis (PIP) method. The ablation and radar-wave transparent performances of the composite at high temperature were evaluated under arc jet. The composition and ablation surface microstructures were studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that the 2.5D SiO2f/Si3N4-BN composites have a linear ablation rate of 0.33 mm/s and high radar-wave trans- parent ratio of 98.6%. The fused layer and the matrix are protected by each other, and no fused layer accumulates on the ablation surface. The nitride composite is a high-temperature ablation resistivity and microwave transparent material.

  18. Laser ablation studies of nanocomposites

    Directory of Open Access Journals (Sweden)

    Oleg V. Mkrtychev

    2015-03-01

    Full Text Available The first experimental measurements of the threshold energy density values for the laser ablation of glass nanocomposites with nanodimensional coatings have been carried out under the action of the YAG–Nd laser power pulse radiation. The coatings in question were of different compositions and had been created by the sol–gel technology. The procedure for determining the laser ablation threshold energy density values was worked out on the base of the breakdown probability level of 0.5. The statistical processing of the measurement data over all the samples allowed obtaining the dependence of the ablation destruction threshold energy parameters on the coating physical and chemical properties such as the sample transmission in the visible region of the spectrum, coating thickness, the chemical composition of the film-forming solution, and on the pulse duration of laser radiation.

  19. Microwave ablation of hepatocellular carcinoma

    Institute of Scientific and Technical Information of China (English)

    2015-01-01

    Although surgical resection is still the optimal treatmentoption for early-stage hepatocellular carcinoma(HCC) in patients with well compensated cirrhosis,thermal ablation techniques provide a valid nonsurgicaltreatment alternative, thanks to their minimalinvasiveness, excellent tolerability and safety profile,proven efficacy in local disease control, virtuallyunlimited repeatability and cost-effectiveness. Differentenergy sources are currently employed in clinics asphysical agents for percutaneous or intra-surgicalthermal ablation of HCC nodules. Among them, radiofrequency(RF) currents are the most used, whilemicrowave ablations (MWA) are becoming increasinglypopular. Starting from the 90s', RF ablation (RFA) rapidlybecame the standard of care in ablation, especially inthe treatment of small HCC nodules; however, RFAexhibits substantial performance limitations in thetreatment of large lesions and/or tumors located nearmajor heat sinks. MWA, first introduced in the FarEastern clinical practice in the 80s', showing promisingresults but also severe limitations in the controllabilityof the emitted field and in the high amount of poweremployed for the ablation of large tumors, resultingin a poor coagulative performance and a relativelyhigh complication rate, nowadays shows better resultsboth in terms of treatment controllability and of overallcoagulative performance, thanks to the improvementof technology. In this review we provide an extensiveand detailed overview of the key physical and technicalaspects of MWA and of the currently available systems,and we want to discuss the most relevant published dataon MWA treatments of HCC nodules in regard to clinicalresults and to the type and rate of complications, both inabsolute terms and in comparison with RFA.

  20. Percutaneous radiofrequency ablation for lung tumors beneath the rib under CT fluoroscopic guidance with gantry tilt

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Takanobu; Yamagami, Takuji; Tanaka, Osamu; Yoshimatsu, Rika; Miura, Hiroshi; Nishimura, Tsunehiko (Dept. of Radiology, Graduate School of Medical Science, Kyoto Prefectural Univ. of Medicine, Kamigyo, Kyoto (Japan)), e-mail: yamagami@koto.kpu-m.ac.jp

    2010-05-15

    Background: Radiofrequency (RF) ablation of lung tumors has become a treatment of choice, especially for unresectable cases. However, RF ablation of small lung lesions located just beneath the rib is difficult. Purpose: To evaluate the efficacy and safety of gantry tilting for the performance of RF ablation of peripheral lesions located beneath the rib. Material and Methods: Our study was based on 18 of 293 lesions in the lung for which RF ablation was performed under CT scan fluoroscopic guidance at our institution between October 2004 and March 2009. For these 18 lesions, RF ablation was performed with gantry tilting because a rib blocked visualization of the RF ablation route even after other attempts had been made to change the relationship between the target and the rib. Results: All RF needles, with only one exception, were successfully advanced to hit the tumor. The commonest complication was a pneumothorax, which occurred in seven procedures. No serious complications occurred. The progression-free rates were 82.4% at 6 months, 62.5% at 12 months, and 30% at 24 months. Mean local progression-free duration was 17.6+-11.6 months (range 4-36 months). Conclusion: RF ablation under CT scan fluoroscopic guidance with gantry tilt is a useful and safe technique for RF ablation of lung nodules located beneath the rib

  1. Radiofrequency ablation of hepatic metastasis: Results of treatment in forty patients

    Directory of Open Access Journals (Sweden)

    Rath G

    2008-01-01

    Full Text Available Aim: To evaluate the local control of hepatic metastasis with radiofrequency ablation treatment. Materials and Methods: We did a retrospective analysis in 40 patients treated with radiofrequency ablation for hepatic metastasis. The tumors ablated included up to two metastatic liver lesions, with primaries in breast, gastrointestinal tract, cervix, etc. Radiofrequency ablation was performed under general anesthesia in all cases, using ultrasound guidance. Radionics Cool-Tip RF System was used to deliver the treatment. Results: The median age of patients treated was 49 years. There were 13 female and 27 male patients. The median tumor size ablated was 1.5 cm (0.75-4.0 cm. A total of 52 radiofrequency ablation cycles were delivered. Successful ablation was achieved in all patients with hepatic metastasis less than 3 cm in size. Pain was the most common complication seen (75%. One patients developed skin burns. At 2-year follow-up 7.5% of patients had locally recurrent disease. Conclusions: Radiofrequency ablation is a minimally invasive treatment modality. It can be useful in a select group of patients with solitary liver metastasis of less than 3 cm size.

  2. Laser ablation at the hydrodynamic regime

    Directory of Open Access Journals (Sweden)

    Gojani Ardian B.

    2013-04-01

    Full Text Available Laser ablation of several metals and PVC polymer by high energy nanosecond laser pulses is investigated experimentaly. Visualization by shadowgraphy revealed the dynamics of the discontinuities in ambient air and ablation plume above the target surface, while surface profiling allowed for determination of the ablated mass.

  3. Laser ablation at the hydrodynamic regime

    OpenAIRE

    Gojani Ardian B.

    2013-01-01

    Laser ablation of several metals and PVC polymer by high energy nanosecond laser pulses is investigated experimentaly. Visualization by shadowgraphy revealed the dynamics of the discontinuities in ambient air and ablation plume above the target surface, while surface profiling allowed for determination of the ablated mass.

  4. Laser ablation and optical surface damage

    Science.gov (United States)

    Chase, L. L.; Hamza, A. V.; Lee, H. W. H.

    Laser ablation usually accompanies optical surface damage to bare surfaces and coatings. Investigations of optical damage mechanisms by observation of ablation processes at laser fluences very close to the optical damage threshold are described. Several promising surface characterization methods for investigating damage mechanisms are also described. The possible role of laser ablation in initiating or promoting optical surface damage is discussed.

  5. Laser ablation mechanisms and optical surface damage

    Science.gov (United States)

    Chase, L. L.; Hamza, A. V.; Lee, H. W. H.

    1991-05-01

    Laser ablation usually accompanies optical surface damage to bare surfaces and coatings. Investigations of optical damage mechanisms by observation of ablation processes at laser fluences very close to the optical damage threshold are described. Several promising surface characterization methods for investigating damage mechanisms are also described. The possible role of laser ablation in initiating or promoting optical surface damage is discussed.

  6. Soft thrombus formation in radiofrequency catheter ablation

    NARCIS (Netherlands)

    Demolin, JM; Eick, OJ; Munch, K; Koullick, E; Nakagawa, H; Wittkampf, FHM

    2002-01-01

    During RF catheter ablation, local temperature elevation can result in coagulum formation on the ablation electrode, resulting in impedance rise. A recent study has also demonstrated the formation of a so-called soft thrombus during experimental ablations. This deposit poorly adhered to the catheter

  7. Catheter ablation of parahisian premature ventricular complex.

    Science.gov (United States)

    Kim, Jun; Kim, Jeong Su; Park, Yong Hyun; Kim, June Hong; Chun, Kook Jin

    2011-12-01

    Catheter ablation is performed in selected patients with a symptomatic premature ventricular complex (PVC) or PVC-induced cardiomyopathy. Ablation of PVC from the His region has a high risk of inducing a complete atrioventricular block. Here we report successful catheter ablation of a parahisian PVC in a 63-year-old man.

  8. Ablation of Solid Hydrogen in a Plasma

    DEFF Research Database (Denmark)

    Jørgensen, L. W.; Sillesen, Alfred Hegaard

    1979-01-01

    Several hydrogen pellet ablation models based on the formation of a shielding neutral cloud have been reported by different authors. The predicted ablation rates are shown to follow almost the same scaling law and this is used to explain the authors' ablation experiment....

  9. Deflection of uncooperative targets using laser ablation

    Science.gov (United States)

    Thiry, Nicolas; Vasile, Massimiliano

    2015-09-01

    Owing to their ability to move a target in space without requiring propellant, laser-based deflection methods have gained attention among the research community in the recent years. With laser ablation, the vaporized material is used to push the target itself allowing for a significant reduction in the mass requirement for a space mission. Specifically, this paper addresses two important issues which are thought to limit seriously the potential efficiency of a laser-deflection method: the impact of the tumbling motion of the target as well as the impact of the finite thickness of the material ablated in the case of a space debris. In this paper, we developed a steady-state analytical model based on energetic considerations in order to predict the efficiency range theoretically allowed by a laser deflection system in absence of the two aforementioned issues. A numerical model was then implemented to solve the transient heat equation in presence of vaporization and melting and account for the tumbling rate of the target. This model was also translated to the case where the target is a space debris by considering material properties of an aluminium 6061-T6 alloy and adapting at every time-step the size of the computational domain along with the recession speed of the interface in order to account for the finite thickness of the debris component. The comparison between the numerical results and the analytical predictions allow us to draw interesting conclusions regarding the momentum coupling achievable by a given laser deflection system both for asteroids and space debris in function of the flux, the rotation rate of the target and its material properties. In the last section of this paper, we show how a reasonably small spacecraft could deflect a 56m asteroid with a laser system requiring less than 5kW of input power.

  10. Nanosecond laser ablation of bulk Al, Bronze, and Cu: ablation rate saturation and laserinduced oxidation

    OpenAIRE

    R. Maisterrena-Epstein; S. Camacho-López; L. Escobar-Alarcón; M. A. Camacho-López

    2007-01-01

    In this work we report about the characteristics of nanosecond laser ablation, in atmospheric air, of bulk Al, Bronze, and Cu. Average per pulse laser ablation rate and its dependence on ablation depth is presented for these three metals. We will demonstrate and discuss some distinctive features of the ablation saturation effect of the above metals. We will also present results on laser-induced oxidation of the metals which results off the ablation event. We studied the laser-induced oxidatio...

  11. Image-guided radiofrequency ablation of hepatocellular carcinoma (HCC): Is MR guidance more effective than CT guidance?

    Energy Technology Data Exchange (ETDEWEB)

    Clasen, Stephan, E-mail: stephan.clasen@med.uni-tuebingen.de [University Hospital, Department of Diagnostic and Interventional Radiology, Hoppe-Seyler Str. 3, 72076 Tübingen (Germany); Rempp, Hansjörg, E-mail: hansjoerg.rempp@med.uni-tuebingen.de [University Hospital, Department of Diagnostic and Interventional Radiology, Hoppe-Seyler Str. 3, 72076 Tübingen (Germany); Hoffmann, Rüdiger, E-mail: ruediger.hoffmann@med.uni-tuebingen.de [University Hospital, Department of Diagnostic and Interventional Radiology, Hoppe-Seyler Str. 3, 72076 Tübingen (Germany); Graf, Hansjörg, E-mail: hansjoerg.graf@med.uni-tuebingen.de [University Hospital, Department of Diagnostic and Interventional Radiology, Section of Experimental Radiology, Hoppe-Seyler Str. 3, 72076 Tübingen (Germany); Pereira, Philippe L., E-mail: Philippe.Pereira@slk-kliniken.de [SLK Clinic Heilbronn, Clinic for Radiology, Minimal-invasive Therapies, and Nuclear Medicine, Am Gesundbrunnen 20-26, 74078 Heilbronn (Germany); Claussen, Claus D., E-mail: claus.claussen@med.uni-tuebingen.de [University Hospital, Department of Diagnostic and Interventional Radiology, Hoppe-Seyler Str. 3, 72076 Tübingen (Germany)

    2014-01-15

    Objectives: The purpose of the study was to retrospectively compare technique effectiveness of computed tomography (CT)-guided versus magnetic resonance (MR)-guided radiofrequency (RF) ablation of hepatocellular carcinoma (HCC). Materials and methods: In 35 consecutive patients 53 CT-guided (n = 29) or MR-guided (n = 24) ablation procedures were performed in the treatment of 56 (CT: 29; MR: 27) HCC. The entire ablation procedure was performed at a multislice CT-scanner or an interventional 0.2-Tesla MR-scanner. Assessment of treatment response was based on dynamic MR imaging at 1.5 Tesla. The mean follow-up was 22.9 months. Primary technique effectiveness was assessed 4 months after ablation therapy. Secondary technique effectiveness was assessed 4 months after a facultative second ablation procedure. Primary and secondary technique effectiveness of CT-guided and MR-guided RF ablation was compared by using Chi-Square (likelihood ratio) test. Results: Primary technique effectiveness after a single session was achieved in 26/27 (96.3%) HCC after MR-guided RF ablation and 23/29 (79.3%) HCC after CT-guided RF ablation (Chi-Square: p = 0.04). Secondary technique effectiveness was achieved in 26/27 (96.3%) HCC after MR-guided RF ablation and in 26/29 (89.7%) HCC after CT-guided RF ablation (Chi-Square: p = 0.32). A local tumor progression was detected in 8/52 (15.4%) tumors after initial technique effectiveness. Major complications were detected after 3/53 (5.7%) ablation procedures. Conclusions: CT-guided and MR-guided RF ablations are locally effective therapies in the treatment of HCC. Due to a higher rate of primary technique effectiveness MR-guided RF ablation may reduce the number of required sessions for complete tumor treatment.

  12. Hydrodynamic instabilities in an ablation front

    Energy Technology Data Exchange (ETDEWEB)

    Piriz, A R; Portugues, R F [E.T.S.I. Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real (Spain)

    2004-06-01

    The hydrodynamic stability of an ablation front is studied for situations in which the wavelength of the perturbations is larger than the distance to the critical surface where the driving radiation is absorbed. An analytical model is presented, and it shows that under conditions in which the thermal flux is limited within the supercritical region of the ablative corona, the front may behave like a flame or like an ablation front, depending on the perturbation wavelength. For relatively long wavelengths the critical and ablation surfaces practically lump together into a unique surface and the front behaves like a flame, whereas for the shortest wavelengths the ablation front substructure is resolved.

  13. Ablation characteristics of special concrete due to an impinging zirconium-dioxide melt jet

    Energy Technology Data Exchange (ETDEWEB)

    An, S.M., E-mail: sangmoan@kaeri.re.kr; Ha, K.S.; Min, B.T.; Kim, H.Y.; Song, J.H.

    2015-04-01

    Highlights: • The jet impingement tests were performed for a special concrete of core-catcher. • The ablation rate and depth were measured 1.59 mm/s and 4.33 mm, respectively. • The experimental results were estimated well between the model prediction bounds. • The material ablation was described reasonably by a convective heat transfer model. - Abstract: Jet impingement experiments were performed to investigate the ablation characteristics of special concrete, which has been developed as one of the candidate protecting materials for the EU-APR1400 ex-vessel core catcher. In order to simulate the jet impingement phenomenon owing to the reactor vessel failure during a severe core meltdown accident, the experimental facility was established and the experimental conditions were determined based on parametric studies. The special concrete specimen was manufactured in accordance with the standard procedures, and its microstructures and physicochemical properties were analyzed to verify the requirements for the qualification. An induction melting technique in a cold crucible was employed to generate the zirconium-dioxide melt as a simulant of the corium melt. The special concrete was ablated uniformly over the impact area by jet impingement, and the average ablation depth was measured to be 4.33 mm. The average ablation rate in depth was evaluated as 1.59 mm/s using the temperature measurements of the specimen. As compared with the predictions by the models based on the convective and radiative heat transfer analysis, both the measured ablation rate and depth were estimated appropriately within the bounds of their limits. However, the convective heat transfer model turned out to predict the ablation characteristics of the special concrete more reasonably during the jet impingement even though some water content within the special concrete could lead to a sudden generation of the steam layer through which the material ablation is attenuated substantially by the

  14. No-Touch Radiofrequency Ablation: A Comparison of Switching Bipolar and Switching Monopolar Ablation in Ex Vivo Bovine Liver

    Science.gov (United States)

    Chang, Won; Lee, Sang Min; Han, Joon Koo

    2017-01-01

    Objective To evaluate the feasibility, efficiency, and safety of no-touch switching bipolar (SB) and switching monopolar (SM) radiofrequency ablation (RFA) using ex vivo bovine livers. Materials and Methods A pork loin cube was inserted as a tumor mimicker in the bovine liver block; RFA was performed using the no-touch technique in the SM (group A1; 10 minutes, n = 10, group A2; 15 minutes, n = 10) and SB (group B; 10 minutes, n = 10) modes. The groups were compared based on the creation of confluent necrosis with sufficient safety margins, the dimensions, and distance between the electrode and ablation zone margin (DEM). To evaluate safety, small bowel loops were placed above the liver surface and 30 additional ablations were performed in the same groups. Results Confluent necroses with sufficient safety margins were created in all specimens. SM RFA created significantly larger volumes of ablation compared to SB RFA (all p < 0.001). The DEM of group B was significantly lower than those of groups A1 and A2 (all p < 0.001). Although thermal injury to the small bowel was noted in 90%, 100%, and 30% of the cases in groups A1, A2, and B, respectively, full depth injury was noted only in 60% of group A2 cases. Conclusion The no-touch RFA technique is feasible in both the SB and SM modes; however, SB RFA appears to be more advantageous compared to SM RFA in the creation of an ablation zone while avoiding the unnecessary creation of an adjacent parenchymal ablation zone or adjacent small bowel injuries.

  15. Ablation study of tungsten-based nuclear thermal rocket fuel

    Science.gov (United States)

    Smith, Tabitha Elizabeth Rose

    The research described in this thesis has been performed in order to support the materials research and development efforts of NASA Marshall Space Flight Center (MSFC), of Tungsten-based Nuclear Thermal Rocket (NTR) fuel. The NTR was developed to a point of flight readiness nearly six decades ago and has been undergoing gradual modification and upgrading since then. Due to the simplicity in design of the NTR, and also in the modernization of the materials fabrication processes of nuclear fuel since the 1960's, the fuel of the NTR has been upgraded continuously. Tungsten-based fuel is of great interest to the NTR community, seeking to determine its advantages over the Carbide-based fuel of the previous NTR programs. The materials development and fabrication process contains failure testing, which is currently being conducted at MSFC in the form of heating the material externally and internally to replicate operation within the nuclear reactor of the NTR, such as with hot gas and RF coils. In order to expand on these efforts, experiments and computational studies of Tungsten and a Tungsten Zirconium Oxide sample provided by NASA have been conducted for this dissertation within a plasma arc-jet, meant to induce ablation on the material. Mathematical analysis was also conducted, for purposes of verifying experiments and making predictions. The computational method utilizes Anisimov's kinetic method of plasma ablation, including a thermal conduction parameter from the Chapman Enskog expansion of the Maxwell Boltzmann equations, and has been modified to include a tangential velocity component. Experimental data matches that of the computational data, in which plasma ablation at an angle shows nearly half the ablation of plasma ablation at no angle. Fuel failure analysis of two NASA samples post-testing was conducted, and suggestions have been made for future materials fabrication processes. These studies, including the computational kinetic model at an angle and the

  16. Heat accumulation in ultra-short pulsed scanning laser ablation of metals.

    Science.gov (United States)

    Bauer, Franziska; Michalowski, Andreas; Kiedrowski, Thomas; Nolte, Stefan

    2015-01-26

    High average laser powers can have a serious adverse impact on the ablation quality in ultra-short pulsed laser material processing of metals. With respect to the scanning speed, a sharp transition between a smooth, reflective and an uneven, dark ablated surface is observed. Investigating the influence of the sample temperature, it is experimentally shown that this effect stems from heat accumulation. In a numerical heat flow simulation, the critical scanning speed indicating the change in ablation quality is determined in good agreement with the experimental data.

  17. Ablation experiment and threshold calculation of titanium alloy irradiated by ultra-fast pulse laser

    Directory of Open Access Journals (Sweden)

    Buxiang Zheng

    2014-02-01

    Full Text Available The interaction between an ultra-fast pulse laser and a material's surface has become a research hotspot in recent years. Micromachining of titanium alloy with an ultra-fast pulse laser is a very important research direction, and it has very important theoretical significance and application value in investigating the ablation threshold of titanium alloy irradiated by ultra-fast pulse lasers. Irradiated by a picosecond pulse laser with wavelengths of 1064 nm and 532 nm, the surface morphology and feature sizes, including ablation crater width (i.e. diameter, ablation depth, ablation area, ablation volume, single pulse ablation rate, and so forth, of the titanium alloy were studied, and their ablation distributions were obtained. The experimental results show that titanium alloy irradiated by a picosecond pulse infrared laser with a 1064 nm wavelength has better ablation morphology than that of the green picosecond pulse laser with a 532 nm wavelength. The feature sizes are approximately linearly dependent on the laser pulse energy density at low energy density and the monotonic increase in laser pulse energy density. With the increase in energy density, the ablation feature sizes are increased. The rate of increase in the feature sizes slows down gradually once the energy density reaches a certain value, and gradually saturated trends occur at a relatively high energy density. Based on the linear relation between the laser pulse energy density and the crater area of the titanium alloy surface, and the Gaussian distribution of the laser intensity on the cross section, the ablation threshold of titanium alloy irradiated by an ultra-fast pulse laser was calculated to be about 0.109 J/cm2.

  18. Ablation Property of Ceramics/Carbon Fibers/Resin Novel Super-hybrid Composite

    Institute of Scientific and Technical Information of China (English)

    Jun QIU; Xiaoming CAO; Chong TIAN; Jinsong ZHANG

    2005-01-01

    A novel super-hybrid composite (NSHC) is prepared with three-dimension reticulated SiC ceramic (3DRC), high performance carbon fibers and modified phenolic resin (BPR) in this paper. Ablation performance of super-hybrid composite is studied. The results show that the NSHC has less linear ablation rate compared with pure BPR and CF/BPR composite, for example, its linear ablation rate is 50% of CF/BPR at the same fiber content. Mass ablation rate of the NSHC is slightly lower than that of pure BPR and CF/BPR composite because of their difference in the density. Scanning electron microscopic analysis indicates that 3DRC can increase anti-erosion capacity of materials because its special reticulated structure can control the deformation of materials and strengthen the stability of integral structure.

  19. UV solid state laser ablation of intraocular lenses

    Science.gov (United States)

    Apostolopoulos, A.; Lagiou, D. P.; Evangelatos, Ch.; Spyratou, E.; Bacharis, C.; Makropoulou, M.; Serafetinides, A. A.

    2013-06-01

    Commercially available intraocular lenses (IOLs) are manufactured from silicone and acrylic, both rigid (e.g. PMMA) and foldable (hydrophobic or hydrophilic acrylic biomaterials), behaving different mechanical and optical properties. Recently, the use of apodizing technology to design new diffractive-refractive multifocals improved the refractive outcome of these intraocular lenses, providing good distant and near vision. There is also a major ongoing effort to refine laser refractive surgery to correct other defects besides conventional refractive errors. Using phakic IOLs to treat high myopia potentially provides better predictability and optical quality than corneal-based refractive surgery. The aim of this work was to investigate the effect of laser ablation on IOL surface shaping, by drilling circular arrays of holes, with a homemade motorized rotation stage, and scattered holes on the polymer surface. In material science, the most popular lasers used for polymer machining are the UV lasers, and, therefore, we tried in this work the 3rd and the 5th harmonic of a Q-switched Nd:YAG laser (λ=355 nm and λ=213 nm respectively). The morphology of the ablated IOL surface was examined with a scanning electron microscope (SEM, Fei - Innova Nanoscope) at various laser parameters. Quantitative measurements 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 variations in surface height and, finally, the ablation rates were also mathematically simulated for depicting the possible laser ablation mechanism(s). The experimental results and the theoretical modelling of UV laser interaction with polymeric IOLs are discussed in relation with the physical (optical, mechanical and thermal) properties of the material, in addition to laser radiation parameters (laser energy fluence, number of pulses). The qualitative aspects of laser ablation at λ=213 nm reveal a

  20. Ablation Study of WC and PCD Composites Using 10 Picosecond and 1 Nanosecond Pulse Durations at Green and Infrared Wavelengths

    Science.gov (United States)

    Eberle, Gregory; Wegener, Konrad

    An ablation study is carried out to compare 10 picosecond and 1 nanosecond pulse durations as well as 532 nanometre and 1064 nanometre wavelengths at each corresponding pulse duration. All laser parameters are kept constant in order to understand the influence of pulse duration and wavelength independently. The materials processed according to the electronic band structure are a metal and an insulator/metal composite, i.e. tungsten carbide and polycrystalline diamond composite respectively. After laser processing said materials, the ablation rate and surface roughness are determined. Analysis into the ablation behaviour between the various laser parameters and the materials processed is given, with a particular emphasis on the graphitisation of diamond.

  1. Experience of robotic catheter ablation in humans using a novel remotely steerable catheter sheath

    Science.gov (United States)

    Wallace, Daniel T.; Goldenberg, Alex S.; Peters, Nicholas S.; Davies, D. Wyn

    2008-01-01

    Background A novel remotely controlled steerable guide catheter has been developed to enable precise manipulation and stable positioning of any eight French (Fr) or smaller electrophysiological catheter within the heart for the purposes of mapping and ablation. Objective To report our initial experience using this system for remotely performing catheter ablation in humans. Methods Consecutive patients attending for routine ablation were recruited. Various conventional diagnostic catheters were inserted through the left femoral vein in preparation for treating an accessory pathway (n = 1), atrial flutter (n = 2) and atrial fibrillation (n = 7). The steerable guide catheter was inserted into the right femoral vein through which various irrigated and non-irrigated tip ablation catheters were used. Conventional endpoints of loss of pathway conduction, bidirectional cavotricuspid isthmus block and four pulmonary vein isolation were used to determine acute procedural success. Results Ten patients underwent remote catheter ablation using conventional and/or 3D non-fluoroscopic mapping technologies. All procedural endpoints were achieved using the robotic control system without manual manipulation of the ablation catheter. There was no major complication. A radiation dosimeter positioned next to the operator 2.7 m away from the X-ray source showed negligible exposure despite a mean cumulative dose area product of 7,281.4 cGycm2 for all ten ablation procedures. Conclusions Safe and clinically effective remote navigation of ablation catheters can be achieved using a novel remotely controlled steerable guide catheter in a variety of arrhythmias. The system is compatible with current mapping and ablation technologies Remote navigation substantially reduces radiation exposure to the operator. Electronic supplementary material The online version of this article (doi:10.1007/s10840-007-9184-z) contains supplementary material, which is available to authorized users

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

    Energy Technology Data Exchange (ETDEWEB)

    Moreland, Anna J., E-mail: ajmoreland@gmail.com; Lubner, Meghan G., E-mail: mlubner@uwhealth.org; Ziemlewicz, Timothy J., E-mail: tziemlewicz@uwhealth.org; Kitchin, Douglas R., E-mail: dkitchin@uwhealth.org; Hinshaw, J. Louis, E-mail: jhinshaw@uwhealth.org; Johnson, Alexander D., E-mail: ajohnsonuwbme@gmail.com; Lee, Fred T., E-mail: flee@uwhealth.org; Brace, Christopher L., E-mail: clbrace@wisc.edu [University of Wisconsin – Madison, Department of Radiology, E3/366 Clinical Science Center (United States)

    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. Atmospheric pressure arc discharge with ablating graphite anode

    Energy Technology Data Exchange (ETDEWEB)

    Nemchinsky, V. A. [Keiser University, Fort Lauderdale Campus, FL, 33309, USA; Raitses, Y. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

    2015-05-18

    The anodic carbon arc discharge is used to produce carbon nanoparticles. Recent experiments with the carbon arc at atmospheric pressure helium demonstrated the enhanced ablation rate for narrow graphite anodes resulting in high deposition rates of carbonaceous products on the copper cathode (Fetterman et al 2008 Carbon 46 1322–6). The proposed model explains these results with interconnected steady-state models of the cathode and the anode processes. When considering cathode functioning, the model predicts circulation of the particles in the near-cathode region: evaporation of the cathode material, ionization of evaporated atoms and molecules in the near-cathode plasma, return of the resulting ions to the cathode, surface recombination of ions and electrons followed again by cathode evaporation etc. In the case of the low anode ablation rate, the ion acceleration in the cathode sheath provides the major cathode heating mechanism. In the case of an intensive anode ablation, an additional cathode heating is due to latent fusion heat of the atomic species evaporated from the anode and depositing at the cathode. Using the experimental arc voltage as the only input discharge parameter, the model allows us to calculate the anode ablation rate. A comparison of the results of calculations with the available experimental data shows reasonable agreement.

  4. Glass particles produced by laser ablation for ICP-MSmeasurements

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, J.; Liu, C.; Wen, S.; Mao, X.; Russo, R.E.

    2007-06-01

    Pulsed laser ablation (266nm) was used to generate glass particles from two sets of standard reference materials using femtosecond (150fs) and nanosecond (4ns) laser pulses with identical fluences of 50 J cm{sup -2}. Scanning electron microscopy (SEM) images of the collected particles revealed that there are more and larger agglomerations of particles produced by nanosecond laser ablation. In contrast to the earlier findings for metal alloy samples, no correlation between the concentration of major elements and the median particle size was found. When the current data on glass were compared with the metal alloy data, there were clear differences in terms of particle size, crater depth, heat affected zone, and ICP-MS response. For example, glass particles were larger than metal alloy particles, the craters in glass were less deep than craters in metal alloys, and damage to the sample was less pronounced in glass compared to metal alloys samples. The femtosecond laser generated more intense ICP-MS signals compared to nanosecond laser ablation for both types of samples, although glass sample behavior was more similar between ns and fs-laser ablation than for metals alloys.

  5. Sonography-guided percutaneous microwave ablation of intrahepatic primary cholangiocarcinoma

    Energy Technology Data Exchange (ETDEWEB)

    Yu Mingan [Department of Interventional Ultrasound, Chinese PLA General Hospital, 28 Fuxing Road, Beijing, 100853 (China); Liang Ping, E-mail: Liangping301@hotmail.com [Department of Interventional Ultrasound, Chinese PLA General Hospital, 28 Fuxing Road, Beijing, 100853 (China); Yu Xiaoling; Cheng Zhigang; Han Zhiyu; Liu Fangyi; Yu Jie [Department of Interventional Ultrasound, Chinese PLA General Hospital, 28 Fuxing Road, Beijing, 100853 (China)

    2011-11-15

    Objective: To evaluate the efficacy and safety of sonography-guided percutaneous microwave ablation of intrahepatic primary cholangiocarcinoma. Materials and methods: From May 2006 to March 2010, 15 patients (11 men, 4 women; mean age, 57.4 years) with 24 histologically proven intrahepatic primary cholangiocarcinoma lesions (mean tumor size, 3.2 {+-} 1.9 cm; range, 1.3-9.9 cm) were treated with microwave ablation. Results: Thirty-eight sessions were performed for 24 nodules in 15 patients. The follow-up period was 4-31 months (mean, 12.8 {+-} 8.0 months). The ablation success rate, the technique effectiveness rate, and the local tumor progression rate were 91.7% (22/24), 87.5% (21/24), and 25% (6/24) respectively according to the results of follow-up. The cumulative overall 6, 12, 24 month survival rates were 78.8%, 60.0%, and 60.0%, respectively. Major complication occurred including liver abscess in two patients (13.3%) and needle seeding in one patient (6.7%). Both complications were cured satisfied with antibiotic treatment combined to catheter drainage for abscess and resection for needle seeding. The minor complications and side effects were experienced by most patients which subsided with supportive treatment. Conclusion: Microwave ablation can be used as a safe and effective technique to treat intrahepatic primary cholangiocarcinoma.

  6. Femtosecond laser ablation of gold interdigitated electrodes for electronic tongues

    Science.gov (United States)

    Manzoli, Alexandra; de Almeida, Gustavo F. B.; Filho, José A.; Mattoso, Luiz H. C.; Riul, Antonio; Mendonca, Cleber R.; Correa, Daniel S.

    2015-06-01

    Electronic tongue (e-tongue) sensors based on impedance spectroscopy have emerged as a potential technology to evaluate the quality and chemical composition of food, beverages, and pharmaceuticals. E-tongues usually employ transducers based on metal interdigitated electrodes (IDEs) coated with a thin layer of an active material, which is capable of interacting chemically with several types of analytes. IDEs are usually produced by photolithographic methods, which are time-consuming and costly, therefore, new fabrication technologies are required to make it more affordable. Here, we employed femtosecond laser ablation with pulse duration of 50 fs to microfabricate gold IDEs having finger width from 2.3 μm up to 3.2 μm. The parameters used in the laser ablation technique, such as light intensity, scan speed and beam spot size have been optimized to achieve uniform IDEs, which were characterized by optical and scanning electron microscopy. The electrical properties of gold IDEs fabricated by laser ablation were evaluated by impedance spectroscopy, and compared to those produced by conventional photolithography. The results show that femtosecond laser ablation is a promising alternative to conventional photolithography for fabricating metal IDEs for e-tongue systems.

  7. Emission characteristics of laser ablation-hollow cathode glow discharge spectral source

    Directory of Open Access Journals (Sweden)

    Karatodorov Stefan

    2014-11-01

    Full Text Available The emission characteristics of a scheme combining laser ablation as sample introduction source and hollow cathode discharge as excitation source are presented. The spatial separation of the sample material introduction by laser ablation and hollow cathode excitation is achieved by optimizing the gas pressure and the sample-cathode gap length. At these conditions the discharge current is maximized to enhance the analytical lines intensity.

  8. Aerospace Laser Ignition/Ablation Variable High Precision Thruster

    Science.gov (United States)

    Campbell, Jonathan W. (Inventor); Edwards, David L. (Inventor); Campbell, Jason J. (Inventor)

    2015-01-01

    A laser ignition/ablation propulsion system that captures the advantages of both liquid and solid propulsion. A reel system is used to move a propellant tape containing a plurality of propellant material targets through an ignition chamber. When a propellant target is in the ignition chamber, a laser beam from a laser positioned above the ignition chamber strikes the propellant target, igniting the propellant material and resulting in a thrust impulse. The propellant tape is advanced, carrying another propellant target into the ignition chamber. The propellant tape and ignition chamber are designed to ensure that each ignition event is isolated from the remaining propellant targets. Thrust and specific impulse may by precisely controlled by varying the synchronized propellant tape/laser speed. The laser ignition/ablation propulsion system may be scaled for use in small and large applications.

  9. Femtosecond laser ablation of a metal, a dielectric and a semiconductor illuminated at oblique angles of incidence

    CERN Document Server

    Liu, Xiao-Long; Petrarca, Massimo; Polynkin, Pavel

    2016-01-01

    We report the measurements of fluence thresholds for single-shot femtosecond laser ablation, as functions of the angle of incidence and at different polarizations of the laser beam, for a metal, a dielectric and a semiconductor. We use the linear index of refraction, unperturbed by the ablating laser pulse, to compute the values of the laser fluence transmitted into the material, corresponding to the measured values of the ablation threshold fluence in the incident beam. Our data show that, in spite of the complex nonlinear ionization dynamics involved in the ablation process, thus computed transmitted threshold fluence is remarkably independent of the angle of incidence and polarization of the laser beam, for all three material types. We suggest that the angular dependence of ablation threshold can be utilized for profiling fluence distributions in ultra-intense femtosecond laser beams.

  10. 高能飞秒激光烧蚀金靶材的动态热导率影响研究%Effect of Electronic Thermal Conductivity on Properties of Gold Target Material of Femtosecond Laser Ablation

    Institute of Scientific and Technical Information of China (English)

    谭新玉; 魏慧丽; 毛峰; 徐辉进; 黄祥平; 易佳

    2011-01-01

    The influence of electronic thermal conductivity on properties of the femtosecond laser ablation of gold was studied. Because the electron heat capacity, electron-phonon coupling coefficient and electronic thermal conductivity and other thermal physical parameters had influence on the maximum temperature, electron-phonon coupling time and electron-phonon coupling temperature, which characterized the properties of femtosecond pulsed laser ablation. In addition, the physical parameters were expressions of electron temperature or electron temperature and lattice temperature. In order to better understand the influence of electronic thermal conductivity on properties in femtosecond laser ablation, electronic heat capacity and electron-phonon coupling coefficient were taken a reasonable constant value, respectively, while the electronic thermal conductivity was taken three constant values within reasonable limits by arithmetic law, by simulating the heat transfer evolution on target surface based on the one-dimensional two-temperature model, the influence of electron thermal conductivity on maximum electron temperature, on electron-phonon coupling time and electron-phonon coupling temperature was mainly discussed in the femtosecond laser ablation. Hie results showed that electronic thermal conductivity had different effects on electronic maximum temperature, electron-phonon coupling time and electron-phonon coupling temperature. As the electronic thermal conductivity was a reflection of the energy release rate in electronic sub-system when the surface electrons reached to the highest temperature, this led to the electronic thermal conductivity had the most significant influence on the electro-lattice coupling temperature.%讨论了高能飞秒激光烧蚀金属金靶材过程中电子热导率对激光烧蚀性质的影响.由于电子热容量,电声耦合系数及电子热导率等热物理参数对能够表征飞秒激光烧蚀性质的电子最高温度,电声耦

  11. Novel Hybrid Ablative/Ceramic Layered Composite for Earth Re-entry Thermal Protection: Microstructural and Mechanical Performance

    Science.gov (United States)

    Triantou, K.; Mergia, K.; Marinou, A.; Vekinis, G.; Barcena, J.; Florez, S.; Perez, B.; Pinaud, G.; Bouilly, J.-M.; Fischer, W. P. P.

    2015-04-01

    In view of spacecraft re-entry applications into planetary atmospheres, hybrid thermal protection systems based on layered composites of ablative materials and ceramic matrix composites are investigated. Joints of ASTERM™ lightweight ablative material with Cf/SiC (SICARBON™) were fabricated using commercial high temperature inorganic adhesives. Sound joints without defects are produced and very good bonding of the adhesive with both base materials is observed. Mechanical shear tests under ambient conditions and in liquid nitrogen show that mechanical failure always takes place inside the ablative material with no decohesion of the interface of the adhesive layer with the bonded materials. Surface treatment of the ablative surface prior to bonding enhances both the shear strength and the ultimate shear strain by up to about 60%.

  12. Doping He droplets by laser ablation with a pulsed supersonic jet source

    Energy Technology Data Exchange (ETDEWEB)

    Katzy, R.; Singer, M.; Izadnia, S.; LaForge, A. C., E-mail: aaron.laforge@physik.uni-freiburg.de; Stienkemeier, F. [Physikalisches Institut, Universität Freiburg, 79104 Freiburg (Germany)

    2016-01-15

    Laser ablation offers the possibility to study a rich number of atoms, molecules, and clusters in the gas phase. By attaching laser ablated materials to helium nanodroplets, one can gain highly resolved spectra of isolated species in a cold, weakly perturbed system. Here, we present a new setup for doping pulsed helium nanodroplet beams by means of laser ablation. In comparison to more well-established techniques using a continuous nozzle, pulsed nozzles show significant differences in the doping efficiency depending on certain experimental parameters (e.g., position of the ablation plume with respect to the droplet formation, nozzle design, and expansion conditions). In particular, we demonstrate that when the ablation region overlaps with the droplet formation region, one also creates a supersonic beam of helium atoms seeded with the sample material. The processes are characterized using a surface ionization detector. The overall doping signal is compared to that of conventional oven cell doping showing very similar dependence on helium stagnation conditions, indicating a comparable doping process. Finally, the ablated material was spectroscopically studied via laser induced fluorescence.

  13. Laser Ablation with Vacuum Capture for MALDI Mass Spectrometry of Tissue

    Science.gov (United States)

    Donnarumma, Fabrizio; Cao, Fan; Murray, Kermit K.

    2016-01-01

    We have developed a laser ablation sampling technique for matrix-assisted laser desorption ionization (MALDI) mass spectrometry and tandem mass spectrometry (MS/MS) analyses of in-situ digested tissue proteins. Infrared laser ablation was used to remove biomolecules from tissue sections for collection by vacuum capture and analysis by MALDI. Ablation and transfer of compounds from tissue removes biomolecules from the tissue and allows further analysis of the collected material to facilitate their identification. Laser ablated material was captured in a vacuum aspirated pipette-tip packed with C18 stationary phase and the captured material was dissolved, eluted, and analyzed by MALDI. Rat brain and lung tissue sections 10 μm thick were processed by in-situ trypsin digestion after lipid and salt removal. The tryptic peptides were ablated with a focused mid-infrared laser, vacuum captured, and eluted with an acetonitrile/water mixture. Eluted components were deposited on a MALDI target and mixed with matrix for mass spectrometry analysis. Initial experiments were conducted with peptide and protein standards for evaluation of transfer efficiency: a transfer efficiency of 16% was obtained using seven different standards. Laser ablation vacuum capture was applied to freshly digested tissue sections and compared with sections processed with conventional MALDI imaging. A greater signal intensity and lower background was observed in comparison with the conventional MALDI analysis. Tandem time-of-flight MALDI mass spectrometry was used for compound identification in the tissue.

  14. Nanosecond laser ablation processes in aluminum-doped zinc-oxide for photovoltaic devices

    Energy Technology Data Exchange (ETDEWEB)

    Canteli, D., E-mail: david.canteli@ciemat.es [Division de Energias Renovables, Energia Solar Fotovoltaica, CIEMAT, Avda. Complutense, 22, 28040 Madrid (Spain); Fernandez, S. [Division de Energias Renovables, Energia Solar Fotovoltaica, CIEMAT, Avda. Complutense, 22, 28040 Madrid (Spain); Molpeceres, C. [Centro Laser, Universidad Politecnica de Madrid, Ctra. de Valencia Km 7.3, 28031 Madrid (Spain); Torres, I.; Gandia, J.J. [Division de Energias Renovables, Energia Solar Fotovoltaica, CIEMAT, Avda. Complutense, 22, 28040 Madrid (Spain)

    2012-09-15

    Highlights: Black-Right-Pointing-Pointer A study of the ablation of AZO thin films deposited at different temperature conditions with nanosecond UV laser light for photovoltaic devices has been performed. Black-Right-Pointing-Pointer The ablation threshold of AZO thin films was measured and related with the absorption coefficient of the films at the laser wavelength, showing a direct correspondence. Black-Right-Pointing-Pointer A change in the material structure in the areas closest to the edges of laser grooves made in samples deposited at temperatures below 100 Degree-Sign C was observed and studied. - Abstract: Aiming to a future use in thin film solar modules, the processing of aluminum doped zinc oxide thin films with good optoelectronic properties with a nanosecond-pulsed ultraviolet laser has been studied. The ablation threshold fluence of the films has been determined and associated with the material properties. The ablation process has been optimized and grooves with good properties for photovoltaic devices have been obtained. The morphology of the ablated surfaces has been observed by confocal microscopy and its structure has been characterized by Raman spectroscopy. The influence of ablation parameters like focus distance, pulse energy and repetition frequency in the groove morphology has been studied with special attention to the thermal effects on the material structure.

  15. Surgical and Pathological Changes after Radiofrequency Ablation of Thyroid Nodules

    OpenAIRE

    Chiara Dobrinja; Stella Bernardi; Bruno Fabris; Rita Eramo; Petra Makovac; Gabriele Bazzocchi; Lanfranco Piscopello; Enrica Barro; Nicolò de Manzini; Deborah Bonazza; Maurizio Pinamonti; Fabrizio Zanconati; Fulvio Stacul

    2015-01-01

    Background. Radiofrequency ablation (RFA) has been recently advocated as an effective technique for the treatment of symptomatic benign thyroid nodules. It is not known to what extent it may affect any subsequent thyroid surgery and/or histological diagnosis. Materials and Methods. RFA was performed on 64 symptomatic Thy2 nodules (benign nodules) and 6 symptomatic Thy3 nodules (follicular lesions/follicular neoplasms). Two Thy3 nodules regrew after the procedure, and these patients accepted t...

  16. Morphology and mechanisms of picosecond ablation of metal films on fused silica substrates

    Science.gov (United States)

    Bass, Isaac L.; Negres, Raluca A.; Stanion, Ken; Guss, Gabe; Keller, Wesley J.; Matthews, Manyalibo J.; Rubenchik, Alexander M.; Yoo, Jae Hyuck; Bude, Jeffrey D.

    2016-12-01

    The ablation of magnetron sputtered metal films on fused silica substrates by a 1053 nm, picosecond class laser was studied as part of a demonstration of its use for in-situ characterization of the laser spot under conditions commonly used at the sample plane for laser machining and damage studies. Film thicknesses were 60 and 120 nm. Depth profiles and SEM images of the ablation sites revealed several striking and unexpected features distinct from those typically observed for ablation of bulk metals. Very sharp thresholds were observed for both partial and complete ablation of the films. Partial film ablation was largely independent of laser fluence with a surface smoothness comparable to that of the unablated surface. Clear evidence of material displacement was seen at the boundary for complete film ablation. These features were common to a number of different metal films including Inconel on commercial neutral density filters, stainless steel, and aluminum. We will present data showing the morphology of the ablation sites on these films as well as a model of the possible physical mechanisms producing the unique features observed.

