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Sample records for ablator areal density

  1. Gamma Reaction History ablator areal density constraints upon correlated diagnostic modeling of National Ignition Facility implosion experiments

    SciTech Connect

    Cerjan, C. Sayre, D. B.; Landen, O. L.; Church, J. A.; Stoeffl, W.; Grafil, E. M.; Herrmann, H. W.; Hoffman, N. M.; Kim, Y.

    2015-03-15

    The inelastic neutron scattering induced γ-ray signal from {sup 12}C in an Inertial Confinement Fusion capsule is demonstrated to be an effective and general diagnostic for shell ablator areal density. Experimental acquisition of the time-integrated signal at 4.4 MeV using threshold detection from four gas Čerenkov cells provides a direct measurement of the {sup 12}C areal density near stagnation. Application of a three-dimensional isobaric static model of data acquired in a recent high neutron yield National Ignition Facility experimental campaign reveals two general trends: smaller remaining ablator mass at stagnation and higher shell density with increasing laser drive.

  2. Use of 41Ar production to measure ablator areal density in NIF beryllium implosions

    NASA Astrophysics Data System (ADS)

    Wilson, D. C.; Cassata, W. B.; Sepke, S. M.; Velsko, C. A.; Huang, H.; Yeamans, C. B.; Kline, J. L.; Yi, A.; Simakov, A. N.; Haan, S. W.; Batha, S. H.; Dewald, E. L.; Rygg, J. R.; Tommasini, R.; Xu, H.; Kong, C.; Bae, J.; Rice, N.

    2017-02-01

    For the first time, 41Ar produced by the (n,ϒ) reaction from 40Ar in the beryllium shell of a DT filled Inertial Confinement Fusion capsule has been measured. Ar is co-deposited with beryllium in the sputter deposition of the capsule shell. Combined with a measurement of the neutron yield, the radioactive 41Ar then quantifies the areal density of beryllium during the DT neutron production. The measured 1.15 ± 0.17 × 10+8 atoms of 41Ar are 2.5 times that from the best post-shot calculation, suggesting that the Ar and Be areal densities are correspondingly higher than those calculated. Possible explanations are that (1) the beryllium shell is compressed more than calculated, (2) beryllium has mixed into the cold DT ice, or more likely (3) less beryllium is ablated than calculated. Since only one DT filled beryllium capsule has been fielded at NIF, these results can be confirmed and expanded in the future.

  3. Using gamma-ray emission to measure ablator areal density of imploded capsules at the Omega laser

    NASA Astrophysics Data System (ADS)

    Hoffman, N.; Rubery, M.; Herrmann, H.; Kim, Y.; Young, C.; Mack, J.; Wilson, D.; McEvoy, A.; Evans, S.; Sedillo, T.; Stoeffl, W.; Horsfield, C.; Glebov, V.

    2010-11-01

    We have measured the ablator areal density of plastic-shell implosions at the Omega laser, using gamma-ray emission from the capsules detected by the prototype Gamma Reaction History (GRH) diagnostic. The intensity of 4.44-MeV gamma emission from ^12C nuclei in the ablator is proportional to the product of ablator areal density and yield of fusion neutrons, so by detecting the gammas we can infer the ablator areal density, provided we also have a measurement of total neutron yield. Neutron yield is determined from the nTOF experiment at Omega in our approach; alternatively one could use 16.7-MeV gammas from DT fusion. Inferred values of time-averaged carbon areal density are in the range 10-30 mg/cm^2, for a range of implosions. These values are smaller than predicted values based on 1D simulations, which are typically in the range 30-40 mg/cm^2. We discuss possible reasons for the discrepancy, primarily related to mixing.

  4. Note: Radiochemical measurement of fuel and ablator areal densities in cryogenic implosions at the National Ignition Facility.

    PubMed

    Hagmann, C; Shaughnessy, D A; Moody, K J; Grant, P M; Gharibyan, N; Gostic, J M; Wooddy, P T; Torretto, P C; Bandong, B B; Bionta, R; Cerjan, C J; Bernstein, L A; Caggiano, J A; Herrmann, H W; Knauer, J P; Sayre, D B; Schneider, D H; Henry, E A; Fortner, R J

    2015-07-01

    A new radiochemical method for determining deuterium-tritium (DT) fuel and plastic ablator (CH) areal densities (ρR) in high-convergence, cryogenic inertial confinement fusion implosions at the National Ignition Facility is described. It is based on measuring the (198)Au/(196)Au activation ratio using the collected post-shot debris of the Au hohlraum. The Au ratio combined with the independently measured neutron down scatter ratio uniquely determines the areal densities ρR(DT) and ρR(CH) during burn in the context of a simple 1-dimensional capsule model. The results show larger than expected ρR(CH) values, hinting at the presence of cold fuel-ablator mix.

  5. Note: Radiochemical measurement of fuel and ablator areal densities in cryogenic implosions at the National Ignition Facility

    SciTech Connect

    Hagmann, C. Shaughnessy, D. A.; Moody, K. J.; Grant, P. M.; Gharibyan, N.; Gostic, J. M.; Wooddy, P. T.; Torretto, P. C.; Bandong, B. B.; Bionta, R.; Cerjan, C. J.; Bernstein, L. A.; Caggiano, J. A.; Sayre, D. B.; Schneider, D. H.; Henry, E. A.; Fortner, R. J.; Herrmann, H. W.; Knauer, J. P.

    2015-07-15

    A new radiochemical method for determining deuterium-tritium (DT) fuel and plastic ablator (CH) areal densities (ρR) in high-convergence, cryogenic inertial confinement fusion implosions at the National Ignition Facility is described. It is based on measuring the {sup 198}Au/{sup 196}Au activation ratio using the collected post-shot debris of the Au hohlraum. The Au ratio combined with the independently measured neutron down scatter ratio uniquely determines the areal densities ρR(DT) and ρR(CH) during burn in the context of a simple 1-dimensional capsule model. The results show larger than expected ρR(CH) values, hinting at the presence of cold fuel-ablator mix.

  6. Note: Radiochemical measurement of fuel and ablator areal densities in cryogenic implosions at the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Hagmann, C.; Shaughnessy, D. A.; Moody, K. J.; Grant, P. M.; Gharibyan, N.; Gostic, J. M.; Wooddy, P. T.; Torretto, P. C.; Bandong, B. B.; Bionta, R.; Cerjan, C. J.; Bernstein, L. A.; Caggiano, J. A.; Herrmann, H. W.; Knauer, J. P.; Sayre, D. B.; Schneider, D. H.; Henry, E. A.; Fortner, R. J.

    2015-07-01

    A new radiochemical method for determining deuterium-tritium (DT) fuel and plastic ablator (CH) areal densities (ρR) in high-convergence, cryogenic inertial confinement fusion implosions at the National Ignition Facility is described. It is based on measuring the 198Au/196Au activation ratio using the collected post-shot debris of the Au hohlraum. The Au ratio combined with the independently measured neutron down scatter ratio uniquely determines the areal densities ρR(DT) and ρR(CH) during burn in the context of a simple 1-dimensional capsule model. The results show larger than expected ρR(CH) values, hinting at the presence of cold fuel-ablator mix.

  7. Measurement of areal density in the ablators of inertial-confinement-fusion capsules via detection of ablator (n, n'γ) gamma-ray emission

    NASA Astrophysics Data System (ADS)

    Hoffman, N. M.; Herrmann, H. W.; Kim, Y. H.; Hsu, H. H.; Horsfield, C. J.; Rubery, M. S.; Miller, E. K.; Grafil, E.; Stoeffl, W.; Church, J. A.; Young, C. S.; Mack, J. M.; Wilson, D. C.; Langenbrunner, J. R.; Evans, S. C.; Sedillo, T. J.; Glebov, V. Yu.; Duffy, T.

    2013-04-01

    We report the first gamma-ray-based measurements of the areal density of ablators in inertial-confinement-fusion capsule implosions. The measurements, made at the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)], used observations of gamma rays arising from inelastic scattering of 14.1-MeV deuterium-tritium (DT) neutrons on 12C nuclei in the compressed plastic ablators. The emission of 12C(n,n'γ) gamma rays from the capsules is detected using the Gamma Reaction History instrument [H. W. Herrmann et al., J. Phys.: Conf. Ser. 244, 032047 (2010)] operating at OMEGA. From the ratio of a capsule's 12C(n,n'γ) emission to the emission from the same processes in an in situ reference graphite "puck" of known mass and geometry [N. M. Hoffman et al., in IFSA 2011 proceedings (submitted)], we determine the time-averaged areal density of 12C in the capsule's compressed ablator. Measured values of total ablator areal density for thirteen imploded capsules, in the range 23 ± 10 to 58 ± 14 mg/cm2, are comparable to values calculated in 1D radiation-hydrodynamic simulations, and measured by charged-particle techniques.

  8. Using gamma-ray emission to measure areal density of ICF capsules

    SciTech Connect

    Hoffman, Nelson M; Wilson, Douglas C; Hermann, Hans W; Young, Carlton S

    2010-01-01

    Fusion neutrons streaming from a burning ICF capsule generate gamma rays via nuclear inelastic scattering in the ablator of the capsule. The intensity of gamma-ray emission is proportional to the product of the ablator areal density ('{rho}R') and the yield of fusion neutrons, so by detecting the gamma rays we can infer the ablator areal density, provided we also have a measurement of the capsule's total neutron yield. In plastic-shell capsules, for example, {sup 12}C nuclei emit gamma rays at 4.44 MeV after excitation by 14.1-MeV neutrons from D+T fusion. These gamma rays can be measured by the Gamma Reaction History (GRH) experiment being built at the National Ignition Facility (NIF). A linear error analysis indicates the chief sources of uncertainty in inferred areal density.

  9. Tent-induced perturbations on areal density of implosions at the National Ignition Facility

    SciTech Connect

    Tommasini, R. Field, J. E.; Hammel, B. A.; Landen, O. L.; Haan, S. W.; Aracne-Ruddle, C.; Benedetti, L. R.; Bradley, D. K.; Callahan, D. A.; Dewald, E. L.; Doeppner, T.; Edwards, M. J.; Hurricane, O. A.; Izumi, N.; Jones, O. A.; Ma, T.; Meezan, N. B.; Nagel, S. R.; Rygg, J. R.; Stadermann, M.; and others

    2015-05-15

    Areal density non-uniformities seeded by time-dependent drive variations and target imperfections in Inertial Confinement Fusion (ICF) targets can grow in time as the capsule implodes, with growth rates that are amplified by instabilities. Here, we report on the first measurements of the perturbations on the density and areal density profiles induced by the membranes used to hold the capsule within the hohlraum in indirect drive ICF targets. The measurements are based on the reconstruction of the ablator density profiles from 2D radiographs obtained using pinhole imaging coupled to area backlighting, as close as 150 ps to peak compression. Our study shows a clear correlation between the modulations imposed on the areal density and measured neutron yield, and a 3× reduction in the areal density perturbations comparing a high-adiabat vs. low-adiabat pulse shape.

  10. Tent-induced perturbations on areal density of implosions at the National Ignition Facilitya)

    NASA Astrophysics Data System (ADS)

    Tommasini, R.; Field, J. E.; Hammel, B. A.; Landen, O. L.; Haan, S. W.; Aracne-Ruddle, C.; Benedetti, L. R.; Bradley, D. K.; Callahan, D. A.; Dewald, E. L.; Doeppner, T.; Edwards, M. J.; Hurricane, O. A.; Izumi, N.; Jones, O. A.; Ma, T.; Meezan, N. B.; Nagel, S. R.; Rygg, J. R.; Segraves, K. S.; Stadermann, M.; Strauser, R. J.; Town, R. P. J.

    2015-05-01

    Areal density non-uniformities seeded by time-dependent drive variations and target imperfections in Inertial Confinement Fusion (ICF) targets can grow in time as the capsule implodes, with growth rates that are amplified by instabilities. Here, we report on the first measurements of the perturbations on the density and areal density profiles induced by the membranes used to hold the capsule within the hohlraum in indirect drive ICF targets. The measurements are based on the reconstruction of the ablator density profiles from 2D radiographs obtained using pinhole imaging coupled to area backlighting, as close as 150 ps to peak compression. Our study shows a clear correlation between the modulations imposed on the areal density and measured neutron yield, and a 3× reduction in the areal density perturbations comparing a high-adiabat vs. low-adiabat pulse shape.

  11. Fuel areal density distributions derived from nuclear scattering signatures

    NASA Astrophysics Data System (ADS)

    Bionta, R. M.; Casey, D. T.; Cerjan, C. J.; Yeamans, C. B.; Gatu Johnson, M. G.

    2016-10-01

    The spatial variation of activities measured in the array of 20 Nuclear Activation Detectors mounted on the flanges around the NIF target chamber (FNADs) are correlated with asymmetries in the underlying fuel areal density of compressed ICF targets. The asymmetric areal density distributions cause variations in the neutron spectra with direction which are seen in the dsr (down scattered ratio) metric, the ratio of the number of 10-12 MeV neutrons to the number of 13-15 MeV neutrons. We show, using a simple physics based simulation of neutron scattering through an idealized non-uniform DT shell with a realistic neutron source, that for most shots an areal distribution can be found which reproduces both the FNAD activity and the dsr measurements. Furthermore, by linking the simulation to a Marquardt minimizer, we fit the areal distribution to a truncated set of spherical harmonics. Prepared by LLNL under Contract DE-AC52-07NA27344.

  12. Radiochemical Signatures of Interfacial Areal Density and Mix in NIF Implosions

    NASA Astrophysics Data System (ADS)

    Cerjan, Charles; Cassata, William; Velsko, Carol; Hoffman, Rob; Sepke, Scott; Jedlovec, Donald; Stoeffl, Wolfgang; Shaughnessy, Dawn

    2015-11-01

    Recent experimental results from the Radiochemical Analysis of Gaseous Samples (RAGS) diagnostic facility fielded at the National Ignition Facility (NIF) have demonstrated 13N production from charged particle nuclear reactions. This radiochemical product is very sensitive to the fuel-ablator interface areal density. Two specific reactions dominate 13N production: 12C(d,n)13Nand13C(p,n)13N. The short range of the energetically up-scattered deuterons from the cold DT fuel layer restricts the production to the proximate ablator interface thus providing high sensitivity to the interfacial configuration. Although the proton-mediated reaction is almost equally favorable, the small natural abundance of 13C suppresses this contribution to 13N production. Representative HYDRA simulations are used to illustrate these observed effects. This work was performed under the auspices of the U. S. Department of Energy by the Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  13. Improving CMD Areal Density Analysis: Algorithms and Strategies

    NASA Astrophysics Data System (ADS)

    Wilson, R. E.

    2014-06-01

    Essential ideas, successes, and difficulties of Areal Density Analysis (ADA) for color-magnitude diagrams (CMD¡¯s) of resolved stellar populations are examined, with explanation of various algorithms and strategies for optimal performance. A CMDgeneration program computes theoretical datasets with simulated observational error and a solution program inverts the problem by the method of Differential Corrections (DC) so as to compute parameter values from observed magnitudes and colors, with standard error estimates and correlation coefficients. ADA promises not only impersonal results, but also significant saving of labor, especially where a given dataset is analyzed with several evolution models. Observational errors and multiple star systems, along with various single star characteristics and phenomena, are modeled directly via the Functional Statistics Algorithm (FSA). Unlike Monte Carlo, FSA is not dependent on a random number generator. Discussions include difficulties and overall requirements, such as need for fast evolutionary computation and realization of goals within machine memory limits. Degradation of results due to influence of pixelization on derivatives, Initial Mass Function (IMF) quantization, IMF steepness, low Areal Densities (A ), and large variation in A are reduced or eliminated through a variety of schemes that are explained sufficiently for general application. The Levenberg-Marquardt and MMS algorithms for improvement of solution convergence are contained within the DC program. An example of convergence, which typically is very good, is shown in tabular form. A number of theoretical and practical solution issues are discussed, as are prospects for further development.

  14. Shock ignition of thermonuclear fuel with high areal density.

    PubMed

    Betti, R; Zhou, C D; Anderson, K S; Perkins, L J; Theobald, W; Solodov, A A

    2007-04-13

    A novel method by C. Zhou and R. Betti [Bull. Am. Phys. Soc. 50, 140 (2005)] to assemble and ignite thermonuclear fuel is presented. Massive cryogenic shells are first imploded by direct laser light with a low implosion velocity and on a low adiabat leading to fuel assemblies with large areal densities. The assembled fuel is ignited from a central hot spot heated by the collision of a spherically convergent ignitor shock and the return shock. The resulting fuel assembly features a hot-spot pressure greater than the surrounding dense fuel pressure. Such a nonisobaric assembly requires a lower energy threshold for ignition than the conventional isobaric one. The ignitor shock can be launched by a spike in the laser power or by particle beams. The thermonuclear gain can be significantly larger than in conventional isobaric ignition for equal driver energy.

  15. Mammoth ecosystem: Climatic areal, animal's density and cause of extinctions

    NASA Astrophysics Data System (ADS)

    Zimov, S.; Zimov, N.; Zimova, G.; Chapin, S. F.

    2008-12-01

    During the last glaciations Mammoth Ecosystem (ME) occupied territory from present-day France to Canada and from the Arctic islands to China. This ecosystem played major role in global carbon cycle and human settling around the planet. Causes of extinction of this ecosystem are debatable. Analyses of hundreds of radiocarbon dates of ME animal fossil remains showed that warming and moistening of climate wasn't accompanied by animal extinction. On the opposite, on the north right after the warming rise of herbivore population was observed. Reconstruction of ME climatic areal showed that its climatic optimum lies within range of annual precipitation of 200-350 mm and average summer temperatures of +8-+12oC which corresponds with modern climate of Northern Siberia. Analyses of bones and skeletons concentrations in permafrost of Northern Siberia showed that animal density in ME was similar to African savannah. That was a high productive ecosystem that could sustain in wide variety of climates because numerous herbivores maintained there pastures themselves.

  16. In situ calibration of the Gamma Reaction History instrument using reference samples ("pucks") for areal density measurements

    NASA Astrophysics Data System (ADS)

    Hoffman, N. M.; Herrmann, H. W.; Kim, Y. H.; Hsu, H. H.; Horsfield, C. J.; Rubery, M. S.; Wilson, D. C.; Stoeffl, W. W.; Young, C. S.; Mack, J. M.; Miller, E. K.; Grafil, E.; Evans, S. C.; Sedillo, T. J.; Glebov, V. Yu.; Duffy, T.

    2013-11-01

    The introduction of a sample of carbon, for example a disk or "puck", near an imploding DT-filled capsule creates a source of 12C gamma rays that can serve as a reference for calibrating the response of the Gamma Reaction History (GRH) detector [1]. Such calibration is important in the measurement of ablator areal density ⟨ρR⟩abl in plastic-ablator DT-filled capsules at OMEGA [2], by allowing ⟨ρR⟩abl to be inferred as a function of ratios of signals rather than from absolute measurements of signal magnitudes. Systematic uncertainties in signal measurements and detector responses therefore cancel, permitting more accurate measurements of ⟨ρR⟩abl.

  17. Folding paper-based lithium-ion batteries for higher areal energy densities.

    PubMed

    Cheng, Qian; Song, Zeming; Ma, Teng; Smith, Bethany B; Tang, Rui; Yu, Hongyu; Jiang, Hanqing; Chan, Candace K

    2013-10-09

    Paper folding techniques are used in order to compact a Li-ion battery and increase its energy per footprint area. Full cells were prepared using Li4Ti5O12 and LiCoO2 powders deposited onto current collectors consisting of paper coated with carbon nanotubes. Folded cells showed higher areal capacities compared to the planar versions with a 5 × 5 cell folded using the Miura-ori pattern displaying a ~14× increase in areal energy density.

  18. Effects of pulse duration and areal density on ultrathin foil acceleration

    SciTech Connect

    Zhang Xiaomei; Shen Baifei; Ji Liangliang; Wang Fengchao; Wen Meng; Wang Wenpeng; Xu Jiancai; Yu Yahong

    2010-06-15

    The influence of laser pulse duration and areal density of target in the interaction of a circularly polarized pulse with an ultrathin overdense foil is investigated. One-dimensional particle-in-cell simulation shows that with an appropriate laser-pulse rising front, the light pressure acceleration regime is effective even though the thin foil is transparent. As the laser intensity evolves, three stages in the acceleration process can be identified: at first the total reflection of the laser pulse, followed by partial reflection, and then near total reflection again due to the Doppler effect. The influences of the rising front of laser pulse and areal density of the ultrathin foil are investigated. It is found that an optimal laser pulse rising front exists for obtaining high (saturation) ion energy with the same laser energy within a short time. An optimal areal density also exists for obtaining the highest energy. For the same laser pulse, a higher areal density or a higher density with same areal density is more appropriate for obtaining a stationary state for making light pressure acceleration mechanism more effective.

  19. Spinstand demonstration of areal density enhancement using two-dimensional magnetic recording (invited)

    SciTech Connect

    Lippman, Thomas Brockie, Richard; Contreras, John; Garzon, Samir; Leong, Tom; Marley, Arley; Wood, Roger; Zakai, Rehan; Zolla, Howard; Coker, Jon; Galbraith, Rick; Hanson, Weldon; Duquette, Paul; Petrizzi, Joe

    2015-05-07

    Exponential growth of the areal density has driven the magnetic recording industry for almost sixty years. But now areal density growth is slowing down, suggesting that current technologies are reaching their fundamental limit. The next generation of recording technologies, namely, energy-assisted writing and bit-patterned media, remains just over the horizon. Two-Dimensional Magnetic Recording (TDMR) is a promising new approach, enabling continued areal density growth with only modest changes to the heads and recording electronics. We demonstrate a first generation implementation of TDMR by using a dual-element read sensor to improve the recovery of data encoded by a conventional low-density parity-check (LDPC) channel. The signals are combined with a 2D equalizer into a single modified waveform that is decoded by a standard LDPC channel. Our detection hardware can perform simultaneous measurement of the pre- and post-combined error rate information, allowing one set of measurements to assess the absolute areal density capability of the TDMR system as well as the gain over a conventional shingled magnetic recording system with identical components. We discuss areal density measurements using this hardware and demonstrate gains exceeding five percent based on experimental dual reader components.

  20. Spinstand demonstration of areal density enhancement using two-dimensional magnetic recording (invited)

    NASA Astrophysics Data System (ADS)

    Lippman, Thomas; Brockie, Richard; Coker, Jon; Contreras, John; Galbraith, Rick; Garzon, Samir; Hanson, Weldon; Leong, Tom; Marley, Arley; Wood, Roger; Zakai, Rehan; Zolla, Howard; Duquette, Paul; Petrizzi, Joe

    2015-05-01

    Exponential growth of the areal density has driven the magnetic recording industry for almost sixty years. But now areal density growth is slowing down, suggesting that current technologies are reaching their fundamental limit. The next generation of recording technologies, namely, energy-assisted writing and bit-patterned media, remains just over the horizon. Two-Dimensional Magnetic Recording (TDMR) is a promising new approach, enabling continued areal density growth with only modest changes to the heads and recording electronics. We demonstrate a first generation implementation of TDMR by using a dual-element read sensor to improve the recovery of data encoded by a conventional low-density parity-check (LDPC) channel. The signals are combined with a 2D equalizer into a single modified waveform that is decoded by a standard LDPC channel. Our detection hardware can perform simultaneous measurement of the pre- and post-combined error rate information, allowing one set of measurements to assess the absolute areal density capability of the TDMR system as well as the gain over a conventional shingled magnetic recording system with identical components. We discuss areal density measurements using this hardware and demonstrate gains exceeding five percent based on experimental dual reader components.

  1. High-areal-density fuel assembly in direct-drive cryogenic implosions.

    PubMed

    Sangster, T C; Goncharov, V N; Radha, P B; Smalyuk, V A; Betti, R; Craxton, R S; Delettrez, J A; Edgell, D H; Glebov, V Yu; Harding, D R; Jacobs-Perkins, D; Knauer, J P; Marshall, F J; McCrory, R L; McKenty, P W; Meyerhofer, D D; Regan, S P; Seka, W; Short, R W; Skupsky, S; Soures, J M; Stoeckl, C; Yaakobi, B; Shvarts, D; Frenje, J A; Li, C K; Petrasso, R D; Séguin, F H

    2008-05-09

    The first observation of ignition-relevant areal-density deuterium from implosions of capsules with cryogenic fuel layers at ignition-relevant adiabats is reported. The experiments were performed on the 60-beam, 30-kJUV OMEGA Laser System [T. R. Boehly, Opt. Commun. 133, 495 (1997)10.1016/S0030-4018(96)00325-2]. Neutron-averaged areal densities of 202+/-7 mg/cm2 and 182+/-7 mg/cm2 (corresponding to estimated peak fuel densities in excess of 100 g/cm3) were inferred using an 18-kJ direct-drive pulse designed to put the converging fuel on an adiabat of 2.5. These areal densities are in good agreement with the predictions of hydrodynamic simulations indicating that the fuel adiabat can be accurately controlled under ignition-relevant conditions.

  2. Generation of ramp waves using variable areal density flyers

    NASA Astrophysics Data System (ADS)

    Winter, R. E.; Cotton, M.; Harris, E. J.; Chapman, D. J.; Eakins, D.

    2016-07-01

    Ramp loading using graded density impactors as flyers in gas-gun-driven plate impact experiments can yield new and useful information about the equation of state and the strength properties of the loaded material. Selective Laser Melting, an additive manufacturing technique, was used to manufacture a graded density flyer, termed the "bed-of-nails" (BON). A 2.5-mm-thick × 99.4-mm-diameter solid disc of stainless steel formed a base for an array of tapered spikes of length 5.5 mm and spaced 1 mm apart. The two experiments to test the concept were performed at impact velocities of 900 and 1100 m/s using the 100-mm gas gun at the Institute of Shock Physics at Imperial College London. In each experiment, a BON flyer was impacted onto a copper buffer plate which helped to smooth out perturbations in the wave profile. The ramp delivered to the copper buffer was in turn transmitted to three tantalum targets of thicknesses 3, 5 and 7 mm, which were mounted in contact with the back face of the copper. Heterodyne velocimetry (Het-V) was used to measure the velocity-time history, at the back faces of the tantalum discs. The wave profiles display a smooth increase in velocity over a period of ˜ 2.5 μs, with no indication of a shock jump. The measured profiles have been analysed to generate a stress vs. volume curve for tantalum. The results have been compared with the predictions of the Sandia National Laboratories hydrocode, CTH.

  3. Fabrication of silicon oxide nanodots with an areal density beyond 1 teradots inch(-2).

    PubMed

    Xu, Ji; Hong, Sung Woo; Gu, Weiyin; Lee, Kim Y; Kuo, David S; Xiao, Shuaigang; Russell, Thomas P

    2011-12-22

    The combination of solvent annealing, surface reconstruction, and a tone-reversal etching procedure provides an attractive approach to utilize block copolymer (BCP) lithography to fabricate highly ordered and densely packed silicon oxide nano-dots on a surface. The obtained silicon oxide nano-dots feature an areal density of 1.3 teradots inch(-2) .

  4. Areal density optimizations for heat-assisted magnetic recording of high-density media

    NASA Astrophysics Data System (ADS)

    Vogler, Christoph; Abert, Claas; Bruckner, Florian; Suess, Dieter; Praetorius, Dirk

    2016-06-01

    Heat-assisted magnetic recording (HAMR) is hoped to be the future recording technique for high-density storage devices. Nevertheless, there exist several realization strategies. With a coarse-grained Landau-Lifshitz-Bloch model, we investigate in detail the benefits and disadvantages of a continuous and pulsed laser spot recording of shingled and conventional bit-patterned media. Additionally, we compare single-phase grains and bits having a bilayer structure with graded Curie temperature, consisting of a hard magnetic layer with high TC and a soft magnetic one with low TC, respectively. To describe the whole write process as realistically as possible, a distribution of the grain sizes and Curie temperatures, a displacement jitter of the head, and the bit positions are considered. For all these cases, we calculate bit error rates of various grain patterns, temperatures, and write head positions to optimize the achievable areal storage density. Within our analysis, shingled HAMR with a continuous laser pulse moving over the medium reaches the best results and thus has the highest potential to become the next-generation storage device.

  5. What limits the achievable areal densities of large aperture space telescopes?

    NASA Astrophysics Data System (ADS)

    Peterson, Lee D.; Hinkle, Jason D.

    2005-08-01

    This paper examines requirements trades involving areal density for large space telescope mirrors. A segmented mirror architecture is used to define a quantitative example that leads to relevant insight about the trades. In this architecture, the mirror consists of segments of non-structural optical elements held in place by a structural truss that rests behind the segments. An analysis is presented of the driving design requirements for typical on-orbit loads and ground-test loads. It is shown that the driving on-orbit load would be the resonance of the lowest mode of the mirror by a reaction wheel static unbalance. The driving ground-test load would be dynamics due to ground-induced random vibration. Two general conclusions are derived from these results. First, the areal density that can be allocated to the segments depends on the depth allocated to the structure. More depth in the structure allows the allocation of more mass to the segments. This, however, leads to large structural depth that might be a significant development challenge. Second, the requirement for ground-test-ability results in an order of magnitude or more depth in the structure than is required by the on-orbit loads. This leads to the proposition that avoiding ground test as a driving requirement should be a fundamental technology on par with the provision of deployable depth. Both are important structural challenges for these future systems.

  6. Assembly of high-areal-density deuterium-tritium fuel from indirectly driven cryogenic implosions.

    PubMed

    Mackinnon, A J; Kline, J L; Dixit, S N; Glenzer, S H; Edwards, M J; Callahan, D A; Meezan, N B; Haan, S W; Kilkenny, J D; Döppner, T; Farley, D R; Moody, J D; Ralph, J E; MacGowan, B J; Landen, O L; Robey, H F; Boehly, T R; Celliers, P M; Eggert, J H; Krauter, K; Frieders, G; Ross, G F; Hicks, D G; Olson, R E; Weber, S V; Spears, B K; Salmonsen, J D; Michel, P; Divol, L; Hammel, B; Thomas, C A; Clark, D S; Jones, O S; Springer, P T; Cerjan, C J; Collins, G W; Glebov, V Y; Knauer, J P; Sangster, C; Stoeckl, C; McKenty, P; McNaney, J M; Leeper, R J; Ruiz, C L; Cooper, G W; Nelson, A G; Chandler, G G A; Hahn, K D; Moran, M J; Schneider, M B; Palmer, N E; Bionta, R M; Hartouni, E P; LePape, S; Patel, P K; Izumi, N; Tommasini, R; Bond, E J; Caggiano, J A; Hatarik, R; Grim, G P; Merrill, F E; Fittinghoff, D N; Guler, N; Drury, O; Wilson, D C; Herrmann, H W; Stoeffl, W; Casey, D T; Johnson, M G; Frenje, J A; Petrasso, R D; Zylestra, A; Rinderknecht, H; Kalantar, D H; Dzenitis, J M; Di Nicola, P; Eder, D C; Courdin, W H; Gururangan, G; Burkhart, S C; Friedrich, S; Blueuel, D L; Bernstein, L A; Eckart, M J; Munro, D H; Hatchett, S P; Macphee, A G; Edgell, D H; Bradley, D K; Bell, P M; Glenn, S M; Simanovskaia, N; Barrios, M A; Benedetti, R; Kyrala, G A; Town, R P J; Dewald, E L; Milovich, J L; Widmann, K; Moore, A S; LaCaille, G; Regan, S P; Suter, L J; Felker, B; Ashabranner, R C; Jackson, M C; Prasad, R; Richardson, M J; Kohut, T R; Datte, P S; Krauter, G W; Klingman, J J; Burr, R F; Land, T A; Hermann, M R; Latray, D A; Saunders, R L; Weaver, S; Cohen, S J; Berzins, L; Brass, S G; Palma, E S; Lowe-Webb, R R; McHalle, G N; Arnold, P A; Lagin, L J; Marshall, C D; Brunton, G K; Mathisen, D G; Wood, R D; Cox, J R; Ehrlich, R B; Knittel, K M; Bowers, M W; Zacharias, R A; Young, B K; Holder, J P; Kimbrough, J R; Ma, T; La Fortune, K N; Widmayer, C C; Shaw, M J; Erbert, G V; Jancaitis, K S; DiNicola, J M; Orth, C; Heestand, G; Kirkwood, R; Haynam, C; Wegner, P J; Whitman, P K; Hamza, A; Dzenitis, E G; Wallace, R J; Bhandarkar, S D; Parham, T G; Dylla-Spears, R; Mapoles, E R; Kozioziemski, B J; Sater, J D; Walters, C F; Haid, B J; Fair, J; Nikroo, A; Giraldez, E; Moreno, K; Vanwonterghem, B; Kauffman, R L; Batha, S; Larson, D W; Fortner, R J; Schneider, D H; Lindl, J D; Patterson, R W; Atherton, L J; Moses, E I

    2012-05-25

    The National Ignition Facility has been used to compress deuterium-tritium to an average areal density of ~1.0±0.1 g cm(-2), which is 67% of the ignition requirement. These conditions were obtained using 192 laser beams with total energy of 1-1.6 MJ and peak power up to 420 TW to create a hohlraum drive with a shaped power profile, peaking at a soft x-ray radiation temperature of 275-300 eV. This pulse delivered a series of shocks that compressed a capsule containing cryogenic deuterium-tritium to a radius of 25-35 μm. Neutron images of the implosion were used to estimate a fuel density of 500-800 g cm(-3).

  7. Development of Lower Energy Neutron Spectroscopy for Areal Density Measurement in Implosion Experiment at NIF and Omega

    SciTech Connect

    Isumi, N; Lerche, R A; Phillips, T W; Schmid, G J; Moran, M J; Sangster, T C

    2001-08-02

    Areal density ({rho}R) is a fundamental parameter that characterizes the performance of an ICF implosion. For high areal densities ({rho}R> 0.1 g/cm{sup 2}), which will be realized in implosion experiments at NIF and LMJ, the target areal density exceeds the stopping range of charged particles and measurements with charged particle spectroscopy will be difficult. In this region, an areal density measurement method using down shifted neutron counting is a promising alternative. The probability of neutron scattering in the imploded plasma is proportional to the areal density of the plasma. The spectrum of neutrons scattered by the specific target nucleus has a characteristic low energy cut off. This enables separate, simultaneous measurements of fuel and pusher {rho}Rs. To apply this concept in implosion experiments, the detector should have extremely large dynamic range. Sufficient signal output for low energy neutrons is also required. A lithium-glass scintillation-fiber plate (LG-SCIFI) is a promising candidate for this application. In this paper we propose a novel technique based on downshifted neutron measurements with a lithium-glass scintillation-fiber plate. The details of instrumentation and background estimation with Monte Carlo calculation are reported.

  8. Because Muncie's Densities Are Not Manhattan's: Using Geographical Weighting in the EM Algorithm for Areal Interpolation

    PubMed Central

    Schroeder, Jonathan P.; Van Riper, David C.

    2014-01-01

    Areal interpolation transforms data for a variable of interest from a set of source zones to estimate the same variable's distribution over a set of target zones. One common practice has been to guide interpolation by using ancillary control zones that are related to the variable of interest's spatial distribution. This guidance typically involves using source zone data to estimate the density of the variable of interest within each control zone. This article introduces a novel approach to density estimation, the geographically weighted expectation-maximization (GWEM) algorithm, which combines features of two previously used techniques, the expectation-maximization (EM) algorithm and geographically weighted regression. The EM algorithm provides a framework for incorporating proper constraints on data distributions, and using geographical weighting allows estimated control-zone density ratios to vary spatially. We assess the accuracy of GWEM by applying it with land-use/land-cover ancillary data to population counts from a nationwide sample of 1980 United States census tract pairs. We find that GWEM generally is more accurate in this setting than several previously studied methods. Because target-density weighting (TDW)—using 1970 tract densities to guide interpolation—outperforms GWEM in many cases, we also consider two GWEM-TDW hybrid approaches, and find them to improve estimates substantially. PMID:24653524

  9. A new neutron time-of-flight detector for fuel-areal-density measurements on OMEGA.

    PubMed

    Glebov, V Yu; Forrest, C J; Marshall, K L; Romanofsky, M; Sangster, T C; Shoup, M J; Stoeckl, C

    2014-11-01

    A new neutron time-of-flight (nTOF) detector for fuel-areal-density measurements in cryogenic DT implosions was installed on the OMEGA Laser System. The nTOF detector has a cylindrical thin-wall, stainless-steel, 8-in.-diam, 4-in.-thick cavity filled with an oxygenated liquid xylene scintillator. Four gated photomultiplier tubes (PMTs) with different gains are used to measure primary DT and D2 neutrons, down-scattered neutrons in nT and nD kinematic edge regions, and to study tertiary neutrons in the same detector. The nTOF detector is located 13.4 m from target chamber center in a well-collimated line of sight. The design details of the nTOF detector, PMT optimization, and test results on OMEGA will be presented.

  10. A new neutron time-of-flight detector for fuel-areal-density measurements on OMEGA

    SciTech Connect

    Glebov, V. Yu. Forrest, C. J.; Marshall, K. L.; Romanofsky, M.; Sangster, T. C.; Shoup, M. J.; Stoeckl, C.

    2014-11-15

    A new neutron time-of-flight (nTOF) detector for fuel-areal-density measurements in cryogenic DT implosions was installed on the OMEGA Laser System. The nTOF detector has a cylindrical thin-wall, stainless-steel, 8-in.-diam, 4-in.-thick cavity filled with an oxygenated liquid xylene scintillator. Four gated photomultiplier tubes (PMTs) with different gains are used to measure primary DT and D{sub 2} neutrons, down-scattered neutrons in nT and nD kinematic edge regions, and to study tertiary neutrons in the same detector. The nTOF detector is located 13.4 m from target chamber center in a well-collimated line of sight. The design details of the nTOF detector, PMT optimization, and test results on OMEGA will be presented.

  11. Sprayable low density ablator and application process

    NASA Technical Reports Server (NTRS)

    Sharpe, M. H.; Hill, W. E.; Simpson, W. G.; Carter, J. M.; Brown, E. L.; King, H. M.; Schuerer, P. H.; Webb, D. D. (Inventor)

    1978-01-01

    A sprayable, low density ablative composition is described consisting esentially of: (1) 100 parts by weight of a mixture of 25-65% by weight of phenolic microballoons, 0-20% by weight of glass microballoons, 4-10% by weight of glass fibers, 25-45% by weight of an epoxy-modified polyurethane resin, 2-4% by weight of a bentonite dispersing aid, and 1-2% by weight of an alcohol activator for the bentonite; (2) 1-10 parts by weight of an aromatic amine curing agent; and (3) 200-400 parts by weight of a solvent.

  12. Monoenergetic Particle backlighter for Radiography and measuring E and B fields and Plasma Areal density

    NASA Astrophysics Data System (ADS)

    Petrasso, R. D.; Li, C. K.; Séguin, F. H.; Frenje, J. A.; Rygg, J. R.; Manuel, M.; Smalyuk, V.; Betti, R.; Craxton, S.; Knauer, J. P.; Marshall, F. J.; Meyerhofer, D. D.; Myatt, J.; Radha, P. B.; Sangster, T. C.; Theobald, W.; Town, R. P. J.; Amendt, P.; Celliers, P.; Hatchett, S.; Hicks, D.; Landen, O.; MacKinnon, A.; Patel, P.; Tabak, M.

    2006-10-01

    J.COBBLE, N.M. HOFFMAN, G.A. KYRALA, D.C. WILSON, LANL; R. STEPHENS, J. KILKENNY, GA--A novel monoenergetic particle backlighter source (14.7 and 3.0 MeV P, 3.5 and 0.8 MeV α, and 1.0 MeV T), has been utilized at OMEGA to quantitatively measure the evolution of electric (E) and magnetic (B) fields generated by laser-plasma interactions, and will be utilized in the near future to radiograph plasmas and fields generated from fast ignitor implosions, magnetic compression experiments, magnetized foil experiments, hohlraums and, more generally, from 2- and 3-D laser-plasmas. The backlighter consists of an exploding-pusher glass micro-balloon, filled with D^3He, in which a fraction of the OMEGA 60-beams are used to drive the implosion. The width of the spectral line, ˜ 3%, is determined by the burn temperature (˜ 10 keV); the monoenergetic character, as well as multiple particles, enables unique discrimination between E and B fields; it further allows for the probing of cold (warm) plasmas with areal densities of order 1 (10) to 200 (1000) mg/cm**2. New results and planned experiments will be presented.

  13. Diverging results of areal and volumetric bone mineral density in Down syndrome.

    PubMed

    García-Hoyos, M; García-Unzueta, M T; de Luis, D; Valero, C; Riancho, J A

    2017-03-01

    Population with Down syndrome (DS) has lower areal BMD, in association with their smaller skeletal size. However, volumetric BMD and other indices of bone microarchitecture, such as trabecular bone score (TBS) and calcaneal ultrasound (QUS), were normal.

  14. Fracture Risk and Areal Bone Mineral Density in Adolescent Females with Anorexia Nervosa

    PubMed Central

    Faje, Alexander T.; Fazeli, Pouneh K.; Miller, Karen K.; Katzman, Debra K.; Ebrahimi, Seda; Lee, Hang; Mendes, Nara; Snelgrove, Deirdre; Meenaghan, Erinne; Misra, Madhusmita; Klibanski, Anne

    2014-01-01

    Objective To (i) compare fracture prevalence in adolescent females with anorexia nervosa (AN) vs. normal-weight controls and (ii) examine whether reductions in areal bone mineral density (aBMD) predict fracture risk in females with AN. Methods 418 females (310 with active AN and 108 normal-weight controls) 12–22 years old were studied cross-sectionally. Lifetime fracture history was recorded by a physician during participant interviews. Body composition and aBMD measurements of the whole body, whole body less head, lumbar spine, and hip were assessed by dual-energy x-ray absorptiometry (DXA), and bone mineral apparent density (BMAD) was calculated for the lumbar spine. Results Participants with AN and normal-weight controls did not differ for chronological age, sexual maturity, or height. The lifetime prevalence of prior fracture was 59.8% higher in those with AN compared to controls (31.0 % versus 19.4 %, p = 0.02), and the fracture incidence rate peaked in our cohort after the diagnosis of AN. Lower aBMD and lumbar BMAD were not associated with a higher prevalence of fracture in the AN or control group on univariate or multivariate analyses. Compared to controls, fracture prevalence was significantly higher in the subgroup of girls with AN who had normal aBMD or only modest reductions of aBMD (Z-scores > −1 or −1.5). Discussion This is the first study to show that the risk of fracture during childhood and adolescence is significantly higher in patients with AN than in normal-weight controls. Fracture prevalence is increased in this cohort of subjects with AN even without significant reductions in aBMD. PMID:24430890

  15. A CAD-compatible closed form approximation for the inversion charge areal density in double-gate MOSFETs

    NASA Astrophysics Data System (ADS)

    Hariharan, Venkatnarayan; Vasi, Juzer; Ramgopal Rao, V.

    2009-02-01

    In developing the drain current model of a symmetrically driven, undoped (or lightly doped) symmetric double-gate MOSFET (SDGFET), one encounters a transcendental equation relating the value of an intermediate variable β (which is related to the inversion charge areal density and also surface-potential) to the gate and drain voltages; as a result, it doesn't have a closed form solution. From a compact modeling perspective, it is desirable to have closed form expressions in order to implement them in a circuit simulator. In this paper, we present an accurate closed form approximation for the inversion charge areal density, based on the Lambert-W function. We benchmark our approximation against other existing approximations and show that our approximation is computationally the most efficient and numerically the most robust, at a reduced but acceptable accuracy. Hence, it is suitable for use in implementing inversion charge based compact models.

  16. On a novel graded areal density solution to facilitate ramp wave generation in plate-impact studies

    NASA Astrophysics Data System (ADS)

    Painter, J. D.; Fitzmaurice, B. C.; Goff, M.; Appleby-Thomas, G. J.; Wood, D. C.; Pinto, T.

    2017-01-01

    Building on a substantial body of work on functionally graded materials in the literature, it has been previously shown that the use of graded areal density impactors, in conjunction with buffer materials, allows generation of ramp-wave loading profiles in impacted targets. Such off-principle-Hugoniot loading paths are of particular interest where control of one or more state variables (e.g. temperature) is desirable during the loading event. Previous attempts to produce suitable graded areal density impactors have focused on rapid prototyping techniques such as 3D printing. While suitable for small-scale production of impactors, such technologies are relatively immature. Instead, here a novel approach to creating graded areal density structures - TWI Ltd.'s novel surface modification process, Surfi-Sculpt®, with a nominal surface spike distribution of 1.5 per mm2, has been employed to produce the required impactors. Initial experimental results are presented highlighting the potential of this experimental approach; further, these results -combined with basic hydrocode simulations - are used to postulate idealised structures which would allow useful loading paths such as the Adiabat to be readily accessed.

  17. Areal Crater Density Analysis of Volcanic Smooth Plains: A New Approach to Distinguishing Age Units

    NASA Astrophysics Data System (ADS)

    Ostrach, L. R.; Robinson, M. S.

    2013-12-01

    It is well documented that the lunar maria were emplaced over an extended period of time [e.g., 1-3], and mare units exhibit significant color differences in multispectral data that are interpreted to correlate with distinct mineralogical compositions and ages [e.g., 3-7]. Areal crater density (ACD) analysis is used as a novel approach to identify resurfacing boundaries within Mare Imbrium as a test case for mercurian studies. Absolute model age dating and measures of ACD from crater counts on Lunar Reconnaissance Orbiter Wide Angle Camera (LRO WAC) mosaics reveal two spatially expansive, statistically separable units in Mare Imbrium. The older, spectrally red unit (~15-18 wt% FeO, ~2-5 wt% TiO2 [8]) in the east is ~3.3 Ga, and the younger, spectrally blue unit (~17-20 wt% FeO, ~7-10 wt% TiO2 [8]) in the west is ~2.2 Ga. ACD measurements show a regional boundary at the contact between these two regions. The geologic contact is confidently observed in ACD maps derived for regions with model age differences >300-500 million years and spatial extents >1 × 104 km2. The older, spectrally red unit exhibits higher ACD (>35000 craters with diameters ≥500 m per 106 km2) and the younger, spectrally blue unit has a lower ACD (<26000 craters with diameters ≥500 m per 106 km2); the absolute model ages and ACD results agree with other dating studies of this region [5, 9-12]. Thus, ACD measurements provide a reliable technique to distinguish relative ages among geologic units as well as a means to explore the statistical significance of published absolute model ages. Moreover, the ability to distinguish surface units of different ages from measures of crater frequencies in Mare Imbrium, when spectral information is not available or units do not exhibit spectral contrasts, shows that the ACD technique may be applied to other planetary bodies to search for age boundaries within contiguous smooth plains units. For example, multispectral differences within volcanic units (age

  18. The temperature and electromagnetic field distributions of heat-assisted magnetic recording for bit-patterned media at ultrahigh areal density

    NASA Astrophysics Data System (ADS)

    Pituso, K.; Kaewrawang, A.; Buatong, P.; Siritaratiwat, A.; Kruesubthaworn, A.

    2015-05-01

    In this paper, the temperature and electromagnetic field distributions for bit-patterned media (BPM) with heat-assisted writing technology at areal density of 6.54-17.92 Tb/in2 are investigated by the finite integral technique method. We have found that the BPM can confine temperature better than continuous media. The temperature ratio of neighbor bits to heating bit of BPM at areal density of 6.54-7.69 Tb/in2 is lower than 65% and increases with increasing areal density. The electric field direction is toward the bit and the magnetic field circulates around the heating bit. In addition, the electric field of BPM is the same pattern as continuous media at areal density of 13.17 Tb/in2 or above.

  19. Development of Low Density, Flexible Carbon Phenolic Ablators

    NASA Technical Reports Server (NTRS)

    Stackpoole, Mairead; Thornton, Jeremy; Fan, Wendy; Covington, Alan; Doxtad, Evan; Beck, Robin; Gasch, Matt; Arnold, Jim

    2012-01-01

    Phenolic Impregnated Carbon Ablator (PICA) was the enabling TPS material for the Stardust mission where it was used as a single piece heatshield. PICA has the advantages of low density (approximately 0.27 grams per cubic centimeter) coupled with efficient ablative capability at high heat fluxes. Due to its brittle nature and low strain to failure recent efforts at NASA ARC have focused on alternative architectures to yield flexible and more conformal carbon phenolic materials with comparable densities to PICA. This presentation will discuss flexible alternatives to PICA and include preliminary mechanical and thermal properties as well as recent arc jet and LHMEL screening test results.

  20. Demonstration of the highest deuterium-tritium areal density using multiple-picket cryogenic designs on OMEGA.

    PubMed

    Goncharov, V N; Sangster, T C; Boehly, T R; Hu, S X; Igumenshchev, I V; Marshall, F J; McCrory, R L; Meyerhofer, D D; Radha, P B; Seka, W; Skupsky, S; Stoeckl, C; Casey, D T; Frenje, J A; Petrasso, R D

    2010-04-23

    The performance of triple-picket deuterium-tritium cryogenic target designs on the OMEGA Laser System [T. R. Boehly, Opt. Commun. 133, 495 (1997)] is reported. These designs facilitate control of shock heating in low-adiabat inertial confinement fusion targets. Areal densities up to 300 mg/cm2 (the highest ever measured in cryogenic deuterium-tritium implosions) are inferred in the experiments with an implosion velocity approximately 3x10(7) cm/s driven at peak laser intensities of 8x10(14) W/cm2. Extension of these designs to ignition on the National Ignition Facility [J. A. Paisner, Laser Focus World 30, 75 (1994)] is presented.

  1. 10B areal density: A novel approach for design and fabrication of B4C/6061Al neutron absorbing materials

    NASA Astrophysics Data System (ADS)

    Li, Yuli; Wang, Wenxian; Zhou, Jun; Chen, Hongsheng; Zhang, Peng

    2017-04-01

    In this paper, a novel approach to evaluate the neutron shielding performance of a boron-containing neutron absorbing material was proposed for the first time through the establishment of a direct relationship between 10B areal density (10BAD) of the material and its neutron absorption ratio. It is found when the 10BAD of a material is greater than 0.034 g/cm2, the material will achieve a good neutron shielding performance. Based on this proposed approach, B4C/6061Al composite plates with different B4C content (10 wt%, 20 wt%, 30 wt%) were successfully fabricated using vacuum hot pressing followed by hot-extrusion. The characteristics of the B4C/Al interface were studied in details using transmission electron microscopy (TEM), and the effects of B4C particle content on microstructure and mechanical properties of the Al matrix were investigated. Through current studies, B4C/6061Al composite plates possessing good neutron shielding performance and tensile strength are found to be able to be fabricated using either 20 wt% of B4C content with a plate thickness of 4.5 mm or 30 wt% B4C content with a plate thickness of 3 mm.

  2. Adjusting the surface areal density of click-reactive azide groups by kinetic control of the azide substitution reaction on bromine-functional SAMs.

    PubMed

    Zhang, Shuo; Maidenberg, Yanir; Luo, Kai; Koberstein, Jeffrey T

    2014-06-03

    Azide-alkyne click chemistry has emerged as an important and versatile means for tethering a wide variety of guest molecules to virtually any substrate. In many of these applications, it is important to exercise control over the areal density of surface functional groups to achieve a desired areal density of the tethered guest molecule of interest. We demonstrate herein that the areal density of surface azide groups on flat germanium surfaces and nanoparticle substrates (silica and iron oxide) can be controlled kinetically by appropriately timed quenching of the S(N)2 substitution reaction of bromo-alkane-silane monolayers induced by the addition of sodium azide. The kinetics of the azide substitution reaction on monolayers formed on flat Ge substrates, determined by attenuated total reflection infrared spectroscopy (ATR-IR), are found to be identical to those for monolayers formed on both silica and iron oxide nanoparticles, the latter determined by transmission infrared spectroscopy. To validate the method, the percentages of surface bromine groups converted to azide groups after various reaction times were measured by quenching the S(N)2 reaction followed by analysis with ATR-IR (for Ge) and thermogravimetric analysis (after a subsequent click reaction with an alkyne-terminal polymer) for the nanoparticle substrates. The conversions found after quenching agree well with those expected from the standard kinetic curves. The latter result suggests that the kinetic method for the control of azide group areal density is a versatile means for functionalizing substrates with a prescribed areal density of azide groups for subsequent click reactions, and that the method is universal for any substrate, flat or nanoparticle, that can be modified with bromo-alkane-silane monolayers. Regardless of the surface geometry, we find that the azide substitution reaction is complete within 2-3 h, in sharp contrast to previous reports that indicate times of 48-60 h required for

  3. Anthropometric models of bone mineral content and areal bone mineral density based on the bone mineral density in childhood study

    PubMed Central

    Gilsanz, V.; Kalkwarf, H. J.; Lappe, J. M.; Oberfield, S.; Shepherd, J. A.; Winer, K. K.; Zemel, B. S.; Hangartner, T. N.

    2016-01-01

    Summary New models describing anthropometrically adjusted normal values of bone mineral density and content in children have been created for the various measurement sites. The inclusion of multiple explanatory variables in the models provides the opportunity to calculate Z-scores that are adjusted with respect to the relevant anthropometric parameters. Introduction Previous descriptions of children’s bone mineral measurements by age have focused on segmenting diverse populations by race and sex without adjusting for anthropometric variables or have included the effects of a single anthropometric variable. Methods We applied multivariate semi-metric smoothing to the various pediatric bone-measurement sites using data from the Bone Mineral Density in Childhood Study to evaluate which of sex, race, age, height, weight, percent body fat, and sexual maturity explain variations in the population’s bone mineral values. By balancing high adjusted R2 values with clinical needs, two models are examined. Results At the spine, whole body, whole body sub head, total hip, hip neck, and forearm sites, models were created using sex, race, age, height, and weight as well as an additional set of models containing these anthropometric variables and percent body fat. For bone mineral density, weight is more important than percent body fat, which is more important than height. For bone mineral content, the order varied by site with body fat being the weakest component. Including more anthropometrics in the model reduces the overlap of the critical groups, identified as those individuals with a Z-score below −2, from the standard sex, race, and age model. Conclusions If body fat is not available, the simpler model including height and weight should be used. The inclusion of multiple explanatory variables in the models provides the opportunity to calculate Z-scores that are adjusted with respect to the relevant anthropometric parameters. PMID:25311106

  4. Shell stability and conditions analyzed using a new method of extracting shell areal density maps from spectrally resolved images of direct-drive inertial confinement fusion implosions

    DOE PAGES

    Johns, H. M.; Mancini, R. C.; Nagayama, T.; ...