  17. Percutaneous laser ablation of hepatocellular carcinoma in patients with liver cirrhosis awaiting liver transplantation

    Energy Technology Data Exchange (ETDEWEB)

    Pompili, Maurizio, E-mail: mpompili@rm.unicatt.i [Department of Internal Medicine, Universita Cattolica del Sacro Cuore, Largo A. Gemelli, 8, 00168 Roma (Italy); Pacella, Claudio Maurizio, E-mail: claudiomauriziopacella@gmail.co [Department of Diagnostic Imaging and Interventional Radiology, Ospedale Regina Apostolorum, Via S. Francesco D' Assisi, 50, 00041 Albano Laziale (RM) (Italy); Francica, Giampiero, E-mail: giampierofrancica@tin.i [Department of Interventional Ultrasound, Presidio Ospedaliero Camilliani, S. Maria della Pieta, Via S. Rocco, 9, 80026 Casoria (Namibia) (Italy); Angelico, Mario, E-mail: angelico@med.uniroma2.i [Hepatology Unit, Universita di Tor Vergata, Viale Oxford, 81, 00133 Rome (Italy); Tisone, Giuseppe, E-mail: tisone@med.uniroma2.i [Transplant and General Surgery Unit, Universita di Tor Vergata, Ospedale S. Eugenio, Piazzale dell' Umanesimo 10-00144 Rome (Italy); Craboledda, Paolo, E-mail: paolo.craboledda@virgilio.i [Department of Pathology, Ospedale S. Eugenio, Piazzale dell' Umanesimo, 10-00144 Rome (Italy); Nicolardi, Erica; Rapaccini, Gian Ludovico; Gasbarrini, Giovanni [Department of Internal Medicine, Universita Cattolica del Sacro Cuore, Largo A. Gemelli, 8, 00168 Roma (Italy)

    2010-06-15

    Objective: The aim of this study was to determine the effectiveness and safety of percutaneous laser ablation for the treatment of cirrhotic patients with hepatocellular carcinoma awaiting liver transplantation. Materials and methods: The data of 9 male cirrhotic patients (mean age 50 years, range 45-60 years) with 12 biopsy proven nodules of hepatocellular carcinoma (mean diameter 2.0 cm, range 1.0-3.0 cm) treated by laser ablation before liver transplantation between June 2000 and January 2006 were retrospectively reviewed. Laser ablation was carried out by inserting 300 nm optical fibers through 21-Gauge needles (from two to four) positioned under ultrasound guidance into the target lesions. A continuous wave Neodymium:Yttrium Aluminium Garnet laser was used. Transarterial chemoembolization prior to liver transplantation was performed in two incompletely ablated tumors. Results: No procedure-related major complications were recorded. During the waiting time to liver transplantation local tumor progression after ablation occurred in 3 nodules (25%). At histological examination of the explanted livers complete necrosis was found in 8 nodules (66.7%, all treated exclusively with laser ablation), partial necrosis >50% in 3 nodules (25%), and partial necrosis <50% in 1 nodule. Conclusion: In patients with cirrhotic livers awaiting liver transplantation, percutaneous laser ablation is safe and effective for the management of small hepatocellular carcinoma.

  18. Pre-Ablation Thyroglobulin Levels and Persistence / Recurrence Associated to Early Differentiated Thyroid Cancer

    Directory of Open Access Journals (Sweden)

    Arturo Mejía López

    2014-01-01

    Full Text Available Introduction: Differentiated thyroid cancer is the most frequent endocrine neoplasm in the world and its incidence is growing rapidly. The relationship between levels of pre-ablation thyroglobulin (Tg and early persistence/recurrence of differentiated thyroid cancer was studied. Materials and Methods: 91 patients with papillary thyroid cancer who underwent post-surgical ablation with radioactive iodine registered in the Fundacion Cardioinfantil between January 2006 and January 2010 were evaluated. The analysis of the results was performed using the SPSS statistical package and the research hypothesis was evaluated using nonparametric methods. Results: The disease progressed in 20 patients during the first year post-ablation, at the end of this period (p=0.000 a significant relationship between pre-ablation Tg and disease status was found. In the group of individuals by whom the disease progressed there was no significant change in Tg between the first and the second semester post-ablation (p = 0.554; there were no cases of recurrence/persistence in those with levels less than or equal to 2.7 ng/mL; 80 % of these cases involved individuals with initial levels higher than 24 ng/mL. Conclusion: In patients with papillary thyroid cáncer the serum pre-ablation Tg is related to the disease status at the end of the first year post-ablation. The persistence/recurrence is less frequent in low levels and more frequent in higher levels.

  19. Transient Ablation Regime in Circuit Breakers

    Institute of Scientific and Technical Information of China (English)

    Alexandre MARTIN; Jean-Yves TREPANIER; Marcelo REGGIO; GUO Xue-yan

    2007-01-01

    Nozzle wall ablation caused by high temperature electric arcs is studied in the context of high voltage SF6 circuit breakers.The simplified ablation model used in litterature has been updated to take into account the unsteady state of ablation.Ablation rate and velocity are now calculated by a kinetic model using two layers of transition,between the bulk plasma and the ablating wall.The first layer (Knudsen layer),right by the wall,is a kinetic layer of a few mean-free path of thickness.The second layer is collision dominated and makes the transition between the kinetic layer and the plasma bulk.With this new coupled algorithm,it is now possible to calculate the temperature distribution inside the wall,as well as more accurate ablation rates.

  20. Neocuproine Ablates Melanocytes in Adult Zebrafish

    OpenAIRE

    O'Reilly-Pol, Thomas; Johnson, Stephen L.

    2008-01-01

    The simplest regeneration experiments involve the ablation of a single cell type. While methods exist to ablate the melanocytes of the larval zebrafish,1,2 no convenient method exists to ablate melanocytes in adult zebrafish. Here, we show that the copper chelator neocuproine (NCP) causes fragmentation and disappearance of melanin in adult zebrafish melanocytes. Adult melanocytes expressing eGFP under the control of a melanocyte-specific promoter also lose eGFP fluorescence in the presence of...

  1. Computer-aided hepatic tumour ablation

    CERN Document Server

    Voirin, D; Amavizca, M; Leroy, A; Letoublon, C; Troccaz, J; Voirin, David; Payan, Yohan; Amavizca, Miriam; Leroy, Antoine; Letoublon, Christian; Troccaz, Jocelyne

    2001-01-01

    Surgical resection of hepatic tumours is not always possible. Alternative techniques consist in locally using chemical or physical agents to destroy the tumour and this may be performed percutaneously. It requires a precise localisation of the tumour placement during ablation. Computer-assisted surgery tools may be used in conjunction to these new ablation techniques to improve the therapeutic efficiency whilst benefiting from minimal invasiveness. This communication introduces the principles of a system for computer-assisted hepatic tumour ablation.

  2. Cryoballoon Catheter Ablation in Atrial Fibrillation

    Directory of Open Access Journals (Sweden)

    Cevher Ozcan

    2011-01-01

    Full Text Available Pulmonary vein isolation with catheter ablation is an effective treatment in patients with symptomatic atrial fibrillation refractory or intolerant to antiarrhythmic medications. The cryoballoon catheter was recently approved for this procedure. In this paper, the basics of cryothermal energy ablation are reviewed including its ability of creating homogenous lesion formation, minimal destruction to surrounding vasculature, preserved tissue integrity, and lower risk of thrombus formation. Also summarized here are the publications describing the clinical experience with the cryoballoon catheter ablation in both paroxysmal and persistent atrial fibrillation, its safety and efficacy, and discussions on the technical aspect of the cryoballoon ablation procedure.

  3. Aromatic Thermosetting Copolyesters for Ablative TPS Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Better performing ablative thermal protection systems than currently available are needed to satisfy requirements of the most severe crew exploration vehicles, such...

  4. Computational Analysis of Arc-Jet Wedge Tests Including Ablation and Shape Change

    Science.gov (United States)

    Goekcen, Tahir; Chen, Yih-Kanq; Skokova, Kristina A.; Milos, Frank S.

    2010-01-01

    Coupled fluid-material response analyses of arc-jet wedge ablation tests conducted in a NASA Ames arc-jet facility are considered. These tests were conducted using blunt wedge models placed in a free jet downstream of the 6-inch diameter conical nozzle in the Ames 60-MW Interaction Heating Facility. The fluid analysis includes computational Navier-Stokes simulations of the nonequilibrium flowfield in the facility nozzle and test box as well as the flowfield over the models. The material response analysis includes simulation of two-dimensional surface ablation and internal heat conduction, thermal decomposition, and pyrolysis gas flow. For ablating test articles undergoing shape change, the material response and fluid analyses are coupled in order to calculate the time dependent surface heating and pressure distributions that result from shape change. The ablating material used in these arc-jet tests was Phenolic Impregnated Carbon Ablator. Effects of the test article shape change on fluid and material response simulations are demonstrated, and computational predictions of surface recession, shape change, and in-depth temperatures are compared with the experimental measurements.

  5. Experimental and Analytical Investigation of Cemented Tungsten Carbide Ultra-Short Pulse Laser Ablation

    Science.gov (United States)

    Urbina, J. P. Calderón; Daniel, C.; Emmelmann, C.

    Ultra-short pulse laser processing of hard materials, such as cemented tungsten carbide, requires an accurate and agile experimental and analytical investigation to obtain adequate information and setting parameters to maximize ablation rate. Therefore, this study presents a systematic approach which, first, experimentally searches for the variables with the most significant influence on the objective using a design of experiments method; and second, analyzes by means of existing ablation theory the interaction of the material and laser taking into account the Beer-Lambert law and incubation effect.Therefore, this places a basis for future analytical-experimental validation of the examined material.

  6. Using FT-IR Spectroscopy to Elucidate the Structures of Ablative Polymers

    Science.gov (United States)

    Fan, Wendy

    2011-01-01

    The composition and structure of an ablative polymer has a multifaceted influence on its thermal, mechanical and ablative properties. Understanding the molecular level information is critical to the optimization of material performance because it helps to establish correlations with the macroscopic properties of the material, the so-called structure-property relationship. Moreover, accurate information of molecular structures is also essential to predict the thermal decomposition pathways as well as to identify decomposition species that are fundamentally important to modeling work. In this presentation, I will describe the use of infrared transmission spectroscopy (FT-IR) as a convenient tool to aid the discovery and development of thermal protection system materials.

  7. Analysis of internal ablation for the thermal control of aerospace vehicles

    Science.gov (United States)

    Camberos, Jose A.; Roberts, Leonard

    1989-01-01

    A new method of thermal protection for transatmospheric vehicles is introduced. The method involves the combination of radiation, ablation and transpiration cooling. By placing an ablating material behind a fixed-shape, porous outer shield, the effectiveness of transpiration cooling is made possible while retaining the simplicity of a passive mechanism. A simplified one-dimensional approach is used to derive the governing equations. Reduction of these equations to non-dimensional form yields two parameters which characterize the thermal protection effectiveness of the shield and ablator combination for a given trajectory. The non-dimensional equations are solved numerically for a sample trajectory corresponding to glide re-entry. Four typical ablators are tested and compared with results obtained by using the thermal properties of water. For the present level of analysis, the numerical computations adequately support the analytical model.

  8. Thermo-mechanical performance of an ablative/ceramic composite hybrid thermal protection structure for re-entry applications

    OpenAIRE

    Triantou, K.; Mergia, K; Florez, S.; Perez, B.; Bárcena, Jorge; Rotärmel, W.; Pinaud, G.; Fischer, W.P.P.

    2015-01-01

    Hybrid thermal protection systems for aerospace applications based on ablative material (ASTERM (TM)) and ceramic matrix composite (SICARBON (TM)) have been investigated. The ablative material and the ceramic matrix composite were joined using graphite and zirconia zirconium silicate based commercial high temperature adhesives. The thermo-mechanical performance of the structures was assessed from room temperature up to 900 degrees C. In all the joints there is a decrease of shear strength wit...

  9. Molecular dynamics simulation of heat-affected zone of copper metal ablated with femtosecond laser

    Science.gov (United States)

    Hirayama, Yoichi; Obara, Minoru

    2005-03-01

    Femtosecond laser ablation of materials with high thermal conductivity is of paramount importance, because the chemical composition and properties of the area ablated with femtosecond laser are kept unchanged. The material processing by femtosecond laser can well control the heat-affected zone, compared to nanosecond laser ablation. We report on the heat-affected zone of crystalline copper (Cu) by use of femtosecond laser experimentally and theoretically. Laser ablation of Cu is investigated theoretically by two temperature model and molecular dynamics (MD) simulation. The MD simulation takes into account of electron temperature and thermal diffusion length calculated by two temperature model. The dependence of lattice temperature on time and depth is calculated by the MD simulation and two temperature model. The heat-affected zone estimated from the temperature is mainly studied and calculated to be 3 nm at 0.02 J/cm2 which is below the threshold fluence of 0.137 J/cm2. In addition, the thickness of heat-affected zone of copper crystal ablated with femtosecond Ti:sapphire laser is experimentally studied. As a result of X-ray diffraction (XRD) of the ablated surface, the surface crystallinity is partially changed into disordered structure from crystal form. The residual energy left in the metal, which is not used for ablation, will induce liquid phase, leading to the amorphous phase of the metal during resolidification. The thickness of heat-affected zone depends on laser fluence and is experimentally measured to be less than 1 μm at higher laser fluences than the ablation threshold.

  10. Cyanate Ester and Phthalonitrile Impregnated Carbon Ablative TPS

    Science.gov (United States)

    Boghozian, Tane; Stackpoole, Margaret M.; Gasch, Matt

    2016-01-01

    Phenolic resin has extensive heritage as a TPS (Thermal Protection Systems) material, however, alternative resin systems such as Cyanate Ester and Phthalonitrile may offer improved performance compared to state-of-the-art phenolic resin. These alternative resin systems may have higher char yield, higher char strength, lower thermal conductivity and improved mechanical properties. In current work at NASA Ames alternative resin systems were uniformly infused into fibrous substrates and preliminary properties characterized. The density of the cyanate ester infused in fibrous substrate ranged from 0.25-0.3 grams per cubic centimeter compared to PICA (Phenolic resin impregnated carbon ablative) having a density of approximately 0.25 grams per cubic centimeter. The density of Phthalonitrile varies from 0.22-0.25 grams per cubic centimeter. Initial formulations of these new resin systems were recently tested at the LARC HyMETs (Hypersonic Materials Environmental Test System) facility to evaluate their performance and data such as back face temperature, char yield, and recession are compared to PICA. Cyanate Ester and Phthalonitrile impregnated carbon ablative samples showed comparable performance to phenolic resin impregnated carbon ablative samples.

  11. Fully Automated Laser Ablation Liquid Capture Sample Analysis using NanoElectrospray Ionization Mass Spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Lorenz, Matthias [ORNL; Ovchinnikova, Olga S [ORNL; Van Berkel, Gary J [ORNL

    2014-01-01

    RATIONALE: Laser ablation provides for the possibility of sampling a large variety of surfaces with high spatial resolution. This type of sampling when employed in conjunction with liquid capture followed by nanoelectrospray ionization provides the opportunity for sensitive and prolonged interrogation of samples by mass spectrometry as well as the ability to analyze surfaces not amenable to direct liquid extraction. METHODS: A fully automated, reflection geometry, laser ablation liquid capture spot sampling system was achieved by incorporating appropriate laser fiber optics and a focusing lens into a commercially available, liquid extraction surface analysis (LESA ) ready Advion TriVersa NanoMate system. RESULTS: Under optimized conditions about 10% of laser ablated material could be captured in a droplet positioned vertically over the ablation region using the NanoMate robot controlled pipette. The sampling spot size area with this laser ablation liquid capture surface analysis (LA/LCSA) mode of operation (typically about 120 m x 160 m) was approximately 50 times smaller than that achievable by direct liquid extraction using LESA (ca. 1 mm diameter liquid extraction spot). The set-up was successfully applied for the analysis of ink on glass and paper as well as the endogenous components in Alstroemeria Yellow King flower petals. In a second mode of operation with a comparable sampling spot size, termed laser ablation/LESA , the laser system was used to drill through, penetrate, or otherwise expose material beneath a solvent resistant surface. Once drilled, LESA was effective in sampling soluble material exposed at that location on the surface. CONCLUSIONS: Incorporating the capability for different laser ablation liquid capture spot sampling modes of operation into a LESA ready Advion TriVersa NanoMate enhanced the spot sampling spatial resolution of this device and broadened the surface types amenable to analysis to include absorbent and solvent resistant

  12. Pulsed laser ablation of polymers for display applications

    Science.gov (United States)

    Pedder, James E. A.; Holmes, Andrew S.; Booth, Heather J.

    2008-02-01

    Laser micromachining by ablation is a well established technique used for the production of 2.5D and 3D features in a wide variety of materials. The fabrication of stepped, multi-level, structures can be achieved using a number of binary mask projection techniques using excimer lasers. Alternatively, direct-writing of complex 2.5D features can easily be achieved with solid-state lasers. Excimer laser ablation using half-tone masks allows almost continuous surface relief and the generation of features with low surface roughness. We have developed techniques to create large arrays of repeating micro-optical structures on polymer substrates. Here, we show our recent developments in laser structuring with the combination of half-tone and binary mask techniques.

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

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Andrew Thomas [Univ. of California, Berkeley, CA (United States)

    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 (~ 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  15. Possible role for cryoballoon ablation of right atrial appendage tachycardia when conventional ablation fails.

    Science.gov (United States)

    Amasyali, Basri; Kilic, Ayhan

    2015-06-01

    Focal atrial tachycardia arising from the right atrial appendage usually responds well to radiofrequency ablation; however, successful ablation in this anatomic region can be challenging. Surgical excision of the right atrial appendage has sometimes been necessary to eliminate the tachycardia and prevent or reverse the resultant cardiomyopathy. We report the case of a 48-year-old man who had right atrial appendage tachycardia resistant to multiple attempts at ablation with use of conventional radiofrequency energy guided by means of a 3-dimensional mapping system. The condition led to cardiomyopathy in 3 months. The arrhythmia was successfully ablated with use of a 28-mm cryoballoon catheter that had originally been developed for catheter ablation of paroxysmal atrial fibrillation. To our knowledge, this is the first report of cryoballoon ablation without isolation of the right atrial appendage. It might also be an alternative to epicardial ablation or surgery when refractory atrial tachycardia originates from the right atrial appendage.

  16. Effective temperatures of polymer laser ablation

    Science.gov (United States)

    Furzikov, Nickolay P.

    1991-09-01

    Effective temperatures of laser ablation of certain polymers are extracted from experimental dependences of ablation depths on laser fluences. Dependence of these temperatures on laser pulse durations is established. Comparison with the known thermodestruction data shows that the effective temperature corresponds to transient thermodestruction proceeding by the statistically most probable way.

  17. Therapy of HCC-radiofrequency ablation.

    Science.gov (United States)

    Buscarini, L; Buscarini, E

    2001-01-01

    Radiofrequency interstitial hyperthermia has been used for percutaneous ablation of hepatocellular carcinoma, under ultrasound guidance in local anesthesia. Conventional needle electrodes require a mean number of 3 sessions to treat tumors of diameter hemotorax in one case; a fluid collection in the site of ablated tumor in one patient treated by combination of transcatheter arterial embolization and radiofrequency application.

  18. Attitudes Towards Catheter Ablation for Atrial Fibrillation

    DEFF Research Database (Denmark)

    Vadmann, Henrik; Pedersen, Susanne S; Nielsen, Jens Cosedis;

    2015-01-01

    BACKGROUND: Catheter ablation for atrial fibrillation (AF) is an important but expensive procedure that is the subject of some debate. Physicians´ attitudes towards catheter ablation may influence promotion and patient acceptance. This is the first study to examine the attitudes of Danish...

  19. High Heat Flux Block Ablator-in-Honeycomb Heat Shield Using Ablator/Aerogel-Filled Foam Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Ultramet and ARA Ablatives Laboratory previously developed and demonstrated advanced foam-reinforced carbon/phenolic ablators that offer substantially increased high...

  20. Tumor ablation with irreversible electroporation.

    Directory of Open Access Journals (Sweden)

    Bassim Al-Sakere

    Full Text Available We report the first successful use of irreversible electroporation for the minimally invasive treatment of aggressive cutaneous tumors implanted in mice. Irreversible electroporation is a newly developed non-thermal tissue ablation technique in which certain short duration electrical fields are used to permanently permeabilize the cell membrane, presumably through the formation of nanoscale defects in the cell membrane. Mathematical models of the electrical and thermal fields that develop during the application of the pulses were used to design an efficient treatment protocol with minimal heating of the tissue. Tumor regression was confirmed by histological studies which also revealed that it occurred as a direct result of irreversible cell membrane permeabilization. Parametric studies show that the successful outcome of the procedure is related to the applied electric field strength, the total pulse duration as well as the temporal mode of delivery of the pulses. Our best results were obtained using plate electrodes to deliver across the tumor 80 pulses of 100 micros at 0.3 Hz with an electrical field magnitude of 2500 V/cm. These conditions induced complete regression in 12 out of 13 treated tumors, (92%, in the absence of tissue heating. Irreversible electroporation is thus a new effective modality for non-thermal tumor ablation.

  1. Laser ablation of lysozyme with UV, visible and infrared femto- and nanosecond pulses

    DEFF Research Database (Denmark)

    Schou, Jørgen; Canulescu, Stela; Matei, Andreea

    yields ever measured. The mass loss is mainly caused by fragmentation of the lysozyme into simple gases, such as H2S, H2O and CO2 , which are rapidly pumped away in the vacuum chamber. We have investigated the mass loss by ablation of lysozyme in all regimes to see whether a similar mechanism governs......Lysozyme is an interesting molecule for laser ablation of organic materials, because the ablation has been comprehensively studied, it is a medium heavy molecule with a mass of 14305 Da, which can be detected by standard techniques, and because it is used as a bactericidal protein in the food...... industry. Lysozyme molecules do not absorb energy for wavelengths above 310 nm, but nevertheless there is a strong mass loss by ablation for laser irradiation in the visible regime. The total ablation yield of lysozyme at 355 nm and at 2 J/cm2 is about 155 µg/pulse, possibly one of the highest ablation...

  2. Effects of pretreated polysulfonamide pulp on the ablation behavior of EPDM composites

    Energy Technology Data Exchange (ETDEWEB)

    Jia Xiaolong; Li Gang; Sui Gang; Li Peng; Yu Yunhua; Liu Haiyang [Key Laboratory of Beijing City on Preparation and Processing of Novel Polymer Materials, Beijing University of Chemical Technology, Beijing 100029 (China); Yang Xiaoping [Key Laboratory of Beijing City on Preparation and Processing of Novel Polymer Materials, Beijing University of Chemical Technology, Beijing 100029 (China)], E-mail: yangxp@mail.buct.edu.cn

    2008-12-20

    Excellent ablative properties of ethylene-propylene-diene elastomer (EPDM) composites were obtained by adding pretreated polysulfonamide pulp (PSA-pulp). The effects of pulp pretreatment and pulp content on the mechanical and ablative properties of PSA-pulp/EPDM composites were studied. Experimental results showed that the tensile strength decreased slightly and the ablative properties increased by 3 folds on addition of 10 phr pretreated PSA-pulp. This significant improvement in the ablative properties was attributed to the enhanced dispersion degree and improved interfacial adhesion of pretreated PSA-pulp to EPDM matrix, which were observed from scanning electron microscopy. The ablation behavior of pretreated PSA-pulp/EPDM composites was proposed in accordance with the characterizations of thermogravimetric analysis (TGA), energy disperse X-ray spectroscopy (EDS) and pyrolysis-gas chromatograph-mass spectrometry (Py-GC-MS). The carbonized PSA-pulp acted as a skeleton in retaining the char layer and reduced the material loss during the high temperature ablation.

  3. Determination of ablation threshold for composite resins and amalgam irradiated with femtosecond laser pulses

    Science.gov (United States)

    Freitas, A. Z.; Freschi, L. R.; Samad, R. E.; Zezell, D. M.; Gouw-Soares, S. C.; Vieira, N. D., Jr.

    2010-03-01

    The use of laser for caries removal and cavity preparation is already a reality in the dental clinic. The objective of the present study was to consider the viability of ultrashort laser pulses for restorative material selective removal, by determining the ablation threshold fluence for composite resins and amalgam irradiated with femtosecond laser pulses. Lasers pulses centered at 830 nm with 50 fs of duration and 1 kHz of repetition rate, with energies in the range of 300 to 770 μJ were used to irradiate the samples. The samples were irradiated using two different geometrical methods for ablation threshold fluence determinations and the volume ablation was measured by optical coherence tomography. The shape of the ablated surfaces were analyzed by optical microscopy and scanning electron microscopy. The determined ablation threshold fluence is 0.35 J/cm2 for the composite resins Z-100 and Z-350, and 0.25 J/cm2 for the amalgam. These values are half of the value for enamel in this temporal regime. Thermal damages were not observed in the samples. Using the OCT technique (optical coherence tomography) was possible to determine the ablated volume and the total mass removed.

  4. Conformal Ablative Thermal Protection Systems (CA-TPS) for Venus and Saturn Backshells

    Science.gov (United States)

    Beck, R.; Gasch, M.; Stackpoole, M.; Wilder, M.; Boghozian, T.; Chavez-Garcia, J.; Prabhu, Dinesh; Kazemba, Cole D.; Venkatapathy, E.

    2016-01-01

    This poster provides an overview of the work performed to date on the Conformal Ablative TPS (CA-TPS) element of the TPSM project out of GCDP. Under this element, NASA is developing improved ablative TPS materials based on flexible felt for reinforcement rather than rigid reinforcements. By replacing the reinforcements with felt, the resulting materials have much higher strain-to-failure and are much lower in thermal conductivity than their rigid counterparts. These characteristics should allow for larger tile sizes, direct bonding to aeroshells and even lower weight TPS. The conformal phenolic impregnated carbon felt (C-PICA) is a candidate for backshell TPS for both Venus and Saturn entry vehicles.

  5. Ultrafast laser ablation in liquids for nanomaterials and applications.

    Science.gov (United States)

    Rao, S Venugopal; Podagatlapalli, G Krishna; Hamad, Syed

    2014-02-01

    We present an inclusive overview of the ultrafast ablation technique performed in liquids. Being a comparatively new method, we bring out the recent progress achieved, present the challenges ahead, and outline the future prospects for this technique. The review is conveniently divided into five parts: (a) a succinct preamble to the technique of ultrafast ablation in liquids (ULAL) is provided. A brief introduction to the conventional ns ablation is also presented for the sake of completeness (b) fundamental physical processes involved in this technique are elaborated (c) specific advantages of the technique compared to other physical and chemical methodologies are enumerated (d) applications of this technique in photonics; biomedical and explosives detection [using surface-enhanced Raman scattering (SERS)] is updated (e) future prospects describing the potential of this technique for creating unique nanoparticles (NPs) and nanostructures (NSs) for niche applications. We also discuss some of the recently reported significant results achieved in a variety of materials, especially metals, using this technique. Furthermore, we present some of our own experimental data obtained from ULAL of Ag, Cu, and Zn in a variety of liquids such as acetone, water, acetonitrile etc. The generated NPs (colloidal solutions) and NSs (on substrates) have been successfully utilized for nonlinear optical, SERS, and biomedical applications.

  6. Superhydrophobic/superoleophilic magnetic elastomers by laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Milionis, Athanasios, E-mail: am2vy@virginia.edu [Smart Materials-Nanophysics, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova (Italy); Fragouli, Despina; Brandi, Fernando; Liakos, Ioannis; Barroso, Suset [Smart Materials-Nanophysics, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova (Italy); Ruffilli, Roberta [Nanochemistry, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova (Italy); Athanassiou, Athanassia, E-mail: athanassia.athanassiou@iit.it [Smart Materials-Nanophysics, Istituto Italiano di Tecnologia (IIT), Via Morego 30, 16163 Genova (Italy)

    2015-10-01

    Highlights: • We report the development of magnetic nanocomposite sheets. • Laser irradiation of the nanocomposites induces chemical and structural changes to the surface. • The laser-patterned surfaces exhibit superhydrophobicity and superoleophilicity. • The particle contribution in altering the surface and bulk properties of the material is studied. - Abstract: We report the development of magnetic nanocomposite sheets with superhydrophobic and supeoleophilic surfaces generated by laser ablation. Polydimethylsiloxane elastomer free-standing films, loaded homogeneously with 2% wt. carbon coated iron nanoparticles, were ablated by UV (248 nm), nanosecond laser pulses. The laser irradiation induces chemical and structural changes (both in micro- and nano-scale) to the surfaces of the nanocomposites rendering them superhydrophobic. The use of nanoparticles increases the UV light absorption efficiency of the nanocomposite samples, and thus facilitates the ablation process, since the number of pulses and the laser fluence required are greatly reduced compared to the bare polymer. Additionally the magnetic nanoparticles enhance significantly the superhydrophobic and oleophilic properties of the PDMS sheets, and provide to PDMS magnetic properties making possible its actuation by a weak external magnetic field. These nanocomposite elastomers can be considered for applications requiring magnetic MEMS for the controlled separation of liquids.

  7. Micropatterned polysaccharide surfaces via laser ablation for cell guidance

    Energy Technology Data Exchange (ETDEWEB)

    Barbucci, Rolando; Lamponi, Stefania; Pasqui, Daniela; Rossi, Antonella; Weber, Elisabetta

    2003-03-03

    Micropatterned materials were obtained by a controlled laser ablation of a photoimmobilised homogeneous layer of hyaluronic acid (Hyal) and its sulphated derivative (HyalS). The photoimmobilisation was performed by coating the polysaccharide, adequately functionalised with a photoreactive group, on aminosilanised glass substrate and immobilising it on the surface under UV light. Hyal or HyalS photoimmobilised samples were then subjected to laser ablation with wavelengths in the UV regions in order to drill the pattern. Four different patterns with stripes of 100, 50, 25 and 10 {mu}m were generated. A chemical characterisation by attenuated total reflection/Fourier transform infrared (ATR/FT-IR) and time of flight-secondary ions mass spectrometry (TOF-SIMS) confirmed the success of the laser ablation procedure and the presence of alternating stripes of polysaccharide and native glass. The exact dimensions of the stripes were determined by atomic force microscopy. The analysis of cell behaviour in terms of adhesion, proliferation and movement using mouse fibroblasts (3T3 line) and bovine aortic endothelial cells (BAEC) was also performed.

  8. Numerical simulations on artificial reduction of snow and ice ablation

    Science.gov (United States)

    Olefs, M.; Obleitner, F.

    2007-06-01

    This snow modeling study investigates two methods to artificially reduce ablation in Alpine glacier ski resorts. Using the snow cover model SNTHERM, a first set of sensitivity studies focuses on the potential effects of artificial compaction of snow during winter. In comparison to a reference run representing the natural conditions, a stepwise increase of the model's new snow density toward 500 kg m-3 yields no more than 218 kg m-2 water equivalent being saved at the end of the ablation period. Further studies consider effects of covering the snow surface with different materials in spring. The physical properties and the energetic processes at the model's surface node are parameterized accordingly. The results show that 2489 kg m-2 water equivalent are saved compared to the reference run. Thus 15% of the winter snow cover as well as the whole amount of the underlying glacier ice are preserved. This indicates that surface covering reduces snow and ice ablation more effectively than snow compaction, which is confirmed by field measurements.

  9. Analysis of infrared laser tissue ablation

    Science.gov (United States)

    McKenzie, Gordon P.; Timmerman, Brenda H.; Bryanston-Cross, Peter J.

    2005-04-01

    The mechanisms involved in infrared laser tissue ablation are studied using a free electron laser (FELIX) in order to clarify whether the increased ablation efficiency reported in literature for certain infrared wavelengths is due to a wavelength effect or to the specific pulse structure of the lasers that are generally used in these studies. Investigations are presented of ablation of vitreous from pigs" eyes using several techniques including protein gel electrophoresis and ablation plume visualization. The ablation effects of three different infrared wavelengths are compared: 3 mm, which is currently in clinical surgical use, and the wavelengths associated with the amide I and amide II bands, i.e. 6.2 mm and 6.45mm, respectively. The results suggest a different ablation mechanism to be in operation for each studied wavelength, thus indicating that the generally reported increased ablation efficiency in the 6-6.5 micron range is due to the wavelength rather than the typical free electron laser pulse structure.

  10. The Effects of the Factors Related to the Patient and the Disease on the Performance of Ablation Therapy in Patients with Differentiated Thyroid Cancer who have Received I-131 Ablation Therapy

    Directory of Open Access Journals (Sweden)

    Tarık Şengöz

    2012-12-01

    Full Text Available Objective: To investigate whether the factors related to the patient and the disease have any effect on the success of ablation therapy in patients with differentiated thyroid cancer who have received I-131 ablation therapy. Material and Methods: All the patients with differentiated thyroid cancer were referred for I-131 ablation therapy after thyroidectomy between July 2007 and September 2009. The patients had at least six months of follow-up. Age, gender, type of tumor, presence of capsule invasion, size of tumor, number of the tumors, localization of the tumor, invasion of thyroid capsule, lymph/vessel invasion, presence of metastatic lymph nodes, type of surgery, preablation values of thyroglobulin (Tg, AntiTg, TSH, surveys for the evaluation of metastatic disease, (thyroid and bone scintigraphy, neck and abdominal ultrasonography, chest and brain computerized tomography, administered dose, postablation I-131 whole body scan (WBS and diagnostic I-131 WBS, neck USG, values of Tg and AntiTg at the 6th month were recorded. The presence of residual thyroid activity on the 6th month diagnostic I-131 WBS image was accepted as the criterion for ablation success. Results: 191 patients with differentiated thyroid cancer were assessed in this study. The overall success rate of the first ablation therapy was 74.3%. The success rate of the ablation therapy was 66% and 75% in metastatic group and non-metastatic group, respectively. Except the significant correlation between the number of pathologic lymph nodes and the success of ablation (p=0.025, there was no other significant correlation between the patient/disease related factors and the success of ablation therapy. Conclusion: Significant correlation between the number of the pathologic lymph nodes and the ablation therapy performance can also be due to statistical error because of the limited sample size. There was no significant correlation between other patient/disease related prognostic factors

  11. Experimental and modelling investigations into the laser ablation with picosecond pulses at second harmonics

    Science.gov (United States)

    Boerner, Paul; Zandonadi, Germana; Eberle, Gregory; Wegener, Konrad

    2015-03-01

    Ablation threshold experiments on various materials are carried out using a picosecond laser generating second harmonic radiation in air at atmospheric pressure. Various materials are investigated which vary according to their different electronic band gap structure and include: silicon, fine grain polycrystalline diamond, copper, steel and tungsten carbide. Through the use of scanning electron microscopy and 3D confocal microscopy, the crater depth and diameter are determined and a correlation is found. The ablation thresholds are given for the aforementioned materials and compared with recent literature results. Picosecond laser-material interactions are modelled using the two-temperature model, simulated and compared with experimental results for metallic materials. An extension of the two-temperature model to semiconducting and insulating materials is discussed. This alternative model uses multiple rate equations to describe the transient free electron density. Additionally, a set of coupled ordinary differential equations describes the processes of multiphoton excitation, inverse bremsstrahlung, and collisional excitation. The resulting electron density distribution can be used as an input for an electron density dependent twotemperature model. This multiple rate equation model is a generic and fast model, which provides important information like ablation threshold, ablation depth and optical properties.

  12. Real time ablation rate measurement during high aspect-ratio hole drilling with a 120-ps fiber laser.

    Science.gov (United States)

    Mezzapesa, Francesco P; Sibillano, Teresa; Di Niso, Francesca; Ancona, Antonio; Lugarà, Pietro M; Dabbicco, Maurizio; Scamarcio, Gaetano

    2012-01-02

    We report on the instantaneous detection of the ablation rate as a function of depth during ultrafast microdrilling of metal targets. The displacement of the ablation front has been measured with a sub-wavelength resolution using an all-optical sensor based on the laser diode self-mixing interferometry. The time dependence of the laser ablation process within the depth of aluminum and stainless steel targets has been investigated to study the evolution of the material removal rate in high aspect-ratio micromachined holes.

  13. Ablation response testing of aerospace power supplies

    Science.gov (United States)

    Lutz, S. A.; Chan, C. C.

    1993-01-01

    An experimental program was performed to assess the aerothermal ablation response of aerospace power supplies. Full-scale General Purpose Heat Source (GPHS) test articles, Graphite Impact Shell (GIS) test articles, and Lightweight Radioisotope Heater Unit (LWRHU) test articles were all tested without nuclear fuel in simulated reentry environments at the NASA Ames Research Center. Stagnation heating, stagnation pressure, stagnation surface temperature, stagnation surface recession profile, and weight loss measurements were obtained for diffusion-limited and sublimation ablation conditions. The recession profile and weight loss measurements showed an effect of surface features on the stagnation face. The surface features altered the local heating which in turn affected the local ablation.

  14. UV Laser Ablation of Electronically Conductive Polymers

    Science.gov (United States)

    1992-06-16

    deionized water. The polymerization solution for polyaniline was prepared by mixing equal volumes of a solution that was 0.25 M in ammonium persulfate with a...rum2,0 vvcsL) TbeUV.layer ablation of thin polypyrrole and polyaniline films coated on an insulating substrate is described. UV laser ablation is used to...11liiii929. 6 1 2:- A ABSTRACT The UV laser ablation of thin polypyrrole and polyaniline films coated on an insulating substrate is described. UV laser

  15. Diamond Ablators for Inertial Confinement Fusion

    Energy Technology Data Exchange (ETDEWEB)

    Biener, J; Mirkarimi, P B; Tringe, J W; Baker, S L; Wang, Y M; Kucheyev, S O; Teslich, N E; Wu, K J; Hamza, A V; Wild, C; Woerner, E; Koidl, P; Bruehne, K; Fecht, H

    2005-06-21

    Diamond has a unique combination of physical properties for the inertial confinement fusion ablator application, such as appropriate optical properties, high atomic density, high yield strength, and high thermal conductivity. Here, we present a feasible concept to fabricate diamond ablator shells. The fabrication of diamond capsules is a multi-step process, which involves diamond chemical vapor deposition on silicon mandrels followed by polishing, microfabrication of holes, and removing of the silicon mandrel by an etch process. We also discuss the pros and cons of coarse-grained optical quality and nanocrystalline chemical vapor deposition diamond films for the ablator application.

  16. Percutaneous treatment of hepatocellular carcinoma in patients with cirrhosis: A comparison of the safety of cryoablation and radiofrequency ablation

    Energy Technology Data Exchange (ETDEWEB)

    Dunne, Ruth M., E-mail: rmdunne@partners.org [Division of Abdominal Imaging and Intervention, Department of Radiology, Brigham and Women' s Hospital, 75 Francis Street, Boston, MA 02115 (United States); Shyn, Paul B., E-mail: pshyn@partners.org [Division of Abdominal Imaging and Intervention, Department of Radiology, Brigham and Women' s Hospital, 75 Francis Street, Boston, MA 02115 (United States); Sung, Jeffrey C., E-mail: jcsung@gmail.com [Division of Abdominal Imaging and Intervention, Department of Radiology, Brigham and Women' s Hospital, 75 Francis Street, Boston, MA 02115 (United States); Tatli, Servet, E-mail: statli@partners.org [Division of Abdominal Imaging and Intervention, Department of Radiology, Brigham and Women' s Hospital, 75 Francis Street, Boston, MA 02115 (United States); Morrison, Paul R. [Division of Abdominal Imaging and Intervention, Department of Radiology, Brigham and Women' s Hospital, 75 Francis Street, Boston, MA 02115 (United States); Catalano, Paul J., E-mail: pcata@jimmy.harvard.edu [Department of Biostatistics and Computational Biology, Dana Farber Cancer Institute, 450 Brookline Avenue, CLSB 11007, Boston, MA 02215 (United States); Department of Biostatistics, Harvard School of Public Health, Boston, MA 02215 (United States); Silverman, Stuart G., E-mail: sgsilverman@partners.org [Division of Abdominal Imaging and Intervention, Department of Radiology, Brigham and Women' s Hospital, 75 Francis Street, Boston, MA 02115 (United States)

    2014-04-15

    Purpose: To compare the safety of image-guided percutaneous cryoablation and radiofrequency ablation in the treatment of hepatocellular carcinoma in patients with cirrhosis. Materials and methods: This retrospective HIPAA-compliant study received institutional review board approval. Forty-two adult patients with cirrhosis underwent image-guided percutaneous ablation of hepatocellular carcinoma from 2003 to 2011. Twenty-five patients underwent 33 cryoablation procedures to treat 39 tumors, and 22 underwent 30 radiofrequency ablation procedures to treat 39 tumors. Five patients underwent both cryoablation and radiofrequency ablation procedures. Complication rates and severity per procedure were compared between the ablation groups. Potential confounding patient, procedure, and tumor-related variables were also compared. Statistical analyses included Kruskal–Wallis, Wilcoxon rank sum, and Fisher's exact tests. Two-sided P-values <0.05 were considered significant. Results: The overall complication rates, 13 (39.4%) of 33 cryoablation procedures versus eight (26.7%) of 30 radiofrequency ablation procedures and severe/fatal complication rates, two (6.1%) of 33 cryoablation procedures versus one (3.3%) of 30 radiofrequency ablation procedures, were not significantly different between the ablation groups (both P = 0.26). Severe complications included pneumothoraces requiring chest tube insertion during two cryoablation procedures. One death occurred within 90 days of a radiofrequency ablation procedure; all other complications were managed successfully. Conclusion: No significant difference was seen in the overall safety of image-guided percutaneous cryoablation and radiofrequency ablation in the treatment of hepatocellular carcinoma in patients with cirrhosis.

  17. Treatment of osteoid osteoma using CT-guided radiofrequency ablation versus MR-guided laser ablation: A cost comparison

    Energy Technology Data Exchange (ETDEWEB)

    Maurer, M.H., E-mail: martin.maurer@charite.de [Charite - Universitaetsmedizin Berlin, Department of Radiology, Augustenburger Platz 1, 13353 Berlin (Germany); Gebauer, B., E-mail: bernhard.gebauer@charite.de [Charite - Universitaetsmedizin Berlin, Department of Radiology, Augustenburger Platz 1, 13353 Berlin (Germany); Wieners, G., E-mail: gero.wieners@charite.de [Charite - Universitaetsmedizin Berlin, Department of Radiology, Augustenburger Platz 1, 13353 Berlin (Germany); De Bucourt, M., E-mail: maximilian.de-bucourt@charite.de [Charite - Universitaetsmedizin Berlin, Department of Radiology, Augustenburger Platz 1, 13353 Berlin (Germany); Renz, D.M., E-mail: diane.renz@charite.de [Charite - Universitaetsmedizin Berlin, Department of Radiology, Augustenburger Platz 1, 13353 Berlin (Germany); Hamm, B., E-mail: bernd.hamm@charite.de [Charite - Universitaetsmedizin Berlin, Department of Radiology, Augustenburger Platz 1, 13353 Berlin (Germany); Streitparth, F., E-mail: florian.streitparth@charite.de [Charite - Universitaetsmedizin Berlin, Department of Radiology, Augustenburger Platz 1, 13353 Berlin (Germany)

    2012-11-15

    Objective: To compare the costs of CT-guided radiofrequency ablation (RFA) and MR-guided laser ablation (LA) for minimally invasive percutaneous treatment of osteoid osteoma. Materials and methods: Between November 2005 and October 2011, 20 patients (14 males, 6 females, mean age 20.3 {+-} 9.1 years) underwent CT-guided RFA and 24 patients (18 males, 6 females; mean age, 23.8 {+-} 13.8 years) MR-guided LA (open 1.0 Tesla, Panorama HFO, Philips, Best, Netherlands) for osteoid osteoma diagnosed on the basis of clinical presentation and imaging findings. Prorated costs of equipment use (purchase, depreciation, and maintenance), staff costs, and expenditure for disposables were identified for CT-guided RFA and MR-guided LA procedures. Results: The average total costs per patient were EUR 1762 for CT-guided RFA and EUR 1417 for MR-guided LA. These were (RFA/LA) EUR 92/260 for equipment use, EUR 149/208 for staff, and EUR 870/300 for disposables. Conclusion: MR-guided LA is less expensive than CT-guided RFA for minimally invasive percutaneous ablation of osteoid osteoma. The higher costs of RFA are primarily due to the higher price of the disposable RFA probes.

  18. Contribution of material’s surface layer on charge state distribution in laser ablation plasma

    Energy Technology Data Exchange (ETDEWEB)

    Kumaki, Masafumi, E-mail: rogus@asagi.waseda.jp [Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555 (Japan); Nishina Center for Accelerator-Based Science, RIKEN, Saitama 351-0198 (Japan); Steski, Dannie; Kanesue, Takeshi [Collider-Accelerator Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); Ikeda, Shunsuke [Nishina Center for Accelerator-Based Science, RIKEN, Saitama 351-0198 (Japan); Interdisciplinary Graduate School of Science and Engineering, Tokyo Institute of Technology, Kanagawa 226-8503 (Japan); Okamura, Masahiro [Nishina Center for Accelerator-Based Science, RIKEN, Saitama 351-0198 (Japan); Collider-Accelerator Department, Brookhaven National Laboratory, Upton, New York 11973 (United States); Washio, Masakazu [Research Institute for Science and Engineering, Waseda University, Tokyo 169-8555 (Japan)

    2016-02-15

    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{sup 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.

  19. Ablation Modeling of Ares-I Upper State Thermal Protection System Using Thermal Desktop

    Science.gov (United States)

    Sharp, John R.; Page, Arthur T.

    2007-01-01

    The thermal protection system (TPS) for the Ares-I Upper Stage will be based on Space Transportation System External Tank (ET) and Solid Rocket Booster (SRB) heritage materials. These TPS materials were qualified via hot gas testing that simulated ascent and re-entry aerothermodynamic convective heating environments. From this data, the recession rates due to ablation were characterized and used in thermal modeling for sizing the thickness required to maintain structural substrate temperatures. At Marshall Space Flight Center (MSFC), the in-house code ABL is currently used to predict TPS ablation and substrate temperatures as a FORTRAN application integrated within SINDA/G. This paper describes a comparison of the new ablation utility in Thermal Desktop and SINDA/FLUINT with the heritage ABL code and empirical test data which serves as the validation of the Thermal Desktop software for use on the design of the Ares-I Upper Stage project.

  20. Typical flutter ablation as an adjunct to catheter ablation of atrial fibrillation

    Directory of Open Access Journals (Sweden)

    Dipen Shah

    2008-12-01

    Full Text Available Typical atrial flutter and atrial fibrillation are frequently observed to coexist(1 .  In the current context of interventional electrophysiology, curative or at least definitive ablation is available for both arrhythmias. Despite their coexistence, it is not clear whether typical flutter ablation is necessary in all patients undergoing catheter ablation of atrial fibrillation. The following review explores the pathophysiology of both arrhythmias, their interrelationships and the available data pertaining to this theme.

  1. Use of a circular mapping and ablation catheter for ablation of atypical right ventricular outflow tract arrhythmia.

    Science.gov (United States)

    Katritsis, Demosthenes G; Giazitzoglou, Eleftherios; Paxinos, George

    2010-02-01

    A new technique for ablation of persistent ectopic activity with atypical electrocardiographic characteristics at the vicinity of the right ventricular outflow tract is described. A new circular mapping and ablation catheter initially designed for pulmonary vein ablation was used. Abolition of ectopic activity was achieved with minimal fluoroscopy and ablation times.

  2. Cryoballoon or Radiofrequency Ablation for Paroxysmal Atrial Fibrillation.

    OpenAIRE

    Chun, KR; Bestehorn, K; Pocock, SJ; FIRE AND ICE Investigators; , COLLABORATORS; Kuck, KH; Metzner, A; Ouyang, F; Chun, J; Fürnkranz, A; Elvan, A.; Arentz, T.; Kühne, M.; Sticherling, C; Gellér, L

    2016-01-01

    BACKGROUND: Current guidelines recommend pulmonary-vein isolation by means of catheter ablation as treatment for drug-refractory paroxysmal atrial fibrillation. Radiofrequency ablation is the most common method, and cryoballoon ablation is the second most frequently used technology. METHODS: We conducted a multicenter, randomized trial to determine whether cryoballoon ablation was noninferior to radiofrequency ablation in symptomatic patients with drug-refractory paroxysmal atrial fibrillatio...

  3. Femtosecond Laser Interaction with Energetic Materials

    Energy Technology Data Exchange (ETDEWEB)

    Roos, E; Benterou, J; Lee, R; Roeske, F; Stuart, B

    2002-03-25

    Femtosecond laser ablation shows promise in machining energetic materials into desired shapes with minimal thermal and mechanical effects to the remaining material. We will discuss the physical effects associated with machining energetic materials and assemblies containing energetic materials, based on experimental results. Interaction of ultra-short laser pulses with matter will produce high temperature plasma at high-pressure which results in the ablation of material. In the case of energetic material, which includes high explosives, propellants and pyrotechnics, this ablation process must be accomplished without coupling energy into the energetic material. Experiments were conducted in order to characterize and better understand the phenomena of femtosecond laser pulse ablation on a variety of explosives and propellants. Experimental data will be presented for laser fluence thresholds, machining rates, cutting depths and surface quality of the cuts.

  4. Areal density evolution of isolated surface perturbations at the onset of x-ray ablation Richtmyer-Meshkov growth

    Science.gov (United States)

    Loomis, E. N.; Braun, D.; Batha, S. H.; Sorce, C.; Landen, O. L.

    2011-09-01

    Isolated defects on inertial confinement fusion ignition capsules are a concern as defects taller than a few hundred nanometers are calculated to form jets of high-Z material, which enter the main fuel. If this mixing of high-Z material is not controlled, a serious degradation in thermonuclear burn can occur. A path towards controlling the growth of defects on the outer surface of plastic capsules is currently under development, but requires accurate predictions of defect evolution driven by the early time ablative Richtmyer-Meshkov (RM) effect. The chief uncertainty is the Equation of State (EOS) for polystyrene and its effect on ablative RM. We report on measurements of the growth of isolated defects made at the onset of ablative RM oscillations driven by x-ray ablation to differentiate between EOS models used in design calculations. Experiments at the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] used on-axis area backlighting radiography and x-ray framing cameras to determine bump areal densities at discrete times. Bumps 12 and 14 μm tall and 33 μm FWHM were found to grow to 2 × their initial areal density by 3 ns after the start of the drive laser pulse. Shock speed measurements established target conditions resulting from the ablation process. The tabular LEOS 5310 [D. Young and E. Corey, J. Appl. Phys. 78, 3748 (1995)] model shows good agreement with measured shock speeds and bump growth whereas the QEOS model [R. More et al., Phys. Fluids 31, 3059 (1988)] over predicts shock speed and under predicts bump growth by 6×. Differences in ablative RM behavior were also found for x-ray ablation compared to laser ablation, which result in an overestimation (or non-existence) of oscillation frequency for x-ray ablation as predicted by theory.

  5. Thermal ablation of liver metastases. Current status and perspectives; Thermische Ablation von Lebermetastasen. Aktueller Stand und Perspektiven

    Energy Technology Data Exchange (ETDEWEB)

    Vogl, T.; Mack, M.; Straub, R.; Zangos, S.; Woitaschek, D.; Eichler, K.; Engelmann, K. [Inst. fuer Diagnostische und Interventionelle Radiologie, Univ. Frankfurt (Germany)

    2001-01-01

    Purpose. To present thermal ablation of liver metastases via laser induced thermotherapy. Material and methods. Different technical procedures of thermal ablation and online monitoring are used, as there are the MR-guided laser induced thermotherapy (LITT) and the radiofrequency ablation thermotherapy (RF). Results. In a prospective non randomized study 606 patients with liver metastases were treated via MR-guided laserinduced thermotherapy. Inclusion criteria were the exclusion of extrahepatic tumor spread and a number of metastases lower than 5 and a size lower than 50 mm in diameter. The local tumor control rate in the 3 month and 6 month control study was 98,3%, the complication rate 3,5% (clinically relevant: 1,2%). The mean survival rate was 40,9 months for all patients with liver metastases without statistically relevant differences for various primaries, like colorectal carcinoma, breast cancer and various other tumors. Results for radiofrequency are so far limited with incidence of a higher local tumor recurrence rate versus LITT. Conclusion. MR-guided LITT results in a high local tumor control rate with improved survival. (orig.) [German] Zielsetzung. Vorstellung der thermischen Ablation von Lebermetastasen mittels laserinduzierter Thermotherapie (LITT). Material und Methodik. Verschiedene technische Verfahren der Ablation sowie 'Online-monitoring-Verfahren' werden vorgestellt. Derzeit gaengige Verfahren der Thermoablation stellen die MR-gesteuerte laserinduzierte Thermotherapie (LITT) sowie die Radiofrequenzablation (RF) dar. Ergebnisse. Im Rahmen einer prospektiven, nichtrandomisierten Studie wurden bislang 606 Patienten mit Lebermetastasen unterschiedlicher Primaertumoren mittels LITT perkutan therapiert. Die erzielte lokale Tumorkontrolle in der 3- bzw. 6-Monatskontrolle betrug dabei 98,3%, die Rate klinisch nicht relevanter Komplikationen 3,5%, die Rate klinisch relevanter Komplikationen 1,2%. Die mittlere Ueberlebensrate fuer das

  6. Physical processes of laser tissue ablation

    Science.gov (United States)

    Furzikov, Nickolay P.

    1991-05-01

    The revised ablation model applicable to homogeneous tissues is presented. It is based on the thermal mechanism and involves the instability of the laserinduced evaporation (thermodestruction) front the growth of the surface ripple structure the interference of the laser wave and of the surface wave arising by diffraction on the ripples Beer''s law violation the pulsed thermodestruction of the organic structural component the tissue water boiling and gas dynamic expansion of the resulting products into the surrounding medium which is followed by the shock wave formation. The UV and IR ablation schemes were implemented and compared to the corneal ablation experiments. The initial ablation pressure and temperature are given restored from the timeofflight measurements of the supersonic expansion of the product. 1.

  7. Nanosecond laser ablation of silver nanoparticle film

    Science.gov (United States)

    Chung, Jaewon; Han, Sewoon; Lee, Daeho; Ahn, Sanghoon; Grigoropoulos, Costas P.; Moon, Jooho; Ko, Seung H.

    2013-02-01

    Nanosecond laser ablation of polyvinylpyrrolidone (PVP) protected silver nanoparticle (20 nm diameter) film is studied using a frequency doubled Nd:YAG nanosecond laser (532 nm wavelength, 6 ns full width half maximum pulse width). In the sintered silver nanoparticle film, absorbed light energy conducts well through the sintered porous structure, resulting in ablation craters of a porous dome shape or crown shape depending on the irradiation fluence due to the sudden vaporization of the PVP. In the unsintered silver nanoparticle film, the ablation crater with a clean edge profile is formed and many coalesced nanoparticles of 50 to 100 nm in size are observed inside the ablation crater. These results and an order of magnitude analysis indicate that the absorbed thermal energy is confined within the nanoparticles, causing melting of nanoparticles and their coalescence to larger agglomerates, which are removed following melting and subsequent partial vaporization.

  8. Nanoscale ablation through optically trapped microspheres

    Science.gov (United States)

    Fardel, Romain; McLeod, Euan; Tsai, Yu-Cheng; Arnold, Craig B.

    2010-10-01

    The ability to directly create patterns with size scales below 100 nm is important for many applications where the production or repair of high resolution and density features is needed. Laser-based direct-write methods have the benefit of being able to quickly and easily modify and create structures on existing devices, but ablation can negatively impact the overall technique. In this paper we show that self-positioning of near-field objectives through the optical trap assisted nanopatterning (OTAN) method allows for ablation without harming the objective elements. Small microbeads are positioned in close proximity to a substrate where ablation is initiated. Upon ablation, these beads are temporarily displaced from the trap but rapidly return to the initial position. We analyze the range of fluence values for which this process occurs and find that there exists a critical threshold beyond which the beads are permanently ejected.

  9. Combined use of radioiodine therapy and radiofrequency ablation in treating postsurgical thyroid remnant of differentiated thyroid carcinoma

    OpenAIRE

    Bin Long; Linfa Li; Lifang Yao; Shoucong Chen; Heqing Yi; Xuemei Ye; Dong Xu; Peng Wu

    2015-01-01

    Purpose: To determine whether postoperative radioiodine (RAI) combined with radiofrequency ablation (RFA) is an effective, safe, and feasible method for elimination of excessive postsurgical thyroid remnant for differentiated thyroid carcinoma (DTC). Materials and Methods: We took a prospective study and treated 12 DTC patients (4 males, 8 females, age 20–78 years) who underwent thyroidectomy for RFA followed by 131 I ablation. The pretreatment requires iodine-free diet and thyroid hormone...

  10. Support for High Power Laser Ablation 2010

    Science.gov (United States)

    2010-04-16

    Femtosecond Pulsed laser Ablation and Deposition Marta Castillejo Instituto de Quimica Fisica Rocasolano, CSIC, Serrano 119, 28006 Madrid, Spain Tel:+34...system to transition the laser cavity’s low pressure to the ambient pressure outside the device. Diffusers use a series of shocks in a duct to...especially the incident laser fluence and ambient pressure. New results highlight the influence of the ambient pressure on ablation physics from the

  11. ROLE OF RADIOFREQUENCY ABLATION IN ADENOMA SEBACEUM

    Directory of Open Access Journals (Sweden)

    Ch. Madh

    2016-03-01

    Full Text Available Adenoma sebaceum, pathognomonic of tuberous sclerosis, are tiny angiofibromas which commonly occur over central part of face. Recurrence after treatment is common and hence a need for inexpensive, safe and efficient treatment is required. Radiofrequency ablation is a safe and an economical procedure and has been known to cause less scarring with good aesthetic results compared to other ablative methods such as electrocautery.

  12. Principles of the radiative ablation modeling

    Science.gov (United States)

    Saillard, Yves; Arnault, Philippe; Silvert, Virginie

    2010-12-01

    Indirectly driven inertial confinement fusion (ICF) rests on the setting up of a radiation temperature within a laser cavity and on the optimization of the capsule implosion ablated by this radiation. In both circumstances, the ablation of an optically thick medium is at work. The nonlinear radiation conduction equations that describe this phenomenon admit different kinds of solutions called generically Marshak waves. In this paper, a completely analytic model is proposed to describe the ablation in the subsonic regime relevant to ICF experiments. This model approximates the flow by a deflagrationlike structure where Hugoniot relations are used in the stationary part from the ablation front up to the isothermal sonic Chapman-Jouguet point and where the unstationary expansion from the sonic point up to the external boundary is assumed quasi-isothermal. It uses power law matter properties. It can also accommodate arbitrary boundary conditions provided the ablation wave stays very subsonic and the surface temperature does not vary too quickly. These requirements are often met in realistic situations. Interestingly, the ablated mass rate, the ablation pressure, and the absorbed radiative energy depend on the time history of the surface temperature, not only on the instantaneous temperature values. The results compare very well with self-similar solutions and with numerical simulations obtained by hydrodynamic code. This analytic model gives insight into the physical processes involved in the ablation and is helpful for optimization and sensitivity studies in many situations of interest: radiation temperature within a laser cavity, acceleration of finite size medium, and ICF capsule implosion, for instance.

  13. Materials

    Science.gov (United States)

    Glaessgen, Edward H.; Schoeppner, Gregory A.

    2006-01-01

    NASA Langley Research Center has successfully developed an electron beam freeform fabrication (EBF3) process, a rapid metal deposition process that works efficiently with a variety of weldable alloys. The EBF3 process can be used to build a complex, unitized part in a layer-additive fashion, although the more immediate payoff is for use as a manufacturing process for adding details to components fabricated from simplified castings and forgings or plate products. The EBF3 process produces structural metallic parts with strengths comparable to that of wrought product forms and has been demonstrated on aluminum, titanium, and nickel-based alloys to date. The EBF3 process introduces metal wire feedstock into a molten pool that is created and sustained using a focused electron beam in a vacuum environment. Operation in a vacuum ensures a clean process environment and eliminates the need for a consumable shield gas. Advanced metal manufacturing methods such as EBF3 are being explored for fabrication and repair of aerospace structures, offering potential for improvements in cost, weight, and performance to enhance mission success for aircraft, launch vehicles, and spacecraft. Near-term applications of the EBF3 process are most likely to be implemented for cost reduction and lead time reduction through addition of details onto simplified preforms (casting or forging). This is particularly attractive for components with protruding details that would require a significantly large volume of material to be machined away from an oversized forging, offering significant reductions to the buy-to-fly ratio. Future far-term applications promise improved structural efficiency through reduced weight and improved performance by exploiting the layer-additive nature of the EBF3 process to fabricate tailored unitized structures with functionally graded microstructures and compositions.

  14. Pyrolysis of phenolic impregnated carbon ablator (PICA).

    Science.gov (United States)

    Bessire, Brody K; Lahankar, Sridhar A; Minton, Timothy K

    2015-01-28

    Molar yields of the pyrolysis products of thermal protection systems (TPSs) are needed in order to improve high fidelity material response models. The volatile chemical species evolved during the pyrolysis of a TPS composite, phenolic impregnated carbon ablator (PICA), have been probed in situ by mass spectrometry in the temperature range 100 to 935 °C. The relative molar yields of the desorbing species as a function of temperature were derived by fitting the mass spectra, and the observed trends are interpreted in light of the results of earlier mechanistic studies on the pyrolysis of phenolic resins. The temperature-dependent product evolution was consistent with earlier descriptions of three stages of pyrolysis, with each stage corresponding to a temperature range. The two main products observed were H2O and CO, with their maximum yields occurring at ∼350 °C and ∼450 °C, respectively. Other significant products were CH4, CO2, and phenol and its methylated derivatives; these products tended to desorb concurrently with H2O and CO, over the range from about 200 to 600 °C. H2 is presumed to be the main product, especially at the highest pyrolysis temperatures used, but the relative molar yield of H2 was not quantified. The observation of a much higher yield of CO than CH4 suggests the presence of significant hydroxyl group substitution on phenol prior to the synthesis of the phenolic resin used in PICA. The detection of CH4 in combination with the methylated derivatives of phenol suggests that the phenol also has some degree of methyl substitution. The methodology developed is suitable for real-time measurements of PICA pyrolysis and should lend itself well to the validation of nonequilibrium models whose aim is to simulate the response of TPS materials during atmospheric entry of spacecraft.

  15. Numerical Simulation and Analysis on 3D Temperature Field of the Metal Ablated with Femtosecond Pulse Laser

    Energy Technology Data Exchange (ETDEWEB)

    Yang Li; Yang Wei [Science College, Civil Aviation University of China, Tianjin 300300 (China); Wang Chingyue, E-mail: y_lyang@yahoo.com.cn [Key Laboratory of Opto-electronic Information Science and Technology, Ministry of Education, Tianjin University, Tianjin 300072 (China)

    2011-02-01

    To describe femtosecond laser ablation on the metal, numerical simulation on the basis of the double-temperature equation for three-dimension temperature field of the copper ablated with femtosecond pulse laser was performed by finite-difference method. Based on imbalance of the electronic and lattice's temperatures, the calefactive process of the electron and the lattice was obtained, respectively. The dependence of the electron-lattice coupling time on irradiated laser fluence was studied. The ablation depth and the ablation radius of the copper for single pulse fluence were calculated. The dependence of the start ablation (phase explosion arises) time of the copper on irradiated laser fluence was studied. The results indicate that the material jet due to phase explosion is earlier and the duration of ablation is longer with the increase of the laser fluence. When the laser fluence is higher than 1.5 J/cm{sup 2} the ablation start time is about 2-3 ps.

  16. PREFACE AND CONFERENCE INFORMATION: Eighth International Conference on Laser Ablation

    Science.gov (United States)

    Hess, Wayne P.; Herman, Peter R.; Bäuerle, Dieter; Koinuma, Hideomi

    2007-04-01

    Laser ablation encompasses a wide range of delicate to extreme light interactions with matter that present considerably challenging problems for scientists to study and understand. At the same time, laser ablation also represents a basic process of significant commercial importance in laser material processing—defining a multi-billion dollar industry today. These topics were widely addressed at the 8th International Conference on Laser Ablation (COLA), held in Banff, Canada on 11-16 September 2005. The meeting took place amongst the majestic and natural beauty of the Canadian Rocky Mountains at The Banff Centre, where delegates enjoyed many inspiring presentations and discussions in a unique campus learning environment. The conference brought together world leading scientists, students and industry representatives to examine the basic science of laser ablation and improve our understanding of the many physical, chemical and/or biological processes driven by the laser. The multi-disciplinary research presented at the meeting underlies some of our most important trends at the forefront of science and technology today that are represented in the papers collected in this volume. Here you will find new processes that are producing novel types of nanostructures and nano-materials with unusual and promising properties. Laser processes are described for delicately manipulating living cells or modifying their internal structure with unprecedented degrees of control and precision. Learn about short-pulse lasers that are driving extreme physical processes on record-fast time scales and opening new directions from material processing applications. The conference papers further highlight forefront application areas in pulsed laser deposition, nanoscience, analytical methods, materials, and microprocessing applications. Laser ablation continues to grow and evolve, touching forefront areas in science and driving new technological trends in laser processing applications. Please

  17. Pulsed erbium laser ablation of hard dental tissue: the effects of atomized water spray versus water surface film

    Science.gov (United States)

    Freiberg, Robert J.; Cozean, Colette D.

    2002-06-01

    It has been established that the ability of erbium lasers to ablate hard dental tissue is due primarily to the laser- initiated subsurface expansion of the interstitial water trapped within the enamel and that by maintaining a thin film of water on the surface of the tooth, the efficiency of the laser ablation is enhanced. It has recently been suggested that a more aggressive ablative mechanism, designated as a hydrokinetic effect, occurs when atomized water droplets, introduced between the erbium laser and the surface of the tooth, are accelerated in the laser's field and impact the tooth's surface. It is the objective of this study to determine if the proposed hydrokinetic effect exists and to establish its contribution to the dental hard tissue ablation process. Two commercially available dental laser systems were employed in the hard tissue ablation studies. One system employed a water irrigation system in which the water was applied directly to the tooth, forming a thin film of water on the tooth's surface. The other system employed pressurized air and water to create an atomized mist of water droplets between the laser hand piece and the tooth. The ablative properties of the two lasers were studied upon hard inorganic materials, which were void of any water content, as well as dental enamel, which contained interstitial water within its crystalline structure. In each case the erbium laser beam was moved across the surface of the target material at a constant velocity. When exposing material void of any water content, no ablation of the surfaces was observed with either laser system. In contrast, when the irrigated dental enamel was exposed to the laser radiation, a linear groove was formed in the enamel surface. The volume of ablated dental tissue associated with each irrigation method was measured and plotted as a function of the energy within the laser pulse. Both dental laser systems exhibited similar enamel ablation rates and comparable ablated surface

  18. Evaluation of Finite-Rate GasSurface Interaction Models for a Carbon Based Ablator

    Science.gov (United States)

    Chen, Yih-Kanq; Goekcen, Tahir

    2015-01-01

    Two sets of finite-rate gas-surface interaction model between air and the carbon surface are studied. The first set is an engineering model with one-way chemical reactions, and the second set is a more detailed model with two-way chemical reactions. These two proposed models intend to cover the carbon surface ablation conditions including the low temperature rate-controlled oxidation, the mid-temperature diffusion-controlled oxidation, and the high temperature sublimation. The prediction of carbon surface recession is achieved by coupling a material thermal response code and a Navier-Stokes flow code. The material thermal response code used in this study is the Two-dimensional Implicit Thermal-response and Ablation Program, which predicts charring material thermal response and shape change on hypersonic space vehicles. The flow code solves the reacting full Navier-Stokes equations using Data Parallel Line Relaxation method. Recession analyses of stagnation tests conducted in NASA Ames Research Center arc-jet facilities with heat fluxes ranging from 45 to 1100 wcm2 are performed and compared with data for model validation. The ablating material used in these arc-jet tests is Phenolic Impregnated Carbon Ablator. Additionally, computational predictions of surface recession and shape change are in good agreement with measurement for arc-jet conditions of Small Probe Reentry Investigation for Thermal Protection System Engineering.

  19. Incidence and types of complications after ablative oral cancer surgery with primary microvascular free flap reconstruction

    NARCIS (Netherlands)

    Lodders, J.N.; Parmar, S.; Stienen, N.L.M.; Martin, T.J.; Karagozoglu, K.H.; Heymans, M.W.; Nandra, B.; Forouzanfar, T.

    2015-01-01

    BACKGROUND: The aims of the study were 1) to evaluate the incidence and types of postoperative complications after ablative oral cancer surgery with primary free flap reconstruction and 2) identify prognostic variables for postoperative complications. MATERIAL AND METHODS: Desired data was retrieved

  20. Dust ablation in Pluto's atmosphere

    Science.gov (United States)

    Horanyi, Mihaly; Poppe, Andrew; Sternovsky, Zoltan

    2016-04-01

    Based on measurements by dust detectors onboard the Pioneer 10/11 and New Horizons spacecraft the total production rate of dust particles born in the Edgeworth Kuiper Belt (EKB) has been be estimated to be on the order of 5 ṡ 103 kg/s in the approximate size range of 1 - 10 μm. Dust particles are produced by collisions between EKB objects and their bombardment by both interplanetary and interstellar dust particles. Dust particles of EKB origin, in general, migrate towards the Sun due to Poynting-Robertson drag but their distributions are further sculpted by mean-motion resonances as they first approach the orbit of Neptune and later the other planets, as well as mutual collisions. Subsequently, Jupiter will eject the vast majority of them before they reach the inner solar system. The expected mass influx into Pluto atmosphere is on the order of 200 kg/day, and the arrival speed of the incoming particles is on the order of 3 - 4 km/s. We have followed the ablation history as function of speed and size of dust particles in Pluto's atmosphere, and found that volatile rich particles can fully sublimate due to drag heating and deposit their mass in narrow layers. This deposition might promote the formation of the haze layers observed by the New Horizons spacecraft. This talk will explore the constraints on the composition of the dust particles by comparing the altitude of the deposition layers to the observed haze layers.

  1. Experimental Observation of Nonlinear Mode Coupling In the Ablative Rayleigh-Taylor Instability on the NIF

    Science.gov (United States)

    Martinez, David

    2015-11-01

    We investigate on the National Ignition Facility (NIF) the ablative Rayleigh-Taylor (RT) instability in the transition from linear to highly nonlinear regimes. This work is part of the Discovery Science Program on NIF and of particular importance to indirect-drive inertial confinement fusion (ICF) where careful attention to the form of the rise to final peak drive is calculated to prevent the RT instability from shredding the ablator in-flight and leading to ablator mixing into the cold fuel. The growth of the ablative RT instability was investigated using a planar plastic foil with pre-imposed two-dimensional broadband modulations and diagnosed using x-ray radiography. The foil was accelerated for 12ns by the x-ray drive created in a gas-filled Au radiation cavity with a radiative temperature plateau at 175 eV. The dependence on initial conditions was investigated by systematically changing the modulation amplitude, ablator material and the modulation pattern. For each of these cases bubble mergers were observed and the nonlinear evolution of the RT instability showed insensitivity to the initial conditions. This experiment provides critical data needed to validate current theories on the ablative RT instability for indirect drive that relies on the ablative stabilization of short-scale modulations for ICF ignition. This paper will compare the experimental data to the current nonlinear theories. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC.

  2. Femtosecond-laser ablation dynamics of dielectrics: basics and applications for thin films

    DEFF Research Database (Denmark)

    Balling, P.; Schou, Jørgen

    2013-01-01

    -field excitation makes it possible to produce films of materials that are transparent to the laser light. Second, the highly localized excitation reduces the emission of larger material particulates. Third, lasers with ultrashort pulses are shown to be particularly useful tools for the production of nanocluster......Laser ablation of dielectrics by ultrashort laser pulses is reviewed. The basic interaction between ultrashort light pulses and the dielectric material is described, and different approaches to the modeling of the femtosecond ablation dynamics are reviewed. Material excitation by ultrashort laser...... can be described by various rate-equation models in combination with different descriptions of the excited electrons. The optical properties of the highly excited dielectric undergo a rapid change during the laser pulse, which must be included in a detailed modeling of the excitations. The material...

  3. Ablation enhancement of silicon by ultrashort double-pulse laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Xin; Shin, Yung C. [Center for Laser-Based Manufacturing, School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47907 (United States)

    2014-09-15

    In this study, the ultrashort double-pulse ablation of silicon is investigated. An atomistic simulation model is developed to analyze the underlying physics. It is revealed that the double-pulse ablation could significantly increase the ablation rate of silicon, compared with the single pulse ablation with the same total pulse energy, which is totally different from the case of metals. In the long pulse delay range (over 1 ps), the enhancement is caused by the metallic transition of melted silicon with the corresponding absorption efficiency. At ultrashort pulse delay (below 1 ps), the enhancement is due to the electron excitation by the first pulse. The enhancement only occurs at low and moderate laser fluence. The ablation is suppressed at high fluence due to the strong plasma shielding effect.

  4. Photoacoustic characterization of radiofrequency ablation lesions

    Science.gov (United States)

    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.

  5. Physical mechanisms of SiN{sub x} layer structuring with ultrafast lasers by direct and confined laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Rapp, S., E-mail: rapp@hm.edu [Faculty of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstraße 34, 80335 Munich (Germany); Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg, Paul-Gordan-Straße 6, 91052 Erlangen (Germany); Heinrich, G. [Technische Universität Ilmenau, Institut für Physik, Weimarer Straße 25., 98693 Ilmenau (Germany); CiS Forschungsinstitut für Mikrosensorik und Photovoltaik GmbH, Konrad-Zuse-Straße 14, 99099 Erfurt (Germany); Wollgarten, M. [Helmholtz Zentrum Berlin für Materialien und Energie GmbH, Hahn-Meitner-Platz 1, 14109 Berlin (Germany); Huber, H. P. [Faculty of Applied Sciences and Mechatronics, Munich University of Applied Sciences, Lothstraße 34, 80335 Munich (Germany); Schmidt, M. [Friedrich-Alexander-Universität Erlangen-Nürnberg, Lehrstuhl für Photonische Technologien, Konrad-Zuse-Straße 3-5, 91052 Erlangen (Germany)

    2015-03-14

    In the production process of silicon microelectronic devices and high efficiency silicon solar cells, local contact openings in thin dielectric layers are required. Instead of photolithography, these openings can be selectively structured with ultra-short laser pulses by confined laser ablation in a fast and efficient lift off production step. Thereby, the ultrafast laser pulse is transmitted by the dielectric layer and absorbed at the substrate surface leading to a selective layer removal in the nanosecond time domain. Thermal damage in the substrate due to absorption is an unwanted side effect. The aim of this work is to obtain a deeper understanding of the physical laser-material interaction with the goal of finding a damage-free ablation mechanism. For this, thin silicon nitride (SiN{sub x}) layers on planar silicon (Si) wafers are processed with infrared fs-laser pulses. Two ablation types can be distinguished: The known confined ablation at fluences below 300 mJ/cm{sup 2} and a combined partial confined and partial direct ablation at higher fluences. The partial direct ablation process is caused by nonlinear absorption in the SiN{sub x} layer in the center of the applied Gaussian shaped laser pulses. Pump-probe investigations of the central area show ultra-fast reflectivity changes typical for direct laser ablation. Transmission electron microscopy results demonstrate that the Si surface under the remaining SiN{sub x} island is not damaged by the laser ablation process. At optimized process parameters, the method of direct laser ablation could be a good candidate for damage-free selective structuring of dielectric layers on absorbing substrates.

  6. Laser ablation of hepatocellular carcinoma-A review

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A wide range of local thermal ablative therapies have been developed in the treatment of non resectable hepatocellular carcinoma (HCC) in the last decade. Laser ablation (LA) and radiofrequency ablation (RFA) are the two most widely used of these. This article provides an up to date overview of the role of laser ablation in the local treatment of HCC. General principles, technique, image guidance and patient selection are discussed. A review of published data on treatment efficacy, long term outcome and complication rates of laser ablation is included and comparison with RFA made. The role of laser ablation in combination with transcatheter arterial chemoembolisation is also discussed.

  7. Synthesis and characterization of a novel laser ablation sensitive triazene incorporated epoxy resin

    KAUST Repository

    Patole, Archana S.

    2014-01-01

    New triazene monomer was synthesized and further employed as a crosslinking agent partner with epoxy matrix using ethyl methyl imidazole as a curing agent in order to investigate the effect of triazene moieties on polymeric properties for laser ablation application. The synthesized triazene monomer was characterized by analytical and spectroscopic methods, while the surface morphology of resist after laser ablation was visualized by optical laser scanning images and scanning electron microscopy. Thermogravimetrical investigations indicate the loss of nitrogen being the initial thermal decomposition step and exhibit sufficient stabilities for the requirements for laser ablation application. Fourier transform infra-red, nuclear magnetic resonance, and gas chromatography analyses showed the successful synthesis of triazene. The ablation results from the optical laser scanning images revealed that the etching depth could be controlled by varying the concentration of triazene monomer in the formulation of epoxy. The shear strength analysis revealed that that the shear strength increased with increasing the amount of triazene in the formulation of direct ablation sensitive resist. © 2014 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.

  8. First-Principles Investigations on Thermal Conductivity and Average Ionization of CH Ablators Under Extreme Conditions

    Science.gov (United States)

    Hu, S. X.; Goncharov, V. N.; McCrory, R. L.; Skupsky, S.; Collins, L. A.; Kress, J. D.

    2015-11-01

    A plastic CH ablator (polystyrene) is often used for inertial confinement fusion (ICF) target designs. Upon intense laser or x-ray ablations, a CH ablator can be shocked to warm-dense-matter (WDM) conditions. Many-body coupling and quantum electron degeneracy are expected to play an essential role in determining the properties of such warm dense plasmas. Using ab initio methods of quantum molecular dynamics (QMD), we have performed investigations on the principal Hugoniot of a CH ablator, the first-principles equation-of-state table of CH, and its effect on ICF simulations. In this presentation, we focus on the thermal conductivity and average ionization of CH-ablators under a wide range of plasma temperatures and densities. The resulting thermal conductivity (κ) and average ionization () show large differences from the usual model predictions in the WDM regime. These results, being fitted with analytical functions of plasma density and temperature, have been incorporated into radiation -hydrodynamics codes. Their effects on the ICF implosion simulations will be presented. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and the Scientific Campaign 10 at LANL under Contract No. DE-AC52-06NA25396.

  9. Mechanisms of nanoparticle formation by ultra-short laser ablation of metals in liquid environment.

    Science.gov (United States)

    Povarnitsyn, Mikhail E; Itina, Tatiana E; Levashov, Pavel R; Khishchenko, Konstantin V

    2013-03-07

    Laser ablation in liquids is now commonly used to produce colloidal nanoparticles (NPs) that have found numerous applications in different areas. In experiments, NPs of different materials can be rather easily obtained by using laser systems with various pulse durations, shapes, wavelengths, and fluences. In this paper, we focus our attention on metal (gold) NPs produced by ultra-short laser pulses. To better understand the mechanisms of the NPs formation, we perform modeling of femtosecond laser interactions with a gold target in the presence of liquid (water). Simulation of the ablation process over several nanoseconds shows that most of the primary NPs originate from the ablated metastable liquid layer, whereas only a minority is formed by condensation inside the cavitation bubble. These particles will further grow/evaporate, and coagulate during a much longer collision stage in the liquid colloid.

  10. Modification of narrow ablating capillaries under the influence of multiple femtosecond laser pulses

    CERN Document Server

    Gubin, K V; Trunov, V I; Pestryakov, E V

    2016-01-01

    Powerful femtosecond laser pulses that propagate through narrow ablating capillaries cause modification of capillary walls, which is studied experimentally and theoretically. At low intensities, laser-induced periodic surface structures (LIPSS) and porous coating composed of sub-micron particles appear on the walls. At higher intensities, the surface is covered by deposited droplets of the size up to 10 $\\mu$m. In both cases, the ablated material forms a solid plug that completely blocks the capillary after several hundreds or thousands of pulses. The suggested theoretical model indicates that plug formation is a universal effect. It must take place in any narrow tube subject to ablation under the action of short laser pulses.

  11. Hyperthermal Pulsed-Laser Ablation Beams for Film Deposition and Surface Microstructural Engineering

    Energy Technology Data Exchange (ETDEWEB)

    Lowndes, D.H.

    1999-11-08

    This paper presents an overview of pulsed-laser ablation for film deposition and surface microstructure formation. By changing the ambient gas pressure from high vacuum to several Torr (several hundred Pa) and by selecting the pulsed-laser wavelength, the kinetic energy of ablated atoms/ions can be varied from several hundred eV down to {approximately}0.1 eV and films ranging from superhard to nanocrystalline may be deposited. Furthermore, cumulative (multi-pulse) irradiation of a semiconductor surface (e.g. silicon) in an oxidizing gas (0{sub 2}, SF{sub 6}) et atmospheric pressure can produce dense, self-organized arrays of high-aspect-ratio microcolumns or microcones. Thus, a wide range of materials synthesis and processing opportunities result from the hyperthermal flux and reactive growth conditions provided by pulsed-laser ablation.

  12. Wavelength effect on hole shapes and morphology evolution during ablation by picosecond laser pulses

    Science.gov (United States)

    Zhao, Wanqin; Wang, Wenjun; Li, Ben Q.; Jiang, Gedong; Mei, Xuesong

    2016-10-01

    An experimental study is presented of the effect of wavelength on the shape and morphology evolution of micro holes ablated on stainless steel surface by a 10 ps Q-switched Nd:VAN pulsed laser. Two routes of hole development are associated with the visible (532 nm) and near-infrared (1064 nm) laser beams, respectively. The evolution of various geometric shapes and morphological characteristics of the micro holes ablated with the two different wavelengths is comparatively studied for other given processing conditions such as a laser power levels and the number of pulses applied. Plausible explanations, based on the light-materials interaction associated with laser micromachining, are also provided for the discernable paths of geometric and morphological development of holes under laser ablation.

  13. Photonic Doppler velocimetry of laser-ablated ultrathin metals.

    Science.gov (United States)

    Valenzuela, A R; Rodriguez, G; Clarke, S A; Thomas, K A

    2007-01-01

    Obtaining velocity information from the interaction of a laser pulse on a metal layer provides insight into the rapid dynamics of material removal and plasma plume physics during ablation. A traditional approach involves using a velocity interferometer system for any reflector (VISAR) on a reflective metal surface. However, when the target is a thin metal layer, the cohesion of the surface is quickly lost resulting in a large spread of particle velocities that cannot be easily resolved by VISAR. This is due to material ejection"confusing" the VISAR measurement surface, effectively washing out the spatial fringe visibility in the VISAR interferometer. A new heterodyne-based optical velocimeter method is the photonic Doppler velocimeter (PDV). Because PDV tracks motion in a frequency encoded temporal electro-optical signal, velocity information is preserved and allows for multiple velocity components to be recorded simultaneously. The challenge lies in extracting PDV velocity information at short (nanosecond) laser ablation time scales with rapidly varying heterodyne beats by using electronic, optical, and analytical techniques to recover the velocity information from a fleeting signal. Here we show how we have been able to obtain velocity information on the nanosecond time scale and are able to compare it to hydrodynamic simulations. Also, we examine refinements to our PDV system by increasing the bandwidth, utilizing different probes, and sampling different analysis techniques.

  14. Imaging in percutaneous ablation for atrial fibrillation

    Energy Technology Data Exchange (ETDEWEB)

    Maksimovic, Ruzica [Erasmus Medical Center, Department of Radiology, GD Rotterdam (Netherlands); Institute for Cardiovascular Diseases of the University Medical Center, Belgrade (Czechoslovakia); Dill, Thorsten [Kerckhoff-Heart Center, Department of Cardiology, Bad Nauheim (Germany); Ristic, Arsen D.; Seferovic, Petar M. [Institute for Cardiovascular Diseases of the University Medical Center, Belgrade (Czechoslovakia)

    2006-11-15

    Percutaneous ablation for electrical disconnection of the arrhythmogenic foci using various forms of energy has become a well-established technique for treating atrial fibrillation (AF). Success rate in preventing recurrence of AF episodes is high although associated with a significant incidence of pulmonary vein (PV) stenosis and other rare complications. Clinical workup of AF patients includes imaging before and after ablative treatment using different noninvasive and invasive techniques such as conventional angiography, transoesophageal and intracardiac echocardiography, computed tomography (CT) and magnetic resonance imaging (MRI), which offer different information with variable diagnostic accuracy. Evaluation before percutaneous ablation involves assessment of PVs (PV pattern, branching pattern, orientation and ostial size) to facilitate position and size of catheters and reduce procedure time as well as examining the left atrium (presence of thrombi, dimensions and volumes). Imaging after the percutaneous ablation is important for assessment of overall success of the procedure and revealing potential complications. Therefore, imaging methods enable depiction of PVs and the anatomy of surrounding structures essential for preprocedural management and early detection of PV stenosis and other ablation-related procedures, as well as long-term follow-up of these patients. (orig.)

  15. Percutaneous tumor ablation in medical radiology

    Energy Technology Data Exchange (ETDEWEB)

    Vogl, T.J.; Mack, M.G. [University Hospital Frankfurt Univ. (Germany). Inst. for Diagnostic and Interventional Radiology; Helmberger, T.K. [Klinikum Bogenhausen, Academic Teaching Hospital of the Technical Univ. Munich (Germany). Dept. for Diagnostic and Interventional Radiology and Nuclear Medicine; Reiser, M.F. (eds.) [University Hospitals - Grosshadern and Innenstadt Munich Univ. (Germany). Dept. of Clinical Radiology

    2008-07-01

    Thermal ablation has become an integral part of oncology, especially in the field of interventional oncology. This very comprehensive book encompasses the different technologies employed in thermal ablation, its indications and the results achieved in various clinical conditions. The first part of the book clearly explains the basics of thermal ablative techniques such as laser-induced thermotherapy, radiofrequency ablation, microwave ablation, cryotherapy, and localized tumor therapy. The latest developments in the application of minimally invasive therapies in localized neoplastic disease are demonstrated. In the main part of the book, techniques of guiding the applicators to the target structures by use of different imaging tools such as ultrasound, computed tomography and magnetic resonance imaging are discussed. The results are presented for a variety of clinical indications, including liver and lung tumors and metastases and some rather rare conditions involving the kidney, the head and neck, the prostate, and soft tissue structures. A large number of acknowledged experts have contributed to the book, which benefits from a lucid structure and excellent images. (orig.)

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

    Science.gov (United States)

    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.

  17. Characterization of the aerosol produced by infrared femtosecond laser ablation of polyacrylamide gels for the sensitive inductively coupled plasma mass spectrometry detection of selenoproteins

    Energy Technology Data Exchange (ETDEWEB)

    Claverie, Fanny [Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Materiaux, UMR 5254 CNRS- Universite de Pau et des Pays de l' Adour, Helioparc Pau-Pyrenees, 2 Avenue du President Angot, 64053 Pau Cedex 9 (France); Novalase SA, Z.I de la Briqueterie, 6 Impasse du bois de la Grange, 33610 Canejan (France); Pecheyran, Christophe [Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Materiaux, UMR 5254 CNRS- Universite de Pau et des Pays de l' Adour, Helioparc Pau-Pyrenees, 2 Avenue du President Angot, 64053 Pau Cedex 9 (France)], E-mail: Christophe.pecheyran@univ-pau.fr; Mounicou, Sandra [Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Materiaux, UMR 5254 CNRS- Universite de Pau et des Pays de l' Adour, Helioparc Pau-Pyrenees, 2 Avenue du President Angot, 64053 Pau Cedex 9 (France); Ballihaut, Guillaume [Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Materiaux, UMR 5254 CNRS- Universite de Pau et des Pays de l' Adour, Helioparc Pau-Pyrenees, 2 Avenue du President Angot, 64053 Pau Cedex 9 (France); Laboratoire d' Ecologie Moleculaire (Microbiologie), UMR 5254 CNRS- Universite de Pau et des Pays de l' Adour, avenue de l' Universite, B.P. 1155, F-64013 Pau (France); Fernandez, Beatriz [Laboratoire de Chimie Analytique Bio-Inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l' Environnement et les Materiaux, UMR 5254 CNRS- Universite de Pau et des Pays de l' Adour, Helioparc Pau-Pyrenees, 2 Avenue du President Angot, 64053 Pau Cedex 9 (France); Alexis, Joel [Laboratoire Genie de Production, Ecole Nationale d' Ingenieurs de Tarbes, 47 avenue d' Azereix BP 1629, 65016 Tarbes (France)] (and others)

    2009-07-15

    A 2D high repetition rate femtosecond laser ablation strategy (2-mm wide lane) previously developed for the detection of selenoproteins in gel electrophoresis by inductively coupled plasma mass spectrometry was found to increase signal sensitivity by a factor of 40 compared to conventional nanosecond ablation (0.12-mm wide lane) [G. Ballihaut, F. Claverie, C. Pecheyran, S. Mounicou, R. Grimaud and R. Lobinski, Sensitive Detection of Selenoproteins in Gel Electrophoresis by High Repetition Rate Femtosecond Laser Ablation-Inductively Coupled Plasma Mass Spectrometry, Anal. Chem. 79 (2007) 6874-6880]. Such improvement couldn't be explained solely by the difference of amount of material ablated, and then, was attributed to the aerosol properties. In order to validate this hypothesis, the characterization of the aerosol produced by nanosecond and high repetition rate femtosecond laser ablation of polyacrylamide gels was investigated. Our 2D high repetition rate femtosecond laser ablation strategy of 2-mm wide lane was found to produce aerosols of similar particle size distribution compared to nanosecond laser ablation of 0.12-mm wide lane, with 38% mass of particles < 1 {mu}m. However, at high repetition rate, when the ablated surface was reduced, the particle size distribution was shifted toward thinner particle diameter (up to 77% for a 0.12-mm wide lane at 285 {mu}m depth). Meanwhile, scanning electron microscopy was employed to visualize the morphology of the aerosol. In the case of larger ablation, the fine particles ejected from the sample were found to form agglomerates due to higher ablation rate and then higher collision probability. Additionally, investigations of the plasma temperature changes during the ablation demonstrated that the introduction of such amount of polyacrylamide gel particles had very limited impact on the ICP source ({delta}T{approx} 25 {+-} 5 K). This suggests that the cohesion forces between the thin particles composing these large

  18. Reduction of picosecond laser ablation threshold and damage via nanosecond pre-pulse for removal of dielectric layers on silicon solar cells

    Science.gov (United States)

    Brand, A. A.; Meyer, F.; Nekarda, J.-F.; Preu, R.

    2014-10-01

    Laser microstructuring of thin dielectric layers on sensitive electronic devices, such as crystalline silicon solar cells, requires a careful design of the laser ablation process. For instance, degradation of the substrate's crystallinity can vastly decrease minority carrier lifetime and consequently impair the efficiency of such devices. Short-pulse laser ablation seems well suited for clean and spatially confined structuring because of the small heat-affected zone in the remaining substrate material [Dube and Gonsiorawski in Conference record of the twenty first IEEE photovoltaic specialists conference, 624-628 1990]. The short-time regimes, however, generate steep temperature gradients that can lead to amorphization of the remaining silicon surface. By `heating' the substrate via a non-ablative laser pulse in the nanosecond regime before the actual ablation pulse occurs we are able to prevent amorphization of the surface of the silicon solar cell substrate, while lowering the ablation thresholds of a SiNx layer on crystalline silicon wafers.

  19. A study of particle generation during laser ablation with applications

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chunyi [Univ. of California, Berkeley, CA (United States)

    2005-01-01

    A study has been made of the generation of particles during laser ablation and has included size distribution measurements and observation of the formation processes. The particle size distribution with respect to different laser parameters was obtained in-line using a differential mobility analyzer (DMA) and a particle counter. The experimental results show that the particle size varies with laser energy, laser pulsewidth, ambient gas flow rate and sample properties. The results serve as a basis for controlling the size of nanoparticles generated by laser ablation. Laser shadowgraph imaging was used to study mass ejection processes and mechanisms. At higher laser irradiance, some particles were ejected in the liquid and even in the solid phase. Time-resolved images show the propagation of the shockwaves: external shockwaves propagate outward and decelerate, and internal shockwaves reflect back and forth between the gas contact surface and the sample surface. The internal shockwave is proposed to cause the ejection of liquid particles when the internal shockwave strikes the liquid molten layer. A simulation based on vapor plume expansion was carried out and provides satisfactory agreement with experimental results. Different material properties result in different particle ejection behavior:particle ejection for most materials including metals result in a conically shaped envelope for the ejected material while ejection for silicon resembles a liquid jet. The difference in density change when the materials melt was proposed to be an important factor in the different ejection behavior. The characteristics of particles generated by laser ablation have a strong influence on the chemical analysis of the irradiated sample. Large particles are more difficult to completely vaporize and ionize, and induced preferential vaporization causes fractionation (i.e. a detected chemical composition that differs from the sample material). Large particles also result in spikes in

  20. Interactive Volumetry Of Liver Ablation Zones

    CERN Document Server

    Egger, Jan; Brandmaier, Philipp; Seider, Daniel; Gawlitza, Matthias; Strocka, Steffen; Voglreiter, Philip; Dokter, Mark; Hofmann, Michael; Kainz, Bernhard; Hann, Alexander; Chen, Xiaojun; Alhonnoro, Tuomas; Pollari, Mika; Schmalstieg, Dieter; Moche, Michael

    2015-01-01

    Percutaneous radiofrequency ablation (RFA) is a minimally invasive technique that destroys cancer cells by heat. The heat results from focusing energy in the radiofrequency spectrum through a needle. Amongst others, this can enable the treatment of patients who are not eligible for an open surgery. However, the possibility of recurrent liver cancer due to incomplete ablation of the tumor makes post-interventional monitoring via regular follow-up scans mandatory. These scans have to be carefully inspected for any conspicuousness. Within this study, the RF ablation zones from twelve post-interventional CT acquisitions have been segmented semi-automatically to support the visual inspection. An interactive, graph-based contouring approach, which prefers spherically shaped regions, has been applied. For the quantitative and qualitative analysis of the algorithm's results, manual slice-by-slice segmentations produced by clinical experts have been used as the gold standard (which have also been compared among each o...

  1. Kinetic depletion model for pellet ablation

    Energy Technology Data Exchange (ETDEWEB)

    Kuteev, Boris V. [State Technical Univ., St. Petersburg (Russian Federation)

    2001-11-01

    A kinetic model for depletion effect, which determines pellet ablation when the pellet passes a rational magnetic surface, is formulated. The model predicts a moderate decrease of the ablation rate compared with the earlier considered monoenergy versions [1, 2]. For typical T-10 conditions the ablation rate reduces by a reactor of 2.5 when the 1-mm pellet penetrates through the plasma center. A substantial deceleration of pellets -about 15% per centimeter of low shire rational q region; is predicted. Penetration for Low Field Side and High Field Side injections is considered taking into account modification of the electron distribution function by toroidal magnetic field. It is shown that Shafranov shift and toroidal effects yield the penetration length for HFS injection higher by a factor of 1.5. This fact should be taken into account when plasma-shielding effects on penetration are considered. (author)

  2. Deep Dive Topic: Choosing between ablators

    Energy Technology Data Exchange (ETDEWEB)

    Hurricane, O. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Thomas, C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Olson, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-07-14

    Recent data on implosions using identical hohlraums and very similar laser drives underscores the conundrum of making a clear choice of one ablator over another. Table I shows a comparison of Be and CH in a nominal length, gold, 575 μm-diameter, 1.6 mg/cc He gas-fill hohlraum while Table II shows a comparison of undoped HDC and CH in a +700 length, gold, 575 μm diameter, 1.6 mg/cc He gas fill hohlraum. As can be seen in the tables, the net integrated fusion performance of these ablators is the same to within error bars. In the case of the undoped HDC and CH ablators, the hot spot shapes of the implosions were nearly indistinguishable for the experiments listed in Table II.