    2016-01-25

    In warm target direct-drive ICF implosion experiments performed at the OMEGA laser facility, plastic microballoons doped with a titanium tracer layer in the shell and filled with deuterium gas were imploded using a low-adiabat shaped laser pulse. Continuum radiation emitted in the core is transmitted through the tracer layer and the resulting spectrum recorded with a gated multi-monochromatic x-ray imager (MMI). Titanium K-shell line absorption spectra observed in the data are due to transitions in L-shell titanium ions driven by the backlighting continuum. The MMI data consist of an array of spectrally resolved images of the implosion. These 2-D space-resolvedmore » titanium spectral features constrain the plasma conditions and areal density of the titanium doped region of the shell. The MMI data were processed to obtain narrow-band images and space resolved spectra of titanium spectral features. Shell areal density maps, ρL(x,y), extracted using a new method using both narrow-band images and space resolved spectra are confirmed to be consistent within uncertainties. We report plasma conditions in the titanium-doped region of electron temperature (Te) = 400±28eV, electron number density (Ne) = 8.5x1024±2.5x1024 cm-3, and average areal density <ρR> = 86±7mg/cm2. Fourier analysis of areal density maps reveals shell modulations caused by hydrodynamic instability growth near the fuel-shell interface in the deceleration phase. We observe significant structure in modes l = 2-9, dominated by l = 2. We extract a target breakup fraction of 7.1±1.5% from our Fourier analysis. A new method for estimating mix width is evaluated against existing literature and our target breakup fraction. We estimate a mix width of 10.5±1μm.« less

  5. Areal power density: A preliminary examination of underground heat transfer in a potential Yucca Mountain repository and recommendations for thermal design approaches; Yucca Mountain Site Characterization Project

    SciTech Connect

    Hertel, E.S. Jr.; Ryder, E.E.

    1991-11-01

    The design of the potential Yucca Mountain repository is subject to many thermal goals related to the compliance of the site with federal regulations. This report summarizes a series of sensitivity studies that determined the expected temperatures near the potential repository. These sensitivity studies were used to establish an efficient loading scheme for the spent fuel canisters and a maximum areal power density based strictly on thermal goals. Given the current knowledge of the site, a design-basis areal power density of 80 kW/acre can be justified based on thermal goals only. Further analyses to investigate the impacts of this design-basis APD on mechanical and operational aspects of the potential repository must be undertaken before a final decision is made.

  6. Image and Radiation Power Analysis Techniques for Determining Electron temperature, Liner Areal Density, and Radiated Energy in MagLIF Experiments

    NASA Astrophysics Data System (ADS)

    Evans, Matthew; Knapp, Patrick; Gomez, Matthew; Hansen, Stephanie; McBride, Ryan; MacPherson, L. Armon; Gourdain, Pierre

    2016-10-01

    We describe techniques developed to analyze filtered Time Integrated Pinhole Camera (TIPC) images to determine the axially resolved electron temperature and liner areal density at stagnation in MagLIF experiments conducted on the Z machine at Sandia National Laboratories. X-ray power detectors are analyzed to determine the absolute radiated energy. The TIPC images are co-registered using intensity based similarities. This technique is shown to provide accurate registration without the use of fiducial markings. A filtered 6-channel PCD array was used to record the radiated power at photon energies >1 keV. A model for the x-ray emission is used with the data set to perform Bayesian parameter estimation to simultaneously determine the electron temperature, liner areal density and x-ray yield with uncertainties via χ2 minimization.

  7. Development of Low Density Flexible Carbon Phenolic Ablators

    NASA Technical Reports Server (NTRS)

    Stackpole, Mairead; Thornton, Jeremy; Fan, Wendy; Agrawal, Parul; Doxtad, Evan; Gasch, Matt

    2011-01-01

    Phenolic Impregnated Carbon Ablator (PICA) was the enabling TPS material for the Stardust mission where it was used as a single piece heatshield. PICA has the advantages of low density (0.27g/cm3) coupled with efficient ablative capability at high heat fluxes. Under the Orion program, PICA was also shown to be capable of both ISS and lunar return missions however some unresolved issues remain for its application in a tiled configuration for the Orion-specific design. In particular, the problem of developing an appropriate gap filler resulted in the Orion program selecting AVCOAT as the primary heatshield material over PICA. We are currently looking at alternative architectures to yield flexible and more conformal carbon phenolic materials with comparable densities to PICA that will address some of the design issues faced in the application of a tiled PICA heat shield. These new materials are viable TPS candidates for upcoming NASA missions and as material candidates for private sector Commercial Orbital Transportation Services (COTS). This presentation will discuss flexible alternatives to PICA and include preliminary mechanical and thermal properties as well as arc jet and LHMEL screening test results.

  8. Tracking areal lithium densities from neutron activation - quantitative Li determination in self-organized TiO2 nanotube anode materials for Li-ion batteries.

    PubMed

    Portenkirchner, E; Neri, G; Lichtinger, J; Brumbarov, J; Rüdiger, C; Gernhäuser, R; Kunze-Liebhäuser, J

    2017-03-28

    Nanostructuring of electrode materials is a promising approach to enhance the performance of next-generation, high-energy density lithium (Li)-ion batteries. Various experimental and theoretical approaches allow for a detailed understanding of solid-state or surface-controlled reactions that occur in nanoscaled electrode materials. While most techniques which are suitable for nanomaterial investigations are restricted to analysis widths of the order of Å to some nm, they do not allow for characterization over the length scales of interest for electrode design, which is typically in the order of mm. In this work, three different self-organized anodic titania nanotube arrays, comprising as-grown amorphous titania nanotubes, carburized anatase titania nanotubes, and silicon coated carburized anatase titania nanotubes, have been synthesized and studied as model composite anodes for use in Li-ion batteries. Their 2D areal Li densities have been successfully reconstructed with a sub-millimeter spatial resolution over lateral electrode dimensions of 20 mm exploiting the (6)Li(n,α)(3)H reaction, in spite of the extremely small areal Li densities (10-20 μg cm(-2) Li) in the nanotubular active material. While the average areal Li densities recorded via triton analysis are found to be in good agreement with the electrochemically measured charges during lithiation, triton analysis revealed, for certain nanotube arrays, areas with a significantly higher Li content ('hot spots') compared to the average. In summary, the presented technique is shown to be extremely well suited for analysis of the lithiation behavior of nanostructured electrode materials with very low Li concentrations. Furthermore, identification of lithiation anomalies is easily possible, which allows for fundamental studies and thus for further advancement of nanostructured Li-ion battery electrodes.

  9. Density Profile of a Foil Accelerated by Laser Ablation

    NASA Astrophysics Data System (ADS)

    Knauer, J. P.; Hu, S. X.; Goncharov, V. N.; Haberberger, D.

    2016-10-01

    An experiment to measure the density profile of a foil accelerated by laser ablation has been designed and is underway. High-density material is measured with x-ray radiography and low-density plasma is measured using 251-nm interferometry. Two-dimensional hydrodynamic simulation results from the code DRACO will be compared to these data. The accelerated foil is an 80- μm-thick CH target with Ge and Si-doped layers. The incident laser is a 351-nm, 5-ns pulse with a total energy of 6.2 kJ. Si and Ti x rays are used for the radiography measurement. A 1-D image versus time data are recorded with an x-ray streak camera and 2-D image data at specific times are recorded with an x-ray framing camera using point-projection backlighting. Foil acceleration is measured with the 1-D data. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  10. Shell stability and conditions analyzed using a new method of extracting shell areal density maps from spectrally resolved images of direct-drive inertial confinement fusion implosions

    SciTech Connect

    Johns, H. M.; Mancini, R. C.; Nagayama, T.; Mayes, D. C.; Tommasini, R.; Smalyuk, V. A.; Regan, S. P.; Delettrez, J. A.

    2016-01-25

    In warm target direct-drive ICF implosion experiments performed at the OMEGA laser facility, plastic microballoons doped with a titanium tracer layer in the shell and filled with deuterium gas were imploded using a low-adiabat shaped laser pulse. Continuum radiation emitted in the core is transmitted through the tracer layer and the resulting spectrum recorded with a gated multi-monochromatic x-ray imager (MMI). Titanium K-shell line absorption spectra observed in the data are due to transitions in L-shell titanium ions driven by the backlighting continuum. The MMI data consist of an array of spectrally resolved images of the implosion. These 2-D space-resolved titanium spectral features constrain the plasma conditions and areal density of the titanium doped region of the shell. The MMI data were processed to obtain narrow-band images and space resolved spectra of titanium spectral features. Shell areal density maps, ρL(x,y), extracted using a new method using both narrow-band images and space resolved spectra are confirmed to be consistent within uncertainties. We report plasma conditions in the titanium-doped region of electron temperature (Te) = 400±28eV, electron number density (Ne) = 8.5x1024±2.5x1024 cm-3, and average areal density <ρR> = 86±7mg/cm2. Fourier analysis of areal density maps reveals shell modulations caused by hydrodynamic instability growth near the fuel-shell interface in the deceleration phase. We observe significant structure in modes l = 2-9, dominated by l = 2. We extract a target breakup fraction of 7.1±1.5% from our Fourier analysis. A new method for estimating mix width is evaluated against existing literature and our target breakup fraction. We estimate a mix width of 10.5±1μm.

  11. Ultimate fracture load of cadaver proximal humeri correlates more strongly with mean combined cortical thickness than with areal cortical index, DEXA density, or canal-to-calcar ratio

    PubMed Central

    Mears, C. S.; Burkhead, W. Z.

    2017-01-01

    Objectives This investigation sought to advance the work published in our prior biomechanical study (Journal of Orthopaedic Research, 2016). We specifically sought to determine whether there are additional easy-to-measure parameters on plain radiographs of the proximal humerus that correlate more strongly with ultimate fracture load, and whether a parameter resembling the Dorr strength/quality characterisation of proximal femurs can be applied to humeri. Materials and Methods A total of 33 adult humeri were used from a previous study where we quantified bone mineral density of the proximal humerus using radiographs and dual-energy x-ray absorptiometry (DEXA), and regional mean cortical thickness and cortical index using radiographs. The bones were fractured in a simulated backwards fall with the humeral head loaded at 2 mm/second via a frustum angled at 30° from the long axis of the bone. Correlations were assessed with ultimate fracture load and these new parameters: cortical index expressed in areas (“areal cortical index”) of larger regions of the diaphysis; the canal-to-calcar ratio used analogous to its application in proximal femurs; and the recently described medial cortical ratio. Results The three new parameters showed the following correlations with ultimate fracture load: areal cortical index (r = 0.56, p < 0.001); canal-to-calcar ratio (r = 0.38, p = 0.03); and medial cortical ratio (r = 0.49, p < 0.005). These correlations were weaker when compared with those that we previously reported: mean cortical thickness of the proximal diaphysis versus ultimate fracture load (r = 0.71; p < 0.001); and mean density in the central humeral head versus ultimate fracture load (r = 0.70; p < 0.001). Conclusion Simple-to-measure radiographic parameters of the proximal humerus reported previously are more useful in predicting ultimate fracture load than are areal cortical index, canal-to-calcar ratio, and medial cortical ratio. Cite this article: J. G. Skedros, C

  12. Studying areal density evolution in D-3He implosions at the National Ignition Facility using pTOF-measured shock- and compression-bang times and WRF-measured shock and compression ρR

    NASA Astrophysics Data System (ADS)

    Kabadi, N.; Sio, H.; Lahmann, B.; Frenje, J. A.; Gatu Johnson, M.; Seguin, F. H.; Petrasso, R. D.; Rinderknecht, H. G.; Berzak-Hopkins, L.; Meezan, N.; Casey, D. T.; Baker, K.; Khan, S.; Thomas, C. A.; Spears, B. K.; Barbosa, F.; Bionta, R. M.; Zylstra, A.; Kilkenny, J. D.; Sangster, T. C.

    2016-10-01

    Understanding the time evolution of inertial confinement fusion (ICF) experiments is critical for making further improvements on the road to ignition. In an ICF implosion at the National Ignition Facility (NIF) shocks are launched into the ablator by a laser pulse. These shocks coalesce at the fuel-shell interface and then converge at the center of the implosion which causes significant heating and a period of nuclear burn (``shock phase''), followed by a compression phase due to the imploding shell. The particle-time-of-flight (pTOF) and the magnetic particle-time-of-flight (magPTOF) detectors were developed to measure both the shock and compression bang-times in NIF D-3He implosions. These timing measurements in combination with shock and compression areal densities (ρR) from wedge range filters (WRFs) provide a direct measurement of ρR evolution, which can be used to guide theory and heavily constrain simulations. This presentation shows a first analysis of ρR evolution from shock phase to compression phase in a variety of NIF implosions as measured by pTOF and WRFs. This work was supported in part by LLE, the U.S. DoE (NNSA, NLUF) and LLNL.

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

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

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

  14. Ignition relevant ablator response of boron carbide and high-density carbon driven by multiple shocks

    NASA Astrophysics Data System (ADS)

    Prisbrey, Shon T.; Baker, Kevin; Celliers, Peter; Dittrich, Tom; Moore, Alastair; Wu, Kuang Jen; Kervin, Peggy; Hurricane, Omar

    2013-10-01

    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 current ablation material, 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. In an effort to evaluate the performance of other possible ablators that could be suitable for achieving self-propagating fusion burn we have inferred the ablation performance of two possible ablators, boron carbide and high-density carbon, by measuring the shock speed of induced shocks while subjecting the ablators to a multiple-shock inducing radiation drive environment similar to a generic three-shock ignition drive. We present the platform used, velocity measurements used to infer the ablation response, and matching simulations to show the relative performance of boron carbide and high-density carbon with a general comparison to current performance of the currently used glow-discharge polymer ablator. 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. LLNL-ABS-640519.

  15. Areal Average Albedo (AREALAVEALB)

    DOE Data Explorer

    Riihimaki, Laura; Marinovici, Cristina; Kassianov, Evgueni

    2008-01-01

    he Areal Averaged Albedo VAP yields areal averaged surface spectral albedo estimates from MFRSR measurements collected under fully overcast conditions via a simple one-line equation (Barnard et al., 2008), which links cloud optical depth, normalized cloud transmittance, asymmetry parameter, and areal averaged surface albedo under fully overcast conditions.

  16. Streaked radiography measurements of convergent ablator performance (invited)

    SciTech Connect

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

    2010-10-15

    The velocity and remaining ablator mass of an imploding capsule are critical metrics for assessing the progress toward ignition of an inertially confined fusion experiment. These and other ablator rocket parameters have been measured using a single streaked x-ray radiograph. A regularization technique has been used to determine the ablator density profile {rho}(r) at each time step; moments of {rho}(r) then provide the areal density, average radius, and mass of the unablated, or remaining, ablator material, with the velocity determined from the time derivative of the average radius. The technique has been implemented on experiments at the OMEGA laser facility.

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

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

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

  18. Using secondary nuclear products for inferring the fuel areal density, convergence, and electron temperatures of deuterium filled implosions on the NIF

    NASA Astrophysics Data System (ADS)

    Lahmann, B.; Frenje, J. A.; Gatu Johnson, M.; Sio, H.; Kabadi, N. V.; Sutcliffe, G.; Seguin, F. H.; Li, C. K.; Petrasso, R. D.; Hartouni, E. P.; Rinderknecht, H. G.; Sayre, D. B.; Yeamans, C. B.; Khan, S. F.; Kyrala, G. A.; Lepape, S.; Berzak-Hopkins, L.; Meezan, N.; Bionta, R.; Ma, T.

    2016-10-01

    In deuterium-filled inertial confinement fusion implosions, 0.82 MeV 3He and 1.01 MeV T born from the primary DD reaction branches can undergo fusion reactions with the thermal deuterium plasma to create secondary D3He protons and DT neutrons respectively. In regimes of moderate fuel areal density (ρR 5 - 100 mg/cm2) the ratio of both of these secondary yields to the primary yield can be used to infer the fuel ρR, convergence, and an electron temperature (Te) simultaneously. This technique has been used on a myriad of deuterium filled implosion experiments on the NIF using the nuclear time of flight (NTOF) diagnostics to measure the secondary DT neutrons and CR-39 based wedge range filters (WRFs) to measure the secondary D3He protons. Additionally, a comparative study is conducted between the nuclear inferred convergence and x-ray inferred convergence obtained on these experiments. This work was supported in part by LLE, the U.S. DoE (NNSA, NLUF) and LLNL.

  19. Characterisation of a MeV Bremsstrahlung x-ray source produced from a high intensity laser for high areal density object radiography

    NASA Astrophysics Data System (ADS)

    Courtois, C.; Edwards, R.; Compant La Fontaine, A.; Aedy, C.; Bazzoli, S.; Bourgade, J. L.; Gazave, J.; Lagrange, J. M.; Landoas, O.; Dain, L. Le; Mastrosimone, D.; Pichoff, N.; Pien, G.; Stoeckl, C.

    2013-08-01

    Results of an experiment to characterise a MeV Bremsstrahlung x-ray emission created by a short (<10 ps) pulse, high intensity (1.4 × 1019 W/cm2) laser are presented. X-ray emission is characterized using several diagnostics; nuclear activation measurements, a calibrated hard x-ray spectrometer, and dosimeters. Results from the reconstructed x-ray energy spectra are consistent with numerical simulations using the PIC and Monte Carlo codes between 0.3 and 30 MeV. The intense Bremsstrahlung x-ray source is used to radiograph an image quality indicator (IQI) heavily filtered with thick tungsten absorbers. Observations suggest that internal features of the IQI can be resolved up to an external areal density of 85 g/cm2. The x-ray source size, inferred by the radiography of a thick resolution grid, is estimated to be approximately 400 μm (full width half maximum of the x-ray source Point Spread Function).

  20. Characterisation of a MeV Bremsstrahlung x-ray source produced from a high intensity laser for high areal density object radiography

    SciTech Connect

    Courtois, C.; Compant La Fontaine, A.; Bazzoli, S.; Bourgade, J. L.; Gazave, J.; Lagrange, J. M.; Landoas, O.; Dain, L. Le; Pichoff, N.; Edwards, R.; Aedy, C.; Mastrosimone, D.; Pien, G.; Stoeckl, C.

    2013-08-15

    Results of an experiment to characterise a MeV Bremsstrahlung x-ray emission created by a short (<10 ps) pulse, high intensity (1.4 × 10{sup 19} W/cm{sup 2}) laser are presented. X-ray emission is characterized using several diagnostics; nuclear activation measurements, a calibrated hard x-ray spectrometer, and dosimeters. Results from the reconstructed x-ray energy spectra are consistent with numerical simulations using the PIC and Monte Carlo codes between 0.3 and 30 MeV. The intense Bremsstrahlung x-ray source is used to radiograph an image quality indicator (IQI) heavily filtered with thick tungsten absorbers. Observations suggest that internal features of the IQI can be resolved up to an external areal density of 85 g/cm{sup 2}. The x-ray source size, inferred by the radiography of a thick resolution grid, is estimated to be approximately 400 μm (full width half maximum of the x-ray source Point Spread Function)

  1. Hook spectroscopy as an atomic number density diagnostic applied to laser-ablated copper plasmas

    SciTech Connect

    Zerkle, D.K.; Sappey, A.D.; Gamble, T.K.

    1993-11-01

    Hook spectroscopy has been used to determine the absolute number density of ground state copper atoms in laser-ablated plasma plumes. An ablation laser power flux of {approximately} 1.5 GW/cm{sup 2} is applied to a solid copper target in a background gas, producing a plasma plume suitable for studying homogeneous copper vapor condensation. Density is measured at post-ablation time delays ranging from 10 {mu}s to 3 ms with 25 torr of argon as the background gas. Planar laser-induced fluorescence (PLEF) images containing relative density information are used in conjunction with the hook spectra to resolve spatially the absolute density within the plume. Copper atom densities thus measured ranged from 1.9 {times} 10{sup 15} cm{sup {minus}3} at a delay of 10 {mu}s to 2.7 {times} 10{sup 13} cm{sup {minus}3} at 3 ms delay in 25 torr of argon The decrease in density is due to the condensation of copper vapor to form fine particulate. As a combustion diagnostic, the hook method may prove extremely useful for the determination of metal impurity density in coal fired flames as well as a single -- shot OH density and temperature diagnostic.

  2. Spatial and Temporal Investigations of Laser Ablation Plasma Plume Density and Composition

    NASA Astrophysics Data System (ADS)

    Iratcabal, Jeremy; Bach, Bernhard; Beatty, Cuyler; Dutra, Eric; Darling, Timothy; Wiewior, Piotr; Covington, Aaron

    2016-10-01

    Laser ablation of solid targets with laser intensities of the order of 108-1011 W/cm2 provides a rich platform for investigating the density and composition of coexisting molecular, atomic, and ion species in the resulting plasma plume. Experiments measuring the spatial- and temporal-evolution of laser ablation plumes have been performed to simultaneously characterize the multiple parameters related to the energy and momentum partitioning of the incident laser energy as the ablation process occurs. The temperature, density, and relative populations of different molecular, atomic, and ion species can be determined by the simultaneous measurement of optical and charged particle spectroscopy, fast imaging cameras, and optical interferometric diagnostics. Additionally, background gas pressure, density, and species were carefully varied. A comparison of density measurements obtained with multiple interferometric, spectroscopic, and fast imaging diagnostics for a carbon ablation plume expanding into vacuum and into background gases with different Reynolds numbers will be presented. Atomic, molecular, and ion species population evolution will be presented as measured with optical and charged particle spectroscopy. This work was supported by the U.S. DOE NNSA Cooperative Agreement No. DE-NA0002075 and National Securities Technologies, LLC under Contract No. DE-AC52-06NA25946/subcontract No. 165819.

  3. Capsule Areal-Density Asymmetries and Time Evolution Inferred from 14.7-MeV Proton Line Structure in OMEGA D^3He Implosions

    NASA Astrophysics Data System (ADS)

    Li, C. K.

    2002-11-01

    The fusion of D^3He in spherical capsule implosions results in copious production of 14.7-MeV protons. As these protons pass through the plasma, they lose energy. Importantly, this energy loss reflects the areal density (ρL) of the plasma transited. Up to 11 proton spectrometers simultaneously view D^3He implosions from different directions. While the burn-averaged and spatially averaged ρL for each implosion is typically between 50 to 75 mg/cm^2 within a group of similar implosions, there are often significant differences between the individual spectra of a given shot, in both their average implied ρL ( ˜50% about the mean) and in the low-energy tail. Some of these low-mode (ℓ ˜ 1) individual-shot asymmetries are attributable to laser drive asymmetry. However, for small amounts of energy imbalance (<=5% rms), the measured asymmetries are found to be uncorrelated with UV-measured laser imbalance. This indicates that other sources of asymmetry, such as capsule asymmetries, may play a role. In addition to nonuniformities, time evolution is the other important component to line broadening and spectral shape. To most clearly elucidate this effect, implosions of 24-μm-thick CH capsules were conducted. In a 400-ps period between first shock coalescence and compression, the spatially averaged ρL changes from ˜ 8 to ˜ 70 mg/cm^2. An important issue is whether the shell asymmetries could have already been established at the time of first shock coalescence. Supported in part by the U.S. D.O.E. Office of Inertial Confinement Fusion (Grant DE-FG03-99DP00300; Cooperative Agreement DE-FC03-92SF19460), LLE (subcontract P0410025G), LLNL (subcontract B313975). (Petrasso: Visiting Senior Scientist at LLE.)

  4. Areal and volumetric bone mineral density and geometry at two levels of protein intake during caloric restriction: a randomized, controlled trial.

    PubMed

    Sukumar, Deeptha; Ambia-Sobhan, Hasina; Zurfluh, Robert; Schlussel, Yvette; Stahl, Theodore J; Gordon, Chris L; Shapses, Sue A

    2011-06-01

    Weight reduction induces bone loss by several factors, and the effect of higher protein (HP) intake during caloric restriction on bone mineral density (BMD) is not known. Previous study designs examining the longer-term effects of HP diets have not controlled for total calcium intake between groups and have not examined the relationship between bone and endocrine changes. In this randomized, controlled study, we examined how BMD (areal and volumetric), turnover markers, and hormones [insulin-like growth factor 1 (IGF-1), IGF-binding protein 3 (IGFBP-3), 25-hydroxyvitamin D, parathyroid hormone (PTH), and estradiol] respond to caloric restriction during a 1-year trial using two levels of protein intake. Forty-seven postmenopausal women (58.0 ± 4.4 years; body mass index of 32.1 ± 4.6 kg/m(2) ) completed the 1-year weight-loss trial and were on a higher (HP, 24%, n = 26) or normal protein (NP, 18%, n = 21) and fat intake (28%) with controlled calcium intake of 1.2 g/d. After 1 year, subjects lost 7.0% ± 4.5% of body weight, and protein intake was 86 and 60 g/d in the HP and NP groups, respectively. HP compared with NP diet attenuated loss of BMD at the ultradistal radius, lumbar spine, and total hip and trabecular volumetric BMD and bone mineral content of the tibia. This is consistent with the higher final values of IGF-1 and IGFBP-3 and lower bone-resorption marker (deoxypyridinoline) in the HP group than in the NP group (p < .05). These data show that a higher dietary protein during weight reduction increases serum IGF-1 and attenuates total and trabecular bone loss at certain sites in postmenopausal women.

  5. Areal and Volumetric Bone Mineral Density and Geometry at Two Levels of Protein Intake During Caloric Restriction: A Randomized, Controlled Trial

    PubMed Central

    Sukumar, Deeptha; Ambia-Sobhan, Hasina; Zurfluh, Robert; Schlussel, Yvette; Stahl, Theodore J; Gordon, Chris L; Shapses, Sue A

    2011-01-01

    Weight reduction induces bone loss by several factors, and the effect of higher protein (HP) intake during caloric restriction on bone mineral density (BMD) is not known. Previous study designs examining the longer-term effects of HP diets have not controlled for total calcium intake between groups and have not examined the relationship between bone and endocrine changes. In this randomized, controlled study, we examined how BMD (areal and volumetric), turnover markers, and hormones [insulin-like growth factor 1 (IGF-1), IGF-binding protein 3 (IGFBP-3), 25-hydroxyvitamin D, parathyroid hormone (PTH), and estradiol] respond to caloric restriction during a 1-year trial using two levels of protein intake. Forty-seven postmenopausal women (58.0 ± 4.4 years; body mass index of 32.1 ± 4.6 kg/ m2) completed the 1-year weight-loss trial and were on a higher (HP, 24%, n =26) or normal protein (NP, 18%, n =21) and fat intake (28%) with controlled calcium intake of 1.2 g/d. After 1 year, subjects lost 7.0% ± 4.5% of body weight, and protein intake was 86 and 60 g/d in the HP and NP groups, respectively. HP compared with NP diet attenuated loss of BMD at the ultradistal radius, lumbar spine, and total hip and trabecular volumetric BMD and bone mineral content of the tibia. This is consistent with the higher final values of IGF-1 and IGFBP-3 and lower bone-resorption marker (deoxypyridinoline) in the HP group than in the NP group ( p <.05). These data show that a higher dietary protein during weight reduction increases serum IGF-1 and attenuates total and trabecular bone loss at certain sites in postmenopausal women. PMID:21611972

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

    SciTech Connect

    MacKinnon, A. J.; Meezan, N. B.; Ross, J. S.; Le Pape, S.; Berzak Hopkins, L.; Divol, L.; Ho, D.; Milovich, J.; Pak, A.; Ralph, J.; Döppner, T.; Patel, P. K.; Thomas, C.; Tommasini, R.; Haan, S.; MacPhee, A. G.; McNaney, J.; Caggiano, J.; Hatarik, R.; Bionta, R.; Ma, T.; Spears, B.; Rygg, J. R.; Benedetti, L. R.; Town, R. P. J.; Bradley, D. K.; Dewald, E. L.; Fittinghoff, D.; Jones, O. S.; Robey, H. R.; Moody, J. D.; Khan, S.; Callahan, D. A.; Hamza, A.; Biener, J.; Celliers, P. M.; Braun, D. G.; Erskine, D. J.; Prisbrey, S. T.; Wallace, R. J.; Kozioziemski, B.; Dylla-Spears, R.; Sater, J.; Collins, G.; Storm, E.; Hsing, W.; Landen, O.; Atherton, J. L.; Lindl, J. D.; Edwards, M. J.; Frenje, J. A.; Gatu-Johnson, M.; Li, C. K.; Petrasso, R.; Rinderknecht, H.; Rosenberg, M.; Séguin, F. H.; Zylstra, A.; Knauer, J. P.; Grim, G.; Guler, N.; Merrill, F.; Olson, R.; Kyrala, G. A.; Kilkenny, J. D.; Nikroo, A.; Moreno, K.; Hoover, D. E.; Wild, C.; Werner, E.

    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.

  7. High-density carbon ablator experiments on the National Ignition Facility

    SciTech Connect

    MacKinnon, A. J. Meezan, N. B.; Ross, J. S.; Le Pape, S.; Berzak Hopkins, L.; Divol, L.; Ho, D.; Milovich, J.; Pak, A.; Ralph, J.; Döppner, T.; Patel, P. K.; Thomas, C.; Tommasini, R.; Haan, S.; MacPhee, A. G.; McNaney, J.; Caggiano, J.; Hatarik, R.; Bionta, R.; and others

    2014-05-15

    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.

  8. Prediction of Areal Bone Mineral Density and Bone Mineral Content in Children and Adolescents Living With HIV Based on Anthropometric Variables.

    PubMed

    Lima, Luiz Rodrigo Augustemak de; Krug, Rodrigo de Rosso; Silva, Rosane Carla Rosendo da; Carvalho, Aroldo Prohmann de; González-Chica, David Alejandro; Back, Isabela de Carlos; Petroski, Edio Luiz

    2016-10-01

    Children and adolescents living with HIV have low bone mass for age. There are reliable and accurate methods for evaluation of bone mass, however, alternative methods are necessary, especially, for application in limited-resource scenarios. Anthropometry is a noninvasive and low cost method that can predict bone mass in healthy youths. The aim of the study was to develop predictive equations for bone mineral content and bone mineral density in children and adolescents living with HIV based on anthropometric variables. Forty-eight children and adolescents of both sexes (24 females) from 7 to 17 years, living in greater Florianopolis area, Santa Catarina, Brazil, who were under clinical follow-up at "Hospital Infantil Joana de Gusmão", participated in the study. Dual-energy X-ray absorptiometry was used to evaluate whole-body bone mineral content (BMC) and areal bone mineral density (aBMD). Height, body weight, bone diameters, arm circumference, and triceps skinfold were measured and the body mass index and arm muscle area were calculated. Multiple regression models were fitted to predict BMC and aBMD, using backward selection (p ≥ 0.05). Two predictive models with high R(2) values (84%-94%) were developed. Model 1 to estimate aBMD [Y = -0.1450124 + (height × 0.0033807) + (age × 0.0146381) + (body mass index × 0.0158838) + (skin color × 0.0421068)], and model 2 to estimate BMC [Y = 1095.1 + (body weight × 45.66973) + (age × 31.36516) + (arm circumference × -53.27204) + (femoral diameter × -9.594018)].The predictive models using anthropometry provided reliable estimates and can be useful to monitor aBMD and BMC in children and adolescents living with human immunodeficiency virus where limited resources are available.

  9. Novel Low-Density Ablators Containing Hyperbranched Poly(azomethine)s

    NASA Technical Reports Server (NTRS)

    Tigelaar, Dean

    2011-01-01

    An ablative composite is low-density (0.25 to 0.40 g/cu cm), easy to fabricate, and superior to the current state-of-the-art ablator (phenolic impregnated carbon ablator, PICA) in terms of decomposition temperature, char yield, and mechanical strength. Initial ablative testing with a CO2 laser under high-heat-flux (1,100 W/sq cm) conditions showed these new ablators are over twice as effective as PICA in terms of weight loss, as well as transfer of heat through the specimen. The carbon fiber/poly(azomethine) composites have the same density as PICA, but are 8 to 11 times stronger to irreversible breaking by tensile compression. In addition, polyazomethine char yields by thermogravimetric analysis are 70 to 80 percent at 1,000 C. This char yield is 10 to 20 percent higher than phenolic resins, as well as one of the highest char yields known for any polymer. A high char yield holds the composite together better toward shearing forces on reentry, as well as reradiates high heat fluxes. This innovative composite is stronger than PICA, so multiple pieces can be sealed together without fracture. Researchers have also studied polyazomethines before as linear polymers. Due to poor solubility, these polymers precipitate from the polymerization solvent as a low-molecular-weight (2 to 4 repeat units) powder. The only way found to date to keep linear polyazomethines in solution is by adding solubilizing side groups. However, these groups sacrifice certain polymer properties. These hyperbranched polyazomethines are high molecular weight and fully aromatic.

  10. Modeling CO{sub 2} Laser Ablative Impulse with Polymers

    SciTech Connect

    Sinko, John E.; Phipps, Claude R.; Sasoh, Akihiro

    2010-10-08

    Laser ablation vaporization models have usually ignored the spatial dependence of the laser beam. Here, we consider effects from modeling using a Gaussian beam for both photochemical and photothermal conditions. The modeling results are compared to experimental and literature data for CO{sub 2} laser ablation of the polymer polyoxymethylene under vacuum, and discussed in terms of the ablated mass areal density and momentum coupling coefficient. Extending the scope of discussion, laser ablative impulse generation research has lacked a cohesive strategy for linking the vaporization and plasma regimes. Existing models, mostly formulated for ultraviolet laser systems or metal targets, appear to be inappropriate or impractical for applications requiring CO{sub 2} laser ablation of polymers. A recently proposed method for linking the vaporization and plasma regimes for analytical modeling is addressed here along with the implications of its use. Key control parameters are considered, along with the major propulsion parameters needed for laser ablation propulsion modeling.

  11. Improved Performance of High Areal Density Indirect Drive Implosions at the National Ignition Facility using a Four-Shock Adiabat Shaped Drive

    DOE PAGES

    Casey, D. T.; Milovich, J. L.; Smalyuk, V. A.; ...

    2015-09-01

    Hydrodynamic instabilities can cause capsule defects and other perturbations to grow and degrade implosion performance in ignition experiments at the National Ignition Facility (NIF). Here, we show the first experimental demonstration that a strong unsupported first shock in indirect drive implosions at the NIF reduces ablation front instability growth leading to a 3 to 10 times higher yield with fuel ρR > 1 g=cm2. This work shows the importance of ablation front instability growth during the National Ignition Campaign and may provide a path to improved performance at the high compression necessary for ignition.

  12. Improved Performance of High Areal Density Indirect Drive Implosions at the National Ignition Facility using a Four-Shock Adiabat Shaped Drive

    SciTech Connect

    Casey, D. T.; Milovich, J. L.; Smalyuk, V. A.; Clark, D. S.; Robey, H. F.; Pak, A.; MacPhee, A. G.; Baker, K. L.; Weber, C. R.; Ma, T.; Park, H. -S.; Döppner, T.; Callahan, D. A.; Haan, S. W.; Patel, P. K.; Peterson, J. L.; Hoover, D.; Nikroo, A.; Yeamans, C. B.; Merrill, F. E.; Volegov, P. L.; Fittinghoff, D. N.; Grim, G. P.; Edwards, M. J.; Landen, O. L.; Lafortune, K. N.; MacGowan, B. J.; Widmayer, C. C.; Sayre, D. B.; Hatarik, R.; Bond, E. J.; Nagel, S. R.; Benedetti, L. R.; Izumi, N.; Khan, S.; Bachmann, B.; Spears, B. K.; Cerjan, C. J.; Gatu Johnson, M.; Frenje, J. A.

    2015-09-01

    Hydrodynamic instabilities can cause capsule defects and other perturbations to grow and degrade implosion performance in ignition experiments at the National Ignition Facility (NIF). Here, we show the first experimental demonstration that a strong unsupported first shock in indirect drive implosions at the NIF reduces ablation front instability growth leading to a 3 to 10 times higher yield with fuel ρR > 1 g=cm2. This work shows the importance of ablation front instability growth during the National Ignition Campaign and may provide a path to improved performance at the high compression necessary for ignition.

  13. Improved Performance of High Areal Density Indirect Drive Implosions at the National Ignition Facility using a Four-Shock Adiabat Shaped Drive.

    PubMed

    Casey, D T; Milovich, J L; Smalyuk, V A; Clark, D S; Robey, H F; Pak, A; MacPhee, A G; Baker, K L; Weber, C R; Ma, T; Park, H-S; Döppner, T; Callahan, D A; Haan, S W; Patel, P K; Peterson, J L; Hoover, D; Nikroo, A; Yeamans, C B; Merrill, F E; Volegov, P L; Fittinghoff, D N; Grim, G P; Edwards, M J; Landen, O L; Lafortune, K N; MacGowan, B J; Widmayer, C C; Sayre, D B; Hatarik, R; Bond, E J; Nagel, S R; Benedetti, L R; Izumi, N; Khan, S; Bachmann, B; Spears, B K; Cerjan, C J; Gatu Johnson, M; Frenje, J A

    2015-09-04

    Hydrodynamic instabilities can cause capsule defects and other perturbations to grow and degrade implosion performance in ignition experiments at the National Ignition Facility (NIF). Here, we show the first experimental demonstration that a strong unsupported first shock in indirect drive implosions at the NIF reduces ablation front instability growth leading to a 3 to 10 times higher yield with fuel ρR>1  g/cm(2). This work shows the importance of ablation front instability growth during the National Ignition Campaign and may provide a path to improved performance at the high compression necessary for ignition.

  14. Endometrial ablation

    MedlinePlus

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

  15. Experimental and Computational Studies of High Energy Density Plasma Streams Ablated from Fine Wires

    SciTech Connect

    Greenly, John B.; Seyler, Charles

    2014-03-30

    Experimental and computational studies of high energy density plasma streams ablated from fine wires. Laboratory of Plasma Studies, School of Electrical and Computer Engineering, Cornell University. Principal Investigators: Dr. John B. Greenly and Dr. Charles E. Seyler. This report summarizes progress during the final year of this project to study the physics of high energy density (HED) plasma streams of 10^17-10^20/cm3 density and high velocity (~100-500 km/s). Such streams are produced from 5-250 micrometer diameter wires heated and ionized by a 1 MA, 250 ns current pulse on the COBRA pulsed power facility at Cornell University. Plasma is ablated from the wires and is driven away to high velocity by unbalanced JxB force. A wire, or an array of wires, can persist as an essentially stationary, continuous source of this streaming plasma for >200 ns, even with driving magnetic fields of many Tesla and peak current densities in the plasma of many MA/cm2. At the heart of the ablation stream generation is the continuous transport of mass from the relatively cold, near-solid-density wire "core" into current-carrying plasma within 1 mm of the wire, followed by the magnetic acceleration of that plasma and its trapped flux to form a directed stream. In the first two years of this program, an advancing understanding of ablation physics led to the discovery of several novel wire ablation experimental regimes. In the final year, one of these new HED plasma regimes has been studied in quantitative detail. This regime studies highly reproducible magnetic reconnection in strongly radiating plasma with supersonic and superalfvenic flow, and shock structures in the outflow. The key discovery is that very heavy wires, e.g. 250 micrometer diameter Al or 150 micrometer Cu, behave in a qualitatively different way than the lighter wires typically used in wire-array Z-pinches. Such wires can be configured to produce a static magnetic X-point null geometry that stores magnetic and

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

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

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

  17. First Case of Automatic His Potential Detection With a Novel Ultra High-density Electroanatomical Mapping System for AV Nodal Ablation

    PubMed Central

    Hilbert, Sebastian; Kosiuk, Jedrzej; John, Silke; Hindricks, Gerhard; Bollmann, Andreas

    2016-01-01

    A 74-year old was considered for atrioventricular (AV) nodal ablation in view of atrial fibrillation (AF) with poorly controlled ventricular rate despite being on amiodarone. Targeted AV nodal ablation was successfully performed after identifying the target site for ablation by reviewing an ultra high-density map of the His region produced by automatic electrogram annotation. PMID:25852249

  18. Cryogenic THD and DT layer implosions with high density carbon ablators in near-vacuum hohlraums

    NASA Astrophysics Data System (ADS)

    Meezan, N. B.; Berzak Hopkins, L. F.; Le Pape, S.; Khan, S. F.; Pak, A. E.; Divol, L.; Ho, D. D.; Ma, T.; Doeppner, T.; Rygg, J. R.; Field, J. E.; Jones, O. S.; Milovich, J. L.; Kozioziemski, B. J.; Hamza, A. V.; MacKinnon, A. J.; Hsing, W. W.; Edwards, M. J.

    2014-10-01

    High Density Carbon (HDC or diamond) is a promising ablator material for use in near-vacuum hohlraums, as its high density allows for ignition designs with laser pulse durations <10 ns. A series of experiments in 2013 on the National Ignition Facility culminated in a DT layered implosion driven by a 6.5 ns, 2-shock laser pulse. This talk describes these experiments and comparisons with the design code HYDRA. Backlit radiography of a THD layered capsule demonstrated an ablator implosion velocity of 385 km/s with a slightly oblate hot spot shape; however, other diagnostics suggested an asymmetric compressed fuel layer. The streak camera-based SPIDER diagnostic showed a double-peaked history of the capsule self-emission. Simulations suggest that this is a signature of a low-temperature hot spot. Changes to the laser pulse-shape and pointing for a subsequent DT implosion resulted in a higher temperature, prolate hot-spot and a thermonuclear yield of 1 . 8 ×1015 neutrons. Prepared by LLNL under Contract DE-AC52-07NA27344.

  19. Cryogenic THD and DT layer implosions with high density carbon ablators in near-vacuum hohlraums

    DOE PAGES

    Meezan, N. B.; Berzak Hopkins, L. F.; Le Pape, S.; ...

    2015-06-02

    High Density Carbon (HDC or diamond) is a promising ablator material for use in near-vacuum hohlraums, as its high density allows for ignition designs with laser pulse durations of <10 ns. A series of Inertial Confinement Fusion (ICF) experiments in 2013 on the National Ignition Facility [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)] culminated in a DT layered implosion driven by a 6.8 ns, 2-shock laser pulse. This paper describes these experiments and comparisons with ICF design code simulations. Backlit radiography of a THD layered capsule demonstrated an ablator implosion velocity of 385 km/s with a slightlymore » oblate hot spot shape. Other diagnostics suggested an asymmetric compressed fuel layer. A streak camera-based hot spot self-emission diagnostic (SPIDER) showed a double-peaked history of the capsule self-emission. Simulations suggest that this is a signature of low quality hot spot formation. Changes to the laser pulse and pointing for a subsequent DT implosion resulted in a higher temperature, prolate hot spot and a thermonuclear yield of 1.8 x 10¹⁵ neutrons, 40% of the 1D simulated yield.« less

  20. Cryogenic THD and DT layer implosions with high density carbon ablators in near-vacuum hohlraums

    SciTech Connect

    Meezan, N. B.; Berzak Hopkins, L. F.; Le Pape, S.; Divol, L.; MacKinnon, A. J.; Döppner, T.; Ho, D. D.; Jones, O. S.; Khan, S. F.; Ma, T.; Milovich, J. L.; Pak, A. E.; Ross, J. S.; Thomas, C. A.; Benedetti, L. R.; Bradley, D. K.; Celliers, P. M.; Clark, D. S.; Field, J. E.; Haan, S. W.; Izumi, N.; Kyrala, G. A.; Moody, J. D.; Patel, P. K.; Ralph, J. E.; Rygg, J. R.; Sepke, S. M.; Spears, B. K.; Tommasini, R.; Town, R. P. J.; Biener, J.; Bionta, R. M.; Bond, E. J.; Caggiano, J. A.; Eckart, M. J.; Gatu Johnson, M.; Grim, G. P.; Hamza, A. V.; Hartouni, E. P.; Hatarik, R.; Hoover, D. E.; Kilkenny, J. D.; Kozioziemski, B. J.; Kroll, J. J.; McNaney, J. M.; Nikroo, A.; Sayre, D. B.; Stadermann, M.; Wild, C.; Yoxall, B. E.; Landen, O. L.; Hsing, W. W.; Edwards, M. J.

    2015-06-02

    High Density Carbon (HDC or diamond) is a promising ablator material for use in near-vacuum hohlraums, as its high density allows for ignition designs with laser pulse durations of <10 ns. A series of Inertial Confinement Fusion (ICF) experiments in 2013 on the National Ignition Facility [E. I. Moses et al., Phys. Plasmas 16, 041006 (2009)] culminated in a DT layered implosion driven by a 6.8 ns, 2-shock laser pulse. This paper describes these experiments and comparisons with ICF design code simulations. Backlit radiography of a THD layered capsule demonstrated an ablator implosion velocity of 385 km/s with a slightly oblate hot spot shape. Other diagnostics suggested an asymmetric compressed fuel layer. A streak camera-based hot spot self-emission diagnostic (SPIDER) showed a double-peaked history of the capsule self-emission. Simulations suggest that this is a signature of low quality hot spot formation. Changes to the laser pulse and pointing for a subsequent DT implosion resulted in a higher temperature, prolate hot spot and a thermonuclear yield of 1.8 x 10¹⁵ neutrons, 40% of the 1D simulated yield.

  1. High-density carbon ablator ignition path with low-density gas-filled rugby hohlraum

    SciTech Connect

    Amendt, Peter; Ho, Darwin D.; Jones, Ogden S.

    2015-04-15

    A recent low gas-fill density (0.6 mg/cc {sup 4}He) cylindrical hohlraum experiment on the National Ignition Facility has shown high laser-coupling efficiency (>96%), reduced phenomenological laser drive corrections, and improved high-density carbon capsule implosion symmetry [Jones et al., Bull. Am. Phys. Soc. 59(15), 66 (2014)]. In this Letter, an ignition design using a large rugby-shaped hohlraum [Amendt et al., Phys. Plasmas 21, 112703 (2014)] for high energetics efficiency and symmetry control with the same low gas-fill density (0.6 mg/cc {sup 4}He) is developed as a potentially robust platform for demonstrating thermonuclear burn. The companion high-density carbon capsule for this hohlraum design is driven by an adiabat-shaped [Betti et al., Phys. Plasmas 9, 2277 (2002)] 4-shock drive profile for robust high gain (>10) 1-D ignition performance and large margin to 2-D perturbation growth.

  2. Determination of energy density threshold for laser ablation of bacteria. An in vitro study.

    PubMed

    Coffelt, D W; Cobb, C M; MacNeill, S; Rapley, J W; Killoy, W J

    1997-01-01

    The Nd:YAG and CO2 lasers have been shown to be bactericidal at relative low energy densities. However, at energy densities exceeding 120 J/cm2 (CO2) and 200 J/cm2 (Nd:YAG), laser irradiation also causes irreparable root surface damage. The purpose of this study was to determine, in vitro, the energy density threshold at which microbial ablation could be achieved while inflicting the least amount of damage to the root surfaces of human teeth. Pairs of Escherichia coli colonies cultured on broth agar were treated with a CO2 laser using a pulsed waveform at approximate energy densities ranging from 3 to 110 J/cm2. One of each colony-pair was then examined by scanning electron microscopy (SEM) and the other subcultured for viable microbes. Roots of extracted teeth were lightly scaled and treated by CO2 laser, again with pulsed beam using approximate energy densities of 3 to 110 J/cm2: and examined by SEM. Regardless of the level of energy density, residual bacteria could be subcultured from all laser treated microbial colonies. The inability of the laser to completely obliterate microbial colonies was likely due to: depth of energy penetration, difficulty in precisely overlapping beam focal spots, irregular beam profile, and presence of microbes at the periphery of the beam focal spot. The threshold energy density for bacterial obliteration was determined to be 11 J/cm2 and that for root damage was 41 J/cm2. Root damage was evident by charring, crater formation, melt-down and resolidification surface mineral, and increasing surface porosity. The results of this in vitro study indicate that when used at an energy density between 11 and 41 J/cm2 the CO2 laser may destroy microbial colonies without inflicting undue damage to the tooth root surface.

  3. Investigation of gamma-ray time shifts caused by capsule areal density variations in inertial confinement fusion experiments at the national ignition facility and the omega facility

    NASA Astrophysics Data System (ADS)

    Grafil, Elliot M.

    This thesis describes work on Cherenkov based gamma detectors used as diag- nostics at Inertial Confinement Fusion (ICF) facilities. The first part describes the calibration and commissioning of the Gamma Reaction History diagnostic which is a four cell Cherenkov detector array used to characterize the ICF implosion at the National Ignition Facility (NIF) by measuring the gamma rays generated during the fusion event. Two of the key metrics which the GRH measures are Gamma Bang Time (GBT) generated from the D(T,α)n thermonuclear burn and Ablator Peak Time (APT) caused by (n,n‧)gamma reactions in the surrounding capsule ablator. Simulations of ignition capsules predict that GBT and APT should be time synchronized. After GRH commissioning, the array was used during first year of NIF operation in the National Ignition Campaign. Contrary to expectations, time shifts between GBT and APT of order 10s of picoseconds were observed. In order to further investigate the possibility of these time shifts in view of testing both instrument and code credibility an ICF shot campaign at the smaller OMEGA facility in Rochester was devised. It was performed during two full shot days in April of 2013 and 2014 and confirmed in principle the viability of the Cherenkov detector approach but raised additional questions regarding the credibility of the simulation codes used to describe ICF experiments. Specifically the measurements show that the understanding of temporal behavior of GBT vs APT may not be properly modeled in the DRACO code used at OMEGA. In view of the OMEGA results which showed no time shifts between GBT and APT, the readout and timing synchronization system of the GRH setup at the NIF was reevaluated in the framework of this thesis. Motivated by the results, which highlighted the use of wrong optical fiber diameters and possible problems with the installed variable optical attenuators, the NIF equipment has been updated over the recent months and new timing tests will

  4. Laser-ablated loading of solid target through foams of overcritical density

    SciTech Connect

    De Angelis, R. Consoli, F.; Andreoli, P.; Cristofari, G.; Di Giorgio, G.; Gus'kov, S. Yu.; Rupasov, A. A.

    2015-07-15

    The main objective of the work is to study the conversion of the laser pulse energy into the energy of the hydrodynamic motion of matter in a solid target following the initial absorption of laser radiation in a layer of porous material. Results of experiments on plane massive aluminum targets, coated with a layer of porous plastic with density greater than the critical density of the plasma created, are presented. Experiments were carried out on the laser installation ABC of the Research Center ENEA-Frascati; the targets were irradiated by a beam of the fundamental harmonic of Nd-laser radiation with an energy of about 50 kJ, intensity of 10{sup 13 }W/cm{sup 2}, and 3 ns duration. The experimental method consisted in measuring the volume of the craters created on the aluminum surface behind various thicknesses and densities of the porous absorber of laser radiation. On the basis of these measurements and of an advanced analytical model, quantitative conclusions are made on how the efficiency of laser energy transfer to the solid part of the target (laser-ablated loading) depends on thickness and density of the porous absorber.

  5. Near-vacuum hohlraums for driving fusion implosions with high density carbon ablators

    NASA Astrophysics Data System (ADS)

    Berzak Hopkins, Laura

    2014-10-01

    Achieving ignition requires reaching fast implosion velocities, which highlights the need for a highly efficient hohlraum to drive indirect-drive inertial confinement fusion implosions. Gas-filled hohlraums are typically utilized due to the pulse length (15-20 ns) needed to drive plastic (CH) capsules. With the recent use of 3× denser high-density carbon (HDC) capsules, ignition pulses can be less than 10 ns in duration, providing the opportunity to utilize near-vacuum hohlraums (NVH) to drive ignition-relevant implosions on the National Ignition Facility (NIF) with minimal laser-plasma instabilities which complicate standard gas-filled hohlraums. Initial NVH implosions on the NIF have demonstrated coupling efficiency significantly higher than observed in gas-filled hohlraums - backscatter losses less than 2% and virtually no suprathermal electron generation. A major design challenge for the NVH is symmetry control. Without tamping gas, the hohlraum wall quickly expands filling the volume with gold plasma. However, results to-date indicate that the inner-cone beams propagate freely to the hohlraum wall for at least 6.5 ns. With minimal predicted cross-beam power transfer, this propagation enables symmetry control via dynamic beam phasing - time-dependent direct adjustment of the inner- and outer-cone laser pulses. A series of experiments with an HDC ablator and NVH culminated in a 6 ns, 1.2 MJ cryogenic DT layered implosion yielding 1.8 × 1015 neutrons--significantly higher yield than any CH implosion at comparable energy. This implosion reached an ignition-relevant velocity -350 km/s - with no observed ablator mix in the hot spot. Recent experiments have explored two-shock designs in a larger, 6.72 mm hohlraum, and upcoming experiments will incrementally extend the pulse duration toward a 9 ns long, three-shock ignition design. Prepared by LLNL under Contract DE-AC52-07NA27344.

  6. Near-vacuum hohlraums with uranium walls for driving high density carbon ablators

    NASA Astrophysics Data System (ADS)

    Meezan, N. B.; Dewald, E. L.; Berzak Hopkins, L. F.; Moore, A. S.; Schneider, M. V.; Thomas, C. A.; Tommasini, R.; Ho, D. D.; Clark, D. S.; Weber, C. R.; Hamza, A. V.; Nikroo, A.; Le Pape, S.; Divol, L.; MacKinnon, A. J.

    2015-11-01

    We present experimental results for unlined uranium near-vacuum hohlraums on the National Ignition Facility. X-ray wall losses are lower in uranium than in gold at radiation temperatures near 300 eV. In addition, the intensity of x-rays with energy hν > 1 . 8 keV is lower for uranium hohlraums. The softer uranium spectrum allows the use of ablators with lower levels of dopants that reduce rocket efficiency and increase the risk of polluting the hot-spot with emissive material. Experiments in the ViewFactor platform measured 5% higher total x-ray intensity and 30% lower intensity of hν > 1 . 8 keV for uranium relative to gold. Back-lit implosions using undoped high-density carbon (HDC, or diamond) capsules achieved a velocity of 400 +/- 20 km/s compared to 360 +/- 20 km/s for gold. These results have led the NIF HDC campaign to baseline uranium hohlraums for upcoming experiments. Prepared by LLNL under Contract DE-AC52-07NA27344.

  7. Ablation and carbon deposition induced by UV laser irradiation of polyimide: Application to the metallization of VIAs in high density printed circuit boards

    NASA Astrophysics Data System (ADS)

    Metayer, P.; Davenas, J.; Bureau, J. M.

    2001-12-01

    Polyimides are known to exhibit large ablation rates upon irradiation with excimer laser due to their high absorbance in the UV and low fluorescence yield. We have studied different regimes of laser ablation according to the fluence and studied the structures resulting from carbon products deposition. For fluences larger than the polyimide ablation threshold, but lower than the carbon one, the development of one structure is the dominant process, whereas large ablation rates lead to polyimide etching above the carbon ablation threshold. The deposition of a carbon layer on the walls of ablated slits has in particular been investigated using an original experimental technique. Optical microscopy and MEB have shown that this carbon layer covered the main height of the ablated holes whereas a threshold (bare polyimide) for carbon condensation was evidenced at the bottom of the ablated hole. Raman spectroscopy and conductivity measurements have shown that the carbon phase is mainly graphitic. A dependence of the carbon condensation threshold on the slit width has been evidenced and discussed in relation with the angle of ejection of ablation debris. A procedure has been developed to render the bare polyimide of the threshold region conductive. At last the conductive properties of the walls of the ablated holes have been exploited to perform an electrolytic metallization. Implications for the production of interconnection vertical interconnections (VIAs) in high density printed circuits are addressed.

  8. Phenomenological and experimental study of the thermal response of low density silica ablators to high enthalpy plasma flows

    NASA Technical Reports Server (NTRS)

    Henline, William D.; Tran, Huy K.; Hamm, Michael K.

    1991-01-01

    A complete analysis of the melting-ablator governing equations is carried out for porous ablators with the purpose of establishing an approximate analytical model capable of determining surface recession, temperature, and heat flux as well as in-depth temperature profiles. A detailed dimensional analysis of the melt-flow governing equations is performed for parameters applicable to high-enthalpy flows. Results of arc-jet flow experiments performed on NASA Reusable Surface Insulation materials of different densities and over a range of stagnation pressures and heat fluxes are discussed. A dimensionless correlation for melt run-offs is derived in terms of material and flow parameters; however, it is pointed out that the accuracy of the current data is sufficient to conclude the compliance with the model.

  9. Design Calculations for NIF Convergent Ablator Experiments

    NASA Astrophysics Data System (ADS)

    Olson, R. E.; Callahan, D. A.; Hicks, D. G.; Landen, O. L.; Langer, S. H.; Meezan, N. B.; Spears, B. K.; Widmann, K.; Kline, J. L.; Wilson, D. C.; Petrasso, R. D.; Leeper, R. J.

    2010-11-01

    Design calculations for NIF convergent ablator experiments will be described. The convergent ablator experiments measure the implosion trajectory, velocity, and ablation rate of an x-ray driven capsule and are a important component of the U. S. National Ignition Campaign at NIF. The design calculations are post-processed to provide simulations of the key diagnostics -- 1) Dante measurements of hohlraum x-ray flux and spectrum, 2) streaked radiographs of the imploding ablator shell, 3) wedge range filter measurements of D-He3 proton output spectra, and 4) GXD measurements of the imploded core. The simulated diagnostics will be compared to the experimental measurements to provide an assessment of the accuracy of the design code predictions of hohlraum radiation temperature, capsule ablation rate, implosion velocity, shock flash areal density, and x-ray bang time. Post-shot versions of the design calculations are used to enhance the understanding of the experimental measurements and will assist in choosing parameters for subsequent shots and the path towards optimal ignition capsule tuning. *SNL, LLNL, and LANL are operated under US DOE contracts DE-AC04-94AL85000. DE-AC52-07NA27344, and DE-AC04-94AL85000.

  10. Design options for improved performance with high-density carbon ablators and low-gas fill hohlraum targets

    NASA Astrophysics Data System (ADS)

    Berzak Hopkins, L.; Divol, L.; Lepape, S.; Meezan, N. B.; Dewald, E.; Ho, D.; Khan, S.; Pak, A.; Ralph, J.; Ross, J. S.

    2016-10-01

    Recent simulation-based and experimental work using high-density carbon ablators in unlined uranium hohlraums with 0.3 mg/cc helium fill have demonstrated round implosions with minimal evolution of Legendre moment P2 during burn. To extend this promising work, design studies have been performed to explore potential performance improvements with larger capsules, while maintaining similar case-to-capsule target ratios. We present here the results of these design studies, which will motivate a series of upcoming experiments at the National Ignition Facility. Prepared by LLNL under Contract DE-AC52-07NA27344.

  11. Comparison of plasma temperature and electron density on nanosecond laser ablation of Cu and nano-Cu

    SciTech Connect

    Chen, Anmin; Jiang, Yuanfei; Wang, Tingfeng; Shao, Junfeng; Jin, Mingxing

    2015-03-15

    Laser-induced breakdown spectroscopy is performed through the collection of spectra by spectral detection equipment at different delay times and distances from targets composed of Cu and nano-Cu, which are ablated using a Nd:YAG laser (532 nm, 10 ns, 10 Hz) in our experiments. The measured wavelength range is from 475 nm to 525 nm. Using the local thermodynamic equilibrium model, we analyze the characteristics of the plasma temperature and the electron number density for different distances between the target surface and the lens. The results show that when compared with the nano-Cu plasma case, the temperature of the Cu plasma is higher, while its electron number density is lower.

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

    SciTech Connect

    Hayes, Anna; Grim, Gary; Jungnam, Jerry; Bradley, Paul; Rundberg, Bob; Wilhelmy, Jerry; Wilson, Doug

    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 the ideal

  13. Studies on subcritical and overcritical density laser ablated TAC foam targets

    NASA Astrophysics Data System (ADS)

    Chaurasia, S.; Leshma, P.; Murali, C. G.; Borisenko, N. G.; Munda, D. S.; Orekhov, A.; Gromov, A. I.; Merkuliev, Yu. A.; Dhareshwar, L. J.

    2015-05-01

    In this paper, the interaction of high power laser with low density polymer foam with density as low as 2 mg/cm3, 4 mg/cm3, 20 mg/cm3 30 mg/cm3 and 50 mg/cm3 targets are investigated and compared with solid polymer targets. An understanding of such interaction is important from fusion research point of view. Low density foam coating of fusion capsule has been proposed in order to smooth in direct drive scheme and also it is being used as efficient x-ray converter in indirect drive scheme. It is observed that about 75-80% of the laser energy is absorbed in the subcritical (with density <4 mg/cm3) foam targets and the soft x-ray yield in this case is almost two times that measured in the over dense (supper critical) targets. The optical shadowgraphy of the targets shows that the laser coupling in low density foam is associated with a supersonic heat wave while, with increasing density this phenomenon is replaced by subsonic absorption and shock formation. In the case of a 50 mg/cm3 foams the foil velocity reduced by 35% (i.e. 5×106 cm/s), which further reduced to 3.8×106 cm/s in case solid polymer targets.

  14. Ablation of ErbB4 from excitatory neurons leads to reduced dendritic spine density in mouse prefrontal cortex

    PubMed Central

    Cooper, Margaret A.; Koleske, Anthony J.

    2014-01-01

    Dendritic spine loss is observed in many psychiatric disorders, including schizophrenia, and likely contributes to the altered sense of reality, disruption of working memory, and attention deficits that characterize these disorders. ErbB4, a member of the EGF family of receptor tyrosine kinases, is genetically associated0020with schizophrenia, suggesting that alterations in ErbB4 function contribute to the disease pathology. Additionally, ErbB4 functions in synaptic plasticity, leading us to hypothesize that disruption of ErbB4 signaling may affect dendritic spine development. We show that dendritic spine density is reduced in the dorsomedial prefrontal cortex of ErbB4 conditional whole-brain knockout mice. We find that ErbB4 localizes to dendritic spines of excitatory neurons in cortical neuronal cultures and is present in synaptic plasma membrane preparations. Finally, we demonstrate that selective ablation of ErbB4 from excitatory neurons leads to a decrease in the proportion of mature spines and an overall reduction in dendritic spine density in the prefrontal cortex of weanling (P21) mice that persists at 2 months of age. These results suggest that ErbB4 signaling in excitatory pyramidal cells is critical for the proper formation and maintenance of dendritic spines in excitatory pyramidal cells. PMID:24752666

  15. Measurements of ablation-front hydrodynamic instability growth in high-density carbon (HDC) ignition targets at the National Ignition Facility (NIF)

    NASA Astrophysics Data System (ADS)

    Casey, D.; Smalyuk, V.; Peterson, L.; Berzak Hopkins, L.; Bunn, T.; Carlson, L.; Haan, S.; Ho, D.; Hoover, D.; Kroll, J.; Landen, O.; Le Pape, S.; MacKinnon, A.; Macphee, A.; Meezan, N.; Milovich, J.; Nikroo, A.; Remington, B.; Robey, H.; Ross, S.

    2014-10-01

    High-density carbon (HDC) has emerged as a promising ablator for ignition experiments at the National Ignition Facility (NIF) partly because of its efficient coupling of the drive energy to fuel. Experiments during the National Ignition Campaign using a CH plastic ablator have shown that instability growth and the resultant mix of plastic into the hotspot was a significant source of overall the observed performance degradation. Likewise, mix of HDC ablator into the hotspot may also be a concern, as growth rates for HDC are comparable to CH and ablator/dopant is higher Z than CH ablators making the consequences potentially more severe. To help understand this issue, we plan to perform the first instability growth measurements of W-doped HDC implosions with preimposed mode 60 and mode 90 perturbations in convergent geometry using actual ignition targets and drives. These results will be presented and compared to ignition design simulations. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  16. A fibre based triature interferometer for measuring rapidly evolving, ablatively driven plasma densities

    NASA Astrophysics Data System (ADS)

    Macdonald, J.; Bland, S. N.; Threadgold, J.

    2015-08-01

    We report on the first use of a fibre interferometer incorporating triature analysis for measuring rapidly evolving plasma densities of ne ˜ 1013/cm3 and above, such as those produced by simple coaxial plasma guns. The resultant system is extremely portable, easy to field in experiments, relatively cheap to produce, and—with the exception of a small open area in which the plasma is sampled—safe in operation as all laser light is enclosed.

  17. Bump evolution driven by the x-ray ablation Richtmyer-Meshkov effect in plastic inertial confinement fusion Ablators

    NASA Astrophysics Data System (ADS)

    Loomis, Eric; Braun, Dave; Batha, Steven H.; Landen, Otto L.

    2013-11-01

    Growth of hydrodynamic instabilities at the interfaces of inertial confinement fusion capsules (ICF) due to ablator and fuel non-uniformities are a primary concern for the ICF program. Recently, observed jetting and parasitic mix into the fuel were attributed to isolated defects on the outer surface of the capsule. Strategies for mitigation of these defects exist, however, they require reduced uncertainties in Equation of State (EOS) models prior to invoking them. In light of this, we have begun a campaign to measure the growth of isolated defects (bumps) due to x-ray ablation Richtmyer-Meshkov in plastic ablators to validate these models. Experiments used hohlraums with radiation temperatures near 70 eV driven by 15 beams from the Omega laser (Laboratory for Laser Energetics, University of Rochester, NY), which sent a ˜1.25Mbar shock into a planar CH target placed over one laser entrance hole. Targets consisted of 2-D arrays of quasi-gaussian bumps (10 microns tall, 34 microns FWHM) deposited on the surface facing into the hohlraum. On-axis radiography with a saran (Cl Heα - 2.76keV) backlighter was used to measure bump evolution prior to shock breakout. Shock speed measurements were also performed to determine target conditions. Simulations using the LEOS 5310 and SESAME 7592 models required the simulated laser power be turned down to 80 and 88%, respectively to match observed shock speeds. Both LEOS 5310 and SESAME 7592 simulations agreed with measured bump areal densities out to 6 ns where ablative RM oscillations were observed in previous laser-driven experiments, but did not occur in the x-ray driven case. The QEOS model, conversely, over predicted shock speeds and under predicted areal density in the bump.

  18. Observations of multimode perturbation decay at non-accelerating, soft x-ray driven ablation fronts

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    Minimizing the growth of hydrodynamic instabilities is a fundamental design issue facing the achievement of thermonuclear ignition and burn with Inertial Confinement Fusion (ICF). The thin capsules and extreme accelerations found in ICF make it an inherently unstable system primarily to Rayleigh-Taylor (RT) occurring at the ablation front. A potential mechanism by which perturbations at the outer capsule surface can be reduced lies in the already present ablative Richtmyer-Meshkov (RM) effect, which operates during the first shock transit of the ablator. At present, the available Equation of State (EOS) models predict a wide range of behavior for the ablative RM oscillations of multimode isolated defects on plastic (CH) capsules. To resolve these differences, we conducted experiments at the OMEGA Laser Facility [T. R. Boehly et al., Optics Comm. 133 (1997)] that measured the evolution of gaussian-shaped bumps driven by soft x-ray ablation from a halfraum. Shock speeds in the CH target were measured to reach 15 μm/ns for halfraum radiation temperatures of 70 eV lasting for up to 7 ns. The evolution of gaussian-shaped bumps of different widths and heights were measured using on-axis x-ray radiography at up to 37× magnification. Bumps with initial widths of 34 and 44 μm FWHM were found to grow by 3× their initial areal density and then saturate out to 6 ns due to lateral compression of the bump characteristic of the formation of a rippled shock front propagating into the solid target. Narrower 17 μm FWHM bumps, on the other hand, grew by roughly 2× followed immediately by a decrease back to initial values of areal density out to 7 ns, which largely agrees with both LEOS 5310 and SESAME 7592 EOS predictions. The difference in observed behavior suggests that high spatial frequency modes found in narrower bumps are needed to significantly affect the ablation front profile on shorter time scales.

  19. Waterproof, Ultrahigh Areal-Capacitance, Wearable Supercapacitor Fabrics.

    PubMed

    Yang, Yu; Huang, Qiyao; Niu, Liyong; Wang, Dongrui; Yan, Casey; She, Yiyi; Zheng, Zijian

    2017-02-24

    High-performance supercapacitors (SCs) are promising energy storage devices to meet the pressing demand for future wearable applications. Because the surface area of a human body is limited to 2 m(2) , the key challenge in this field is how to realize a high areal capacitance for SCs, while achieving rapid charging, good capacitive retention, flexibility, and waterproofing. To address this challenge, low-cost materials are used including multiwall carbon nanotube (MWCNT), reduced graphene oxide (RGO), and metallic textiles to fabricate composite fabric electrodes, in which MWCNT and RGO are alternatively vacuum-filtrated directly onto Ni-coated cotton fabrics. The composite fabric electrodes display typical electrical double layer capacitor behavior, and reach an ultrahigh areal capacitance up to 6.2 F cm(-2) at a high areal current density of 20 mA cm(-2) . All-solid-state fabric-type SC devices made with the composite fabric electrodes and water-repellent treatment can reach record-breaking performance of 2.7 F cm(-2) at 20 mA cm(-2) at the first charge-discharge cycle, 3.2 F cm(-2) after 10 000 charge-discharge cycles, zero capacitive decay after 10 000 bending tests, and 10 h continuous underwater operation. The SC devices are easy to assemble into tandem structures and integrate into garments by simple sewing.

  20. Moldable cork ablation material

    NASA Technical Reports Server (NTRS)

    1977-01-01

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

  1. Areal Rainfall Estimation for Flood Forecasting

    NASA Astrophysics Data System (ADS)

    Jones, A.; Bell, V.; Moore, R.

    2003-04-01

    This study deals with the estimation of catchment areal rainfall for the purpose of real-time flood forecasting using rainfall-runoff models. In the UK the two sources of rainfall data on the appropriate timescale are a sparse network of telemetered raingauges, with typical gauge spacings of 10 to 20km, and rainfall estimates derived from weather radar. The focus here is placed on raingauge estimation of rainfall. A survey of the literature reveals a vast number of methods developed for the estimation of areal rainfall from raingauge measurements on a range of spatial and temporal scales, ranging from simple weighting schemes to more complex interpolation methods. A review of previous method intercomparison studies identifies the need for a full evaluation of methods. Evaluation of a selection of nine weighting methods including Thiessen polygons, Standard Average Annual Rainfall (SAAR) weights and DTM-derived elevation weights has been carried out for two UK catchments. One catchment, the Brue in Somerset, is equipped with a special dense network of raingauges installed as part of the HYREX experiment. Evaluation was carried out using the PDM rainfall-runoff model with areal rainfall estimated from several sub-networks of raingauges and modelled flow compared with observed flow. Modelled flow was also compared with flow modelled using the ‘ground truth’ of areal rainfall estimated from the dense raingauge network. Estimates of 15 minute areal rainfall using each method were also compared directly with the areal estimate from the dense network for individual events characterised by either convective or stratiform rain. For stratiform rain, results indicated that all methods give reasonably accurate results, even when only two gauges are used, and the performances of the methods tested were almost indistinguishable. For convective rain, the Thiessen method gave consistently better results than the other methods, and the SAAR-method gave consistently worse

  2. Cryogenic tritium-hydrogen-deuterium and deuterium-tritium layer implosions with high density carbon ablators in near-vacuum hohlraums

    NASA Astrophysics Data System (ADS)

    Meezan, N. B.; Berzak Hopkins, L. F.; Le Pape, S.; Divol, L.; MacKinnon, A. J.; Döppner, T.; Ho, D. D.; Jones, O. S.; Khan, S. F.; Ma, T.; Milovich, J. L.; Pak, A. E.; Ross, J. S.; Thomas, C. A.; Benedetti, L. R.; Bradley, D. K.; Celliers, P. M.; Clark, D. S.; Field, J. E.; Haan, S. W.; Izumi, N.; Kyrala, G. A.; Moody, J. D.; Patel, P. K.; Ralph, J. E.; Rygg, J. R.; Sepke, S. M.; Spears, B. K.; Tommasini, R.; Town, R. P. J.; Biener, J.; Bionta, R. M.; Bond, E. J.; Caggiano, J. A.; Eckart, M. J.; Gatu Johnson, M.; Grim, G. P.; Hamza, A. V.; Hartouni, E. P.; Hatarik, R.; Hoover, D. E.; Kilkenny, J. D.; Kozioziemski, B. J.; Kroll, J. J.; McNaney, J. M.; Nikroo, A.; Sayre, D. B.; Stadermann, M.; Wild, C.; Yoxall, B. E.; Landen, O. L.; Hsing, W. W.; Edwards, M. J.

    2015-06-01

    High Density Carbon (or diamond) is a promising ablator material for use in near-vacuum hohlraums, as its high density allows for ignition designs with laser pulse durations of <10 ns. A series of Inertial Confinement Fusion (ICF) experiments in 2013 on the National Ignition Facility [Moses et al., Phys. Plasmas 16, 041006 (2009)] culminated in a deuterium-tritium (DT) layered implosion driven by a 6.8 ns, 2-shock laser pulse. This paper describes these experiments and comparisons with ICF design code simulations. Backlit radiography of a tritium-hydrogen-deuterium (THD) layered capsule demonstrated an ablator implosion velocity of 385 km/s with a slightly oblate hot spot shape. Other diagnostics suggested an asymmetric compressed fuel layer. A streak camera-based hot spot self-emission diagnostic (SPIDER) showed a double-peaked history of the capsule self-emission. Simulations suggest that this is a signature of low quality hot spot formation. Changes to the laser pulse and pointing for a subsequent DT implosion resulted in a higher temperature, prolate hot spot and a thermonuclear yield of 1.8 × 1015 neutrons, 40% of the 1D simulated yield.

  3. Cryogenic tritium-hydrogen-deuterium and deuterium-tritium layer implosions with high density carbon ablators in near-vacuum hohlraums

    SciTech Connect

    Meezan, N. B. Hopkins, L. F. Berzak; Pape, S. Le; Divol, L.; MacKinnon, A. J.; Döppner, T.; Ho, D. D.; Jones, O. S.; Khan, S. F.; Ma, T.; Milovich, J. L.; Pak, A. E.; Ross, J. S.; Thomas, C. A.; Benedetti, L. R.; Bradley, D. K.; Celliers, P. M.; Clark, D. S.; Field, J. E.; Haan, S. W.; and others

    2015-06-15

    High Density Carbon (or diamond) is a promising ablator material for use in near-vacuum hohlraums, as its high density allows for ignition designs with laser pulse durations of <10 ns. A series of Inertial Confinement Fusion (ICF) experiments in 2013 on the National Ignition Facility [Moses et al., Phys. Plasmas 16, 041006 (2009)] culminated in a deuterium-tritium (DT) layered implosion driven by a 6.8 ns, 2-shock laser pulse. This paper describes these experiments and comparisons with ICF design code simulations. Backlit radiography of a tritium-hydrogen-deuterium (THD) layered capsule demonstrated an ablator implosion velocity of 385 km/s with a slightly oblate hot spot shape. Other diagnostics suggested an asymmetric compressed fuel layer. A streak camera-based hot spot self-emission diagnostic (SPIDER) showed a double-peaked history of the capsule self-emission. Simulations suggest that this is a signature of low quality hot spot formation. Changes to the laser pulse and pointing for a subsequent DT implosion resulted in a higher temperature, prolate hot spot and a thermonuclear yield of 1.8 × 10{sup 15} neutrons, 40% of the 1D simulated yield.

  4. Catheter ablation.

    PubMed

    Fromer, M; Shenasa, M

    1991-02-01

    Catheter ablation is gaining increasing interest for the therapy of symptomatic, sustained arrhythmias of various origins. The scope of this review is to give an overview of the biophysical aspects and major characteristics of some of the most widely used energy sources in catheter ablation, e.g., the discharge of conventional defibrillators, modified defibrillators, laser light, and radiofrequency current application. Results from animal studies are considered to explain the basic mechanisms of catheter ablation. The recent achievements with the use of radiofrequency current to modify or ablate cardiac conduction properties are outlined in more detail.

  5. A multiplier-based method of generating stochastic areal rainfall from point rainfalls

    NASA Astrophysics Data System (ADS)

    Ndiritu, J. G.

    Catchment modelling for water resources assessment is still mainly based on rain gauge measurements as these are more easily available and cover longer periods than radar and satellite-based measurements. Rain gauges however measure the rain falling on an extremely small proportion of the catchment and the areal rainfall obtained from these point measurements are consequently substantially uncertain. These uncertainties in areal rainfall estimation are generally ignored and the need to assess their impact on catchment modelling and water resources assessment is therefore imperative. A method that stochastically generates daily areal rainfall from point rainfall using multiplicative perturbations as a means of dealing with these uncertainties is developed and tested on the Berg catchment in the Western Cape of South Africa. The differences in areal rainfall obtained by alternately omitting some of the rain gauges are used to obtain a population of plausible multiplicative perturbations. Upper bounds on the applicable perturbations are set to prevent the generation of unrealistically large rainfall and to obtain unbiased stochastic rainfall. The perturbations within the set bounds are then fitted into probability density functions to stochastically generate the perturbations to impose on areal rainfall. By using 100 randomly-initialized calibrations of the AWBM catchment model and Sequent Peak Analysis, the effects of incorporating areal rainfall uncertainties on storage-yield-reliability analysis are assessed. Incorporating rainfall uncertainty is found to reduce the required storage by up to 20%. Rainfall uncertainty also increases flow-duration variability considerably and reduces the median flow-duration values by an average of about 20%.

  6. The relative contributions of forest growth and areal expansion to forest biomass carbon

    NASA Astrophysics Data System (ADS)

    Li, P.; Zhu, J.; Hu, H.; Guo, Z.; Pan, Y.; Birdsey, R.; Fang, J.

    2016-01-01

    Forests play a leading role in regional and global terrestrial carbon (C) cycles. Changes in C sequestration within forests can be attributed to areal expansion (increase in forest area) and forest growth (increase in biomass density). Detailed assessment of the relative contributions of areal expansion and forest growth to C sinks is crucial to reveal the mechanisms that control forest C sinks and it is helpful for developing sustainable forest management policies in the face of climate change. Using the Forest Identity concept and forest inventory data, this study quantified the spatial and temporal changes in the relative contributions of forest areal expansion and increased biomass growth to China's forest biomass C sinks from 1977 to 2008. Over the last 30 years, the areal expansion of forests has been a larger contributor to C sinks than forest growth for planted forests in China (62.2 % vs. 37.8 %). However, for natural forests, forest growth has made a larger contribution than areal expansion (60.4 % vs. 39.6 %). For all forests (planted and natural forests), growth in area and density has contributed equally to the total C sinks of forest biomass in China (50.4 % vs. 49.6 %).The relative contribution of forest growth of planted forests showed an increasing trend from an initial 25.3 % to 61.0 % in the later period of 1998 to 2003, but for natural forests, the relative contributions were variable without clear trends, owing to the drastic changes in forest area and biomass density over the last 30 years. Our findings suggest that afforestation will continue to increase the C sink of China's forests in the future, subject to sustainable forest growth after the establishment of plantations.

  7. Modification of polyimide wetting properties by laser ablated conical microstructures

    NASA Astrophysics Data System (ADS)

    Least, Brandon T.; Willis, David A.

    2013-05-01

    Laser texturing of Kapton® HN polyimide was performed by low-fluence ablation using a pulsed, frequency tripled (349 nm) Nd:YLF laser. The laser was scanned in two dimensions in order to generate texture over a large area. The laser overlap percentage and fluence were varied and the resulting texture was studied. The texture features were inspected by electron microscopy and energy dispersive X-Ray spectroscopy (EDS), while the static contact angle of de-ionized water was measured by a contact angle goniometer. Rounded bump features were formed at all fluences, which decreased in areal density with fluence and number of laser pulses. Conical microstructures or "cones" were also formed at most fluences. Cones were larger than the bumps and thus had lower areal density, which increased as a function of the number of laser pulses. The polyimide was hydrophilic before texturing, with a contact angle of approximately 76°. For most of the experimental conditions the contact angle increased as a result of texturing, with the contact angle exceeding 90° for some textured surfaces, and reaching values as high as 118°. In general, the surfaces with significant increases in contact angle had high density of texture features, either bumps or cones. The surfaces that experienced a decrease in contact angle generally had low density of texture features. The increase in contact angle from a wetting (θ < 90°) to a nonwetting surface (θ > 90°) cannot be explained by texturing alone. EDS measurements indicate that textured regions had higher carbon content than the untextured regions due to depletion of oxygen species. The increase in carbon content relative to the oxygen content increased the native contact angle of the surface, causing the transition from hydrophilic to hydrophobic behavior. The contact angle of a textured surface increased as the relative spacing of features (diameter to spacing) decreased.

  8. Observations of multimode perturbation decay at non-accelerating, soft x-ray driven ablation fronts

    SciTech Connect

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

    2012-12-15

    Minimizing the growth of hydrodynamic instabilities is a fundamental design issue facing the achievement of thermonuclear ignition and burn with Inertial Confinement Fusion (ICF). The thin capsules and extreme accelerations found in ICF make it an inherently unstable system primarily to Rayleigh-Taylor (RT) occurring at the ablation front. A potential mechanism by which perturbations at the outer capsule surface can be reduced lies in the already present ablative Richtmyer-Meshkov (RM) effect, which operates during the first shock transit of the ablator. At present, the available Equation of State (EOS) models predict a wide range of behavior for the ablative RM oscillations of multimode isolated defects on plastic (CH) capsules. To resolve these differences, we conducted experiments at the OMEGA Laser Facility [T. R. Boehly et al., Optics Comm. 133 (1997)] that measured the evolution of gaussian-shaped bumps driven by soft x-ray ablation from a halfraum. Shock speeds in the CH target were measured to reach 15 {mu}m/ns for halfraum radiation temperatures of 70 eV lasting for up to 7 ns. The evolution of gaussian-shaped bumps of different widths and heights were measured using on-axis x-ray radiography at up to 37 Multiplication-Sign magnification. Bumps with initial widths of 34 and 44 {mu}m FWHM were found to grow by 3 Multiplication-Sign their initial areal density and then saturate out to 6 ns due to lateral compression of the bump characteristic of the formation of a rippled shock front propagating into the solid target. Narrower 17 {mu}m FWHM bumps, on the other hand, grew by roughly 2 Multiplication-Sign followed immediately by a decrease back to initial values of areal density out to 7 ns, which largely agrees with both LEOS 5310 and SESAME 7592 EOS predictions. The difference in observed behavior suggests that high spatial frequency modes found in narrower bumps are needed to significantly affect the ablation front profile on shorter time scales.

  9. Thermal response and ablation characteristics of light weight ceramic ablators

    NASA Technical Reports Server (NTRS)

    Tran, Huy K.; Rasky, Daniel J.; Esfahani, Lili

    1993-01-01

    An account is given of the thermal performance and ablation characteristics of the NASA-Ames Lightweight Ceramic Ablators (LCAs) in supersonic, high-enthalpy convective environments, which use low density ceramic or carbon fiber matrices as substrates for main structural support, with organic resin fillers. LCA densities are in the 0.224-1.282 g/cu cm range. In-depth temperature data have been obtained to determine thermal penetration depths and conductivity. The addition of SiC and PPMA is noted to significantly improve the ablation performance of LCAs with silica substrates. Carbon-based LCAs are the most mass-efficient at high flux levels.

  10. BOREAS HYD-4 Areal Snow Course Data

    NASA Technical Reports Server (NTRS)

    Hall, Forrest G. (Editor); Knapp, David E. (Editor); Metcalfe, John R.; Goodison, Barry E.; Walker, Anne; Smith, David E. (Technical Monitor)

    2000-01-01

    The Boreal Ecosystem-Atmosphere Study (BOREAS) Hydrology (HYD)-4 team focused on collecting data during the 1994 winter focused field campaign (FFCW) to improve the understanding of winter processes within the boreal forest. Knowledge of snow cover and its variability in the boreal forest is fundamental if BOREAS is to achieve its goals of understanding the processes and states involved in the exchange of energy and water. The development and validation of remote sensing algorithms will provide the means to extend the knowledge of these processes and states from the local to the regional scale. A specific thrust of the hydrology research is the development and validation of snow cover algorithms from airborne passive microwave measurements. Airborne remote sensing data (gamma, passive microwave) were acquired along a series of flight lines established in the vicinity of the BOREAS study areas. Ground snow surveys were conducted along selected sections of these aircraft flight lines. These calibration segments were typically 10-20 km in length, and ground data were collected at one to two kilometer intervals. The data are provided in tabular ASCII files. The HYD-04 areal snow course data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  11. Thermal ablation.

    PubMed

    Webb, Heather; Lubner, Meghan G; Hinshaw, J Louis

    2011-04-01

    Image-guided tumor ablation refers to a group of treatment modalities that have emerged during the past 2 decades as important tools in the treatment of a wide range of tumors throughout the body. Although most widely recognized in the treatment of hepatic and renal malignancies, the role of thermal ablation has expanded to include lesions of the lung, breast, prostate, bone, as well as other organs and its clinical applications continue to increase. In the following article, we discuss the major thermal ablation modalities, their respective strengths and weaknesses, potential complications and how to avoid them, as well as possible future applications.

  12. Catheter Ablation

    MedlinePlus

    ... you during the procedure. Machines will measure your heart’s activity. All types of ablation require cardiac catheterization to place flexible tubes, or catheters, inside your heart to make the scars. Your doctor will clean ...

  13. A prepositioned areal electrofishing apparatus for sampling stream habitats

    USGS Publications Warehouse

    Fisher, William L.; Brown, Marshall E.

    1993-01-01

    We describe the design, use, and sampling characteristics ofan electrofishing apparatus used to sample fish in stream habitats. The apparatus uses two prepositioned areal electrofishing devices (PAED) of different designs, a bottom parallel electrode PAED and a suspended dropper electrode PAED. To determine the effective immobilization ranges of the PAEDs, we evaluated intensities and shapes of the PAEDs' electrical fields, and the electroshock responses of fish in cages in concrete tanks and in four streams in Alabama with different water conductivities. Electroshock responses indicated that complete immobilization occurred at voltage gradients of 1.0 V/cm or higher (voltage drop, 400 V AC), as far as 35 cm from the PAED electrodes, although some fish were immobilized up to 65 cm away at 0.3 V/cm. We estimated the immobilization (stun) power density threshold to be about 10 μW/cm3. Stream evaluations of the PAEDs revealed that higher voltages were needed to immobilize fish at lower (35 μS/cm) and higher (120 and 125 μS/cm) water conductivities, whereas lower voltages were required at an intermediate conductivity (60 μS/cm). These results conformed with the predictions of power transfer theory and underscored the need to calibrate PAEDs to stream conductivities to standardize the effective sampling range.

  14. Combining remotely sensed and other measurements for hydrologic areal averages

    NASA Technical Reports Server (NTRS)

    Johnson, E. R.; Peck, E. L.; Keefer, T. N.

    1982-01-01

    A method is described for combining measurements of hydrologic variables of various sampling geometries and measurement accuracies to produce an estimated mean areal value over a watershed and a measure of the accuracy of the mean areal value. The method provides a means to integrate measurements from conventional hydrological networks and remote sensing. The resulting areal averages can be used to enhance a wide variety of hydrological applications including basin modeling. The correlation area method assigns weights to each available measurement (point, line, or areal) based on the area of the basin most accurately represented by the measurement. The statistical characteristics of the accuracy of the various measurement technologies and of the random fields of the hydrologic variables used in the study (water equivalent of the snow cover and soil moisture) required to implement the method are discussed.

  15. An Areal Isotropic Spline Filter for Surface Metrology.

    PubMed

    Zhang, Hao; Tong, Mingsi; Chu, Wei

    2015-01-01

    This paper deals with the application of the spline filter as an areal filter for surface metrology. A profile (2D) filter is often applied in orthogonal directions to yield an areal filter for a three-dimensional (3D) measurement. Unlike the Gaussian filter, the spline filter presents an anisotropic characteristic when used as an areal filter. This disadvantage hampers the wide application of spline filters for evaluation and analysis of areal surface topography. An approximation method is proposed in this paper to overcome the problem. In this method, a profile high-order spline filter serial is constructed to approximate the filtering characteristic of the Gaussian filter. Then an areal filter with isotropic characteristic is composed by implementing the profile spline filter in the orthogonal directions. It is demonstrated that the constructed areal filter has two important features for surface metrology: an isotropic amplitude characteristic and no end effects. Some examples of applying this method on simulated and practical surfaces are analyzed.

  16. Estimation of multidimensional precipitation parameters by areal estimates of oceanic rainfall

    NASA Technical Reports Server (NTRS)

    Valdes, J. B.; Nakamoto, S.; Shen, S. S. P.; North, G. R.

    1990-01-01

    The parameters of the multidimensional precipitation model proposed by Waymire et al. (1984) are estimated using the areal-averaged radar measurements of precipitation of the Global Atlantic Tropical Experiment (GATE) data set. The procedure followed was the fitting of the first- and second-order moments at different aggregation scales by nonlinear regression techniques. The numerical estimates of the parameters using different subsets of GATE information were reasonably stable, i.e., they were not affected by changes of the area-averaging size, temporal length of the records, and percentage of areal coverage of rainfall. This suggests that the estimation procedure is relatively robust and suitable to estimate the parameters of the multidimensional model in areas of sparse density of rain gages. The use of the space-time spectrum of rainfall to help in the determination of sampling errors due to intermittent visits of future space-borne low-altitude sensors of precipitation is also discussed.

  17. Dry-Processed, Binder-Free Holey Graphene Electrodes for Supercapacitors with Ultrahigh Areal Loadings.

    PubMed

    Walsh, Evan D; Han, Xiaogang; Lacey, Steven D; Kim, Jae-Woo; Connell, John W; Hu, Liangbing; Lin, Yi

    2016-11-02

    For commercial applications, the need for smaller footprint energy storage devices requires more energy to be stored per unit area. Carbon nanomaterials, especially graphene, have been studied as supercapacitor electrodes and can achieve high gravimetric capacities affording high gravimetric energy densities. However, most nanocarbon-based electrodes exhibit a significant decrease in their areal capacitances when scaled to the high mass loadings typically used in commercially available cells (∼10 mg/cm(2)). One of the reasons for this behavior is that the additional surface area in thick electrodes is not readily accessible by electrolyte ions due to the large tortuosity. Furthermore, the fabrication of such electrodes often involves complicated processes that limit the potential for mass production. Here, holey graphene electrodes for supercapacitors that are scalable in both production and areal capacitance are presented. The lateral surface porosity on the graphene sheets was created using a facile single-step air oxidation method, and the resultant holey graphene was compacted under ambient conditions into mechanically robust monolithic shapes that can be directly used as binder-free electrodes. In comparison, pristine graphene discs under similar binder-free compression molding conditions were extremely brittle and thus not deemed useful for electrode applications. The coin cell supercapacitors, based on these holey graphene electrodes exhibited small variations in gravimetric capacitance over a wide range of areal mass loadings (∼1-30 mg/cm(2)) at current densities as high as 30 mA/cm(2), resulting in the near-linear increase of the areal capacitance (F/cm(2)) with the mass loading. The prospects of the presented method for facile binder-free ultrathick graphene electrode fabrication are discussed.

  18. Streaked Imaging of Ablative Richtmyer--Meshkov Growth in ICF Targets on OMEGA

    NASA Astrophysics Data System (ADS)

    Gotchev, O. V.; Goncharov, V. N.; Jaanimagi, P. A.; Knauer, J. P.; Meyerhofer, D. D.

    2003-10-01

    Dynamic overpressure sets the growth rate of the ablative Richtmyer--Meshkov (RM) instability and the seeds for subsequent growth of perturbations due to the Rayleigh--Taylor instability in directly driven ICF targets. It leads to temporal oscillations of the perturbed ablation front, which have been predicted analytically,(V.N. Goncharov, Phys. Rev. Lett. 82), 2091 (1999). observed in 2-D ORCHID hydrodynamic simulations, and measured experimentally.(Y. Aglitskiy et al.), Phys. Plasmas 9, 2264 (2002). These predictions were verified on OMEGA by measuring the perturbation amplitudes and frequencies directly, through face-on x-ray radiography. Experiments with a high-resolution, Ir-coated Kirkpatrick--Baez microscope, coupled to a high-current streak tube, provided a continuous record of the target areal density during shock transit, while it was dominated by the evolution of the RM instability. Planar plastic targets with variable thicknesses (30 to 60 μm) and single-mode (λ = 10 to 30 μm) ripples on the front surface were irradiated with 1.5-ns square UV laser pulses with intensities---ranging from 5 × 10^13 W/cm^2 to 4 × 10^14 W/cm^2. Results clearly indicate a phase reversal in the evolution of the target areal density perturbations, in good agreement with theory and simulation. The predicted dependence of the oscillation period on laser intensity and modulation wavelength was quantified. This work was supported by the U.S. Department of Energy Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460.

  19. Percutaneous transapical access for pulmonary vein mapping and ablation in a porcine model with a new high-density electroanatomical mapping system

    PubMed Central

    Bollmann, Andreas; Kosiuk, Jedrzej; Hilbert, Sebastian; John, Silke; Hindricks, Gerhard

    2015-01-01

    Introduction: The porcine model is generally accepted for the development and testing of new forms oftherapy including ablation of atrial fibrillation (AF). However, the challenging left atrial (LA) and pulmonary vein (PV) anatomy enables only limited percutaneous catheter-based PV access. Results: Here we present I) an alternative percutaneous transapical access, which enables easy and safe retrograde transmitral LA and PV mapping and ablation; II) early experience of LA mapping and successful circumferential PV isolation with novel mapping system (RhythmiaTM) and new generation of ablation catheter equipped with micro electrodes (IntellaTip MiFi). Conclusion: Although the experience with the transapical approach is limited, the initial results are promising as this may offer an alternative approach for tasting new technologies and translational research. PMID:26550175

  20. Conductive MOF electrodes for stable supercapacitors with high areal capacitance

    NASA Astrophysics Data System (ADS)

    Sheberla, Dennis; Bachman, John C.; Elias, Joseph S.; Sun, Cheng-Jun; Shao-Horn, Yang; Dincă, Mircea

    2016-10-01

    Owing to their high power density and superior cyclability relative to batteries, electrochemical double layer capacitors (EDLCs) have emerged as an important electrical energy storage technology that will play a critical role in the large-scale deployment of intermittent renewable energy sources, smart power grids, and electrical vehicles. Because the capacitance and charge-discharge rates of EDLCs scale with surface area and electrical conductivity, respectively, porous carbons such as activated carbon, carbon nanotubes and crosslinked or holey graphenes are used exclusively as the active electrode materials in EDLCs. One class of materials whose surface area far exceeds that of activated carbons, potentially allowing them to challenge the dominance of carbon electrodes in EDLCs, is metal-organic frameworks (MOFs). The high porosity of MOFs, however, is conventionally coupled to very poor electrical conductivity, which has thus far prevented the use of these materials as active electrodes in EDLCs. Here, we show that Ni3(2,3,6,7,10,11-hexaiminotriphenylene)2 (Ni3(HITP)2), a MOF with high electrical conductivity, can serve as the sole electrode material in an EDLC. This is the first example of a supercapacitor made entirely from neat MOFs as active materials, without conductive additives or other binders. The MOF-based device shows an areal capacitance that exceeds those of most carbon-based materials and capacity retention greater than 90% over 10,000 cycles, in line with commercial devices. Given the established structural and compositional tunability of MOFs, these results herald the advent of a new generation of supercapacitors whose active electrode materials can be tuned rationally, at the molecular level.

  1. Conductive MOF electrodes for stable supercapacitors with high areal capacitance.

    PubMed

    Sheberla, Dennis; Bachman, John C; Elias, Joseph S; Sun, Cheng-Jun; Shao-Horn, Yang; Dincă, Mircea

    2017-02-01

    Owing to their high power density and superior cyclability relative to batteries, electrochemical double layer capacitors (EDLCs) have emerged as an important electrical energy storage technology that will play a critical role in the large-scale deployment of intermittent renewable energy sources, smart power grids, and electrical vehicles. Because the capacitance and charge-discharge rates of EDLCs scale with surface area and electrical conductivity, respectively, porous carbons such as activated carbon, carbon nanotubes and crosslinked or holey graphenes are used exclusively as the active electrode materials in EDLCs. One class of materials whose surface area far exceeds that of activated carbons, potentially allowing them to challenge the dominance of carbon electrodes in EDLCs, is metal-organic frameworks (MOFs). The high porosity of MOFs, however, is conventionally coupled to very poor electrical conductivity, which has thus far prevented the use of these materials as active electrodes in EDLCs. Here, we show that Ni3(2,3,6,7,10,11-hexaiminotriphenylene)2 (Ni3(HITP)2), a MOF with high electrical conductivity, can serve as the sole electrode material in an EDLC. This is the first example of a supercapacitor made entirely from neat MOFs as active materials, without conductive additives or other binders. The MOF-based device shows an areal capacitance that exceeds those of most carbon-based materials and capacity retention greater than 90% over 10,000 cycles, in line with commercial devices. Given the established structural and compositional tunability of MOFs, these results herald the advent of a new generation of supercapacitors whose active electrode materials can be tuned rationally, at the molecular level.

  2. Effects of spatial variability and scale on areal -average evapotranspiration

    NASA Technical Reports Server (NTRS)

    Famiglietti, J. S.; Wood, Eric F.

    1993-01-01

    This paper explores the effect of spatial variability and scale on areally-averaged evapotranspiration. A spatially-distributed water and energy balance model is employed to determine the effect of explicit patterns of model parameters and atmospheric forcing on modeled areally-averaged evapotranspiration over a range of increasing spatial scales. The analysis is performed from the local scale to the catchment scale. The study area is King's Creek catchment, an 11.7 sq km watershed located on the native tallgrass prairie of Kansas. The dominant controls on the scaling behavior of catchment-average evapotranspiration are investigated by simulation, as is the existence of a threshold scale for evapotranspiration modeling, with implications for explicit versus statistical representation of important process controls. It appears that some of our findings are fairly general, and will therefore provide a framework for understanding the scaling behavior of areally-averaged evapotranspiration at the catchment and larger scales.

  3. Relationships in Areal Variability: The Ross Sea Polynya and Ice

    NASA Astrophysics Data System (ADS)

    Ward, Jason Michael

    General increases in Antarctic sea ice coverage occur primarily in the Ross Sea. This study investigates the Ross Sea Polynya's relationship with the Ross Sea ice areal coverage. A unique, relatively long term Ross Sea Polynya area dataset was created through the application of the Polynya Signature Simulation Method (PSSM) onto Special Sensor Microwave Imager (SSM/I) data inputs. Bivariate regression analyses were used to determine the relationships, at the 95% confidence level, between Ross Sea Polynya and ice areal trends, annual seasonalities, and anomalies at the full temporal scale as well as the monthly level. Polynya and sea ice have significant positive relationships in the late austral summer and early spring (February to March), and a significant negative relationship in the late austral winter (August). The areal anomalies only had a significant relationship in February, while the trends were not correlated at any time.

  4. Evidentials and Areal Typology: A Case Study from Amazonia.

    ERIC Educational Resources Information Center

    Aikhenvald, Alexandra Y.; Dixon, R. M. W.

    1998-01-01

    A discussion of areal linguistics and Amazonian languages looks at common properties of Amazonian languages, the occurrence, origins, and development of evidentiality systems in a number of those languages, and patterns of grammatical diffusion. Concludes that communities in the Amazonian linguistics area share common beliefs, mental attitudes,…

  5. copCAR: A Flexible Regression Model for Areal Data.

    PubMed

    Hughes, John

    2015-09-16

    Non-Gaussian spatial data are common in many fields. When fitting regressions for such data, one needs to account for spatial dependence to ensure reliable inference for the regression coefficients. The two most commonly used regression models for spatially aggregated data are the automodel and the areal generalized linear mixed model (GLMM). These models induce spatial dependence in different ways but share the smoothing approach, which is intuitive but problematic. This article develops a new regression model for areal data. The new model is called copCAR because it is copula-based and employs the areal GLMM's conditional autoregression (CAR). copCAR overcomes many of the drawbacks of the automodel and the areal GLMM. Specifically, copCAR (1) is flexible and intuitive, (2) permits positive spatial dependence for all types of data, (3) permits efficient computation, and (4) provides reliable spatial regression inference and information about dependence strength. An implementation is provided by R package copCAR, which is available from the Comprehensive R Archive Network, and supplementary materials are available online.

  6. Dip-angle influence on areal DNAPL recovery by co-solvent flooding with and without pre-flooding.

    PubMed

    Boyd, Glen R; Li, Minghua; Husserl, Johana; Ocampo-Gómez, Ana M

    2006-01-10

    A two-dimensional (2D) laboratory model was used to study effects of gravity on areal recovery of a representative dense non-aqueous phase liquid (DNAPL) contaminant by an alcohol pre-flood and co-solvent flood in dipping aquifers. Recent studies have demonstrated that injection of alcohol and co-solvent solutions can be used to reduce in-situ the density of DNAPL globules and displace the contaminant from the source zone. However, contact with aqueous alcohol reduces interfacial tension and causes DNAPL swelling, thus facilitating risk of uncontrolled downward DNAPL migration. The 2D laboratory model was operated with constant background gradient flow and a DNAPL spill was simulated using tetrachloroethene (PCE). The spill was dispersed to a trapped, immobile PCE saturation by a water flood. Areal PCE recovery was studied using a double-triangle well pattern to simulate a remediation scheme consisting of an alcohol pre-flood using aqueous isobutanol ( approximately 10% vol.) followed by a co-solvent flood using a solution of ethylene glycol (65%) and 1-propanol (35%). Experiments were conducted with the 2D model oriented in the horizontal plane and compared to experiments at the 15 degrees and 30 degrees dip-angle orientations. Injection was applied either in the downward or upward direction of flow. Experimental results were compared to theoretical predictions for flood front stability and used to evaluate effects of gravity on areal PCE recovery. Sensitivity experiments were performed to evaluate effects of the alcohol pre-flood on PCE areal recovery. For experiments conducted with the alcohol pre-flood and the 2D model oriented in the horizontal plane, results indicate that 89-93% of source zone PCE was recovered. With injection oriented downward, results indicate that areal PCE recovery was 70-77% for a 15 degrees dip angle and 57-59% for a 30 degrees dip angle. With injection oriented upward, results indicate that areal PCE recovery was 57-60% at the 30

  7. Studies on the Surface Morphology and Orientation of CeO2 Films Deposited by Pulsed Laser Ablation

    NASA Astrophysics Data System (ADS)

    Develos, Katherine; Kusunoki, Masanobu; Ohshima, Shigetoshi

    1998-11-01

    We studied the surface morphology and orientation of CeO2 films grown by pulsed laser ablation (PLA) on r-cut (1\\=102) Al2O3 substrates and evaluated the effects of predeposition annealing conditions of Al2O3 and film thickness of CeO2. The annealing of Al2O3 substrates improves the smoothness of the surface and performing this in high vacuum leads to better crystallinity and orientation of deposited CeO2 films compared to those annealed in oxygen. A critical value of the film thickness was found beyond which the surface roughness increases abruptly. Atomic force microscopy (AFM) study showed that the surface of CeO2 films is characterized by a mazelike pattern. Increasing the film thickness leads to the formation of larger islands which cause the increase in the surface roughness of the films. The areal density and height of these islands increased with film thickness.

  8. Optimizing areal capacities through understanding the limitations of lithium-ion electrodes

    SciTech Connect

    Gallagher, Kevin G.; Trask, Stephen E.; Bauer, Christoph; Woehrle, Thomas; Lux, Simon; Tschech, Matthias; Polzin, Bryant J.; Ha, Seungbum; Long, Brandon R.; Wu, Qingliu; Lu, Wenquan; Dees, Dennis W.; Jansen, Andrew N.

    2016-01-01

    Increasing the areal capacity or electrode thickness in lithium ion batteries is one possible means to increase pack level energy density while simultaneously lowering cost. The physics that limit use of high areal capacity as a function of battery power to energy ratio are poorly understood and thus most currently produced automotive lithium ion cells utilize modest loadings to ensure long life over the vehicle battery operation. Here we show electrolyte transport limits the utilization of the positive electrode at critical C-rates during discharge; whereas, a combination of electrolyte transport and polarization lead to lithium plating in the graphite electrode during charge. Experimental measurements are compared with theoretical predictions based on concentrated solution and porous electrode theories. An analytical expression is derived to provide design criteria for long lived operation based on the physical properties of the electrode and electrolyte. Finally, a guideline is proposed that graphite cells should avoid charge current densities near or above 4 mA/cm2 unless additional precautions have been made to avoid deleterious side reaction.

  9. Experiments on Dynamic Overpressure Stabilization of Ablative Richtmyer--Meshkov Growth in ICF Targets on OMEGA

    NASA Astrophysics Data System (ADS)

    Gotchev, O. V.; Goncharov, V. N.; Jaanimagi, P. A.; Knauer, J. P.; Meyerhofer, D. D.

    2002-11-01

    Dynamic overpressure sets the growth rate of the ablative Richtmyer--Meshkov (RM) instability and the late-time imprint levels in directly driven ICF targets. It leads to temporal oscillations of the perturbed ablation front, which have been predicted analytically and observed experimentally,(Y. Aglitskiy et al.), Phys. Plasmas 9, 2264 (2002). and in 2-D ORCHID simulations. These predictions were verified on OMEGA by measuring the perturbation amplitudes and frequencies directly with an x-ray framing camera through face-on x-ray radiography. Planar plastic targets with variable thickness (20 to 60 μm) and single-mode (λ = 10 to 30 μm) ripples on the front surface were irradiated with 1.5-ns square UV laser pulses at maximum energy. Results clearly indicate a phase reversal in the evolution of the target areal density perturbations, in good agreement with theory and simulation. Nonlinearity in the evolution of the preimposed mode, resulting in an enriched spectrum, was observed for initial amplitudes previously believed to develop linearly with time. Upcoming experiments with a high-resolution, streaked imager, will allow for the detailed recording of the evolution of the RM instability and the competing stabilization effect. This work was supported by the U.S. DOE Office of Inertial Confinement Fusion under Cooperative Agreement No. DE-FC03-92SF19460.

  10. Pellet ablation and ablation model development

    SciTech Connect

    Houlberg, W.A.

    1989-01-01

    A broad survey of pellet ablation is given, based primarily on information presented at this meeting. The implications of various experimental observations for ablation theory are derived from qualitative arguments of the physics involved. The major elements of a more complete ablation theory are then outlined in terms of these observations. This is followed by a few suggestions on improving the connections between theory and experimental results through examination of ablation data. Although this is a rather aggressive undertaking for such a brief (and undoubtedly incomplete) assessment, some of the discussion may help us advance the understanding of pellet ablation. 17 refs.

  11. Areal rainfall estimation using moving cars as rain gauges - modeling study and laboratory experiment

    NASA Astrophysics Data System (ADS)

    Rabiei, E.; Haberlandt, U.; Sester, M.; Fitzner, D.

    2012-04-01

    Areal rainfall estimation is still one of the concerns in hydrological analyses. Low density of the conventional rainfall measurement devices as well as the errors in radar data developed the new idea of using moving cars, called raincars, as a possible new source for measuring rainfall. This idea is easily technically feasible if the cars are provided with GPS and a small memory chip for recording the coordinates, car speed and data from the sensors, either for the frequency measurement of the wipers or the optical sensors on cars. According to the modeling study, which is done on the Bode catchment in Germany, a high number of possibly inaccurate sensors, raincars, provide more reliable areal rainfall estimation than a lower number of highly accurate, stationary sensors. In this study, data for the stationary gauges and the cars are extracted from the radar data. A valid relationship between wiper frequency and rainfall with a known error is assumed where the radar data is considered as the reference. Areal precipitation is estimated by different interpolation techniques, ordinary kriging for the stationary stations and indicator kriging for the cars. The results are then compared and evaluated with the reference, radar. After proving the feasibility of the hypothesis in the modeling study, field and laboratory experiment have been arranged. A certain number of cars has been equipped with sensors and in the laboratory, to produce the rainfall as close as possible to nature, sprinkler irrigation system has been designed for producing different rain intensities, from 1 mm/hr to 55 mm/hr. Here, we can develop an empirical approach for the relationship between the wiper frequency and rainfall intensity as well as for the optical sensors on the cars under different rainfall intensities.