  3. Complete regeneration of ablated eyestalk in penaeid prawn, Penaeus monodon

    Digital Repository Service at National Institute of Oceanography (India)

    Desai, U.M.; Achuthankutty, C.T.

    Ablation of one eyestalk is generally practised in all commercial prawn hatcheries to induce gonad maturation and spawning. An observation was made that the ablated eyestalk of spent females of the tiger prawn Penaeus monodon was completely...

  4. Alcohol septal ablation in patients with hypertrophic obstructive cardiomyopathy

    DEFF Research Database (Denmark)

    Jensen, Morten K; Prinz, Christian; Horstkotte, Dieter;

    2013-01-01

    The infarction induced by alcohol septal ablation (ASA) may predispose to arrhythmia and sudden cardiac death (SCD).......The infarction induced by alcohol septal ablation (ASA) may predispose to arrhythmia and sudden cardiac death (SCD)....

  5. Thermal ablation of liver metastases from colorectal cancer: radiofrequency, microwave and laser ablation therapies.

    Science.gov (United States)

    Vogl, Thomas J; Farshid, Parviz; Naguib, Nagy N N; Darvishi, Abbas; Bazrafshan, Babak; Mbalisike, Emmanuel; Burkhard, Thorsten; Zangos, Stephan

    2014-07-01

    Surgery is currently considered the treatment of choice for patients with colorectal cancer liver metastases (CRLM) when resectable. The majority of these patients can also benefit from systemic chemotherapy. Recently, local or regional therapies such as thermal ablations have been used with acceptable outcomes. We searched the medical literature to identify studies and reviews relevant to radiofrequency (RF) ablation, microwave (MW) ablation and laser-induced thermotherapy (LITT) in terms of local progression, survival indexes and major complications in patients with CRLM. Reviewed literature showed a local progression rate between 2.8 and 29.7 % of RF-ablated liver lesions at 12-49 months follow-up, 2.7-12.5 % of MW ablated lesions at 5-19 months follow-up and 5.2 % of lesions treated with LITT at 6-month follow-up. Major complications were observed in 4-33 % of patients treated with RF ablation, 0-19 % of patients treated with MW ablation and 0.1-3.5 % of lesions treated with LITT. Although not significantly different, the mean of 1-, 3- and 5-year survival rates for RF-, MW- and laser ablated lesions was (92.6, 44.7, 31.1 %), (79, 38.6, 21 %) and (94.2, 61.5, 29.2 %), respectively. The median survival in these methods was 33.2, 29.5 and 33.7 months, respectively. Thermal ablation may be an appropriate alternative in patients with CRLM who have inoperable liver lesions or have operable lesions as an adjunct to resection. However, further competitive evaluation should clarify the efficacy and priority of these therapies in patients with colorectal cancer liver metastases.

  6. Palliative Treatment of Rectal Carcinoma Recurrence Using Radiofrequency Ablation

    Energy Technology Data Exchange (ETDEWEB)

    Mylona, Sophia, E-mail: mylonasophia@yahoo.com; Karagiannis, Georgios, E-mail: gekaragiannis@yahoo.gr; Patsoura, Sofia, E-mail: sofia.patsoura@yahoo.gr [Hellenic Red Cross Hospital ' Korgialenio-Benakio' (Greece); Galani, Panagiota, E-mail: gioulagalani@yahoo.com [Amalia Fleming Hospital (Greece); Pomoni, Maria, E-mail: marypomoni@gmail.com [Evgenidion Hospital (Greece); Thanos, Loukas, E-mail: loutharad@yahoo.com [Sotiria Hospital (Greece)

    2012-08-15

    Purpose: To evaluate the safety and efficacy of CT-guided radiofrequency (RF) ablation for the palliative treatment of recurrent unresectable rectal tumors. Materials and Methods: Twenty-seven patients with locally recurrent rectal cancer were treated with computed tomography (CT)-guided RF ablation. Therapy was performed with the patient under conscious sedation with a seven- or a nine-array expandable RF electrode for 8-10 min at 80-110 Degree-Sign C and a power of 90-110 W. All patients went home under instructions the next day of the procedure. Brief Pain Inventory score was calculated before and after (1 day, 1 week, 1 month, 3 months, and 6 months) treatment. Results: Complete tumor necrosis rate was 77.8% (21 of a total 27 procedures) despite lesion location. BPI score was dramatically decreased after the procedure. The mean preprocedure BPI score was 6.59, which decreased to 3.15, 1.15, and 0.11 at postprocedure day 1, week 1, and month 1, respectively, after the procedure. This decrease was significant (p < 0.01 for the first day and p < 0.001 for the rest of the follow-up intervals (paired Student t test; n - 1 = 26) for all periods during follow-up. Six patients had partial tumor necrosis, and we were attempted to them with a second procedure. Although the necrosis area showed a radiographic increase, no complete necrosis was achieved (secondary success rate 65.6%). No immediate or delayed complications were observed. Conclusion: CT-guided RF ablation is a minimally invasive, safe, and highly effective technique for treatment of malignant rectal recurrence. The method is well tolerated by patients, and pain relief is quickly achieved.

  7. CT-guided radiofrequency (RF) ablation of osteoid osteoma. Clinical long-term results; CT-gesteuerte Radiofrequenz(RF)-Ablation von Osteoidosteomen. Klinische Langzeitergebnisse

    Energy Technology Data Exchange (ETDEWEB)

    Schmidt, Diethard; Clasen, S.; Schaefer, J.F.; Rempp, H.; Koenig, C.W.; Claussen, C.D. [Universitaetsklinikum Tuebingen (Germany). Abt. fuer Diagnostische und Interventionelle Radiologie; Duda, S.; Truebenbach, J. [Juedisches Krankenhaus, Berlin (Germany). Radiologen Praxis; Erdtmann, B. [Radiologie Zentrum Stuttgart, Bad Cannstatt (Germany). Praxis; Pereira, P.L. [SLK-Kliniken, Heilbronn (Germany). Klinik fuer Radiologie, Minimal-Invasive Therapien und Nuklearmedizin

    2011-04-15

    Purpose: To evaluate CT-guided radiofrequency (RF) ablation of osteoid osteoma using internally cooled monopolar RF electrodes for technical success, complications and clinical long-term success. Materials and Methods: Between April 1999 and July 2009, 23 patients were treated under general anesthesia with CT-guided RF ablation using an internally cooled monopolar single RF electrode (Cool-tip, Valleylab, TycoHealthcare, Boulder, USA; active tip: 10 mm). For the removal of the nidus, we used either a manual or an automated drill. The technical success was evaluated by a CT scan (MSCT, Siemens Medical Solutions, Forchheim). The clinical long-term success was investigated by questioning patients prior to discharge, and after 6, 12 and 18 months. After 18 months, patients were interviewed on an annual basis. Results: The technical success rate was 100 %. The nidus was located in n = 19 cases at the lower extremity and in n = 4 cases at the upper extremity. Minor complications were observed for n = 2 patients. The mean hospitalization time was 1.5 d (1-2 d). The mean follow-up was 75.9 months (18-120 months) for n = 23 patients. No local recurrence was observed. One patient had intermediate pain one week after RF ablation without recurrent symptoms. Conclusion: CT-guided RF ablation using an internally cooled monopolar single RF electrode is an effective and safe minimally invasive method for the treatment of osteoid osteoma with excellent clinical long-term success. (orig.)

  8. Stereotactic Body Radiotherapy and Ablative Therapies for Lung Cancer.

    Science.gov (United States)

    Abbas, Ghulam; Danish, Adnan; Krasna, Mark J

    2016-07-01

    The treatment paradigm for early stage lung cancer and oligometastatic disease to the lung is rapidly changing. Ablative therapies, especially stereotactic body radiation therapy, are challenging the surgical gold standard and have the potential to be the standard for operable patients with early stage lung cancer who are high risk due to co- morbidities. The most commonly used ablative modalities include stereotactic body radiation therapy, microwave ablation, and radiofrequency ablation.

  9. Thermal Ablation for Benign Thyroid Nodules: Radiofrequency and Laser

    Energy Technology Data Exchange (ETDEWEB)

    Baek, Jung Hwan; Lee, Jeong Hyun [University of Ulsan College of Medicine, Asan Medical Center, Seoul (Korea, Republic of); Valcavi, Roberto [Endocrinology Division and Thyroid Disease Center, Arcispedale Santa Maria Nuova, Reggio Emilia (Italy); Pacella, Claudio M. [Diagnostic Imaging and Interventional Radiology Department, Ospedale Regina Apostolorum, Albano Laziale-Rome (IT); Rhim, Hyun Chul [Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of); Na, Dong Kyu [Human Medical Imaging and Intervention Center, Seoul (Korea, Republic of)

    2011-10-15

    Although ethanol ablation has been successfully used to treat cystic thyroid nodules, this procedure is less effective when the thyroid nodules are solid. Radiofrequency (RF) ablation, a newer procedure used to treat malignant liver tumors, has been valuable in the treatment of benign thyroid nodules regardless of the extent of the solid component. This article reviews the basic physics, techniques, applications, results, and complications of thyroid RF ablation, in comparison to laser ablation.

  10. Subcellular analysis by laser ablation electrospray ionization mass spectrometry

    Science.gov (United States)

    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.

  11. Efficacy and satisfaction rate comparing endometrial ablation by rollerball electrocoagulation to uterine balloon thermal ablation in a randomised controlled trial.

    NARCIS (Netherlands)

    Zon-Rabelink, I.A.A. van; Vleugels, M.P.; Merkus, J.M.W.M.; Graaf, R.M. de

    2004-01-01

    OBJECTIVE: To compare two methods of endometrial ablation, hysteroscopic rollerball electrocoagulation (RBE) and non-hysteroscopic uterine balloon thermal ablation (Thermachoice trade mark ), regarding efficacy for reducing dysfunctional uterine bleeding and patients satisfaction rate. METHODS: A ra

  12. Experimental measurement of ablation effects in plasma armature railguns

    Energy Technology Data Exchange (ETDEWEB)

    Parker, J.V.; Parsons, W.M.

    1986-01-01

    Experimental evidence supporting the importance of ablation in plasma armature railguns is presented. Experiments conducted using the HYVAX and MIDI-2 railguns are described. Several indirect effects of ablation are identified from the experimental results. An improved ablation model of plasma armature dynamics is proposed which incorporates the restrike process.

  13. Cardiac ablation by transesophageal high intensity focused ultrasound

    Institute of Scientific and Technical Information of China (English)

    JIANG Chen-xi; YU Rong-hui; MA Chang-sheng

    2010-01-01

    @@ Cardiac ablation is an important modality of invasive therapy in modern cardiology, especially in the treatment of arrhythmias, as well as other diseases such as hypertrophic obstructive cardiomyopathy (HOCM). Since Huang et al1 used radiofrequency (RF) to ablate canine atrial ventricular junction, RF has developed into the leading energy source in catheter ablation of arrhythmias.

  14. Monitoring of tumor radio frequency ablation using derivative spectroscopy

    NARCIS (Netherlands)

    Spliethoff, J.W.; Tanis, E.; Evers, Daniel James; Hendriks, B.H.; Prevoo, W.; Ruers, T.J.M.

    2014-01-01

    Despite the widespread use of radio frequency (RF) ablation, an effective way to assess thermal tissue damage during and after the procedure is still lacking. We present a method for monitoring RF ablation efficacy based on thermally induced methemoglobin as a marker for full tissue ablation. Diffus

  15. Tangle-Free Mesh Motion for Ablation Simulations

    Science.gov (United States)

    Droba, Justin

    2016-01-01

    Problems involving mesh motion-which should not be mistakenly associated with moving mesh methods, a class of adaptive mesh redistribution techniques-are of critical importance in numerical simulations of the thermal response of melting and ablative materials. Ablation is the process by which material vaporizes or otherwise erodes due to strong heating. Accurate modeling of such materials is of the utmost importance in design of passive thermal protection systems ("heatshields") for spacecraft, the layer of the vehicle that ensures survival of crew and craft during re-entry. In an explicit mesh motion approach, a complete thermal solve is first performed. Afterwards, the thermal response is used to determine surface recession rates. These values are then used to generate boundary conditions for an a posteriori correction designed to update the location of the mesh nodes. Most often, linear elastic or biharmonic equations are used to model this material response, traditionally in a finite element framework so that complex geometries can be simulated. A simple scheme for moving the boundary nodes involves receding along the surface normals. However, for all but the simplest problem geometries, evolution in time following such a scheme will eventually bring the mesh to intersect and "tangle" with itself, inducing failure. This presentation demonstrates a comprehensive and sophisticated scheme that analyzes the local geometry of each node with help from user-provided clues to eliminate the tangle and enable simulations on a wide-class of difficult problem geometries. The method developed is demonstrated for linear elastic equations but is general enough that it may be adapted to other modeling equations. The presentation will explicate the inner workings of the tangle-free mesh motion algorithm for both two and three-dimensional meshes. It will show abstract examples of the method's success, including a verification problem that demonstrates its accuracy and

  16. Ablation of hard dental tissues with an ArF-pulsed excimer laser

    Science.gov (United States)

    Neev, Joseph; Raney, Daniel; Whalen, William E.; Fujishige, Jack T.; Ho, Peter D.; McGrann, John V.; Berns, Michael W.

    1991-06-01

    The interaction of 15 ns pulses from an ArF excimer laser with hard dental tissue was investigated for the purpose of obtaining practical information on the ablation process. Dark field fast photography utilizing an auxiliary, 15 ns Nd:Yag laser 'probe', was used to study the ablation plume dynamics as a function of time, luminescence were studied at different fluence levels and prr. Dentin ablation was found to be about four times as efficient as ablation of enamel in the higher fluence levels tested (> 10 J/cm2) and about twice as efficient as the ablation in the lower fluence regime (approximately equals 1 J/cm2). The dentin etch depth per pulse was found to increase exponentially with fluence (at least up to the tested level of 11 J/cm2), while in enamel the etch depth per pulse appears to increase logarithmically with fluence. Dentin ablation yields a larger, more dense plume which can be ejected (depending on the fluence level) to a height of several millimeters above the surface with observed ejection velocity in access of 1200 m/s. The dentin plume consisted of a relatively uniform particle size distribution (0.1 micrometers to 10 micrometers in diameter). Enamel ablation, on the other hand, yields a smaller observed ejection velocities (about 800 m/s), and a much smaller plume of fine particles (about 0.1 micrometers in diameter) and gases, confined to within 0.5 mm of the surface. In addition, an even smaller amount of highly non-uniform debris, (from ten to several hundred micrometers in size) is observed to be ejected to higher levels, and reach roughly half the height of the corresponding dentin plume for similar fluence levels. Although both dentin and enamel yield lower ablation efficiencies at 1 Hz, no significant difference is detected between the ablation efficiency at 5 Hz and ablation 10 Hz prr. Both materials remained within 20 degree(s)C of room temperature even at fluences as high as 20 J/cm2 and prr as high as 10 Hz for enamel and 20 Hz for

  17. Research on ablation process of constant elastic alloy with femtosecond laser in solution medium

    Science.gov (United States)

    Deng, Guilin; Su, Wenyi; Duan, Ji'an; Fan, Nannan; Sun, Xiaoyan; Zhou, Jianying; Wang, Cong; Yin, Kai; Dong, Xinran; Hu, Youwang

    2016-09-01

    Constant elastic alloy is widely used material with high applied performance. In order to develop the application of constant elastic alloy, laser ablation of constant elastic alloy in different ablation mediums was investigated with different femtosecond lasers. Constant elastic alloy was ablated in solution with different ethanol contents and different thicknesses of the liquid layer above the target material and for comparison, in air. Also, the effects of laser energy and laser pulses of femtosecond laser on the morphology are studied. The effects of the position of the laser focus relative to the target surface were also discussed. The experimental results indicate that larger laser-induced area and smaller depth of craters tend to be obtained in solution than in air. The laser-induced area firstly increases and then decreases, and depths of craters decrease at first and increase later with the increase in ethanol content. Furthermore, the larger were energy of laser pulses, the larger were laser-induced area and deeper craters made in all different ablation solutions.

  18. Double-pulse laser ablation coupled to laser-induced breakdown spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Glaus, Reto, E-mail: reglaus@ufl.edu; Hahn, David W.

    2014-08-01

    Laser ablation coupled to laser-induced breakdown spectroscopy (LA-LIBS) is an analytical method, which minimizes sample matrix effects typically found in quantitative LIBS-based direct solid analyses. This paper reports the application of double-pulse laser ablation (DP-LA) to improve the analyte response and the achievable precisions of LA-LIBS. Two coaxial laser beams were applied at the ablation site and the analytical signals were then collected from a second free-standing LIBS plasma downstream of the ablation site. Signal improvements of up to one order of magnitude were observed compared to single-pulse LA-LIBS. The effect of the interpulse delay on the observed signal-to-noise ratios was studied and the quantification capabilities of the optimized DP-LA-LIBS setup were investigated for manganese and iron in a broad range of different alloy types. A linear response was observed for manganese across the different matrices, allowing for nonmatrix-matched calibrations. Matrix effects were observed when analyzing aluminum samples, which, however, could be compensated for by applying iron as internal standard. Size distributions of the ablated material and electron density measurements provide additional insight into the double-pulse process, with additional future work suggested. - Highlights: • Double-pulse laser ablation was coupled to laser-induced breakdown spectroscopy. • Nonmatrix-matched calibration of manganese in various alloys was performed. • Improved sensitivities and precisions compared to single-pulse LA were demonstrated. • Remaining matrix effects and internal standardization are discussed.

  19. Imaging Features of Radiofrequency Ablation with Heat-Deployed Liposomal Doxorubicin in Hepatic Tumors

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Cheng William, E-mail: williamhongcheng@gmail.com; Chow, Lucy, E-mail: lucychow282@gmail.com [National Institutes of Health, Center for Interventional Oncology, Clinical Center (United States); Turkbey, Evrim B., E-mail: evrimbengi@yahoo.com [National Institutes of Health, Radiology and Imaging Sciences, Clinical Center (United States); Lencioni, Riccardo, E-mail: riccardo.lencioni@med.unipi.it [Pisa University Hospital, Division of Diagnostic Imaging and Intervention, Department of Hepatology and Liver Transplantation (Italy); Libutti, Steven K., E-mail: slibutti@montefiore.org [Albert Einstein College of Medicine, Montefiore-Einstein Center for Cancer Care, Department of Surgery (United States); Wood, Bradford J., E-mail: bwood@nih.gov [National Institutes of Health, Center for Interventional Oncology, Clinical Center (United States)

    2016-03-15

    IntroductionThe imaging features of unresectable hepatic malignancies in patients who underwent radiofrequency ablation (RFA) in combination with lyso-thermosensitive liposomal doxorubicin (LTLD) were determined.Materials and MethodsA phase I dose escalation study combining RFA with LTLD was performed with peri- and post- procedural CT and MRI. Imaging features were analyzed and measured in terms of ablative zone size and surrounding penumbra size. The dynamic imaging appearance was described qualitatively immediately following the procedure and at 1-month follow-up. The control group receiving liver RFA without LTLD was compared to the study group in terms of imaging features and post-ablative zone size dynamics at follow-up.ResultsPost-treatment scans of hepatic lesions treated with RFA and LTLD have distinctive imaging characteristics when compared to those treated with RFA alone. The addition of LTLD resulted in a regular or smooth enhancing rim on T1W MRI which often correlated with increased attenuation on CT. The LTLD-treated ablation zones were stable or enlarged at follow-up four weeks later in 69 % of study subjects as opposed to conventional RFA where the ablation zone underwent involution compared to imaging acquired immediately after the procedure.ConclusionThe imaging features following RFA with LTLD were different from those after standard RFA and can mimic residual or recurrent tumor. Knowledge of the subtle findings between the two groups can help avoid misinterpretation and proper identification of treatment failure in this setting. Increased size of the LTLD-treated ablation zone after RFA suggests the ongoing drug-induced biological effects.

  20. MRI-guided percutaneous laser ablation of small renal cell carcinoma: Initial clinical experience

    Energy Technology Data Exchange (ETDEWEB)

    Kariniemi, Juho; Ojala, Risto; Hellstroem, Pekka; Sequeiros, Roberto Blanco (Dept. of Radiology, Dept. of Surgery, Oulu Univ. Hospital, Oulu (Finland)), e-mail: juho.kariniemi@oulu.fi

    2010-05-15

    Background: The number of detected small renal cell carcinomas (RCCs) has been rising, largely due to advances in imaging. Open surgical resection is the standard management of small RCCs; however, imaging-guided percutaneous ablative therapies have emerged as a minimally invasive treatment alternative, especially for patients who are poor candidates for surgery. Purpose: To evaluate the initial clinical experience of magnetic resonance imaging (MRI)-guided percutaneous laser ablation of small RCCs. Material and Methods: Eight patients with 10 tumors were treated with percutaneous MRI-guided laser ablation. All tumors (diameter range 1.5-3.8 cm, mean 2.7 cm) were biopsy-proven RCCs. By using a 0.23 T open MRI system and general anesthesia in patients, one to four (mean 2.6) laser fibers were placed and the tumors were ablated under near real-time MRI control by observing the signal void caused by the temperature change in the heated tissue. The treatment was considered successful if the tumor showed no contrast enhancement at follow-up imaging. Results: All except one tumor were successfully ablated in one session. The first patient treated showed enhancing residual tumor in post-procedural MRI; she has thus far declined retreatment. One complication, a myocardial infarction, occurred; all other patients tolerated the procedure well. No local recurrence was discovered during the follow-up (range 12-30 months, mean 20 months). Conclusion: In this small group of patients with relatively short follow-up period, MRI-guided percutaneous laser ablation proved to be a promising treatment option for small RCCs

  1. Ultrasonography-guided percutaneous radiofrequency ablation for cervical lymph node metastasis from thyroid carcinoma

    Directory of Open Access Journals (Sweden)

    Liping Wang

    2014-01-01

    Full Text Available Purpose: The aim was to explore the efficacy and safety of ultrasonography-guided percutaneous radiofrequency ablation (RFA for cervical lymph node metastases from thyroid carcinoma. Materials and Methods: Eight patients with previous total thyroidectomy and radioiodine therapy were enrolled in this study. A total of 20 cervical lymph node metastases were confirmed by percutaneous biopsy. Participants underwent ultrasonography-guided RFA treatment for all confirmed metastatic lymph nodes. Contrast-enhanced ultrasound (CEUS and sonoelastography were performed to rapidly evaluate treatment responses before and shortly after RFA. Routine follow-up consisted of conventional US, CEUS, sonoelastography, thyroglobulin level, and necessary fine needle aspiration cytology. Results: All eight patients were successfully treated without obvious complications. Post-RFA CEUS showed that total metastatic lymph nodes were ablated. The sonoelastographic score of ablated area elevated significantly shortly after RFA (P < 0.001. With a mean follow-up of 9.4 ± 5.1 months, there were no evidences of recurrence at ablated sites; however, two new cervical recurrent lymph nodes occurred in one case, which was successfully ablated as well. The mass volume shrinkages of the ablated nodes were observed in all cases. We found that 5 treated lymph nodes disappeared, 4 were reduced more than 80%, 9 were reduced between 50% and 80%, and 2 were reduced less than 50%. At the last follow-up evaluation, the serum thyroglobulin levels had decreased in 6 of 8 patients. Conclusion: Ultrasonography-guided percutaneous RFA for cervical lymph node metastasis of thyroid malignancy is a feasible, effective, and safe therapy. This procedure shows a nonsurgical therapeutic option for metastatic lymph nodes in patients with difficult reoperations or inoperations, it may reduce or delay a large number of highly invasive repeated neck dissections.

  2. Laser ablation of borosilicate glass with high power shaped UV nanosecond laser pulses

    Science.gov (United States)

    von Witzendorff, Philipp; Bordin, Andrea; Suttmann, Oliver; Patel, Rajesh S.; Bovatsek, James; Overmeyer, Ludger

    2016-03-01

    The application of thin borosilicate glass as interposer material requires methods for separation and drilling of this material. Laser processing with short and ultra-short laser pulses have proven to enable high quality cuts by either direct ablation or internal glass modification and cleavage. A recently developed high power UV nanosecond laser source allows for pulse shaping of individual laser pulses. Thus, the pulse duration, pulse bursts and the repetition rate can be set individually at a maximum output power of up to 60 W. This opens a completely new process window, which could not be entered with conventional Q-switched pulsed laser sources. In this study, the novel pulsed UV laser system was used to study the laser ablation process on 400 μm thin borosilicate glass at different pulse durations ranging from 2 - 10 ns and a pulse burst with two 10 ns laser pulses with a separation of 10 ns. Single line scan experiments were performed to correlate the process parameters and the laser pulse shape with the ablation depth and cutting edge chipping. Increasing the pulse duration within the single pulse experiments from 2 ns to longer pulse durations led to a moderate increase in ablation depth and a significant increase in chipping. The highest material removal was achieved with the 2x10 ns pulse burst. Experimental data also suggest that chipping could be reduced, while maintaining a high ablation depth by selecting an adequate pulse overlap. We also demonstrate that real-time combination of different pulse patterns during drilling a thin borosilicate glass produced holes with low overall chipping at a high throughput rate.

  3. A review of the safety aspects of radio frequency ablation

    Directory of Open Access Journals (Sweden)

    Abhishek Bhaskaran

    2015-09-01

    Full Text Available In light of recent reports showing high incidence of silent cerebral infarcts and organized atrial arrhythmias following radiofrequency (RF atrial fibrillation (AF ablation, a review of its safety aspects is timely. Serious complications do occur during supraventricular tachycardia (SVT ablations and knowledge of their incidence is important when deciding whether to proceed with ablation. Evidence is emerging for the probable role of prophylactic ischemic scar ablation to prevent VT. This might increase the number of procedures performed. Here we look at the various complications of RF ablation and also the methods to minimize them. Electronic database was searched for relevant articles from 1990 to 2015. With better awareness and technological advancements in RF ablation the incidence of complications has improved considerably. In AF ablation it has decreased from 6% to less than 4% comprising of vascular complications, cardiac tamponade, stroke, phrenic nerve injury, pulmonary vein stenosis, atrio-esophageal fistula (AEF and death. Safety of SVT ablation has also improved with less than 1% incidence of AV node injury in AVNRT ablation. In VT ablation the incidence of major complications was 5–11%, up to 3.4%, up to 1.8% and 4.1–8.8% in patients with structural heart disease, without structural heart disease, prophylactic ablations and epicardial ablations respectively. Vascular and pericardial complications dominated endocardial and epicardial VT ablations respectively. Up to 3% mortality and similar rates of tamponade were reported in endocardial VT ablation. Recent reports about the high incidence of asymptomatic cerebral embolism during AF ablation are concerning, warranting more research into its etiology and prevention.

  4. Development and fundamental investigation of Laser Ablation Glow Discharge Time-Of-Flight Mass Spectrometry (LA-GD-TOFMS)

    Energy Technology Data Exchange (ETDEWEB)

    Tarik, Mohamed [ETH Zurich, D-CHAB, Laboratory of inorganic chemistry, Wolfgang-Pauli-Str. 10, 8093 Zurich (Switzerland); Lotito, Giovanni [ETH Zurich, D-CHAB, Laboratory of inorganic chemistry, Wolfgang-Pauli-Str. 10, 8093 Zurich (Switzerland); TOFWERK AG, Uttigenstr. 22, 3600 Thun (Switzerland); Whitby, James A. [TOFWERK AG, Uttigenstr. 22, 3600 Thun (Switzerland); Mechanics of Materials and Nanostructures Laboratory, Empa - Materials Science and Technology, Feuerwerkerstr. 39, 3602 Thun (Switzerland); Koch, Joachim [ETH Zurich, D-CHAB, Laboratory of inorganic chemistry, Wolfgang-Pauli-Str. 10, 8093 Zurich (Switzerland); Fuhrer, Katrin; Gonin, Marc [TOFWERK AG, Uttigenstr. 22, 3600 Thun (Switzerland); Michler, Johann [Mechanics of Materials and Nanostructures Laboratory, Empa - Materials Science and Technology, Feuerwerkerstr. 39, 3602 Thun (Switzerland); Bolli, Jean-Luc [Ecole d' ingenieurs de Geneve, 4 Prairie, 1202 Geneva (Switzerland); Guenther, Detlef [ETH Zurich, D-CHAB, Laboratory of inorganic chemistry, Wolfgang-Pauli-Str. 10, 8093 Zurich (Switzerland)], E-mail: guenther@inorg.chem.ethz.ch

    2009-03-15

    Glow Discharge (GD) spectroscopy is a well known and accepted technique for the bulk and surface composition analysis, while laser ablation (LA) provides analysis with high spatial-resolution analysis in LIBS (laser-induced breakdown spectroscopy) or when coupled to inductively coupled plasma spectrometry (ICP-OES or ICP-MS). This work concerns the construction of a Laser Ablation Glow Discharge Time-Of-Flight Mass Spectrometry (LA-GD-TOFMS) instrument to study the analytical capabilities resulting from the interaction of a laser-generated sample plume with a pulsed glow discharge. Two ablation configurations were studied in detail. In a first approach, the laser-generated plume was introduced directly into the GD, while the second approach generated the plume inside the GD. The ablated material was introduced at different times with respect to the discharge pulse in order to exploit the efficient ionization in the GD plasma. For both LA-GD configurations, direct ablation into the afterglow of the pulsed glow discharge leads to an ion signal enhancement of up to a factor of 7, as compared to the ablation process alone under the same experimental conditions. The LA-GD enhancement was found to occur exclusively in the GD afterglow, with a maximum ablation S/N occurring in a few hundred microseconds after the termination of the glow discharge. The duration of the enhanced signal is about two milliseconds. Both the laser pulse energy and the position of the ablation plume (with respect to the sampling orifice) were found to affect the amount of mass entering the afterglow region and consequently, the enhancement factor of ionization.

  5. Development and fundamental investigation of Laser Ablation Glow Discharge Time-Of-Flight Mass Spectrometry (LA-GD-TOFMS)

    Science.gov (United States)

    Tarik, Mohamed; Lotito, Giovanni; Whitby, James A.; Koch, Joachim; Fuhrer, Katrin; Gonin, Marc; Michler, Johann; Bolli, Jean-Luc; Günther, Detlef

    2009-03-01

    Glow Discharge (GD) spectroscopy is a well known and accepted technique for the bulk and surface composition analysis, while laser ablation (LA) provides analysis with high spatial-resolution analysis in LIBS (laser-induced breakdown spectroscopy) or when coupled to inductively coupled plasma spectrometry (ICP-OES or ICP-MS). This work concerns the construction of a Laser Ablation Glow Discharge Time-Of-Flight Mass Spectrometry (LA-GD-TOFMS) instrument to study the analytical capabilities resulting from the interaction of a laser-generated sample plume with a pulsed glow discharge. Two ablation configurations were studied in detail. In a first approach, the laser-generated plume was introduced directly into the GD, while the second approach generated the plume inside the GD. The ablated material was introduced at different times with respect to the discharge pulse in order to exploit the efficient ionization in the GD plasma. For both LA-GD configurations, direct ablation into the afterglow of the pulsed glow discharge leads to an ion signal enhancement of up to a factor of 7, as compared to the ablation process alone under the same experimental conditions. The LA-GD enhancement was found to occur exclusively in the GD afterglow, with a maximum ablation S/N occurring in a few hundred microseconds after the termination of the glow discharge. The duration of the enhanced signal is about two milliseconds. Both the laser pulse energy and the position of the ablation plume (with respect to the sampling orifice) were found to affect the amount of mass entering the afterglow region and consequently, the enhancement factor of ionization.

  6. “Edgeboost”: A Novel Technique to Extend the Ablation Zone Lateral to a Two-Probe Bipolar Radiofrequency Device

    Energy Technology Data Exchange (ETDEWEB)

    Huo, Ya Ruth, E-mail: ruth.huo@gmail.com; Pillai, Krishna, E-mail: panthera6444@yahoo.com.au; Akhter, Javed, E-mail: s8603151@unsw.edu.au; Morris, David L., E-mail: david.morris@unsw.edu.au [St George Hospital, Hepatobiliary and Surgical Oncology Unit, UNSW Department of Surgery (Australia)

    2016-01-15

    BackgroundThe dual-electrode bipolar-RFA (B-RFA) is increasingly used to ablate large liver tumours (3–7 cm). However, the challenging aspect of B-RFA is the placement of the two electrodes around the tumour. Realignment often requires the electrodes to be extracted and reinserted.AimThe aim of this study is to examine “Edgeboost”, a novel technique to increase the lateral ablation dimension without requiring any realignment of the electrodes.Methods and MaterialsAn egg-white model and an ex vivo calf liver model were used compare the standard bipolar mode ablation to Edgeboost-1 (reaching full impedance in bipolar mode initially, then cycling in unipolar mode between left and right probes) and Edgeboost-2 (similar to Edgeboost-1 but not reaching full impedance initially in bipolar mode in order to minimize charring and, thus, to increase total ablation time).ResultsA significantly larger outer lateral ablation dimension to the probe was achieved with Edgeboost-1 compared to the standard method in the liver model (1.14 cm, SD: 0.16 vs. 0.44 cm, SD: 0.24, p = 0.04). Edgeboost-2 achieved the largest outer lateral ablation dimension of 1.75 cm (SD: 0.35). A similar association was seen in the egg model. Edgeboost-2 almost doubled the mass ablated with standard bipolar alone (mass ratio: 1:1.94 in egg white and 1:1.84 in liver).ConclusionThis study demonstrates that the novel “Edgeboost” technique can increase the outer lateral ablation dimension without requiring the two inserted electrodes to be reinserted. This would be beneficial for interventionists who use the dual B-RFA.

  7. Diagnostics of laser ablated plasma plumes

    DEFF Research Database (Denmark)

    Amoruso, S.; Toftmann, B.; Schou, Jørgen;

    2004-01-01

    The effect of an ambient gas on the expansion dynamics of laser ablated plasmas has been studied for two systems by exploiting different diagnostic techniques. First, the dynamics of a MgB2 laser produced plasma plume in an Ar atmosphere has been investigated by space-and time-resolved optical...

  8. Modeling sublimation of a charring ablator

    Science.gov (United States)

    Balhoff, J. F.; Pike, R. W.

    1973-01-01

    The Hertz-Knudsen analysis is shown to accurately predict the sublimation rate from a charring ablator. Porosity is shown to have a significant effect on the surface temperature. The predominant carbon species found in the vapor is C3, which agrees well with the results of previous investigations.

  9. Combining Electrolysis and Electroporation for Tissue Ablation.

    Science.gov (United States)

    Phillips, Mary; Rubinsky, Liel; Meir, Arie; Raju, Narayan; Rubinsky, Boris

    2015-08-01

    Electrolytic ablation is a method that operates by delivering low magnitude direct current to the target region over long periods of time, generating electrolytic products that destroy cells. This study was designed to explore the hypothesis stating that electrolytic ablation can be made more effective when the electrolysis-producing electric charges are delivered using electric pulses with field strength typical in reversible electroporation protocols. (For brevity we will refer to tissue ablation protocols that combine electroporation and electrolysis as E(2).) The mechanistic explanation of this hypothesis is related to the idea that products of electrolysis generated by E(2) protocols can gain access to the interior of the cell through the electroporation permeabilized cell membrane and therefore cause more effective cell death than from the exterior of an intact cell. The goal of this study is to provide a first-order examination of this hypothesis by comparing the charge dosage required to cause a comparable level of damage to a rat liver, in vivo, when using either conventional electrolysis or E(2) approaches. Our results show that E(2) protocols produce tissue damage that is consistent with electrolytic ablation. Furthermore, E(2) protocols cause damage comparable to that produced by conventional electrolytic protocols while delivering orders of magnitude less charge to the target tissue over much shorter periods of time.

  10. Bending diamonds by femtosecond laser ablation

    DEFF Research Database (Denmark)

    Balling, Peter; Esberg, Jakob; Kirsebom, Kim;

    2009-01-01

    We present a new method based on femtosecond laser ablation for the fabrication of statically bent diamond crystals. Using this method, curvature radii of 1 m can easily be achieved, and the curvature obtained is very uniform. Since diamond is extremely tolerant to high radiation doses, partly due...

  11. The Atrial Fibrillation Ablation Pilot Study

    DEFF Research Database (Denmark)

    Arbelo, Elena; Brugada, Josep; Hindricks, Gerhard;

    2014-01-01

    was achieved in 40.7% of patients (43.7% in paroxysmal AF; 30.2% in persistent AF; 36.7% in long-lasting persistent AF). A second ablation was required in 18% of the cases and 43.4% were under antiarrhythmic treatment. Thirty-three patients (2.5%) suffered an adverse event, 272 (21%) experienced a left atrial...

  12. Outpatient laser tonsillar ablation under local anaesthetic.

    Science.gov (United States)

    Andrews, Peter J; Latif, Abdul

    2004-11-01

    Outpatient laser ablation of the palatine tonsils under local anaesthetic is an alternative technique to capsular tonsillectomy for recurrent tonsillitis under general anaesthetic. Laser tonsillotomy ablates up to 70% of the tonsillar tissue and is performed when patients choose not to have a conventional tonsillectomy, or are unfit for a general anaesthetic. The technique described here is an adaptation of Krespis' laser-assisted serial tonsillectomy (LAST) whereby only one sitting is required. Krespis' technique effectively eliminates recurrent tonsillitis in 96% of the cases over a 4-year follow-up period and represents the only substantial study looking at treating recurrent tonsillitis with outpatient laser ablation. This study is a retrospective postal survey of 19 patients who underwent laser tonsillar ablation under local anaesthetic for recurrent chronic tonsillitis from 1997 to 2001 and was performed in liaison with the clinical audit department at Basildon Hospital. We had a response rate of 74% and an admission rate of 0%, which compares favourably with day case tonsillectomy surgery. Of the patients, 75% did not experience further episodes of tonsillitis 12 months after the procedure and 77% of the patients were glad they had the operation. Although this technique does not completely eliminate tonsillitis, it offers an alternative for those patients who prefer a procedure that is done quickly in an outpatient setting without the additional problems of general anaesthesia, overnight hospital admission and long waiting lists.

  13. Barium Ferrite Films Grown by Laser Ablation

    NARCIS (Netherlands)

    Lisfi, A.; Lodder, J.C.; Haan, de P.; Smithers, M.A.; Roesthuis, F.J.G.

    1998-01-01

    Pulsed laser ablation (PLA) has been used to grow barium ferrite films on Al2O3 single crystal substrates. When deposition occurs in an oxidising atmosphere at high temperatures, the films are single BaFe12O19 phase, very well oriented with (001) texture, and exhibit a large perpendicular magnetic a

  14. A chemical model of meteoric ablation

    Directory of Open Access Journals (Sweden)

    T. Vondrak

    2008-07-01

    Full Text Available Most of the extraterrestrial dust entering the Earth's atmosphere ablates to produce metal vapours, which have significant effects on the aeronomy of the upper mesosphere and lower thermosphere. A new Chemical Ablation Model (CAMOD is described which treats the physics and chemistry of ablation, by including the following processes: sputtering by inelastic collisions with air molecules before the meteoroid melts; evaporation of atoms and oxides from the molten particle; diffusion-controlled migration of the volatile constituents (Na and K through the molten particle; and impact ionization of the ablated fragments by hyperthermal collisions with air molecules. Evaporation is based on thermodynamic equilibrium in the molten meteoroid (treated as a melt of metal oxides, and between the particle and surrounding vapour phase. The loss rate of each element is then determined assuming Langmuir evaporation. CAMOD successfully predicts the meteor head echo appearance heights, observed from incoherent scatter radars, over a wide range of meteoroid velocities. The model also confirms that differential ablation explains common-volume lidar observations of K, Ca and Ca+ in fresh meteor trails. CAMOD is then used to calculate the injection rates into the atmosphere of a variety of elements as a function of altitude, integrated over the meteoroid mass and velocity distributions. The most abundant elements (Fe, Mg and Si have peak injection rates around 85 km, with Na and K about 8 km higher. The more refractory element Ca ablates around 82 km with a Na:Ca ratio of 4:1, which does therefore not explain the depletion of atomic Ca to Na, by more than 2 orders of magnitude, in the upper mesosphere. Diffusion of the most volatile elements (Na and K does not appear to be rate-limiting except in the fastest meteoroids. Non-thermal sputtering causes ~35% mass loss from the fastest (~60–70 km s−1 and smallest (10−17–10

  15. A chemical model of meteoric ablation

    Directory of Open Access Journals (Sweden)

    T. Vondrak

    2008-12-01

    Full Text Available Most of the extraterrestrial dust entering the Earth's atmosphere ablates to produce metal vapours, which have significant effects on the aeronomy of the upper mesosphere and lower thermosphere. A new Chemical Ablation Model (CAMOD is described which treats the physics and chemistry of ablation, by including the following processes: sputtering by inelastic collisions with air molecules before the meteoroid melts; evaporation of atoms and oxides from the molten particle; diffusion-controlled migration of the volatile constituents (Na and K through the molten particle; and impact ionization of the ablated fragments by hyperthermal collisions with air molecules. Evaporation is based on thermodynamic equilibrium in the molten meteoroid (treated as a melt of metal oxides, and between the particle and surrounding vapour phase. The loss rate of each element is then determined assuming Langmuir evaporation. CAMOD successfully predicts the meteor head echo appearance heights, observed from incoherent scatter radars, over a wide range of meteoroid velocities. The model also confirms that differential ablation explains common-volume lidar observations of K, Ca and Ca+ in fresh meteor trails. CAMOD is then used to calculate the injection rates into the atmosphere of a variety of elements as a function of altitude, integrated over the meteoroid mass and velocity distributions. The most abundant elements (Fe, Mg and Si have peak injection rates around 85 km, with Na and K about 8 km higher. The more refractory element Ca ablates around 82 km with a Na:Ca ratio of 4:1, which does therefore not explain the depletion of atomic Ca to Na, by more than 2 orders of magnitude, in the upper mesosphere. Diffusion of the most volatile elements (Na and K does not appear to be rate-limiting except in the fastest meteoroids. Non-thermal sputtering causes ~35% mass loss from the fastest (~60–70 km s−1 and smallest (10−17–10

  16. Plume collimation for laser ablation electrospray ionization mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Vertes, Akos; Stolee, Jessica A.

    2016-06-07

    In various embodiments, a device may generally comprise a capillary having a first end and a second end; a laser to emit energy at a sample in the capillary to ablate the sample and generate an ablation plume in the capillary; an electrospray apparatus to generate an electrospray plume to intercept the ablation plume to produce ions; and a mass spectrometer having an ion transfer inlet to capture the ions. The ablation plume may comprise a collimated ablation plume. The device may comprise a flow cytometer. Methods of making and using the same are also described.

  17. Plume collimation for laser ablation electrospray ionization mass spectrometry

    Science.gov (United States)

    Vertes, Akos; Stolee, Jessica A.

    2014-09-09

    In various embodiments, a device may generally comprise a capillary having a first end and a second end; a laser to emit energy at a sample in the capillary to ablate the sample and generate an ablation plume in the capillary; an electrospray apparatus to generate an electrospray plume to intercept the ablation plume to produce ions; and a mass spectrometer having an ion transfer inlet to capture the ions. The ablation plume may comprise a collimated ablation plume. The device may comprise a flow cytometer. Methods of making and using the same are also described.

  18. Burn, freeze, or photo-ablate?: comparative symptom profile in Barrett's dysplasia patients undergoing endoscopic ablation

    Science.gov (United States)

    Gill, Kanwar Rupinder S.; Gross, Seth A.; Greenwald, Bruce D.; Hemminger, Lois L.; Wolfsen, Herbert C.

    2009-06-01

    Background: There are few data available comparing endoscopic ablation methods for Barrett's esophagus with high-grade dysplasia (BE-HGD). Objective: To determine differences in symptoms and complications associated with endoscopic ablation. Design: Prospective observational study. Setting: Two tertiary care centers in USA. Patients: Consecutive patients with BE-HGD Interventions: In this pilot study, symptoms profile data were collected for BE-HGD patients among 3 endoscopic ablation methods: porfimer sodium photodynamic therapy, radiofrequency ablation and low-pressure liquid nitrogen spray cryotherapy. Main Outcome Measurements: Symptom profiles and complications from the procedures were assessed 1-8 weeks after treatment. Results: Ten BE-HGD patients were treated with each ablation modality (30 patients total; 25 men, median age: 69 years (range 53-81). All procedures were performed in the clinic setting and none required subsequent hospitalization. The most common symptoms among all therapies were chest pain, dysphagia and odynophagia. More patients (n=8) in the porfimer sodium photodynamic therapy group reported weight loss compared to radio-frequency ablactation (n=2) and cryotherapy (n=0). Four patients in the porfimer sodium photodynamic therapy group developed phototoxicity requiring medical treatment. Strictures, each requiring a single dilation, were found in radiofrequency ablactation (n=1) and porfimer sodium photodynamic therapy (n=2) patients. Limitations: Small sample size, non-randomized study. Conclusions: These three endoscopic therapies are associated with different types and severity of post-ablation symptoms and complications.