  12. Laser ablation studies of concrete

    SciTech Connect

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

    1999-10-20

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

  13. Microwave Assisted Synthesis of Porous NiCo2O4 Microspheres: Application as High Performance Asymmetric and Symmetric Supercapacitors with Large Areal Capacitance

    NASA Astrophysics Data System (ADS)

    Khalid, Syed; Cao, Chuanbao; Wang, Lin; Zhu, Youqi

    2016-03-01

    Large areal capacitance is essentially required to integrate the energy storage devices at the microscale electronic appliances. Energy storage devices based on metal oxides are mostly fabricated with low mass loading per unit area which demonstrated low areal capacitance. It is still a challenge to fabricate supercapacitor devices of porous metal oxides with large areal capacitance. Herein we report microwave method followed by a pyrolysis of the as-prepared precursor is used to synthesize porous nickel cobaltite microspheres. Porous NiCo2O4 microspheres are capable to deliver large areal capacitance due to their high specific surface area and small crystallite size. The facile strategy is successfully demonstrated to fabricate aqueous-based asymmetric & symmetric supercapacitor devices of porous NiCo2O4 microspheres with high mass loading of electroactive materials. The asymmetric & symmetric devices exhibit maximum areal capacitance and energy density of 380 mF cm‑2 & 19.1 Wh Kg‑1 and 194 mF cm‑2 & 4.5 Wh Kg‑1 (based on total mass loading of 6.25 & 6.0 mg) respectively at current density of 1 mA cm‑2. The successful fabrication of symmetric device also indicates that NiCo2O4 can also be used as the negative electrode material for futuristic asymmetric devices.

  14. Microwave Assisted Synthesis of Porous NiCo2O4 Microspheres: Application as High Performance Asymmetric and Symmetric Supercapacitors with Large Areal Capacitance

    PubMed Central

    Khalid, Syed; Cao, Chuanbao; Wang, Lin; Zhu, Youqi

    2016-01-01

    Large areal capacitance is essentially required to integrate the energy storage devices at the microscale electronic appliances. Energy storage devices based on metal oxides are mostly fabricated with low mass loading per unit area which demonstrated low areal capacitance. It is still a challenge to fabricate supercapacitor devices of porous metal oxides with large areal capacitance. Herein we report microwave method followed by a pyrolysis of the as-prepared precursor is used to synthesize porous nickel cobaltite microspheres. Porous NiCo2O4 microspheres are capable to deliver large areal capacitance due to their high specific surface area and small crystallite size. The facile strategy is successfully demonstrated to fabricate aqueous-based asymmetric & symmetric supercapacitor devices of porous NiCo2O4 microspheres with high mass loading of electroactive materials. The asymmetric & symmetric devices exhibit maximum areal capacitance and energy density of 380 mF cm−2 & 19.1 Wh Kg−1 and 194 mF cm−2 & 4.5 Wh Kg−1 (based on total mass loading of 6.25 & 6.0 mg) respectively at current density of 1 mA cm−2. The successful fabrication of symmetric device also indicates that NiCo2O4 can also be used as the negative electrode material for futuristic asymmetric devices. PMID:26936283

  15. Microwave Assisted Synthesis of Porous NiCo2O4 Microspheres: Application as High Performance Asymmetric and Symmetric Supercapacitors with Large Areal Capacitance.

    PubMed

    Khalid, Syed; Cao, Chuanbao; Wang, Lin; Zhu, Youqi

    2016-03-03

    Large areal capacitance is essentially required to integrate the energy storage devices at the microscale electronic appliances. Energy storage devices based on metal oxides are mostly fabricated with low mass loading per unit area which demonstrated low areal capacitance. It is still a challenge to fabricate supercapacitor devices of porous metal oxides with large areal capacitance. Herein we report microwave method followed by a pyrolysis of the as-prepared precursor is used to synthesize porous nickel cobaltite microspheres. Porous NiCo2O4 microspheres are capable to deliver large areal capacitance due to their high specific surface area and small crystallite size. The facile strategy is successfully demonstrated to fabricate aqueous-based asymmetric &symmetric supercapacitor devices of porous NiCo2O4 microspheres with high mass loading of electroactive materials. The asymmetric &symmetric devices exhibit maximum areal capacitance and energy density of 380 mF cm(-2) &19.1 Wh Kg(-1) and 194 mF cm(-2) &4.5 Wh Kg(-1) (based on total mass loading of 6.25 &6.0 mg) respectively at current density of 1 mA cm(-2). The successful fabrication of symmetric device also indicates that NiCo2O4 can also be used as the negative electrode material for futuristic asymmetric devices.

  16. Numerical simulations of the ablative Rayleigh-Taylor instability in planar inertial-confinement-fusion targets using the FastRad3D code

    NASA Astrophysics Data System (ADS)

    Bates, J. W.; Schmitt, A. J.; Karasik, M.; Zalesak, S. T.

    2016-12-01

    The ablative Rayleigh-Taylor (RT) instability is a central issue in the performance of laser-accelerated inertial-confinement-fusion targets. Historically, the accurate numerical simulation of this instability has been a challenging task for many radiation hydrodynamics codes, particularly when it comes to capturing the ablatively stabilized region of the linear dispersion spectrum and modeling ab initio perturbations. Here, we present recent results from two-dimensional numerical simulations of the ablative RT instability in planar laser-ablated foils that were performed using the Eulerian code FastRad3D. Our study considers polystyrene, (cryogenic) deuterium-tritium, and beryllium target materials, quarter- and third-micron laser light, and low and high laser intensities. An initial single-mode surface perturbation is modeled in our simulations as a small modulation to the target mass density and the ablative RT growth-rate is calculated from the time history of areal-mass variations once the target reaches a steady-state acceleration. By performing a sequence of such simulations with different perturbation wavelengths, we generate a discrete dispersion spectrum for each of our examples and find that in all cases the linear RT growth-rate γ is well described by an expression of the form γ = α [ k g / ( 1 + ɛ k L m ) ] 1 / 2 - β k V a , where k is the perturbation wavenumber, g is the acceleration of the target, Lm is the minimum density scale-length, Va is the ablation velocity, and ɛ is either one or zero. The dimensionless coefficients α and β in the above formula depend on the particular target and laser parameters and are determined from two-dimensional simulation results through the use of a nonlinear curve-fitting procedure. While our findings are generally consistent with those of Betti et al. (Phys. Plasmas 5, 1446 (1998)), the ablative RT growth-rates predicted in this investigation are somewhat smaller than the values previously reported for the

  17. Flexible Ablators

    NASA Technical Reports Server (NTRS)

    Stackpoole, Margaret M. (Inventor); Ghandehari, Ehson M. (Inventor); Thornton, Jeremy J. (Inventor); Covington, Melmoth Alan (Inventor)

    2017-01-01

    A low-density article comprising a flexible substrate and a pyrolizable material impregnated therein, methods of preparing, and devices using the article are disclosed. The pyrolizable material pyrolizes above 350 C and does not flow at temperatures below the pyrolysis temperature. The low-density article remains flexible after impregnation and continues to remain flexible when the pyrolizable material is fully pyrolized.

  18. Thermal Response Simulation of Ultra Light Weight Phenolic Carbon Ablator by the Use of the Ablation Analysis Code

    NASA Astrophysics Data System (ADS)

    Kato, Sumio; Okuyama, Keiichi; Gibo, Kenta; Miyagi, Takuma; Suzuki, Toshiyuki; Fujita, Kazuhisa; Sakai, Takeharu; Nishio, Seiji; Watanabe, Akihiro

    A space vehicle which undergoes the atmospheric re-entry or a planetary entry needs the heat shield system to protect inner equipments against severe aerodynamic heating environments. Charring ablator is usually used for the heat shield system. In order to design the heat shield system, it is necessary to predict the thermal behavior under aerodynamic heating by ablation analysis. A computer code for charring ablation and thermal response analysis is newly developed for simulation of one-dimensional transient thermal behavior of charring ablation materials. The mathematical model for the charring ablation including basic equation and computational method of ablation analysis is briefly described. A new ultra light weight phenolic carbon ablator called LATS (Lightweight Ablator series for Transfer vehicle) was recently developed. Arc-heated tests of the LATS ablator were carried out and measured results of the temperature response and surface mass loss are compared with the simulation results of the ablation analysis program. The agreement between the results of simulation and measurement is found to be good. It is also found that the mathematical model used in the ablation code can be applied to the ablation analysis of the low density LATS ablator.

  19. Aluminum X-ray mass-ablation rate measurements

    DOE PAGES

    Kline, John L.; Hager, Jonathan D.

    2016-10-15

    Measurements of the mass ablation rate of aluminum (Al) have been completed at the Omega Laser Facility. Measurements of the mass-ablation rate show Al is higher than plastic (CH), comparable to high density carbon (HDC), and lower than beryllium. The mass-ablation rate is consistent with predictions using a 1D Lagrangian code, Helios. Lastly, the results suggest Al capsules have a reasonable ablation pressure even with a higher albedo than beryllium or carbon ablators warranting further investigation into the viability of Al capsules for ignition should be pursued.

  20. Radiofrequency Ablation of Liver Tumors

    MedlinePlus

    ... Site Index A-Z Radiofrequency Ablation (RFA) of Liver Tumors Radiofrequency ablation (RFA) is a treatment that ... of Liver Tumors? What is Radiofrequency Ablation of Liver Tumors? Radiofrequency ablation, sometimes referred to as RFA, ...

  1. An Infrared Spectroscopic and Density Functional Theoretical Investigation of the Reaction Products of Laser-Ablated Scandium and Titanium Atoms with Nitric Oxide

    NASA Technical Reports Server (NTRS)

    Bauschlicher, Charles W., Jr.; Kushto, Gary P.; Zhou, Mingfei; Andrews, Lester; Arnold, James (Technical Monitor)

    1998-01-01

    Laser-ablated Sc and Ti atoms have been reacted with NO during condensation in excess argon. Matrix infrared spectra show that the major products are the side bonded Sc[NO] species and the inserted NScO and NTiO molecules based on isotopic substitution (15NI6O and 15N18O) and DIFT calculations of isotopic frequencies, which provide a match for two modes in three isotopic modifications for each molecule. The NScO and NTiO molecules are nitride/oxides with M-O stretching modes only 46-88/cm below the diatomic metal oxides but M-N stretching modes 314-442/cm lower than the diatomic metal nitride molecules. The ScN, ScO, TiN, and TiO molecules are observed as decomposition products. Evidence is also presented for the nitrosyls ScNO and TiNO, the Sc[NO]+ cation, and the NTiO- anion.

  2. Diamond Ablators for Inertial Confinement Fusion

    SciTech Connect

    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.

  3. Toward a comprehensive areal model of earthquake-induced landslides

    USGS Publications Warehouse

    Miles, S.B.; Keefer, D.K.

    2009-01-01

    This paper provides a review of regional-scale modeling of earthquake-induced landslide hazard with respect to the needs for disaster risk reduction and sustainable development. Based on this review, it sets out important research themes and suggests computing with words (CW), a methodology that includes fuzzy logic systems, as a fruitful modeling methodology for addressing many of these research themes. A range of research, reviewed here, has been conducted applying CW to various aspects of earthquake-induced landslide hazard zonation, but none facilitate comprehensive modeling of all types of earthquake-induced landslides. A new comprehensive areal model of earthquake-induced landslides (CAMEL) is introduced here that was developed using fuzzy logic systems. CAMEL provides an integrated framework for modeling all types of earthquake-induced landslides using geographic information systems. CAMEL is designed to facilitate quantitative and qualitative representation of terrain conditions and knowledge about these conditions on the likely areal concentration of each landslide type. CAMEL is highly modifiable and adaptable; new knowledge can be easily added, while existing knowledge can be changed to better match local knowledge and conditions. As such, CAMEL should not be viewed as a complete alternative to other earthquake-induced landslide models. CAMEL provides an open framework for incorporating other models, such as Newmark's displacement method, together with previously incompatible empirical and local knowledge. ?? 2009 ASCE.

  4. Ablative skin resurfacing.

    PubMed

    Chwalek, Jennifer; Goldberg, David J

    2011-01-01

    Ablative skin resurfacing has remained the gold standard for treating photodamage and acne scars since the development of the first CO(2) lasers. CO(2) and Er:YAG lasers emit infrared light, which targets water resulting in tissue contraction and collagen formation. The first ablative laser systems created significant thermal damage resulting in unacceptably high rates of scarring and prolonged healing. Newer devices, such as high-energy pulsed lasers and fractional ablative lasers, are capable of achieving significant improvements with fewer side effects and shorter recovery times. While ablative resurfacing has become safer, careful patient selection is still important to avoid post-treatment scarring, dyspigmentation, and infections. Clinicians utilizing ablative devices need to be aware of possible side effects in order to maximize results and patient satisfaction. This chapter reviews the background of ablative lasers including the types of ablative lasers, mechanism of action, indications for ablative resurfacing, and possible side effects.

  5. Ultrahigh-throughput Generation and Characterization of Cellular Aggregates in Laser-ablated Microwells of Poly(dimethylsiloxane)

    PubMed Central

    Albritton, Jacob L.; Roybal, Jonathon D.; Paulsen, Samantha J.; Calafat, Nick; Flores-Zaher, Jose A.; Farach-Carson, Mary C.; Gibbons, Don L.; Miller, Jordan S.

    2016-01-01

    Aggregates of cells, also known as multicellular aggregates (MCAs), have been used as microscale tissues in the fields of cancer biology, regenerative medicine, and developmental biology for many decades. However, small MCAs (fewer than 100 cells per aggregate) have remained challenging to manufacture in large quantities at high uniformity. Forced aggregation into microwells offers a promising solution for forming consistent aggregates, but commercial sources of microwells are expensive, complicated to manufacture, or lack the surface packing densities that would significantly improve MCA production. To address these concerns, we custom-modified a commercial laser cutter to provide complete control over laser ablation and directly generate microwells in a poly(dimethylsiloxane) (PDMS) substrate. We achieved ultra rapid microwell production speeds (>50,000 microwells/hr) at high areal packing densities (1,800 microwells/cm2) and over large surface areas for cell culture (60 cm2). Variation of the PDMS substrate distance from the laser focal plane during ablation allowed for the generation of microwells with a variety of sizes, contours, and aspect ratios. Casting of high-fidelity microneedle masters in polyurethane allowed for non-ablative microwell reproduction through replica molding. MCAs of human bone marrow derived mesenchymal stem cells (hMSCs), murine 344SQ metastatic adenocarcinoma cells, and human C4-2 prostate cancer cells were generated in our system with high uniformity within 24 hours, and computer vision software aided in the ultra-high-throughput analysis of harvested aggregates. Moreover, MCAs maintained invasive capabilities in 3D migration assays. In particular, 344SQ MCAs demonstrated epithelial lumen formation on Matrigel, and underwent EMT and invasion in the presence of TGF-β. We expect this technique to find broad utility in the generation and cultivation of cancer cell aggregates, primary cell aggregates, and embryoid bodies. PMID:26998251

  6. Facile preparation of polypyrrole/graphene oxide nanocomposites with large areal capacitance using electrochemical codeposition for supercapacitors

    NASA Astrophysics Data System (ADS)

    Zhou, Haihan; Han, Gaoyi; Xiao, Yaoming; Chang, Yunzhen; Zhai, Hua-Jin

    2014-10-01

    A simple and low-cost electrochemical codeposition method has been introduced to fabricate polypyrrole/graphene oxide (PPy/GO) nanocomposites and the areal capacitance of conducting polymer/GO composites is reported for the first time. Fourier transform infrared spectroscopy (FTIR), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) are implemented to determine the PPy/GO nanocomposites are successfully prepared and the interaction between PPy and GO. The as-prepared PPy/GO nanocomposites show the curly sheet-like morphology, superior capacitive behaviors and cyclic stability. Furthermore, the varying deposition time is implemented to investigate the impact of the loading amount on electrochemical behavior of the composites, and a high areal capacitance of 152 mF cm-2 is achieved at 10 mV s-1 CV scan. However, the thicker films caused by the long deposition time would result in larger diffusion resistance of electrolyte ions, consequently exhibit the relatively lower capacitance value at the high current density. The GCD tests indicate moderate deposition time is more suitable for the fast charge/discharge. Considering the very simple and effective synthetic process, the PPy/GO nanocomposites with relatively high areal capacitance are competitive candidate for supercapacitor application, and its capacitive performances can be easily tuned by varying the deposition time.

  7. Large Areal Mass, Mechanically Tough and Freestanding Electrode Based on Heteroatom-doped Carbon Nanofibers for Flexible Supercapacitors.

    PubMed

    Liu, Rong; Ma, Lina; Mei, Jia; Huang, Shu; Yang, Shaoqiang; Li, Enyuan; Yuan, Guohui

    2017-02-21

    A flexible and freestanding supercapacitor electrode with a N,P-co-doped carbon nanofiber network (N,P-CNFs)/graphene (GN) composite loaded on bacterial cellulose (BC) is first designed and fabricated in a simple, low-cost, and effective approach. The porous structure and excellent mechanical properties make the BC paper an ideal substrate that shows a large areal mass of 8 mg cm(-2) . As a result, the flexible N,P-CNFs/GN/BC paper electrode shows appreciable areal capacitance (1990 mF cm(-2) in KOH and 2588 mF cm(-2) in H2 SO4 electrolytes) without sacrificing gravimetric capacitance (248.8 F g(-1) and 323.5 F g(-1) ), exhibits excellent cycling ability (without capacity loss after 20 000 cycles), and remarkable tensile strength (42.8 MPa). By direct coupling of two membrane electrodes, the symmetric supercapacitor delivers a prominent areal capacitance of 690 mF cm(-2) in KOH and 898 mF cm(-2) in H2 SO4 , and remarkable power/energy density (19.98 mW cm(-2) /0.096 mW h cm(-2) in KOH and 35.01 mW cm(-2) /0.244 mW h cm(-2) in H2 SO4 ). Additionally, it shows stable behavior in both bent and flat states. These results promote new opportunities for N,P-CNFs/GN/BC paper electrodes as high areal performance, freestanding electrodes for flexible supercapacitors.

  8. Nanoscale ablation through optically trapped microspheres

    NASA Astrophysics Data System (ADS)

    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. Areal rainfall estimation using moving cars as rain gauges - laboratory and field experiment

    NASA Astrophysics Data System (ADS)

    Rabiei, Ehsan; Haberlandt, Uwe; Sester, Monika; Fitzner, Daniel

    2014-05-01

    Areal precipitation estimation for fine temporal and spatial resolution is still a challenging task. Beside the fact that newly developed instrumentations, e.g. weather radar, provide valuable information with high spatial and temporal resolutions, they are subject to different sources of errors. On the other hand, recording rain gauges provide accurate point rainfall depth, but are still often poor in density. Equipping a car with a GPS device as well as sensors measuring rainfall makes it possible to implement cars on the streets as the moving rain gauges. Initial results from a modeling study assuming arbitrary measurement errors have shown that implementing a reasonable large number of inaccurate measurement devices (raincars) provide more reliable areal precipitations compared to the available rain gauge network. The purpose of this study is to derive relationships between sensor readings and rain rate in a laboratory and quantify the errors. Sensor readings involve wiper frequency and optical sensors which are on the cars to automate wiper activities. Besides, the influence of car speed on the sensor readings is investigated implementing a car-speed simulator. It has been observed that the manual wiper activity adjustment, according to front visibility, shows a strong relationship between rainfall intensity and wiper speed. Two optical sensors calibrated in laboratory showed a relatively strong relationship with the rain intensity recorded by a tipping bucket. A positive relationship between the velocity and the amount of water has been observed meaning that the higher the speed of a car, the higher the amount of water hitting the car. Additionally, some preliminary results of the field experiments are discussed.

  10. Nonequilibrium Ablation of Phenolic Impregnated Carbon Ablator

    NASA Technical Reports Server (NTRS)

    Milos, Frank S.; Chen, Yih K.; Gokcen, Tahir

    2012-01-01

    In previous work, an equilibrium ablation and thermal response model for Phenolic Impregnated Carbon Ablator was developed. In general, over a wide range of test conditions, model predictions compared well with arcjet data for surface recession, surface temperature, in-depth temperature at multiple thermocouples, and char depth. In this work, additional arcjet tests were conducted at stagnation conditions down to 40 W/sq cm and 1.6 kPa. The new data suggest that nonequilibrium effects become important for ablation predictions at heat flux or pressure below about 80 W/sq cm or 10 kPa, respectively. Modifications to the ablation model to account for nonequilibrium effects are investigated. Predictions of the equilibrium and nonequilibrium models are compared with the arcjet data.

  11. Hybrid Areal Interpolation of Census Counts from 2000 Blocks to 2010 Geographies.

    PubMed

    Schroeder, Jonathan P

    2017-03-01

    To measure population changes in areas where census unit boundaries do not align across time, a common approach is to interpolate data from one census's units to another's. This article presents a broad assessment of areal interpolation models for estimating counts of 2000 characteristics in 2010 census units throughout the United States. We interpolate from 2000 census block data using 4 types of ancillary data to guide interpolation: 2010 block densities, imperviousness data, road buffers, and water body polygons. We test 8 binary dasymetric (BD) models and 8 target-density weighting (TDW) models, each using a unique combination of the 4 ancillary data types, and derive 2 hybrid models that blend the best-performing BD and TDW models. The most accurate model is a hybrid that generally gives high weight to TDW (allocating 2000 data in proportion to 2010 densities) but gives increasing weight to a BD model (allocating data uniformly within developed land near roads) in proportion to the estimated 2000-2010 rate of change within each block. Although for most 2010 census units, this hybrid model's estimates differ little from the simplest model's estimates, there are still many areas where the estimates differ considerably. Estimates from the final model, along with lower and upper bounds for each estimate, are publicly available for over 1,000 population and housing characteristics at 10 geographic levels via the National Historical Geographic Information System (NHGIS - http://nhgis.org).

  12. Ablation of carbide materials with femtosecond pulses

    NASA Astrophysics Data System (ADS)

    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.

  13. Pulmonary ablation: a primer.

    PubMed

    Roberton, Benjamin J; Liu, David; Power, Mark; Wan, John M C; Stuart, Sam; Klass, Darren; Yee, John

    2014-05-01

    Percutaneous image-guided thermal ablation is safe and efficacious in achieving local control and improving outcome in the treatment of both early stage non-small-cell lung cancer and pulmonary metastatic disease, in which surgical treatment is precluded by comorbidity, poor cardiorespiratory reserve, or unfavorable disease distribution. Radiofrequency ablation is the most established technology, but new thermal ablation technologies such as microwave ablation and cryoablation may offer some advantages. The use of advanced techniques, such as induced pneumothorax and the popsicle stick technique, or combining thermal ablation with radiotherapy, widens the treatment options available to the multidisciplinary team. The intent of this article is to provide the reader with a practical knowledge base of pulmonary ablation by concentrating on indications, techniques, and follow-up.

  14. Renal Ablation Update

    PubMed Central

    Khiatani, Vishal; Dixon, Robert G.

    2014-01-01

    Thermal ablative technologies have evolved considerably in the recent past and are now an important component of current clinical guidelines for the treatment of small renal masses. Both radiofrequency ablation and cryoablation have intermediate-term oncologic control that rivals surgical options, with favorable complication profiles. Studies comparing cryoablation and radiofrequency ablation show no significant difference in oncologic control or complication profile between the two modalities. Early data from small series with microwave ablation have shown similar promising results. Newer technologies including irreversible electroporation and high-intensity–focused ultrasound have theoretical advantages, but will require further research before becoming a routine part of the ablation armamentarium. The purpose of this review article is to discuss the current ablative technologies available, briefly review their mechanisms of action, discuss technical aspects of each, and provide current data supporting their use. PMID:25049445

  15. Time and space resolved measurement of the electron temperature, mass density and ionization state in the ablation plasma between two exploding Al wiresa)

    NASA Astrophysics Data System (ADS)

    Knapp, P. F.; Pikuz, S. A.; Shelkovenko, T. A.; Hammer, D. A.; Hansen, S. B.

    2012-05-01

    We have determined the properties of plasma around and between two exploding wires using high-resolution x-ray absorption spectroscopy. Plasma densities and temperatures ranging from ≳0.1g/cm3 and a few eV to less than 0.01 g/cm3 and 30 eV have been measured in experiments at Cornell University with two 40 μm aluminum (Al) wires spaced 1 mm apart driven by ˜150 kA peak current pulses with 100 ns rise time. The wire plasma was backlit by the 1.4-1.6 keV continuum radiation produced by a Mo wire X-pinch. The spectrometer employed two spherically bent quartz crystals to record the absorption and backlighter spectra simultaneously. The transition between the dense Al wire core and the coronal plasma is seen as a transition from cold K-edge absorption to Mg-, Na-, and finally Ne-like absorption at the boundary. In the plasma that accumulates between the wires, ionization states up to C-Like Al are observed. The spectrometer geometry and ˜2μm X-pinch source size provide 0.3 eV spectral resolution and 20 μm spatial resolution enabling us to see 1s → 2p satellite transitions as separate lines as well as O-, F-, and Ne-like 1s → 3p transitions that have not been seen before. A step wedge was used to calibrate the transmission, enabling density to be measured within a factor of two and temperature to be measured within ±25%. A genetic algorithm was developed to fit synthetic spectra calculated using the collisional-radiative code SCRAM to the experimental spectra. In order to obtain agreement it was necessary to assume multiple plasma regions with variable thicknesses, thereby allowing the inferred plasma conditions to vary along the absorption path.

  16. Radiofrequency Ablation of Cancer

    SciTech Connect

    Friedman, Marc; Mikityansky, Igor; Kam, Anthony; Libutti, Steven K.; Walther, McClellan M.; Neeman, Ziv; Locklin, Julia K.; Wood, Bradford J.

    2004-09-15

    Radiofrequency ablation (RFA) has been used for over 18 years for treatment of nerve-related chronic pain and cardiac arrhythmias. In the last 10 years, technical developments have increased ablation volumes in a controllable, versatile, and relatively inexpensive manner. The host of clinical applications for RFA have similarly expanded. Current RFA equipment, techniques, applications, results, complications, and research avenues for local tumor ablation are summarized.

  17. Calculating areal average thickness of rigid gas-permeable contact lenses.

    PubMed

    Weissman, B A

    1986-11-01

    A method to calculate areal average thickness of rigid contact lenses is shown. The method involves division of lens volume, which is determined from lens design specifications or derived from measured lens weight, by the area of the lens back surface. Areal average thickness may then be used with known oxygen permeability to generate oxygen transmissibility values.

  18. AREAL low energy electron beam applications in life and materials sciences

    NASA Astrophysics Data System (ADS)

    Tsakanov, V. M.; Aroutiounian, R. M.; Amatuni, G. A.; Aloyan, L. R.; Aslanyan, L. G.; Avagyan, V. Sh.; Babayan, N. S.; Buniatyan, V. V.; Dalyan, Y. B.; Davtyan, H. D.; Derdzyan, M. V.; Grigoryan, B. A.; Grigoryan, N. E.; Hakobyan, L. S.; Haroutyunian, S. G.; Harutiunyan, V. V.; Hovhannesyan, K. L.; Khachatryan, V. G.; Martirosyan, N. W.; Melikyan, G. S.; Petrosyan, A. G.; Petrosyan, V. H.; Sahakyan, A. A.; Sahakyan, V. V.; Sargsyan, A. A.; Simonyan, A. S.; Tatikyan, S. Sh.; Tsakanova, G. V.; Tsovyan, E.; Vardanyan, A. S.; Vardanyan, V. V.; Yeremyan, A. S.; Yeritsyan, H. N.; Zanyan, G. S.

    2016-09-01

    The AREAL laser-driven RF gun provides 2-5 MeV energy ultrashort electron pulses for experimental study in life and materials sciences. We report the first experimental results of the AREAL beam application in the study of molecular-genetic effects, silicon-dielectric structures, ferroelectric nanofilms, and single crystals for scintillators.

  19. Lung Ablation: Whats New?

    PubMed

    Xiong, Lillian; Dupuy, Damian E

    2016-07-01

    Lung cancer had an estimated incidence of 221,200 in 2015, making up 13% of all cancer diagnoses. Tumor ablation is an important treatment option for nonsurgical lung cancer and pulmonary metastatic patients. Radiofrequency ablation has been used for over a decade with newer modalities, microwave ablation, cryoablation, and irreversible electroporation presenting as additional and possibly improved treatment options for patients. This minimally invasive therapy is best for small primary lesions or favorably located metastatic tumors. These technologies can offer palliation and sometimes cure of thoracic malignancies. This article discusses the current available technologies and techniques available for tumor ablation.

  20. Time and space resolved measurement of the electron temperature, mass density and ionization state in the ablation plasma between two exploding Al wires

    SciTech Connect

    Knapp, P. F.; Pikuz, S. A.; Shelkovenko, T. A.; Hammer, D. A.; Hansen, S. B.

    2012-05-15

    We have determined the properties of plasma around and between two exploding wires using high-resolution x-ray absorption spectroscopy. Plasma densities and temperatures ranging from Greater-Than-Or-Equivalent-To 0.1g/cm{sup 3} and a few eV to less than 0.01 g/cm{sup 3} and 30 eV have been measured in experiments at Cornell University with two 40 {mu}m aluminum (Al) wires spaced 1 mm apart driven by {approx}150 kA peak current pulses with 100 ns rise time. The wire plasma was backlit by the 1.4-1.6 keV continuum radiation produced by a Mo wire X-pinch. The spectrometer employed two spherically bent quartz crystals to record the absorption and backlighter spectra simultaneously. The transition between the dense Al wire core and the coronal plasma is seen as a transition from cold K-edge absorption to Mg-, Na-, and finally Ne-like absorption at the boundary. In the plasma that accumulates between the wires, ionization states up to C-Like Al are observed. The spectrometer geometry and {approx}2{mu}m X-pinch source size provide 0.3 eV spectral resolution and 20 {mu}m spatial resolution enabling us to see 1s{yields} 2p satellite transitions as separate lines as well as O-, F-, and Ne-like 1s{yields} 3p transitions that have not been seen before. A step wedge was used to calibrate the transmission, enabling density to be measured within a factor of two and temperature to be measured within {+-}25%. A genetic algorithm was developed to fit synthetic spectra calculated using the collisional-radiative code SCRAM to the experimental spectra. In order to obtain agreement it was necessary to assume multiple plasma regions with variable thicknesses, thereby allowing the inferred plasma conditions to vary along the absorption path.

  1. Areal Feature Matching Based on Similarity Using Critic Method

    NASA Astrophysics Data System (ADS)

    Kim, J.; Yu, K.

    2015-10-01

    In this paper, we propose an areal feature matching method that can be applied for many-to-many matching, which involves matching a simple entity with an aggregate of several polygons or two aggregates of several polygons with fewer user intervention. To this end, an affine transformation is applied to two datasets by using polygon pairs for which the building name is the same. Then, two datasets are overlaid with intersected polygon pairs that are selected as candidate matching pairs. If many polygons intersect at this time, we calculate the inclusion function between such polygons. When the value is more than 0.4, many of the polygons are aggregated as single polygons by using a convex hull. Finally, the shape similarity is calculated between the candidate pairs according to the linear sum of the weights computed in CRITIC method and the position similarity, shape ratio similarity, and overlap similarity. The candidate pairs for which the value of the shape similarity is more than 0.7 are determined as matching pairs. We applied the method to two geospatial datasets: the digital topographic map and the KAIS map in South Korea. As a result, the visual evaluation showed two polygons that had been well detected by using the proposed method. The statistical evaluation indicates that the proposed method is accurate when using our test dataset with a high F-measure of 0.91.

  2. Assessment of probabilistic areal reduction factors of precipitations for the entire French territory with gridded rainfall data.

    NASA Astrophysics Data System (ADS)

    Fouchier, Catherine; Maire, Alexis; Arnaud, Patrick; Cantet, Philippe; Odry, Jean

    2016-04-01

    The starting point of our study was the availability of maps of rainfall quantiles available for the entire French mainland territory at the spatial resolution of 1 km². These maps display the rainfall amounts estimated for different rainfall durations (from 15 minutes to 72 hours) and different return periods (from 2 years up to 1 000 years). They are provided by a regionalized stochastic hourly point rainfall generator, the SHYREG method which was previously developed by Irstea (Arnaud et al., 2007; Cantet and Arnaud, 2014). Being calibrated independently on numerous raingauges data (with an average density across the country of 1 raingauge per 200 km²), this method suffers from a limitation common to point-process rainfall generators: it can only reproduce point rainfall patterns and has no capacity to generate rainfall fields. It can't hence provide areal rainfall quantiles, the estimation of the latter being however needed for the construction of design rainfall or for the diagnostic of observed events. One means of bridging this gap between our local rainfall quantiles and areal rainfall quantiles is given by the concept of probabilistic areal reduction factors of rainfall (ARF) as defined by Omolayo (1993). This concept enables to estimate areal rainfall of a particular frequency within a certain amount of time from point rainfalls of the same frequency and duration. Assessing such ARF for the whole French territory is of particular interest since it should allow us to compute areal rainfall quantiles, and eventually watershed rainfall quantiles, by using the already available grids of statistical point rainfall of the SHYREG method. Our purpose was then to assess these ARF thanks to long time-series of spatial rainfall data. We have used two sets of rainfall fields: i) hourly rainfall fields from a 10-year reference database of Quantitative Precipitation Estimation (QPE) over France (Tabary et al., 2012), ii) daily rainfall fields resulting from a 53-year

  3. Simple model for ablative stabilization

    NASA Astrophysics Data System (ADS)

    Mikaelian, Karnig O.

    1992-11-01

    We present a simple analytic model for ablative stablization of the Rayleigh-Taylor instability. In this model the effect of ablation is to move the peak of the perturbations to the location of peak pressure. This mechanism enhances the density-gradient stabilization, which is effective at short wavelengths, and it also enhances the stabilization of long-wavelength perturbations due to finite shell thickness. We consider the following density profile: exponential blowoff plasma with a density gradient β, followed by a constant-density shell of thickness δt. For perturbations of arbitrary wave number k, we present an explicit expression for the growth rate γ as a function of k, β, and δt. We find that ``thick'' shells defined by β δt>=1 have γ2>=0 for any k, while ``thin'' shells defined by β δt<1 can have γ2<0 for small k, reflecting stability by proximity to the back side of the shell. We also present lasnex simulations that are in good agreement with our analytic formulas.

  4. Ablative Thermal Protection System Fundamentals

    NASA Technical Reports Server (NTRS)

    Beck, Robin A. S.

    2013-01-01

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

  5. Sprayable lightweight ablative coating

    NASA Technical Reports Server (NTRS)

    Simpson, William G. (Inventor); Sharpe, Max H. (Inventor); Hill, William E. (Inventor)

    1991-01-01

    An improved lightweight, ablative coating is disclosed that may be spray applied and cured without the development of appreciable shrinkage cracks. The ablative mixture consists essentially of phenolic microballoons, hollow glass spheres, glass fibers, ground cork, a flexibilized resin binder, and an activated colloidal clay.

  6. Observations of the Ablative Richtmyer-Meshkov Effect Relevant to Indirect-Drive Inertial Confinement Fusion

    NASA Astrophysics Data System (ADS)

    Loomis, Eric; Braun, Dave; Batha, Steve; Landen, Otto

    2013-10-01

    Recent simulations and experiments have shown that isolated features on the outer surface of Inertial Confinement Fusion (ICF) ignition capsules can profoundly impact capsule performance by leading to material jetting or mixing into the hotspot. Controlling the growth of these artifacts is complicated due to uncertainties in equation of state (EOS) models used in simulation codes. Here we report on measurements pertaining to the growth and decay of isolated defects due to x-ray ablation Richtmyer-Meshkov in CH capsules in order to validate these models. Face-on transmission radiography was used to measure the evolution of Gaussian bump arrays in plastic targets. Au halfraums heated to radiation temperatures near 70 eV using 15 beams in a 7.5 ns pulse from the Omega laser (Laboratory for Laser Energetics, University of Rochester, NY) indirectly drove the samples while simultaneous radiographs from Ta and Y backlighter foils were recorded. Shock speed measurements were also made with Omega's Active Shock Break Out (ASBO) diagnostic in conjunction with the x-ray flux recorded by a soft x-ray power diagnostic (DANTE) were used to determine drive conditions in the target. Measurements of 5 micron tall, 17 micron wide bumps show a decrease in bump areal density between 4.5 and 7.5 ns while 33 micron wide bumps saturate near 3 ns consistent with LEOS 5310 and SESAME 7592 simulations.

  7. Observation of hydrodynamic processes of radiation-ablated plasma in a small hole

    SciTech Connect

    Li, Hang; Kuang, Longyu; Jiang, Shaoen Ding, Yongkun; Song, Tianming; Yang, Jiamin Zhu, Tuo; Lin, Zhiwei; Zheng, Jianhua; Zhang, Haiying; Yu, Ruizhen; Liu, Shenye; Hu, Guangyue; Zhao, Bin; Zheng, Jian

    2015-07-15

    In the hohlraum used in laser indirect-drive inertial confinement fusion experiments, hydrodynamic processes of radiation-ablated high-Z plasma have a great effect on laser injection efficiency, radiation uniformity, and diagnosis of hohlraum radiation field from diagnostic windows (DW). To study plasma filling in the DWs, a laser-irradiated Ti disk was used to generate 2–5 keV narrow energy band X-ray as the intense backlighter source, and laser-produced X-ray in a hohlraum with low-Z foam tamper was used to heat a small hole surrounded by gold wall with 150 μm in diameter and 100 μm deep. The hydrodynamic movement of the gold plasma in the small hole was measured by an X-ray framing camera and the results are analyzed. Quantitative measurement of the plasma areal density distribution and evolution in the small hole can be used to assess the effect of plasma filling on the diagnosis from the DWs.

  8. Monitoring Areal Snow Cover Using NASA Satellite Imagery

    NASA Technical Reports Server (NTRS)

    Harshburger, Brian J.; Blandford, Troy; Moore, Brandon

    2011-01-01

    The objective of this project is to develop products and tools to assist in the hydrologic modeling process, including tools to help prepare inputs for hydrologic models and improved methods for the visualization of streamflow forecasts. In addition, this project will facilitate the use of NASA satellite imagery (primarily snow cover imagery) by other federal and state agencies with operational streamflow forecasting responsibilities. A GIS software toolkit for monitoring areal snow cover extent and producing streamflow forecasts is being developed. This toolkit will be packaged as multiple extensions for ArcGIS 9.x and an opensource GIS software package. The toolkit will provide users with a means for ingesting NASA EOS satellite imagery (snow cover analysis), preparing hydrologic model inputs, and visualizing streamflow forecasts. Primary products include a software tool for predicting the presence of snow under clouds in satellite images; a software tool for producing gridded temperature and precipitation forecasts; and a suite of tools for visualizing hydrologic model forecasting results. The toolkit will be an expert system designed for operational users that need to generate accurate streamflow forecasts in a timely manner. The Remote Sensing of Snow Cover Toolbar will ingest snow cover imagery from multiple sources, including the MODIS Operational Snowcover Data and convert them to gridded datasets that can be readily used. Statistical techniques will then be applied to the gridded snow cover data to predict the presence of snow under cloud cover. The toolbar has the ability to ingest both binary and fractional snow cover data. Binary mapping techniques use a set of thresholds to determine whether a pixel contains snow or no snow. Fractional mapping techniques provide information regarding the percentage of each pixel that is covered with snow. After the imagery has been ingested, physiographic data is attached to each cell in the snow cover image. This data

  9. Dynamic effective connectivity of inter-areal brain circuits.

    PubMed

    Battaglia, Demian; Witt, Annette; Wolf, Fred; Geisel, Theo

    2012-01-01

    Anatomic connections between brain areas affect information flow between neuronal circuits and the synchronization of neuronal activity. However, such structural connectivity does not coincide with effective connectivity (or, more precisely, causal connectivity), related to the elusive question "Which areas cause the present activity of which others?". Effective connectivity is directed and depends flexibly on contexts and tasks. Here we show that dynamic effective connectivity can emerge from transitions in the collective organization of coherent neural activity. Integrating simulation and semi-analytic approaches, we study mesoscale network motifs of interacting cortical areas, modeled as large random networks of spiking neurons or as simple rate units. Through a causal analysis of time-series of model neural activity, we show that different dynamical states generated by a same structural connectivity motif correspond to distinct effective connectivity motifs. Such effective motifs can display a dominant directionality, due to spontaneous symmetry breaking and effective entrainment between local brain rhythms, although all connections in the considered structural motifs are reciprocal. We show then that transitions between effective connectivity configurations (like, for instance, reversal in the direction of inter-areal interactions) can be triggered reliably by brief perturbation inputs, properly timed with respect to an ongoing local oscillation, without the need for plastic synaptic changes. Finally, we analyze how the information encoded in spiking patterns of a local neuronal population is propagated across a fixed structural connectivity motif, demonstrating that changes in the active effective connectivity regulate both the efficiency and the directionality of information transfer. Previous studies stressed the role played by coherent oscillations in establishing efficient communication between distant areas. Going beyond these early proposals, we advance

  10. Low temperature ablation models made by pressure/vacuum application

    NASA Technical Reports Server (NTRS)

    Fischer, M. C.; Heier, W. C.

    1970-01-01

    Method developed employs high pressure combined with strong vacuum force to compact ablation models into desired conical shape. Technique eliminates vapor hazard and results in high material density providing excellent structural integrity.

  11. Atmospheric Profile Imprint in Firewall Ablation Coefficient

    NASA Technical Reports Server (NTRS)

    Ceplecha, Z.; Pecina, P.

    1984-01-01

    A general formula which expresses the distance along the meteoric fireball trajectory 1 as a function of t is discussed. Differential equations which include the motion and ablation of a single nonfragmenting meteor body are presented. The importance of the atmospheric density profile in the meteor formula is emphasized.

  12. Use of areal snow cover measurements from ERTS-1 imagery in snowmelt-runoff relationships in Arizona

    NASA Technical Reports Server (NTRS)

    Aul, J. S.; Ffolliott, P. F.

    1975-01-01

    Methods of interpreting ERTS-1 imagery to measure areal snow cover were analyzed. Relationship of areal snow cover and runoff were among the objectives in this study of ERTS-1 imagery use for forecasting snowmelt-runoff relationships.

  13. Ice elevation and areal changes of glaciers from the Northern Patagonia Icefield, Chile

    NASA Astrophysics Data System (ADS)

    Rivera, Andrés; Benham, Toby; Casassa, Gino; Bamber, Jonathan; Dowdeswell, Julian A.

    2007-10-01

    High thinning rates (up to - 4.0 ± 0.97 m a - 1 ) have been measured at Campo de Hielo Patagónico Norte (CHN) or Northern Patagonia Icefield, Chile between 1975 and 2001. Results have been obtained by comparing a Digital Elevation Model (DEM) derived from regular cartography compiled by Instituto Geográfico Militar of Chile (IGM) based upon 1974/1975 aerial photographs and a DEM generated from Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) satellite images acquired in September 2001. A complete cloud-free Landsat ETM+ satellite image mosaic acquired in March 2001 was used to update the available glacier inventory of the CHN, including all glaciers larger than 0.5 km 2 (48 new glaciers). A new delineation of ice divides was also performed over the accumulation areas of glaciers sharing the high plateau where the existing regular cartography exhibits poor coverage of topographic information. This updated glacier inventory produced a total ice area for 2001 of 3953 km 2, which represents a decrease of 3.4 ± 1.5% (140 ± 61 km 2 of ice) with respect to the total ice area of the CHN in 1979 calculated from a Landsat MSS satellite image. Almost 62% of the total area change between 1979 and 2001 took place in glaciers located at the western margin of the CHN, where the maximum area loss was experienced by Glaciar San Quintín with 33 km 2. At the southern margin, Glaciar Steffen underwent the largest ice-area loss (12 km 2 or 2.6% of the 1979 area), whilst at the eastern margin the greatest area loss took place in Glaciares Nef (7.9 km 2, 5.7% of the 1979 area) and Colonia (9.1 km 2, 2.7% of the 1979 area). At the northern margin of the CHN the lower debris-covered ablation area of Glaciar Grosse collapsed into a new freshwater lake formed during the late 1990s. The areal changes measured at the CHN are much larger than previously estimated due to the inclusion of changes experienced in the accumulation areas. The CHN as a whole is

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

    NASA Astrophysics Data System (ADS)

    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.

  15. Tumor Ablation and Nanotechnology

    PubMed Central

    Manthe, Rachel L.; Foy, Susan P.; Krishnamurthy, Nishanth; Sharma, Blanka; Labhasetwar, Vinod

    2010-01-01

    Next to surgical resection, tumor ablation is a commonly used intervention in the treatment of solid tumors. Tumor ablation methods include thermal therapies, photodynamic therapy, and reactive oxygen species (ROS) producing agents. Thermal therapies induce tumor cell death via thermal energy and include radiofrequency, microwave, high intensity focused ultrasound, and cryoablation. Photodynamic therapy and ROS producing agents cause increased oxidative stress in tumor cells leading to apoptosis. While these therapies are safe and viable alternatives when resection of malignancies is not feasible, they do have associated limitations that prevent their widespread use in clinical applications. To improve the efficacy of these treatments, nanoparticles are being studied in combination with nonsurgical ablation regimens. In addition to better thermal effect on tumor ablation, nanoparticles can deliver anticancer therapeutics that show synergistic anti-tumor effect in the presence of heat and can also be imaged to achieve precision in therapy. Understanding the molecular mechanism of nanoparticle-mediated tumor ablation could further help engineer nanoparticles of appropriate composition and properties to synergize the ablation effect. This review aims to explore the various types of nonsurgical tumor ablation methods currently used in cancer treatment and potential improvements by nanotechnology applications. PMID:20866097

  16. Effects of Laser Wavelength on Ablator Testing

    NASA Technical Reports Server (NTRS)

    White, Susan M.

    2014-01-01

    Wavelength-dependent or spectral radiation effects are potentially significant for thermal protection materials. NASA atmospheric entry simulations include trajectories with significant levels of shock layer radiation which is concentrated in narrow spectral lines. Tests using two different high powered lasers, the 10.6 micron LHMEL I CO2 laser and the near-infrared 1.07 micron fiber laser, on low density ablative thermal protection materials offer a unique opportunity to evaluate spectral effects. Test results indicated that the laser wavelength can impact the thermal response of an ablative material, in terms of bond-line temperatures, penetration times, mass losses, and char layer thicknesses.

  17. Measurement of inflight shell areal density perturbations in NIF capsule implosions near peak velocity

    NASA Astrophysics Data System (ADS)

    Hammel, B. A.; Pickworth, L.; Smalyuk, V.; Macphee, A.; Scott, H. A.; Robey, H.; Barrios, M.; Regan, S. P.

    2015-11-01

    Quantitative measurements of shell-RhoR perturbations in capsules near peak implosion velocity (PV) are challenging. An external backlighter samples both sides of the shell, unless a re-entrant cone is used (potentially perturbing implosion). Emission from the hot core, after shock-stagnation and prior to PV, has been used as a self-backlighter, providing a means to sample one side of the capsule. Adding high-Z gas (~ 1% Ar) to the capsule fill in Symcaps (4He), has produced a continuum backlighter with significant increase in emission at photon energies ~ 8 keV over nominal fills. From images of the transmitted self-emission, above and below the K-edge of an internally doped Cu layer, we infer the growth at PV of imposed perturbations (100 nm amplitude, mode 40). Prepared by LLNL under Contract DE-AC52-07NA27344.

  18. HoneySiC: a new optomechanical material for low-areal cost and density

    NASA Astrophysics Data System (ADS)

    Goodman, William A.

    2013-09-01

    One of the major problems perceived for deposited silicon carbide mirrors and structures is the cost associated with machining and lightweighting the material to the specifications of a drawing. Molded pedigrees of silicon carbide address these concerns by casting or molding a slurry and prefiring the slurry to make a consolidated and porous greenbody which is relatively soft and not very difficult to machine. The machined greenbody is then infiltrated with molten silicon in an exothermic process that yields a two phase reaction bonded silicon carbide material that must undergo a final machining step. Converted silicon carbide pedigrees machine a graphite or carbon/carbon precursor material to near net shape and then infiltrate the part with gaseous silicon monoxide or molten silicon to convert most or all of the carbon to silicon carbide. Some pedigrees are highly porous, while others may be dense and containing 2 or 3 different phases of material. We have created and demonstrated a new fiber reinforced silicon carbide material that combines the benefits of molding, infiltration and conversion processes. The resulting HoneySiC material requires a minimal amount of machining. HoneySiC material achieves lightweighting of 92% relative to bulk material and net production cost on the order of 38K per square meter (unpolished), less than half of NASA's goal of 100K per square meter.

  19. Measurements of Areal Densities and Temperatures from DT Capsule Implosions on OMEGA

    NASA Astrophysics Data System (ADS)

    Li, C. K.; Hicks, D. G.; Seguin, F. H.; Frenje, J. A.; Green, K. M.; Petrasso, R. D.; Soures, J. M.; Meyerhofer, D. D.; Glebov, V. Yu.; Stoeckl, C.; Roberts, S.; Sangster, T. C.; Phillips, T. W.

    2000-10-01

    Spectral measurements were made of 14.1-MeV neutron knock-on particles from imploded DT-filled CH shells on OMEGA. Fuel ρR is inferred from the spectra and yields of D and T knock-ons, while shell ρR is determined from the measured yield of p knock-ons from the CH. Shell electron temperature Te is uniquely determined by using the downshift of the endpoint energies of knock-ons from the fuel. This is possible because knock-on yield is independent of Te while the energy downshift is a function of both shell ρR and shell T_e. In addition, CD and CH shells were also shot. From such implosions, a complex set of multiple particle spectra are obtained simultaneously. This work was performed in part at the LLE NLUF, and was supported in part by the U.S. DOE Contr. DE-FG03-99SF21782, LLE subcont. PO410025G, LLNL subcont. B313975, and by the U.S. DOE Office of ICF under Coop. Agree. No. DE-FC03-92SF19460.

  20. Preparing two-dimensional microporous carbon from Pistachio nutshell with high areal capacitance as supercapacitor materials

    NASA Astrophysics Data System (ADS)

    Xu, Jiandong; Gao, Qiuming; Zhang, Yunlu; Tan, Yanli; Tian, Weiqian; Zhu, Lihua; Jiang, Lei

    2014-07-01

    Two-dimensional (2D) porous carbon AC-SPN-3 possessing of amazing high micropore volume ratio of 83% and large surface area of about 1069 m2 g-1 is high-yield obtained by pyrolysis of natural waste Pistachio nutshells with KOH activation. The AC-SPN-3 has a curved 2D lamellar morphology with the thickness of each slice about 200 nm. The porous carbon is consists of highly interconnected uniform pores with the median pore diameter of about 0.76 nm, which could potentially improve the performance by maximizing the electrode surface area accessible to the typical electrolyte ions (such as TEA+, diameter = ~0.68 nm). Electrochemical analyses show that AC-SPN-3 has significantly large areal capacitance of 29.3/20.1 μF cm-2 and high energy density of 10/39 Wh kg-1 at power of 52/286 kW kg-1 in 6 M KOH aqueous electrolyte and 1 M TEABF4 in EC-DEC (1:1) organic electrolyte system, respectively.

  1. Flexible supercapacitors with high areal capacitance based on hierarchical carbon tubular nanostructures

    NASA Astrophysics Data System (ADS)

    Zhang, Haitao; Su, Hai; Zhang, Lei; Zhang, Binbin; Chun, Fengjun; Chu, Xiang; He, Weidong; Yang, Weiqing

    2016-11-01

    Hierarchical structure design can greatly enhance the unique properties of primary material(s) but suffers from complicated preparation process and difficult self-assembly of materials with different dimensionalities. Here we report on the growth of single carbon tubular nanostructures with hierarchical structure (hCTNs) through a simple method based on direct conversion of carbon dioxide. Resorting to in-situ transformation and self-assembly of carbon micro/nano-structures, the obtained hCTNs are blood-like multichannel hierarchy composed of one large channel across the hCTNs and plenty of small branches connected to each other. Due to the unique pore structure and high surface area, these hCTN-based flexible supercapacitors possess the highest areal capacitance of ∼320 mF cm-2, as well as good rate-capability and excellent cycling stability (95% retention after 2500 cycles). It was established that this method can control the morphology, size, and density of hCTNs and effectively construct hCTNs well anchored to the various substrates. Our work unambiguously demonstrated the potential of hCTNs for large flexible supercapacitors and integrated energy management electronics.

  2. Preparing two-dimensional microporous carbon from Pistachio nutshell with high areal capacitance as supercapacitor materials

    PubMed Central

    Xu, Jiandong; Gao, Qiuming; Zhang, Yunlu; Tan, Yanli; Tian, Weiqian; Zhu, Lihua; Jiang, Lei

    2014-01-01

    Two-dimensional (2D) porous carbon AC-SPN-3 possessing of amazing high micropore volume ratio of 83% and large surface area of about 1069 m2 g−1 is high-yield obtained by pyrolysis of natural waste Pistachio nutshells with KOH activation. The AC-SPN-3 has a curved 2D lamellar morphology with the thickness of each slice about 200 nm. The porous carbon is consists of highly interconnected uniform pores with the median pore diameter of about 0.76 nm, which could potentially improve the performance by maximizing the electrode surface area accessible to the typical electrolyte ions (such as TEA+, diameter = ~0.68 nm). Electrochemical analyses show that AC-SPN-3 has significantly large areal capacitance of 29.3/20.1 μF cm−2 and high energy density of 10/39 Wh kg−1 at power of 52/286 kW kg−1 in 6 M KOH aqueous electrolyte and 1 M TEABF4 in EC-DEC (1:1) organic electrolyte system, respectively. PMID:24986670

  3. Thermal ablation for hepatocellular carcinoma.

    PubMed

    Head, Hayden W; Dodd, Gerald D

    2004-11-01

    Thermal ablation, as a form of minimally invasive therapy for hepatocellular carcinoma (HCC), has become an important treatment modality. Because of the limitations of surgery, the techniques of thermal ablation have become standard therapies for HCC in some situations. This article reviews 4 thermal ablation techniques-radiofrequency (RF) ablation, microwave ablation, laser ablation, and cryoablation. Each of these techniques may have a role in treating HCC, and the mechanisms, equipment, patient selection, results, and complications of each are considered. Furthermore, combined therapies consisting of thermal ablation and adjuvant chemotherapy also show promise for enhancing these techniques. Important areas of research into thermal ablation remain, including improving the ability of ablation to treat larger tumors, determining the indications for each thermal ablation modality, optimizing image guidance, and obtaining good outcome data on the efficacy of these techniques.