  19. Electrolytic Effects During Tissue Ablation by Electroporation.

    Science.gov (United States)

    Rubinsky, Liel; Guenther, Enric; Mikus, Paul; Stehling, Michael; Rubinsky, Boris

    2016-10-01

    Nonthermal irreversible electroporation is a new tissue ablation technique that consists of applying pulsed electric fields across cells to induce cell death by creating permanent defects in the cell membrane. Nonthermal irreversible electroporation is of interest because it allows treatment near sensitive tissue structures such as blood vessels and nerves. Two recent articles report that electrolytic reaction products at electrodes can be combined with electroporation pulses to augment and optimize tissue ablation. Those articles triggered a concern that the results of earlier studies on nonthermal irreversible electroporation may have been tainted by unaccounted for electrolytic effects. The goal of this study was to reexamine previous studies on nonthermal irreversible electroporation in the context of these articles. The study shows that the results from some of the earlier studies on nonthermal irreversible electroporation were affected by unaccounted for electrolysis, in particular the research with cells in cuvettes. It also shows that tissue ablation ascribed in the past to irreversible electroporation is actually caused by at least 3 different cytotoxic effects: irreversible electroporation without electrolysis, irreversible electroporation combined with electrolysis, and reversible electroporation combined with electrolysis. These different mechanisms may affect cell and tissue ablation in different ways, and the effects may depend on various clinical parameters such as the polarity of the electrodes, the charge delivered (voltage, number, and length of pulses), and the distance of the target tissue from the electrodes. Current clinical protocols employ ever-increasing numbers of electroporation pulses to values that are now an order of magnitude larger than those used in our first fundamental nonthermal irreversible electroporation studies in tissues. The different mechanisms of cell death, and the effect of the clinical parameters on the mechanisms may

  20. Silicon-Class Ablators for NIC Ignition Capsules

    Science.gov (United States)

    Ho, Darwin; Salmonson, Jay; Haan, Steve

    2012-10-01

    We present design studies using silicon-class ablators (i.e., Si, SiC, SiB6, and SiB14) for NIC ignition capsules. These types of ablators have several advantages in that they: (a) require no internal dopant layers and are robust to M-band radiation; (b) have smooth outer surfaces; (c) have stable fuel-ablator interface; and (d) have good 1-D performance. The major disadvantage for some of the ablators in this class is the relatively smaller ablation stabilization. Consequently, the ablator is more susceptible to breakup caused by RT instabilities. However, smoother outer surfaces on this class of ablators can reduce the effect of RT instabilities. 2-D simulations of SiC ablators show ignition failure despite smooth surfaces and good 1-D performance. But SiB6 and SiB14 ablators exhibit promising behaviors. SiB6 (SiB14) ablators have high 1-D ignition margin and high peak core hydrodynamic pressure 880 (900) Gbar. The ablation scale length for SiB6 is longer than that for SiC and for SiB14 is comparable to that of plastic. Therefore, we expect acceptable performance for SiB6 and less RT growth for SiB14. 2-D simulations are now in progress.

  1. Cork-resin ablative insulation for complex surfaces and method for applying the same

    Science.gov (United States)

    Walker, H. M.; Sharpe, M. H.; Simpson, W. G. (Inventor)

    1980-01-01

    A method of applying cork-resin ablative insulation material to complex curved surfaces is disclosed. The material is prepared by mixing finely divided cork with a B-stage curable thermosetting resin, forming the resulting mixture into a block, B-stage curing the resin-containing block, and slicing the block into sheets. The B-stage cured sheet is shaped to conform to the surface being insulated, and further curing is then performed. Curing of the resins only to B-stage before shaping enables application of sheet material to complex curved surfaces and avoids limitations and disadvantages presented in handling of fully cured sheet material.

  2. Tissue temperatures and lesion size during irrigated tip catheter radiofrequency ablation: an in vitro comparison of temperature-controlled irrigated tip ablation, power-controlled irrigated tip ablation, and standard temperature-controlled ablation

    DEFF Research Database (Denmark)

    Petersen, H H; Chen, X; Pietersen, A;

    2000-01-01

    in the power-controlled mode with high power and high infusion rate, and is associated with an increased risk of crater formation, which is related to high tissue temperatures. The present study explored the tissue temperatures during temperature-controlled irrigated tip ablation, comparing it with standard......The limited success rate of radiofrequency catheter ablation in patients with ventricular tachycardias related to structural heart disease may be increased by enlarging the lesion size. Irrigated tip catheter ablation is a new method for enlarging the size of the lesion. It was introduced...... temperature-controlled ablation and power-controlled irrigated tip ablation. In vitro strips of porcine left ventricular myocardium were ablated. Temperature-controlled irrigated tip ablation at target temperatures 60 degrees C, 70 degrees C, and 80 degrees C with infusion of 1 mL saline/min were compared...

  3. Wavelength dependence of soft tissue ablation by using pulsed lasers

    Institute of Scientific and Technical Information of China (English)

    Xianzeng Zhang; Shusen Xie; Qing Ye; Zhenlin Zhan

    2007-01-01

    Pulsed laser ablation of soft biological tissue was studied at 10.6-, 2.94-, and 2.08-μm wavelengths. The ablation effects were assessed by means of optical microscope, the ablation crater depths were measured with reading microscope. It was shown that Er:YAG laser produced the highest quality ablation with clear,sharp cuts following closely the patial contour of the incident beam and the lowest fluence threshold. The pulsed CO2 laser presented the moderate quality ablation with the highest ablation efficiency. The craters drilled with Ho:YAG laser were generally larger than the incident laser beam spot, irregular in shape, and clearly dependent on the local morphology of biotissue. The blation characteristics, including fluence threshold and ablation efficiency, varied substantially with wavelength. It is not evident that water is the only dominant chromophore in tissue.

  4. Investigation of Resin Systems for Improved Ablative Materials

    Science.gov (United States)

    1966-04-01

    67 C-I Equilibrium Decomposition Products Molar Composition for a B-N Type Resin with Empirical Formula C 6 H 1 5 B 2 N 3...82 C-II Equilibrium Decomposition Products Molar Composition for a Si-O Type Resin with Empirical Formula C8 HjoSiO 2 85 -xiii - NASA CR-54471 4176...6014-SOOO TABLES (Continued) Page C-Ill Equilibrium Decomposition Products Molar Composition for a Si-O Type Resin with Empirical Formula of CI 2 Hl

  5. Investigation of Resin Systems for Improved Ablative Materials

    Science.gov (United States)

    2010-02-25

    and synthe- sized in Task I. " Commercial Sources: Monsanto - Skybond 700 (polyimide), and Narmco - Polybenzimidazole. Optimization of the resins will...tested in Contract NAS3-4188 (DuPont SP-I and SP-2), a new polyimide resin produced by Monsanto (Skybond 700) has recently been added to those resins...laminates from the improved modified polyimides being synthesized in Task I. The new resin selected for evaluation was Monsanto Chemical Company’s Skybond 700

  6. The Post-Test Analysis of Ablative Materials

    Science.gov (United States)

    1969-02-10

    Alpha - iron , amorphous silica and carbon, and poorly crystalline carbon were observed. 04, 06, 10 1.66, 1.60, 1.50 Alpha - iron , amorphous silica and carbon...significant difference in degree of crystallinity of graphite. Minor amounts of alpha - iron . 14, 16, 20 1.33, 1.28, 1.18 Graphite and amorphous carbon...specific heat with depth. It is possible that the slight traces of alpha iron which were observed during the X-ray profile studies of the nozzle

  7. Impacts of Ambient and Ablation Plasmas on Short- and Ultrashort-Pulse Laser Processing of Surfaces

    Directory of Open Access Journals (Sweden)

    Nadezhda M. Bulgakova

    2014-12-01

    Full Text Available In spite of the fact that more than five decades have passed since the invention of laser, some topics of laser-matter interaction still remain incompletely studied. One of such topics is plasma impact on the overall phenomenon of the interaction and its particular features, including influence of the laser-excited plasma re-radiation, back flux of energetic plasma species, and massive material redeposition, on the surface quality and processing efficiency. In this paper, we analyze different plasma aspects, which go beyond a simple consideration of the well-known effect of plasma shielding of laser radiation. The following effects are considered: ambient gas ionization above the target on material processing with formation of a “plasma pipe”; back heating of the target by both laser-driven ambient and ablation plasmas through conductive and radiative heat transfer; plasma chemical effects on surface processing including microstructure growth on liquid metals; complicated dynamics of the ablation plasma flow interacting with an ambient gas that can result in substantial redeposition of material around the ablation spot. Together with a review summarizing our main to-date achievements and outlining research directions, we present new results underlining importance of laser plasma dynamics and photoionization of the gas environment upon laser processing of materials.

  8. ns or fs pulsed laser ablation of a bulk InSb target in liquids for nanoparticles synthesis.

    Science.gov (United States)

    Semaltianos, N G; Hendry, E; Chang, H; Wears, M L; Monteil, G; Assoul, M; Malkhasyan, V; Blondeau-Patissier, V; Gauthier-Manuel, B; Moutarlier, V

    2016-05-01

    Laser ablation of bulk target materials in liquids has been established as an alternative method for the synthesis of nanoparticles colloidal solutions mainly due to the fact that the synthesized nanoparticles have bare, ligand-free surfaces since no chemical precursors are used for their synthesis. InSb is a narrow band gap semiconductor which has the highest carrier mobility of any known semiconductor and nanoparticles of this material are useful in optoelectronic device fabrication. In this paper a bulk InSb target was ablated in deionized (DI) water or ethanol using a nanosecond (20 ns) or a femtosecond (90 fs) pulsed laser source, for nanoparticles synthesis. In all four cases the largest percentage of the nanoparticles are of InSb in the zincblende crystal structure with fcc lattice. Oxides of either In or Sb are also formed in the nanoparticles ensembles in the case of ns or fs ablation, respectively. Formation of an oxide of either element from the two elements of the binary bulk alloy is explained based on the difference in the ablation mechanism of the material in the case of ns or fs pulsed laser irradiation in which the slow or fast deposition of energy into the material results to mainly melting or vaporization, respectively under the present conditions of ablation, in combination with the lower melting point but higher vaporization enthalpy of In as compared to Sb. InSb in the metastable phase with orthorhombic lattice is also formed in the nanoparticles ensembles in the case of fs ablation in DI water (as well as oxide of InSb) which indicates that the synthesized nanoparticles exhibit polymorphism controlled by the type of the laser source used for their synthesis. The nanoparticles exhibit absorption which is observed to be extended in the infrared region of the spectrum.

  9. Cavitation dynamics of laser ablation of bulk and wire-shaped metals in water during nanoparticles production.

    Science.gov (United States)

    De Giacomo, A; Dell'Aglio, M; Santagata, A; Gaudiuso, R; De Pascale, O; Wagener, P; Messina, G C; Compagnini, G; Barcikowski, S

    2013-03-07

    Although the first nanoseconds to microseconds rule the resulting process yield of laser ablation in liquid, a comprehensive view involving combination of time-resolved measurement techniques is still lacking. In this paper, fundamental aspects of laser ablation of metals in water during the production of nanoparticles are discussed. Three fast diagnostic methods have been applied simultaneously. These are Optical Emission Spectroscopy for the plasma characterization, fast shadowgraph for plasma and cavitation bubble dynamics and laser scattering for the mechanisms of delivery of the produced materials in the liquid. Moreover, in order to validate the discussion, the effect on cavitation dynamics of the ablation of bulk and wire-shaped targets has been investigated together with the relative nanoparticles production yield. Unusual arrow-bow ejection phenomena between the cavitation bubble and the wire result in suppressed material back-deposition, causing efficient ejection of ablated matter into the liquid. The presented nanosecond and microsecond-resolved analysis allows estimating the timescale and role of the basic mechanisms involved in laser ablation in liquids as well as the thermodynamic characteristics of the processes.

  10. Measurements of nanoparticle size distribution produced by laser ablation of tungsten and boron-carbide in N 2 ambient

    Science.gov (United States)

    Bereznai, Miklós; Heszler, Péter; Tóth, Zsolt; Wilhelmsson, Ola; Boman, Mats

    2006-04-01

    Nanoparticles (NPs) were produced by ablating tungsten and boron-carbide (B 4C) target materials in atmospheric pressure nitrogen ambient using ArF excimer laser pulses. The size distributions of the NPs formed during the ablation were monitored—within a 7-133 nm size window—by a condensation particle counter connected to a differential mobility analyzer. The laser repetition rate was varied between 1-50 Hz, and the fluence was systematically changed in the range of 0.5-15 J/cm 2, for both materials, allowing a comparative study in an extended laser parameter regime. The multishot ablation threshold ( Φth) of B 4C was determined to be ˜1.9 J/cm 2 for the laser used (ArF excimer, λ = 193 nm). Similarly to earlier studies, it was shown that the size distributions consist of mainly small nanoparticles (<˜20 nm) attributed to a non-thermal ablation mechanism below Φth. An additional broad peak appears (between 20 and 40 nm) above Φth as a consequence of the thermally induced macroscopic ablation. Chemical composition of deposited polydisperse nanoparticles was studied by X-ray photoelectron spectroscopy showing nitrogen incorporation into the boron-carbide.

  11. Laser ablation and growth of Si and Ge

    Energy Technology Data Exchange (ETDEWEB)

    Yap, Seong Shan, E-mail: seong.yap@ntnu.no [Department of Physics, Norwegian University of Science and Technology, 7491 Trondheim (Norway); Siew, Wee Ong; Nee, Chen Hon [Faculty of Engineering, Multimedia University, 63100 Cyberjaya, Selangor (Malaysia); Reenaas, Turid Worren [Department of Physics, Norwegian University of Science and Technology, 7491 Trondheim (Norway); Tou, Teck Yong [Faculty of Engineering, Multimedia University, 63100 Cyberjaya, Selangor (Malaysia)

    2012-02-01

    In this work, we investigated the laser ablation and deposition of Si and Ge at room temperature in vacuum by employing nanosecond lasers of 248 nm, 355 nm, 532 nm and 1064 nm. Time-integrated optical emission spectra were obtained for neutrals and ionized Ge and Si species in the plasma at laser fluences from 0.5 to 11 J/cm{sup 2}. The deposited films were characterized by using Raman spectroscopy, scanning electron microscopy and atomic force microscopy. Amorphous Si and Ge films, micron-sized crystalline droplets and nano-sized particles were deposited. The results suggested that ionized species in the plasma promote the process of subsurface implantation for both Si and Ge films while large droplets were produced from the superheated and melted layer of the target. The dependence of the properties of the materials on laser wavelength and fluence were discussed.

  12. Strain compatibility assessment for SRB sprayable ablator MSA-1

    Science.gov (United States)

    Patterson, W. J.

    1979-01-01

    Tensile and compressive strain compatibility testing was performed on as-sprayed samples of the Shuttle Solid Rocket Booster external ablator material, MSA-1. Strain gages on the aluminum substrate were used to monitor strain. Strain compatibility was determined as the percent strain in the substrate at first visual evidence of MSA-1 failure. The 1/8-in. MSA-1, baselined for large areas of the SRB external skin, was characterized by a strain compatibility of 1.5 to 1.8 percent, which far exceeded the yield range of the metal substrate. Thicker MSA-1 applications (1.4 to 3/8 in.) were characterized by a lower level of strain compatibility, which appeared to be a manifestation of application limitations.

  13. Does Radio Frequency Ablation (RFA) Epiphysiodesis Affect Joint Cartilage?

    DEFF Research Database (Denmark)

    Shiguetomi Medina, Juan Manuel; Abood, Ahmed Abdul-Hussein; Rahbek, Ole;

    Background: Epiphysiodesis made with RFA has resulted, in animal models, an effective procedure that disrupts the growth plate and induces LLD. This procedure involves an increase of temperature (>92°C) of the targeted region causing thermal damage. To our knowledge, no study that investigates...... the effect of this procedure in the adjacent joint articular cartilage has been reported Purpose / Aim of Study: Proof of concept that epiphysiodesis made with RFA is a safe procedure that disrupts the growth plate without damaging the adjacent joint articular cartilage Materials and Methods: RFA...... articular joint cartilage. This study resembles possible results of RFA epiphysiodesis on humans. Previous studies suggest that an 8 min ablation is enough to disrupt the growth plate. This study shows that RFA can be done safely in the growing physis even on triple-long procedures. It is important...

  14. Laser-induced back-ablation of aluminum thin films using picosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    BULLOCK, A B

    1999-05-26

    Experiments were performed to understand laser-induced back-ablation of Al film targets with picosecond laser pulses. Al films deposited on the back surface of BK-7 substrates are ablated by picosecond laser pulses propagating into the Al film through the substrate. The ablated Al plume is transversely probed by a time-delayed, two-color sub-picoseond (500 fs) pulse, and this probe is then used to produce self-referencing interferograms and shadowgraphs of the Al plume in flight. Optical emission from the Al target due to LIBA is directed into a time-integrated grating spectrometer, and a time-integrating CCD camera records images of the Al plume emission. Ablated Al plumes are also redeposited on to receiving substrates. A post-experimental study of the Al target and recollected deposit characteristics was also done using optical microscopy, interferometry, and profilometry. In this high laser intensity regime, laser-induced substrate ionization and damage strongly limits transmitted laser fluence through the substrate above a threshold fluence. The threshold fluence for this ionization-based transmission limit in the substrate is dependent on the duration of the incident pulse. The substrate ionization can be used as a dynamic control of both transmitted spatial pulse profile and ablated Al plume shape. The efficiency of laser energy transfer between the laser pulse incident on the Al film and the ablated Al plume is estimated to be of order 5% and is a weak function of laser pulsewidth. The Al plume is highly directed. Low plume divergence ({theta}{sub divergence} < 5{sup o}) shows the ablated plume temperature to be very low at long time delays ( T << 0.5 eV at delays of 255 ns). Spectroscopic observations and calculations indicate that, in early time (t < 100 ps), the Al film region near the substrate/metal interface is at temperatures of order 0.5 eV. Interferograms of Al plumes produced with 0.1 {micro}m films show these plumes to be of high neutral atom

  15. Silver nanoparticles generated by pulsed laser ablation in supercritical CO2 medium

    Science.gov (United States)

    Machmudah, Siti; Sato, Takayuki; Wahyudiono; Sasaki, Mitsuru; Goto, Motonobu

    2012-03-01

    Pulsed laser ablation (PLA) has been widely employed in industrial and biological applications and in other fields. The environmental conditions in which PLA is conducted are important parameters that affect both the solid particle cloud and the deposition produced by the plume. In this work, the generation of nanoparticles (NPs) has been developed by performing PLA of silver (Ag) plates in a supercritical CO2 medium. Ag NPs were successfully generated by allowing the selective generation of clusters. Laser ablation was performed with an excitation wavelength of 532 nm under various pressures and temperatures of CO2 medium. On the basis of the experimental result, both surface of the irradiated Ag plate and structure of Ag NPs were significantly affected by the changes in supercritical CO2 pressure and temperature. With increasing irradiation pressure, plume deposited in the surrounding crater created by the ablation was clearly observed. In Field Emission Scanning Electron Microscopy (FE-SEM) the image of the generated Ag NPs on the silicon wafer and the morphology of Ag particles were basically a sphere-like structure. Ag particles contain NPs with large-varied diameter ranging from 5 nm to 1.2 μm. The bigger Ag NPs melted during the ablation process and then ejected smaller spherical Ag NPs, which formed nanoclusters attached on the molten Ag NPs. The smaller Ag NPs were also formed around the bigger Ag NPs. Based on the results, this new method can also be used to obtain advanced nano-structured materials.

  16. Towards nanopatterning by femtosecond laser ablation of pre-stretched elastomers

    Science.gov (United States)

    Surdo, Salvatore; Piazza, Simonluca; Ceseracciu, Luca; Diaspro, Alberto; Duocastella, Martí

    2016-06-01

    Diffraction limits the focusing capabilities of an optical system seriously constraining the use of lasers for nanopatterning. In this work, we present a novel and simple approach to reduce the minimum feature size of a laser-direct write system by ablating a pre-stretched material. In particular, by focusing and scanning a femtosecond laser beam on the surface of a uniaxially pre-stretched elastomeric membrane we are able to obtain microstructures according to a desired pattern. After removing the stress applied to the elastomer, the membrane relaxes to its original size and the ablated patterns shrink while preserving their shape. In this way, the minimum feature size that is typically determined by the optical properties of the focusing system can be now controlled by the strain applied to the elastomer during the ablation process. We demonstrate this approach by ablating lines on a stretchable polymeric membrane at different strain conditions. Experimental results are in good agreement with theoretical predictions. The proposed method opens up new interesting possibilities for the rapid prototyping of micro- and nano-structures suitable for a wide range of applications such as soft-lithography, micro-/nano-fluidics and lab-on-chip.

  17. The changes in complete blood count in thyroid cancer patients treated with radioactive iodine ablation therapy

    Directory of Open Access Journals (Sweden)

    Bircan Sönmez

    2010-12-01

    Full Text Available Objective: The aim of this study was to evaluate the effect of radioactive iodine (RAI ablation therapy on the complete blood count (CBC in thyroid cancer patients. Materials and Methods: One hundred sixty four patients undergoing RAI ablation therapy after total thyroidectomy were included. CBC results were available from the patients’ medical records at the time of ablation and at the 1st, 6th, and 12th months after RAI therapy.Results: Hemoglobin (Hb, white blood cell (WBC and platelet (Plt values were significantly lower than baseline at 1 month after treatment (p<0.0001. Hb and WBC values were increased at the 6th month and at the 1st year. Plt values increased at the 6th month but had decreased again at the 1st year. The values were usually in normal ranges except in the patients with low pretreatment Hb and WBC values.Conclusion: RAI ablation therapy in thyroid cancer patients is a safe treatment modality without any serious or persistent hematological side effects.

  18. Characterization of laser-induced damage in silicon solar cells during selective ablation processes

    Energy Technology Data Exchange (ETDEWEB)

    Poulain, G. [Université de Lyon, Institut des Nanotechnologies de Lyon INL-UMR5270, CNRS, INSA de Lyon, Bâtiment Blaise pascal, Villeurbanne, F-69621 (France); Agence de l’environnement et de la Maîtrise de l’Energie, 20, avenue du Grésillé, BP 90406 49004 Angers Cedex 01 (France); Blanc, D., E-mail: daniele.blanc@insa-lyon.fr [Université de Lyon, Institut des Nanotechnologies de Lyon INL-UMR5270, CNRS, INSA de Lyon, Bâtiment Blaise pascal, Villeurbanne, F-69621 (France); Focsa, A.; De Vita, M.; Fraser, K. [Université de Lyon, Institut des Nanotechnologies de Lyon INL-UMR5270, CNRS, INSA de Lyon, Bâtiment Blaise pascal, Villeurbanne, F-69621 (France); Sayad, Y. [Institut de Sciences et Technologies, Centre Universitaire de Souk Ahras, Route de Annaba, Souk Ahras (Algeria); Lemiti, M. [Université de Lyon, Institut des Nanotechnologies de Lyon INL-UMR5270, CNRS, INSA de Lyon, Bâtiment Blaise pascal, Villeurbanne, F-69621 (France)

    2013-05-15

    Selective laser ablation of silicon nitride layers on crystalline silicon wafers was investigated for solar cell fabrication. Laser processing was performed with a nanosecond UV laser at various energy densities ranging from 0.2 to 1.5 J cm{sup −2}. Optical microscopy was used as a simple mean to assess the ablation threshold that was correlated to the temperature at the interface between the silicon nitride coating and the silicon substrate. Minority carrier lifetime measurements were performed using a microwave photo-conductance decay technique. Band to band photoluminescence spectroscopy proved to be a sensitive technique to qualify the laser-induced damage to the silicon substrate. The crystalline structure of silicon seemed to be maintained after silicon nitride ablation as shown by UV reflectivity measurements. Laser parameters corresponding to fluences of around 0.4 J cm{sup −2} were found to achieve selective ablation of SiN{sub x} without causing detrimental damage to the surrounding material.

  19. Preparation of silver nanoparticles in virgin coconut oil using laser ablation

    Directory of Open Access Journals (Sweden)

    Reza Zamiri,B Z Azmi. Amir Reza Sadrolhosseini

    2011-01-01

    Full Text Available Reza Zamiri1, B Z Azmi1,2, Amir Reza Sadrolhosseini1, Hossein Abbastabar Ahangar3, A W Zaidan1, M A Mahdi41Department of Physics, 2Advanced Materials and Nanotechnology Laboratory, 3Department of Chemistry, 4Wireless and Photonics Networks Research Center, Universiti Putra Malaysia, Serdang, Selangor, MalaysiaAbstract: Laser ablation of a silver plate immersed in virgin coconut oil was carried out for fabrication of silver nanoparticles. A Nd:YAG laser at wavelengths of 1064 nm was used for ablation of the plate at different times. The virgin coconut oil allowed formation of nanoparticles with well-dispersed, uniform particle diameters that were stable for a reasonable length of time. The particle sizes and volume fraction of nanoparticles inside the solutions obtained at 15, 30, 45 min ablation times were 4.84, 5.18, 6.33 nm and 1.0 × 10-8, 1.6 × 10-8, 2.4 × 10-8, respectively. The presented method for preparation of silver nanoparticles in virgin coconut oil is environmentally friendly and may be considered a green method.Keywords: silver nanoparticles, laser ablation, virgin coconut oil

  20. Three-Dimensional Single-Mode Nonlinear Ablative Rayleigh-Taylor Instability

    Science.gov (United States)

    Yan, R.; Betti, R.; Sanz, J.; Liu, B.; Frank, A.

    2015-11-01

    The nonlinear evolution of the ablative Rayleigh-Taylor (ART) instability is studied in three dimensions for conditions relevant to inertial confinement fusion targets. The simulations are performed using our newly developed code ART3D and an astrophysical code AstroBEAR. The laser ablation can suppress the growth of the short-wavelength modes in the linear phase but may enhance their growth in the nonlinear phase because of the vortex-acceleration mechanism. As the mode wavelength approaches the cutoff of the linear spectrum (short-wavelength modes), it is found that the bubble velocity grows faster than predicted in the classical 3-D theory. When compared to 2-D results, 3-D short-wavelength bubbles grow faster and do not reach saturation. The unbounded 3-D bubble acceleration is driven by the unbounded accumulation of vorticity inside the bubble. The vorticity is transferred by mass ablation from the Rayleigh-Taylor spikes into the ablated plasma filling the bubble volume. A density plateau is observed inside a nonlinear ART bubble and the plateau density is higher for shorter-wavelength modes. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  1. High-density carbon ablator experiments on the National Ignition Facilitya)

    Energy Technology Data Exchange (ETDEWEB)

    MacKinnon, A. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Meezan, N. B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Ross, J. S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Le Pape, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Berzak Hopkins, L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Divol, L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Ho, D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Milovich, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Pak, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Ralph, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Döppner, T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Patel, P. K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Thomas, C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Tommasini, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Haan, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); MacPhee, A. G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); McNaney, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Caggiano, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hatarik, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Bionta, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Ma, T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Spears, B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Rygg, J. R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Benedetti, L. R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Town, R. P. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Bradley, D. K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Dewald, E. L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Fittinghoff, D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Jones, O. S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Robey, H. R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Moody, J. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Khan, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Callahan, D. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hamza, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Biener, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Celliers, P. M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Braun, D. G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Erskine, D. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Prisbrey, S. T. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Wallace, R. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Kozioziemski, B. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Dylla-Spears, R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Sater, J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Collins, G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Storm, E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hsing, W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Landen, O. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Atherton, J. L. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Lindl, J. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Edwards, M. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Frenje, J. A. [MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States); Gatu-Johnson, M. [MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States); Li, C. K. [MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States); Petrasso, R. [MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States); Rinderknecht, H. [MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States); Rosenberg, M. [MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States); Séguin, F. H. [MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States); Zylstra, A. [MIT (Massachusetts Inst. of Technology), Cambridge, MA (United States); Knauer, J. P. [Univ. of Rochester, NY (United States); Grim, G. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Guler, N. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Merrill, F. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Olson, R. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kyrala, G. A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kilkenny, J. D. [General Atomics, San Diego, CA (United States); Nikroo, A. [General Atomics, San Diego, CA (United States); Moreno, K. [General Atomics, San Diego, CA (United States); Hoover, D. E. [General Atomics, San Diego, CA (United States); Wild, C. [Diamond Materials GmbH, Freiburg (Germany); Werner, E. [Diamond Materials GmbH, Freiburg (Germany)

    2014-05-01

    High Density Carbon (HDC) is a leading candidate as an ablator material for Inertial Confinement Fusion (ICF) capsules in x-ray (indirect) drive implosions. HDC has a higher density (3.5 g/cc) than plastic (CH, 1 g/cc), which results in a thinner ablator with a larger inner radius for a given capsule scale. This leads to higher x-ray absorption and shorter laser pulses compared to equivalent CH designs. This paper will describe a series of experiments carried out to examine the feasibility of using HDC as an ablator using both gas filled hohlraums and lower density, near vacuum hohlraums. These experiments have shown that deuterium (DD) and deuterium-tritium gas filled HDC capsules driven by a hohlraum filled with 1.2 mg/cc He gas, produce neutron yields a factor of 2× higher than equivalent CH implosions, representing better than 50% Yield-over-Clean (YoC). In a near vacuum hohlraum (He = 0.03 mg/cc) with 98% laser-to-hohlraum coupling, such a DD gas-filled capsule performed near 1D expectations. A cryogenic layered implosion version was consistent with a fuel velocity = 410 ± 20 km/s with no observed ablator mixing into the hot spot.

  2. Controlled Contamination of Epoxy Composites with PDMS and Removal by Laser Ablation

    Science.gov (United States)

    Palmieri, Frank; Ledesma, Rodolfo; Cataldo, Daniel; Lin, Yi; Wohl, Christopher; Gupta, Mool; Connell, John

    2016-01-01

    Surface preparation is critical to the performance of adhesively bonded composites. During manufacturing, minute quantities of mold release compounds are inevitably deposited on faying surfaces and may compromise bond performance. To ensure safety, mechanical fasteners and other crack arrest features must be installed in the bondlines of primary structures, which negates some advantages of adhesively bonded construction. Laser ablation is an automated, repeatable, and scalable process with high potential for the surface preparation of metals and composites in critical applications such as primary airframe structures. In this study, laser ablation is evaluated on composite surfaces for the removal of polydimethylsiloxane (PDMS), a common mold release material. Composite panels were contaminated uniformly with PDMS film thicknesses as low as 6.0 nm as measured by variable angle spectroscopic ellipsometry. Bond performance was assessed by mechanical testing using a 250 F cure, epoxy adhesive and compared with pre-bond surface inspection results. Water contact angle, optically stimulated electron emission, and laser induced breakdown spectroscopy were used to characterize contaminated and laser ablated surfaces. The failure mode obtained from double cantilever beam tests correlated well with surface characterization data. The test results indicated that even low levels of PDMS were not completely removed by laser ablation.

  3. 3D transient model to predict temperature and ablated areas during laser processing of metallic surfaces

    Science.gov (United States)

    Naghshine, Babak. B.; Kiani, Amirkianoosh

    2017-02-01

    Laser processing is one of the most popular small-scale patterning methods and has many applications in semiconductor device fabrication and biomedical engineering. Numerical modelling of this process can be used for better understanding of the process, optimization, and predicting the quality of the final product. An accurate 3D model is presented here for short laser pulses that can predict the ablation depth and temperature distribution on any section of the material in a minimal amount of time. In this transient model, variations of thermal properties, plasma shielding, and phase change are considered. Ablation depth was measured using a 3D optical profiler. Calculated depths are in good agreement with measured values on laser treated titanium surfaces. The proposed model can be applied to a wide range of materials and laser systems.

  4. Crack Arrest in Brittle Ceramics Subjected to Thermal Shock and Ablation

    Science.gov (United States)

    Wang, Yan-Wei; Yu, He-Long; Tang, Hong-Xiang; Feng, Xue

    2014-09-01

    Ceramics are suitable for high temperature applications, especially for aerospace materials. When serving in high temperature environments, ceramics usually have to deal with the challenge of both thermal shock and ablation. We report the crack arrest in brittle ceramics during thermal shock and ablation. In our experiment, the specimens of Al2O3 are subjected to oxygen-propane flame heating until the temperature arises up to 1046°C and then are cooled down in air. The crack occurs, however, it does not propagate when arrested by the microstructures (e.g., micro-bridges) of the crack tip. Such micro-bridge enhances the toughness of the brittle ceramics and prevents the crack propagation, which provides a hint for design of materials against the thermal shock.

  5. Percutaneous thermal ablation of renal neoplasms; Perkutane Thermoablation von Nierentumoren

    Energy Technology Data Exchange (ETDEWEB)

    Tacke, J. [Inst. fuer Diagnostische und Interventionelle Radiologie/Neuroradiologie, Klinikum Passau (Germany); Mahnken, A.H.; Guenther, R.W. [Klinik fuer Radiologische Diagnostik, Universitaetsklinikum Aachen (Germany)

    2005-12-15

    Due to modern examination techniques such as multidetector computed tomography and high-field magnetic resonance imaging, the detection rate of renal neoplasms is continually increasing. Even though tumors exceeding 4 cm in diameter rarely metastasize, all renal lesions that are possible neoplasms should be treated. Traditional treatment techniques include radical nephrectomy or nephron-sparing resection, which are increasingly performed laparoscopically. Modern thermal ablation techniques such as hyperthermal techniques like radiofrequency ablation RFA, laser induced thermal ablation LITT, focused ultrasound FUS and microwave therapy MW, as well as hypothermal techniques (cryotherapy) may be a useful treatment option for patients who are unfit for or refuse surgical resection. Cryotherapy is the oldest and best known thermal ablation technique and can be performed laparoscopically or percutaneously. Since subzero temperatures have no antistyptic effect, additional maneuvers must be performed to control bleeding. Percutaneous cryotherapy of renal tumors is a new and interesting method, but experience with it is still limited. Radiofrequency ablation is the most frequently used method. Modern probe design allows volumes between 2 and 5 cm in diameter to be ablated. Due to hyperthermal tract ablation, the procedure is deemed to be safe and has a low complication rate. Although there are no randomized comparative studies to open resection, the preliminary results for renal RFA are promising and show RFA to be superior to other thermal ablation techniques. Clinical success rates are over 90% for both, cryo- and radiofrequency ablation. Whereas laser induced thermal therapy is established in hepatic ablation, experience is minimal with respect to renal application. For lesions of more than 2 cm in diameter, additional cooling catheters are required. MR thermometry offers temperature control during ablation. Microwave ablation is characterized by small ablation volumes

  6. Improved optical limiting performance of laser-ablation-generated metal nanoparticles due to silica-microsphere-induced local field enhancement

    OpenAIRE

    Zheren Du; Lianwei Chen; Tsung-Sheng Kao; Mengxue Wu; Minghui Hong

    2015-01-01

    For practical application, optical limiting materials must exhibit a fast response and a low threshold in order to be used for the protection of the human eye and electro-optical sensors against intense light. Many nanomaterials have been found to exhibit optical limiting properties. Laser ablation offers the possibility of fabricating nanoparticles from a wide range of target materials. For practical use of these materials, their optical limiting performance, including optical limiting thres...

  7. [Atrial fibrillation ablation: application of nurse methodology].

    Science.gov (United States)

    Ramos-González-Serna, Amelia; Mateos-García, M Dolores

    2011-01-01

    Ablation of pulmonary veins for treatment of atrial fibrillation involves applying radiofrequency energy wave by a catheter that causes a circumferential lesion to achieve electrical isolation and voltage drop in the interior. It is mainly applied when there is resistance to treatment and recurrence of symptoms affecting the quality of life of patients. The nurse is an important part of the multidisciplinary team who care for patients who undergo this procedure. The provision of comprehensive nursing care should include nursing procedures prior to, during, and after treatment to ensure the careful and systematic quality required. The aims of this article are: to provide specialised knowledge on the procedure of atrial fibrillation ablation, to describe the preparation of the electrophysiology laboratory, analyse nursing care and develop a standardized care plan for patients on whom this procedure is performed using the NANDA (North American Nursing Association) taxonomy and NIC (Nursing Intervention Classification).

  8. Design calculations for NIF convergent ablator experiments

    Directory of Open Access Journals (Sweden)

    Olson R.E.

    2013-11-01

    Full Text Available The NIF convergent ablation tuning effort is underway. In the early experiments, we have discovered that the design code simulations over-predict the capsule implosion velocity and shock flash ρr, but under-predict the hohlraum x-ray flux measurements. The apparent inconsistency between the x-ray flux and radiography data implies that there are important unexplained aspects of the hohlraum and/or capsule behavior.

  9. Radiofrequency ablation of two femoral head chondroblastomas

    Energy Technology Data Exchange (ETDEWEB)

    Petsas, Theodore [Department of Radiology, University of Patras (Greece); Megas, Panagiotis [Department of Orthopaedic Surgery, University of Patras (Greece)]. E-mail: panmegas@med.upatras.gr; Papathanassiou, Zafiria [Department of Radiology, University of Patras (Greece)

    2007-07-15

    Chondroblastoma is a rare benign cartilaginous bone tumor. Surgical resection is the treatment of choice for pain relief and prevention of further growth. Open surgical techniques are associated with complications, particularly when the tumors are located in deep anatomical sites. The authors performed RF ablation in two cases of subarticular femoral head chondroblastomas and emphasize its positive impact. The clinical course, the radiological findings and the post treatment results are discussed.

  10. Femtosecond Laser Ablation of Solid Targets using Gaussian and Vortex Beams

    OpenAIRE

    Kiliyanamkandy, Anoop

    2015-01-01

    This thesis presents a detailed investigation of laser ablation of solid targets with femtosecond (fs) pulses, focusing on three prominent aspects: 1) spatial and temporal evolution of the laser produced plume, in high vacuum condition; 2) nanoparticles generation in high vacuum and applications of nanostructured films in material science; 3) surface micro/nanostructure formation, in ambient condition. Most of the experiments were carried out on pure copper and silicon targets, and some of th...

  11. Fluorescence Enhancement Ratio Dropdown at Low Fluences during Femtosecond Double Pulse Laser Ablation

    Institute of Scientific and Technical Information of China (English)

    Sima SINGHA; Robert J. GORDON; HU Zhan

    2008-01-01

    In the study of double pulse ablation of materials (silicon and copper), a dropdown of double pulse to single pulse fluorescence signal enhancement at low fluences is observed. The dropdown is analysed with a simple theoretical one-dimensional heat diffusion model and verified by fluorescence time constants change as a function of fluence. The dropdown is explained as a result of liquid-solid mixture layer at the liquid and solid boundary. The effect of the layer becomes important at low fluences.

  12. Comparison of Theoretical and Experimental Values for the Effective Heat of Ablation of Ammonium Chloride

    Science.gov (United States)

    Welker, Jean E.

    1960-01-01

    Thermodynamic properties of ammonium chloride have been obtained and applied to a theoretical analysis of the shielding mechanism which reduces the rate of heat transfer to a body when ablation takes place at the surface. The analysis has considered the mechanism as one in which the material sublimes directly from the solid to the vapor phase. The results of the computation are compared with the experimental results obtained from the Langley 700-kilowatt arc jet.

  13. Radiofrequency Ablation to Treat Loco-Regional Recurrence of Well-Differentiated Thyroid Carcinoma

    OpenAIRE

    Lee, Sun Jin; Jung, So Lyung; Kim, Bum Soo; Ahn, Kook Jin; Choi, Hyun Seok; Lim, Dong Jun; Kim, Min Hee; Bae, Ja Seong; Kim, Min Sik; Jung, Chan Kwon; Chong, Se Min

    2014-01-01

    Objective To evaluate the efficacy of radiofrequency ablation (RFA) in the treatment of loco-regional, recurrent, and well-differentiated thyroid carcinoma. Materials and Methods Thirty-five recurrent well-differentiated thyroid carcinomas (RTC) in 32 patients were treated with RFA, between March 2008 and October 2011. RTCs were detected by regular follow-up ultrasound and confirmed by biopsy. All patients had fewer than 3 RTCs in the neck and were at high surgical risk or refused to undergo ...

  14. A tubular electrode for radiofrequency ablation therapy

    KAUST Repository

    Antunes, Carlos Lemos Lemos Lemos

    2012-07-06

    Purpose – Due to its good mechanical and biocompatibility characteristics, nitinol SEMS is a popular endoprothesis used for relieving stricture problems in hollow organs due to carcinomas. Besides its mechanical application, SEMS can be regarded as well as potential electrode for performing RF ablation therapy on the tumor. The purpose of this work is to perform numerical and experimental analyses in order to characterize the lesion volume induced in biological tissue using this kind of tubular electrode. Design/methodology/approach – Data concerning electrical conductivity and dimension of the damaged tissue after RF ablation procedure were obtained from ex vivo samples. Next, numerical models using 3D finite element method were obtained reassembling the conditions considered at experimentation setup and results were compared. Findings – Numerical and experimental results show that a regular volume of damaged tissue can be obtained considering this type of electrode. Also, results obtained from numerical simulation are close to those obtained by experimentation. Originality/value – SEMSs, commonly used as devices to minimize obstruction problems due to the growth of tumors, may still be considered as an active electrode for RF ablation procedures. A method considering this observation is presented in this paper. Also, numerical simulation can be regarded in this case as a tool for determining the lesion volume.

  15. Ultraviolet laser ablation of polyimide films

    Science.gov (United States)

    Srinivasan, R.; Braren, B.; Dreyfus, R. W.

    1987-01-01

    Pulsed laser radiation at 193, 248, or 308 nm can etch films of polyimide (DuPont KaptonTM). The mechanism of this process has been examined by the chemical analysis of the condensible products, by laser-induced fluorescence analysis of the diatomic products, and by the measurement of the etch depth per pulse over a range of fluences of the laser pulse. The most important product as well as the only one condensible at room temperature is carbon. Laser-induced fluorescence analysis showed that C2 and CN were present in the ablation plume. At 248 nm, even well below the fluence threshold of 0.08 J/cm2 for significant ablation, these diatomic species are readily detected and are measured to leave the polymer surface with translational energy of ˜5 eV. These results, when combined with the photoacoustic studies of Dyer and Srinivasan [Appl. Phys. Lett. 48, 445 (1986)], show that a simple photochemical mechanism in which one photon or less (on average) is absorbed per monomer is inadequate. The ablation process must involve many photons per monomer unit to account for the production of predominantly small (<4 atoms) products and the ejection of these fragments at supersonic velocities.

  16. Laser ablation cell sorting in scanning cytometry

    Science.gov (United States)

    Shen, Feimo; Price, Jeffrey H.

    2001-05-01

    Flow cytometry has been an important tool for automated cells sorting. However, the lack of good sensitivity prevents it from being used for rare events sorting; furthermore, fragile cells, anchorage-dependent cells, and clump forming cells cannot be sorted this way. A fully automated, high-speed scanning cytometer with autofocus and image segmentation is capable of accurately locating contaminant cells in a monolayer cell population. A laser ablation system was incorporated into the cytometer to negatively sort out the unwanted cells by applying a focused, ultra-short laser pulse (sub-micron diameter, pulse duration = 4 nsec, wavelength - 500 nm) to each targeted cell. Due to the high power density (approximately 1010 W/cm2) that was present at the focal point, disruptive mechanical forces were generated and were responsible for the kill. Fluorescently stained NIH-3T3 fibroblast cells were used as a model contaminant target ells in an unstained NIH-3T3 population to determine the identification-kill effectiveness. The contaminant cells were stained with the fluorochrome CellTracker Blue CMAC, whereas the background cells were left intact. Ablation pulses were applied in frame-by-frame increment batches to the cell culture on the microscope. The negative sorting effectiveness was analyzed by automatically re-scanning the post-ablation cell culture in phase contrast and propidium iodide stained epi fluorescent fields to verify cell death.

  17. Microwave soft tissue ablation (Invited Paper)

    Science.gov (United States)

    Clegg, Peter J.; Cronin, Nigel J.

    2005-04-01

    Microsulis, in conjunction with the University of Bath have developed a set of novel microwave applicators for the ablation of soft tissues. These interstitial applicators have been designed for use in open surgical, laparoscopic and percutaneous settings and range in diameter from 2.4 to 7 mm. A 20 mm diameter flat faced interface applicator was developed as an adjunct to the open surgical interstitial applicator and has been applied to the treatment of surface breaking lesions in hepatobiliary surgery. Taken as a complete tool set the applicators are capable of treating a wide range of conditions in a safe and efficacious manner. The modality employs a radiated electromagnetic field at the allocated medical frequency of 2.45 GHz and powers between 30 and 150 Watts. Computer simulations, bench testing, safety and efficacy testing, ex-vivo and in-vivo work plus clinical trials have demonstrated that these systems are capable of generating large volumes of ablation in short times with favourable ablation geometries. Clinical studies have shown very low complication rates with minimal local recurrence. It is considered that this modality offers major advantages over currently marketed products. The technique is considered to be particularly safe as it is quick and there is no passage of current obviating the requirement for grounding pads. Since the microwave field operates primarily on water and all soft tissues with the exception of fat are made up of approximately 70% water the heating pattern is highly predictable making repeatability a key factor for this modality.

  18. Initial Results of Image-Guided Percutaneous Ablation as Second-Line Treatment for Symptomatic Vascular Anomalies

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, Scott M., E-mail: Thompson.scott@mayo.edu [Mayo Clinic, Mayo Graduate School, Mayo Medical School and the Mayo Clinic Medical Scientist Training Program, College of Medicine (United States); Callstrom, Matthew R., E-mail: callstrom.matthew@mayo.edu; McKusick, Michael A., E-mail: mckusick.michael@mayo.edu; Woodrum, David A., E-mail: woodrum.david@mayo.edu [Mayo Clinic, Department of Radiology, College of Medicine (United States)

    2015-10-15

    PurposeThe purpose of this study was to determine the feasibility, safety, and early effectiveness of percutaneous image-guided ablation as second-line treatment for symptomatic soft-tissue vascular anomalies (VA).Materials and MethodsAn IRB-approved retrospective review was undertaken of all patients who underwent percutaneous image-guided ablation as second-line therapy for treatment of symptomatic soft-tissue VA during the period from 1/1/2008 to 5/20/2014. US/CT- or MRI-guided and monitored cryoablation or MRI-guided and monitored laser ablation was performed. Clinical follow-up began at one-month post-ablation.ResultsEight patients with nine torso or lower extremity VA were treated with US/CT (N = 4) or MRI-guided (N = 2) cryoablation or MRI-guided laser ablation (N = 5) for moderate to severe pain (N = 7) or diffuse bleeding secondary to hemangioma–thrombocytopenia syndrome (N = 1). The median maximal diameter was 9.0 cm (6.5–11.1 cm) and 2.5 cm (2.3–5.3 cm) for VA undergoing cryoablation and laser ablation, respectively. Seven VA were ablated in one session, one VA initially treated with MRI-guided cryoablation for severe pain was re-treated with MRI-guided laser ablation due to persistent moderate pain, and one VA was treated in a planned two-stage session due to large VA size. At an average follow-up of 19.8 months (range 2–62 months), 7 of 7 patients with painful VA reported symptomatic pain relief. There was no recurrence of bleeding at five-year post-ablation in the patient with hemangioma–thrombocytopenia syndrome. There were two minor complications and no major complications.ConclusionImage-guided percutaneous ablation is a feasible, safe, and effective second-line treatment option for symptomatic VA.

  19. One-step fabrication of superhydrophobic hierarchical structures by femtosecond laser ablation

    Energy Technology Data Exchange (ETDEWEB)

    Rukosuyev, Maxym V.; Lee, Jason [Mechanical Engineering, University of Victoria (Canada); Cho, Seong Jin; Lim, Geunbae [Mechanical Engineering, Pohang University of Science and Technology, Pohang (Korea, Republic of); Jun, Martin B.G., E-mail: mbgjun@uvic.ca [Mechanical Engineering, University of Victoria (Canada)

    2014-09-15

    Highlights: • Superhydrophobic surface patterns by femtosecond laser ablation in open air. • Micron scale ridge-like structure with superimposed submicron convex features. • Hydrophobic or even superhydrophobic behavior with no additional silanization. - Abstract: Hydrophobic surface properties are sought after in many areas of research, engineering, and consumer product development. Traditionally, hydrophobic surfaces are produced by using various types of coatings. However, introduction of foreign material onto the surface is often undesirable as it changes surface chemistry and cannot provide a long lasting solution (i.e. reapplication is needed). Therefore, surface modification by transforming the base material itself can be preferable in many applications. Femtosecond laser ablation is one of the methods that can be used to create structures on the surface that will exhibit hydrophobic behavior. The goal of the presented research was to create micro and nano-scale patterns that will exhibit hydrophobic properties with no additional post treatment. As a result, dual scale patterned structures were created on the surface of steel aluminum and tungsten carbide samples. Ablation was performed in the open air with no subsequent treatment. Resultant surfaces appeared to be strongly hydrophobic or even superhydrophobic with contact angle values of 140° and higher. In conclusion, the nature of surface hydrophobicity proved to be highly dependent on surface morphology as the base materials used are intrinsically hydrophilic. It was also proven that the hydrophobicity inducing structures could be manufactured using femtosecond laser machining in a single step with no subsequent post treatment.

  20. Femtosecond-resolved ablation dynamics of Si in the near field of a small dielectric particle

    Directory of Open Access Journals (Sweden)

    Paul Kühler

    2013-09-01

    Full Text Available In this work we analyze the ablation dynamics of crystalline Si in the intense near field generated by a small dielectric particle located at the material surface when being irradiated with an infrared femtosecond laser pulse (800 nm, 120 fs. The presence of the particle (7.9 μm diameter leads to a strong local enhancement (ca. 40 times of the incoming intensity of the pulse. The transient optical response of the material has been analyzed by means of fs-resolved optical microscopy in reflection configuration over a time span from 0.1 ps to about 1 ns. Characteristic phenomena like electron plasma formation, ultrafast melting and ablation, along with their characteristic time scales are observed in the region surrounding the particle. The use of a time resolved imaging technique allows us recording simultaneously the material response at ordinary and large peak power densities enabling a direct comparison between both scenarios. The time resolved images of near field exposed regions are consistent with a remarkable temporal shift of the ablation onset which occurs in the sub-picosend regime, from about 500 to 800 fs after excitation.

  1. Ultrafast laser-induced melting and ablation studied by time-resolved diffuse X-ray scattering

    Directory of Open Access Journals (Sweden)

    Meyer zu Heringdorf F.

    2013-03-01

    Full Text Available Time-resolved diffuse X-ray scattering with 50 fs, 9.5 keV X-ray pulses from the Linear Coherent Light Source was used to study the structural dynamics in materials undergoing rapid melting and ablation after fs laser excitation.

  2. Clinical outcome of percutaneous RF-ablation of non-operable patients with liver metastasis from breast cancer

    DEFF Research Database (Denmark)

    Kümler, Iben; Parner, Vibeke Kirk; Tuxen, Malgorzata K.

    2015-01-01

    PURPOSE: Despite improved anti-neoplastic treatment the prognosis for patients with liver metastases from metastatic breast cancer remains poor. MATERIALS AND METHODS: Thirty-two consecutive patients with metastatic breast cancer treated with radiofrequency ablation (RFA) at the Department of Onc...

  3. Transient Newton rings in dielectrics upon fs laser ablation

    CERN Document Server

    Garcia-Lechuga, Mario; Hernandez-Rueda, Javier; Solis, Javier

    2014-01-01

    We report the appearance of transient Newton rings in dielectrics (sapphire and lead-oxide glass) during ablation with single fs laser pulses. Employing femtosecond microscopy with 800 nm excitation and 400 nm illumination, we observe a characteristic ring pattern that dynamically changes for increasing delay times between pump and probe pulse. Such transient Newton rings have been previously observed in metals and semiconductors at fluences above the ablation threshold and were related to optical interference of the probe beam reflected at the front surface of the ablating layer and at the interface of the non-ablating substrate. Yet, it had been generally assumed that this phenomenon cannot be (and has not been) observed in dielectrics due to the different ablation mechanism and optical properties of dielectrics. The fact that we are able to observe them has important consequences for the comprehension of the ablation mechanisms in dielectrics and provides a new method for investigating these mechanisms in ...

  4. Ultrasound guided percutaneous microwave ablation of benign thyroid nodules: Safety and imaging follow-up in 222 patients

    Energy Technology Data Exchange (ETDEWEB)

    Yue, Wenwen [Binzhou Medical University, #346 Guan-hai Road, Lai-shan, Yantai, Shandong 264003 (China); Wang, Shurong, E-mail: 7762808@sina.com [Department of Ultrasound, Muping Area People' s Hospital, #629 Nan-hua Street, Mu-ping, Yantai, Shandong 264100 (China); Wang, Bin [Binzhou Medical University, #346 Guan-hai Road, Lai-shan, Yantai, Shandong 264003 (China); Xu, Qingling; Yu, Shoujun; Yonglin, Zhang; Wang, Xiju [Department of Ultrasound, Muping Area People' s Hospital, #629 Nan-hua Street, Mu-ping, Yantai, Shandong 264100 (China)

    2013-01-15

    Objective: Microwave ablation is a minimally invasive technique that has been used to treat benign and malignant tumors of liver, lung and kidney. Towards thyroid nodules, only a few cases are reported so far. The aim of the study was to investigate the effectiveness and safety of ultrasound-guided percutaneous microwave ablation in the treatment of benign thyroid nodules with a large sample. Materials and methods: A total of 477 benign thyroid nodules in 222 patients underwent microwave ablation in our department from July 2009 to March 2012. Microwave ablation was carried out using microwave antenna (16G) under local anesthesia. Nodule volume, thyroid function and clinical symptoms were evaluated before treatment and at 1, 3, more than 6 months. The study was ethics committee approved and written informed consents were obtained from all patients. Results: All thyroid nodules significantly decreased in size after microwave ablation. A 6-month follow-up was achieved in 254 of 477 nodules, and the mean decrease in the volume of thyroid nodules was from 2.13 ± 4.42 ml to 0.45 ± 0.90 ml, with a mean percent decrease of 0.65 ± 0.65. A volume-reduction ratio greater than 50% was observed in 82.3% (209/254) of index nodules, and 30.7% (78/254) of index nodules disappeared 6-month after the ablation. The treatment was well tolerated and no major complications were observed except pain and transient voice changes. Conclusions: Microwave ablation seems to be a safe and effective technique for the treatment of benign thyroid nodules. Further prospective randomized studies are needed to define the role of the procedure in the treatment of thyroid nodules.

  5. Steerable sheath technology in the ablation of atrial fibrillation.

    Science.gov (United States)

    Joseph, Jubin; Wong, Kelvin C K; Ginks, Matthew R; Bashir, Yaver; Betts, Timothy R; Rajappan, Kim

    2013-12-01

    Steerable sheaths have been shown to reduce procedure time in the catheter ablation of atrial fibrillation (AF), where catheter positioning and stability is typically challenging. This review critically addresses and highlights the recent developments in design of sheaths used to manipulate the ablation catheter and how these developments may impact on the ablation procedure itself, in particular the likelihood of first-time success. Patents relating to steerable sheaths are reviewed and discussed to gauge potential future developments in this area.

  6. Patients’ survival in lung malignancies treated by microwave ablation: our experience on 56 patients

    Energy Technology Data Exchange (ETDEWEB)

    Belfiore, G.; Ronza, F. [Department of Diagnostic Imaging, “S. Anna-S. Sebastiano” Hospital, Via F. Palasciano, 81100 Caserta (Italy); Belfiore, M.P., E-mail: mariapaola.belfiore@virgilio.it [Institute of Radiology, Second University of Naples, Piazza Miraglia, 80138 Naples (Italy); Serao, N.; Di Ronza, G. [Department of Diagnostic Imaging, “S. Anna-S. Sebastiano” Hospital, Via F. Palasciano, 81100 Caserta (Italy); Grassi, R.; Rotondo, A. [Institute of Radiology, Second University of Naples, Piazza Miraglia, 80138 Naples (Italy)

    2013-01-15

    Objectives: We retrospectively evaluated percutaneous CT-guided microwave (MW) ablation safety and efficacy in unresectable lung malignancies focusing on patients’ survival. Materials and methods: All procedures were approved by the hospital ethical committee. From 2008 to 2012 we treated 69 unresectable lesions (44 lung cancer, 25 lung metastases) in 56 patients (35 men/21 women; mean age: 61.5 years). Treatment was performed under CT guidance using 14 G needles with a 3 cm active tip and a 55 W MW generator (Vivawave Microwave Coagulation System; Valley Lab). Treatment was performed at 45 W for 6–10 min. Patients were scheduled for a 3 and 6 month CT follow-up to evaluate lesion diameter and enhancement. Survival rate was evaluated by Kaplan–Meier analysis. Results: Ablation procedures were completed according to protocol in all patients. Pneumothorax occurred in 18 patients and 8 required chest tube. Four lesions (all >4.3 cm) were retreated 20 days after the ablation because of peripheral focal areas of residual tumor. Follow-up CT evaluation showed a decrease in maximum diameter in 44/69 lesions (64%) and in 42/59 lesions (71%) at 3 and 6 months, respectively. In all cases no pathologic enhancement was observed. Cancer-specific mortality yielded a survival rate of 69% at 12 months, 54% at 24 months and 49% at 36 months, respectively. An estimate mean for survival time was 27.8 months with a standard error of 2.8 months (95% confidence interval: 22.4–33.2 months). Conclusion: Based on our experience, MW ablation seems to represent a potential safe and effective percutaneous technique in the treatment of lung malignancies. MW ablation may improve survival in patients not suitable to surgery.

  7. Effects of oxytocin on high intensity focused ultrasound (HIFU) ablation of adenomysis: A prospective study

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xin [State Key Laboratory of Ultrasound Engineering in Medicine Co-founded by Chongqing and the Ministry of Science and Technology, Chongqing Key laboratory of Ultrasound in Medicine and Engineering, College of Biomedical Engineering, Chongqing Medical University, Chongqing 400016 (China); Zou, Min; Zhang, Cai [Department of Obstetrics and Gynecology, Chongqing Haifu Hospital, Chongqing 401121 (China); He, Jia [Department of Obstetrics and Gynecology, Suining Central Hospital, Sichuan 629000 (China); Mao, Shihua [Department of Obstetrics and Gynecology, Three Gorges Central Hospital, Chongqing 404000 (China); Wu, Qingrong [Department of Obstetrics and Gynecology, Fuling Central Hospital, Chongqing 408099 (China); He, Min [State Key Laboratory of Ultrasound Engineering in Medicine Co-founded by Chongqing and the Ministry of Science and Technology, Chongqing Key laboratory of Ultrasound in Medicine and Engineering, College of Biomedical Engineering, Chongqing Medical University, Chongqing 400016 (China); Department of Obstetrics and Gynecology, Suining Central Hospital, Sichuan 629000 (China); Wang, Jian [Department of Obstetrics and Gynecology, Chongqing Haifu Hospital, Chongqing 401121 (China); Department of Obstetrics and Gynecology, Three Gorges Central Hospital, Chongqing 404000 (China); Zhang, Ruitao [Department of Obstetrics and Gynecology, Chongqing Haifu Hospital, Chongqing 401121 (China); Department of Obstetrics and Gynecology, Fuling Central Hospital, Chongqing 408099 (China); Zhang, Lian, E-mail: lianwzhang@yahoo.com [State Key Laboratory of Ultrasound Engineering in Medicine Co-founded by Chongqing and the Ministry of Science and Technology, Chongqing Key laboratory of Ultrasound in Medicine and Engineering, College of Biomedical Engineering, Chongqing Medical University, Chongqing 400016 (China); Department of Obstetrics and Gynecology, Chongqing Haifu Hospital, Chongqing 401121 (China)

    2014-09-15

    Objective: To investigate the effects of oxytocin on high-intensity focused ultrasound (HIFU) ablation for the treatment of adenomyosis. Materials and methods: Eighty-six patients with adenomyosis from three hospitals were randomly assigned to the oxytocin group or control group for HIFU treatment. During HIFU treatment, 80 units of oxytocin was added in 500 ml of 0.9% normal saline running at the rate of 2 ml/min (0.32 U/min) in the oxytocin group, while 0.9% normal saline was used in the control group. Both patients and HIFU operators were blinded to oxytocin or saline application. Treatment results, adverse effects were compared. Results: When using oxytocin, the non-perfused volume (NPV) ratio was 80.7 ± 11.6%, the energy-efficiency factor (EEF) was 8.1 ± 9.9 J/mm{sup 3}, and the sonication time required to ablate 1 cm{sup 3} was 30.0 ± 36.0 s/cm{sup 3}. When not using oxytocin, the non-perfused volume ratio was 70.8 ± 16.7%, the EEF was 15.8 ± 19.6 J/mm{sup 3}, and the sonication time required to ablate 1 cm{sup 3} was 58.2 ± 72.7 S/cm{sup 3}. Significant difference in the NPV ratio, EEF, and the sonication time required to ablate 1 cm{sup 3} between the two groups was observed. No oxytocin related adverse effects occurred. Conclusion: Oxytocin could significantly decrease the energy for ablating adenomyosis with HIFU, safely enhance the treatment efficiency.

  8. Percutaneous osteoid osteoma treatment with combination of radiofrequency and alcohol ablation

    Energy Technology Data Exchange (ETDEWEB)

    Akhlaghpoor, S. [Noor Medical Imaging Center, Tehran (Iran, Islamic Republic of)]. E-mail: akhlaghpoor@nmri-ir.com; Tomasian, A. [Noor Medical Imaging Center, Tehran (Iran, Islamic Republic of); Arjmand Shabestari, A. [Noor Medical Imaging Center, Tehran (Iran, Islamic Republic of); Ebrahimi, M. [Noor Medical Imaging Center, Tehran (Iran, Islamic Republic of); Alinaghizadeh, M.R. [Noor Medical Imaging Center, Tehran (Iran, Islamic Republic of)

    2007-03-15

    Aim: To assess the efficacy of percutaneous osteoid osteoma treatment using a combination of radiofrequency ablation (RFA) and alcohol ablation with regard to technical and long-term clinical success. Materials and methods: From December 2001 to November 2004, RFA and subsequent alcohol ablation was performed on 54 patients with osteoid osteoma, diagnosed clinically using radiography, computed tomography (CT) and symptoms. Under general anaesthesia, treatment was performed via percutaneous access under thin section (2 mm) spiral CT guidance in all cases with an 11 G radiofrequency-compatible coaxial needle and 2 mm coaxial drill system and 1.0 cm active tip 17 G non-cooled radiofrequency needle. RFA was performed at 90 {sup o}C for a period of 6 min. After needle removal, 0.5-1.0 ml absolute alcohol (99.8% concentration) was injected directly into the nidus using a 20 G needle. Patients were discharged within 24 h and followed up clinically (at 1 week, 1 month and every 3 months thereafter). Results: The technical success rate was 100%. Complications occurred in two patients consisting of local mild cellulitis in entry site and peripheral small zone paresthesia on the anterior part of leg. The follow-up period range was 13-48 months (mean {+-} SD, 28.2 {+-} 7.4 months). Prompt pain relief and return to normal activities were observed in 52 of 54 patients. Recurrent pain occurred in two patients after a 1 and 3 months period of being pain free, respectively; a second RFA and alcohol ablation was performed achieving successful results. Primary and secondary clinical success rates were 96.3% (52/54 patients) and 100% (2/2 patients), respectively. Conclusion: Percutaneous osteoid osteoma treatment with combination of radiofrequency and alcohol ablation is safe, effective and minimally invasive with high primary and secondary success rates. Persistent or recurrent lesions can be effectively re-treated.

  9. In Situ Geochemical Analysis and Age Dating of Rocks Using Laser Ablation-Miniature Mass Spectrometer

    Science.gov (United States)

    Sinha, Mahadeva P.; Hecht, Michael H.; Hurowitz, Joel A.

    2012-01-01

    A miniaturized instrument for performing chemical and isotopic analysis of rocks has been developed. The rock sample is ablated by a laser and the neutral species produced are analyzed using the JPL-invented miniature mass spectrometer. The direct sampling of neutral ablated material and the simultaneous measurement of all the elemental and isotopic species are the novelties of this method. In this laser ablation-miniature mass spectrometer (LA-MMS) method, the ablated neutral atoms are led into the electron impact ionization source of the MMS, where they are ionized by a 70-eV electron beam. This results in a secondary ion pulse typically 10-100 microsecond wide, compared to the original 5-10-nanosecond laser pulse duration. Ions of different masses are then spatially dispersed along the focal plane of the magnetic sector of the miniature mass spectrometer and measured in parallel by a modified CCD (charge-coupled device) array detector capable of detecting ions directly. Compared to conventional scanning techniques, simultaneous measurement of the ion pulse along the focal plane effectively offers a 100% duty cycle over a wide mass range. LAMMS offers a more quantitative assessment of elemental composition than techniques that detect laser-ionized species produced directly in the ablation process because the latter can be strongly influenced by matrix effects that vary with the structure and geometry of the surface, the laser beam, and the ionization energies of the elements. The measurement of high-precision isotopic ratios and elemental composition of different rock minerals by LAMMS method has been demonstrated. The LA-MMS can be applied for the absolute age determination of rocks. There is no such instrument available presently in a miniaturized version that can be used for NASA space missions. Work is in progress in the laboratory for geochronology of rocks using LA-MMS that is based on K-Ar radiogenic dating technique.

  10. [Moist ablation of the corneal surface with the Er:YAG laser. Results of optimizing ablation].

    Science.gov (United States)

    Bende, T; Jean, B; Matallana, M; Seiler, T; Steiner, R

    1994-10-01

    The Er:YAG laser, emitting light at 2.94 microns, may be an alternative to the 193 nm excimer laser for photorefractive keratectomy. Compared to the excimer laser, the ablation rate is very high. Surface roughness is also more pronounced than for the excimer laser. Using a precorneal liquid film, these two factors can be reduced, as shown in ablation experiments performed on porcine corneas. Thermal damage of the remaining corneal tissue is another side effect. There is no significant decrease in the amount of thermal damage with this new technique,--not even when the pulse length is reduced.

  11. Ablation and optical third-order nonlinearities in Ag nanoparticles

    Directory of Open Access Journals (Sweden)

    Carlos Torres-Torres

    2010-11-01

    Full Text Available Carlos Torres-Torres1, Néstor Peréa-López2, Jorge Alejandro Reyes-Esqueda3, Luis Rodríguez-Fernández3, Alejandro Crespo-Sosa3, Juan Carlos Cheang-Wong3, Alicia Oliver31Section of Graduate Studies and Research, School of Mechanical and Electrical Engineering, National Polytechnic Institute, Zacatenco, Distrito Federal, Mexico; 2Laboratory for Nanoscience and Nanotechnology Research and Advanced Materials Department, IPICYT, Camino a la Presa San Jose, San Luis Potosi, Mexico; 3Instituto de Física, Universidad Nacional Autónoma de México, A.P. 20-364, México, D.F. 01000, MéxicoAbstract: The optical damage associated with high intensity laser excitation of silver nanoparticles (NPs was studied. In order to investigate the mechanisms of optical nonlinearity of a nanocomposite and their relation with its ablation threshold, a high-purity silica sample implanted with Ag ions was exposed to different nanosecond and picosecond laser irradiations. The magnitude and sign of picosecond refractive and absorptive nonlinearities were measured near and far from the surface plasmon resonance (SPR of the Ag NPs with a self-diffraction technique. Saturable optical absorption and electronic polarization related to self-focusing were identified. Linear absorption is the main process involved in nanosecond laser ablation, but nonlinearities are important for ultrashort picosecond pulses when the absorptive process become significantly dependent on the irradiance. We estimated that near the resonance, picosecond intraband transitions allow an expanded distribution of energy among the NPs, in comparison to the energy distribution resulting in a case of far from resonance, when the most important absorption takes place in silica. We measured important differences in the ablation threshold and we estimated that the high selectiveness of the SPR of Ag NPs as well as their corresponding optical nonlinearities can be strongly significant for laser

  12. Multi-modal albedo distributions in the ablation area of the southwestern Greenland Ice Sheet

    Science.gov (United States)

    Moustafa, S. E.; Rennermalm, A. K.; Smith, L. C.; Miller, M. A.; Mioduszewski, J. R.; Koenig, L. S.; Hom, M. G.; Shuman, C. A.

    2015-05-01

    of bare ice expansion at the expense of snow, surface meltwater ponding, and melting of outcropped ice layers enriched with mineral materials, enabling dust and impurities to accumulate. As climate change continues in the Arctic region, understanding the seasonal evolution of ice sheet surface types in Greenland's ablation area is critical to improve projections of mass loss contributions to sea level rise.

  13. Numerical simulation of copper ablation by ultrashort laser pulses

    CERN Document Server

    Ding, PengJi; Li, YuHong

    2011-01-01

    Using a modified self-consistent one-dimensional hydrodynamic lagrangian fluid code, laser ablation of solid copper by ultrashort laser pulses in vacuum was simulated to study fundamental mechanisms and to provide a guide for drilling periodic microholes or microgratings on the metal surface. The simulated laser ablation threshold is a approximate constancy in femtosecond regime and increases as the square root of pulse duration in picosecond regime. The ablation depth as a function of pulse duration shows four different regimes and a minimum for a pulse duration of ~ 12ps for various laser fluences. The influence of laser-induced plasma shielding on ablation depth is also studied.

  14. Thermal character in organic polymers with nanojoule femtosecond laser ablation

    Institute of Scientific and Technical Information of China (English)

    Xiaochang Ni(倪晓昌); Ching-Yue Wang(王清月); Yanfeng Li(栗岩峰); Minglie Hu(胡明列); Zhuan Wang(王专); Lu Chai(柴路)

    2003-01-01

    Ablation experiments with femtosecond (fs) laser pulse (pulse duration 37 fs, wavelength 800 nm) on organic polymers have been performed in air. The ablation threshold is found to be only several nanojoules. The diameters of the dots ablated in the organic polymers are influenced by the laser fluence and the number of laser pulses. It is observed that heat is diffused in a threadlike manner in all directions around the central focus region. Explanations of the observed phenomena are presented. A one-dimensional waveguide is also ablated in the organic polymers.

  15. Excimer laser ablation of thin titanium oxide films on glass

    Energy Technology Data Exchange (ETDEWEB)

    Overschelde, O. van [Condensed Matter Physics Group, University of Mons-Hainaut, B-7000 Mons (Belgium); Dinu, S. [University of ' Valahia' , Targoviste (Romania); Guisbiers, G. [Condensed Matter Physics Group, University of Mons-Hainaut, B-7000 Mons (Belgium); Monteverde, F. [Materia Nova, Unit of Electronic Microscopy, B-7000 Mons (Belgium); Nouvellon, C. [Materia Nova, Inorganic and Analytical Chemistry, B-7000 Mons (Belgium); Wautelet, M. [Condensed Matter Physics Group, University of Mons-Hainaut, B-7000 Mons (Belgium)]. E-mail: michel.wautelet@umh.ac.be

    2006-04-30

    Thin titanium dioxide films are deposited on glass substrates by magnetron sputter deposition. They are irradiated in air, by means of a KrF excimer laser. The ablation rate is measured as a function of the laser fluence per pulse, F, and of the number of pulses, N. Above a fluence threshold, the films are partially ablated. The ablated thickness does not vary linearly with N. This is the signature of a negative feedback between the film thickness and the ablation rate. The origin of this negative feedback is shown to be due to either thermal or electronic effects, or both. At high F, the film detachs from the substrate.

  16. Development of laser ablation plasma by anisotropic self-radiation

    Directory of Open Access Journals (Sweden)

    Ohnishi Naofumi

    2013-11-01

    Full Text Available We have proposed a method for reproducing an accurate solution of low-density ablation plasma by properly treating anisotropic radiation. Monte-Carlo method is employed for estimating Eddington tensor with limited number of photon samples in each fluid time step. Radiation field from ablation plasma is significantly affected by the anisotropic Eddington tensor. Electron temperature around the ablation surface changes with the radiation field and is responsible for the observed emission. An accurate prediction of the light emission from the laser ablation plasma requires a careful estimation of the anisotropic radiation field.

  17. CT-guided radiofrequency tumor ablation in children

    Energy Technology Data Exchange (ETDEWEB)

    Botsa, Evanthia [National and Kapodistrian University of Athens, First Pediatric Clinic, Agia Sofia Children' s Hospital, Athens (Greece); Poulou, Loukia S.; Koundouraki, Antonia; Thanos, Loukas [Sotiria General Hospital for Chest Diseases, Department of Medical Imaging and Interventional Radiology, Athens (Greece); Koutsogiannis, Ioannis [General Military Hospital NIMTS, Department of Medical Imaging, Athens (Greece); Ziakas, Panayiotis D. [Warren Alpert Medical School of Brown University Rhode Island Hospital, Division of Infectious Diseases, Providence, RI (United States); Alexopoulou, Efthimia [Attikon University Hospital, Second Department of Radiology, Athens University School of Medicine, Athens (Greece)

    2014-11-15

    Image-guided radiofrequency ablation is a well-accepted technique of interventional oncology in adults. To evaluate the efficacy and safety of CT-guided radiofrequency ablation as a minimally invasive treatment for metastatic neoplasms in children. A total of 15 radiofrequency ablation sessions were performed in 12 children and young adults (median age 9.5; range 5-18 years) with metastatic malignancies. Seven children and young adults had secondary hepatic lesions, three had pulmonary and two had bone lesions. Radiofrequency ablation was performed under conscious sedation. The median lesion size was 1.7 cm (range 1.3-2.8 cm). The median time for ablation was 8 min (range 7-10 min). Radiofrequency procedures were technically successful in all tumors. Postablation imaging immediately after, and 1 month and 3 months after radiofrequency ablation showed total necrosis in all patients. At 6-month follow-up, three patients (all with lesion size >2 cm) had local recurrence and underwent a second radiofrequency ablation session. At 2-year follow-up no patient had recurrence of the treated tumor. Post-ablation syndrome occurred in four children. No major complication occurred. CT-guided radiofrequency tumor ablation was safe and efficient for palliative treatment in our cohort of patients. (orig.)

  18. Comparison of laser ablation and dried solution aerosol as sampling systems in inductively coupled plasma mass spectrometry.

    Science.gov (United States)

    Coedo, A G; Padilla, I; Dorado, M T

    2004-12-01

    This paper describes a study designed to determine the possibility of using a dried aerosol solution for calibration in laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The relative sensitivities of tested materials mobilized by laser ablation and by aqueous nebulization were established, and the experimentally determined relative sensitivity factors (RSFs) were used in conjunction with aqueous calibration for the analysis of solid steel samples. To such a purpose a set of CRM carbon steel samples (SS-451/1 to SS-460/1) were sampled into an ICP-MS instrument by solution nebulization using a microconcentric nebulizer with membrane desolvating (D-MCN) and by laser ablation (LA). Both systems were applied with the same ICP-MS operating parameters and the analyte signals were compared. The RSF (desolvated aerosol response/ablated solid response) values were close to 1 for the analytes Cr, Ni, Co, V, and W, about 1.3 for Mo, and 1.7 for As, P, and Mn. Complementary tests were carried out using CRM SS-455/1 as a solid standard for one-point calibration, applying LAMTRACE software for data reduction and quantification. The analytical results are in good agreement with the certified values in all cases, showing that the applicability of dried aerosol solutions is a good alternative calibration system for laser ablation sampling.

  19. CT-guided Bipolar and Multipolar Radiofrequency Ablation (RF Ablation) of Renal Cell Carcinoma: Specific Technical Aspects and Clinical Results

    Energy Technology Data Exchange (ETDEWEB)

    Sommer, C. M., E-mail: christof.sommer@med.uni-heidelberg.de [University Hospital Heidelberg, INF 110, Department of Diagnostic and Interventional Radiology (Germany); Lemm, G.; Hohenstein, E. [Minimally Invasive Therapies and Nuclear Medicine, SLK Kliniken Heilbronn GmbH, Clinic for Radiology (Germany); Bellemann, N.; Stampfl, U. [University Hospital Heidelberg, INF 110, Department of Diagnostic and Interventional Radiology (Germany); Goezen, A. S.; Rassweiler, J. [Clinic for Urology, SLK Kliniken Heilbronn GmbH (Germany); Kauczor, H. U.; Radeleff, B. A. [University Hospital Heidelberg, INF 110, Department of Diagnostic and Interventional Radiology (Germany); Pereira, P. L. [Minimally Invasive Therapies and Nuclear Medicine, SLK Kliniken Heilbronn GmbH, Clinic for Radiology (Germany)

    2013-06-15

    Purpose. This study was designed to evaluate the clinical efficacy of CT-guided bipolar and multipolar radiofrequency ablation (RF ablation) of renal cell carcinoma (RCC) and to analyze specific technical aspects between both technologies. Methods. We included 22 consecutive patients (3 women; age 74.2 {+-} 8.6 years) after 28 CT-guided bipolar or multipolar RF ablations of 28 RCCs (diameter 2.5 {+-} 0.8 cm). Procedures were performed with a commercially available RF system (Celon AG Olympus, Berlin, Germany). Technical aspects of RF ablation procedures (ablation mode [bipolar or multipolar], number of applicators and ablation cycles, overall ablation time and deployed energy, and technical success rate) were analyzed. Clinical results (local recurrence-free survival and local tumor control rate, renal function [glomerular filtration rate (GFR)]) and complication rates were evaluated. Results. Bipolar RF ablation was performed in 12 procedures and multipolar RF ablation in 16 procedures (2 applicators in 14 procedures and 3 applicators in 2 procedures). One ablation cycle was performed in 15 procedures and two ablation cycles in 13 procedures. Overall ablation time and deployed energy were 35.0 {+-} 13.6 min and 43.7 {+-} 17.9 kJ. Technical success rate was 100 %. Major and minor complication rates were 4 and 14 %. At an imaging follow-up of 15.2 {+-} 8.8 months, local recurrence-free survival was 14.4 {+-} 8.8 months and local tumor control rate was 93 %. GFR did not deteriorate after RF ablation (50.8 {+-} 16.6 ml/min/1.73 m{sup 2} before RF ablation vs. 47.2 {+-} 11.9 ml/min/1.73 m{sup 2} after RF ablation; not significant). Conclusions. CT-guided bipolar and multipolar RF ablation of RCC has a high rate of clinical success and low complication rates. At short-term follow-up, clinical efficacy is high without deterioration of the renal function.

  20. Future requirements for advanced materials

    Science.gov (United States)

    Olstad, W. B.

    1980-01-01

    Recent advances and future trends in aerospace materials technology are reviewed with reference to metal alloys, high-temperature composites and adhesives, tungsten fiber-reinforced superalloys, hybrid materials, ceramics, new ablative materials, such as carbon-carbon composite and silica tiles used in the Shuttle Orbiter. The technologies of powder metallurgy coupled with hot isostatic pressing, near net forging, complex large shape casting, chopped fiber molding, superplastic forming, and computer-aided design and manufacture are emphasized.

  1. Electroporation ablation: A new energy modality for ablation of arrhythmogenic cardiac substrate

    NARCIS (Netherlands)

    van Driel, VJHM

    2016-01-01

    At the very end of the Direct Current (DC) era, low-energy DC ablation was demonstrated to cause myocardial lesions by non-thermal irreversible electroporation (IRE) (permanent formation of pores in the cell membrane, leading to cell death), without arcing and/or barotrauma. To eliminate rather smal

  2. Micrometeorological processes driving snow ablation in an Alpine catchment

    Directory of Open Access Journals (Sweden)

    R. Mott

    2011-08-01

    Full Text Available Mountain snow covers typically become patchy over the course of a melting season. The snow pattern during melt is mainly governed by the end of winter snow depth distribution and the local energy balance. The objective of this study is to investigate micrometeorological processes driving snow ablation in an Alpine catchment. For this purpose we combine a meteorological model (ARPS with a fully distributed energy balance model (Alpine3D. Turbulent fluxes above melting snow are further investigated by using data from eddy-correlation systems. We compare modelled snow ablation to measured ablation rates as obtained from a series of Terrestrial Laser Scanning campaigns covering a complete ablation season. The measured ablation rates indicate that the advection of sensible heat causes locally increased ablation rates at the upwind edges of the snow patches. The effect, however, appears to be active over rather short distances except for very strong wind conditions. Neglecting this effect, the model is able to capture the mean ablation rates for early ablation periods but strongly overestimates snow ablation once the fraction of snow coverage is below a critical value. While radiation dominates snow ablation early in the season, the turbulent flux contribution becomes important late in the season. Simulation results indicate that the air temperatures appear to overestimate the local air temperature above snow patches once the snow coverage is below a critical value. Measured turbulent fluxes support these findings by suggesting a stable internal boundary layer close to the snow surface causing a strong decrease of the sensible heat flux towards the snow cover. Thus, the existence of a stable internal boundary layer above a patchy snow cover exerts a dominant control on the timing and magnitude of snow ablation for patchy snow covers.

  3. Dynamic evolution of a flow to localized, kinetics-driven ablation or coagulation

    Science.gov (United States)

    Hagan, Daniel; Crocker, Ryan; Dubief, Yves

    2012-11-01

    This research focuses on the numerical simulation of the ablative creation of a cavity or a coagulative formation at a wall in a flow. The fluid-solid interface is defined by a level set (LS) variable, whose transport equation is driven by the mass-loss or growth process. The boundary conditions at the fluid-solid interface are enforced by a mass and energy-conserving immersed boundary method (IBM) using the ghost-fluid node approach for the latter and for the transport of chemical species. The first application of the LS/IBM algorithm is a channel flow in which both walls are cavity-free, but one wall contains a section made of ablatable material, which could correspond to a hole or gap in a spacecraft thermal protection shield. The second application is a pipe flow in which the wall is capable of accumulating material, which could describe the coagulation of blood at a vessel wall. The solid mass loss or growth is driven by one step kinetics. For both flows, the dynamical interplay between the ablative or coagulative patch is investigated through statistics and flow topology. We gratefully acknowledge the financial support of NASA, grant No. NNX11AM07A, and NIH, grant No. P01HL46703, and the computational support of the Vermont Advanced Computing Core.

  4. Effects of Nonequilibrium Chemistry and Darcy-Forchheimer Pyrolysis Flow for Charring Ablator

    Science.gov (United States)

    Chen, Yih-Kanq; Milos, Frank S.

    2013-01-01

    The fully implicit ablation and thermal response code simulates pyrolysis and ablation of thermal protection materials and systems. The governing equations, which include energy conservation, a three-component decomposition model, and a surface energy balance, are solved with a moving grid.This work describes new modeling capabilities that are added to a special version of code. These capabilities include a time-dependent pyrolysis gas flow momentum equation with Darcy-Forchheimer terms and pyrolysis gas species conservation equations with finite rate homogeneous chemical reactions. The total energy conservation equation is also enhanced for consistency with these new additions. Two groups of parametric studies of the phenolic impregnated carbon ablator are performed. In the first group, an Orion flight environment for a proposed lunar-return trajectory is considered. In the second group, various test conditions for arcjet models are examined. The central focus of these parametric studies is to understand the effect of pyrolysis gas momentum transfer on material in-depth thermal responses with finite-rate, equilibrium, or frozen homogeneous gas chemistry. Results indicate that the presence of chemical nonequilibrium pyrolysis gas flow does not significantly alter the in-depth thermal response performance predicted using the chemical equilibrium gas model.

  5. Er:YAG laser ablation: 5-11 years prospective study

    Science.gov (United States)

    Dostalova, Tatjana; Jelinkova, Helena; Nemec, Michal; Sulc, Jan; Miyagi, Mitsunobu

    2005-03-01

    The Er:YAG laser at 2940 nm has been proposed for use in dental cavity preparation and removal of carious enamel and dentin. The purpose of the present study was to determine the effect of the Er:YAG laser ablation in treating dental caries after a period from 5 to 11 years. For this study, 133 cavities were chosen, and for their reparation of it the three restorative materials were used. Baseline examination was made in the following intervals: one week, 1 year, and from 5 to 11 years after cavity preparation and placement of filling material. Clinical assessments were carried out in accordance with the US Public Health Service System. The follow-up included: the marginal ridge, marginal adaptation, anatomic form, caries, color match, cavo surface margin discoloration, surface smoothness, and postoperative sensitivity. Er:YAG laser ablation is an excellent method for treating frontal teeth, i.e., incisors, canines, premolars, and initial occlusal caries of molars. However, visual control of non-contact therapy is necessary. Er:YAG laser ablation is safe, and it strongly reduces pain. The laser treatment markedly decreases the unpleasant sound and vibration.

  6. Laser systems for ablative fractional resurfacing

    DEFF Research Database (Denmark)

    Paasch, Uwe; Haedersdal, Merete

    2011-01-01

    ablative laser systems. Fractionated CO(2) (10,600-nm), erbium yttrium aluminum garnet, 2940-nm and yttrium scandium gallium garnet, 2790-nm lasers are available. In this article, we present an overview of AFR technology, devices and histopathology, and we summarize the current clinical possibilities...... of a variety of skin conditions, primarily chronically photodamaged skin, but also acne and burn scars. In addition, it is anticipated that AFR can be utilized in the laser-assisted delivery of topical drugs. Clinical efficacy coupled with minimal downtime has driven the development of various fractional...

  7. Radiofrequency ablation for benign thyroid nodules.

    Science.gov (United States)

    Bernardi, S; Stacul, F; Zecchin, M; Dobrinja, C; Zanconati, F; Fabris, B

    2016-09-01

    Benign thyroid nodules are an extremely common occurrence. Radiofrequency ablation (RFA) is gaining ground as an effective technique for their treatment, in case they become symptomatic. Here we review what are the current indications to RFA, its outcomes in terms of efficacy, tolerability, and cost, and also how it compares to the other conventional and experimental treatment modalities for benign thyroid nodules. Moreover, we will also address the issue of treating with this technique patients with cardiac pacemakers (PM) or implantable cardioverter-defibrillators (ICD), as it is a rather frequent occurrence that has never been addressed in detail in the literature.

  8. A study of ultrafast electron diffusion kinetics in ultrashort-pulse laser ablation of metals

    Institute of Scientific and Technical Information of China (English)

    Yang Jian-Jun; Liu Wei-Wei; Zhu Xiao-Nong

    2007-01-01

    Temperature dependence of the electron diffusion in metallic targets, where the electron-electron collision is the dominant process, is investigated with the help of an extended two-temperature model. In sharp contrast to the low electron temperature case, where only the electron-phonon collisions are commonly considered, the electron diffusion process underlying the high electron temperatures evolves dramatically different in both temporal and spatial domains.Calculated results of the ablation yield at different pulse durations are presented for a copper plate impinged by ultrashort laser pulses with energy fluences ranging from 0.1 J/cm2 to 10 J/cm2. The excellent agreement between the simulation results and the experimental data indicates the significant role of electron-electron collisions in material ablations using intense ultrashort laser pulses.

  9. Femtosecond laser ablation of polymeric substrates for the fabrication of microfluidic channels

    Energy Technology Data Exchange (ETDEWEB)

    Suriano, Raffaella, E-mail: raffaella.suriano@chem.polimi.it [Dipartimento di Chimica, Materiali e Ingegneria Chimica ' Giulio Natta' , Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan (Italy); Kuznetsov, Arseniy [Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover (Germany); Eaton, Shane M. [Istituto di Fotonica e Nanotecnologie (IFN)-CNR, Piazza Leonardo da Vinci 32, 20133 Milan (Italy); Kiyan, Roman [Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover (Germany); Cerullo, Giulio [Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan (Italy); Osellame, Roberto [Istituto di Fotonica e Nanotecnologie (IFN)-CNR, Piazza Leonardo da Vinci 32, 20133 Milan (Italy); Chichkov, Boris N. [Laser Zentrum Hannover e.V., Hollerithallee 8, 30419 Hannover (Germany); Levi, Marinella; Turri, Stefano [Dipartimento di Chimica, Materiali e Ingegneria Chimica ' Giulio Natta' , Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan (Italy)

    2011-05-01

    This manuscript presents a study of physical and chemical properties of microchannels fabricated by femtosecond laser processing technology in thermoplastic polymeric materials, including poly(methyl methacrylate) (PMMA), polystyrene (PS) and cyclic olefin polymer (COP). By surface electron microscopy and optical profilometry, the dimensions of microchannels in the polymers were found to be easily tunable, with surface roughness values comparable to those obtained by standard prototyping techniques such as micromilling. Through colorimetric analysis and optical microscopy, PMMA was found to remain nearly transparent after ablation while COP and PS darkened significantly. Using infrared spectroscopy, the darkening in PS and COP was attributed to significant oxidation and dehydrogenation during laser ablation, unlike PMMA, which was found to degrade by a thermal depolymerization process. The more stable molecular structure of PMMA makes it the most viable thermoplastic polymer for femtosecond laser fabrication of microfluidic channels.

  10. Surface modulation of silicon surface by excimer laser at laser fluence below ablation threshold

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, P. [Jawaharlal Nehru Centre for Advanced Scientific Research, Chemistry and Physics of Materials Unit (CPMU), Bangalore, Jakkur PO (India)

    2010-04-15

    Controlled single step fabrication of silicon conical surface modulations on [311] silicon surface is reported utilizing KrF excimer laser [{lambda}=248 nm] at laser fluence below ablation threshold laser fluence. When laser fluence was increased gradually from 0 to 0.2 J/cm{sup 2} for fixed 200 numbers of shots; first nanopores are observed to form at 0.1 J/cm{sup 2}, then very shallow nanocones evolve as a function of laser fluence. At 0.2 J/cm{sup 2}, nanoparticles are observed to form. Up to 0.15 J/cm{sup 2} the very shallow nanocone volume is smaller but increases at a fast rate with laser fluence thereafter. It is observed that the net material volume before and after the laser irradiation remains the same, a sign of the melting and resolidification without any ablation. (orig.)

  11. Ablation behavior of monolayer and multilayer Ir coatings under carburizing and oxidizing oxyacetylene flames

    Science.gov (United States)

    Wu, Wangping; Jiang, Jinjin; Chen, Zhaofeng

    2016-06-01

    Iridium is one of the most promising candidates for protective barrier of refractory materials to endure high service temperature. The multilayer iridium coating was produced by a double glow plasma process on the polished tungsten carbide substrates, compared with monolayer. The ablation behaviors of the monolayer on the unpolished and polished substrates were investigated under carburizing and oxidizing oxyacetylene flames, respectively, at the same time the multilayer coating ablated under oxidizing flames. Multilayer coating was a polycrystalline phase with the preferential (220) orientation. Monolayer on the unpolished substrate had fine coarse grains and some small microcracks were present. Multilayer consisted of columnar grains with some voids between the grains boundaries. The formation of a WIr phase in the as-deposited multilayer was attributed to high deposition temperature. The monolayer could endure high temperature up to 1800 °C in carburizing flame. The substrates could be protected more effectively by multilayer than monolayer at 2000- 2200 °C in oxidizing flame.

  12. Comparative Efficacy of Radiofrequency and Laser Ablation for the Treatment of Benign Thyroid Nodules

    DEFF Research Database (Denmark)

    Ha, Eun Ju; Baek, Jung Hwan; Kim, Kyung Won;

    2015-01-01

    PURPOSE: To compare the efficacy of radiofrequency ablation (RFA) and laser ablation (LA) for treatment of benign solid thyroid nodules, using a systematic review including traditional pooling and Bayesian network meta-analysis. MATERIALS AND METHODS: A comprehensive literature search in Pub.......7%). There were no major complications after either RFA or LA. CONCLUSIONS: RFA appears to be superior to LA in reducing benign solid thyroid nodule volume, despite the smaller number of treatment sessions without major side effects.......Med-MEDLINE, EMBASE, and the Cochrane Library databases identified prospective studies evaluating the percentage mean change [absolute mean change (mL)] in nodule volume after RFA or LA. Studies from January 1, 2000, to November 1, 2013, were included. Review of 128 potential papers, including a full-text review...

  13. Surface Enhanced Raman Scattering (SERS Studies of Gold and Silver Nanoparticles Prepared by Laser Ablation

    Directory of Open Access Journals (Sweden)

    Samuel P. Hernandez-Rivera

    2013-03-01

    Full Text Available Gold and silver nanoparticles (NPs were prepared in water, acetonitrile and isopropanol by laser ablation methodologies. The average characteristic (longer size of the NPs obtained ranged from 3 to 70 nm. 4-Aminobenzebethiol (4-ABT was chosen as the surface enhanced Raman scattering (SERS probe molecule to determine the optimum irradiation time and the pH of aqueous synthesis of the laser ablation-based synthesis of metallic NPs. The synthesized NPs were used to evaluate their capacity as substrates for developing more analytical applications based on SERS measurements. A highly energetic material, TNT, was used as the target compound in the SERS experiments. The Raman spectra were measured with a Raman microspectrometer. The results demonstrate that gold and silver NP substrates fabricated by the methods developed show promising results for SERS-based studies and could lead to the development of micro sensors.

  14. Resonant laser ablation of metals detected by atomic emission in a microwave plasma and by inductively coupled plasma mass spectrometry.

    Science.gov (United States)

    Cleveland, Danielle; Stchur, Peter; Hou, Xiandeng; Yang, Karl X; Zhou, Jack; Michel, Robert G

    2005-12-01

    It has been shown that an increase in sensitivity and selectivity of detection of an analyte can be achieved by tuning the ablation laser wavelength to match that of a resonant gas-phase transition of that analyte. This has been termed resonant laser ablation (RLA). For a pulsed tunable nanosecond laser, the data presented here illustrate the resonant enhancement effect in pure copper and aluminum samples, chromium oxide thin films, and for trace molybdenum in stainless steel samples, and indicate two main characteristics of the RLA phenomenon. The first is that there is an increase in the number of atoms ablated from the surface. The second is that the bandwidth of the wavelength dependence of the ablation is on the order of 1 nm. The effect was found to be virtually identical whether the atoms were detected by use of a microwave-induced plasma with atomic emission detection, by an inductively coupled plasma with mass spectrometric detection, or by observation of the number of laser pulses required to penetrate through thin films. The data indicate that a distinct ablation laser wavelength dependence exists, probably initiated via resonant radiation trapping, and accompanied by collisional broadening. Desorption contributions through radiation trapping are substantiated by changes in crater morphology as a function of wavelength and by the relatively broad linewidth of the ablation laser wavelength scans, compared to gas-phase excitation spectra. Also, other experiments with thin films demonstrate the existence of a distinct laser-material interaction and suggest that a combination of desorption induced by electronic transition (DIET) with resonant radiation trapping could assist in the enhancement of desorption yields. These results were obtained by a detailed inspection of the effect of the wavelength of the ablation laser over a narrow range of energy densities that lie between the threshold of laser-induced desorption of species and the usual analytical

  15. Hybrid Carbon-Carbon Ablative Composites for Thermal Protection in Aerospace

    Directory of Open Access Journals (Sweden)

    P. Sanoj

    2014-01-01

    Full Text Available Composite materials have been steadily substituting metals and alloys due to their better thermomechanical properties. The successful application of composite materials for high temperature zones in aerospace applications has resulted in extensive exploration of cost effective ablative materials. High temperature heat shielding to body, be it external or internal, has become essential in the space vehicles. The heat shielding primarily protects the substrate material from external kinetic heating and the internal insulation protects the subsystems and helps to keep coefficient of thermal expansion low. The external temperature due to kinetic heating may increase to about maximum of 500°C for hypersonic reentry space vehicles while the combustion chamber temperatures in case of rocket and missile engines range between 2000°C and 3000°C. Composite materials of which carbon-carbon composites or the carbon allotropes are the most preferred material for heat shielding applications due to their exceptional chemical and thermal resistance.