  4. Ablative skin resurfacing.

    PubMed

    Agrawal, Nidhi; Smith, Greg; Heffelfinger, Ryan

    2014-02-01

    Ablative laser resurfacing has evolved as a safe and effective treatment for skin rejuvenation. Although traditional lasers were associated with significant thermal damage and lengthy recovery, advances in laser technology have improved safety profiles and reduced social downtime. CO2 lasers remain the gold standard of treatment, and fractional ablative devices capable of achieving remarkable clinical improvement with fewer side effects and shorter recovery times have made it a more practical option for patients. Although ablative resurfacing has become safer, careful patient selection and choice of suitable laser parameters are essential to minimize complications and optimize outcomes. This article describes the current modalities used in ablative laser skin resurfacing and examines their efficacy, indications, and possible side effects.

  5. Endometrial Ablation for Menorrhagia

    PubMed Central

    Sanders, Barry H.

    1992-01-01

    Endometrial ablation is a relatively new treatment for patients with persistent menorrhagia. The procedure can be performed by either laser photocoagulation or electrocoagulation; both have a very low risk of complication. Generally, less than 24 hours of hospitalization is required and return to normal activities, including work, is almost immediate. Endometrial ablation is likely to become a mainstay of treatment for menorrhagia as the technology and training become more readily available. PMID:21229128

  6. Template synthesis of SnO2/α-Fe2O3 nanotube array for 3D lithium ion battery anode with large areal capacity.

    PubMed

    Zeng, Weiqian; Zheng, Feipeng; Li, Ruizhi; Zhan, Yang; Li, Yuanyuan; Liu, Jinping

    2012-04-21

    Electrodes with three-dimensional (3D) nanostructure are expected to improve the energy and power densities per footprint area of lithium ion microbatteries. Herein, we report a large-scale synthesis of a SnO(2)/α-Fe(2)O(3) composite nanotube array on a stainless steel substrate via a ZnO nanowire array as an in situ sacrificial template without using any strong acid or alkali. Importantly, both SnO(2) and α-Fe(2)O(3) contribute to the lithium storage, and the hybridization of SnO(2) and α-Fe(2)O(3) into an integrated nanotube structure provides them with an elegant synergistic effect when participating in electrochemical reactions. Large areal capacities and good rate capability are demonstrated for such a composite nanotube array. Particularly noteworthy is that the areal capacities (e.g. 1.289 mAh cm(-2) at a current rate of 0.1 mA cm(-2)) are much larger than those of many previous thin-film/3D microbattery electrodes. Our work suggests the possibility of further improving the areal capacity/energy density of 3D microelectrodes by designing ordered hybrid nanostructure arrays.

  7. High areal capacity Si/LiCoO2 batteries from electrospun composite fiber mats

    DOE PAGES

    Self, Ethan C.; Naguib, Michael Abdelmalak; Ruther, Rose E.; ...

    2017-03-09

    Freestanding nanofiber mat Li–ion battery anodes containing Si nanoparticles, carbon black, and poly(acrylic acid) (Si/C/PAA) are prepared using electrospinning. The mats are compacted to a high fiber volume fraction (≈0.85), and interfiber contacts are welded by exposing the mat to methanol vapor. A compacted+welded fiber mat anode containing 40 wt % Si exhibits high capacities of 1484 mA h g–1 (3500 mA h gmath formula ) at 0.1 C and 489 mA h g–1 at 1 C and good cycling stability (e.g., 73 % capacity retention over 50 cycles). Post-mortem analysis of the fiber mats shows that the overall electrodemore » structure is preserved during cycling. Whereas many nanostructured Si anodes are hindered by their low active material loadings and densities, thick, densely packed Si/C/PAA fiber mat anodes reported here have high areal and volumetric capacities (e.g., 4.5 mA h cm–2 and 750 mA h cm–3, respectively). A full cell containing an electrospun Si/C/PAA anode and electrospun LiCoO2-based cathode has a high specific energy density of 270 Wh kg–1. Here, the excellent performance of the electrospun Si/C/PAA fiber mat anodes is attributed to the: i) PAA binder, which interacts with the SiOx surface of Si nanoparticles and ii) high material loading, high fiber volume fraction, and welded interfiber contacts of the electrospun mats.« less

  8. High Areal Capacity Si/LiCoO2 Batteries from Electrospun Composite Fiber Mats.

    PubMed

    Self, Ethan C; Naguib, Michael; Ruther, Rose E; McRen, Emily C; Wycisk, Ryszard; Liu, Gao; Nanda, Jagjit; Pintauro, Peter N

    2017-03-09

    Freestanding nanofiber mat Li-ion battery anodes containing Si nanoparticles, carbon black, and poly(acrylic acid) (Si/C/PAA) are prepared using electrospinning. The mats are compacted to a high fiber volume fraction (≈0.85), and interfiber contacts are welded by exposing the mat to methanol vapor. A compacted+welded fiber mat anode containing 40 wt % Si exhibits high capacities of 1484 mA h g(-1) (3500 mA h g-1Si ) at 0.1 C and 489 mA h g(-1) at 1 C and good cycling stability (e.g., 73 % capacity retention over 50 cycles). Post-mortem analysis of the fiber mats shows that the overall electrode structure is preserved during cycling. Whereas many nanostructured Si anodes are hindered by their low active material loadings and densities, thick, densely packed Si/C/PAA fiber mat anodes reported here have high areal and volumetric capacities (e.g., 4.5 mA h cm(-2) and 750 mA h cm(-3) , respectively). A full cell containing an electrospun Si/C/PAA anode and electrospun LiCoO2 -based cathode has a high specific energy density of 270 Wh kg(-1) . The excellent performance of the electrospun Si/C/PAA fiber mat anodes is attributed to the: i) PAA binder, which interacts with the SiOx surface of Si nanoparticles and ii) high material loading, high fiber volume fraction, and welded interfiber contacts of the electrospun mats.

  9. Laser ablation with applied magnetic field for electric propulsion

    NASA Astrophysics Data System (ADS)

    Batishcheva, Alla; Batishchev, Oleg; Cambier, Jean-Luc

    2012-10-01

    Using ultrafast lasers with tera-watt-level power allows efficient ablation and ionization of solid-density materials [1], creating dense and hot (˜100eV) plasma. We propose ablating small droplets in the magnetic nozzle configurations similar to mini-helicon plasma source [2]. Such approach may improve the momentum coupling compared to ablation of solid surfaces and facilitate plasma detachment. Results of 2D modeling of solid wire ablation in the applied magnetic field are presented and discussed. [4pt] [1] O. Batishchev et al, Ultrafast Laser Ablation for Space Propulsion, AIAA technical paper 2008-5294, -16p, 44th JPC, Hartford, 2008.[0pt] [2] O. Batishchev and J.L. Cambier, Experimental Study of the Mini-Helicon Thruster, Air Force Research Laboratory Report, AFRL-RZ-ED-TR-2009-0020, 2009.

  10. Testing of Advanced Conformal Ablative TPS

    NASA Technical Reports Server (NTRS)

    Gasch, Matthew; Agrawal, Parul; Beck, Robin

    2013-01-01

    In support of the CA250 project, this paper details the results of a test campaign that was conducted at the Ames Arcjet Facility, wherein several novel low density thermal protection (TPS) materials were evaluated in an entry like environment. The motivation for these tests was to investigate whether novel conformal ablative TPS materials can perform under high heat flux and shear environment as a viable alternative to rigid ablators like PICA or Avcoat for missions like MSL and beyond. A conformable TPS over a rigid aeroshell has the potential to solve a number of challenges faced by traditional rigid TPS materials (such as tiled Phenolic Impregnated Carbon Ablator (PICA) system on MSL, and honeycomb-based Avcoat on the Orion Multi Purpose Crew Vehicle (MPCV)). The compliant (high strain to failure) nature of the conformable ablative materials will allow better integration of the TPS with the underlying aeroshell structure and enable monolithic-like configuration and larger segments to be used in fabrication.A novel SPRITE1 architecture, developed by the researchers at NASA Ames was used for arcjet testing. This small probe like configuration with 450 spherecone, enabled us to test the materials in a combination of high heat flux, pressure and shear environment. The heat flux near the nose were in the range of 500-1000 W/sq cm whereas in the flank section of the test article the magnitudes were about 50 of the nose, 250-500W/sq cm range. There were two candidate conformable materials under consideration for this test series. Both test materials are low density (0.28 g/cu cm) similar to Phenolic Impregnated Carbon Ablator (PICA) or Silicone Impregnated Refractory Ceramic Ablator (SIRCA) and are comprised of: A flexible carbon substrate (Carbon felt) infiltrated with an ablative resin system: phenolic (Conformal-PICA) or silicone (Conformal-SICA). The test demonstrated a successful performance of both the conformable ablators for heat flux conditions between 50

  11. Mechanism study of skin tissue ablation by nanosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Fang, Qiyin

    . A laser-induced and localized thermal ionization pathway has been investigated and it was found to have significant influence on the initial free electron density during plasma formation due to the combination of strong light absorption by chromophores and confined temperature rise in the chromophores. Good agreements have been found between the new plasma-mediated ablation model and experimental results. The implications of this dissertation research to the future improvement of laser systems in dermatology and plastic surgery are discussed.

  12. Infrared laser bone ablation

    SciTech Connect

    Nuss, R.C.; Fabian, R.L.; Sarkar, R.; Puliafito, C.A.

    1988-01-01

    The bone ablation characteristics of five infrared lasers, including three pulsed lasers (Nd:YAG, lambda = 1064 micron; Hol:YSGG, lambda = 2.10 micron; and Erb:YAG, lambda = 2.94 micron) and two continuous-wave lasers (Nd:YAG, lambda = 1.064 micron; and CO/sub 2/, lambda = 10.6 micron), were studied. All laser ablations were performed in vitro, using moist, freshly dissected calvarium of guinea pig skulls. Quantitative etch rates of the three pulsed lasers were calculated. Light microscopy of histologic sections of ablated bone revealed a zone of tissue damage of 10 to 15 micron adjacent to the lesion edge in the case of the pulsed Nd:YAG and the Erb:YAG lasers, from 20 to 90 micron zone of tissue damage for bone ablated by the Hol:YSGG laser, and 60 to 135 micron zone of tissue damage in the case of the two continuous-wave lasers. Possible mechanisms of bone ablation and tissue damage are discussed.

  13. Femtosecond ablation of ultrahard materials

    NASA Astrophysics Data System (ADS)

    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.

  14. Laser ablation dynamics in metals: The thermal regime

    SciTech Connect

    Mezzapesa, F. P.; Brambilla, M.; Dabbicco, M.; Scamarcio, G.; Columbo, L. L.; Ancona, A.; Sibillano, T.

    2012-07-02

    We studied the laser ablation dynamics of steel in the thermal regime both experimentally and theoretically. The real-time monitoring of the process shows that the ablation rate depends on laser energy density and ambient pressure during the exposure time. We demonstrated that the ablation efficiency can be enhanced when the pressure is reduced with respect to the atmospheric pressure for a given laser fluence, reaching an upper limit despite of high-vacuum conditions. An analytical model based on the Hertz-Knudsen law reproduces all the experimental results.

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

    NASA Technical Reports Server (NTRS)

    Lachaud, Jean; Mansour, Nagi N.

    2008-01-01

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

  16. Laser-induced shockwave propagation from ablation in a cavity

    SciTech Connect

    Zeng Xianzhong; Mao Xianglei; Mao, Samuel S.; Wen, S.-B.; Greif, Ralph; Russo, Richard E.

    2006-02-06

    The propagation of laser-induced shockwaves from ablation inside of cavities was determined from time-resolved shadowgraph images. The temperature and electron number density of the laser-induced plasma was determined from spectroscopic measurements. These properties were compared to those for laser ablation on the flat surface under the same energy and background gas condition. A theoretical model was proposed to determine the amount of energy and vaporized mass stored in the vapor plume based on these measurements.

  17. Shuttle subscale ablative nozzle tests

    NASA Technical Reports Server (NTRS)

    Powers, L. B.; Bailey, R. L.

    1980-01-01

    Recent subscale nozzle tests have identified new and promising carbon phenolic nozzle ablatives which utilize staple rayon, PAN, and pitch based carbon cloth. A 4-inch throat diameter submerged test nozzle designed for the 48-inch Jet Propulsion Laboratory char motor was used to evaluate five different designs incorporating 20 candidate ablatives. Test results indicate that several pitch and PAN-based carbon phenolic ablatives can provide erosion and char performance equivalent or superior to the present continuous rayon-based SRM ablative.

  18. Areal rainfall estimation using moving cars - computer experiments including hydrological modeling

    NASA Astrophysics Data System (ADS)

    Rabiei, Ehsan; Haberlandt, Uwe; Sester, Monika; Fitzner, Daniel; Wallner, Markus

    2016-09-01

    The need for high temporal and spatial resolution precipitation data for hydrological analyses has been discussed in several studies. Although rain gauges provide valuable information, a very dense rain gauge network is costly. As a result, several new ideas have emerged to help estimating areal rainfall with higher temporal and spatial resolution. Rabiei et al. (2013) observed that moving cars, called RainCars (RCs), can potentially be a new source of data for measuring rain rate. The optical sensors used in that study are designed for operating the windscreen wipers and showed promising results for rainfall measurement purposes. Their measurement accuracy has been quantified in laboratory experiments. Considering explicitly those errors, the main objective of this study is to investigate the benefit of using RCs for estimating areal rainfall. For that, computer experiments are carried out, where radar rainfall is considered as the reference and the other sources of data, i.e., RCs and rain gauges, are extracted from radar data. Comparing the quality of areal rainfall estimation by RCs with rain gauges and reference data helps to investigate the benefit of the RCs. The value of this additional source of data is not only assessed for areal rainfall estimation performance but also for use in hydrological modeling. Considering measurement errors derived from laboratory experiments, the result shows that the RCs provide useful additional information for areal rainfall estimation as well as for hydrological modeling. Moreover, by testing larger uncertainties for RCs, they observed to be useful up to a certain level for areal rainfall estimation and discharge simulation.

  19. Comprehensive Areal Model of Earthquake-Induced Landslides: Technical Specification and User Guide

    USGS Publications Warehouse

    Miles, Scott B.; Keefer, David K.

    2007-01-01

    This report describes the complete design of a comprehensive areal model of earthquakeinduced landslides (CAMEL). This report presents the design process, technical specification of CAMEL. It also provides a guide to using the CAMEL source code and template ESRI ArcGIS map document file for applying CAMEL, both of which can be obtained by contacting the authors. CAMEL is a regional-scale model of earthquake-induced landslide hazard developed using fuzzy logic systems. CAMEL currently estimates areal landslide concentration (number of landslides per square kilometer) of six aggregated types of earthquake-induced landslides - three types each for rock and soil.

  20. Laboratory Micrometeroid/Dust Ablation Studies

    NASA Astrophysics Data System (ADS)

    Thomas, E.; Horanyi, M.; Janches, D.; Munsat, T. L.; Plane, J. M. C.; Simolka, J.; Sternovsky, Z.

    2014-12-01

    Each day, somewhere between 5-270 tonnes of meteoric material ablates in Earth's upper atmosphere. Thisenormous range is significant because the Interplanetary Dust Particle (IDP) input has implications in ourunderstanding of meteor transport in the atmosphere, the formation of layers of metal atoms and ions,nucleation of noctilucent clouds, effects on stratospheric aerosols and O3 chemistry, and dust evolution inour solar system. As the dust ablates, it produces light, as well as a plasma trail of ionized atmosphericatoms and electrons. These meteor signatures are detected by photographic means, or by radar, but thereremain uncertainties in the luminous efficiency and ionization coefficient of meteors - two parameters thatare essential to evaluate densities, masses, height distributions and fluxes. Precise measurements of theseparameters would allow for not only an understanding of the layers of metal atoms and ions and meteoricsmoke particles in the mesosphere and lower thermosphere, but also would allow for the Earth's atmosphereto be used as a dust detector to detect and characterize the dust environment in our solar system. This work discusses the preliminary results of the new dust ablation facility at the 3 MV hypervelocity dust accelerator at the Institute for Modeling Plasma, Atmospheres and Cosmic Dust (IMPACT) at the University of Colorado, which aims to characterize the ionization coefficient and luminous efficiency of ablating micrometeroids.

  1. Percutaneous ablation of adrenal tumors.

    PubMed

    Venkatesan, Aradhana M; Locklin, Julia; Dupuy, Damian E; Wood, Bradford J

    2010-06-01

    Adrenal tumors comprise a broad spectrum of benign and malignant neoplasms and include functional adrenal adenomas, pheochromocytomas, primary adrenocortical carcinoma, and adrenal metastases. Percutaneous ablative approaches that have been described and used in the treatment of adrenal tumors include percutaneous radiofrequency ablation, cryoablation, microwave ablation, and chemical ablation. Local tumor ablation in the adrenal gland presents unique challenges, secondary to the adrenal gland's unique anatomic and physiological features. The results of clinical series employing percutaneous ablative techniques in the treatment of adrenal tumors are reviewed in this article. Clinical and technical considerations unique to ablation in the adrenal gland are presented, including approaches commonly used in our practices, and risks and potential complications are discussed.

  2. 3D flexible O/N Co-doped graphene foams for supercapacitor electrodes with high volumetric and areal capacitances

    NASA Astrophysics Data System (ADS)

    Qin, Tianfeng; Wan, Zunyuan; Wang, Zilei; Wen, Yuxiang; Liu, Mengting; Peng, Shanglong; He, Deyan; Hou, Juan; Huang, Fei; Cao, Guozhong

    2016-12-01

    3D flexible O/N co-doped graphene foams (GF) have been designed and fabricated successfully via combining the compression/hot curing strategy with chemical reduction and hydrothermal treatment, in which melamine foams were used not only as the source of N/O functional groups for the introduction of pseudocapacitance but also as the sacrificial template to inhibit the agglomeration of graphene. Also, the mechanism for method of the compressing/hot curing has been investigated systematically. And the resultant GF demonstrates excellent mechanical strength and flexibility. When the compacting GF is used as free-standing electrodes for supercapacitor, it exhibits more excellent ability of charge storage than that of pristine graphene foams. And 10 MPa-GF electrodes delivers high areal capacitance of 375 μF cm-2 at a current density of 1 A g-1, excellent rate capabilities and superior cycling stability of above 100%. According to the analysis of capacitance contribution for 10 MPa-GF electrode, the pseudocapacitance originated from N/O functional groups is up to ∼65% of the contribution of total capacitance. Moreover, the symmetric supercapacitor comprised of 10 MPa-GF electrodes presents a maximum energy density of 16 Wh kg-1 (8 Wh L-1) and a maximum power density of 17 kW kg-1 (8.6 kW L-1).

  3. Femtosecond laser for cavity preparation in enamel and dentin: ablation efficiency related factors

    PubMed Central

    Chen, H.; Li, H.; Sun, YC.; Wang, Y.; Lü, PJ.

    2016-01-01

    To study the effects of laser fluence (laser energy density), scanning line spacing and ablation depth on the efficiency of a femtosecond laser for three-dimensional ablation of enamel and dentin. A diode-pumped, thin-disk femtosecond laser (wavelength 1025 nm, pulse width 400 fs) was used for the ablation of enamel and dentin. The laser spot was guided in a series of overlapping parallel lines on enamel and dentin surfaces to form a three-dimensional cavity. The depth and volume of the ablated cavity was then measured under a 3D measurement microscope to determine the ablation efficiency. Different values of fluence, scanning line spacing and ablation depth were used to assess the effects of each variable on ablation efficiency. Ablation efficiencies for enamel and dentin were maximized at different laser fluences and number of scanning lines and decreased with increases in laser fluence or with increases in scanning line spacing beyond spot diameter or with increases in ablation depth. Laser fluence, scanning line spacing and ablation depth all significantly affected femtosecond laser ablation efficiency. Use of a reasonable control for each of these parameters will improve future clinical application. PMID:26864679

  4. Femtosecond laser for cavity preparation in enamel and dentin: ablation efficiency related factors

    NASA Astrophysics Data System (ADS)

    Chen, H.; Li, H.; Sun, Yc.; Wang, Y.; Lü, Pj.

    2016-02-01

    To study the effects of laser fluence (laser energy density), scanning line spacing and ablation depth on the efficiency of a femtosecond laser for three-dimensional ablation of enamel and dentin. A diode-pumped, thin-disk femtosecond laser (wavelength 1025 nm, pulse width 400 fs) was used for the ablation of enamel and dentin. The laser spot was guided in a series of overlapping parallel lines on enamel and dentin surfaces to form a three-dimensional cavity. The depth and volume of the ablated cavity was then measured under a 3D measurement microscope to determine the ablation efficiency. Different values of fluence, scanning line spacing and ablation depth were used to assess the effects of each variable on ablation efficiency. Ablation efficiencies for enamel and dentin were maximized at different laser fluences and number of scanning lines and decreased with increases in laser fluence or with increases in scanning line spacing beyond spot diameter or with increases in ablation depth. Laser fluence, scanning line spacing and ablation depth all significantly affected femtosecond laser ablation efficiency. Use of a reasonable control for each of these parameters will improve future clinical application.

  5. Ablation of skeletal metastases: current status.

    PubMed

    Kurup, A Nicholas; Callstrom, Matthew R

    2010-08-01

    Image-guided percutaneous ablation of bone metastases is an effective, minimally invasive alternative to conventional therapies in the palliation of pain from metastatic disease. Ablative technologies applied in the treatment of skeletal metastases include radiofrequency ablation, cryoablation, microwave ablation, laser ablation, ethanol ablation, and, most recently, focused ultrasound. These ablative methods may be performed in combination with percutaneous cementoplasty to provide support and stabilization for metastases in weight-bearing bones at risk for pathologic fracture.

  6. The intercrater plains of Mercury and the Moon: Their nature, origin and role in terrestrial planet evolution. Areal measurement of Mercury's first quadrant. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Leake, M. A.

    1982-01-01

    Various linear and areal measurements of Mercury's first quadrant which were used in geological map preparation, map analysis, and statistical surveys of crater densities are discussed. Accuracy of each method rests on the determination of the scale of the photograph, i.e., the conversion factor between distances on the planet (in km) and distances on the photograph (in cm). Measurement errors arise due to uncertainty in Mercury's radius, poor resolution, poor coverage, high Sun angle illumination in the limb regions, planetary curvature, limited precision in measuring instruments, and inaccuracies in the printed map scales. Estimates are given for these errors.

  7. Electric field modulation of the non-linear areal magnetic anisotropy energy

    NASA Astrophysics Data System (ADS)

    Lau, Yong-Chang; Sheng, Peng; Mitani, Seiji; Chiba, Daichi; Hayashi, Masamitsu

    2017-01-01

    We study the ferromagnetic layer thickness dependence of the voltage-controlled magnetic anisotropy (VCMA) in gated CoFeB/MgO heterostructures with heavy metal underlayers. When the effective CoFeB thickness is below ˜1 nm, the VCMA efficiency of Ta/CoFeB/MgO heterostructures considerably decreases with decreasing CoFeB thickness. We find that a high order phenomenological term used to describe the thickness dependence of the areal magnetic anisotropy energy can also account for the change in the areal VCMA efficiency. In this structure, the higher order term competes against the common interfacial VCMA, thereby reducing the efficiency at lower CoFeB thickness. The areal VCMA efficiency does not saturate even when the effective CoFeB thickness exceeds ˜1 nm. We consider the higher order term is related to the strain that develops at the CoFeB/MgO interface: as the average strain of the CoFeB layer changes with its thickness, the electronic structure of the CoFeB/MgO interface varies, leading to changes in areal magnetic anisotropy energy and VCMA efficiency.

  8. A hybrid simulation-optimization approach for solving the areal groundwater pollution source identification problems

    NASA Astrophysics Data System (ADS)

    Ayvaz, M. Tamer

    2016-07-01

    In this study, a new simulation-optimization approach is proposed for solving the areal groundwater pollution source identification problems which is an ill-posed inverse problem. In the simulation part of the proposed approach, groundwater flow and pollution transport processes are simulated by modeling the given aquifer system on MODFLOW and MT3DMS models. The developed simulation model is then integrated to a newly proposed hybrid optimization model where a binary genetic algorithm and a generalized reduced gradient method are mutually used. This is a novel approach and it is employed for the first time in the areal pollution source identification problems. The objective of the proposed hybrid optimization approach is to simultaneously identify the spatial distributions and input concentrations of the unknown areal groundwater pollution sources by using the limited number of pollution concentration time series at the monitoring well locations. The applicability of the proposed simulation-optimization approach is evaluated on a hypothetical aquifer model for different pollution source distributions. Furthermore, model performance is evaluated for measurement error conditions, different genetic algorithm parameter combinations, different numbers and locations of the monitoring wells, and different heterogeneous hydraulic conductivity fields. Identified results indicated that the proposed simulation-optimization approach may be an effective way to solve the areal groundwater pollution source identification problems.

  9. CONFRONTING THE MODIFIABLE AREAL UNIT PROBLEM FOR INFERENCE ON NITRATE IN REGIONAL SHALLOW GROUND WATER

    EPA Science Inventory

    The modifiable areal unit problem results from data aggregation to a level which is so arbitrary that critical information is lost. Yet aggregation is necessary for assessment under the U.S. Environmental Protection Agency's Regional Vulnerability Assessment Program. This work pr...

  10. Laser ablation of polymeric materials at 157 nm

    NASA Astrophysics Data System (ADS)

    Costela, A.; García-Moreno, I.; Florido, F.; Figuera, J. M.; Sastre, R.; Hooker, S. M.; Cashmore, J. S.; Webb, C. E.

    1995-03-01

    Results are presented on the ablation by 157 nm laser radiation of polytetrafluoroethylene (PTFE), polyimide, polyhydroxybutyrate (PHB), poly(methyl methacrylate) (PMMA), and poly(2-hydroxyethyl methacrylate) with 1% of ethylene glycol dimethacrylate as a crosslinking monomer. Direct photoetching of PHB and undoped PTFE is demonstrated for laser fluences ranging from 0.05 to 0.8 J/cm2. The dependence of the ablation process on the polymer structure is analyzed, and insight into the ablation mechanism is gained from an analysis of the data using Beer-Lambert's law and the kinetic model of the moving interface. Consideration of the absorbed energy density required to initiate significant ablation suggests that the photoetching mechanism is similar for all the polymers studied.

  11. Calcified lesion modeling for excimer laser ablation

    NASA Astrophysics Data System (ADS)

    Scott, Holly A.; Archuleta, Andrew; Splinter, Robert

    2009-06-01

    Objective: Develop a representative calcium target model to evaluate penetration of calcified plaque lesions during atherectomy procedures using 308 nm Excimer laser ablation. Materials and Methods: An in-vitro model representing human calcified plaque was analyzed using Plaster-of-Paris and cement based composite materials as well as a fibrinogen model. The materials were tested for mechanical consistency. The most likely candidate(s) resulting from initial mechanical and chemical screening was submitted for ablation testing. The penetration rate of specific multi-fiber catheter designs and a single fiber probe was obtained and compared to that in human cadaver calcified plaque. The effects of lasing parameters and catheter tip design on penetration speed in a representative calcified model were verified against the results in human cadaver specimens. Results: In Plaster of Paris, the best penetration was obtained using the single fiber tip configuration operating at 100 Fluence, 120 Hz. Calcified human lesions are twice as hard, twice as elastic as and much more complex than Plaster of Paris. Penetration of human calcified specimens was highly inconsistent and varied significantly from specimen to specimen and within individual specimens. Conclusions: Although Plaster of Paris demonstrated predictable increases in penetration with higher energy density and repetition rate, it can not be considered a totally representative laser ablation model for calcified lesions. This is in part due to the more heterogeneous nature and higher density composition of cadaver intravascular human calcified occlusions. Further testing will require a more representative model of human calcified lesions.

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

    SciTech Connect

    Zheng, Buxiang; Jiang, Gedong; Wang, Wenjun Wang, Kedian; Mei, Xuesong

    2014-03-15

    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/cm{sup 2}.

  13. [Ablative and fractional lasers].

    PubMed

    Beylot, C; Grognard, C; Michaud, T

    2009-10-01

    The use of pulsed or scanning Carbon Dioxide, and pulsed Erbium-YAG lasers allows the programmable and reproducible photocoagulation of thin layers of the epidermis and superficial dermis. Thermal damage depends on the type of laser and is greater with CO(2) lasers. The degree of neocollagenesis is proportional to the thermal damage and is better with CO(2) lasers. Their main indication is the correction of photoaged facial skin but they can also be used for corrective dermatology, e.g. for scars and genodermatosis. Results are highly satisfactory but the technique is invasive and the patient experiences a social hindrance of around two weeks. Fractionated techniques treat 25% of the defective skin area at each session in noncontiguous microzones; four sessions are therefore necessary to treat the entire cutaneous surface. The treatment is given under topical anesthesia and is much less invasive, particularly with nonablative fractional laser treatment in which photothermolysis does not penetrate below the epidermis and/or the effects are slight, with no or very little social isolation. However, the results are much less satisfactory than the results of ablative laser and there is no firming effect. Other zones than the face can be treated. With the fractional CO(2) and Erbium ablative lasers, which have multiplied over the past 2 years, the much wider impacts cause perforation of the epidermis and there is a zone of ablation by laser photovaporization, with a zone of thermal damage below. The results are better in correcting photoaging of the face, without, however, achieving the efficacy of ablative lasers, which remain the reference technique. However, the effects are not insignificant, requiring at least 5 days of social isolation.

  14. Radiative ablation of disks around massive stars

    NASA Astrophysics Data System (ADS)

    Kee, Nathaniel Dylan

    Hot, massive stars (spectral types O and B) have extreme luminosities (10. 4 -10. 6 L?) that drive strong stellar winds through UV line-scattering.Some massive stars also have disks, formed by either decretion from the star (as in the rapidly rotating "Classical Be stars"), or accretion during the star's formation. This dissertation examines the role of stellar radiation in driving (ablating) material away from these circumstellar disks. A key result is that the observed month to year decay of Classical Be disks can be explained by line-driven ablation without, as previously done, appealing to anomalously strong viscous diffusion. Moreover, the higher luminosity of O stars leads to ablation of optically thin disks on dynamical timescales of order a day, providing a natural explanation for the lack of observed Oe stars. In addition to the destruction of Be disks, this dissertation also introduces a model for their formation by coupling observationally inferred non-radial pulsation modes and rapid stellar rotation to launch material into orbiting Keplerian disks of Be-like densities. In contrast to such Be decretion disks, star-forming accretion disks are much denser and so are generally optically thick to continuum processes. To circumvent the computational challenges associated with radiation hydrodynamics through optically thick media, we develop an approximate method for treating continuum absorption in the limit of geometrically thin disks. The comparison of ablation with and without continuum absorption shows that accounting for disk optical thickness leads to less than a 50% reduction in ablation rate, implying that ablation rate depends mainly on stellar properties like luminosity. Finally, we discuss the role of "thin-shell mixing" in reducing X-rays from colliding wind binaries. Laminar, adiabatic shocks produce well understood X-ray emission, but the emission from radiatively cooled shocks is more complex due to thin-shell instabilities. The parameter

  15. Areal studies aid protection of ground-water quality in Illinois, Indiana, and Wisconsin

    USGS Publications Warehouse

    Mills, Patrick C.; Kay, Robert T.; Brown, Timothy A.; Yeskis, Douglas J.

    1999-01-01

    In 1991, the U.S. Geological Survey, in cooperation with the U.S. Environmental Protection Agency, initiated studies designed to characterize the ground-water quality and hydrogeology in northern Illinois, and southern and eastern Wisconsin (with a focus on the north-central Illinois cities of Belvidere and Rockford, and the Calumet region of northeastern Illinois and northwestern Indiana). These areas are considered especially susceptible to ground-water contamination because of the high density of industrial and waste-disposal sites and the shallow depth to the unconsolidated sand and gravel aquifers and the fractured, carbonate bedrock aquifers that underlie the areas. The data and conceptual models of ground-water flow and contaminant distribution and movement developed as part of the studies have allowed Federal, State, and local agencies to better manage, protect, and restore the water supplies of the areas. Water-quality, hydrologic, geologic, and geophysical data collected as part of these areal studies indicate that industrial contaminants are present locally in the aquifers underlying the areas. Most of the contaminants, particularly those at concentrations that exceeded regulatory water-quality levels, were detected in the sand and gravel aquifers near industrial or waste-disposal sites. In water from water-supply wells, the contaminants that were present generally were at concentrations below regulatory levels. The organic compounds detected most frequently at concentrations near or above regulatory levels varied by area. Trichloroethene, tetrachloroethene, and 1,1,1-trichloroethane (volatile chlorinated compounds) were most prevalent in north-central Illinois; benzene (a petroleum-related compound) was most prevalent in the Calumet region. Differences in the type of organic compounds that were detected in each area likely reflect differences in the types of industrial sites that predominate in the areas. Nickel and aluminum were the trace metals

  16. OCDR guided laser ablation device

    DOEpatents

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

    2002-01-01

    A guided laser ablation device. The device includes a mulitmode laser ablation fiber that is surrounded by one or more single mode optical fibers that are used to image in the vicinity of the laser ablation area to prevent tissue damage. The laser ablation device is combined with an optical coherence domain reflectometry (OCDR) unit and with a control unit which initializes the OCDR unit and a high power laser of the ablation device. Data from the OCDR unit is analyzed by the control unit and used to control the high power laser. The OCDR images up to about 3 mm ahead of the ablation surface to enable a user to see sensitive tissue such as a nerve or artery before damaging it by the laser.

  17. Catheter Ablation for Ventricular Arrhythmias

    PubMed Central

    Nof, Eyal; Stevenson, William G; John, Roy M

    2013-01-01

    Catheter ablation has emerged as an important and effective treatment option for many recurrent ventricular arrhythmias. The approach to ablation and the risks and outcomes are largely determined by the nature of the severity and type of underlying heart disease. In patients with structural heart disease, catheter ablation can effectively reduce ventricular tachycardia (VT) episodes and implantable cardioverter defibrillator (ICD) shocks. For VT and symptomatic premature ventricular beats that occur in the absence of structural heart disease, catheter ablation is often effective as the sole therapy. Advances in catheter technology, imaging and mapping techniques have improved success rates for ablation. This review discusses current approaches to mapping and ablation for ventricular arrhythmias. PMID:26835040

  18. Thermal ablation of an aluminium film upon absorption of a femtosecond laser pulse

    SciTech Connect

    Bezhanov, S G; Kanavin, A P; Uryupin, S A

    2016-02-28

    We have found the time dependence of the ablation depth of aluminium irradiated by a femtosecond laser pulse. It is shown to what extent an increase in the radiation energy flux density leads to an increase in the quasi-stationary value of the ablation depth. By reducing the aluminium film thickness down to one hundred nanometres and less, the ablation depth significantly increases. At the same time, the quasi-stationary value of the ablation depth of a thin film is obtained due to the removal of heat from the focal spot region. (interaction of laser radiation with matter. laser plasma)

  19. Radiofrequency Ablation for Liver Cancer.

    PubMed

    Jacobs, Amy

    2015-01-01

    Interventional ablative technologies aided by imaging techniques such as ultrasonography, computed tomography, and magnetic resonance imaging have been crucial in managing patients with primary liver cancer and liver metastases over the past 20 years. Several ablative technologies have been used to treat liver cancer; however, radiofrequency ablation (RFA) has emerged as the most common ablative therapy for hepatic lesions, both in the United States and globally. RFA is the treatment of choice for patients who cannot have surgical resection of the liver. This article focuses on the role of imaging in RFA treatment of primary and metastatic hepatic lesions.

  20. Areal Theory

    NASA Astrophysics Data System (ADS)

    Curtright, Thomas

    2002-07-01

    New features are described for models with multi-particle area-dependent potentials, in any number of dimensions. The corresponding many-body field theories are investigated for classical configurations. Some explicit solutions are given, and some conjectures are made about chaos in such field theories.

  1. Ventricular Arrhythmias from the Left Ventricular Summit: Critical Importance of Anatomy, Imaging, and Detailed Mapping to Allow Safe and Effective Ablation.

    PubMed

    Kumar, Saurabh; Tedrow, Usha B; Stevenson, William G

    2016-03-01

    Ventricular arrhythmias arising from the region of the left ventricular summit can be challenging for catheter-based percutaneous ablation. A detailed knowledge of the anatomy of this region and the need of high-density mapping of surrounding structures are critical in ensuring safe and effective ablation. This case-based review focuses on the particular challenges with ablation in this region.

  2. Average areal water equivalent of snow in a mountain basin using microwave and visible satellite data

    NASA Technical Reports Server (NTRS)

    Rango, A.; Martinec, J.; Chang, A. T. C.; Foster, J. L.; Vankatwijk, V.

    1988-01-01

    Satellite microwave data were used to evaluate the average areal water equivalent of snow cover in the mountainous Rio Grande basin of Colorado. Areal water equivalent data for the basin were obtained from contoured values of point measurements and from zonal water volume values generated by a snowmelt runoff model. Comparison of these snow water equivalent values shows the model values to consistently exceed the contoured values, probably because of the narrow elevation range in the lower part of the basin where the point measurements are concentrated. A significant relationship between the difference in microwave brightness temperatures at two different wavelengths and a basin-wide average snow water equivalent value is obtained. The average water equivalent of the snow cover in the basin was derived from differences of the microwave brightness temperatures.

  3. Average areal water equivalent of snow in a mountain basin using microwave and visible satellite data

    NASA Technical Reports Server (NTRS)

    Rango, Albert; Van Katwijk, Victor F.; Martinec, Jaroslav; Chang, Alfred T. C.; Foster, James L.

    1989-01-01

    Satellite microwave data were used to evaluate the average areal water equivalent of snow cover in the mountainous Rio Grande basin of Colorado. Areal water equivalent data for the basin were obtained from contoured values of point measurements and from zonal water volume values generated by a snowmelt runoff model. Comparison of these snow water equivalent values shows the model values to consistently exceed the contoured values, probably because of the narrow elevation range in the lower part of the basin where the point measurements are concentrated. A significant relationship between the difference in microwave brightness temperatures at two different wavelengths and a basin-wide average snow water equivalent value is obtained. The average water equivalent of the snow cover in the basin was derived from differences of the microwave brightness temperatures.

  4. Unsupervised classification and areal measurement of land and water coastal features on the Texas coast

    NASA Technical Reports Server (NTRS)

    Flores, L. M.; Reeves, C. A.; Hixon, S. B.; Paris, J. F.

    1973-01-01

    Multispectral scanner (MSS) digital data from ERTS-1 was used to delineate coastal land, vegetative, and water features in two portions of the Texas Coastal Zone. Data (Scene ID's 1037-16244 and 1037-16251) acquired on August 29, 1972, were analyzed on NASA Johnson Space Center systems through the use of two clustering algorithms. Seventeen to 30 spectrally homogeneous classes were so defined. Many classes were identified as being pure features such as water masses, salt marsh, beaches, pine, hardwoods, and exposed soil or construction materials. Most classes were identified to be mixtures of the pure class types. Using an objective technique for measuring the percentage of wetland along salt marsh boundaries, an analysis was made of the accuracy of areal measurement of salt marshes. Accuracies ranged from 89 to 99 percent. Aircraft photography was used as the basis for determining the true areal size of salt marshes in the study sites.

  5. Experimental investigation of the laser ablation process on wood surfaces

    NASA Astrophysics Data System (ADS)

    Panzner, M.; Wiedemann, G.; Henneberg, K.; Fischer, R.; Wittke, Th.; Dietsch, R.

    1998-05-01

    Processing of wood by conventional mechanical tools like saws or planes leaves behind a layer of squeezed wood only slightly adhering to the solid wood surface. Laser ablation of this layer could improve the durability of coatings and glued joints. For technical applications, thorough knowledge about the laser ablation process is necessary. Results of ablation experiments by excimer lasers, Nd:YAG lasers, and TEA-CO 2 lasers on surfaces of different wood types and cut orientations are shown. The process of ablation was observed by a high-speed camera system and optical spectroscopy. The influence of the experimental parameters are demonstrated by SEM images and measurement of the ablation rate depending on energy density. Thermal effects like melting and also carbonizing of cellulose were found for IR- and also UV-laser wavelengths. Damage of the wood surface after laser ablation was weaker for excimer lasers and CO 2-TEA lasers. This can be explained by the high absorption of wood in the ultraviolet and middle infrared spectral range. As an additional result, this technique provides an easy way for preparing wood surfaces with excellently conserved cellular structure.

  6. Surveying the earth's environment from space - Spectral, areal, temporal coverage trends

    NASA Technical Reports Server (NTRS)

    Nagler, R. G.

    1977-01-01

    Attention is given to various areas of satellite applications to monitoring the earth's environment. These trends primarily concern spectral, areal, and temporal coverage. Various environmental monitors are discussed in terms of derived economic benefits. Several types of remote sensors for earth applications are described, noting spectral channels, resolution cell size, swath width, and data rate. A sample environmental monitoring system is presented which includes five geostationary satellites, and three or four low earth orbit spacecraft

  7. 3D Interconnected Electrode Materials with Ultrahigh Areal Sulfur Loading for Li-S Batteries.

    PubMed

    Fang, Ruopian; Zhao, Shiyong; Hou, Pengxiang; Cheng, Min; Wang, Shaogang; Cheng, Hui-Ming; Liu, Chang; Li, Feng

    2016-05-01

    Sulfur electrodes based on a 3D integrated hollow carbon fiber foam (HCFF) are synthesized with high sulfur loadings of 6.2-21.2 mg cm(-2) . Benefiting from the high electrolyte absorbability of the HCFF and the multiple conductive channels, the obtained electrode demonstrates excellent cycling stability and a high areal capacity of 23.32 mAh cm(-2) , showing great promise in commercially viable Li-S batteries.

  8. MAUP: Modifiable Areal Unit Problem in raster GIS datasets. Raster pixels as modifiable areas

    USGS Publications Warehouse

    Lyn, Usery E.

    2001-01-01

    The Modifiable Areal Unit Problem (MAUP) is a well-studied aspect of geographic phenomena. It is usually associated with socio-economic data collected by census enumeration units. This problem also applies directly to geographic data in raster formats, including both GIS categorical data layers and remotely sensed images. The author briefly provides a foundation for examining the component parts of the MAUP in remotely sensed raster data.

  9. Temperature dependent ablation threshold in silicon using ultrashort laser pulses

    NASA Astrophysics Data System (ADS)

    Thorstensen, Jostein; Erik Foss, Sean

    2012-11-01

    We have experimentally investigated the ablation threshold in silicon as a function of temperature when applying ultrashort laser pulses at three wavelengths. By varying the temperature of a silicon substrate from room temperature to 320 °C, we observe that the ablation threshold for a 3 ps pulse using a wavelength of 1030 nm drops from 0.43 J/cm2 to 0.24 J/cm2, a reduction of 43%. For a wavelength of 515 nm, the ablation threshold drops from 0.22 J/cm2 to 0.15 J/cm2, a reduction of 35%. The observed ablation threshold for pulses at 343 nm remains constant with temperature, at 0.10 J/cm2. These results indicate that substrate heating is a useful technique for lowering the ablation threshold in industrial silicon processing using ultrashort laser pulses in the IR or visible wavelength range. In order to investigate and explain the observed trends, we apply the two-temperature model, a thermodynamic model for investigation of the interaction between silicon and ultrashort laser pulses. Applying the two-temperature model implies thermal equilibrium between optical and acoustic phonons. On the time scales encountered herein, this need not be the case. However, as discussed in the article, the two-temperature model provides valuable insight into the physical processes governing the interaction between the laser light and the silicon. The simulations indicate that ablation occurs when the number density of excited electrons reaches the critical electron density, while the lattice remains well below vaporization temperature. The simulated laser fluence required to reach critical electron density is also found to be temperature dependent. The dominant contributor to increased electron density is, in the majority of the investigated cases, the linear absorption coefficient. Two-photon absorption and impact ionization also generate carriers, but to a lesser extent. As the linear absorption coefficient is temperature dependent, we find that the simulated reduction in

  10. High temperature ablative foam

    NASA Technical Reports Server (NTRS)

    Liu, Matthew T. (Inventor)

    1992-01-01

    An ablative foam composition is formed of approximately 150 to 250 parts by weight polymeric isocyanate having an isocyanate functionality of 2.6 to 3.2; approximately 15 to 30 parts by weight reactive flame retardant having a hydroxyl number range from 200-260; approximately 10 to 40 parts by weight non-reactive flame retardant; approximately 10 to 40 parts by weight nonhydrolyzable silicone copolymer having a hydroxyl number range from 75-205; and approximately 3 to 16 parts by weight amine initiated polyether resin having an isocyanate functionality greater than or equal to 3.0 and a hydroxyl number range from 400-800.

  11. Matricectomy and nail ablation.

    PubMed

    Baran, Robert; Haneke, Eckart

    2002-11-01

    Matricectomy refers to the complete extirpation of the nail matrix, resulting in permanent nail loss. Usually however, matricectomy is only partial, restricted to one or both lateral horns of the matrix. Nail ablation is the definitive removal of the entire nail organ. The most important common denominator in the successful matricectomy is the total removal or destruction of the matrix tissue. Matricectomy may be indicated for the management of onychauxis, onychogryphosis, congenital nail dystrophies, and chronic painful nail, such as recalcitrant ingrown toenail or split within the medial or lateral one-third of the nail.

  12. Accuracy and Precision of Silicon Based Impression Media for Quantitative Areal Texture Analysis

    PubMed Central

    Goodall, Robert H.; Darras, Laurent P.; Purnell, Mark A.

    2015-01-01

    Areal surface texture analysis is becoming widespread across a diverse range of applications, from engineering to ecology. In many studies silicon based impression media are used to replicate surfaces, and the fidelity of replication defines the quality of data collected. However, while different investigators have used different impression media, the fidelity of surface replication has not been subjected to quantitative analysis based on areal texture data. Here we present the results of an analysis of the accuracy and precision with which different silicon based impression media of varying composition and viscosity replicate rough and smooth surfaces. Both accuracy and precision vary greatly between different media. High viscosity media tested show very low accuracy and precision, and most other compounds showed either the same pattern, or low accuracy and high precision, or low precision and high accuracy. Of the media tested, mid viscosity President Jet Regular Body and low viscosity President Jet Light Body (Coltène Whaledent) are the only compounds to show high levels of accuracy and precision on both surface types. Our results show that data acquired from different impression media are not comparable, supporting calls for greater standardisation of methods in areal texture analysis. PMID:25991505

  13. Accuracy and Precision of Silicon Based Impression Media for Quantitative Areal Texture Analysis

    NASA Astrophysics Data System (ADS)

    Goodall, Robert H.; Darras, Laurent P.; Purnell, Mark A.

    2015-05-01

    Areal surface texture analysis is becoming widespread across a diverse range of applications, from engineering to ecology. In many studies silicon based impression media are used to replicate surfaces, and the fidelity of replication defines the quality of data collected. However, while different investigators have used different impression media, the fidelity of surface replication has not been subjected to quantitative analysis based on areal texture data. Here we present the results of an analysis of the accuracy and precision with which different silicon based impression media of varying composition and viscosity replicate rough and smooth surfaces. Both accuracy and precision vary greatly between different media. High viscosity media tested show very low accuracy and precision, and most other compounds showed either the same pattern, or low accuracy and high precision, or low precision and high accuracy. Of the media tested, mid viscosity President Jet Regular Body and low viscosity President Jet Light Body (Coltène Whaledent) are the only compounds to show high levels of accuracy and precision on both surface types. Our results show that data acquired from different impression media are not comparable, supporting calls for greater standardisation of methods in areal texture analysis.

  14. A multivariate spatial mixture model for areal data: examining regional differences in standardized test scores

    PubMed Central

    Neelon, Brian; Gelfand, Alan E.; Miranda, Marie Lynn

    2013-01-01

    Summary Researchers in the health and social sciences often wish to examine joint spatial patterns for two or more related outcomes. Examples include infant birth weight and gestational length, psychosocial and behavioral indices, and educational test scores from different cognitive domains. We propose a multivariate spatial mixture model for the joint analysis of continuous individual-level outcomes that are referenced to areal units. The responses are modeled as a finite mixture of multivariate normals, which accommodates a wide range of marginal response distributions and allows investigators to examine covariate effects within subpopulations of interest. The model has a hierarchical structure built at the individual level (i.e., individuals are nested within areal units), and thus incorporates both individual- and areal-level predictors as well as spatial random effects for each mixture component. Conditional autoregressive (CAR) priors on the random effects provide spatial smoothing and allow the shape of the multivariate distribution to vary flexibly across geographic regions. We adopt a Bayesian modeling approach and develop an efficient Markov chain Monte Carlo model fitting algorithm that relies primarily on closed-form full conditionals. We use the model to explore geographic patterns in end-of-grade math and reading test scores among school-age children in North Carolina. PMID:26401059

  15. Data Fitting to Study Ablated Hard Dental Tissues by Nanosecond Laser Irradiation

    PubMed Central

    Abdel-Daiem, A. M.; Ansari, M. Shahnawaze; Babkair, Saeed S.; Salah, Numan A.; Al-Mujtaba, A.

    2016-01-01

    Laser ablation of dental hard tissues is one of the most important laser applications in dentistry. Many works have reported the interaction of laser radiations with tooth material to optimize laser parameters such as wavelength, energy density, etc. This work has focused on determining the relationship between energy density and ablation thresholds using pulsed, 5 nanosecond, neodymium-doped yttrium aluminum garnet; Nd:Y3Al5O12 (Nd:YAG) laser at 1064 nanometer. For enamel and dentin tissues, the ablations have been performed using laser-induced breakdown spectroscopy (LIBS) technique. The ablation thresholds and relationship between energy densities and peak areas of calcium lines, which appeared in LIBS, were determined using data fitting. Furthermore, the morphological changes were studied using Scanning Electron Microscope (SEM). Moreover, the chemical stability of the tooth material after ablation has been studied using Energy-Dispersive X-Ray Spectroscopy (EDX). The differences between carbon atomic % of non-irradiated and irradiated samples were tested using statistical t-test. Results revealed that the best fitting between energy densities and peak areas of calcium lines were exponential and linear for enamel and dentin, respectively. In addition, the ablation threshold of Nd:YAG lasers in enamel was higher than that of dentin. The morphology of the surrounded ablated region of enamel showed thermal damages. For enamel, the EDX quantitative analysis showed that the atomic % of carbon increased significantly when laser energy density increased. PMID:27228169

  16. Dynamics of multiple plumes in laser ablation: Modeling of the shielding effect

    NASA Astrophysics Data System (ADS)

    Zinovik, Igor; Povitsky, Alex

    2006-07-01

    The scattering and absorption of laser radiation by previously ablated plumes in laser ablation (known as the shielding effect) dramatically affect the efficiency of laser ablation process. The ablated plumes consisting of water vapor, droplets, and particles are modeled as a gas-particle equilibrium mixture by solution of the Euler equations combined with the transport equation for the ratio of heat capacities. Shielding effect on the overall ablated mass by multiple plumes is studied for a wide range of concentration of particles in vaporized plumes, various laser repetition rates, scattering, and absorption of laser energy. The shielding phenomenon is studied for short sequences of discrete plumes to focus on the shielding effect of individual plumes. The results of numerical modeling were compared to experimental results of laser-induced water explosive vaporization. Ablation rate was calculated for a single ablated plume and for the sequence of six laser pulses at the repetition rates of 0.33 and 1MHz at which gas dynamics interactions between plumes are strong but plumes have not yet form a continuous jet. A single ablated plume has an initial semispherical shape which transforms into mushroomlike cloud with a thin stem and a ring vortex as it was observed in experiments with water and cornea ablation. For the plume with a given ablated mass, the longer ejection of plume with smaller density produces the plume with smaller shielding capacity. For multiple laser pulses, the velocity of ejected mixture increases from the center of the target to its periphery because of the shielding effect. The ablated mass of the current plume depends on the attenuation of the incident laser beam energy caused by the propagation of laser beam through previously ablated plumes. In the case of laser energy absorption, the ablation rate per pulse exceeds 2-2.5 times the rate obtained for the laser energy scattering.

  17. Laser ablation in analytical chemistry.

    PubMed

    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.

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

    NASA Technical Reports Server (NTRS)

    Maahs, H. G.

    1972-01-01

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

  19. Simulation of Pellet Ablation

    NASA Astrophysics Data System (ADS)

    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.

  20. X-ray refraction effect and density determination of steep-gradient, high-density plasma

    NASA Astrophysics Data System (ADS)

    Miyanaga, N.; Kato, Y.; Yamanaka, C.

    1982-12-01

    X-ray defraction due to the steep density gradient of a laser-produced plasma has been observed. Distribution of the density gradient was determined from the measured refraction angle. Estimation of the radial density profile and the density scale length in the high-density region near the ablation surface are presented.

  1. Low cost fabrication of ablative heat shields

    NASA Technical Reports Server (NTRS)

    Cecka, A. M.; Schofield, W. C.

    1972-01-01

    A material and process study was performed using subscale panels in an attempt to reduce the cost of fabricating ablative heat shield panels. Although no improvements were made in the material formulation, a significant improvement was obtained in the processing methods compared to those employed in the previous work. The principal feature of the new method is the press filling and curing of the ablation material in a single step with the bonding and curing of the face sheet. This method was chosen to replace the hand troweling and autoclave curing procedure used previously. Double-curvature panels of the same size as the flat panels were fabricated to investigate fabrication problems. It was determined that the same materials and processes used for flat panels can be used to produce the curved panels. A design with severe curvatures consisting of radii of 24 x 48 inches was employed for evaluation. Ten low-density and ten high-density panels were fabricated. With the exception of difficulties related to short run non-optimum tooling, excellent panel filling and density uniformity were obtained.