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

    Science.gov (United States)

    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.

  17. Transonic ablation flow regimes of high-Z pellets

    CERN Document Server

    Kim, Hyoungkeun; Parks, Paul

    2015-01-01

    In this letter, we report results of numerical studies of the ablation of argon and neon pellets in tokamaks and compare them with theoretical predictions and studies of deuterium pellets. Results demonstrate the influence of atomic physics processes on the pellet ablation process.

  18. Radiofrequency ablation as initial therapy in paroxysmal atrial fibrillation

    DEFF Research Database (Denmark)

    Cosedis Nielsen, Jens; Johannessen, Arne; Raatikainen, Pekka;

    2012-01-01

    There are limited data comparing radiofrequency catheter ablation with antiarrhythmic drug therapy as first-line treatment in patients with paroxysmal atrial fibrillation.......There are limited data comparing radiofrequency catheter ablation with antiarrhythmic drug therapy as first-line treatment in patients with paroxysmal atrial fibrillation....

  19. Trowelable ablative coating composition and method of use

    Science.gov (United States)

    Headrick, Stephen E. (Inventor); Hill, Roger L. (Inventor)

    1989-01-01

    A trowelable ablative coating composition is disclosed. The composition comprises an epoxy resin, an amide curing agent, glass microspheres and ground cork. A method for protecting a substrate is also disclosed. The method comprises applying the trowelable ablative coating discussed above to a substrate and curing the coating composition.

  20. Percutaneous transluminal coronary rotary ablation with rotablator (European experience)

    NARCIS (Netherlands)

    M.E. Bertrand (Michel); J.M. Lablanche (Jean Marc); C. Bauters; P.P.T. de Jaegere (Peter); P.W.J.C. Serruys (Patrick); J. Meyer (Jurgen); U. Dietz; R. Erbel (Raimund)

    1992-01-01

    textabstractThis study reports the results from 3 European centers using rotary ablation with Rotablator, a device that is inserted into the coronary artery and removes atheroma by grinding it into millions of tiny fragments. Rotary ablation was performed in 129 patients. Primary success (reduction

  1. Ablation techniques for primary and metastatic liver tumors

    Institute of Scientific and Technical Information of China (English)

    2016-01-01

    Ablative treatment methods have emerged as safe and effective therapies for patients with primary andsecondary liver tumors who are not surgical candidatesat the time of diagnosis. This article reviews the currentliterature and describes the techniques, complicationsand results for radiofrequency ablation, microwaveablation, cryoablation, and irreversible electroporation.

  2. Low vulnerability of the right phrenic nerve to electroporation ablation

    NARCIS (Netherlands)

    van Driel, Vincent J. H. M.; Neven, KGEJ; van Wessel, Harri; Vink, Aryan; Doevendans, Pieter A. F. M.; Wittkampf, Fred H. M.

    2015-01-01

    BACKGROUND Circular electroporation ablation is a novel ablation modality for electrical pulmonary vein isolation. With a single 200-3 application, deep circular myocardial lesions can be created. However, the acute and chronic effects of this energy source on phrenic nerve (PN) function are unknown

  3. Fiber-Coupled Spectrometer for TPS Materials Project

    Data.gov (United States)

    National Aeronautics and Space Administration — EDA, Inc., in partnership with Penn State, has shown previously that the concept of embedding fiber optics within ablative TPS material has merit and should yield a...

  4. Laser ablative cutting of ceramics for electronics applications

    Energy Technology Data Exchange (ETDEWEB)

    Warner, B. E., LLNL

    1996-03-01

    Pulsed, high-beam quality lasers offer unique materials processing characteristics. In processing metals, copper vapor and pulsed Nd:YAG lasers have produced micron-scale cuts and holes with submicron heat-affected zones. Since the cost of laser photons is high and average material removal rates can be slow with ablation, high value-added applications are necessary to justify processing costs. Ceramics present a special challenge for manufacturing because of their high hardness, relatively low thermal conductivity, and brittle nature. Surface damage typically limits the strength of a ceramic part to a small fraction of its bulk strength. This work investigates the use of copper vapor and pulsed diode-pumped Nd:YAG lasers to cut precision features in ceramic substrates. Variations in laser wavelength and power, processing speed, ceramic type, and assist gas were investigated with the goal of producing <100-{mu}m wide by 600-{mu}m deep cuts through silicon-carbide and alumina/titanium-carbide substrates for potential use in electronics. Silicon-carbide bars 250-{mu}m wide by 600-{mu}m high by 2.5-cm long were laser cut from substrates without fracture.

  5. Dynamics of Laser Ablation in Superfluid ^4{He}

    Science.gov (United States)

    Buelna, X.; Popov, E.; Eloranta, J.

    2017-02-01

    Pulsed laser ablation of metal targets immersed in superfluid ^4{He} is visualized by time-resolved shadowgraph photography and the products are analyzed by post-experiment atomic force microscopy (AFM) measurements. The expansion dynamics of the gaseous ablation half-bubble on the target surface appears underdamped and follows the predicted behavior for the thermally induced bubble growth mechanism. An inherent instability of the ablation bubble appears near its maximum radius and no tightly focused cavity collapse or rebound events are observed. During the ablation bubble retreat phase, the presence of sharp edges in the target introduces flow patterns that lead to the creation of large classical vortex rings. Furthermore, on the nanometer scale, AFM data reveal that the metal nanoparticles created by laser ablation are trapped in spherical vortex tangles and quantized vortex rings present in the non-equilibrium liquid.

  6. Chemothermal Therapy for Localized Heating and Ablation of Tumor

    Directory of Open Access Journals (Sweden)

    Zhong-Shan Deng

    2013-01-01

    Full Text Available Chemothermal therapy is a new hyperthermia treatment on tumor using heat released from exothermic chemical reaction between the injected reactants and the diseased tissues. With the highly minimally invasive feature and localized heating performance, this method is expected to overcome the ubiquitous shortcomings encountered by many existing hyperthermia approaches in ablating irregular tumor. This review provides a relatively comprehensive review on the latest advancements and state of the art in chemothermal therapy. The basic principles and features of two typical chemothermal ablation strategies (acid-base neutralization-reaction-enabled thermal ablation and alkali-metal-enabled thermal/chemical ablation are illustrated. The prospects and possible challenges facing chemothermal ablation are analyzed. The chemothermal therapy is expected to open many clinical possibilities for precise tumor treatment in a minimally invasive way.

  7. Radiofrequency Ablation for Treatment of Symptomatic Uterine Fibroids

    Directory of Open Access Journals (Sweden)

    Siân Jones

    2012-01-01

    Full Text Available The use of thermal energy-based systems to treat uterine fibroids has resulted in a plethora of devices that are less invasive and potentially as effective in reducing symptoms as traditional options such as myomectomy. Most thermal ablation devices involve hyperthermia (heating of tissue, which entails the conversion of an external electromagnetic or ultrasound waves into intracellular mechanical energy, generating heat. What has emerged from two decades of peer-reviewed research is the concept that hyperthermic fibroid ablation, regardless of the thermal energy source, can create large areas of necrosis within fibroids resulting in reductions in fibroid volume, associated symptoms and the need for reintervention. When a greater percentage of a fibroid's volume is ablated, symptomatic relief is more pronounced, quality of life increases, and it is more likely that such improvements will be durable. We review radiofrequency ablation (RFA, one modality of hyperthermic fibroid ablation.

  8. Radiofrequency ablation of hepatic tumors: lessons learned from 3000 procedures.

    Science.gov (United States)

    Rhim, Hyunchul; Lim, Hyo K; Kim, Young-sum; Choi, Dongil; Lee, Won Jae

    2008-10-01

    Radiofrequency ablation has been accepted as the most popular local ablative therapy for unresectable malignant hepatic tumors. For 9 years from April 1999, we performed 3000 radiofrequency ablation procedures for hepatic tumors in our institution. Our results on the safety (mortality, 0.15%/patient) and therapeutic efficacy (5-year survival rate, 58%) are similar to those of previous studies reported, supporting the growing evidence of a clear survival benefit, excellent results for local tumor control and improved quality of life. The most important lesson learned from our 3000 procedures is that the best planning, safe ablation and complete ablation are key factors for patient outcome. Furthermore, multimodality treatment is the best strategy for recurrent hepatocellular carcinoma encountered after any kind of first-line treatment.

  9. Synthesis of Ag@Silica Nanoparticles by Assisted Laser Ablation

    Science.gov (United States)

    González-Castillo, Jr.; Rodriguez, E.; Jimenez-Villar, E.; Rodríguez, D.; Salomon-García, I.; de Sá, Gilberto F.; García-Fernández, T.; Almeida, DB; Cesar, CL; Johnes, R.; Ibarra, Juana C.

    2015-10-01

    This paper reports the synthesis of silver nanoparticles coated with porous silica (Ag@Silica NPs) using an assisted laser ablation method. This method is a chemical synthesis where one of the reagents (the reducer agent) is introduced in nanometer form by laser ablation of a solid target submerged in an aqueous solution. In a first step, a silicon wafer immersed in water solution was laser ablated for several minutes. Subsequently, an AgNO3 aliquot was added to the aqueous solution. The redox reaction between the silver ions and ablation products leads to a colloidal suspension of core-shell Ag@Silica NPs. The influence of the laser pulse energy, laser wavelength, ablation time, and Ag+ concentration on the size and optical properties of the Ag@Silica NPs was investigated. Furthermore, the colloidal suspensions were studied by UV-VIS-NIR spectroscopy, X-Ray diffraction, and high-resolution transmission electron microscopy (HRTEM).

  10. Computational modeling of ultra-short-pulse ablation of enamel

    Energy Technology Data Exchange (ETDEWEB)

    London, R.A.; Bailey, D.S.; Young, D.A. [and others

    1996-02-29

    A computational model for the ablation of tooth enamel by ultra-short laser pulses is presented. The role of simulations using this model in designing and understanding laser drilling systems is discussed. Pulses of duration 300 sec and intensity greater than 10{sup 12} W/cm{sup 2} are considered. Laser absorption proceeds via multi-photon initiated plasma mechanism. The hydrodynamic response is calculated with a finite difference method, using an equation of state constructed from thermodynamic functions including electronic, ion motion, and chemical binding terms. Results for the ablation efficiency are presented. An analytic model describing the ablation threshold and ablation depth is presented. Thermal coupling to the remaining tissue and long-time thermal conduction are calculated. Simulation results are compared to experimental measurements of the ablation efficiency. Desired improvements in the model are presented.

  11. Oestrogen sulfotransferase ablation sensitizes mice to sepsis.

    Science.gov (United States)

    Chai, Xiaojuan; Guo, Yan; Jiang, Mengxi; Hu, Bingfang; Li, Zhigang; Fan, Jie; Deng, Meihong; Billiar, Timothy R; Kucera, Heidi R; Gaikwad, Nilesh W; Xu, Meishu; Lu, Peipei; Yan, Jiong; Fu, Haiyan; Liu, Youhua; Yu, Lushan; Huang, Min; Zeng, Su; Xie, Wen

    2015-08-10

    Sepsis is the host's deleterious systemic inflammatory response to microbial infections. Here we report an essential role for the oestrogen sulfotransferase (EST or SULT1E1), a conjugating enzyme that sulfonates and deactivates estrogens, in sepsis response. Both the caecal ligation and puncture (CLP) and lipopolysaccharide models of sepsis induce the expression of EST and compromise the activity of oestrogen, an anti-inflammatory hormone. Surprisingly, EST ablation sensitizes mice to sepsis-induced death. Mechanistically, EST ablation attenuates sepsis-induced inflammatory responses due to compromised oestrogen deactivation, leading to increased sepsis lethality. In contrast, transgenic overexpression of EST promotes oestrogen deactivation and sensitizes mice to CLP-induced inflammatory response. The induction of EST by sepsis is NF-κB dependent and EST is a NF-κB-target gene. The reciprocal regulation of inflammation and EST may represent a yet-to-be-explored mechanism of endocrine regulation of inflammation, which has an impact on the clinical outcome of sepsis.

  12. CT Guided Laser Ablation of Osteoid Osteoma

    Directory of Open Access Journals (Sweden)

    Manohar Kachare

    2015-10-01

    Full Text Available To present our experience of Computed Tomography (CT guided laser ablation of radiologically proven osteoid osteoma in the inter trochantric region of the femur. A19 year old female presented with severe pain in left upper thigh region since 6-7 months, which was exaggerated during nights and was relived on taking oral Non Steroid Anti Inflammatory Drugs (NSAIDs. On CT scan hypodense lesion with surrounding dense sclerosis noted in intertrochanteric region in left femur. Magnetic Resonance Imaging (MRI revealed small focal predominantly cortical, oval lytic lesion in the intertrochanteric region which appeared hypointense on T1 Weighted Image (T1WI and hyperintense on T2 Weighted Image (T2WI and Short Tau Inversion Recovery (STIR image. Diffuse extensive sclerosis and hyperostosis of bone was noted surrounding the lesion appearing hypointense on T1W and T2W images. Under local anesthesia the laser fibre was inserted in the nidus under CT guidance through bone biopsy needle and 1800 joules energy delivered in the lesion continuous mode. Complete relief of pain noted after 24 hours after the treatment. CT guided LASER ablation is a safe, simple and effective method of treatment for osteoid osteoma.

  13. Real-time ablation measurements on erosion of silicone rubber and EPDM material by highly concentrated particles%高浓度颗粒流冲刷条件下硅橡胶和EPDM绝热材料动态烧蚀实验

    Institute of Scientific and Technical Information of China (English)

    张胜敏; 胡春波; 夏盛勇; 孙翔宇; 胡淑芳

    2011-01-01

    利用X射线实时诊断技术(RTR)针对硅橡胶和EPDM绝热材料,开展了高浓度颗粒流冲刷条件下动态烧蚀实验研究,成功获得了绝热材料烧蚀表面退移过程的序列图像.研究表明:(1)在本实验条件下,硅橡胶绝热材料颗粒冲刷区域的瞬时烧蚀率在0-2,内迅速增加,2s之后瞬时烧蚀率略有下降并趋于稳定;EPDM绝热材料颗粒冲刷区域的瞬时烧蚀率在0~1s内迅速增加,1s之后瞬时烧蚀率趋于稳定;(2)相同冲刷条件下硅橡胶绝热材料抗颗粒流冲刷性能比EPDM绝热材料差,硅橡胶绝热材料不适合在高过载发动机中应用;(3)高浓度颗粒流冲刷条件下绝热材料的烧蚀率比常规条件下要严重的多,其机理主要是高温颗粒流对炭化层有强烈的机械剥蚀效应和热化学烧蚀作用.实验结果对硅橡胶和EPDM绝热材料烧蚀机理研究及烧蚀建模具有重要参考价值.%The experimental study of the silicone rubber and EPDM insulator eroded by highly concentrated particles were carried out and a series of dynamic recession images of insulation surface were obtained successfully based on real-time X-ray radiography technique(RTR). The experimental results show that( 1 )The transient ablation rate of silicone rubber increased rapidly within the first two seconds and it would become stable after two seconds. The transient ablation rate of EPDM increased rapidly within the first second and then it would become stable. (2) The results indicate that the characteristic of resistant to erosion of particles of EPDM insulator is better than that of silicone rubber. Silicone rubber insulation is not suitable for the application of high overload motor. ( 3 ) The ablation rate of insulation eroded by highly concentrated particles is higher than that in normal condition. The mechanism is that the insulation is eroded by both mechanical abrasion and thermochemical ablation due to high-temperature particles. The results are

  14. Post-Ablation Endometrial Carcinoma (PAEC) Following Radiofrequency Endometrial Ablation: A Case Report and Its Implications for Management of Endometrial Ablation Failures.

    Science.gov (United States)

    Wortman, Morris; Dawkins, Josette C

    2016-10-26

    Endometrial ablation (EA) has become one of the most commonly performed gynecologic procedures in the United States and other developed countries. Global endometrial ablation (GEA) devices have supplanted resectoscopic ablation primarily because they have brought with them technical simplicity and unprecedented safety. These devices, all of which received FDA approval between 1997 and 2001, are typically used to treat abnormal uterine bleeding (AUB) in premenopausal women. Several million women in the US who have undergone a previous EA procedure are about to enter the risk pool for the development of endometrial cancer (EC). Ours is the 18th reported case of post-ablation endometrial carcinoma (PAEC) in the English literature. This case underscores the diagnostic challenges faced in evaluating women with a history of a previous EA who cannot be properly evaluated with conventional techniques such as endometrial biopsy and sonohysterography.

  15. Modeling of plasma distortions by laser-induced ablation spectroscopy (LIAS) and implications for the interpretation of LIAS measurements

    Science.gov (United States)

    Tokar, M. Z.; Gierse, N.; Philipps, V.; Samm, U.

    2015-09-01

    For the interpretation of the line radiation observed from laser induced ablation spectroscopy (LIAS) such parameters as the density and temperature of electrons within very compact clouds of atoms and singly charged ions of ablated material have to be known. Compared to the local plasma conditions prior to the laser pulse, these can be strongly changed during LIAS since new electrons are generated by the ionisation of particles ejected from the irradiated target. Because of their transience and spatial inhomogeneity it is technically difficult to measure disturbances induced in the plasma by LIAS. To overcome this uncertainty a numerical model has been elaborated, providing a self-consistent description for the spreading of ablated particles and accompanying modifications in the plasma. The results of calculations for LIAS performed on carbon-containing targets in Ohmic and additionally heated discharges in the tokamak TEXTOR are presented. Due to the increase in the electron density the ‘ionisation per photon’ ratio, S/XB factor, is significantly enhanced compared to unperturbed plasma conditions. The impact of the amount of material ablated and of the plasma conditions before LIAS on the level of the S/XB-enhancement is investigated.

  16. Direct investigation of the ablation rate evolution during laser drilling of high-aspect-ratio micro-holes

    Science.gov (United States)

    Mezzapesa, Francesco P.; Sibillano, Teresa; Columbo, Lorenzo L.; Di Niso, Francesca; Ancona, Antonio; Dabbicco, Maurizio; De Lucia, Francesco; Lugarà, Pietro M.; Scamarcio, Gaetano

    2012-03-01

    The recent development of ultrafast laser ablation technology in precision micromachining has dramatically increased the demand for reliable and real-time detection systems to characterize the material removal process. In particular, the laser percussion drilling of metals is lacking of non-invasive techniques able to monitor into the depth the spatial- and time-dependent evolution all through the ablation process. To understand the physical interaction between bulk material and high-energy light beam, accurate in-situ measurements of process parameters such as the penetration depth and the removal rate are crucial. We report on direct real time measurements of the ablation front displacement and the removal rate during ultrafast laser percussion drilling of metals by implementing a contactless sensing technique based on optical feedback interferometry. High aspect ratio micro-holes were drilled onto steel plates with different thermal properties (AISI 1095 and AISI 301) and Aluminum samples using 120-ps/110-kHz pulses delivered by a microchip laser fiber amplifier. Percussion drilling experiments have been performed by coaxially aligning the diode laser probe beam with the ablating laser. The displacement of the penetration front was instantaneously measured during the process with a resolution of 0.41 μm by analyzing the sawtooth-like induced modulation of the interferometric signal out of the detector system.

  17. Determinations of rare earth element abundance and U-Pb age of zircons using multispot laser ablation-inductively coupled plasma mass spectrometry.

    Science.gov (United States)

    Yokoyama, Takaomi D; Suzuki, Toshihiro; Kon, Yoshiaki; Hirata, Takafumi

    2011-12-01

    We have developed a new calibration technique for multielement determination and U-Pb dating of zircon samples using laser ablation-inductively coupled plasma mass spectrometry (ICPMS) coupled with galvanometric optics. With the galvanometric optics, laser ablation of two or more sample materials could be achieved in very short time intervals (~10 ms). The resulting sample aerosols released from different ablation pits or different solid samples were mixed and homogenized within the sample cell and then transported into the ICP ion source. Multiple spot laser ablation enables spiking of analytes or internal standard elements directly into the solid samples, and therefore the standard addition calibration method can be applied for the determination of trace elements in solid samples. In this study, we have measured the rare earth element (REE) abundances of two zircon samples (Nancy 91500 and Prešovice) based on the standard addition technique, using a direct spiking of analytes through a multispot laser ablation of the glass standard material (NIST SRM612). The resulting REE abundance data show good agreement with previously reported values within analytical uncertainties achieved in this study (10% for most elements). Our experiments demonstrated that nonspectroscopic interferences on 14 REEs could be significantly reduced by the standard addition technique employed here. Another advantage of galvanometric devices is the accumulation of sample aerosol released from multiple spots. In this study we have measured the U-Pb age of a zircon sample (LMR) using an accumulation of sample aerosols released from 10 separate ablation pits of low diameters (~8 μm). The resulting (238)U-(206)Pb age data for the LMR zircons was 369 ± 64 Ma, which is in good agreement with previously reported age data (367.6 ± 1.5 Ma). (1) The data obtained here clearly demonstrate that the multiple spot laser ablation-ICPMS technique can become a powerful approach for elemental and isotopic

  18. Ultrasonography-guided percutaneous radiofrequency ablation of hepatocellular carcinomas: A feasibility scoring system for planning sonography

    Energy Technology Data Exchange (ETDEWEB)

    Rhim, Hyunchul, E-mail: rhimhc@skku.ed [Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of); Choi, Dongil; Kim, Young-sun; Lim, Hyo K. [Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul (Korea, Republic of); Choe, Bong-Keun [Department of Preventive Medicine, Kyung Hee University School of Medicine, Seoul (Korea, Republic of)

    2010-08-15

    Purpose: This study was designed to evaluate whether a feasibility scoring system for planning sonography is a reliable predictor of a safe and complete ablation in ultrasonography (US)-guided percutaneous radiofrequency ablation (RFA) of hepatocellular carcinomas (HCCs). Materials and methods: We retrospectively evaluated the therapeutic outcomes of 108 consecutive patients (M:F, 78:30; mean age, 57.4 years) with a single nodular HCC (mean diameter, 2.0 cm) treated by percutaneous RFA. All patients were assessed for the feasibility of performing an RFA at planning sonography prior to the ablation. The feasibility scoring system consisted of five categories: the safe electrode path (P); the vital organs adjacent to the RFA zone (O); tumor size (S); tumor conspicuity (C); and the heat-sink effect (H). Each category was divided into a four-point scale [1-4]. If a score of 4 in any category was determined, the patient was not considered to be a suitable candidate for percutaneous RFA. We assessed if the score of each category, safety score (P + O), and curability score (S + C + H) correlated with a safe and complete ablation using the chi-squared test and likelihood ratio test for trend. Results: The technical success rate was 100% (108/108) based on CT images obtained immediately after ablation. There was no 30-day mortality after RFA. There were major complications (one case of severe vasovagal reflex, one case of hemoperitoneum and one case of a pseudoaneurysm) in three (2.7%) patients, and minor complications (one case of a biloma, one case of subsegmental infarction and one case of abscess) in three (2.7%) patients. Post-ablation syndrome as a side effect was noted in 38 (35.1%) of 108 patients. The primary technique effectiveness rate at 1 month was 95.1% (105/108). Local tumor progression was noted in eight (7.6%) of 105 patients during the follow-up period (range, 3.0-11.5 months; median, 5.8 months; mean, 5.7 months). There was no significant single category

  19. Fast femtosecond laser ablation for efficient cutting of sintered alumina substrates

    Science.gov (United States)

    Oosterbeek, Reece N.; Ward, Thomas; Ashforth, Simon; Bodley, Owen; Rodda, Andrew E.; Simpson, M. Cather

    2016-09-01

    Fast, accurate cutting of technical ceramics is a significant technological challenge because of these materials' typical high mechanical strength and thermal resistance. Femtosecond pulsed lasers offer significant promise for meeting this challenge. Femtosecond pulses can machine nearly any material with small kerf and little to no collateral damage to the surrounding material. The main drawback to femtosecond laser machining of ceramics is slow processing speed. In this work we report on the improvement of femtosecond laser cutting of sintered alumina substrates through optimisation of laser processing parameters. The femtosecond laser ablation thresholds for sintered alumina were measured using the diagonal scan method. Incubation effects were found to fit a defect accumulation model, with Fth,1=6.0 J/cm2 (±0.3) and Fth,∞=2.5 J/cm2 (±0.2). The focal length and depth, laser power, number of passes, and material translation speed were optimised for ablation speed and high quality. Optimal conditions of 500 mW power, 100 mm focal length, 2000 μm/s material translation speed, with 14 passes, produced complete cutting of the alumina substrate at an overall processing speed of 143 μm/s - more than 4 times faster than the maximum reported overall processing speed previously achieved by Wang et al. [1]. This process significantly increases processing speeds of alumina substrates, thereby reducing costs, making femtosecond laser machining a more viable option for industrial users.

  20. PLASMA-OXYGEN INTERACTION DURING THIN FILMS DEPOSITION BY LASER ABLATION: DETERMINATION OF THE INTERACTION PRESSURE THRESHOLD AND EFFECT ON THE THIN FILMS PROPERTIESE

    Directory of Open Access Journals (Sweden)

    S. Lafane

    2015-07-01

    Full Text Available In this contribution we study the effect of the oxygen pressure on the plasma dynamics during the ablation of oxides materials into an oxygen gas. The study was done using fast imaging and ion probe techniques. Both techniques revealed that a threshold oxygen pressure is needed to initiate the plume oxygen interaction. This threshold oxygen pressure depends on the ablated material. A clear effect of this threshold pressure on the structural and phase composition of the deposited thin films is shown.

  1. Transarterial ablation of hepatocellular carcinoma. Status and developments; Transvaskulaere Ablation des hepatozellulaeren Karzinoms. Ist Chemotherapie alles

    Energy Technology Data Exchange (ETDEWEB)

    Radeleff, B.A.; Stampfl, U.; Sommer, C.M.; Bellemann, N.; Kauczor, H.U. [Universitaetsklinikum Heidelberg, Abt. Diagnostische und Interventionelle Radiologie, Radiologische Klinik, Heidelberg (Germany); Hoffmann, K. [Universitaetsklinikum Heidelberg, Abt. fuer Allgemein-, Viszeral- und Transplantationschirurgie, Chirurgische Klinik, Heidelberg (Germany); Ganten, T.; Ehehalt, R. [Universitaetsklinikum Heidelberg, Medizinische Klinik IV, Gastroenterologie, Infektionskrankheiten, Vergiftungen, Heidelberg (Germany)

    2012-01-15

    Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide and represents the main cause of death among European patients with liver cirrhosis. Only 30-40% of patients diagnosed with HCC are candidates for curative treatment options (e.g. surgical resection, liver transplantation or ablation). The remaining majority of patients must undergo local regional and palliative therapies. Transvascular ablation of HCC takes advantage of the fact that the hypervascularized HCC receives most of its blood supply from the hepatic artery. In this context transvascular ablation describes different therapy regimens which can be assigned to four groups: cTACE (conventional transarterial chemoembolization), bland embolization (transarterial embolization TAE), DEB-TACE (TACE with drug-eluting beads, DEB) and SIRT (selective internal radiation therapy, radioembolization). Conventional TACE is the most common type of transvascular ablation and represents a combination of intra-arterial chemotherapy and embolization with occlusion of the arterial blood supply. However, there is no standardized regimen with respect to the chemotherapeutic drug, the embolic agent, the usage of lipiodol and the interval between the TACE procedures. Even the exact course of a cTACE procedure (order of chemotherapy or embolization) is not standardized. It remains unclear whether or not intra-arterial chemotherapy is definitely required as bland embolization using very small, tightly calibrated spherical particles (without intra-arterial administration of a chemotherapeutic drug) shows tumor necrosis comparable to cTACE. For DEB-TACE microparticles loaded with a chemotherapeutic drug combine the advantages of cTACE and bland embolization. Thereby, a continuing chemotherapeutic effect within the tumor might cause a further increase in intratumoral cytotoxicity and at the same time a decrease in systemic toxicity. (orig.) [German] Das hepatozellulaere Karzinom (HCC) ist weltweit betrachtet das

  2. SOLID BODY ABLATION UNDER EXPOSURE TO ULTRA SHORT LASER PULSES: STUDY BY MOLECULAR DYNAMICS METHODS

    Directory of Open Access Journals (Sweden)

    D. S. Ivanov

    2014-09-01

    Full Text Available The process of laser ablation under the influence of ultra short laser pulses on metals is investigated by methods of molecular dynamics. The validity and applicability of the hybrid atomistic-continuous model for the estimation of optimum modes of ultra short laser pulses processing are explored. Combination of atomistic model of laser-induced non-equilibrium process of a phase transition at the atomic level with continuous two-temperature model for describing the dynamics of photo-excitation of free media is proposed. Applicability of laser ablation model on the example of aluminum films and gold under exposure to pulses with different energy density and duration is shown. It is indicated that, depending on the ratio of the laser pulse duration and the characteristic time of electron-phonon material interaction, photothermal and photomechanical modes of destruction are implemented that determine the quality and performance of the laser processing. It is established that at the duration of laser pulse less than the time of electron-phonon interaction high-performance photomechanical type of destruction is implemented by internal stresses arising in the area of exposure. This is confirmed by a linear dependence of the ablation rate from the absorbed energy. At the duration of laser pulse greater than the time of electron-phonon interaction inefficient photothermal mode of destruction is implemented. The results may be useful for specialists engaged in the development of laser technologies

  3. Stark broadening measurements in plasmas produced by laser ablation of hydrogen containing compounds

    Science.gov (United States)

    Burger, Miloš; Hermann, Jörg

    2016-08-01

    We present a method for the measurement of Stark broadening parameters of atomic and ionic spectral lines based on laser ablation of hydrogen containing compounds. Therefore, plume emission spectra, recorded with an echelle spectrometer coupled to a gated detector, were compared to the spectral radiance of a plasma in local thermal equilibrium. Producing material ablation with ultraviolet nanosecond laser pulses in argon at near atmospheric pressure, the recordings take advantage of the spatially uniform distributions of electron density and temperature within the ablated vapor. By changing the delay between laser pulse and detector gate, the electron density could be varied by more than two orders of magnitude while the temperature was altered in the range from 6,000 to 14,000 K. The Stark broadening parameters of transitions were derived from their simultaneous observation with the hydrogen Balmer alpha line. In addition, assuming a linear increase of Stark widths and shifts with electron density for non-hydrogenic lines, our measurements indicate a change of the Stark broadening-dependence of Hα over the considered electron density range. The presented results obtained for hydrated calcium sulfate (CaSO4ṡ2H2O) can be extended to any kind of hydrogen containing compounds.

  4. Selective removal of esthetic composite restorations with spectral guided laser ablation

    Science.gov (United States)

    Yi, Ivana; Chan, Kenneth H.; Tsuji, Grant H.; Staninec, Michal; Darling, Cynthia L.; Fried, Daniel

    2016-02-01

    Dental composites are used for a wide range of applications such as fillings for cavities, adhesives for orthodontic brackets, and closure of gaps (diastemas) between teeth by esthetic bonding. Anterior restorations are used to replace missing, diseased and unsightly tooth structure for both appearance and function. When these restorations must be replaced, they are difficult to remove mechanically without causing excessive removal or damage to enamel because dental composites are color matched to teeth. Previous studies have shown that CO2 lasers have high ablation selectivity and are well suited for removal of composite on occlusal surfaces while minimizing healthy tissue loss. A spectral feedback guidance system may be used to discriminate between dental composite and dental hard tissue for selective ablation of composite material. The removal of composite restorations filling diastemas is more challenging due to the esthetic concern for anterior teeth. The objective of this study is to determine if composite spanning a diastema between anterior teeth can be removed by spectral guided laser ablation at clinically relevant rates with minimal damage to peripheral healthy tissue and with higher selectivity than a high speed dental handpiece.

  5. Postinterventional MRI findings following MRI-guided laser ablation of osteoid osteoma

    Energy Technology Data Exchange (ETDEWEB)

    Fuchs, S., E-mail: simon.fuchs@charite.de [Department of Radiology, Charité, Humboldt University, Berlin (Germany); Gebauer, B.; Stelter, L.; Schäfer, M.L.; Renz, D.M. [Department of Radiology, Charité, Humboldt University, Berlin (Germany); Melcher, I.; Schaser, K. [Center for Musculoskeletal Surgery, Charité, Humboldt University, Berlin (Germany); Hamm, B.; Streitparth, F. [Department of Radiology, Charité, Humboldt University, Berlin (Germany)

    2014-04-15

    Objective: To evaluate postinterventional magnetic resonance imaging (MRI) characteristics following MRI-guided laser ablation of osteoid osteoma (OO). Materials and methods: 35 patients treated with MRI-guided laser ablation underwent follow-up MRI immediately after the procedure, after 3, 6, 12, 24, 36, and up to 48 months. The imaging protocol included multiplanar fat-saturated T2w TSE, unenhanced and contrast-enhanced T1w SE, and subtraction images. MR images were reviewed regarding the appearance and size of treated areas, and presence of periablation bone and soft tissue changes. Imaging was correlated with clinical status. Results: Mean follow-up time was 13.6 months. 28/35 patients (80%) showed a postinterventional “target-sign” appearance consisting of a fibrovascular rim zone and a necrotic core area. After an initial increase in total lesion diameter after 3 months, a subsequent progressive inward remodeling process of the zonal compartments was observed for up to 24 months. Periablation bone and soft tissue changes showed a constant decrease over time. MR findings correlated well with the clinical status. Clinical success was achieved in 32/35 (91%). Conclusions: Evaluation of long-term follow-up MRI after laser ablation of OO identified typical postinterventional changes and thus may contribute to the interpretation of therapeutic success and residual or recurrent OO in suspected cases.

  6. Selective removal of esthetic composite restorations with spectral guided laser ablation.

    Science.gov (United States)

    Yi, Ivana; Chan, Kenneth H; Tsuji, Grant H; Staninec, Michal; Darling, Cynthia L; Fried, Daniel

    2016-02-13

    Dental composites are used for a wide range of applications such as fillings for cavities, adhesives for orthodontic brackets, and closure of gaps (diastemas) between teeth by esthetic bonding. Anterior restorations are used to replace missing, diseased and unsightly tooth structure for both appearance and function. When these restorations must be replaced, they are difficult to remove mechanically without causing excessive removal or damage to enamel because dental composites are color matched to teeth. Previous studies have shown that CO2 lasers have high ablation selectivity and are well suited for removal of composite on occlusal surfaces while minimizing healthy tissue loss. A spectral feedback guidance system may be used to discriminate between dental composite and dental hard tissue for selective ablation of composite material. The removal of composite restorations filling diastemas is more challenging due to the esthetic concern for anterior teeth. The objective of this study is to determine if composite spanning a diastema between anterior teeth can be removed by spectral guided laser ablation at clinically relevant rates with minimal damage to peripheral healthy tissue and with higher selectivity than a high speed dental hand-piece.

  7. Photothermal ablation is the primary mechanism in holmium:YAG laser lithotripsy of urinary calculi

    Science.gov (United States)

    Glickman, Randolph D.; Teichman, Joel M. H.; Corbin, Nicole S.; Vassar, George J.; Weintraub, Susan T.; Chan, Kin Foong; Welch, Ashley J.

    1999-09-01

    Because of the >= 250 microsecond(s) pulsewidth emitted by the Ho:YAG laser used in clinical lithotripsy, it is unlikely that stress confinement occurs within the irradiated stones. Experimental data supports a thermal mechanism for Ho:YAG laser stone ablation. Previous work has shown that stone fragmentation occurs soon after the onset of the laser pulse, is uncorrelated to cavitation bubble formation or collapse, and is associated with low pressures. Moreover, lithotripsy proceeds fastest with desiccated stones in air (data based on laser ablation of calcium oxalate monohydrate stones), indicating that direct absorption of the laser radiation by the stone material is required for the most efficient ablation. Lowering the initial temperature of calculi reduces the stone mass-loss following 20 J of delivered laser energy: 2.2 +/- 1.1 mg vs 5.2 +/- 1.6 mg for calcium oxalate monohydrate (COM) stones (-80 vs 23 degree(s)C), and 0.8 +/- 0.4 mg vs 2.2 +/- 1.1 mg for cystine stones (-80 vs 23 degree(s)C), p cystine; Ca2O7P2 from calcium hydrogen phosphate dihydrate, and cyanide and alloxan from uric acid. All of these observations are most consistent with a photothermal breakdown process induced by Ho:YAG laser lithotripsy.

  8. Effect of carbon dioxide laser ablation followed by intralesional steroids on keloids

    Directory of Open Access Journals (Sweden)

    Gaurav A Garg

    2011-01-01

    Full Text Available Abstract : Keloid is a difficult-to-treat condition and an ideal treatment modality is not available. Carbon dioxide (CO 2 laser is one of the modalities to treat keloids. Aim : To evaluate the effect of CO 2 laser ablation followed by intralesional steroids on keloids. Settings and Design : This was a prospective, single-center, uncontrolled, open study. Materials and Methods : Twenty-eight patients having 35 keloids were included in the study. Keloids were ablated or excised with CO 2 laser followed by intralesional steroid 3-4 weeks apart for 6 months. Results were evaluated after 6 months of stopping of intralesional steroids. Statistical Analysis : Fisher′s exact test was applied for obtaining difference in recurrence rate of regular and irregular patients. Results : Thirteen patients followed up regularly for intralesional steroids. During 6 months of follow-up after stoppage of steroids, only two patients showed recurrence. Ten patients were irregular for intralesional steroids and seven of them showed recurrence. Difference in recurrence rate of regular and irregular patients was significant. Conclusion : Only CO 2 laser ablation is not sufficient for halting the pathogenesis of keloid formation.We therefore conclude that CO 2 laser followed by intralesional steroid is a useful therapeutic approach for the treatment of keloids; however, patients need to be observed for recurrence over the next 1 year.

  9. Target-plane deposition of diamond-like carbon in pulsed laser ablation of graphite

    Energy Technology Data Exchange (ETDEWEB)

    Yap, S.S. [Faculty of Engineering, Multimedia University, 63100 Cyberjaya, Selangor (Malaysia); Tou, T.Y. [Faculty of Engineering, Multimedia University, 63100 Cyberjaya, Selangor (Malaysia)], E-mail: tytou@mmu.edu.my

    2007-10-15

    In pulsed Nd:YAG laser ablation of highly oriented pyrolytic graphite (HOPG) at 10{sup -6} Torr, diamond-like carbon (DLC) are deposited at laser wavelengths of 1064, 532, and 355 nm on substrates placed in the target-plane. These target-plane samples are found to contain varying sp{sup 3} content and composed of nanostructures of 40-200 nm in size depending on the laser wavelength and laser fluence. The material and origin of sp{sup 3} in the target-plane samples is closely correlated to that in the laser-modified HOPG surface layer, and hardly from the backward deposition of ablated carbon plume. The surface morphology of the target-plane samples shows the columnar growth and with a tendency for agglomeration between nanograins, in particular for long laser wavelength at 1064 nm. It is also proposed that DLC formation mechanism at the laser-ablated HOPG is possibly via the laser-induced subsurface melting and resolidification.

  10. Safety and feasibility of radiofrequency ablation for treatment of Bosniak IV renal cysts

    Science.gov (United States)

    de Menezes, Marcos Roberto; Viana, Publio Cesar Cavalcante; Yamanari, Tássia Regina; Reis, Leonardo Oliveira; Nahas, William

    2016-01-01

    ABSTRACT Purpose To describe our initial experience with radiofrequency ablation (RFA) of Bosniak IV renal cysts. Materials and Methods From 2010 to 2014, 154 renal tumor cases were treated with percutaneous thermal ablation, of which 10 cases (6.4%) from nine patients were complex renal cysts and were treated with radiofrequency ablation. Results All complex cysts were classified as Bosniak IV (four women and five men; mean age: 63.6 yrs, range: 33–83 years). One patient had a single kidney. Lesion size ranged from 1.5 to 4.1cm (mean: 2.5cm) and biopsy was performed on four cysts immediately before the procedure, all of which were malignant (two clear cell and two papillary carcinoma). Mean volume reduction of complex cysts was 25% (range: 10–40%). No patients required retreatment with RFA and no immediate or late complications were observed. The follow-up of Bosniak IV cysts had a median of 27 months (interquartile range [IQR], 23 to 38) and no recurrence or significant loss of renal function were observed. Conclusions Mid-term follow-up of the cases in our database suggests that image-guided percutaneous RFA can treat Bosniak IV cysts with very low complication rates and satisfactorily maintain renal function. PMID:27286107

  11. Percutaneous radiofrequency ablation of osteoid osteomas. Technique and results; Perkutane Radiofrequenzablation von Osteoidosteomen. Technik und Ergebnisse

    Energy Technology Data Exchange (ETDEWEB)

    Bruners, P.; Penzkofer, T. [Lehrstuhl fuer Angewandte Medizintechnik, Helmholtz Inst. fuer Biomedizinische Technik, RWTH Aachen (Germany); Guenther, R. W.; Mahnken, A. [Klinik fuer Radiologische Diagnostik, Universitaetsklinikum RWTH Aachen (Germany)

    2009-08-15

    Purpose: Osteoid osteoma is a benign primary bone tumor that typically occurs in children and young adults. Besides local pain, which is often worse at night, prompt relief due to medication with acetylsalicylic acid (ASS) is characteristic for this bone lesion. Because long-term medication with ASS does not represent an alternative treatment strategy due to its potentially severe side effects, different minimally invasive image-guided techniques for the therapy of osteoid osteoma have been developed. In this context radiofrequency (RF) ablation in particular has become part of the clinical routine. The technique and results of image-guided RF ablation are compared to alternative treatment strategies. Materials and Methods: Using this technique, an often needle-shaped RF applicator is percutaneously placed into the tumor under image guidance. Then a high-frequency alternating current is applied by the tip of the applicator which leads to ionic motion within the tissue resulting in local heat development and thus in thermal destruction of the surrounding tissue including the tumor. Results: The published primary and secondary success rates of this technique are 87 and 83%, respectively. Surgical resection and open curettage show comparable success rates but are associated with higher complication rates. In addition image-guided RF ablation of osteoid osteomas is associated with low costs. (orig.)

  12. Laser ablated coupling structures for stacked optical interconnections on printed circuit boards

    Science.gov (United States)

    Hendrickx, Nina; Van Steenberge, Geert; Geerinck, Peter; Van Erps, Jürgen; Thienpont, Hugo; Van Daele, Peter

    2006-04-01

    Laser ablation is presented as a versatile technology that can be used for the definition of arrays of multimode waveguides and coupling structures in a stacked two layer optical structure, integrated on a printed circuit board (PCB). The optical material, Truemode Backplane TM Polymer, is fully compatible with standard PCB manufacturing and shows excellent ablation properties. A KrF excimer laser is used for the ablation of both waveguides and coupling structures into the optical layer. The stacking of individual optical layers containing waveguides, that guide the light in the plane of the optical layer, and coupling structures, that provide out-of-plane coupling and coupling between different optical layers, is very interesting since it allows us to increase the integration density and routing possibilities and limit the number of passive components that imply a certain loss. Experimental results are presented, and surface roughness and profile measurements are performed on the structured elements for further characterization. Numerical simulations are presented on the tolerance on the angle of the coupling structures and the influence of tapering on the coupling efficiency of the waveguides.

  13. [Anesthetic consideration in patients undergoing catheter ablation for atrial fibrillation].

    Science.gov (United States)

    Oda, Toshiyuki; Takahama, Yutaka

    2012-11-01

    This chapter describes anesthetic consideration in patients undergoing catheter ablation for atrial fibrillation (AF) based on electrophysiologic or pharmacological aspects. In the 2011 guidelines of the Japanese Circulation Society for non-pharmacotherapy of cardiac arrhythmias, catheter ablation is recommended as Class I therapeutic modality for the patients with drug-refractory paroxysmal AF. Catheter ablation of AF is an invasive and long-lasting procedure necessitating sedation during treatment. However, in the most of the patients, sedation or anesthesia is possibly performed by cardiologists using propofol, midazolam or dexmedetomidine. Deep sedation accompanies a high risk of ventilatory or circulatory derangement. Furthermore, life-threatening complications, such as cerebral infarction or cardiac tamponade, can occur during ablation. Patients with AF are increasing in number as a trend in the aging society, resulting in an increase in catheter ablation in high risk patients. To accomplish safe anesthetic management of the patients for catheter ablations, anesthesiologists are required to have fundamental knowledge and skill in the performance of the catheter ablation.

  14. Actual role of radiofrequency ablation of liver metastases

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Philippe L. [Eberhard-Karls-University of Tuebingen, Department of Diagnostic Radiology, Tuebingen (Germany)

    2007-08-15

    The liver is, second only to lymph nodes, the most common site for metastatic disease irrespective of the primary tumour. More than 50% of all patients with malignant diseases will develop liver metastases with a significant morbidity and mortality. Although the surgical resection leads to an improved survival in patients with colorectal metastases, only approximately 20% of patients are eligible for surgery. Thermal ablation and especially radiofrequency ablation emerge as an important additional therapy modality for the treatment of liver metastases. RF ablation shows a benefit in life expectancy and may lead in a selected patient group to cure. Percutaneous RF ablation appears safer (versus cryotherapy), easier (versus laser), and more effective (versus ethanol instillation and transarterial chemoembolisation) compared with other minimally invasive procedures. RF ablation can be performed by a percutaneous, laparoscopical or laparotomic approach, and may be potentially combined with chemotherapy and surgery. At present ideal candidates have tumours with a maximum diameter less than 3.5 cm. An untreatable primary tumour or a systemic disease represents contraindications for performing local therapies. Permanent technical improvements of thermal ablation devices and a better integration of thermal ablation in the overall patient care may lead to prognosis improvement in patients with liver metastases. (orig.)

  15. LAPAROSCOPIC NEPHRECTOMY USING RADIOFREQUENCY THERMAL ABLATION

    Directory of Open Access Journals (Sweden)

    B. Ya. Alekseev

    2012-01-01

    Full Text Available The wide use of current diagnostic techniques, such as ultrasound study, computed tomography, and magnetic resonance imaging, has led to significantly increased detection rates for disease in its early stages. This gave rise to a change in the standards for the treatment of locally advanced renal cell carcinoma (RCC. Laparoscopic nephrectomy (LN has recently become the standard treatment of locally advanced RCC in the clinics having much experience with laparoscopic surgery. The chief drawback of LN is difficulties in maintaining intraoperative hemostasis and a need for creating renal tissue ischemia. The paper gives the intermediate results of application of the new procedure of LN using radiofrequency thermal ablation in patients with non-ischemic early-stage RCC.