  2. Experimental investigation on thermal ablation of carbon-fiber/epoxy composite irradiated by continuous wave laser

    NASA Astrophysics Data System (ADS)

    He, Minbo; Ma, Zhiliang; Chen, Linzhu; Lin, Xinwei; Zhou, Menglian

    2015-05-01

    The tests of carbon-fiber/epoxy composite laminates, subjected to a tangential gas-flow and 1070 nm continuous wave laser are carried out to acquire the ablation laws of samples on the conditions of different gas-flow. Simultaneously, considered the images from camera of large dynamic range, the damage laws of samples are also obtained for various laser power densities. Experimental results reveal that, without airflow on sample surface, the smoke caused by laser heating can be quickly on fire which causes a burn damage on the surface of samples so that the mass loss is most of all. However, the tangential airflow can remove away the smoke which has a weakening effect on the energy of incidence laser. So the ablation depth has an obvious increase in laser irradiation area. Unlike airflow, nitrogen flow can obviously restrain oxidation ablation on surface so that the ablation damage in laser irradiation area is relatively not severe. On the other hand, as laser power density increases, the mass loss of samples continues to rise but isn't proportional. And the ablation heat with the increase of power density shows a complex change. Below power density of 390 W/cm2, the mass loss mainly depends on the pyrolysis of epoxy while the ablation heat has a gradual decrease. Along with power density increasing but less than 1330 W/cm2 , the oxidation ablation of carbon fibers will be a leading factor and the ablation heat shows a little increase. Above power density of 1330 W/cm2 , the carbon fibers turn up the phenomenon of sublimation. What's more, airflow removed effects will be enhanced in high temperature. In this case, the ablation heat again has a trend of decrease.

  3. Assessing Modifiable Areal Unit Problem in the Analysis of Deforestation Drivers Using Remote Sensing and Census Data

    NASA Astrophysics Data System (ADS)

    Mas, J. F.; Pérez Vega, A.; Andablo Reyes, A.; Castillo Santiago, M. A.; Flamenco Sandoval, A.

    2015-08-01

    In order to identify drivers of land use / land cover change (LUCC), the rate of change is often compared with environmental and socio-economic variables such as slope, soil suitability or population density. Socio-economic information is obtained from census data which are collected for individual households but are commonly presented in aggregate on the basis of geographical units as municipalities. However, a common problem, known as the modifiable areal unit problem (MAUP), is that the results of statistical analysis are not independent of the scale and the spatial configuration of the units used to aggregate the information. In this article, we evaluate how strong MAUP effects are for a study on the deforestation drivers in Mexico at municipality level. This was done by taking socio-economic variables from the 2010 Census of Mexico along with environmental variables and the rate of deforestation. As population census is given for each human settlement and environmental variables are obtained from high resolution spatial database, it was possible to aggregate the information using spatial units ("pseudo municipalities") with different sizes in order to observe the effect of scale and aggregation on the values of bivariate correlations (Pearsons r) between pairs of variables. We found that MAUP produces variations in the results, and we observed some variable pairs and some configurations of the spatial units where the effect was substantial.

  4. Pellet ablation and temperature profile measurements in TFTR

    SciTech Connect

    Owens, D.K.; Schmidt, G.L.; Cavallo, A.; Grek, B.; Hulse, R.; Johnson, D.; Mansfield, D.; McNeill, D.; Park, H.; Taylor, G.

    1988-01-01

    Single and multiple deuterium pellets have been injected into a variety of TFTR plasmas, including ohmically heated plasmas with wide range of electron temperatures, neutral beam heated plasmas at several NBI powers and high T/sub e/, post NBI plasmas. Pellet penetration into these plasmas was determined by measuring the pellet speed and duration of the H/sub ..cap alpha..//D/sub ..cap alpha../ light emission during pellet ablation in the plasma. These penetration measurements are compared to the predicted penetration computed using the ablation model developed by Oak Ridge National Laboratory. The plasma density profiles before and after pellet injection are used to estimate the number of particles deposited in the plasma. The plasma particle increase compared to the estimated number of atoms in the pellet yields a measure of the fueling efficiency of pellets in TFTR. The ablation cloud parameters are discussed based on polychromater measurements of the H/sub ..cap alpha..//D/sub ..cap alpha../ line emission from the neutral cloud surrounding the pellet. The electron temperature profile evolution after pellet injection is examined for the case of multiple pellet injection into an ohmically heated plasma. The ORNL pellet ablation code was used to compare measured pellet penetration depths with a theoretical model. The measured input parameters to the model are the electron density and temperature profiles, the neutral beam heating profile, the neutral density profile, the pellet size, pellet speed and pellet composition. The free parameter in the model is the thickness of the neutral cloud surrounding the pellet. This parameter is adjusted to arrive at a reasonable agreement between measured and calculated pellet penetration depths. The output of the model which is directly comparable to experiment is the calculated ablation rate. It is assumed that the broad-band H/sub ..cap alpha..//D/sub ..cap alpha../ emission is proportional to the ablation rate.

  5. Three-dimensional Ni/TiO2 nanowire network for high areal capacity lithium ion microbattery applications.

    PubMed

    Wang, Wei; Tian, Miao; Abdulagatov, Aziz; George, Steven M; Lee, Yung-Cheng; Yang, Ronggui

    2012-02-08

    The areal capacity of nanowire-based microbatteries can be potentially increased by increasing the length of nanowires. However, agglomeration of high aspect ratio nanowire arrays could greatly degrade the performance of nanowires for lithium ion (Li-ion) battery applications. In this work, a three-dimensional (3-D) Ni/TiO(2) nanowire network was successfully fabricated using a 3-D porous anodic alumina (PAA) template-assisted electrodeposition of Ni followed by TiO(2) coating using atomic layer deposition. Compared to the straight Ni/TiO(2) nanowire arrays fabricated using conventional PAA templates, the 3-D Ni/TiO(2) nanowire network shows higher areal discharging capacity. The areal capacity increases proportionally with the length of nanowires. With a stable Ni/TiO(2) nanowire network structure, 100% capacity is retained after 600 cycles. This work paves the way to build reliable 3-D nanostructured electrodes for high areal capacity microbatteries.

  6. Plastic ablator ignition capsule design for the National Ignition Facility

    SciTech Connect

    Clark, D S; Haan, S W; Hammel, B A; Salmonson, J D; Callahan, D A; Town, R J

    2009-10-06

    This paper describes current efforts to develop a plastic ablator capsule design for the first ignition attempt on the National Ignition Facility. The trade-offs in capsule scale and laser energy that must be made to achieve ignition probabilities comparable to those with other candidate ablators, beryllium and high-density carbon, are emphasized. Large numbers of 1-D simulations, meant to assess the statistical behavior of the target design, as well as 2-D simulations to assess the target's susceptibility to Rayleigh-Taylor growth are discussed.

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

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

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

  8. Investigation of low-cost fabrication of ablative heat shields

    NASA Technical Reports Server (NTRS)

    Massions, V. P.; Mach, R. W.

    1973-01-01

    The fabrication, testing, and evaluation of materials and techniques employed in the fabrication of ablative heat shield panels are described. Results of this effort show projected reductions in labor man-hours for dielectric curing of panels when compared to panels molded in a steam-heated press. In addition, panels were fabricated with more than one density within the cross-section. These dual-density panels show significant weight and cost reduction potentials.

  9. Thermal Ablation of Lung Tissue: In Vivo Experimental Comparison of Microwave and Radiofrequency

    SciTech Connect

    Crocetti, Laura Bozzi, Elena; Faviana, Pinuccia; Cioni, Dania; Della Pina, Clotilde; Sbrana, Alberto; Fontanini, Gabriella; Lencioni, Riccardo

    2010-08-15

    This study was designed to compare feasibility, safety, and effectiveness of microwave (MW) ablation versus radiofrequency (RF) ablation of lung tissue in a rabbit model. Twenty New Zealand White rabbits were submitted to MW (n = 10, group A) or RF ablation (n = 10, group B). The procedures were performed with a prototype MW ablation device with a 1.6-cm radiating section antenna (Valleylab MW Ablation System) and with a 2-cm exposed-tip RF electrode (Cool-tip RF Ablation System). At immediate computed tomography increase in density, maximum diameters (D1-D3) of ablation zones were measured and ablation volume was calculated. Histopathologic assessment was performed 3 and 7 days after the procedure. Technical success was achieved in nine of 10 rabbits in each group. One death occurred in group B. Complications included pneumothorax (group A, n = 4; group B, n = 4), abscess (group A, n = 1; group B, n = 1), and thoracic wall burn (group A, n = 4). No significant differences were demonstrated in attenuation increase (P = 0.73), dimensions (P = 0.28, 0.86, 0.06, respectively, comparing D1-D3) and volume (P = 0.17). At histopathology, ablation zones were similar, with septal necrosis, edema, hemorrhage, and peripheral lymphocytic infiltrate. Complete thrombosis of more than 90% of vessels up to 2 mm in diameter was depicted at the periphery of the ablation zone in group A specimens. In group B specimens, complete thrombosis was depicted in 20% of vessels. Feasibility and safety of MW and RF ablation are similar in a lung rabbit model. MW ablation produces a greater damage to peripheral small vessels inducing thrombosis.

  10. [New techniques of tumor ablation (microwaves, electroporation)].

    PubMed

    de Baere, T

    2011-09-01

    Since the introduction of radiofrequency tumor ablation of liver tumors in the late 1990s, local destructive therapies have been applied to lung, renal and bone lesions. In addition, new techniques have been introduced to compensate for the limitations of radiofrequency ablation, namely the reduced rate of complete ablation for tumors larger than 3 cm and tumors near vessels larger than 3 mm. Microwave ablation is currently evolving rapidly. While it is a technique based on thermal ablation similar to radiofrequency ablation, there are significant differences between both techniques. Electroporation, of interest because of the non-thermal nature of the ablation process, also is under evaluation.

  11. Ablative heat shield design for space shuttle

    NASA Technical Reports Server (NTRS)

    Seiferth, R. W.

    1973-01-01

    Ablator heat shield configuration optimization studies were conducted for the orbiter. Ablator and reusable surface insulation (RSI) trajectories for design studies were shaped to take advantage of the low conductance of ceramic RSI and high temperature capability of ablators. Comparative weights were established for the RSI system and for direct bond and mechanically attached ablator systems. Ablator system costs were determined for fabrication, installation and refurbishment. Cost penalties were assigned for payload weight penalties, if any. The direct bond ablator is lowest in weight and cost. A mechanically attached ablator using a magnesium subpanel is highly competitive for both weight and cost.

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

    PubMed

    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.

  13. Performance and Controllability of Pulsed Ion Beam Ablation Propulsion

    SciTech Connect

    Yazawa, Masaru; Buttapeng, Chainarong; Harada, Nobuhiro; Suematsu, Hisayuki; Jiang Weihua; Yatsui, Kiyoshi

    2006-05-02

    We propose novel propulsion driven by ablation plasma pressures produced by the irradiation of pulsed ion beams onto a propellant. The ion beam ablation propulsion demonstrates by a thin foil (50 {mu}mt), and the flyer velocity of 7.7 km/s at the ion beam energy density of 2 kJ/cm2 adopted by using the Time-of-flight method is observed numerically and experimentally. We estimate the performance of the ion beam ablation propulsion as specific impulse of 3600 s and impulse bit density of 1700 Ns/m2 obtained from the demonstration results. In the numerical analysis, a one-dimensional hydrodynamic model with ion beam energy depositions is used. The control of the ion beam kinetic energy is only improvement of the performance but also propellant consumption. The spacecraft driven by the ion beam ablation provides high performance efficiency with short-pulsed ion beam irradiation. The numerical results of the advanced model explained latent heat and real gas equation of state agreed well with experimental ones over a wide range of the incident ion beam energy density.

  14. The topographic development and areal parametric characterization of a stratified surface polished by mass finishing

    NASA Astrophysics Data System (ADS)

    Walton, Karl; Blunt, Liam; Fleming, Leigh

    2015-09-01

    Mass finishing is amongst the most widely used finishing processes in modern manufacturing, in applications from deburring to edge radiusing and polishing. Processing objectives are varied, ranging from the cosmetic to the functionally critical. One such critical application is the hydraulically smooth polishing of aero engine component gas-washed surfaces. In this, and many other applications the drive to improve process control and finish tolerance is ever present. Considering its widespread use mass finishing has seen limited research activity, particularly with respect to surface characterization. The objectives of the current paper are to; characterise the mass finished stratified surface and its development process using areal surface parameters, provide guidance on the optimal parameters and sampling method to characterise this surface type for a given application, and detail the spatial variation in surface topography due to coupon edge shadowing. Blasted and peened square plate coupons in titanium alloy are wet (vibro) mass finished iteratively with increasing duration. Measurement fields are precisely relocated between iterations by fixturing and an image superimposition alignment technique. Surface topography development is detailed with ‘log of process duration’ plots of the ‘areal parameters for scale-limited stratified functional surfaces’, (the Sk family). Characteristic features of the Smr2 plot are seen to map out the processing of peak, core and dale regions in turn. These surface process regions also become apparent in the ‘log of process duration’ plot for Sq, where lower core and dale regions are well modelled by logarithmic functions. Surface finish (Ra or Sa) with mass finishing duration is currently predicted with an exponential model. This model is shown to be limited for the current surface type at a critical range of surface finishes. Statistical analysis provides a group of areal parameters including; Vvc, Sq, and Sdq

  15. Areal 3-D seismic technique for reservoir delineation: Case history from offshore Niger Delta

    SciTech Connect

    Idowu, A.O. )

    1993-02-01

    In the 1950s, early exploration period in the Niger Delta witnessed the use of 2-D (two dimensional) seismic reflection method which adequate for imaging large subsurface geologic features including growth faulting and roll-over anticlines. This technique involves the Common-Depth-Point method (CDP) which acquires a plane of seismic information in distance along the surface and in time into the geological section, and is used to improve the signal-to-noise (S/N) ratio, to remove multiples and consequently give a representation of the subsurface particularly if the data are collected up- or downdip. By mid-1980s, the obvious geological structures have, in general, been discovered and it became necessary to adopt a more sophisticated technique such as the 3-D (three dimensional) seismic method to delineate more subtle reservoirs and resolve complex fault patterns in order to aid exploration as well as facilitate efficient field development. The case history discussed in this paper involves the use of areal 3-D seismic method for delineating the reservoir characterization of the O-field located in a shallow water area of the western Niger Delta. The areal 3-D seismic technique is superior to the earlier CDP method in that a cube of seismic data can be collected in two dimensions in space and one in time by a variety of techniques including the swath seismic shooting pattern adopted for gathering the 3-D data for the O-field's reservoir which involves the line of sources. The objective is to adequately sample the subsurface so that changes in various parameters such as the amplitude phase or power in the siesmic signal or velocity of propagation can be mapped areally and interpreted as an indication of changes in the physical properties of the rock matrix.

  16. TPS Ablator Technologies for Interplanetary Spacecraft

    NASA Technical Reports Server (NTRS)

    Curry, Donald M.

    2004-01-01

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

  17. An overview of beam diagnostic and control systems for 50 MeV AREAL Linac

    NASA Astrophysics Data System (ADS)

    Sargsyan, A. A.; Amatuni, G. A.; Sahakyan, V. V.; Zanyan, G. S.; Martirosyan, N. W.; Vardanyan, V. V.; Grigoryan, B. A.

    2017-03-01

    Advanced Research Electron Accelerator Laboratory (AREAL) is an electron linear accelerator project with a laser driven RF gun being constructed at CANDLE Synchrotron Research Institute. After the successful operation of the gun section at 5 MeV, a program of facility energy enhancement up to 50 MeV is launched. In this paper the current status of existing diagnostic and control systems, as well as the results of electron beam parameter measurements are presented. The approaches of intended diagnostic and control systems for the upgrade program are also described.

  18. Ablative Laser Propulsion Using Multi-Layered Material Systems

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  19. Plastic ablator ignition capsule design for the National Ignition Facility

    SciTech Connect

    Clark, D S; Haan, S W; Hammel, B A; Salmonson, J D; Callahan, D A; Town, R P

    2009-12-01

    The National Ignition Campaign, tasked with designing and fielding targets for fusion ignition experiments on the National Ignition Facility (NIF), has carried forward three complementary target designs for the past several years: a beryllium ablator design, a plastic ablator design, and a high-density carbon or synthetic diamond design. This paper describes current simulations and design optimization to develop the plastic ablator capsule design as a candidate for the first ignition attempt on NIF. The trade-offs in capsule scale and laser energy that must be made to achieve a comparable ignition probability to that with beryllium are emphasized. Large numbers of 1-D simulations, meant to assess the statistical behavior of the target design, as well as 2-D simulations to assess the target's susceptibility to Rayleigh-Taylor growth are presented.

  20. Plastic ablator ignition capsule design for the National Ignition Facility

    SciTech Connect

    Clark, Daniel S.; Haan, Steven W.; Hammel, Bruce A.; Salmonson, Jay D.; Callahan, Debra A.; Town, Richard P. J.

    2010-05-15

    The National Ignition Campaign, tasked with designing and fielding targets for fusion ignition experiments on the National Ignition Facility (NIF) [G. H. Miller, E. I. Moses, and C. R. Wuest, Nucl. Fusion 44, S228 (2004)], has carried forward three complementary target designs for the past several years: a beryllium ablator design, a plastic ablator design, and a high-density carbon or synthetic diamond design. This paper describes current simulations and design optimization to develop the plastic ablator capsule design as a candidate for the first ignition attempt on NIF. The trade-offs in capsule scale and laser energy that must be made to achieve a comparable ignition probability to that with beryllium are emphasized. Large numbers of one-dimensional simulations, meant to assess the statistical behavior of the target design, as well as two-dimensional simulations to assess the target's susceptibility to Rayleigh-Taylor growth are presented.

  1. Microscopic Scale Simulation of the Ablation of Fibrous Materials

    NASA Technical Reports Server (NTRS)

    Lachaud, Jean Romain; Mansour, Nagi N.

    2010-01-01

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

  2. Direct-drive–ignition designs with mid-Z ablators

    SciTech Connect

    Lafon, M.; Betti, R.; Anderson, K. S.; Collins, T. J. B.; Epstein, R.; McKenty, P. W.; Myatt, J. F.; Shvydky, A.; Skupsky, S.

    2015-03-15

    Achieving thermonuclear ignition using direct laser illumination relies on the capability to accelerate spherical shells to high implosion velocities while maintaining shell integrity. Ablator materials of moderate atomic number Z reduce the detrimental effects of laser–plasma instabilities in direct-drive implosions. To validate the physics of moderate-Z ablator materials for ignition target designs on the National Ignition Facility (NIF), hydro-equivalent targets are designed using pure plastic (CH), high-density carbon, and glass (SiO{sub 2}) ablators. The hydrodynamic stability of these targets is investigated through two-dimensional (2D) single-mode and multimode simulations. The overall stability of these targets to laser-imprint perturbations and low-mode asymmetries makes it possible to design high-gain targets. Designs using polar-drive illumination are developed within the NIF laser system specifications. Mid-Z ablator targets are an attractive candidate for direct-drive ignition since they present better overall performance than plastic ablator targets through reduced laser–plasma instabilities and a similar hydrodynamic stability.

  3. Modeling and Validation of Microwave Ablations with Internal Vaporization

    PubMed Central

    Chiang, Jason; Birla, Sohan; Bedoya, Mariajose; Jones, David; Subbiah, Jeyam; Brace, Christopher L.

    2014-01-01

    Numerical simulation is increasingly being utilized for computer-aided design of treatment devices, analysis of ablation growth, and clinical treatment planning. Simulation models to date have incorporated electromagnetic wave propagation and heat conduction, but not other relevant physics such as water vaporization and mass transfer. Such physical changes are particularly noteworthy during the intense heat generation associated with microwave heating. In this work, a numerical model was created that integrates microwave heating with water vapor generation and transport by using porous media assumptions in the tissue domain. The heating physics of the water vapor model was validated through temperature measurements taken at locations 5, 10 and 20 mm away from the heating zone of the microwave antenna in homogenized ex vivo bovine liver setup. Cross-sectional area of water vapor transport was validated through intra-procedural computed tomography (CT) during microwave ablations in homogenized ex vivo bovine liver. Iso-density contours from CT images were compared to vapor concentration contours from the numerical model at intermittent time points using the Jaccard Index. In general, there was an improving correlation in ablation size dimensions as the ablation procedure proceeded, with a Jaccard Index of 0.27, 0.49, 0.61, 0.67 and 0.69 at 1, 2, 3, 4, and 5 minutes. This study demonstrates the feasibility and validity of incorporating water vapor concentration into thermal ablation simulations and validating such models experimentally. PMID:25330481

  4. Direct-drive–ignition designs with mid-Z ablators

    SciTech Connect

    Lafon, M.; Betti, R.; Anderson, K. S.; Collins, T. J. B.; Epstein, R.; McKenty, P. W.; Myatt, J. F.; Shvydky, A.; Skupsky, S.

    2015-03-01

    Achieving thermonuclear ignition using direct laser illumination relies on the capability to accelerate spherical shells to high implosion velocities while maintaining shell integrity. Ablator materials of moderate atomic number Z reduce the detrimental effects of laser–plasma instabilities in direct-drive implosions. To validate the physics of moderate-Z ablator materials for ignition target designs on the National Ignition Facility (NIF), hydro-equivalent targets are designed using pure plastic (CH), high-density carbon, and glass (SiO2) ablators. The hydrodynamic stability of these targets is investigated through two-dimensional (2D) single-mode and multimode simulations. The overall stability of these targets to laser-imprint perturbations and low-mode asymmetries makes it possible to design high-gain targets. Designs using polar-drive illumination are developed within the NIF laser system specifications. Mid-Z ablator targets are an attractive candidate for direct-drive ignition since they present better overall performance than plastic ablator targets through reduced laser–plasma instabilities and a similar hydrodynamic stability.

  5. Modified areal cartography in auditory cortex following early- and late-onset deafness.

    PubMed

    Wong, Carmen; Chabot, Nicole; Kok, Melanie A; Lomber, Stephen G

    2014-07-01

    Cross-modal plasticity following peripheral sensory loss enables deprived cortex to provide enhanced abilities in remaining sensory systems. These functional adaptations have been demonstrated in cat auditory cortex following early-onset deafness in electrophysiological and psychophysical studies. However, little information is available concerning any accompanying structural compensations. To examine the influence of sound experience on areal cartography, auditory cytoarchitecture was examined in hearing cats, early-deaf cats, and cats with late-onset deafness. Cats were deafened shortly after hearing onset or in adulthood. Cerebral cytoarchitecture was revealed immunohistochemically using SMI-32, a monoclonal antibody used to distinguish auditory areas in many species. Auditory areas were delineated in coronal sections and their volumes measured. Staining profiles observed in hearing cats were conserved in early- and late-deaf cats. In all deaf cats, dorsal auditory areas were the most mutable. Early-deaf cats showed further modifications, with significant expansions in second auditory cortex and ventral auditory field. Borders between dorsal auditory areas and adjacent visual and somatosensory areas were shifted ventrally, suggesting expanded visual and somatosensory cortical representation. Overall, this study shows the influence of acoustic experience in cortical development, and suggests that the age of auditory deprivation may significantly affect auditory areal cartography.

  6. Evaluation of CAMEL - comprehensive areal model of earthquake-induced landslides

    USGS Publications Warehouse

    Miles, S.B.; Keefer, D.K.

    2009-01-01

    A new comprehensive areal model of earthquake-induced landslides (CAMEL) has been developed to assist in planning decisions related to disaster risk reduction. CAMEL provides an integrated framework for modeling all types of earthquake-induced landslides using fuzzy logic systems and geographic information systems. CAMEL is designed to facilitate quantitative and qualitative representation of terrain conditions and knowledge about these conditions on the likely areal concentration of each landslide type. CAMEL has been empirically evaluated with respect to disrupted landslides (Category I) using a case study of the 1989 M = 6.9 Loma Prieta, CA earthquake. In this case, CAMEL performs best in comparison to disrupted slides and falls in soil. For disrupted rock fall and slides, CAMEL's performance was slightly poorer. The model predicted a low occurrence of rock avalanches, when none in fact occurred. A similar comparison with the Loma Prieta case study was also conducted using a simplified Newmark displacement model. The area under the curve method of evaluation was used in order to draw comparisons between both models, revealing improved performance with CAMEL. CAMEL should not however be viewed as a strict alternative to Newmark displacement models. CAMEL can be used to integrate Newmark displacements with other, previously incompatible, types of knowledge. ?? 2008 Elsevier B.V.

  7. Electrospun titania-based fibers for high areal capacity Li-ion battery anodes

    NASA Astrophysics Data System (ADS)

    Self, Ethan C.; Wycisk, Ryszard; Pintauro, Peter N.

    2015-05-01

    Electrospinning is utilized to prepare composite fiber Li-ion battery anodes containing titania and carbon nanoparticles with a poly (acrylic acid) binder. The electrospun material exhibits a stable charge/discharge capacity with only 5% capacity fade over 450 cycles at 0.5 C. Compared to a conventional slurry cast electrode of the same composition, the electrospun anode demonstrates 4-fold higher capacity retention (31% vs. 7.9%) at a charge/discharge rate of 5 C. Electrospinning is also used to prepare ultrathick anodes (>1 mm) with areal capacities up to 3.9 mAh cm-2. Notably, the thick electrodes exhibit areal capacities of 2.5 and 1.3 mAh cm-2 at 1 C and 2 C, respectively. Electrospun anodes with densely packed fibers have a 2 C volumetric capacity which exceeds that of the slurry cast material (21.2 and 17.5 mAh cm-3, respectively). The excellent performance of the electrospun anodes is attributed to interfiber voids which provide complete electrolyte intrusion, a large electrode/electrolyte interface, and short Li+ transport pathways between the electrolyte and titania nanoparticles.

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

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    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.

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

    SciTech Connect

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

    2014-09-15

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

  10. A modified method for accurate correlation between the craze density and the optomechanical properties of fibers using Pluta microscope.

    PubMed

    Sokkar, T Z N; El-Farahaty, K A; El-Bakary, M A; Omar, E Z; Hamza, A A

    2016-05-01

    A modified method was suggested to improve the performance of the Pluta microscope in its nonduplicated mode in the calculation of the areal craze density especially, for relatively low draw ratio (low areal craze density). This method decreases the error that is resulted from the similarity between the formed crazes and the dark fringes of the interference pattern. Furthermore, an accurate method to calculate the birefringence and the orientation function of the drawn fibers via nonduplicated Pluta polarizing interference microscope for high areal craze density (high draw ratio) was suggested. The advantage of the suggested method is to relate the optomechanical properties of the tested fiber with the areal craze density, for the same region of the fiber material.

  11. Monochromatic x-ray radiography for areal-density measurement of inertial fusion energy fuel in fast ignition experiment.

    PubMed

    Fujioka, Shinsuke; Fujiwara, Takashi; Tanabe, Minoru; Nishimura, Hiroaki; Nagatomo, Hideo; Ohira, Shinji; Inubushi, Yuichi; Shiraga, Hiroyuki; Azechi, Hiroshi

    2010-10-01

    Ultrafast, two-dimensional x-ray imaging is an important diagnostics for the inertial fusion energy research, especially in investigating implosion dynamics at the final stage of the fuel compression. Although x-ray radiography was applied to observing the implosion dynamics, intense x-rays emitted from the high temperature and dense fuel core itself are often superimposed on the radiograph. This problem can be solved by coupling the x-ray radiography with monochromatic x-ray imaging technique. In the experiment, 2.8 or 5.2 keV backlight x-rays emitted from laser-irradiated polyvinyl chloride or vanadium foils were selectively imaged by spherically bent quartz crystals with discriminating the out-of-band emission from the fuel core. This x-ray radiography system achieved 24 μm and 100 ps of spatial and temporal resolutions, respectively.

  12. Monochromatic x-ray radiography for areal-density measurement of inertial fusion energy fuel in fast ignition experiment

    SciTech Connect

    Fujioka, Shinsuke; Fujiwara, Takashi; Tanabe, Minoru; Nishimura, Hiroaki; Nagatomo, Hideo; Ohira, Shinji; Shiraga, Hiroyuki; Azechi, Hiroshi; Inubushi, Yuichi

    2010-10-15

    Ultrafast, two-dimensional x-ray imaging is an important diagnostics for the inertial fusion energy research, especially in investigating implosion dynamics at the final stage of the fuel compression. Although x-ray radiography was applied to observing the implosion dynamics, intense x-rays emitted from the high temperature and dense fuel core itself are often superimposed on the radiograph. This problem can be solved by coupling the x-ray radiography with monochromatic x-ray imaging technique. In the experiment, 2.8 or 5.2 keV backlight x-rays emitted from laser-irradiated polyvinyl chloride or vanadium foils were selectively imaged by spherically bent quartz crystals with discriminating the out-of-band emission from the fuel core. This x-ray radiography system achieved 24 {mu}m and 100 ps of spatial and temporal resolutions, respectively.

  13. Combined Effects of Spaceflight and Age in Astronauts as Assessed by Areal Bone Mineral Density [BMD] and Trabecular Bone Score

    NASA Technical Reports Server (NTRS)

    Sibonga, Jean D.; Spector, Elizabeth R.; Ploutz-Snyder, R.; Evans, H. J.; King, L.; Watts, N. B.; Hans, D.; Smith, S. A.

    2013-01-01

    Spaceflight is a potential risk factor for secondary osteoporosis in astronauts. Although lumbar spine (LS) BMD declines rapidly, more than expected for age, there have been no fragility fractures in astronauts that can clearly be attributed to spaceflight. Recently, astronauts have been returning from 6-month spaceflights with absolute BMD still above young adult mean BMD. In spite of these BMD measurements, we project that the rapid loss in bone mass over long-duration spaceflight affects the bone microarchitecture of the LS which might predispose astronauts to premature vertebral fractures. Thus, we evaluated TBS, a novel texture index correlated with vertebral bone microarchitecture, as a means of monitoring changes to bone microarchitecture in astronauts as they age. We previously reported that TBS detects an effect of spaceflight (6-month duration), independent of BMD, in 51 astronauts (47+/-4 y) (Smith et al, J Clin Densitometry 2014). Hence, TBS was evaluated in serial DXA scans (Hologic Discovery W) conducted triennially in all active and retired astronauts and more frequently (before spaceflight, after spaceflight and until recovery) in the subset of astronauts flying 4-6- month missions. We used non-linear models to describe trends in observations (BMD or TBS) plotted as a function of astronaut age. We fitted 1175 observations of 311 astronauts, pre-flight and then postflight starting 3 years after landing or after astronaut's BMD for LS was restored to within 2% of preflight BMD. Observations were then grouped and defined as follows: 1) LD: after exposure to at least one long-duration spaceflight > 100 days and 2) SD: before LD and after exposure to at least one short-duration spaceflight < 30 days. Data from males and females were analyzed separately. Models of SD observations revealed that TBS and BMD had similar curvilinear declines with age for both male and female astronauts. However, models of LD observations showed TBS declining with age while BMD appeared stable or trending upward. For females (n=8) LD observations were too few to discern a trend. Notably, models describing trends in TBS appeared to be more sensitive to the effects of age than the models for BMD. We conclude that TBS may provide an additional index for the lumbar spine to monitor the combined changes due to spaceflight and due to aging. This increased knowledge may enhance the ability to identify an intervention trigger for premature vertebral fractures in astronauts.

  14. Modeling of beam-target interaction during pulsed electron beam ablation of graphite: Case of melting

    NASA Astrophysics Data System (ADS)

    Ali, Muddassir; Henda, Redhouane

    2017-02-01

    A one-dimensional thermal model based on a two-stage heat conduction equation is employed to investigate the ablation of graphite target during nanosecond pulsed electron beam ablation. This comprehensive model accounts for the complex physical phenomena comprised of target heating, melting and vaporization upon irradiation with a polyenergetic electron beam. Melting and vaporization effects induced during ablation are taken into account by introducing moving phase boundaries. Phase transition induced during ablation is considered through the temperature dependent thermodynamic properties of graphite. The effect of electron beam efficiency, power density, and accelerating voltage on ablation is analyzed. For an electron beam operating at an accelerating voltage of 15 kV and efficiency of 0.6, the model findings show that the target surface temperature can reach up to 7500 K at the end of the pulse. The surface begins to melt within 25 ns from the pulse start. For the same process conditions, the estimated ablation depth and ablated mass per unit area are about 0.60 μm and 1.05 μg/mm2, respectively. Model results indicate that ablation takes place primarily in the regime of normal vaporization from the surface. The results obtained at an accelerating voltage of 15 kV and efficiency factor of 0.6 are satisfactorily in good accordance with available experimental data in the literature.

  15. Femtosecond laser ablation of enamel

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  16. Fragmentation and ablation during entry

    SciTech Connect

    Canavan, G.H.

    1997-09-01

    This note discusses objects that both fragment and ablate during entry, using the results of previous reports to describe the velocity, pressure, and fragmentation of entering objects. It shows that the mechanisms used there to describe the breakup of non-ablating objects during deceleration remain valid for most ablating objects. It treats coupled fragmentation and ablation during entry, building on earlier models that separately discuss the entry of objects that are hard, whose high heat of ablation permits little erosion, and those who are strong whose strength prevents fragmentation, which are discussed in ``Radiation from Hard Objects,`` ``Deceleration and Radiation of Strong, Hard, Asteroids During Atmospheric Impact,`` and ``Meteor Signature Interpretation.`` This note provides a more detailed treatment of the further breakup and separation of fragments during descent. It replaces the constraint on mass per unit area used earlier to determine the altitude and magnitude of peak power radiation with a detailed analytic solution of deceleration. Model predictions are shown to be in agreement with the key features of numerical calculations of deceleration. The model equations are solved for the altitudes of maximum radiation, which agree with numerical integrations. The model is inverted analytically to infer object size and speed from measurements of peak power and altitude to provide a complete model for the approximate inversion of meteor data.

  17. Thermal ablation of lung tumors.

    PubMed

    McTaggart, Ryan A; Dupuy, Damian E

    2007-06-01

    Thermal ablation can be applied to treat any thoracic malignancy: primary lung cancers, recurrent primary lung cancers, metastatic disease, chest wall masses, and painful, bony metastases. Since the first reported use of thermal ablation for lung cancer in 2000 there has been an explosive use of the procedure, and by 2010 the number of procedures to treat thoracic malignancy is expected to exceed 150,000 per year. Presently, thermal ablation is best used for patients with early-stage lung cancers in patients who are not surgical candidates, patients with small and favorably located pulmonary metastases, and patients in whom palliation of tumor-related symptoms is the goal. Radiofrequency ablation, microwave ablation, and cryoablation are novel treatment modalities for lung cancer and can safely accomplish tumor destruction and even complete eradication of tumor in patients who are not candidates for surgical resection. In this article, we discuss technical considerations for each modality and the periprocedure and postprocedure management of patients with this disease.

  18. Diagnostic characterization of ablation plasma ion implantation

    NASA Astrophysics Data System (ADS)

    Qi, B.; Gilgenbach, R. M.; Jones, M. C.; Johnston, M. D.; Lau, Y. Y.; Wang, L. M.; Lian, J.; Doll, G. L.; Lazarides, A.

    2003-06-01

    Experiments are reported in which two configurations for ablation-plasma-ion-implantation (APII) are characterized by diagnostics and compared. The first configuration oriented the target parallel to the deposition substrate. This orientation yielded ion-beam-assisted deposition of thin films. A delay (>5 μs) between laser and high voltage was necessary for this geometry to avoid arcing between negatively biased substrate and target. The second experimental configuration oriented the target perpendicular to the deposition substrate, reducing arcing, even for zero/negative delay between the laser and the high voltage pulse. This orientation also reduced neutral atom, ballistic deposition on the substrate resulting in a pure ion implantation mode. Ion density measurements were made by resonant laser diagnostics and Langmuir probes, yielding total ion populations in the range of 1014. Implanted ion doses were estimated by electrical diagnostics, and materials analysis, including x-ray energy dispersive spectroscopy and x-ray photoelectron spectroscopy, yielding implanted doses in the range 1012 ions/cm2 per pulse. This yields an APII efficiency of order 10% for implantation of laser ablated ions. Scaling of ion dose with voltage agrees well with a theory assuming the Child-Langmuir law and that the ion current at the sheath edge is due to the uncovering of the ions by the movement of the sheath. Thin film analysis showed excellent adhesion with smoother films for an accelerating voltage of -3.2 kV; higher voltages (-7.7 kV) roughened the film.

  19. Measuring and comparing brain cortical surface area and other areal quantities

    PubMed Central

    Winkler, Anderson M.; Sabuncu, Mert R.; Yeo, B.T. Thomas; Fischl, Bruce; Greve, Douglas N.; Kochunov, Peter; Nichols, Thomas E.; Blangero, John; Glahn, David C.

    2012-01-01

    Structural analysis of MRI data on the cortical surface usually focuses on cortical thickness. Cortical surface area, when considered, has been measured only over gross regions or approached indirectly via comparisons with a standard brain. Here we demonstrate that direct measurement and comparison of the surface area of the cerebral cortex at a fine scale is possible using mass conservative interpolation methods. We present a framework for analyses of the cortical surface area, as well as for any other measurement distributed across the cortex that is areal by nature. The method consists of the construction of a mesh representation of the ortex, registration to a common coordinate system and, crucially, interpolation using a pycnophylactic method. Statistical analysis of surface area is done with power-transformed data to address lognormality, and inference is done with permutation methods. We introduce the concept of facewise analysis, discuss its interpretation and potential applications. PMID:22446492

  20. Geodetic constraints on areal changes in the Pacific-North America plate boundary zone: What controls Basin and Range extension?

    NASA Astrophysics Data System (ADS)

    Kreemer, Corné; Hammond, William C.

    2007-10-01

    Using ˜1500 geodetic velocities we model the present-day spatial patterns of areal changes inside the Pacific-North America plate boundary zone. From this model we show that between the central Gulf of California and the Queen Charlotte Islands there is no significant net change in surface area. This zero net areal-change result allows us to relate regions of areal growth to areas of equivalent contraction elsewhere within the plate boundary zone. We find that areal growth of the Basin and Range province (BRP) and its eastern margin (˜5.2 ± 0.1 × 103 m2/yr) is balanced by areal reduction near northwestern California between 38°N and 42°N. The San Andreas fault system south of 38°N and the plate boundary zone north of ˜42°N (including the Juan de Fuca and Gorda Ridge systems) each have no significant net areal change. Our results suggest a kinematic relationship between extension in the BRP and contraction near the northern California Coast Ranges and Klamath Mountains. From these observations we propose that, although BRP extension may be caused by internal forces, the southernmost Cascadia subduction zone provides a “window of escape” that acts as a stress guide to BRP extension as well as northwestward Sierra Nevada motion. Such a dynamic model is consistent with independent findings that (1) the least principal horizontal stress orientations in the BRP are toward northern California, (2) extension directions in the BRP have changed orientation to track the northward migration of the Mendocino triple junction, and (3) the southernmost Cascadia subduction zone is a relatively weak plate boundary.

  1. Theoretical Modeling for Hepatic Microwave Ablation

    PubMed Central

    Prakash, Punit

    2010-01-01

    Thermal tissue ablation is an interventional procedure increasingly being used for treatment of diverse medical conditions. Microwave ablation is emerging as an attractive modality for thermal therapy of large soft tissue targets in short periods of time, making it particularly suitable for ablation of hepatic and other tumors. Theoretical models of the ablation process are a powerful tool for predicting the temperature profile in tissue and resultant tissue damage created by ablation devices. These models play an important role in the design and optimization of devices for microwave tissue ablation. Furthermore, they are a useful tool for exploring and planning treatment delivery strategies. This review describes the status of theoretical models developed for microwave tissue ablation. It also reviews current challenges, research trends and progress towards development of accurate models for high temperature microwave tissue ablation. PMID:20309393

  2. Image-guided ablation of adrenal lesions.

    PubMed

    Yamakado, Koichiro

    2014-06-01

    Although laparoscopic adrenalectomy has remained the standard of care for the treatment for adrenal tumors, percutaneous image-guided ablation therapy, such as chemical ablation, radiofrequency ablation, cryoablation, and microwave ablation, has been shown to be clinically useful in many nonsurgical candidates. Ablation therapy has been used to treat both functioning adenomas and malignant tumors, including primary adrenal carcinoma and metastasis. For patients with functioning adenomas, biochemical and symptomatic improvement is achieved in 96 to 100% after ablation; for patients with malignant adrenal neoplasms, however, the survival benefit from ablation therapy remains unclear, though good initial results have been reported. This article outlines the current role of ablation therapy for adrenal lesions, as well as identifying some of the technical considerations for this procedure.

  3. Microwave ablation of hepatocellular carcinoma

    PubMed Central

    Poggi, Guido; Tosoratti, Nevio; Montagna, Benedetta; Picchi, Chiara

    2015-01-01

    Although surgical resection is still the optimal treatment option for early-stage hepatocellular carcinoma (HCC) in patients with well compensated cirrhosis, thermal ablation techniques provide a valid non-surgical treatment alternative, thanks to their minimal invasiveness, excellent tolerability and safety profile, proven efficacy in local disease control, virtually unlimited repeatability and cost-effectiveness. Different energy sources are currently employed in clinics as physical agents for percutaneous or intra-surgical thermal ablation of HCC nodules. Among them, radiofrequency (RF) currents are the most used, while microwave ablations (MWA) are becoming increasingly popular. Starting from the 90s’, RF ablation (RFA) rapidly became the standard of care in ablation, especially in the treatment of small HCC nodules; however, RFA exhibits substantial performance limitations in the treatment of large lesions and/or tumors located near major heat sinks. MWA, first introduced in the Far Eastern clinical practice in the 80s’, showing promising results but also severe limitations in the controllability of the emitted field and in the high amount of power employed for the ablation of large tumors, resulting in a poor coagulative performance and a relatively high complication rate, nowadays shows better results both in terms of treatment controllability and of overall coagulative performance, thanks to the improvement of technology. In this review we provide an extensive and detailed overview of the key physical and technical aspects of MWA and of the currently available systems, and we want to discuss the most relevant published data on MWA treatments of HCC nodules in regard to clinical results and to the type and rate of complications, both in absolute terms and in comparison with RFA. PMID:26557950

  4. Surgical Ablation of Atrial Fibrillation.

    PubMed

    Ramlawi, Basel; Abu Saleh, Walid K

    2015-01-01

    The Cox-maze procedure for the restoration of normal sinus rhythm, initially developed by Dr. James Cox, underwent several iterations over the years. The main concept consists of creating a series of transmural lesions in the right and left atria that disrupt re-entrant circuits responsible for propagating the abnormal atrial fibrillation rhythm. The left atrial appendage is excluded as a component of the Maze procedure. For the first three iterations of the Cox- maze procedure, these lesions were performed using a surgical cut-and-sew approach that ensured transmurality. The Cox-Maze IV is the most currently accepted iteration. It achieves the same lesion set of the Cox- maze III but uses alternative energy sources to create the transmural lesions, potentially in a minimally invasive approach on the beating heart. High-frequency ultrasound, microwave, and laser energy have all been used with varying success in the past. Today, bipolar radiofrequency heat or cryotherapy cooling are the most accepted sources for creating linear lesions with consistent safety and transmurality. The robust and reliable nature of these energy delivery methods has yielded a success rate reaching 90% freedom from atrial fibrillation at 12 months. Such approaches offer a significant long-term advantage over catheter-based ablation, especially in patients having longstanding, persistent atrial fibrillation with characteristics such as dilated left atrial dimensions, poor ejection fraction, and failed catheter ablation. Based on these improved results, there currently is significant interest in developing a hybrid ablation strategy that incorporates the superior transmural robust lesions of surgical ablation, the reliable stroke prevention potential of epicardial left atrial appendage exclusion, and sophisticated mapping and confirmatory catheter-based ablation technology. Such a minimally invasive hybrid strategy for ablation may lead to the development of multidisciplinary "Afib teams" to

  5. Laser ablation based fuel ignition

    DOEpatents

    Early, James W.; Lester, Charles S.

    1998-01-01

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

  6. Laser ablation based fuel ignition

    DOEpatents

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

    1998-06-23

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

  7. Transhemangioma Ablation of Hepatocellular Carcinoma

    SciTech Connect

    Pua, Uei

    2012-12-15

    Radiofrequency ablation (RFA) is a well-established treatment modality in the treatment of early hepatocellular carcinoma (HCC) [1]. Safe trajectory of the RFA probe is crucial in decreasing collateral tissue damage and unwarranted probe transgression. As a percutaneous technique, however, the trajectory of the needle is sometimes constrained by the available imaging plane. The presence of a hemangioma beside an HCC is uncommon but poses the question of safety related to probe transgression. We hereby describe a case of transhemangioma ablation of a dome HCC.

  8. Fractional ablative laser skin resurfacing: a review.

    PubMed

    Tajirian, Ani L; Tarijian, Ani L; Goldberg, David J

    2011-12-01

    Ablative laser technology has been in use for many years now. The large side effect profile however has limited its use. Fractional ablative technology is a newer development which combines a lesser side effect profile along with similar efficacy. In this paper we review fractional ablative laser skin resurfacing.

  9. Spectroscopic characterization of laser ablation brass plasma

    NASA Astrophysics Data System (ADS)

    Shaikh, Nek M.; Hafeez, Sarwat; Kalyar, M. A.; Ali, R.; Baig, M. A.

    2008-11-01

    We present optical emission studies of the laser ablation brass plasma generated by the fundamental, second, and third harmonics of a neodymium doped yttrium aluminum garnet laser. The spectra predominantly reveal the spectral lines of the neutral and singly ionized copper and zinc. The excitation temperatures are determined by the Boltzmann plot method, whereas the electron number densities have been extracted from the Stark broadened line profiles. The spatial variations in the spectral line intensities and the plasma parameters at 1000, 500, and 100 mbar air pressures have been evaluated. Besides, the effect of the ambient gases (He, Ne, and Ar), the laser irradiance, and the laser wavelengths on the plasma parameters have been investigated.

  10. Cyanate Ester and Phthalonitrile Impregnated Carbon Ablative TPS

    NASA Technical Reports Server (NTRS)

    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. Leonid meteor ablation, energy exchange and trail morphology

    SciTech Connect

    Zinn, John; Judd, O'Dean P.; ReVelle, D. O.

    2002-01-01

    This paper describes theoretical model studies of the interaction of Leonid meteoroids with the earth's atmosphere. Subject to some modest-to-strenuous approximations we compute the rates of ablation and deceleration, energy deposition, and terminal altitudes of the meteors as functions of their initial mass and bulk density, velocity, trajectory entry angle, drag coefficient, heat of ablation, and an ablation energy transfer fraction. We find that the dominant energy deposition in the atmosphere is associated with the stopping of the ablated meteor particles and vapor by the surrounding air. Then having computed the energy deposition rates versus altitude we compute the hydrodynamic and radiative expansion of the hot wake material in the radial direction, along with the associated air chemistry. From the computed results we can then plot two-dimensional temperature contours -- as functions of the instantaneous distance behind the meteor and radial distance from the center of the wake, at various altitudes along the meteor's path. We also compute the rates of emission of radiation and the radiative efficiency, and discuss comparisons with observations.

  12. Modern Advances in Ablative TPS

    NASA Technical Reports Server (NTRS)

    Venkatapathy, Ethiraj

    2013-01-01

    Topics covered include: Physics of Hypersonic Flow and TPS Considerations. Destinations, Missions and Requirements. State of the Art Thermal Protection Systems Capabilities. Modern Advances in Ablative TPS. Entry Systems Concepts. Flexible TPS for Hypersonic Inflatable Aerodynamic Decelerators. Conformal TPS for Rigid Aeroshell. 3-D Woven TPS for Extreme Entry Environment. Multi-functional Carbon Fabric for Mechanically Deployable.

  13. Sketch maps showing areal extent, thickness and amount of commercial-quality peat in deposits of southern and western Maine

    USGS Publications Warehouse

    Cameron, C.C.; Mullen, M.K.

    1982-01-01

    Peat deposits in southern and western Maine were investigated for their estimated potential as peat resources suitable for energy, horticultural, and agricultural uses. Fifty-six sketch maps illustrate the areal extent, thickness, and amount of commercial-quality peat. The total yield is estimated at 27,736,400 short tons air-dried peat.

  14. Projections of changes of areal evapotranspiration for different land-use units in the Wielkopolska Region (Poland)

    NASA Astrophysics Data System (ADS)

    Szwed, Małgorzata

    2016-08-01

    Strong global warming has been observed in the last three decades. Central Europe, including Poland, is not an exception. Moreover, climate projections for Poland foresee further warming as well as changes in the quantity as well as spatial and seasonal distribution of precipitation. This will result in changes in all elements of the water balance, including the areal evapotranspiration. For estimating the areal evapotranspiration, the heat balance method (HBM) is used in this paper for the growing season (March-October), whereas for the remaining months (November-February), evaporation is calculated according to the Ivanov equation. Values of areal evapotranspiration from selected land units are examined and compared for the average conditions in two time horizons, i.e. 1961-1990 (control period) and 2061-2090 (projection horizon) over the Wielkopolska Region in Poland, based on multi-model ensemble climate projections. Projections for the future, based on the MPI-M-REMO model, indicate that the regional average increases of the annual sum of areal evapotranspiration (connected mainly with an increase of air temperature) is equal to 45 mm, with the biggest changes during winter. In the growing season, the highest increases are expected to appear in July and June. As regards the spatial distribution, the highest increases are projected for the areas with presently highest evapotranspiration, e.g. the southwestern parts of the region.

  15. Esophageal papilloma: Flexible endoscopic ablation by radiofrequency

    PubMed Central

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

    2015-01-01

    Squamous papilloma of the esophagus is a rare benign lesion of the esophagus. Radiofrequency ablation is an established endoscopic technique for the eradication of Barrett esophagus. No cases of endoscopic ablation of esophageal papilloma by radiofrequency ablation (RFA) have been reported. We report a case of esophageal papilloma successfully treated with a single session of radiofrequency ablation. Endoscopic ablation of the lesion was achieved by radiofrequency using a new catheter inserted through the working channel of endoscope. The esophageal ablated tissue was removed by a specifically designed cup. Complete ablation was confirmed at 3 mo by endoscopy with biopsies. This case supports feasibility and safety of as a new potential indication for BarrxTM RFA in patients with esophageal papilloma. PMID:25789102

  16. Percutaneous ablation of benign bone tumors.

    PubMed

    Welch, Brian T; Welch, Timothy J

    2011-09-01

    Percutaneous image-guided ablation has become a standard of practice and one of the primary modalities for treatment of benign bone tumors. Ablation is most commonly used to treat osteoid osteomas but may also be used in the treatment of chondroblastomas, osteoblastomas, and giant cell tumors. Percutaneous image-guided ablation of benign bone tumors carries a high success rate (>90% in case series) and results in decreased morbidity, mortality, and expense compared with traditional surgical methods. The ablation technique most often applied to benign bone lesions is radiofrequency ablation. Because the ablation technique has been extensively applied to osteoid osteomas and because of the uncommon nature of other benign bone tumors, we will primarily focus this discussion on the percutaneous ablation of osteoid osteomas.

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

    NASA Astrophysics Data System (ADS)

    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.

  18. Percutaneous Irreversible Electroporation Lung Ablation: Preliminary Results in a Porcine Model

    SciTech Connect

    Deodhar, Ajita; Monette, Sebastien; Single, Gordon W.; Hamilton, William C.; Thornton, Raymond H.; Sofocleous, Constantinos T.; Maybody, Majid; Solomon, Stephen B.

    2011-12-15

    Objective: Irreversible electroporation (IRE) uses direct electrical pulses to create permanent 'pores' in cell membranes to cause cell death. In contrast to conventional modalities, IRE has a nonthermal mechanism of action. Our objective was to study the histopathological and imaging features of IRE in normal swine lung. Materials and Methods: Eleven female swine were studied for hyperacute (8 h), acute (24 h), subacute (96 h), and chronic (3 week) effects of IRE ablation in lung. Paired unipolar IRE applicators were placed under computed tomography (CT) guidance. Some applicators were deliberately positioned near bronchovascular structures. IRE pulse delivery was synchronized with the cardiac rhythm only when ablation was performed within 2 cm of the heart. Contrast-enhanced CT scan was performed immediately before and after IRE and at 1 and 3 weeks after IRE ablation. Representative tissue was stained with hematoxylin and eosin for histopathology. Results: Twenty-five ablations were created: ten hyperacute, four acute, and three subacute ablations showed alveolar edema and necrosis with necrosis of bronchial, bronchiolar, and vascular epithelium. Bronchovascular architecture was maintained. Chronic ablations showed bronchiolitis obliterans and alveolar interstitial fibrosis. Immediate post-procedure CT images showed linear or patchy density along the applicator tract. At 1 week, there was consolidation that resolved partially or completely by 3 weeks. Pneumothorax requiring chest tube developed in two animals; no significant cardiac arrhythmias were noted. Conclusion: Our preliminary porcine study demonstrates the nonthermal and extracellular matrix sparing mechanism of action of IRE. IRE is a potential alternative to thermal ablative modalities.

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

    SciTech Connect

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

    2011-03-15

    X-ray ablation rates have been measured in beryllium, copper-doped beryllium, germanium-doped plastic (Ge-doped CH), and diamondlike high density carbon (HDC) for radiation temperatures T in the range of 160-260 eV. In beryllium, the measured ablation rates range from 3 to 12 mg/cm{sup 2}/ns; in Ge-doped CH, the ablation rates range from 2 to 6 mg/cm{sup 2}/ns; and for HDC, the rates range from 2 to 9 mg/cm{sup 2}/ns. The ablation rates follow an approximate T{sup 3} dependence and, for T below 230 eV, the beryllium ablation rates are significantly higher than HDC and Ge-doped CH. The corresponding implied ablation pressures are in the range of 20-160 Mbar, scaling as T{sup 3.5}. The results are found to be well predicted by computational simulations using the physics packages and computational techniques employed in the design of indirect-drive inertial confinement fusion capsules. An iterative rocket model has been developed and used to compare the ablation rate data set to spherical indirect-drive capsule implosion experiments and to confirm the validity of some aspects of proposed full-scale National Ignition Facility ignition capsule designs.

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

    SciTech Connect

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

    2012-08-15

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

  1. Laser ablated zirconium plasma: A source of neutral zirconium

    SciTech Connect

    Yadav, Dheerendra; Thareja, Raj K.