  16. Emerging indications of endoscopic radiofrequency ablation

    Science.gov (United States)

    Becq, Aymeric; Camus, Marine; Rahmi, Gabriel; de Parades, Vincent; Marteau, Philippe

    2015-01-01

    Introduction Radiofrequency ablation (RFA) is a well-validated treatment of dysplastic Barrett's esophagus. Other indications of endoscopic RFA are under evaluation. Results Four prospective studies (total 69 patients) have shown that RFA achieved complete remission of early esophageal squamous intra-epithelial neoplasia at a rate of 80%, but with a substantial risk of stricture. In the setting of gastric antral vascular ectasia, two prospective monocenter studies, and a retrospective multicenter study, (total 51 patients), suggest that RFA is efficacious in terms of reducing transfusion dependency. In the setting of chronic hemorrhagic radiation proctopathy, a prospective monocenter study and a retrospective multicenter study (total 56 patients) suggest that RFA is an efficient treatment. A retrospective comparative study (64 patients) suggests that RFA improves stents patency in malignant biliary strictures. Conclusions Endoscopic RFA is an upcoming treatment modality in early esophageal squamous intra-epithelial neoplasia, as well as in gastric, rectal, and biliary diseases. PMID:26279839

  17. Laser systems for ablative fractional resurfacing

    DEFF Research Database (Denmark)

    Paasch, Uwe; Haedersdal, Merete

    2011-01-01

    of a variety of skin conditions, primarily chronically photodamaged skin, but also acne and burn scars. In addition, it is anticipated that AFR can be utilized in the laser-assisted delivery of topical drugs. Clinical efficacy coupled with minimal downtime has driven the development of various fractional...... ablative laser systems. Fractionated CO(2) (10,600-nm), erbium yttrium aluminum garnet, 2940-nm and yttrium scandium gallium garnet, 2790-nm lasers are available. In this article, we present an overview of AFR technology, devices and histopathology, and we summarize the current clinical possibilities...... with AFR incorporating our personal experience. AFR is still in the exploratory era, and systematic investigations of clinical outcomes related to various system settings are needed....

  18. Nanosecond laser ablation and deposition of silicon

    Energy Technology Data Exchange (ETDEWEB)

    Siew, Wee Ong; Tou, Teck Yong [Multimedia University, Faculty of Engineering, Cyberjaya, Selangor (Malaysia); Yap, Seong Shan; Reenaas, Turid Worren [Norwegian University of Science and Technology, Department of Physics, Trondheim (Norway); Ladam, Cecile; Dahl, Oeystein [SINTEF Materials and Chemistry, Trondheim (Norway)

    2011-09-15

    Nanosecond-pulsed KrF (248 nm, 25 ns) and Nd:YAG (1064 nm, 532 nm, 355 nm, 5 ns) lasers were used to ablate a polycrystalline Si target in a background pressure of <10{sup -4} Pa. Si films were deposited on Si and GaAs substrates at room temperature. The surface morphology of the films was characterized using scanning electron microscopy (SEM) and atomic force microscopy (AFM). Round droplets from 20 nm to 5 {mu}m were detected on the deposited films. Raman Spectroscopy indicated that the micron-sized droplets were crystalline and the films were amorphous. The dependence of the properties of the films on laser wavelengths and fluence is discussed. (orig.)

  19. Radiofrequency interstitial tumor ablation: dry electrode.

    Science.gov (United States)

    Johnson, D Brooke; Cadeddu, Jeffrey A

    2003-10-01

    With the shift in the treatment of small renal tumors from radical extirpative surgery to nephron-sparing approaches, dry-electrode radiofrequency ablation (RFA) has emerged as one potential modality. This application of RF energy leads to the production of heat within the treatment zone secondary to the native impedance of living tissue. Animal studies and human clinical series have demonstrated that RFA can create controlled, targeted, reproducible, and lethal lesions. Most clinical series have reported promising results, although some authors question the totality of tumor destruction by RFA. With time, the efficacy of RFA, as measured by patient survival, will be determined. Once this is known, RFA may be compared with other therapeutic modalities for small renal tumors to determine its place.

  20. Radiofrequency ablation of a misdiagnosed Brodie's abscess.

    Science.gov (United States)

    Chan, Rs; Abdullah, Bjj; Aik, S; Tok, Ch

    2011-04-01

    Radiofrequency ablation (RFA) therapy is recognised as a safe and effective treatment option for osteoid osteoma. This case report describes a 27-year-old man who underwent computed tomography (CT)-guided percutaneous RFA for a femoral osteoid osteoma, which was diagnosed based on his clinical presentation and CT findings. The patient developed worsening symptoms complicated by osteomyelitis after the procedure. His clinical progression and subsequent MRI findings had led to a revised diagnosis of a Brodie's abscess, which was further supported by the eventual resolution of his symptoms following a combination of antibiotics treatment and surgical irrigations. This case report illustrates the unusual MRI features of osteomyelitis mimicking soft tissue tumours following RFA of a misdiagnosed Brodie's abscess and highlights the importance of a confirmatory histopathological diagnosis for an osteoid osteoma prior to treatment.

  1. Three-dimensional simulations of ablative hydrodynamic instabilities in indirectly driven targets

    Energy Technology Data Exchange (ETDEWEB)

    Marinak, M.M.; Tipton, R.E.; Remington, B.A. [and others

    1996-06-01

    To model ignition in a National Ignition Facility (NIF) capsule implosion, the authors must understand the behavior of instabilities that can cause breakup of the pellet shell. During a capsule implosion, shocks that transit the shell cause growth of perturbations at the surface or at an interface because of a Richtmyer-Meshkov type of instability. Following shock breakout, or earlier for a shaped pulse, the low-density ablated plasma accelerates the pusher, and the ablation front is Rayleigh-Taylor (RT) unstable. Ablation and finite density gradients have the effect of stabilizing the short wavelength modes. Unstable modes present on the outer surface grow and feed through to the inner surface. Once the shell encounters the rebounding shock from the capsule center, it decelerates and the inner surface becomes RT unstable. If perturbations grow large enough, pusher material mixes into the core, degrading implosion performance. Capsule designs for the NIF depend on ablative stabilization and saturation to prevent perturbations initially present on the capsule surface from growing large enough to quench ignition. Here, the authors examine the first simulations and experiments to study the effect of 3-D perturbation shape on instability growth and saturation in indirectly driven targets. The first section discusses HYDRA, the radiation hydrodynamics code developed for these simulations. The subsequent section examines 3-D shape effects in single-mode perturbations in planar foil simulations and experiments. A discussion of the evolution of multimode perturbations on planar foils is followed by a discussion of 3-D simulations of instability growth in Nova capsule implosions.

  2. Ablation dynamics in laser sclerotomy ab externo

    Science.gov (United States)

    Brinkmann, Ralf; Droege, Gerit; Mohrenstecher, Dirk; Scheu, M.; Birngruber, Reginald

    1996-01-01

    Laser sclerostomy ab externo with flashlamp excited mid-IR laser systems emitting in the 2-3 micrometer spectral range is in phase II clinical trials. Although acutely high success rates were achieved, the restenosis rate after several months is about 40%. Laser pulses of several hundreds of microseconds, known to induce thermo-mechanical explosive evaporation were used for this procedure. We investigated the ablation dynamics in tissue and the cavitation bubble dynamics in water by means of an Er:YAG laser system to estimate the extent of mechanical damage zones in the sclera and in the anterior chamber, which may contribute to the clinical failure. We found substantial mechanical tissue deformation during the ablation process caused by the cavitation effects. Stress waves up to several bar generated by explosive evaporization were measured. The fast mechanical stretching and collapsing of the scleral tissue induced by cavitation resulted in tissue dissection as could be proved by flash photography and histology. The observed high restenosis might be a result of a subsequent enhanced wound healing process. Early fistula occlusions due to iris adherences, observed in about 20% of the clinical cases may be attributed to intraocular trauma induced by vapor bubble expansion through the anterior chamber after scleral perforation. An automatic feedback system minimizing adverse effects by steering and terminating the laser process during scleral fistulization is demonstrated. Moreover, a new approach in laser sclerostomy ab externo is presented using a cw-IR laser diode system emitting at the 1.94 micrometer mid-IR water absorption peak. This system was used in vitro and showed smaller damage zones compared to the pulsed laser radiation.

  3. Laparoscopic radiofrequency ablation of neuroendocrine liver metastases.

    Science.gov (United States)

    Berber, Eren; Flesher, Nora; Siperstein, Allan E

    2002-08-01

    We previously reported on the safety and efficacy of laparoscopic radiofrequency thermal ablation (RFA) for treating hepatic neuroendocrine metastases. The aim of this study is to report our 5-year RFA experience in the treatment of these challenging group of patients. Of the 222 patients with 803 liver primary and secondary tumors undergoing laparoscopic RFA between January 1996 and August 2001, a total of 34 patients with 234 tumors had neuroendocrine liver metastases. There were 25 men and 9 women with a mean +/- SEM age of 52 +/- 2 years who underwent 42 ablations. Primary tumor types included carcinoid tumor in 18 patients, medullary thyroid cancer in 7, secreting islet cell tumor in 5, and nonsecreting islet cell tumor in 4. There was no mortality, and the morbidity was 5%. The mean hospital stay was 1.1 days. Symptoms were ameliorated in 95%, with significant or complete symptom control in 80% of the patients for a mean of 10+ months (range 6-24 months). All patients were followed for a mean +/- SEM of 1.6 +/- 0.2 years (range 1.0-5.4 years). During this period new liver lesions developed in 28% of patients, new extrahepatic disease in 25%, and local liver recurrence in 13%; existing liver lesions progressed in 13%. Overall 41% of patients showed no progression of their cancer. Nine patients (27%) died. Mean +/- SEM survivals after diagnosis of primary disease, detection of liver metastases, and performance of RFA were 5.5 +/- 0.8 years, 3.0 +/- 0.3 years, and 1.6 +/- 0.2 years, respectively. Sixty-five percent of the patients demonstrated a partial or significant decrease in their tumor markers during follow-up. In conclusion, RFA provides excellent local tumor control with overnight hospitalization and low morbidity in the treatment of liver metastases from neuroendocrine tumors. It is a useful modality in the management of these challenging group of patients.

  4. Ablation from metals induced by visible and UV laser irradiation

    DEFF Research Database (Denmark)

    Svendsen, Winnie Edith; Schou, Jørgen; Thestrup Nielsen, Birgitte

    1996-01-01

    The deposition rate of laser-ablated silver has been determined for fluences between 0.5 and 15 J/cm2 at the wavelengths 532 and 355 nm for a beam spot area of around 0.01 cm2. The ablated metal was collected on a quartz crystal microbalance. The rate at 5 J/cm2 was about 4 × 1013 Ag/cm2 per pulse...... for 532 nm, and somewhat lower for 355 nm. The initial vaporization during the ablation has been studied numerically as well....

  5. Ablative Thermal Response Analysis Using the Finite Element Method

    Science.gov (United States)

    Dec John A.; Braun, Robert D.

    2009-01-01

    A review of the classic techniques used to solve ablative thermal response problems is presented. The advantages and disadvantages of both the finite element and finite difference methods are described. As a first step in developing a three dimensional finite element based ablative thermal response capability, a one dimensional computer tool has been developed. The finite element method is used to discretize the governing differential equations and Galerkin's method of weighted residuals is used to derive the element equations. A code to code comparison between the current 1-D tool and the 1-D Fully Implicit Ablation and Thermal Response Program (FIAT) has been performed.

  6. Analysis of illicit drugs by direct ablation of solid samples.

    Science.gov (United States)

    Bermúdez, Celina; Cabezas, Carlos; Mata, Santiago; Berdakin, Matias; Tejedor, Jesús M; Alonso, José L

    2015-01-01

    Analysis of illicit drugs arises as an important field of work given the high social impacts presented by drugs in the modern society. Direct laser ablation of solid compounds allows their analysis without sampling or preparation procedures. For that purpose, an experimental set-up that combines laser ablation with time-of- flight mass spectrometry has been constructed very recently to perform studies on the mass spectra of such drugs as 3,4-methylenedioxy-N-methylamphetamine, commonly known as MDMA or ecstasy. Analysis of the observed fragmentation pattern in mass spectra may elucidate the ablation-induced photofragmentation phenomena produced, which differ from those previously observed with conventional ionization methods.

  7. Alternative High Performance Polymers for Ablative Thermal Protection Systems

    Science.gov (United States)

    Boghozian, Tane; Stackpoole, Mairead; Gonzales, Greg

    2015-01-01

    Ablative thermal protection systems are commonly used as protection from the intense heat during re-entry of a space vehicle and have been used successfully on many missions including Stardust and Mars Science Laboratory both of which used PICA - a phenolic based ablator. Historically, phenolic resin has served as the ablative polymer for many TPS systems. However, it has limitations in both processing and properties such as char yield, glass transition temperature and char stability. Therefore alternative high performance polymers are being considered including cyanate ester resin, polyimide, and polybenzoxazine. Thermal and mechanical properties of these resin systems were characterized and compared with phenolic resin.

  8. Effects of Confined Laser Ablation on Laser Plasma Propulsion

    Institute of Scientific and Technical Information of China (English)

    ZHENG Zhi-Yuan; ZHANG Jie; LU Xin; HAO Zuo-Qiang; XU Miao-Hua; WANG Zhao-Hua; WEI Zhi-Yi

    2005-01-01

    @@ We investigate the effects of confined laser ablation on laser plasma propulsion. Compared with planar ablation,the cavity ablation provides an effective way to obtain a large target momentum and a high coupling coefficient.When laser pukes are focused into a cavity with 1 mm diameter and 2mm depth, a high coupling coefficient is obtained. By using a glass layer to cover the cavity, the coupling coefficient is enhanced by 10 times. Meanwhile,it is found that with the increase of the target surface size, the target momentum presents a linear increase.

  9. Ablation response testing of simulated radioisotope power supplies

    Science.gov (United States)

    Lutz, Steven A.; Chan, Chris C.

    1994-05-01

    Results of an experimental program to assess the aerothermal ablation response of simulated radioisotope power supplies are presented. Full-scale general purpose heat source, graphite impact shell, and lightweight radioisotope heater unit test articles are all tested without nuclear fuel in simulated reentry environments. Convective stagnation heating, stagnation pressure, stagnation surface temperature, surface recession profile, and weight loss measurements are obtained for diffusion-limited and sublimation ablation conditions. The recession profile and weight loss measurements show an effect of surface features on the stagnation face. The surface features alter the local heating which in turn affects the local ablation.

  10. Micrometeorological processes driving snow ablation in an Alpine catchment

    Directory of Open Access Journals (Sweden)

    R. Mott

    2011-11-01

    Full Text Available Mountain snow covers typically become patchy over the course of a melting season. The snow pattern during melt is mainly governed by the end of winter snow depth distribution and the local energy balance. The objective of this study is to investigate micro-meteorological processes driving snow ablation in an Alpine catchment. For this purpose we combine a meteorological boundary-layer model (Advanced Regional Prediction System with a fully distributed energy balance model (Alpine3D. Turbulent fluxes above melting snow are further investigated by using data from eddy-correlation systems. We compare modeled snow ablation to measured ablation rates as obtained from a series of Terrestrial Laser Scanning campaigns covering a complete ablation season. The measured ablation rates indicate that the advection of sensible heat causes locally increased ablation rates at the upwind edges of the snow patches. The effect, however, appears to be active over rather short distances of about 4–6 m. Measurements suggest that mean wind velocities of about 5 m s−1 are required for advective heat transport to increase snow ablation over a long fetch distance of about 20 m. Neglecting this effect, the model is able to capture the mean ablation rates for early ablation periods but strongly overestimates snow ablation once the fraction of snow coverage is below a critical value of approximately 0.6. While radiation dominates snow ablation early in the season, the turbulent flux contribution becomes important late in the season. Simulation results indicate that the air temperatures appear to overestimate the local air temperature above snow patches once the snow coverage is low. Measured turbulent fluxes support these findings by suggesting a stable internal boundary layer close to the snow surface causing a strong decrease of the sensible heat flux towards the snow cover. Thus, the existence of a stable internal boundary layer above a patchy snow cover

  11. Radiofrequency Ablation for Iatrogenic Thyroid Artery Pseudoaneurysm: Initial Experience.

    Science.gov (United States)

    Jun, Ye Kyeong; Jung, So Lyung; Byun, Ho Kyun; Baek, Jung Hwan; Sung, Jin Yong; Sim, Jung Suk

    2016-10-01

    Eight iatrogenic thyroid pseudoaneurysms (ITPAs) after thyroid biopsy are reported. The mean ITPA diameter was 7.2 mm (range 4 to 12 mm). Ultrasound (US)-guided compression was initially performed at the neck of the ITPA in all cases. Among them, 4 ITPAs persisted (50%) in which radiofrequency (RF) ablation was performed. Mean RF ablation time and power were 13.5 seconds (range 5 to 24 seconds) and 20 W (range 10 to 50 W), respectively. All 4 cases were treated with RF ablation without any complications.

  12. Enhanced coupling of optical energy during liquid-confined metal ablation

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Hyun Wook, E-mail: wkang@pknu.ac.kr [Department of Biomedical Engineering, Pukyong National University, Busan, South Korea and Center for Marine-integrated Biomedical Technology (MIBT), Pukyong National University, Busan (Korea, Republic of); Welch, Ashley J. [Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas, 78712 (United States)

    2015-10-21

    Liquid-confined laser ablation was investigated with various metals of indium, aluminum, and nickel. Ablation threshold and rate were characterized in terms of surface deformation, transient acoustic responses, and plasma emissions. The surface condition affected the degree of ablation dynamics due to variations in reflectance. The liquid confinement yielded up to an order of larger ablation crater along with stronger acoustic transients than dry ablation. Enhanced ablation performance resulted possibly from effective coupling of optical energy at the interface during explosive vaporization, plasma confinement, and cavitation. The deposition of a liquid layer can induce more efficient ablation for laser metal processing.

  13. Surgical and Pathological Changes after Radiofrequency Ablation of Thyroid Nodules

    Science.gov (United States)

    Dobrinja, Chiara; Bernardi, Stella; Fabris, Bruno; Eramo, Rita; Makovac, Petra; Bazzocchi, Gabriele; Piscopello, Lanfranco; Barro, Enrica; de Manzini, Nicolò; Bonazza, Deborah; Pinamonti, Maurizio; Zanconati, Fabrizio; Stacul, Fulvio

    2015-01-01

    Background. Radiofrequency ablation (RFA) has been recently advocated as an effective technique for the treatment of symptomatic benign thyroid nodules. It is not known to what extent it may affect any subsequent thyroid surgery and/or histological diagnosis. Materials and Methods. RFA was performed on 64 symptomatic Thy2 nodules (benign nodules) and 6 symptomatic Thy3 nodules (follicular lesions/follicular neoplasms). Two Thy3 nodules regrew after the procedure, and these patients accepted to undergo a total thyroidectomy. Here we present how RFA has affected the operation and the final pathological features of the surgically removed nodules. Results and Conclusions. RFA is effective for the treatment of Thy2 nodules, but it should not be recommended as first-line therapy for the treatment of Thy3 nodules (irrespective of their mutational status), as it delays surgery in case of malignancy. Moreover, it is unknown whether RFA might promote residual tumor progression or neoplastic progression of Thy3 lesions. Nevertheless, here we show for the first time that one session of RFA does not affect subsequent thyroid surgery and/or histological diagnosis. PMID:26265914

  14. Surgical and Pathological Changes after Radiofrequency Ablation of Thyroid Nodules

    Directory of Open Access Journals (Sweden)

    Chiara Dobrinja

    2015-01-01

    Full Text Available Background. Radiofrequency ablation (RFA has been recently advocated as an effective technique for the treatment of symptomatic benign thyroid nodules. It is not known to what extent it may affect any subsequent thyroid surgery and/or histological diagnosis. Materials and Methods. RFA was performed on 64 symptomatic Thy2 nodules (benign nodules and 6 symptomatic Thy3 nodules (follicular lesions/follicular neoplasms. Two Thy3 nodules regrew after the procedure, and these patients accepted to undergo a total thyroidectomy. Here we present how RFA has affected the operation and the final pathological features of the surgically removed nodules. Results and Conclusions. RFA is effective for the treatment of Thy2 nodules, but it should not be recommended as first-line therapy for the treatment of Thy3 nodules (irrespective of their mutational status, as it delays surgery in case of malignancy. Moreover, it is unknown whether RFA might promote residual tumor progression or neoplastic progression of Thy3 lesions. Nevertheless, here we show for the first time that one session of RFA does not affect subsequent thyroid surgery and/or histological diagnosis.

  15. Surgical and Pathological Changes after Radiofrequency Ablation of Thyroid Nodules.

    Science.gov (United States)

    Dobrinja, Chiara; Bernardi, Stella; Fabris, Bruno; Eramo, Rita; Makovac, Petra; Bazzocchi, Gabriele; Piscopello, Lanfranco; Barro, Enrica; de Manzini, Nicolò; Bonazza, Deborah; Pinamonti, Maurizio; Zanconati, Fabrizio; Stacul, Fulvio

    2015-01-01

    Background. Radiofrequency ablation (RFA) has been recently advocated as an effective technique for the treatment of symptomatic benign thyroid nodules. It is not known to what extent it may affect any subsequent thyroid surgery and/or histological diagnosis. Materials and Methods. RFA was performed on 64 symptomatic Thy2 nodules (benign nodules) and 6 symptomatic Thy3 nodules (follicular lesions/follicular neoplasms). Two Thy3 nodules regrew after the procedure, and these patients accepted to undergo a total thyroidectomy. Here we present how RFA has affected the operation and the final pathological features of the surgically removed nodules. Results and Conclusions. RFA is effective for the treatment of Thy2 nodules, but it should not be recommended as first-line therapy for the treatment of Thy3 nodules (irrespective of their mutational status), as it delays surgery in case of malignancy. Moreover, it is unknown whether RFA might promote residual tumor progression or neoplastic progression of Thy3 lesions. Nevertheless, here we show for the first time that one session of RFA does not affect subsequent thyroid surgery and/or histological diagnosis.

  16. Characterization of Material Response During Arc-Jet Testing with Optical Methods Status and Perspectives

    Science.gov (United States)

    Winter, Michael

    2012-01-01

    The characterization of ablation and recession of heat shield materials during arc jet testing is an important step towards understanding the governing processes during these tests and therefore for a successful extrapolation of ground test data to flight. The behavior of ablative heat shield materials in a ground-based arc jet facility is usually monitored through measurement of temperature distributions (across the surface and in-depth), and through measurement of the final surface recession. These measurements are then used to calibrate/validate materials thermal response codes, which have mathematical models with reasonably good fidelity to the physics and chemistry of ablation, and codes thus calibrated are used for predicting material behavior in flight environments. However, these thermal measurements only indirectly characterize the pyrolysis processes within an ablative material pyrolysis is the main effect during ablation. Quantification of pyrolysis chemistry would therefore provide more definitive and useful data for validation of the material response codes. Information of the chemical products of ablation, to various levels of detail, can be obtained using optical methods. Suitable optical methods to measure the shape and composition of these layers (with emphasis on the blowing layer) during arc jet testing are: 1) optical emission spectroscopy (OES) 2) filtered imaging 3) laser induced fluorescence (LIF) and 4) absorption spectroscopy. Several attempts have been made to optically measure the material response of ablative materials during arc-jet testing. Most recently, NH and OH have been identified in the boundary layer of a PICA ablator. These species are suitable candidates for a detection through PLIF which would enable a spatially-resolved characterization of the blowing layer in terms of both its shape and composition. The recent emission spectroscopy data will be presented and future experiments for a qualitative and quantitative

  17. Endovascular Radiofrequency Ablation for Varicose Veins

    Science.gov (United States)

    2011-01-01

    Executive Summary Objective The objective of the MAS evidence review was to conduct a systematic review of the available evidence on the safety, effectiveness, durability and cost–effectiveness of endovascular radiofrequency ablation (RFA) for the treatment of primary symptomatic varicose veins. Background The Ontario Health Technology Advisory Committee (OHTAC) met on August 26th, 2010 to review the safety, effectiveness, durability, and cost-effectiveness of RFA for the treatment of primary symptomatic varicose veins based on an evidence-based review by the Medical Advisory Secretariat (MAS). Clinical Condition Varicose veins (VV) are tortuous, twisted, or elongated veins. This can be due to existing (inherited) valve dysfunction or decreased vein elasticity (primary venous reflux) or valve damage from prior thrombotic events (secondary venous reflux). The end result is pooling of blood in the veins, increased venous pressure and subsequent vein enlargement. As a result of high venous pressure, branch vessels balloon out leading to varicosities (varicose veins). Symptoms typically affect the lower extremities and include (but are not limited to): aching, swelling, throbbing, night cramps, restless legs, leg fatigue, itching and burning. Left untreated, venous reflux tends to be progressive, often leading to chronic venous insufficiency (CVI). A number of complications are associated with untreated venous reflux: including superficial thrombophlebitis as well as variceal rupture and haemorrhage. CVI often results in chronic skin changes referred to as stasis dermatitis. Stasis dermatitis is comprised of a spectrum of cutaneous abnormalities including edema, hyperpigmentation, eczema, lipodermatosclerosis and stasis ulceration. Ulceration represents the disease end point for severe CVI. CVI is associated with a reduced quality of life particularly in relation to pain, physical function and mobility. In severe cases, VV with ulcers, QOL has been rated to be as bad

  18. Micrometeoroid ablation: metal abundances and fate of mesospheric metals

    Science.gov (United States)

    Rietmeijer, Frans

    Extraterrestrial materials ~20 micometer to ~1 cm in size entering the Earth's atmosphere include aggregate interplanetary dust particles (IDPs), cluster IDPs, CI and CM type micro-meteorites from periodic comets, the asteroid belt and near-Earth asteroids. This dust interacts with the atmosphere, ablation and evaporation, and causes steady-state mesospheric metal abundances that can be locally perturbed by meteor storms and (meteorite-producing) bolides. Solar system accretion was hierarchical and involved a few recycled non-chondritic dust types, viz. principal components (PCs), Fe,Ni-sulfides, Fe-oxides, (Mg,Fe)-olivine, (Mg,Fe,Ca)-pyroxenes, anorthite, and refractory Al,Ti-rich minerals. The PCs (0.1 - 2.0 micrometer) are carbonaceous units, C-bearing ferro-magnesiosilica, and Ca,Al-bearing ferromagnesiosilica units (i.e. CHON, mixed and silicate dust in comet Halley). Liberation from the parent body by ice sublimation, fragmentation, impact and others, will! disrupt this accretion hierarchy at the weakest textural bond. Micrometeoroid compositions are thus a function of size (the smallest dust is non-chondritic), the nature of their accretion environments and post-accretion textural modification. Collectively Zodiacal dust has the average composition of the combined accretion environments of the contributing sources. Within variations caused by the ablation process itself, mesospheric metals have almost chondritic abundances. I will discuss the mesospheric sodium abundance and Fe/Ni ratio. Sodium is difficult to analyze but there are indications that cometary Na-abundances exceed the cosmic value. Extraterrestrial matter has a unique Fe/Ni ratio. Despite its range due to natural variations among micrometeoroids, it is a diagnostic signature. The first tentative observation of condensed and coagulated meteoric matter included Fe/Ni-dust that was adhered to terrestrial dust in the upper stratosphere at ~35 km altitude along with Ti-oxides, Fe-oxides, silica and

  19. Measurements of nanoparticle size distribution produced by laser ablation of tungsten and boron-carbide in N{sub 2} ambient

    Energy Technology Data Exchange (ETDEWEB)

    Bereznai, Miklos [Department of Optics and Quantum Electronics, University of Szeged, Dom ter 9, 6720 Szeged (Hungary) and Department of Materials Chemistry, Angstroem Laboratory, Uppsala University, PO Box 538, SE-75121 Uppsala (Sweden)]. E-mail: bereznai@physx.u-szeged.hu; Heszler, Peter [Department of Engineering Sciences, Angstroem Laboratory, Uppsala University, PO Box 534, SE-75121 Uppsala (Sweden); Research Group on Laser Physics of the Hungarian Academy of Sciences, University of Szeged, Dom ter 9, 6720 Szeged (Hungary); Toth, Zsolt [Research Group on Laser Physics of the Hungarian Academy of Sciences, University of Szeged, Dom ter 9, 6720 Szeged (Hungary); Wilhelmsson, Ola [Department of Materials Chemistry, Angstroem Laboratory, Uppsala University, PO Box 538, SE-75121 Uppsala (Sweden); Boman, Mats [Department of Materials Chemistry, Angstroem Laboratory, Uppsala University, PO Box 538, SE-75121 Uppsala (Sweden)

    2006-04-30

    Nanoparticles (NPs) were produced by ablating tungsten and boron-carbide (B{sub 4}C) target materials in atmospheric pressure nitrogen ambient using ArF excimer laser pulses. The size distributions of the NPs formed during the ablation were monitored-within a 7-133 nm size window-by a condensation particle counter connected to a differential mobility analyzer. The laser repetition rate was varied between 1-50 Hz, and the fluence was systematically changed in the range of 0.5-15 J/cm{sup 2}, for both materials, allowing a comparative study in an extended laser parameter regime. The multishot ablation threshold ({phi} {sub th}) of B{sub 4}C was determined to be {approx}1.9 J/cm{sup 2} for the laser used (ArF excimer, {lambda} = 193 nm). Similarly to earlier studies, it was shown that the size distributions consist of mainly small nanoparticles (<{approx}20 nm) attributed to a non-thermal ablation mechanism below {phi} {sub th}. An additional broad peak appears (between 20 and 40 nm) above {phi} {sub th} as a consequence of the thermally induced macroscopic ablation. Chemical composition of deposited polydisperse nanoparticles was studied by X-ray photoelectron spectroscopy showing nitrogen incorporation into the boron-carbide.

  20. Cost comparison of low-field (0.23 T) MRI-guided laser ablation and surgery in the treatment of osteoid osteoma

    Energy Technology Data Exchange (ETDEWEB)

    Ronkainen, J.; Blanco Sequeiros, R.; Tervonen, O. [Oulu University Hospital, Department of Radiology, P.O. Box 50, Oulu (Finland)

    2006-12-15

    The purpose of this study was to analyze the costs of magnetic resonance imaging (MRI)-guided laser ablation and to compare them with the costs of surgery in the treatment of osteoid osteoma. Seven patients with osteoid osteoma were treated with MRI-guided interstitial laser ablation during 1 year. The reference material consisted of six patients whose osteoid osteoma was treated surgically by either superficial or deep excision with metallic fixation. The costs were analyzed by using activity-based cost accounting. The mean cost of the MRI-guided laser ablation was 2,392 euros and of the excision of superficially located osteoid osteoma 1,807 euros. The cost of excision of deeply located osteoma with metallic fixation was considerably higher (4,996 euros). This was due to the higher material, personnel, and ward costs. The cost of MRI-guided laser ablation of osteoid osteoma was higher than the cost of surgical excision of a superficial osteoma but considerably lower than the cost of excision of a deeply located osteoma where metallic fixation was needed. When the number and mean cost of sick days or days of restricted weight bearing were also included, the cost of MRI-guided laser ablation was lower than the costs of either superficial or deep excision. (orig.)

  1. MR-guided Neurolytic Celiac Plexus Ablation: An Evaluation of Effect and Injection Spread Pattern in Cancer Patients with Celiac Tumor Infiltration

    Energy Technology Data Exchange (ETDEWEB)

    Akural, Etem [Helsinki University Central Hospital, Pain Clinic (Finland); Ojala, Risto O. [Oulu University Hospital, Department of Radiology (Finland); Jaervimaeki, Voitto [Oulu University Hospital, Department of Anesthesiology (Finland); Kariniemi, Juho; Tervonen, Osmo A.; Blanco Sequeiros, Roberto, E-mail: roberto.blanco@oulu.fi [Oulu University Hospital, Department of Radiology (Finland)

    2013-04-15

    ObjectiveThe purpose of this study was to evaluate the feasibility, the initial accuracy, and the effects of the MR-guided neurolytic celiac plexus ablation as a method to treat cancer-induced chronic abdominal pain. Thirteen celiac plexus ablations were performed for 12 patients. A 0.23-T open MRI scanner with optical navigation was used for procedural guidance. As an adjunct to the MR-guided needle positioning, the needle location was confirmed with saline injection and consequent MR imaging (STIR sequence). The spread of the ablative injection material (alcohol-lidocaine mix) was observed by repeating this sequence after the therapeutic injection. Pain scores from seven patients (eight ablations) were used to assess the therapy effect. MR guidance allowed adequate needle positioning and visualization of injection material in all cases. The rest pain scores significantly decreased from 4 (median) at baseline to 1 (median) at 2 weeks (p < 0.05). Average and worst pain experienced during the past week were significantly lower at the 2-week time point compared with the baseline (p < 0.05). However, the intervention did not result in reduction of opioid use at 2 weeks.MR guidance is an accurate and safe method for celiac plexus ablation with positive therapeutic effect.

  2. Enhancing ablation efficiency in micro structuring using a deformable mirror for beam shaping of ultra-short laser pulses

    Science.gov (United States)

    Smarra, M.; Dickmann, K.

    2016-03-01

    Using ultra-short laser pulses for the generation of microstructures results in a high flexible tool for free form geometries in the micro range. Increasing laser power and repetition rates increase as well the demand of high flexible and efficient process strategies. To increase the ablation efficiency the optimal fluency can be determined, which is a material specific value. By varying the beam shape, the ablation efficiency can be enhanced. In this study a deformable mirror was used to vary the beam shape. This mirror is built by combining a piezo-electric ceramic and a mirror substrate. The ceramic is divided into several segments, which can be controlled independently. This results in a high flexible deformable mirror which influences the beam shape and can be used to vary the spot size or generate line geometries. The ablation efficiency and roughness of small generated cavities were analyzed in this study as well as the dimensions of the cavity. This can be used to optimize process strategies to combine high volume ablation and fine detail generation.

  3. Synthesis of cation-exchanged laponite suspensions by laser ablation of microsized-metal particles in liquid

    Science.gov (United States)

    Phuoc, Tran X.; Chen, Ruey-Hung

    2011-03-01

    Laser ablation in the liquid technique has been used to synthesize cation-exchanged laponite suspensions. In summary, laser ablation of the microsize-metal powder (Co, Al, and Cu) dispersed in an aqueous solution containing deionized water laponite crystals was carried out using laser beam generated by a single-mode, Q-switched Nd-Yag laser operating at 532 nm with a pulse duration of 5.5 ns and 10 Hz repetition rate. Laser fluence was 0.265 J/cm 2 for all tests. For all samples, the mass fraction of laponite was 1%. General observations of the prepared samples indicated that an aqueous suspension of 1 wt% laponite retained its free flowing liquid phase characteristics even after aging for several weeks. When bivalent cationic metals (Cu, Co, Al) were ablated in it for about 1 h, even with a small amount of the metal (0.025% and 0.050%) were generated, the suspension became highly viscous and behaved as a shear-thinning and thixotropic material. That is, the suspension gelled strongly when it was allowed to rest. The gels, however, could easily be reverted to a low viscosity liquid with simple shaking. Information from TEM and XRD analysis indicated that such a sol-gel transformation might be due to the charge exchange between the cationic species produced during the laser ablation and the sodium ions in the interlayers of the clay sheets.

  4. Characteristics of the ablation plume induced on glasses for analysis purposes with laser-induced breakdown spectroscopy

    Science.gov (United States)

    Tian, Ye; Sokolova, Ekaterina B.; Zheng, Ronger; Ma, Qianli; Chen, Yanping; Yu, Jin

    2015-12-01

    Laser-induced breakdown spectroscopy (LIBS) has been demonstrated as an efficient tool for elemental analyses of transparent dielectric materials such as glasses or crystals for more than ten years. The induced plasma is however much less studied compared to that induced on the surface of a metal. The purpose of this work is therefore to characterize the plasma induced on the surface of a glass sample for analytical purpose as a function of the ablation laser wavelength, infrared (IR) or ultraviolet (UV), and the ambient gas, air or argon. The surface damage of the samples was also observed for ablation with IR or UV laser pulse when the sample was a float glass or a frosted one. Optimized ablation fluence was then determined. The morphology of the plasma was observed with time-resolved spectroscopic imaging, while the profiles of the electron density and temperature were extracted from time- and space-resolved emission spectroscopy. The analytical performance of the plasmas was then studied in terms of the signal-to-noise ratio for several emission lines from some minor elements, Al, Fe, contained in glasses, and of the behavior of self-absorption for another minor element, Ca, in the different ablation conditions.

  5. Efficiency of Planetesimal Ablation in Giant Planetary Envelopes

    CERN Document Server

    Pinhas, Arazi; Clarke, Cathie

    2016-01-01

    Observations of exoplanetary spectra are leading to unprecedented constraints on their atmospheric elemental abundances, particularly O/H, C/H, and C/O ratios. Recent studies suggest that elemental ratios could provide important constraints on formation and migration mechanisms of giant exoplanets. A fundamental assumption in such studies is that the chemical composition of the planetary envelope represents the sum-total of compositions of the accreted gas and solids during the formation history of the planet. We investigate the efficiency with which accreted planetesimals ablate in a giant planetary envelope thereby contributing to its composition rather than sinking to the core. From considerations of aerodynamic drag causing `frictional ablation' and the envelope temperature structure causing `thermal ablation', we compute mass ablations for impacting planetesimals of radii 30 m to 1 km for different compositions (ice to iron) and a wide range of velocities and impact angles, assuming spherical symmetry. I...

  6. Intra-cardiac echocardiography in alcohol septal ablation

    DEFF Research Database (Denmark)

    Cooper, Robert M; Shahzad, Adeel; Newton, James;

    2015-01-01

    Alcohol septal ablation (ASA) in hypertrophic obstructive cardiomyopathy reduces left ventricular outflow tract gradients. A third of patients do not respond; inaccurate localisation of the iatrogenic infarct can be responsible. Transthoracic echocardiography (TTE) using myocardial contrast can b...

  7. Computer-aided hepatic tumour ablation requirements and preliminary results

    CERN Document Server

    Voirin, D; Amavizca, M; Letoublon, C; Troccaz, J; Voirin, David; Payan, Yohan; Amavizca, Miriam; Letoublon, Christian; Troccaz, Jocelyne

    2002-01-01

    Surgical resection of hepatic tumours is not always possible, since it depends on different factors, among which their location inside the liver functional segments. Alternative techniques consist in local use of chemical or physical agents to destroy the tumour. Radio frequency and cryosurgical ablations are examples of such alternative techniques that may be performed percutaneously. This requires a precise localisation of the tumour placement during ablation. Computer-assisted surgery tools may be used in conjunction with these new ablation techniques to improve the therapeutic efficiency, whilst they benefit from minimal invasiveness. This paper introduces the principles of a system for computer-assisted hepatic tumour ablation and describes preliminary experiments focusing on data registration evaluation. To keep close to conventional protocols, we consider registration of pre-operative CT or MRI data to intra-operative echographic data.

  8. Anatomical Consideration in Catheter Ablation of Idiopathic Ventricular Arrhythmias.

    Science.gov (United States)

    Yamada, Takumi; Kay, G Neal

    2016-01-01

    Idiopathic ventricular arrhythmias (VAs) are ventricular tachycardias (VTs) or premature ventricular contractions (PVCs) with a mechanism that is not related to myocardial scar. The sites of successful catheter ablation of idiopathic VA origins have been progressively elucidated and include both the endocardium and, less commonly, the epicardium. Idiopathic VAs usually originate from specific anatomical structures such as the ventricular outflow tracts, aortic root, atrioventricular (AV) annuli, papillary muscles, Purkinje network and so on, and exhibit characteristic electrocardiograms based on their anatomical background. Catheter ablation of idiopathic VAs is usually safe and highly successful, but can sometimes be challenging because of the anatomical obstacles such as the coronary arteries, epicardial fat pads, intramural and epicardial origins, AV conduction system and so on. Therefore, understanding the relevant anatomy is important to achieve a safe and successful catheter ablation of idiopathic VAs. This review describes the anatomical consideration in the catheter ablation of idiopathic VAs.

  9. Safety and efficacy of argon plasma coagulator ablation therapy for flat colorectal adenomas Seguridad y eficacia de la ablación de pólipos colorrectales con argón plasma

    OpenAIRE

    García, A.; O. Núñez; C. González-Asanza; Parera, A; L. Menchén; Ripoll, C.; Senent, C; E. Cos; P. Menchén

    2004-01-01

    Introduction: argon-plasma coagulation (APC) has been used safely and efficaciously in multiple settings including colon polyp treatment. The aim of this study was to evaluate APC efficacy and safety in the treatment of flat colorectal adenomas. Materials and methods: APC ablation was prospectively performed and evaluated in 22 consecutive patients with colorectal adenomas, 11 of which had large sessile adenomas that were treated with piecemeal polypectomy and APC ablation of residual adenoma...

  10. Mechanochemical endovenous Ablation versus RADiOfrequeNcy Ablation in the treatment of primary great saphenous vein incompetence (MARADONA) : study protocol for a randomized controlled trial

    NARCIS (Netherlands)

    van Eekeren, Ramon R. J. P.; Boersma, Doeke; Holewijn, Suzanne; Vahl, Anco; de Vries, Jean Paul P. M.; Zeebregts, Clark J.; Reijnen, Michel M. P. J.

    2014-01-01

    Background: Radiofrequency ablation (RFA) is associated with an excellent outcome in the treatment of great saphenous vein (GSV) incompetence. The use of thermal energy as a treatment source requires the instillation of tumescence anesthesia. Mechanochemical endovenous ablation (MOCA) combines mecha

  11. Simulation of femtosecond pulsed laser ablation of metals

    Science.gov (United States)

    Davydov, R. V.; Antonov, V. I.

    2016-11-01

    In this paper a mathematical model for femtosecond laser ablation of metals is proposed, based on standard two-temperature model connected with 1D hydrodynamic equations. Wide-range equation of state has been developed. The simulation results are compared with experimental data for aluminium and copper. A good agreement for both metals with numerical results and experiment shows that this model can be employed for choosing laser parameters to better accuracy in nanoparticles production by ablation of metals.

  12. Optimization of the generator settings for endobiliary radiofrequency ablation

    Institute of Scientific and Technical Information of China (English)

    Maximilien; Barret; Sarah; Leblanc; Ariane; Vienne; Alexandre; Rouquette; Frederic; Beuvon; Stanislas; Chaussade; Frederic; Prat

    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.

  13. Pulsed laser ablation and deposition of niobium carbide

    Science.gov (United States)

    Sansone, M.; De Bonis, A.; Santagata, A.; Rau, J. V.; Galasso, A.; Teghil, R.

    2016-06-01

    NbC crystalline films have been deposited in vacuum by ultra-short pulsed laser deposition technique. The films have been characterized by transmission and scanning electron microscopies and by X-ray diffraction. To clarify the ablation-deposition mechanism, the plasma produced by the ablation process has been characterized by optical emission spectroscopy and fast imaging. A comparison of the results with those obtained by ns pulsed deposition of the same target has been carried out.

  14. The characteristics of confined ablation in laser propulsion

    Institute of Scientific and Technical Information of China (English)

    Zheng Zhi-Yuan; Zhang Jie; Hao Zuo-Qiang; Yuan Xiao-Hui; Zhang Zhe; Lu Xin; Wang Zhao-Hua; Wei Zhi-Yi

    2006-01-01

    Compared with direct ablation, confined ablation provides an effective way to obtain a large target momentum and a high coupling coefficient. By using a transparent glass layer to cover the target surface, the coupling coefficient is enhanced by an order of magnitude. With the increase of the gap width between the target surface and the cover layer, the coupling coefficient exponentially decreases. It is found that the coupling coefficient is also related to the thickness of the cover layer.

  15. Isotope Effects of Solid Hydrogenic Pellet Ablation in Fusion Plasma

    Institute of Scientific and Technical Information of China (English)

    PENGLilin; DENGBaiquan; YANJiancheng; WANGXiaoyu

    2003-01-01

    The isotope effects of ablation processes in fusion plasma for five combinations of solid isotopic hydrogenic pellets H2, HD, D2,DT, T2 have been first time studied. The resuits show that the modifications caused by isotope effects for pellet erosion speeds range from 1 for hydrogen pellet down to 0. 487 for tritium pellet and are not negligible in ablation rate calculations. These effects lead to deeper mass deposition and improved core fueling efficiency.

  16. Langmuir probe study of plasma expansion in pulsed laser ablation

    DEFF Research Database (Denmark)

    Hansen, T.N.; Schou, Jørgen; Lunney, J.G.

    1999-01-01

    Langmuir probes were used to monitor the asymptotic expansion of the plasma produced by the laser ablation of a silver target in a vacuum. The measured angular and temporal distributions of the ion flux and electron temperature were found to be in good agreement with the self-similar isentropic...... and adiabatic solution of the gas dynamics equations describing the expansion. The value of the adiabatic index gamma was about 1.25, consistent with the ablation plume being a low temperature plasma....

  17. UV laser ablation of parylene films from gold substrates

    Energy Technology Data Exchange (ETDEWEB)

    O. R. Musaev, P. Scott, J. M. Wrobel, and M. B. Kruger

    2009-11-19

    Parylene films, coating gold substrates, were removed by laser ablation using 248 nm light from an excimer laser. Each sample was processed by a different number of pulses in one of three different environments: air at atmospheric pressure, nitrogen at atmospheric pressure, and vacuum. The laser-induced craters were analyzed by optical microscopy and x-ray photoelectron spectroscopy. Multi-pulse ablation thresholds of gold and parylene were estimated.

  18. A case of splenic abscess after radiofrequency ablation

    Institute of Scientific and Technical Information of China (English)

    Dimitris Zacharoulis; Emmanuel Katsogridakis; Constantinos Hatzitheofilou

    2006-01-01

    Radiofrequency ablation (RFA) is an innovative technique used primarily for the palliative treatment of unresectable liver tumors. Its therapeutic indications however, have been expanded and now include various other organs and diseases. There is a paucity of data regarding technical details and complications of the use of RFA in the spleen. We report a case of partial splenectomy using radiofrequency ablation for splenic hydatid disease,complicated by an abscess formation.

  19. Hollow nanoparticles of metal oxides and sulfides: fast preparation via laser ablation in liquid.

    Science.gov (United States)

    Niu, K Y; Yang, J; Kulinich, S A; Sun, J; Du, X W

    2010-11-16

    In this work, diverse hollow nanoparticles of metal oxides and sulfides were prepared by simply laser ablating metal targets in properly chosen liquids. The Kirkendall voiding and the selective heating with an infrared laser were shown to work as two independent mechanisms for the formation of such hollow nanoparticles in only one- or two-step synthesis approaches. One of the prepared materials, ZnS hollow nanoparticles, showed high performance in gas sensing. The simple, fast, inexpensive technique that is proposed demonstrates very promising perspectives.

  20. Development, Verification and Validation of Enclosure Radiation Capabilities in the CHarring Ablator Response (CHAR) Code

    Science.gov (United States)

    Salazar, Giovanni; Droba, Justin C.; Oliver, Brandon; Amar, Adam J.

    2016-01-01

    With the recent development of multi-dimensional thermal protection system (TPS) material response codes including the capabilities to account for radiative heating is a requirement. This paper presents the recent efforts to implement such capabilities in the CHarring Ablator Response (CHAR) code developed at NASA's Johnson Space Center. This work also describes the different numerical methods implemented in the code to compute view factors for radiation problems involving multiple surfaces. Furthermore, verification and validation of the code's radiation capabilities are demonstrated by comparing solutions to analytical results, to other codes, and to radiant test data.