    2010-10-15

    The authors report spectroscopic investigations of laser produced zirconium (Zr) plasma at moderate laser fluence. At low laser fluence the neutral zirconium species are observed to dominate over the higher species of zirconium. Laser induced fluorescence technique is used to study the velocity distribution of ground state neutral zirconium species. Two-dimensional time-resolved density distributions of ground state zirconium is mapped using planner laser induced fluorescence imaging and total ablated mass of neutral zirconium atoms is estimated. Temporal and spatial evolutions of electron density and temperature are discussed by measuring Stark broadened profile and ratio of intensity of emission lines, respectively.

  2. Spectroscopic diagnostics for ablation cloud of tracer-encapsulated solid pellet in LHD.

    PubMed

    Tamura, N; Sergeev, V Yu; Kalinina, D V; Miroshnikov, I V; Sato, K; Sharov, I A; Bakhareva, O A; Ivanova, D M; Timokhin, V M; Sudo, S; Kuteev, B V

    2008-10-01

    In the Large Helical Device (LHD), various spectroscopic diagnostics have been applied to study the ablation process of an advanced impurity pellet, tracer-encapsulated solid pellet (TESPEL). The total light emission from the ablation cloud of TESPEL is measured by photomultipliers equipped with individual interference filters, which provide information about the TESPEL penetration depth. The spectra emitted from the TESPEL ablation cloud are measured with a 250 mm Czerny-Turner spectrometer equipped with an intensified charge coupled device detector, which is operated in the fast kinetic mode. This diagnostic allows us to evaluate the temporal evolution of the electron density in the TESPEL ablation cloud. In order to gain information about the spatial distribution of the cloud parameters, a nine image optical system that can simultaneously acquire nine images of the TESPEL ablation cloud has recently been developed. Several images of the TESPEL ablation cloud in different spectral domains will give us the spatial distribution of the TESPEL cloud density and temperature.

  3. Areal distribution of sedimentary facies determined from seismic facies analysis and models of modern depositional systems

    SciTech Connect

    Seramur, K.C.; Powell, R.D.; Carpenter, P.J.

    1988-02-01

    Seismic facies analysis was applied to 3.5-kHz single-channel analog reflection profiles of the sediment fill within Muir Inlet, Glacier Bay, southeast Alaska. Nine sedimentary facies have been interpreted from seven seismic facies identified on the profiles. The interpretations are based on reflection characteristics and structural features of the seismic facies. The following reflection characteristics and structural features are used: reflector spacing, amplitude and continuity of reflections, internal reflection configurations, attitude of reflection terminations at a facies boundary, body geometry of a facies, and the architectural associations of seismic facies within each basin. The depositional systems are reconstructed by determining the paleotopography, bedding patterns, sedimentary facies, and modes of deposition within the basin. Muir Inlet is a recently deglaciated fjord for which successive glacier terminus positions and consequent rates of glacial retreat are known. In this environment the depositional processes and sediment characteristics vary with distance from a glacier terminus, such that during a retreat a record of these variations is preserved in the aggrading sediment fill. Sedimentary facies within the basins of lower Muir Inlet are correlated with observed depositional processes near the present glacier terminus in the upper inlet. The areal distribution of sedimentary facies within the basins is interpreted using the seismic facies architecture and inferences from known sediment characteristics proximal to present glacier termini.

  4. Functional system and areal organization of a highly sampled individual human brain

    PubMed Central

    Laumann, Timothy O.; Gordon, Evan M.; Adeyemo, Babatunde; Snyder, Abraham Z.; Joo, Sung Jun; Chen, Mei-Yen; Gilmore, Adrian W.; McDermott, Kathleen B.; Nelson, Steven M.; Dosenbach, Nico U.F.; Schlaggar, Bradley L.; Mumford, Jeanette A.; Poldrack, Russell A.; Petersen, Steven E.

    2015-01-01

    Summary Resting state functional MRI has enabled description of group-level functional brain organization at multiple spatial scales. However, cross-subject averaging may obscure patterns of brain organization specific to each individual. Here, we characterized the brain organization of a single individual repeatedly measured over more than a year. We report a reproducible and internally valid subject-specific areal-level parcellation that corresponds with subject-specific task activations. Highly convergent correlation network estimates can be derived from this parcellation if sufficient data are collected – considerably more than typically acquired. Notably, within-subject correlation variability across sessions exhibited a heterogeneous distribution across the cortex concentrated in visual and somato-motor regions, distinct from the pattern of inter-subject variability. Further, although the individual's systems-level organization is broadly similar to the group, it demonstrates distinct topological features. These results provide a foundation for studies of individual differences in cortical organization and function, especially for special or rare individuals. PMID:26212711

  5. Detecting recent changes in the areal extent of North Cascades glaciers, USA

    NASA Astrophysics Data System (ADS)

    O'Neal, Michael A.; Hanson, Brian; Carisio, Sebastian; Satinsky, Ashley

    2015-09-01

    We present an exhaustive spatial analysis using the geographic, geometric, and hypsometric characteristics of 742 North Cascades glaciers to evaluate changes in their areal extents over a half-century period. Our results indicate that, contrary to our initial expectations, glacier change throughout the study region cannot be explained readily by correlations in glacier location, size, or shape. Because of the large error attributable to annual variations in glacier area due to snowpack, no statistically reliable change could be detected for 444 glaciers in our study (a slight majority). Of the North Cascades glaciers that do exhibit detectable change, a majority decreased in area, but nevertheless, some were detectably growing. These findings suggest that the integration of weather patterns over time does not neatly translate into correlations with natural variations in the geometry of glaciers. Our statistical analyses of the changes observed indicate that geometric data from a large number of glaciers, as well as a surprisingly large amount of spatial change, are required for a credible statistical detection of glacier-length and area changes over a short (multidecadal) period of time.

  6. Direct observation of feedout-related areal mass oscillations in planar plastic targets.

    NASA Astrophysics Data System (ADS)

    Aglitskiy, Y.; Metzler, N.; Velikovich, A. L.; Karasik, M.; Serlin, V.; Pawley, C.; Mostovych, A. N.; Schmitt, A. J.; Obenschain, S. P.; Gardner, J. H.

    2001-10-01

    "Feedout" means the transfer of mass perturbations from the rear to the front surface of a driven target. The oscillations are expected if the perturbation wavelength λ is not large compared to 2π L_s, where Ls is the shock-compressed target thickness. We report the first direct experimental observation of areal mass oscillation associated with feedout, followed by the onset of exponential RT growth. Our experiments were performed with the Nike KrF laser at irradiation 50 TW/cm^2. The mass redistribution in the target was observed with the aid of monochromatic x-ray imaging coupled to a streak camera. We used 40 to 60 μm thick CH targets rippled on the rear side with wavelengths of either 30 or 45 μm, the ratio 2π L_s/λ thus being close to 2. Two phase reversals of mass variation predicted by the theory and simulations were consistently observed both on the original images and on the time histories of Fourier amplitudes.

  7. Assessing Variations in Areal Organization for the Intrinsic Brain: From Fingerprints to Reliability

    PubMed Central

    Xu, Ting; Opitz, Alexander; Craddock, R. Cameron; Wright, Margaret J.; Zuo, Xi-Nian; Milham, Michael P.

    2016-01-01

    Resting state fMRI (R-fMRI) is a powerful in-vivo tool for examining the functional architecture of the human brain. Recent studies have demonstrated the ability to characterize transitions between functionally distinct cortical areas through the mapping of gradients in intrinsic functional connectivity (iFC) profiles. To date, this novel approach has primarily been applied to iFC profiles averaged across groups of individuals, or in one case, a single individual scanned multiple times. Here, we used a publically available R-fMRI dataset, in which 30 healthy participants were scanned 10 times (10 min per session), to investigate differences in full-brain transition profiles (i.e., gradient maps, edge maps) across individuals, and their reliability. 10-min R-fMRI scans were sufficient to achieve high accuracies in efforts to “fingerprint” individuals based upon full-brain transition profiles. Regarding test–retest reliability, the image-wise intraclass correlation coefficient (ICC) was moderate, and vertex-level ICC varied depending on region; larger durations of data yielded higher reliability scores universally. Initial application of gradient-based methodologies to a recently published dataset obtained from twins suggested inter-individual variation in areal profiles might have genetic and familial origins. Overall, these results illustrate the utility of gradient-based iFC approaches for studying inter-individual variation in brain function. PMID:27600846

  8. Facile Synthesis of Highly Crystalline and Large Areal Hexagonal Boron Nitride from Borazine Oligomers

    NASA Astrophysics Data System (ADS)

    Park, Sungchan; Seo, Tae Hoon; Cho, Hyunjin; Min, Kyung Hyun; Lee, Dong Su; Won, Dong-Il; Kang, Sang Ook; Kim, Myung Jong

    2017-01-01

    A novel and facile synthetic method for h-BN films from borazine oligomer (B3N3H4)x precursors has been developed. This method only includes spin-coating of borazine oligomer onto nickel catalysts and a subsequent annealing step. Large areal and highly crystalline h-BN films were obtained. The stoichiometric B/N ratio of borazine oligomer precursor was preserved in the final h-BN product such that it was close to 1 as revealed by XPS. Catalytic effect of nickel for h-BN formation was clearly demonstrated by lowering crystallization temperature compared to the growth condition in the absence of catalyst. The graphene field effect transistor (GFET) characterization has proved the high quality synthesis of h-BN films, showing the shift of neutrality point and the increase of the mobility. This method can also provide functional h-BN coating on various surfaces by annealing Ni-coated borazine oligomer films and subsequent removal of Ni catalyst.

  9. Facile Synthesis of Highly Crystalline and Large Areal Hexagonal Boron Nitride from Borazine Oligomers

    PubMed Central

    Park, Sungchan; Seo, Tae Hoon; Cho, Hyunjin; Min, Kyung Hyun; Lee, Dong Su; Won, Dong-Il; Kang, Sang Ook; Kim, Myung Jong

    2017-01-01

    A novel and facile synthetic method for h-BN films from borazine oligomer (B3N3H4)x precursors has been developed. This method only includes spin-coating of borazine oligomer onto nickel catalysts and a subsequent annealing step. Large areal and highly crystalline h-BN films were obtained. The stoichiometric B/N ratio of borazine oligomer precursor was preserved in the final h-BN product such that it was close to 1 as revealed by XPS. Catalytic effect of nickel for h-BN formation was clearly demonstrated by lowering crystallization temperature compared to the growth condition in the absence of catalyst. The graphene field effect transistor (GFET) characterization has proved the high quality synthesis of h-BN films, showing the shift of neutrality point and the increase of the mobility. This method can also provide functional h-BN coating on various surfaces by annealing Ni-coated borazine oligomer films and subsequent removal of Ni catalyst. PMID:28074854

  10. High density laser-driven target

    DOEpatents

    Lindl, John D.

    1981-01-01

    A high density target for implosion by laser energy composed of a central quantity of fuel surrounded by a high-Z pusher shell with a low-Z ablator-pusher shell spaced therefrom forming a region filled with low-density material.

  11. Growth of anatase and rutile phase TiO2 nanoparticles using pulsed laser ablation in liquid: Influence of surfactant addition and ablation time variation

    NASA Astrophysics Data System (ADS)

    Chaturvedi, Amita; Joshi, M. P.; Mondal, P.; Sinha, A. K.; Srivastava, A. K.

    2017-02-01

    Titanium dioxide (TiO2) nanoparticles were grown using nanosecond pulsed laser ablation of Ti target in DI water and in 0.001 M sodium dodecyl sulfate (SDS) surfactant aqueous solution. Growth was carried out with varying ablation times i. e. 30 min, 60 min and 90 min. The objective of our study was to investigate the influence of variations in liquid ambience conditions on the growth of the nanoparticles in a pulsed laser ablation in liquid (PLAL) process. Size, composition and optical properties of the grown TiO2 nanoparticles were investigated using transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), optical absorption, photoluminescence (PL) spectroscopy and X-ray diffraction (XRD) studies. The obtained nanoparticles of TiO2 were found almost spherical in shape and polycrystalline in nature in both the liquid mediums i.e. DI water and aqueous solution of surfactant. Nanoparticles number density was also found to increase with increasing ablation time in both the liquid mediums. However crystalline phase of the grown TiO2 nanoparticles differs with the change in liquid ambience conditions. Selected area electron diffraction (SAED), PL and XRD studies suggest that DI water ambience is favorable for the growth of anatase phase TiO2 nanoparticles for all ablation times. While Surfactant added water ambience is favorable for the growth of rutile phase TiO2 nanoparticles but for shorter ablation times of 30 min and 60 min only, for longer ablation time of 90 min anatase phase was also observed along with the rutile phase TiO2 nanoparticles. The formation of anatase phase in DI water and rutile and anatase phase in aqueous solution of surfactant is explained on the basis of varying thermodynamic conditions with the two different liquid ambiences and different ablation times.

  12. Development of lightweight ceramic ablators and arc-jet test results

    NASA Technical Reports Server (NTRS)

    Tran, Huy K.

    1994-01-01

    Lightweight ceramic ablators (LCA's) were recently developed at Ames to investigate the use of low density fibrous substrates and organic resins as high temperature, high strength ablative heat shields. Unlike the traditional ablators, LCA's use porous ceramic/carbon fiber matrices as substrates for structural support, and polymeric resins as fillers. Several substrates and resins were selected for the initial studies, and the best performing candidates were further characterized. Three arcjet tests were conducted to determine the LCA's thermal performance and ablation characteristics in a high enthalpy, hypersonic flow environment. Mass loss and recession measurements were obtained for each sample at post test, and the recession rates were determined from high speed motion films. Surface temperatures were also obtained from optical pyrometers.

  13. Characterization of tracked radiofrequency ablation in phantom

    SciTech Connect

    Chen, Chun-Cheng R.; Miga, Michael I.; Galloway, Robert L.

    2007-10-15

    In radiofrequency ablation (RFA), successful therapy requires accurate, image-guided placement of the ablation device in a location selected by a predictive treatment plan. Current planning methods rely on geometric models of ablations that are not sensitive to underlying physical processes in RFA. Implementing plans based on computational models of RFA with image-guided techniques, however, has not been well characterized. To study the use of computational models of RFA in planning needle placement, this work compared ablations performed with an optically tracked RFA device with corresponding models of the ablations. The calibration of the tracked device allowed the positions of distal features of the device, particularly the tips of the needle electrodes, to be determined to within 1.4{+-}0.6 mm of uncertainty. Ablations were then performed using the tracked device in a phantom system based on an agarose-albumin mixture. Images of the sliced phantom obtained from the ablation experiments were then compared with the predictions of a bioheat transfer model of RFA, which used the positional data of the tracked device obtained during ablation. The model was demonstrated to predict 90% of imaged pixels classified as being ablated. The discrepancies between model predictions and observations were analyzed and attributed to needle tracking inaccuracy as well as to uncertainties in model parameters. The results suggest the feasibility of using finite element modeling to plan ablations with predictable outcomes when implemented using tracked RFA.

  14. Thermochromic tissue-mimicking phantom for optimisation of thermal tumour ablation.

    PubMed

    Negussie, Ayele H; Partanen, Ari; Mikhail, Andrew S; Xu, Sheng; Abi-Jaoudeh, Nadine; Maruvada, Subha; Wood, Bradford J

    2016-05-01

    Purpose The purpose of this study was to (1) develop a novel tissue-mimicking thermochromic (TMTC) phantom that permanently changes colour from white to magenta upon heating above ablative temperatures, and (2) assess its utility for specific applications in evaluating thermal therapy devices. Materials and methods Polyacrylamide gel mixed with thermochromic ink was custom made to produce a TMTC phantom that changes its colour upon heating above biological ablative temperatures (> 60 °C). The thermal properties of the phantom were characterised, and compared to those of human tissue. In addition, utility of this phantom as a tool for the assessment of laser and microwave thermal ablation was examined. Results The mass density, thermal conductivity, and thermal diffusivity of the TMTC phantom were measured as 1033 ± 1.0 kg/m(3), 0.590 ± 0.015 W/m.K, and 0.145 ± 0.002 mm(2)/s, respectively, and found to be in agreement with reported values for human soft tissues. Heating the phantom with laser and microwave ablation devices produced clearly demarcated regions of permanent colour change geographically corresponding to regions with temperature elevations above 60 °C. Conclusion The TMTC phantom provides direct visualisation of ablation dynamics, including ablation volume and geometry as well as peak absolute temperatures within the treated region post-ablation. This phantom can be specifically tailored for different thermal therapy modalities, such as radiofrequency, laser, microwave, or therapeutic ultrasound ablation. Such modality-specific phantoms may enable better quality assurance, device characterisation, and ablation parameter optimisation, or optimise the study of dynamic heating parameters integral to drug device combination therapies relying upon heat.

  15. Surface Modification of ICF Target Capsules by Pulsed Laser Ablation

    SciTech Connect

    Carlson, Lane C.; Johnson, Michael A.; Bunn, Thomas L.

    2016-06-30

    Topographical modifications of spherical surfaces are imprinted on National Ignition Facility (NIF) target capsules by extending the capabilities of a recently developed full surface (4π) laser ablation and mapping apparatus. The laser ablation method combines the precision, energy density and long reach of a focused laser beam to pre-impose sinusoidal modulations on the outside surface of High Density Carbon (HDC) capsules and the inside surface of Glow Discharge Polymer (GDP) capsules. Sinusoidal modulations described in this paper have sub-micron to 10’s of microns vertical scale and wavelengths as small as 30 μm and as large as 200 μm. The modulated patterns are created by rastering a focused laser fired at discrete capsule surface locations for a specified number of pulses. The computer program developed to create these raster patterns uses inputs such as laser beam intensity profile, the material removal function, the starting surface figure and the desired surface figure. The patterns are optimized to minimize surface roughness. Lastly, in this paper, simulated surfaces are compared with actual ablated surfaces measured using confocal microscopy.

  16. Surface Modification of ICF Target Capsules by Pulsed Laser Ablation

    DOE PAGES

    Carlson, Lane C.; Johnson, Michael A.; Bunn, Thomas L.

    2016-06-30

    Topographical modifications of spherical surfaces are imprinted on National Ignition Facility (NIF) target capsules by extending the capabilities of a recently developed full surface (4π) laser ablation and mapping apparatus. The laser ablation method combines the precision, energy density and long reach of a focused laser beam to pre-impose sinusoidal modulations on the outside surface of High Density Carbon (HDC) capsules and the inside surface of Glow Discharge Polymer (GDP) capsules. Sinusoidal modulations described in this paper have sub-micron to 10’s of microns vertical scale and wavelengths as small as 30 μm and as large as 200 μm. The modulatedmore » patterns are created by rastering a focused laser fired at discrete capsule surface locations for a specified number of pulses. The computer program developed to create these raster patterns uses inputs such as laser beam intensity profile, the material removal function, the starting surface figure and the desired surface figure. The patterns are optimized to minimize surface roughness. Lastly, in this paper, simulated surfaces are compared with actual ablated surfaces measured using confocal microscopy.« less

  17. High areal capacity hybrid magnesium-lithium-ion battery with 99.9% Coulombic efficiency for large-scale energy storage.

    PubMed

    Yoo, Hyun Deog; Liang, Yanliang; Li, Yifei; Yao, Yan

    2015-04-01

    Hybrid magnesium-lithium-ion batteries (MLIBs) featuring dendrite-free deposition of Mg anode and Li-intercalation cathode are safe alternatives to Li-ion batteries for large-scale energy storage. Here we report for the first time the excellent stability of a high areal capacity MLIB cell and dendrite-free deposition behavior of Mg under high current density (2 mA cm(-2)). The hybrid cell showed no capacity loss for 100 cycles with Coulombic efficiency as high as 99.9%, whereas the control cell with a Li-metal anode only retained 30% of its original capacity with Coulombic efficiency well below 90%. The use of TiS2 as a cathode enabled the highest specific capacity and one of the best rate performances among reported MLIBs. Postmortem analysis of the cycled cells revealed dendrite-free Mg deposition on a Mg anode surface, while mossy Li dendrites were observed covering the Li surface and penetrated into separators in the Li cell. The energy density of a MLIB could be further improved by developing electrolytes with higher salt concentration and wider electrochemical window, leading to new opportunities for its application in large-scale energy storage.

  18. Artificial meteor ablation studies: Olivine

    NASA Technical Reports Server (NTRS)

    Blanchard, M. B.; Cunningham, G. G.

    1973-01-01

    Artificial meteor ablation was performed on a Mg-rich olivine sample using an arc-heated plasma of ionized air. Experimental conditions simulated a meteor traveling about 12 km/sec at an altitude of 70 km. The mineral content of the original olivine sample was 98% olivine (including traces of olivine alteration products) and 2% chromite. Forsterite content of the original olivine was Fo-89. After ablation, the forsterite content had increased to Fo-94 in the recrystallized olivine. In addition, lamella-like intergrowths of magnetite were prevalent constituents. Wherever magnetite occurred, there was an increase in Mg and a corresponding decrease in Fe for the recrystallized olivine. The Allende fusion crust consisted of a recrystallized olivine, which was more Mg-rich and Fe-deficient than the original meteorite's olivine, and abundant magnetite grains. Although troilite and pentlandite were the common opaque mineral constituents in this meteorite, magnetite was the principal opaque mineral found in the fusion crust.

  19. Laser Ablation for Medical Applications

    NASA Astrophysics Data System (ADS)

    Hayashi, Ken-Ichi

    Medical applications of laser are measurement, laser surgery, in-situ monitoring, and processing of medical devices. In this paper, author briefly reviews the trends of medical applications, describes some new applications, and then discuss about the future trends and problems of medical applications. At present, the domestic market of laser equipment for medical applications is nearly 1/10 of that for industrial applications, which has registered significant growth continuously. Laser surgery as a minimum invasive surgery under arthroscope is expected to decrease the pain of patients. Precise processing such as cutting and welding is suitable for manufacturing medical devices. Pulsed laser deposition has been successfully applied to the thin film coating. The corneal refractive surgery by ArF excimer laser has been widely accepted for its highly safe operation. Laser ablation for retinal implant in the visual prosthesis is one of the promising applications of laser ablation in medicine. New applications with femtosecond laser are expected in the near future.

  20. Percutaneous ablation of pancreatic cancer

    PubMed Central

    D’Onofrio, Mirko; Ciaravino, Valentina; De Robertis, Riccardo; Barbi, Emilio; Salvia, Roberto; Girelli, Roberto; Paiella, Salvatore; Gasparini, Camilla; Cardobi, Nicolò; Bassi, Claudio

    2016-01-01

    Pancreatic ductal adenocarcinoma is a highly aggressive tumor with an overall 5-year survival rate of less than 5%. Prognosis and treatment depend on whether the tumor is resectable or not, which mostly depends on how quickly the diagnosis is made. Chemotherapy and radiotherapy can be both used in cases of non-resectable pancreatic cancer. In cases of pancreatic neoplasm that is locally advanced, non-resectable, but non-metastatic, it is possible to apply percutaneous treatments that are able to induce tumor cytoreduction. The aim of this article will be to describe the multiple currently available treatment techniques (radiofrequency ablation, microwave ablation, cryoablation, and irreversible electroporation), their results, and their possible complications, with the aid of a literature review. PMID:27956791

  1. Laser Ablation Molecular Isotopic Spectrometry

    NASA Astrophysics Data System (ADS)

    Russo, Richard E.; Bol'shakov, Alexander A.; Mao, Xianglei; McKay, Christopher P.; Perry, Dale L.; Sorkhabi, Osman

    2011-02-01

    A new method of performing optical isotopic analysis of condensed samples in ambient air and at ambient pressure has been developed: Laser Ablation Molecular Isotopic Spectrometry (LAMIS). The technique uses radiative transitions from molecular species either directly vaporized from a sample or formed by associative mechanisms of atoms or ions in a laser ablation plume. This method is an advanced modification of a known atomic emission technique called laser-induced breakdown spectroscopy (LIBS). The new method — LAMIS — can determine not only chemical composition but also isotopic ratios of elements in the sample. Isotopic measurements are enabled by significantly larger isotopic shifts found in molecular spectra relative to atomic spectra. Analysis can be performed from a distance and in real time. No sample preparation or pre-treatment is required. Detection of the isotopes of hydrogen, boron, carbon, and oxygen are discussed to illustrate the technique.

  2. Percutaneous ablation of pancreatic cancer.

    PubMed

    D'Onofrio, Mirko; Ciaravino, Valentina; De Robertis, Riccardo; Barbi, Emilio; Salvia, Roberto; Girelli, Roberto; Paiella, Salvatore; Gasparini, Camilla; Cardobi, Nicolò; Bassi, Claudio

    2016-11-28

    Pancreatic ductal adenocarcinoma is a highly aggressive tumor with an overall 5-year survival rate of less than 5%. Prognosis and treatment depend on whether the tumor is resectable or not, which mostly depends on how quickly the diagnosis is made. Chemotherapy and radiotherapy can be both used in cases of non-resectable pancreatic cancer. In cases of pancreatic neoplasm that is locally advanced, non-resectable, but non-metastatic, it is possible to apply percutaneous treatments that are able to induce tumor cytoreduction. The aim of this article will be to describe the multiple currently available treatment techniques (radiofrequency ablation, microwave ablation, cryoablation, and irreversible electroporation), their results, and their possible complications, with the aid of a literature review.

  3. One-Dimensional Ablation with Pyrolysis Gas Flow Using a Full Newton's Method and Finite Control Volume Procedure

    NASA Technical Reports Server (NTRS)

    Amar, Adam J.; Blackwell, Ben F.; Edwards, Jack R.

    2007-01-01

    The development and verification of a one-dimensional material thermal response code with ablation is presented. The implicit time integrator, control volume finite element spatial discretization, and Newton's method for nonlinear iteration on the entire system of residual equations have been implemented and verified for the thermochemical ablation of internally decomposing materials. This study is a continuation of the work presented in "One-Dimensional Ablation with Pyrolysis Gas Flow Using a Full Newton's Method and Finite Control Volume Procedure" (AIAA-2006-2910), which described the derivation, implementation, and verification of the constant density solid energy equation terms and boundary conditions. The present study extends the model to decomposing materials including decomposition kinetics, pyrolysis gas flow through the porous char layer, and a mixture (solid and gas) energy equation. Verification results are presented for the thermochemical ablation of a carbon-phenolic ablator which involves the solution of the entire system of governing equations.

  4. Enhanced filament ablation of metals based on plasma grating in air

    SciTech Connect

    Wang, Di; Liu, Fengjiang; Ding, Liangen; Yuan, Shuai; Zeng, Heping

    2015-09-15

    We demonstrate efficient ablation of metals with filamentary plasma grating generated by two intense blue femtosecond filaments and a third focused infrared pulse. This scheme leads to significant promotion of ablation efficiency on metal targets in air in comparison with single infrared or blue filament with equal pulse energy. The reason is that the blue plasma grating firstly provides stronger intensity and a higher density of background electrons, then the delayed infrared pulse accelerates local electrons inside the plasma grating. These two processes finally results in robustly increased electron density and highly ionized metallic atoms.

  5. Destruction of monocrystalline silicon with nanosecond pulsed fiber laser accompanied by the oxidation of ablation microparticles

    NASA Astrophysics Data System (ADS)

    Veiko, V. P.; Skvortsov, A. M.; Huynh, C. T.; Petrov, A. A.

    2013-11-01

    In this work, we report an observation of process of local destruction monocrystalline silicon with a scanning beam irradiation of pulse ytterbium fiber laser with a wavelength λ= 1062 nm, accompanied by the oxidation of ablation microparticles. It is shown that depending on the power density of irradiation was observed a large scatter size of the microparticles. From a certain average power density is observed beginning oxidation particulate emitted from the surface of the irradiated area. By varying the parameters of the laser beam such as scanning speed, pulse repetition rate, overlap of laser spot, radiation dose can be achieved almost complete oxidation of all formed during the ablation of microparticles.

  6. The influence of ambient medium density on laser ablation processes

    SciTech Connect

    Kilgo, III, Marvin Moses

    1995-11-01

    Interest in high flux transport processes has grown in recent years along with the ability and need to manipulate systems with microscopic length and time scales. These systems present unique engineering challenges. Because the time and length scales associated with these problems are very small, assumptions of local equilibrium, physical and mathematical smoothness of boundaries and the unambiguous definition of thermodynamic fields can not be automatically made, even though they may ultimately be acceptable. Furthermore, the observations are made on macroscopic or integrated scales. The large difference in scales between the temporal evolution of the process and the observation requires careful consideration of the claims made regarding the system`s microscopic, temporal behavior. In particular, consistency of a proposed model with observed results does not guarantee uniqueness, or predictive accuracy for the model. For these reasons, microscale heat transfer systems demand a careful consideration of the framework within which the experimentation and analysis are conducted.

  7. Glass fiber addition strengthens low-density ablative compositions

    NASA Technical Reports Server (NTRS)

    Chandler, H. H.

    1974-01-01

    Approximately 15% of E-glass fibers was added to compositions under test and greatly improved char stability. Use of these fibers also reduced thermal strains which, in turn, minimized char shrinkage and associated cracks, subsurface voids, and disbonds. Increased strength allows honeycomb core reinforcement to be replaced by equivalent amount of glass fibers.

  8. Properties and behavior of diamond ablators

    NASA Astrophysics Data System (ADS)

    Fratanduono, D.; Swift, D. C.; Braun, D. G.; Prisbrey, S.; Barton, N. R.; Marinak, M.; Kraus, R.; Arsenlis, A.

    2015-06-01

    Diamond is an attractive ablator for laser loading experiments as it is efficient in converting laser energy to pressure, it transmits multi-kV x-rays such as are used for in-situ diffraction measurements, and it is readily available as single crystals, which do not produce diffraction rings that could obscure signals from a polycrystalline sample. However, radiation hydrodynamics simulations with standard models do not match the detailed velocity histories in ramp-loading experiments. Experimental measurements at the Omega laser showed that the (110) orientation exhibits much less elastic relaxation following the initial yield than did (100). Stress-density relations deduced from these experiments were consistent with the results obtained previously on thinner samples by Bradley et al., indicating that time-dependence in plastic flow had little effect on these time scales. The effect of dissipation, ignored in the characteristics analysis of ramp experiments, was assessed by analyzing simulated data, and was found to be negligible for diamond. Significant differences were found between equations of state in the several-megabar pressure regime, requiring quite different strength models to reproduce the stress-density relation. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  9. Microwave Ablation Compared to Radiofrequency Ablation for Hepatic Lesions: A Meta-Analysis.

    PubMed

    Huo, Ya Ruth; Eslick, Guy D

    2015-08-01

    To evaluate the efficacy and safety of microwave (MW) ablation compared with radiofrequency (RF) ablation for hepatic lesions by using meta-analytic techniques. Overall, 16 studies involving 2,062 patients were included. MW ablation was found to have significantly better 6-year overall survival than RF ablation (odds ratio, 1.64, 95% confidence interval, 1.15-2.35), but this was based on a few articles (n = 3 of 16). MW ablation and RF ablation had similar 1-5-year overall survival, disease-free survival, local recurrence rate, and adverse events. Based on similar safety and efficacy outcomes, either MW ablation or RF ablation may be used for effective local hepatic therapy.

  10. Tumor Thermal Ablation Enhancement by Micromaterials.

    PubMed

    Zhao, Fan; Su, Hongying; Han, Xiangjun; Bao, Han; Qi, Ji

    2016-01-07

    Thermal ablation is a minimally invasive therapeutic technique that has shown remarkable potential in treating un resectable tumors. However, clinical applications have stalled, due to safety ambiguities, slow heat induction, lengthy ablation times, and post-therapeutic monitoring issues. To further improve treatment efficacy, an assortment of micro materials (eg, nano particulates of gold, silica, or iron oxide and single-walled carbon nanotubes) are under study as thermal ablative adjuncts.In recent years, the micro material domain has become especially interesting.In vivo and in vitro animal studies have validated the use of microspheres as embolic agents in liver tumors, in advance of radiofrequency ablation. Microcapsules and micro bubbles serving as ultrasound contrast and ablation sensibilizers are strong prospects for clinical applications. This review was conducted to explore benefits of the three aforementioned micro scale technologies, in conjunction with tumor thermal ablation.

  11. Percutaneous thermal ablation of primary lung cancer.

    PubMed

    de Baere, T; Tselikas, L; Catena, V; Buy, X; Deschamps, F; Palussière, J

    2016-10-01

    Percutaneous ablation of small-size non-small-cell lung cancer (NSCLC) has demonstrated feasibility and safety in nonsurgical candidates. Radiofrequency ablation (RFA), the most commonly used technique, has an 80-90% reported rate of complete ablation, with the best results obtained in tumors less than 2-3cm in diameter. The highest one-, three-, and five-year overall survival rates reported in NSCLC following RFA are 97.7%, 72.9%, and 55.7% respectively. Tumor size, tumor stage, and underlying comorbidities are the main predictors of survival. Other ablation techniques such as microwave or cryoablation may help overcome the limitations of RFA in the future, particularly for large tumors or those close to large vessels. Stereotactic ablative radiotherapy (SABR) has its own complications and carries the risk of fiducial placement requiring multiple lung punctures. SABR has also demonstrated significant efficacy in treating small-size lung tumors and should be compared to percutaneous ablation.

  12. Image-guided ablation for hepatocellular carcinoma.

    PubMed

    Lencioni, Riccardo; Crocetti, Laura

    2013-01-01

    Image-guided ablation is accepted as the best therapeutic choice for patients with early-stage hepatocellular carcinoma (HCC) when surgical options-including resection and transplantation-are precluded. The term image-guided tumor ablation is defined as the direct application of chemical substances or sources of energy to a focal tumor in an attempt to achieve eradication or substantial tumor destruction. Over the past 25 years, several methods for local tumor destruction have been developed and clinically tested. Radiofrequency ablation (RFA) has shown superior anticancer effect and greater survival benefit with respect to the seminal percutaneous technique, ethanol injection, in meta-analyses of randomized controlled trials, and is currently established as the standard ablative modality. Nevertheless, novel thermal and nonthermal techniques for tumor ablation-including microwave ablation and irreversible electroporation-seem to have potential to improve the efficacy of RFA and are currently undergoing clinical investigation.

  13. Areal Distribution of Potential Felsic Material in Nili Patera at Syrtis Major, Mars

    NASA Astrophysics Data System (ADS)

    Eggers, G. L.; Wray, J. J.; Dufek, J.

    2015-12-01

    For decades, studies of the exposed igneous Martian crust via remote sensing and landed observation have concluded that it is predominantly basaltic. However, new analyses of meteorites and mission data indicate a wider range of primary rock composition. Nili Patera in the Syrtis Major region provides one of the best exposures of evolved compositions. Recently, Wray et al. (2013) identified a new unit in the caldera with very high feldspar abundance but unusually low mafic abundance and interpreted it as a felsic unit (as opposed to spectrally similar anorthosite) based on its proximity to a dacite unit. We investigate the summit calderas of Syrtis Major by defining and mapping distinct compositional units using mineralogies inferred from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) instrument on the Mars Reconnaissance Orbiter (MRO). The study focuses on the areal extent of potential felsic material, identified based on a broad absorption feature centered at ~1.25-1.3 μm, a unique feature of feldspars attributed to minor Fe2+ substitution. These mapping efforts are put in geologic context using images from the High Resolution Imaging Science Experiment (HiRISE) instrument on MRO and existing mapping efforts in the area, as well as spectral context using laboratory generated spectra of feldspar and mafic mixtures. While further work understanding this potential felsic unit is warranted, if it is truly felsic it implies a more complicated Martian magmatic history than previously thought. As the diversity of known geologic materials on Mars grows, it is necessary that we understand how to recognize and characterize those materials using the instruments available on current and upcoming missions, such as MRO or the Mars 2020 Rover. Through modeling and data analysis, our ongoing work seeks to understand the geophysical and petrologic context in which the potential felsic materials were generated, and thus to infer their implications for Martian

  14. Solution-grown small-molecule organic semiconductor with enhanced crystal alignment and areal coverage for organic thin film transistors

    DOE PAGES

    Bi, Sheng; He, Zhengran; Chen, Jihua; ...

    2015-07-24

    Drop casting of small-molecule organic semiconductors typically forms crystals with random orientation and poor areal coverage, which leads to significant performance variations of organic thin-film transistors (OTFTs). In this study, we utilize the controlled evaporative self-assembly (CESA) method combined with binary solvent system to control the crystal growth. A small-molecule organic semiconductor,2,5-Di-(2-ethylhexyl)-3,6-bis(5"-n-hexyl-2,2',5',2"]terthiophen-5-yl)-pyrrolo[3,4-c]pyrrole-1,4-dione (SMDPPEH), is used as an example to demonstrate the effectiveness of our approach. By optimizing the double solvent ratios, well-aligned SMDPPEH crystals with significantly improved areal coverage were achieved. As a result, the SMDPPEH based OTFTs exhibit a mobility of 1.6 × 10-2 cm2/V s, which is themore » highest mobility from SMDPPEH ever reported.« less

  15. Solution-grown small-molecule organic semiconductor with enhanced crystal alignment and areal coverage for organic thin film transistors

    SciTech Connect

    Bi, Sheng; He, Zhengran; Chen, Jihua; Li, Dawen

    2015-07-24

    Drop casting of small-molecule organic semiconductors typically forms crystals with random orientation and poor areal coverage, which leads to significant performance variations of organic thin-film transistors (OTFTs). In this study, we utilize the controlled evaporative self-assembly (CESA) method combined with binary solvent system to control the crystal growth. A small-molecule organic semiconductor,2,5-Di-(2-ethylhexyl)-3,6-bis(5"-n-hexyl-2,2',5',2"]terthiophen-5-yl)-pyrrolo[3,4-c]pyrrole-1,4-dione (SMDPPEH), is used as an example to demonstrate the effectiveness of our approach. By optimizing the double solvent ratios, well-aligned SMDPPEH crystals with significantly improved areal coverage were achieved. As a result, the SMDPPEH based OTFTs exhibit a mobility of 1.6 × 10-2 cm2/V s, which is the highest mobility from SMDPPEH ever reported.

  16. Plasma-mediated ablation of biofilm contamination

    NASA Astrophysics Data System (ADS)

    Guo, Zhixiong; Wang, Xiaoliang; Huang, Huan

    2010-12-01

    Ultra-short pulsed laser removal of thin biofilm contamination on different substrates has been conducted via the use of plasma-mediated ablation. The biofilms were formed using sheep whole blood. The ablation was generated using a 1.2 ps ultra-short pulsed laser with wavelength centered at 1552 nm. The blood contamination was transformed into plasma and collected with a vacuum system. The single line ablation features have been measured. The ablation thresholds of blood contamination and bare substrates were determined. It is found that the ablation threshold of the blood contamination is lower than those of the beneath substrates including the glass slide, PDMS, and human dermal tissues. The ablation effects of different laser parameters (pulse overlap rate and pulse energy) were studied and ablation efficiency was measured. Proper ablation parameters were found to efficiently remove contamination with maximum efficiency and without damage to the substrate surface for the current laser system. Complete removal of blood contaminant from the glass substrate surface and freeze-dried dermis tissue surface was demonstrated by the USP laser ablation with repeated area scanning. No obvious thermal damage was found in the decontaminated glass and tissue samples.

  17. Percutaneous ablation of hepatocellular carcinoma: current status.

    PubMed

    McWilliams, Justin P; Yamamoto, Shota; Raman, Steven S; Loh, Christopher T; Lee, Edward W; Liu, David M; Kee, Stephen T

    2010-08-01

    Hepatocellular carcinoma (HCC) is an increasingly common disease with dismal long-term survival. Percutaneous ablation has gained popularity as a minimally invasive, potentially curative therapy for HCC in nonoperative candidates. The seminal technique of percutaneous ethanol injection has been largely supplanted by newer modalities, including radiofrequency ablation, microwave ablation, cryoablation, and high-intensity focused ultrasound ablation. A review of these modalities, including technical success, survival rates, and complications, will be presented, as well as considerations for treatment planning and follow-up.

  18. Ablation of liver metastases: current status.

    PubMed

    Flanders, Vincent L; Gervais, Debra A

    2010-08-01

    Local ablative therapy for the treatment of metastatic disease to the liver has been evaluated most extensively in colorectal cancer with 5-year survival rates up to 55% after RF ablation. Recent findings suggest selected patients with other malignant processes may benefit as well, but conclusive evidence is limited. This article reviews the available literature regarding the use of radiofrequency ablation, microwave ablation, and cryoablation in the treatment of metastatic disease to the liver. The published results of each of these modalities in the treatment of metastatic disease to the liver are promising, and outcomes continue to be evaluated.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  20. Three-Dimensional Sulfur/Graphene Multifunctional Hybrid Sponges for Lithium-Sulfur Batteries with Large Areal Mass Loading

    NASA Astrophysics Data System (ADS)

    Lu, Songtao; Chen, Yan; Wu, Xiaohong; Wang, Zhida; Li, Yang

    2014-04-01

    In this communication, we introduce the concept of three dimensional (3D) battery electrodes to enhance the capacity per footprint area for lithium-sulfur battery. In such a battery, 3D electrode of sulfur embedded into porous graphene sponges (S-GS) was directly used as the cathode with large areal mass loading of sulfur (12 mg cm-2), approximately 6-12 times larger than that of most reports. The graphene sponges (GS) worked as a framework that can provide high electronic conductive network, abilities to absorb the polysulfides intermediate, and meanwhile mechanical support to accommodate the volume changes during charge and discharge. As a result, the S-GS electrode with 80 wt.% sulfur can deliver an extremely high areal specific capacitance of 6.0 mAh cm-2 of the 11th cycle, and maintain 4.2 mAh cm-2 after 300 charge-discharge cycles at a rate of 0.1C, representing an extremely low decay rate (0.08% per cycle after 300 cycles), which could be the highest areal specific capacity with comparable cycle stability among the rechargeable Li/S batteries reported ever.

  1. Three-dimensional sulfur/graphene multifunctional hybrid sponges for lithium-sulfur batteries with large areal mass loading.

    PubMed

    Lu, Songtao; Chen, Yan; Wu, Xiaohong; Wang, Zhida; Li, Yang

    2014-04-10

    In this communication, we introduce the concept of three dimensional (3D) battery electrodes to enhance the capacity per footprint area for lithium-sulfur battery. In such a battery, 3D electrode of sulfur embedded into porous graphene sponges (S-GS) was directly used as the cathode with large areal mass loading of sulfur (12 mg cm(-2)), approximately 6-12 times larger than that of most reports. The graphene sponges (GS) worked as a framework that can provide high electronic conductive network, abilities to absorb the polysulfides intermediate, and meanwhile mechanical support to accommodate the volume changes during charge and discharge. As a result, the S-GS electrode with 80 wt.% sulfur can deliver an extremely high areal specific capacitance of 6.0 mAh cm(-2) of the 11(th) cycle, and maintain 4.2 mAh cm(-2) after 300 charge-discharge cycles at a rate of 0.1C, representing an extremely low decay rate (0.08% per cycle after 300 cycles), which could be the highest areal specific capacity with comparable cycle stability among the rechargeable Li/S batteries reported ever.

  2. Three-Dimensional Sulfur/Graphene Multifunctional Hybrid Sponges for Lithium-Sulfur Batteries with Large Areal Mass Loading

    PubMed Central

    Lu, Songtao; Chen, Yan; Wu, Xiaohong; Wang, Zhida; Li, Yang

    2014-01-01

    In this communication, we introduce the concept of three dimensional (3D) battery electrodes to enhance the capacity per footprint area for lithium-sulfur battery. In such a battery, 3D electrode of sulfur embedded into porous graphene sponges (S-GS) was directly used as the cathode with large areal mass loading of sulfur (12 mg cm−2), approximately 6–12 times larger than that of most reports. The graphene sponges (GS) worked as a framework that can provide high electronic conductive network, abilities to absorb the polysulfides intermediate, and meanwhile mechanical support to accommodate the volume changes during charge and discharge. As a result, the S-GS electrode with 80 wt.% sulfur can deliver an extremely high areal specific capacitance of 6.0 mAh cm−2 of the 11th cycle, and maintain 4.2 mAh cm−2 after 300 charge−discharge cycles at a rate of 0.1C, representing an extremely low decay rate (0.08% per cycle after 300 cycles), which could be the highest areal specific capacity with comparable cycle stability among the rechargeable Li/S batteries reported ever. PMID:24717445

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

    NASA Astrophysics Data System (ADS)

    Wu, Po-hung; Brace, Chris L.

    2016-08-01

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

  4. Study of critical defects in ablative heat shield systems for the space shuttle

    NASA Technical Reports Server (NTRS)

    Miller, C. C.; Rummel, W. D.

    1974-01-01

    Experimental results are presented for a program conducted to determine the effects of fabrication-induced defects on the performance of an ablative heat shield material. Exposures representing a variety of space shuttle orbiter mission environments-humidity acoustics, hot vacuum and cold vacuum-culuminating in entry heating and transonic acoustics, were simulated on large panels containing intentional defects. Nondestructive methods for detecting the defects, were investigated. The baseline materials were two honeycomb-reinforced low density, silicone ablators, MG-36 and SS-41. Principal manufacturing-induced defects displaying a critical potential included: off-curing of the ablator, extreme low density, undercut (or crushed) honeycomb reinforcements, and poor wet-coating of honeycomb.

  5. Effect of excimer laser radiant exposure on uniformity of ablated corneal surface.

    PubMed

    Fantes, F E; Waring, G O

    1989-01-01

    The argon fluoride (193 nm) excimer laser is being used to change the anterior corneal curvature for correction of refractive errors. Uniformity of the surface following laser ablation may play an important role in the rate of epithelial healing and amount and type of stromal scarring. To test the effect of radiant exposure (fluence) on surface smoothness, we ablated rabbit corneas with the 193 nm argon fluoride excimer laser at nine radiant exposures from 50 to 850 mJ/cm2. A total energy of 100 J/cm2 was used for each ablation at a frequency of 1 Hz. Scanning electron microscopy demonstrated progressive improvement of surface smoothness with increasing radiant exposures. Transmission electron microscopy demonstrated no consistent increase in thickness to the surface condensate (pseudomembrane) with increasing radiant exposure. Improvement in surface quality associated with increasing radiant exposures may result from a more uniform depth of ablation per pulse in the corneal lamellae that absorb laser wavelengths differently. Radiant exposures at levels where the depth of ablation is the same regardless of increasing energy densities achieve a more uniform surface because inhomogeneities in the beam and variation in energy from pulse to pulse do not affect the ablation rate.

  6. Laser Navigation for Radiofrequency Ablation

    SciTech Connect

    Varro, Zoltan; Locklin, Julia K. Wood, Bradford J.

    2004-09-15

    A 45-year-old male with renal cell carcinoma secondary to von-Hippel Lindau (VHL) disease presented for radiofrequency ablation (RFA) of kidney tumors. Due to his prior history of several partial nephrectomies and limited renal reserve, RFA was chosen because of its relatively nephron-sparing nature. A laser guidance device was used to help guide probe placement in an attempt to reduce procedure time and improve targeting accuracy. The device was successful at guiding needle placement, as both tumors were located with a single pass. Follow-up CT scan confirmed accurate needle placement, showing an area of coagulation necrosis covering the previously seen tumor.

  7. Changes in the Areal Extent of Arctic Sea Ice: Observations from Satellites

    NASA Technical Reports Server (NTRS)

    Parkinson, Claire L.

    2000-01-01

    Wintertime sea ice covers 15 million square kilometers of the north polar region, an area exceeding one and a half times the area of the U. S. Even at the end of the summer melt season, sea ice still covers 7 million square kilometers. This vast ice cover is an integral component of the climate system, being moved around by winds and waves, restricting heat and other exchanges between the ocean and atmosphere, reflecting most of the solar radiation incident on it, transporting cold, relatively fresh water equatorward, and affecting the overturning of ocean waters underneath, with impacts that can be felt worldwide. Sea ice also is a major factor in the Arctic ecosystem, affecting life forms ranging from minute organisms living within the ice, sometimes to the tune of millions in a single ice floe, to large marine mammals like walruses that rely on sea ice as a platform for resting, foraging, social interaction, and breeding. Since 1978, satellite technology has allowed the monitoring of the vast Arctic sea ice cover on a routine basis. The satellite observations reveal that, overall, the areal extent of Arctic sea ice has been decreasing since 1978, at an average rate of 2.7% per decade through the end of 1998. Through 1998, the greatest rates of decrease occurred in the Seas of Okhotsk and Japan and the Kara and Barents Seas, with most other regions of the Arctic also experiencing ice extent decreases. The two regions experiencing ice extent increases over this time period were the Bering Sea and the Gulf of St. Lawrence. Furthermore, the satellite data reveal that the sea ice season shortened by over 25 days per decade in the central Sea of Okhotsk and the eastern Barents Sea, and by lesser amounts throughout much of the rest of the Arctic seasonal sea ice region, although not in the Bering Sea or the Gulf of St. Lawrence. Concern has been raised that if the trends toward shortened sea ice seasons and lesser sea ice coverage continue, this could entail major

  8. Multivariate areal analysis of the impact and efficiency of the family planning programme in peninsular Malaysia.

    PubMed

    Tan Boon Ann

    1987-06-01

    The findings of the final phase of a 3-phase multivariate areal analysis study undertaken by the Economic and Social Commission for Asia and the Pacific (ESCAP) in 5 countries of the Asian and Pacific Region, including Malaysia, to examine the impact of family planning programs on fertility and reproduction are reported. The study used Malaysia's administrative district as the unit of analysis because the administration and implementation of socioeconomic development activities, as well as the family planning program, depend to a large extent on the decisions of local organizations at the district or state level. In phase 1, existing program and nonprogram data were analyzed using the multivariate technique to separate the impact of the family planning program net of other developmental efforts. The methodology in the 2nd phase consisted of in-depth investigation of selected areas in order to discern the dynamics and determinants of efficiency. The insights gained in phase 2 regarding dynamics of performance were used in phase 3 to refine the input variables of the phase 1 model. Thereafter, the phase 1 analysis was repeated. Insignificant variables and factors were trimmed in order to present a simplified model for studying the impact of environmental, socioeconomic development, family planning programs, and related factors on fertility. The inclusion of a set of family planning program and development variables in phase 3 increased the predictive power of the impact model. THe explained variance for total fertility rate (TFR) of women under 30 years increased from 71% in phase 1 to 79%. It also raised the explained variance of the efficiency model from 34% to 70%. For women age 30 years and older, their TFR was affected directly by the ethnic composition variable (.76), secondary educational status (-.45), and modern nonagricultural occupation (.42), among others. When controlled for other socioeconomic development and environmental indicators, the

  9. Behavioral cartography of visual functions in cat parietal cortex: areal and laminar dissociations.

    PubMed

    Lomber, S G

    2001-01-01

    deactivation of the superficial layers (I-III) of pMS sulcal cortex selectively and completely impaired performance on the direction of motion discrimination task, while leaving visual attention unimpaired. Additional deactivation of the deeper layers (IV-VI) resulted in impaired visual attention as assessed with visual orienting. These results show a functional bipartite division of labor between upper and lower cortical layers of pMS sulcal cortex. Therefore, spatial, motion and attentional functions can be localized within visuoparietal cortex on both an areal and laminar level.

  10. A Novel Method for Assessing Rainfall Extremes from GCMs and RCMs using Areal Reduction Factors

    NASA Astrophysics Data System (ADS)

    Johnson, F.; Li, J.; Evans, J. P.; Sharma, A.

    2013-12-01

    There is considerable uncertainty in future projections of rainfall extremes which affects flood risk planning. One of the reasons for this uncertainty is the significant biases in both General Circulation Model (GCM) and Regional Climate Model (RCM) simulations of these events. Generally these biases mean that future extreme rainfalls are estimated using a delta-change approach where the observed rainfalls are scaled by the percentage change in the RCM current to future estimates. One aspect that has not received much attention is how spatial patterns of extreme rainfall may change and whether these patterns are represented by GCMs and RCMs with more accuracy than the magnitude of the extreme rainfall totals. Areal reduction factors (ARFs) are a useful tool for considering the spatial patterns of extreme rainfalls. ARFs account for the spatial heterogeneity of storm events by quantifying the required reduction in a point rainfall estimate to give an equivalent area averaged rainfall estimate. The required reduction has been found to be dependent on location, watershed area and size of the rainfall event. This study has investigated the scaling of point to grid rainfall for extreme rainfall events as modelled by a number of GCMs and for dynamically downscaled GCM simulations over south-east Australia from the Weather Research and Forecasting (WRF) model. ARFs are proposed as a novel way of evaluating both the GCM and RCM simulations. For the GCMs, the ARFs provide guidance on the models that best represent the modulation of point rainfalls expected over watershed areas as large as individual GCM cells. The advantage of this approach is that information on the scaling of extreme value distributions with increasing spatial scales can be used to correct the bias in the GCM simulations. For the WRF downscaled results, reanalysis driven simulations show that the representation of observed ARF relationships is quite acceptable. Future changes in ARFs can therefore be

  11. Localized and Areally Extensive Alterations in Marathon Valley, Endeavour Crater Rim, Mars

    NASA Technical Reports Server (NTRS)

    Mittlefehldt, David W.; Gellert, Ralf; Van Bommel, Scott; Arvidson, Raymond E.; Clark, Benton C.; Cohen, Barbara A.; Farrand, William H.; Ming, Douglas W.; Schroeder, Christian; Yen, Albert S.; Jolliff, Bradley L.

    2016-01-01

    Mars Exploration Rover Opportunity is exploring the rim of 22 km diameter, Noachian-aged Endeavour crater. Marathon Valley cuts through the central region of the western rim providing a window into the local lower rim stratigraphic record. Spectra from the Compact Reconnaissance Imaging Spectrometer for Mars show evidence for the occurrence of Fe-Mg smectite in this valley, indicating areally extensive and distinct lithologic units and/or styles of aqueous alteration. The Alpha Particle X-ray Spectrometer has determined the compositions of 59 outcrop targets on untreated, brushed and abraded surfaces. Rocks in the Marathon Valley region are soft breccias composed of mm- to cm-sized darker clasts set in a lighter-toned, finegrained matrix. They are basaltic in non-volatile-element composition and compositionally similar to breccias investigated elsewhere on the rim. Alteration styles recorded in the rocks include: (1) Enrichments in Si, Al, Ti and Cr in more reddish-colored rock, consistent with leaching of more soluble cations and/or precipitation of Si +/- Al, Ti, Cr from fluids. Coprecipitation of Ge-rich phases with Si occurred in the western area only; high water:rock is indicated. Pancam multispectral observations indicate higher nanophase ferric oxide contents, but the rocks have lower Fe contents. The highly localized nature of the red zones indicate they cannot be the source of the widespread smectite signature observed from orbit. (2) Outcrops separated by approximately 65 m show common compositional changes between brushed and abraded (approximately 1 mm deep) targets: increases in S and Mg; decreases in Al, Cl and Ca. These changes are likely due to relatively recent, surface-related alteration of valley rocks and formation of surface coatings under low water:rock. (3) One target, from the center of a region of strong CRISM smectite signature, shows modest differences in composition (higher Si, K; lower Mn) compared to most Marathon Valley rocks, while

  12. Inflight Properties of NIF Ignition Capsules Inferred from Convergent Ablator Experiments

    NASA Astrophysics Data System (ADS)

    Meezan, Nathan

    2012-10-01

    Convergent ablator (ConA) experiments on the National Ignition Facility (NIF) are indirect drive implosions that study the inflight dynamics of an imploding capsule. Side-on, back-lit radiography provides data used by the National Ignition Campaign to infer time-dependent properties of the capsule ablator, including its center of mass radius, velocity, unablated mass, shell thickness, and peak density. Previously, CallahanfootnotetextD. A. Callahan et al., Phys. Plasmas 19, 056305 (2012) and Hicks reported ConA experiments demonstrating velocities approaching those required for ignition. Here, we present the findings from a full year of NIF ConA experiments where we have shot more than 20 targets at energies greater than 1 MJ to study the inflight dynamics of ignition-like implosions. These include: *Studies of ablator center of mass motion vs. time, suggesting that the drive history differs substantially from that predicted by standard modeling *Pulse shape scalings studying the dynamics of a ``fifth shock'' that can significantly increase the entropy of the DT fuel in an ignition implosion. *Performance of different ablators, including CH ablators with graded Si doping, CH ablators with uniform Si doping, and other ablators. *ConA experiments using capsules with cryogenic ice layers, demonstrating that gas-filled capsules are adequate surrogates for DT layered implosions. *Studies of thicker capsules shot at powers and energies surpassing 500 TW and 1.8 MJ as we work to meet the ignition implosion velocity requirement in the presence of hydrodynamic instabilities. Finally, we describe insights into hydrodynamic instabilities that we have gained through this large database, from variations in capsule performance (neutron yield and Tion) as well as from the impact of mix on observed late-time ablator properties.

  13. Microscopic Scale Simulation of the Ablation of Fibrous Materials

    NASA Technical Reports Server (NTRS)

    Lachaud, Jean; Mansour, Nagi N.

    2010-01-01

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

  14. Laser ablated copper plasmas in liquid and gas ambient

    SciTech Connect

    Kumar, Bhupesh; Thareja, Raj K.

    2013-05-15

    The dynamics of copper ablated plasma plumes generated using laser ablation of copper targets in both liquid (de-ionized water) and gas (air) ambients is reported. Using time and space resolved visible emission spectroscopy (450-650 nm), the plasma plumes parameters are investigated. The electron density (n{sub e}) determined using Stark broadening of the Cu I (3d{sup 10}4d{sup 1} {sup 2}D{sub 3/2}-3d{sup 10}4p{sup 1} {sup 2}P{sub 3/2} at 521.8 nm) line is estimated and compared for both plasma plumes. The electron temperature (T{sub e}) was estimated using the relative line emission intensities of the neutral copper transitions. Field emission scanning electron microscopy and energy dispersive x-ray spectral analysis of the ablated copper surface indicated abundance of spherical nanoparticles in liquid while those in air are amalgamates of irregular shapes. The nanoparticles suspended in the confining liquid form aggregates and exhibit a surface plasmon resonance at ∼590 nm.

  15. Long-Life and High-Areal-Capacity Li-S Batteries Enabled by a Light-Weight Polar Host with Intrinsic Polysulfide Adsorption.

    PubMed

    Pang, Quan; Nazar, Linda F

    2016-04-26

    Lithium-sulfur batteries are attractive electrochemical energy storage systems due to their high theoretical energy density and very high natural abundance of sulfur. However, practically, Li-S batteries suffer from short cycling life and low sulfur utilization, particularly in the case of high-sulfur-loaded cathodes. Here, we report on a light-weight nanoporous graphitic carbon nitride (high-surface-area g-C3N4) that enables a sulfur electrode with an ultralow long-term capacity fade rate of 0.04% per cycle over 1500 cycles at a practical C/2 rate. More importantly, it exhibits good high-sulfur-loading areal capacity (up to 3.5 mAh cm(-2)) with stable cell performance. We demonstrate the strong chemical interaction of g-C3N4 with polysulfides using a combination of spectroscopic experimental studies and first-principles calculations. The 53.5% concentration of accessible pyridinic nitrogen polysulfide adsorption sites is shown to be key for the greatly improved cycling performance compared to that of N-doped carbons.

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

    PubMed

    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.

  17. Local Ablation for Hepatocellular Carcinoma in Taiwan

    PubMed Central

    Lin, Shi-Ming

    2013-01-01

    Hepatocellular carcinoma (HCC) is the second commonest cancer in Taiwan. The national surveillance program can detect HCC in its early stages, and various curative modalities (including surgical resection, orthotopic liver transplantation, and local ablation) are employed for the treatment of small HCC. Local ablation therapies are currently advocated for early-stage HCC that is unresectable because of co-morbidities, the need to preserve liver function, or refusal of resection. Among the various local ablation therapies, the most commonly used modalities include percutaneous ethanol injection and radiofrequency ablation (RFA); percutaneous acetic acid injection and microwave ablation are used less often. RFA is more commonly employed than other local ablative modalities in Taiwan because the technique is highly effective, minimally invasive, and requires fewer sessions. RFA is therefore advocated in Taiwan as the first-line curative therapy for unresectable HCC or even for resectable HCC. However, current RFA procedures are less effective against tumors that are in high-risk or difficult-to-ablate locations, are poorly visualized on ultrasonography (US), or are large. Recent advancements in RFA in Taiwan can resolve these issues by the creation of artificial ascites or pleural effusion, application of real-time virtual US assistance, use of combination therapy before RFA, or use of switching RF controllers with multiple electrodes. This review article provides updates on the clinical outcomes and advances in local ablative modalities (mostly RFA) for HCC in Taiwan. PMID:24159599

  18. Testing and evaluation of light ablation decontamination

    SciTech Connect

    Demmer, R.L.; Ferguson, R.L.

    1994-10-01

    This report details the testing and evaluation of light ablation decontamination. It details WINCO contracted research and application of light ablation efforts by Ames Laboratory. Tests were conducted with SIMCON (simulated contamination) coupons and REALCON (actual radioactive metal coupons) under controlled conditions to compare cleaning effectiveness, speed and application to plant process type equipment.

  19. Effective temperatures of polymer laser ablation

    NASA Astrophysics Data System (ADS)

    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.

  20. Ablative therapies for small renal tumours.

    PubMed

    Castro, Arturo; Jenkins, Lawrence C; Salas, Nelson; Lorber, Gideon; Leveillee, Raymond J

    2013-05-01

    Improvements in imaging technology have resulted in an increase in detection of small renal masses (SRMs). Minimally invasive ablation modalities, including cryoablation, radiofrequencey ablation, microwave ablation and irreversible electroporation, are currently being used to treat SRMs in select groups of patients. Cryoablation and radiofrequency ablation have been extensively studied. Presently, cryoablation is gaining popularity because the resulting ice ball can be visualized easily using ultrasonography. Tumour size and location are strong predictors of outcome of radiofrequency ablation. One of the main benefits of microwave ablation is that microwaves can propagate through all types of tissue, including desiccated and charred tissue, as well as water vapour, which might be formed during the ablation. Irreversible electroporation has been shown in animal studies to affect only the cell membrane of undesirable target tissues and to spare adjacent structures; however, clinical studies that depict the efficacy and safety of this treatment modality in humans are still sparse. As more experience is gained in the future, ablation modalities might be utilized in all patients with tumours <4 cm in diameter, rather than just as an alternative treatment for high-risk surgical patients.

  1. Lung Cancer Ablation: Technologies and Techniques

    PubMed Central

    Alexander, Erica S.; Dupuy, Damian E.

    2013-01-01

    The incidence of lung cancers in 2012 is estimated to reach 226,160 new cases, with only a third of patients suitable surgical candidates. Tumor ablation has emerged as an important and efficacious treatment option for nonsurgical lung cancer patients. This localized minimally invasive therapy is best suited for small oligonodular lesions or favorably located metastatic tumors. Radiofrequency ablation has been in use for over a decade, and newer modalities including microwave ablation, cryoablation, and irreversible electroporation have emerged as additional treatment options for patients. Ablation therapies can offer patients and clinicians a repeatable and effective therapy for palliation and, in some cases, cure of thoracic malignancies. This article discusses the available technologies and techniques available for tumor ablation of thoracic malignancies including patient selection, basic aspects of procedure technique, imaging follow-up, treatment outcomes, and comparisons between various therapies. PMID:24436530

  2. Lung cancer ablation: technologies and techniques.

    PubMed

    Alexander, Erica S; Dupuy, Damian E

    2013-06-01

    The incidence of lung cancers in 2012 is estimated to reach 226,160 new cases, with only a third of patients suitable surgical candidates. Tumor ablation has emerged as an important and efficacious treatment option for nonsurgical lung cancer patients. This localized minimally invasive therapy is best suited for small oligonodular lesions or favorably located metastatic tumors. Radiofrequency ablation has been in use for over a decade, and newer modalities including microwave ablation, cryoablation, and irreversible electroporation have emerged as additional treatment options for patients. Ablation therapies can offer patients and clinicians a repeatable and effective therapy for palliation and, in some cases, cure of thoracic malignancies. This article discusses the available technologies and techniques available for tumor ablation of thoracic malignancies including patient selection, basic aspects of procedure technique, imaging follow-up, treatment outcomes, and comparisons between various therapies.

  3. Ablative shielding for hypervelocity projectiles

    NASA Technical Reports Server (NTRS)

    Rucker, Michelle A. (Inventor)

    1993-01-01

    A hypervelocity projectile shield which includes a hollow semi-flexible housing fabricated from a plastic like, or otherwise transparent membrane which is filled with a fluid (gas or liquid) is presented. The housing has a inlet valve, similar to that on a tire or basketball, to introduce an ablating fluid into the housing. The housing is attached by a Velcro mount or double-sided adhesive tape to the outside surface of a structure to be protected. The housings are arrayed in a side-by-side relationship for complete coverage of the surface to be protected. In use, when a hypervelocity projectile penetrates the outer wall of a housing it is broken up and then the projectile is ablated as it travels through the fluid, much like a meteorite 'burns up' as it enters the earth's atmosphere, and the housing is deflated. The deflated housing can be easily spotted for replacement, even from a distance. Replacement is then accomplished by simply pulling a deflated housing off the structure and installing a new housing.

  4. Tumor Ablation with Irreversible Electroporation

    PubMed Central

    Al-Sakere, Bassim; André, Franck; Bernat, Claire; Connault, Elisabeth; Opolon, Paule; Davalos, Rafael V.; Rubinsky, Boris; Mir, Lluis M.

    2007-01-01

    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 µs 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. PMID:17989772

  5. Stellar Ablation of Planetary Atmospheres

    NASA Technical Reports Server (NTRS)

    Moore, Thomas E.; Horwitz, J. L.

    2007-01-01

    We review observations and theories of the solar ablation of planetary atmospheres, focusing on the terrestrial case where a large magnetosphere holds off the solar wind, so that there is little direct atmospheric impact, but also couples the solar wind electromagnetically to the auroral zones. We consider the photothermal escape flows known as the polar wind or refilling flows, the enhanced mass flux escape flows that result from localized solar wind energy dissipation in the auroral zones, and the resultant enhanced neutral atom escape flows. We term these latter two escape flows the "auroral wind." We review observations and theories of the heating and acceleration of auroral winds, including energy inputs from precipitating particles, electromagnetic energy flux at magnetohydrodynamic and plasma wave frequencies, and acceleration by parallel electric fields and by convection pickup processes also known as "centrifugal acceleration." We consider also the global circulation of ionospheric plasmas within the magnetosphere, their participation in magnetospheric disturbances as absorbers of momentum and energy, and their ultimate loss from the magnetosphere into the downstream solar wind, loading reconnection processes that occur at high altitudes near the magnetospheric boundaries. We consider the role of planetary magnetization and the accumulating evidence of stellar ablation of extrasolar planetary atmospheres. Finally, we suggest and discuss future needs for both the theory and observation of the planetary ionospheres and their role in solar wind interactions, to achieve the generality required for a predictive science of the coupling of stellar and planetary atmospheres over the full range of possible conditions.

  6. Flyer Acceleration by Pulsed Ion Beam Ablation and Application for Space Propulsion

    SciTech Connect

    Harada, Nobuhiro; Buttapeng, Chainarong; Yazawa, Masaru; Kashine, Kenji; Jiang Weihua; Yatsui, Kiyoshi

    2004-02-04

    Flyer acceleration by ablation plasma pressure produced by irradiation of intense pulsed ion beam has been studied. Acceleration process including expansion of ablation plasma was simulated based on fluid model. And interaction between incident pulsed ion beam and a flyer target was considered as accounting stopping power of it. In experiments, we used ETIGO-II intense pulsed ion beam generator with two kinds of diodes; 1) Magnetically Insulated Diode (MID, power densities of <100 J/cm2) and 2) Spherical-focused Plasma Focus Diode (SPFD, power densities of up to 4.3 kJ/cm2). Numerical results of accelerated flyer velocity agreed well with measured one over wide range of incident ion beam energy density. Flyer velocity of 5.6 km/s and ablation plasma pressure of 15 GPa was demonstrated by the present experiments. Acceleration of double-layer target consists of gold/aluminum was studied. For adequate layer thickness, such a flyer target could be much more accelerated than a single layer. Effect of waveform of ion beam was also examined. Parabolic waveform could accelerate more efficiently than rectangular waveform. Applicability of ablation propulsion was discussed. Specific impulse of 7000{approx}8000 seconds and time averaged thrust of up to 5000{approx}6000N can be expected. Their values can be controllable by changing power density of incident ion beam and pulse duration.

  7. KrF laser-induced ablation and patterning of Y--Ba--Cu--O films

    SciTech Connect

    Heitz, J.; Wang, X.Z.; Schwab, P.; Baeuerle, D. ); Schultz, L. )

    1990-09-01

    The ablation and patterning of Y--Ba--Cu--O films on (100) SrTiO{sub 3} and (100) MgO substrates by KrF excimer-laser light projection was investigated. Three different regimes of laser-material interactions were observed. Transition temperatures and critical current densities in laser-fabricated strip lines were investigated.

  8. Planar laser-driven ablation model for nonlocalized absorption

    SciTech Connect

    Dahmani, F.; Kerdja, T. )

    1991-05-01

    A model for planar laser-driven ablation is presented. Nonlocalized inverse bremsstrahlung absorption of laser energy at a density {ital n}{sub 1}{lt}{ital n}{sub {ital c}} is assumed. A steady-state solution in the conduction zone is joined to a rarefaction wave in the underdense plasma. The calculations relate all steady-state fluid quantities to only the material, absorbed intensity, and laser wavelength. The theory agrees well with results from a computer hydrodynamics code MEDUSA (Comput. Phys. Commun. {bold 7}, 271 (1974)) and experiments.

  9. Pulsed infrared laser ablation and clinical applications

    NASA Astrophysics Data System (ADS)

    Chan, Kin Foong

    Sufficient light energy deposited in tissue can result in ablation and excessive thermal and mechanical damage to adjacent tissues. The goals of this research are to investigate the mechanisms of pulsed infrared laser ablation of tissue, to optimize laser parameters for minimizing unnecessary damage to healthy tissue, and to explore the potential of using pulsed infrared lasers for clinical applications, especially laser lithotripsy. A dual-channel optical low coherence reflectometer was implemented to measure the expansion and collapse velocities of a Q-switched Ho:YAG (λ = 2.12 μm) laser-induced cavitation in water. Cavitation wall velocities up to 11 m/s were measured with this technique, and the results were in fair agreement with those calculated from fast-flash photographic images. The dependence of ablation threshold fluence on calculus absorption was examined. Preliminary results indicated that the product of optical absorption and ablation threshold fluence, which is the heat of ablation, remained constant for a given urinary calculus type and laser pulse duration. An extended study examined the influence of optical absorption on pulsed infrared laser ablation. An analytical photothermal ablation model was applied and compared to experimental ablation results using an infrared free-electron laser at selected wavelengths between 2.12 μm and 6.45 μm Results were in good agreement with the model, and the ablation depths of urinary calculi were highly dependent upon the calculus optical absorption as well as light attenuation within the intrapulse ablation plume. An efficient wavelength for ablation corresponded to the wavelength of the Er:YAG laser (λ = 2.94 μm) suggested this laser should be examined for laser lithotripsy. Schlieren flash photography, acoustic transient measurements with a piezoelectric polyvinylidene-fluoride needle-hydrophone, mass loss measurements, and chemical analyses were employed to study the ablation mechanisms of the free

  10. Proposed linear energy transfer areal detector for protons using radiochromic film

    NASA Astrophysics Data System (ADS)

    Mayer, Rulon; Lin, Liyong; Fager, Marcus; Douglas, Dan; McDonough, James; Carabe, Alejandro

    2015-04-01

    LET with the LET measured using radiochromic film at the pixel level over extended areas. Failure rates using gamma analysis are calculated for areas in the dose distribution using parameters of 25% of MC LET and 3 mm. The processed dose distributions find 5%-10% failure rates for the narrow 12.5 and 15 cm proton ranges and 10%-15% for proton ranges of 15, 17.5, and 20 cm and modulated by 5 cm. It is found through gamma analysis that the measured proton energy deposition in radiochromic film and TPS can be used to determine LET. This modified film dosimetry provides an experimental areal LET measurement that can verify MC calculations, support LET point measurements, possibly enhance biologically based proton treatment planning, and determine the polymerization process within the radiochromic film.

  11. Proposed linear energy transfer areal detector for protons using radiochromic film

    SciTech Connect

    Mayer, Rulon; Lin, Liyong; Fager, Marcus; Douglas, Dan; McDonough, James; Carabe, Alejandro

    2015-04-15

    LET with the LET measured using radiochromic film at the pixel level over extended areas. Failure rates using gamma analysis are calculated for areas in the dose distribution using parameters of 25% of MC LET and 3 mm. The processed dose distributions find 5%–10% failure rates for the narrow 12.5 and 15 cm proton ranges and 10%–15% for proton ranges of 15, 17.5, and 20 cm and modulated by 5 cm. It is found through gamma analysis that the measured proton energy deposition in radiochromic film and TPS can be used to determine LET. This modified film dosimetry provides an experimental areal LET measurement that can verify MC calculations, support LET point measurements, possibly enhance biologically based proton treatment planning, and determine the polymerization process within the radiochromic film.

  12. Relationships between sinkholes areal distribution and main tectonic alignments in Abruzzo (Central Italy)

    NASA Astrophysics Data System (ADS)

    Ferrini, G.; Moretti, A.; De Rose, C.; Stagnini, E.,; Serafini, M.

    2012-04-01

    present there is no evidence of hydrothermal activity or gas diffusion, morphological and geostructural analogy with the hydrothermal field of San Vittorino (Rieti) suggest dissolution processes related to the rising of underground mineralized fluids (piping) and a subsequent collapse phase, in a classic sink-hole evolutionary model. To note the areal distribution of these elements developed in a narrow band , WNW-ESE oriented, running for about 40 km parallel back to the tectonic front of the Gran Sasso and coinciding, with good approximation, to the seismogenic source of the earthquake of April 6th 2009 and of the major historical earthquakes which hit the region. Geophysical survey carried out after the last strong seismic event pointed out the presence of large hidden cavities developed in the Neogene sedimentary filling of the L'Aquila basin confirming that the phenomenon cannot be considered exhausted; then a geochemical mapping of the all area is started to identify suitable sites for monitoring fluid in relation to seismic activity and to evaluate the risk of potential, sudden phenomena of gravitational collapse.

  13. MARG - A Low Cost Solid State Microwave Areal Precipitation Measurement System

    NASA Astrophysics Data System (ADS)

    Paulitsch, Helmut; Dombai, Ferenc; Cremonini, Roberto; Bechini, Renzo

    2014-05-01

    Water is an essential resource for us so the measurements of its movement throughout the whole cycle is very important. The rainfall is discontinuous in space and in time having large natural variability unlike many other meteorological parameters. The widely used method for getting relatively accurate precipitation data over land is the combination of radar rainfall estimations and rain gauge data. The typically used radar data is coming from long-range weather radars operating in C or S band, or from mini radars operating in X band which is attenuating heavily in strong precipitation. Using such radar data we are facing several constraints: operating costs and limitations of long range radars, X band radars can be blocked totally in heavy thunderstorms even in short range, dual polarization solutions are expensive, etc. Recognizing that an important gap exists in instrumental precipitation measurements over land a consortium has been organized and a project has been established to develop a new measurement device, the so called Microwave Areal Rain Gauge (MARG). MARG is based on FMCW radar principle using solid state transmitter and digital signal processing and operating in C band. The MARG project aims to provide an innovative, real-time, low-cost, user friendly and accurate sensor technology to monitor and to measure continuously the rainfall intensity distribution over an area around some thousand square km. The MARG project proposal has been granted by the EU in FP7-SME-2012 funding scheme. The developed instrument is able to monitor in real-time intensity and spatial distribution of rainfall in rural and urban environments and can be operated by commercial weather data and value-added forecast product suppliers. To achieve sufficient isolation between the transmitter and receiver modules, and to avoid using complex and expensive microwave components, two parabolic antennae are used to transmit and receive the FMCW signal. The radar frontend operates in the

  14. Proposed linear energy transfer areal detector for protons using radiochromic film.

    PubMed

    Mayer, Rulon; Lin, Liyong; Fager, Marcus; Douglas, Dan; McDonough, James; Carabe, Alejandro

    2015-04-01

    LET with the LET measured using radiochromic film at the pixel level over extended areas. Failure rates using gamma analysis are calculated for areas in the dose distribution using parameters of 25% of MC LET and 3 mm. The processed dose distributions find 5%-10% failure rates for the narrow 12.5 and 15 cm proton ranges and 10%-15% for proton ranges of 15, 17.5, and 20 cm and modulated by 5 cm. It is found through gamma analysis that the measured proton energy deposition in radiochromic film and TPS can be used to determine LET. This modified film dosimetry provides an experimental areal LET measurement that can verify MC calculations, support LET point measurements, possibly enhance biologically based proton treatment planning, and determine the polymerization process within the radiochromic film.

  15. How spatial variation in areal extent and configuration of labile vegetation states affect the riparian bird community in Arctic tundra.

    PubMed

    Henden, John-André; Yoccoz, Nigel G; Ims, Rolf A; Langeland, Knut

    2013-01-01

    The Arctic tundra is currently experiencing an unprecedented combination of climate change, change in grazing pressure by large herbivores and growing human activity. Thickets of tall shrubs represent a conspicuous vegetation state in northern and temperate ecosystems, where it serves important ecological functions, including habitat for wildlife. Thickets are however labile, as tall shrubs respond rapidly to both abiotic and biotic environmental drivers. Our aim was to assess how large-scale spatial variation in willow thicket areal extent, configuration and habitat structure affected bird abundance, occupancy rates and species richness so as to provide an empirical basis for predicting the outcome of environmental change for riparian tundra bird communities. Based on a 4-year count data series, obtained through a large-scale study design in low arctic tundra in northern Norway, statistical hierarchical community models were deployed to assess relations between habitat configuration and bird species occupancy and community richness. We found that species abundance, occupancy and richness were greatly affected by willow areal extent and configuration, habitat features likely to be affected by intense ungulate browsing as well as climate warming. In sum, total species richness was maximized in large and tall willow patches of small to intermediate degree of fragmentation. These community effects were mainly driven by responses in the occupancy rates of species depending on tall willows for foraging and breeding, while species favouring other vegetation states were not affected. In light of the predicted climate driven willow shrub encroachment in riparian tundra habitats, our study predicts that many bird species would increase in abundance, and that the bird community as a whole could become enriched. Conversely, in tundra regions where overabundance of large herbivores leads to decreased areal extent, reduced height and increased fragmentation of willow thickets

  16. How Spatial Variation in Areal Extent and Configuration of Labile Vegetation States Affect the Riparian Bird Community in Arctic Tundra

    PubMed Central

    Henden, John-André; Yoccoz, Nigel G.; Ims, Rolf A.; Langeland, Knut

    2013-01-01

    The Arctic tundra is currently experiencing an unprecedented combination of climate change, change in grazing pressure by large herbivores and growing human activity. Thickets of tall shrubs represent a conspicuous vegetation state in northern and temperate ecosystems, where it serves important ecological functions, including habitat for wildlife. Thickets are however labile, as tall shrubs respond rapidly to both abiotic and biotic environmental drivers. Our aim was to assess how large-scale spatial variation in willow thicket areal extent, configuration and habitat structure affected bird abundance, occupancy rates and species richness so as to provide an empirical basis for predicting the outcome of environmental change for riparian tundra bird communities. Based on a 4-year count data series, obtained through a large-scale study design in low arctic tundra in northern Norway, statistical hierarchical community models were deployed to assess relations between habitat configuration and bird species occupancy and community richness. We found that species abundance, occupancy and richness were greatly affected by willow areal extent and configuration, habitat features likely to be affected by intense ungulate browsing as well as climate warming. In sum, total species richness was maximized in large and tall willow patches of small to intermediate degree of fragmentation. These community effects were mainly driven by responses in the occupancy rates of species depending on tall willows for foraging and breeding, while species favouring other vegetation states were not affected. In light of the predicted climate driven willow shrub encroachment in riparian tundra habitats, our study predicts that many bird species would increase in abundance, and that the bird community as a whole could become enriched. Conversely, in tundra regions where overabundance of large herbivores leads to decreased areal extent, reduced height and increased fragmentation of willow thickets

  17. On the Ablation Models of Fuel Pellets

    SciTech Connect

    Rozhansky, V.A.; Senichenkov, I.Yu.

    2005-12-15

    The neutral gas shielding model and neutral-gas-plasma shielding model are analyzed qualitatively. The main physical processes that govern the formation of the shielding gas cloud and, consequently, the ablation rate are considered. For the neutral gas shielding model, simple formulas relating the ablation rate and cloud parameters to the parameters of the pellet and the background plasma are presented. The estimates of the efficiency of neutral gas shielding and plasma shielding are compared. It is shown that the main portion of the energy flux of the background electrons is released in the plasma cloud. Formulas for the ablation rate and plasma parameters are derived in the neutral-gas-plasma shielding model. The question is discussed as to why the neutral gas shielding model describes well the ablation rate of the pellet material, although it does not take into account the ionization effects and the effects associated with the interaction of ionized particles with the magnetic field. The reason is that the ablation rate depends weakly on the energy flux of hot electrons; as a result, the attenuation of this flux by the electrostatic shielding and plasma shielding has little effect on the ablation rate. This justifies the use of the neutral gas shielding model to estimate the ablation rate (to within a factor of about 2) over a wide range of parameters of the pellet and the background plasma.

  18. [Indications for catheter ablation of ventricular tachycardia].

    PubMed

    Deneke, T; Israel, C W; Krug, J; Nentwich, K; Müller, P; Mügge, A; Schade, A

    2013-09-01

    Ventricular tachyarrhythmias (VT) can cause sudden cardiac death. This can be prevented by an implantable cardioverter-defibrillator (ICD) but approximately 25% of patients with an ICD develop electrical storm (≥ 3 VTs within 24 hours) during the course of 4-5 years. This is a life-threatening event even in the presence of an ICD, particularly if incessant VT is present, and may significantly deteriorate the patient's psychological state if multiple shocks are discharged. Catheter ablation of VT has developed into a standard procedure in many specialized electrophysiology centers. Patients with hemodynamically stable and unstable VT are amendable to substrate-based ablation strategies. Catheter ablation can be performed as emergency procedure in patients with electrical storm as well as electively in patients with monomorphic VT stored in ICD memory. In patients with ischemic or non-ischemic cardiomyopathy, VT ablation is complementary to ICD implantation and can reduce the number of ventricular arrhythmia episodes and shocks and should be performed early. In patients with electrical storm, catheter ablation can acutely achieve rhythm stabilization and may improve prognosis in the long term. Further indications for catheter ablation exist in patients with idiopathic VT where catheter ablation represents a curative therapy, and in patients with symptomatic or asymptomatic frequent premature ventricular beats which may improve prognosis in patients with heart failure and cardiac resynchronization therapy.

  19. Analysis of infrared laser tissue ablation

    NASA Astrophysics Data System (ADS)

    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.

  20. Thermal therapy, Part III: ablation techniques.

    PubMed

    Habash, Riadh W Y; Bansal, Rajeev; Krewski, Daniel; Alhafid, Hafid T

    2007-01-01

    Ablative treatments are gaining increasing attention as an alternative to standard surgical therapies, especially for patients with contraindication or those who refuse open surgery. Thermal ablation is used in clinical applications mainly for treating heart arrhythmias, benign prostate hyperplasia, and nonoperable liver tumors; there is also increasing application to other organ sites, including the kidney, lung, and brain. Potential benefits of thermal ablation include reduced morbidity and mortality in comparison with standard surgical resection and the ability to treat nonsurgical patients. The purpose of this review is to outline and discuss the engineering principles and biological responses by which thermal ablation techniques can provide elevation of temperature in organs within the human body. Because of the individual problems associated with each type of treatment, a wide range of ablation techniques have evolved including cryoablation as well as ultrasound, radiofrequency (RF), microwave, and laser ablation. Aspects of each ablation technique, including mechanisms of action, equipment required, selection of eligible patients, treatment techniques, and patient outcomes are presented, along with a discussion of limitations of the techniques and future research directions.

  1. Thermal protection system ablation sensor

    NASA Technical Reports Server (NTRS)

    Gorbunov, Sergey (Inventor); Martinez, Edward R. (Inventor); Scott, James B. (Inventor); Oishi, Tomomi (Inventor); Fu, Johnny (Inventor); Mach, Joseph G. (Inventor); Santos, Jose B. (Inventor)

    2011-01-01

    An isotherm sensor tracks space vehicle temperatures by a thermal protection system (TPS) material during vehicle re-entry as a function of time, and surface recession through calibration, calculation, analysis and exposed surface modeling. Sensor design includes: two resistive conductors, wound around a tube, with a first end of each conductor connected to a constant current source, and second ends electrically insulated from each other by a selected material that becomes an electrically conductive char at higher temperatures to thereby complete an electrical circuit. The sensor conductors become shorter as ablation proceeds and reduced resistance in the completed electrical circuit (proportional to conductor length) is continually monitored, using measured end-to-end voltage change or current in the circuit. Thermocouple and/or piezoelectric measurements provide consistency checks on local temperatures.

  2. Radiofrequency Ablation: A Nursing Perspective

    PubMed Central

    Locklin, Julia K.; Wood, Bradford J.

    2008-01-01

    Radiofrequency ablation (RFA) has emerged as a safe and predictable technology for treating certain patients with cancer who otherwise have few treatment options. Nurses need to be familiar with all phases of the RFA procedure to create an optimal environment for patients. This article offers a brief review of the RFA procedure and nurses' responsibilities in caring for these patients. Before RFA, nurses should focus on patient education and aggressive hydration. During the procedure, nurses can prevent injury by placing grounding pads appropriately, monitoring vital signs, and medicating patients as needed. After RFA, nurses should assess the skin puncture site, provide adequate pain relief, and, again, hydrate patients. Nurses who care appropriately for RFA recipients may help to improve patient outcomes and make an otherwise frightening procedure more comfortable. PMID:15973845

  3. Ablation of idiopathic ventricular tachycardia.

    PubMed

    Schreiber, Doreen; Kottkamp, Hans

    2010-09-01

    Idiopathic ventricular arrhythmias occur in patients without structural heart disease. They can arise from a variety of specific areas within both ventricles and in the supravalvular regions of the great arteries. Two main groups need to be differentiated: arrhythmias from the outflow tract (OT) region and idiopathic left ventricular, so-called fascicular, tachycardias (ILVTs). OT tachycardia typically originates in the right ventricular OT, but may also occur in the left ventricular OT, particularly in the sinuses of Valsalva or the anterior epicardium or the great cardiac vein. Activation mapping or pace mapping for the OT regions and mapping of diastolic potentials in ILVTs are the mapping techniques that are typically used. The ablation of idiopathic ventricular arrhythmias is highly successful, associated with only rare complications. Newly recognized entities of idiopathic ventricular tachycardias are those originating in the papillary muscles and in the atrioventricular annular regions.

  4. Initial development of an ablative leading edge for the space shuttle orbiter

    NASA Technical Reports Server (NTRS)

    Daforno, G.; Rose, L.; Graham, J.; Roy, P.

    1974-01-01

    A state-of-the-art preliminary design for typical wing areas is developed. Seven medium-density ablators (with/without honeycomb, flown on Apollo, Prime, X15A2) are evaluated. The screening tests include: (1) leading-edge models sequentially subjected to ascent heating, cold soak, entry heating, post-entry pressure fluctuations, and touchdown shock, and (2) virgin/charred models subjected to bondline strains. Two honeycomb reinforced 30 pcf elastomeric ablators were selected. Roughness/recession degradation of low speed aerodynamics appears acceptable. The design, including attachments, substructure and joints, is presented.

  5. Dynamic response of laser ablative shock waves from coated and uncoated amorphous boron nanoparticles

    NASA Astrophysics Data System (ADS)

    Chelikani, Leela; Pinnoju, Venkateshwarlu; Verma, Pankaj; Singh, Raja V.; Kiran, P. Prem

    2017-01-01

    Laser ablative shock waves from compacted nano-sized powders was studied using time resolved shadowgraphy technique. Shock wave properties such as propagation of shock front, contact front, velocity and pressure behind the shock front were studied from nano-sized powders of Amorphous Boron (B) and Lithium Fluoride coated Boron (LiF-B) with the material density of 2.34 g/cc. The experiments were performed to understand the challenging aspects of laser-powder interactions to explore their application potential for laser ablation Propulsion (LAP).

  6. Nanosecond laser ablation of gold nanoparticle films

    SciTech Connect

    Ko, Seung H.; Choi, Yeonho; Hwang, David J.; Grigoropoulos, Costas P.; Chung, Jaewon; Poulikakos, Dimos

    2006-10-02

    Ablation of self-assembled monolayer protected gold nanoparticle films on polyimide was explored using a nanosecond laser. When the nanoparticle film was ablated and subsequently thermally sintered to a continuous film, the elevated rim structure by the expulsion of molten pool could be avoided and the ablation threshold fluence was reduced to a value at least ten times lower than the reported threshold for the gold film. This could be explained by the unusual properties of nanoparticle film such as low melting temperature, weak bonding between nanoparticles, efficient laser energy deposition, and reduced heat loss. Finally, submicron lines were demonstrated.

  7. IR laser ablation of dental enamel

    NASA Astrophysics Data System (ADS)

    Fried, Daniel

    2000-03-01

    An overview of the basic mechanisms of IR laser ablation of dental enamel is presented. Enamel is a highly structured tissue consisting of an heterogeneous distribution of water, mineral, protein and lipid. Absorption bands of water and carbonated hydroxyapatite can be selectively targeted from 2.7 to 11-micrometer via several laser wavelengths. Mechanistic differences in the nature of ablation and the varying surface morphology produced can be explained by the microstructure of the tissue. Suggested criteria for the choice of the optimum laser parameters for clinical use, the influence of plasma shielding and the role of exogenous water on the mechanism of ablation are discussed.

  8. Radiofrequency Ablation of Persistent Atrial Fibrillation

    PubMed Central

    Hussein, Ayman A.; Saliba, Walid I.; Barakat, Amr; Bassiouny, Mohammed; Chamsi-Pasha, Mohammed; Al-Bawardy, Rasha; Hakim, Ali; Tarakji, Khaldoun; Baranowski, Bryan; Cantillon, Daniel; Dresing, Thomas; Tchou, Patrick; Martin, David O.; Varma, Niraj; Bhargava, Mandeep; Callahan, Thomas; Niebauer, Mark; Kanj, Mohamed; Chung, Mina; Natale, Andrea; Lindsay, Bruce D.; Wazni, Oussama M.

    2017-01-01

    Background Various ablation strategies of persistent atrial fibrillation (PersAF) have had disappointing outcomes, despite concerted clinical and research efforts, which could reflect progressive atrial fibrillation–related atrial remodeling. Methods and Results Two-year outcomes were assessed in 1241 consecutive patients undergoing first-time ablation of PersAF (2005–2012). The time intervals between the first diagnosis of PersAF and the ablation procedures were determined. Patients had echocardiograms and measures of B-type natriuretic peptide and C-reactive protein before the procedures. The median diagnosis-to-ablation time was 3 years (25th–75th percentiles 1–6.5). With longer diagnosis-to-ablation time (based on quartiles), there was a significant increase in recurrence rates in addition to an increase in B-type natriuretic peptide levels (P=0.01), C-reactive protein levels (P<0.0001), and left atrial size (P=0.03). The arrhythmia recurrence rates over 2 years were 33.6%, 52.6%, 57.1%, and 54.6% in the first, second, third, and fourth quartiles, respectively (Pcategorical<0.0001). In Cox Proportional Hazard analyses, B-type natriuretic peptide levels, C-reactive protein levels, and left atrial size were associated with arrhythmia recurrence. The diagnosis-to-ablation time had the strongest association with the ablation outcomes which persisted in multivariable Cox analyzes (hazard ratio for recurrence per +1Log diagnosis-to-ablation time 1.27, 95% confidence interval 1.14–1.43; P<0.0001; hazard ratio fourth versus first quartile 2.44, 95% confidence interval 1.68–3.65; Pcategorical<0.0001). Conclusions In patients with PersAF undergoing ablation, the time interval between the first diagnosis of PersAF and the catheter ablation procedure had a strong association with the ablation outcomes, such as shorter diagnosis-to-ablation times were associated with better outcomes and in direct association with markers of atrial remodeling. PMID:26763227

  9. Ablation of pulmonary malignancy: current status.

    PubMed

    Pua, Bradley B; Thornton, Raymond H; Solomon, Stephen B

    2010-08-01

    Since the first reported use of radiofrequency ablation of the lung in 2000, the field of image-guided lung ablation has received a considerable amount of attention. Survival studies have demonstrated the potential utility of thermal ablation in the treatment of patients with early-stage primary and limited secondary pulmonary tumors with promising results. Diagnostic imaging studies have advanced the understanding of the expected immediate postablation appearance of treated lesions, leading the way for early detection of local tumor progression. These survival studies and the expected imaging follow-up of these patients are reviewed herein.

  10. Pulsed and CW adjustable 1942 nm single-mode all-fiber Tm-doped fiber laser system for surgical laser soft tissue ablation applications.

    PubMed

    Huang, Yize; Jivraj, Jamil; Zhou, Jiaqi; Ramjist, Joel; Wong, Ronnie; Gu, Xijia; Yang, Victor X D

    2016-07-25

    A surgical laser soft tissue ablation system based on an adjustable 1942 nm single-mode all-fiber Tm-doped fiber laser operating in pulsed or CW mode with nitrogen assistance is demonstrated. Ex vivo ablation on soft tissue targets such as muscle (chicken breast) and spinal cord (porcine) with intact dura are performed at different ablation conditions to examine the relationship between the system parameters and ablation outcomes. The maximum laser average power is 14.4 W, and its maximum peak power is 133.1 W with 21.3 μJ pulse energy. The maximum CW power density is 2.33 × 106 W/cm2 and the maximum pulsed peak power density is 2.16 × 107 W/cm2. The system parameters examined include the average laser power in CW or pulsed operation mode, gain-switching frequency, total ablation exposure time, and the input gas flow rate. The ablation effects were measured by microscopy and optical coherence tomography (OCT) to evaluate the ablation depth, superficial heat-affected zone diameter (HAZD) and charring diameter (CD). Our results conclude that the system parameters can be tailored to meet different clinical requirements such as ablation for soft tissue cutting or thermal coagulation for future applications of hemostasis.

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

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  13. Negative correlation between extent of physeal ablation after percutaneous permanent physiodesis and postoperative growth

    PubMed Central

    Horn, Joachim; Kibsgård, Thomas; Kristiansen, Leif Pål; Pripp, Are Hugo; Steen, Harald

    2013-01-01

    Background and purpose Percutaneous physiodesis in the knee region is a well-established method for treating leg-length inequality. Longitudinal growth in the physis is believed to stop almost immediately after the operation. The extent of physis ablation required has never been investigated by any kind of tomography in humans. Using radiostereometric analysis (RSA), we determined when definite growth arrest occurred after surgery. We also studied the correlation between the extent of physis ablation and postoperative growth. Finally, we assessed any bone bridging across the physis. Methods 6, 12, and 30 weeks after surgery, we used RSA to measure longitudinal growth in 27 patients (37 physes) with a mean age of 13 years. CT scanning of the knee region was performed 12 weeks after surgery to measure the percentage of the ablated physis and to determine the distribution of bone bridges across the physis. Results RSA showed that growth rate was reduced to less than half of the expected rate after 6 weeks. During the next 6 weeks, the growth ceased completely. CT scans revealed a large variation in the extent of ablated physes (17–69%). In the ablated areas, tissues of various densities were mixed with mature bone. Bridges were found both laterally and medially across the physes in all of the patients. There was a negative correlation between the extent of ablation and total postoperative growth (rho = –0.37, p = 0.03). Interpretation Growth across the physis is effectively stopped by percutaneous physiodesis. RSA is well-suited for observation of this phenomenon. Volume CT scanning can be used to detect bone bridges that cross the physis and to calculate the extent of physis ablation. PMID:23799346

  14. Finite-difference model to simulate the areal flow of saltwater and fresh water separated by an interface

    USGS Publications Warehouse

    Mercer, James W.; Larson, S.P.; Faust, Charles R.

    1980-01-01

    Model documentation is presented for a two-dimensional (areal) model capable of simulating ground-water flow of salt water and fresh water separated by an interface. The partial differential equations are integrated over the thicknesses of fresh water and salt water resulting in two equations describing the flow characteristics in the areal domain. These equations are approximated using finite-difference techniques and the resulting algebraic equations are solved for the dependent variables, fresh water head and salt water head. An iterative solution method was found to be most appropriate. The program is designed to simulate time-dependent problems such as those associated with the development of coastal aquifers, and can treat water-table conditions or confined conditions with steady-state leakage of fresh water. The program will generally be most applicable to the analysis of regional aquifer problems in which the zone between salt water and fresh water can be considered a surface (sharp interface). Example problems and a listing of the computer code are included. (USGS).

  15. A Sharp Cadherin-6 Gene Expression Boundary in the Developing Mouse Cortical Plate Demarcates the Future Functional Areal Border

    PubMed Central

    Terakawa, Youhei W.; Inoue, Yukiko U.; Asami, Junko; Hoshino, Mikio; Inoue, Takayoshi

    2013-01-01

    The mammalian cerebral cortex can be tangentially subdivided into tens of functional areas with distinct cyto-architectures and neural circuitries; however, it remains elusive how these areal borders are genetically elaborated during development. Here we establish original bacterial artificial chromosome transgenic mouse lines that specifically recapitulate cadherin-6 (Cdh6) mRNA expression profiles in the layer IV of the somatosensory cortex and by detailing their cortical development, we show that a sharp Cdh6 gene expression boundary is formed at a mediolateral coordinate along the cortical layer IV as early as the postnatal day 5 (P5). By further applying mouse genetics that allows rigid cell fate tracing with CreERT2 expression, it is demonstrated that the Cdh6 gene expression boundary set at around P4 eventually demarcates the areal border between the somatosensory barrel and limb field at P20. In the P6 cortical cell pellet culture system, neurons with Cdh6 expression preferentially form aggregates in a manner dependent on Ca2+ and electroporation-based Cdh6 overexpression limited to the postnatal stages perturbs area-specific cell organization in the barrel field. These results suggest that Cdh6 expression in the nascent cortical plate may serve solidification of the protomap for cortical functional areas. PMID:22875867

  16. A compact non-differential approach for modeling laser ablation plasma dynamics

    NASA Astrophysics Data System (ADS)

    Irimiciuc, S. A.; Gurlui, S.; Nica, P.; Focsa, C.; Agop, M.

    2017-02-01

    Various differentiable physical models are frequently used to describe the dynamics of laser-produced plasma plumes (e.g., kinetic models, two-fluid models, etc.). Given the complexity of all the phenomena involved in the laser-matter interactions, it is required to introduce the laser ablation plasma dynamic variable dependencies both on the space-time coordinates and on the resolution scales. Therefore, an adequate theoretical approach may be the use of non-differentiable physical models (fractal models). Continuing our previous work on the fractal hydrodynamic model for laser ablation plasma dynamics, we propose here a compact version for the analysis of the spatial and temporal evolution of some plasma dynamic variables, such as velocities, currents, number densities, or temperatures. Moreover, the influence of external factors on the ablation plasma dynamics is considered. The predictions of this model are compared with the experimental data obtained by using a Langmuir probe on an Aluminum laser-produced plasma.

  17. Quantitative Analysis of Plasma Ablation Using Inverse Wire Array Z-pinches

    SciTech Connect

    Harvey-Thompson, A. J.; Lebedev, S. V.; Bland, S. N.; Chittenden, J. P.; Hall, G. N.; Ning, C.; Suzuki-Vidal, F.; Bott, S. C.

    2009-01-21

    An inverse (exploding) wire array configuration, in which the wires form a cylinder around a current carrying electrode on axis, was used to study the ablation phase of the pinch. This configuration allows the parameters of the plasma from individual wires of the array to be measured as the ablated plasma streams propagate in the outward radial direction. The density distribution and the evolution of the natural mode of modulation of the ablation was measured with interferometry and soft x-ray imaging. Measurements of the voltage across the array, which in this configuration is determined by the private magnetic flux around the individual wires, allows information on the localisation of the current to be obtained.

  18. Investigation of low-cost ablative heat shield fabrication for space shuttles

    NASA Technical Reports Server (NTRS)

    Chandler, H. H.

    1972-01-01

    Improvements in the processes and design to reduce the manufacturing costs for low density ablative panels for the space shuttle are discussed. The areas that were studied included methods of loading honeycomb core, alternative reinforcement concepts, and the use of reusable subpanels. A review of previous studies on the fabrication of low-cost ablative panels and on permissible defects that do not affect thermal performance was conducted. Considerable differences in the quoted prices for ablative panels, even though the various contractors had reported similar fabrication times were discovered. How these cost differences arise from different estimating criteria and which estimating assumptions and other costs must be included in order to arrive at a realistic price are discussed.

  19. Confinement effect of laser ablation plume in liquids probed by self-absorption of C{sub 2} Swan band emission

    SciTech Connect

    Sakka, Tetsuo; Saito, Kotaro; Ogata, Yukio H.

    2005-01-01

    The (0,0) Swan band of the C{sub 2} molecules in a laser ablation plume produced on the surface of graphite target submerged in water was used as a probe to estimate the density of C{sub 2} molecules in the plume. Observed emission spectra were reproduced excellently by introducing a self-absorption parameter to the theoretical spectral profile expected by a rotational population distribution at a certain temperature. The optical density of the ablation plume as a function of time was determined as a best-fit parameter by the quantitative fitting of the whole spectral profile. The results show high optical densities for the laser ablation plume in water compared with that in air. It is related to the plume confinement or the expansion, which are the important phenomena influencing the characteristics of laser ablation plumes in liquids.

  20. Laser ablation in analytical chemistry - A review

    SciTech Connect

    Russo, Richard E.; Mao, Xianglei; Liu, Haichen; Gonzalez, Jhanis; Mao, Samuel S.

    2001-10-10

    Laser ablation is becoming a dominant technology for direct solid sampling in analytical chemistry. Laser ablation refers to the process in which an intense burst of energy delivered by a short laser pulse is used to sample (remove a portion of) a material. The advantages of laser ablation chemical analysis include direct characterization of solids, no chemical procedures for dissolution, reduced risk of contamination or sample loss, analysis of very small samples not separable for solution analysis, and determination of spatial distributions of elemental composition. This review describes recent research to understand and utilize laser ablation for direct solid sampling, with emphasis on sample introduction to an inductively coupled plasma (ICP). Current research related to contemporary experimental systems, calibration and optimization, and fractionation is discussed, with a summary of applications in several areas.

  1. Physical processes of laser tissue ablation

    NASA Astrophysics Data System (ADS)

    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.

  2. Evolving Ablative Therapies for Hepatic Malignancy

    PubMed Central

    Hochwald, Steven N.

    2014-01-01

    The liver is a common site for both primary and secondary malignancy. Hepatic resection and transplantation are the two treatment modalities that have been shown to achieve complete cure, but only 10 to 20% of patients are candidates for these treatments. For the remaining patients, tumor ablation has emerged as the most promising alternative modality. In addition to providing local control and improving survival outcomes, tumor ablation also helps to down stage patients for potential curative treatments, both alone as well as in combination with other treatments. While tumor ablation can be achieved in multiple ways, the introduction of newer ablative techniques has shifted the focus from palliation to potentially curative treatment. Because the long-term safety and survival benefits are not substantive at present, it is important that we strive to evaluate the results from these studies using appropriate comparative outcome methodologies. PMID:24877069

  3. Thermal Ablation Modeling for Silicate Materials

    NASA Technical Reports Server (NTRS)

    Chen, Yih-Kanq

    2016-01-01

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

  4. Pharmacological Tests in Atrial Fibrillation Ablation

    PubMed Central

    Gourraud, Jean-Baptiste; Andrade, Jason G; Macle, Laurent

    2016-01-01

    The invasive management of atrial fibrillation (AF) has been considerably changed by the identification of major sites of AF initiation and/or maintenance within the pulmonary vein antra. Percutaneous catheter ablation of these targets has become the standard of care for sustained maintenance of sinus rhythm. Long-term failure of ablation is related to an inability to create a durable transmural lesion or to identify all of the non-pulmonary vein arrhythmia triggers. Pharmacological challenges during catheter ablation have been suggested to improve outcomes in both paroxysmal and persistent AF. Herein we review the mechanism and evidence for the use of pharmacological adjuncts during the catheter ablation of AF. PMID:28116081

  5. Microwave Tissue Ablation: Biophysics, Technology and Applications

    PubMed Central

    2010-01-01

    Microwave ablation is an emerging treatment option for many cancers, cardiac arrhythmias and other medical conditions. During treatment, microwaves are applied directly to tissues to produce rapid temperature elevations sufficient to produce immediate coagulative necrosis. The engineering design criteria for each application differ, with individual consideration for factors such as desired ablation zone size, treatment duration, and procedural invasiveness. Recent technological developments in applicator cooling, power control and system optimization for specific applications promise to increase the utilization of microwave ablation in the future. This article will review the basic biophysics of microwave tissue heating, provide an overview of the design and operation of current equipment, and outline areas for future research for microwave ablation. PMID:21175404

  6. Indications and options for endometrial ablation.

    PubMed

    2008-11-01

    Endometrial ablation is an effective therapeutic option for the management of menorrhagia in properly selected patients. Hysteroscopic and non-hysteroscopic techniques offer similar rates of symptom relief and patient satisfaction.

  7. Percutaneous ablation of malignant thoracic tumors.

    PubMed

    Ghaye, B

    2013-01-01

    Lung cancer is the leading cause of death related to cancer. Fifteen to thirty percent of patients with a localized lung cancer are actually inoperable as they present with poor general condition, limited cardiopulmonary function, or a too high surgical risk. Therefore, minimally invasive treatments are needed and percutaneous ablation seems an attractive option. Thermal ablation can be performed by delivering heat (radiofrequency, microwave, laser) or cold (cryotherapy) through a needle inserted into the tumor under CT guidance. The ideal lesion is less than 2 or 3 cm in diameter. Success of percutaneous thermal ablation appears to be close to those of surgery for localized lung cancer. Nevertheless studies are still needed to definitely assess the role of ablation compared to other emerging techniques, as stereotactic radiotherapy as well as potential synergy with other treatments.

  8. Flexible Ablators: Applications and Arcjet Testing

    NASA Technical Reports Server (NTRS)

    Arnold, James O.; Venkatapathy, Ethiraj; Beck, Robin A S.; Mcguire, Kathy; Prabhu, Dinesh K.; Gorbunov, Sergey

    2011-01-01

    Flexible ablators were conceived in 2009 to meet the technology pull for large, human Mars Exploration Class, 23 m diameter hypersonic inflatable aerodynamic decelerators. As described elsewhere, they have been recently undergoing initial technical readiness (TRL) advancement by NASA. The performance limits of flexible ablators in terms of maximum heat rates, pressure and shear remain to be defined. Further, it is hoped that this emerging technology will vastly expand the capability of future NASA missions involving atmospheric entry systems. This paper considers four topics of relevance to flexible ablators: (1) Their potential applications to near/far term human and robotic missions (2) Brief consideration of the balance between heat shield diameter, flexible ablator performance limits, entry vehicle controllability and aft-body shear layer impingement of interest to designers of very large entry vehicles, (3) The approach for developing bonding processes of flexible ablators for use on rigid entry bodies and (4) Design of large arcjet test articles that will enable the testing of flexible ablators in flight-like, combined environments (heat flux, pressure, shear and structural tensile loading). Based on a review of thermal protection system performance requirements for future entry vehicles, it is concluded that flexible ablators have broad applications to conventional, rigid entry body systems and are enabling to large deployable (both inflatable and mechanical) heat shields. Because of the game-changing nature of flexible ablators, it appears that NASA's Office of the Chief Technologist (OCT) will fund a focused, 3-year TRL advancement of the new materials capable of performance in heat fluxes in the range of 200-600 W/sq. cm. This support will enable the manufacture and use of the large-scale arcjet test designs that will be a key element of this OCT funded activity.

  9. Resonant laser ablation: mechanisms and applications

    SciTech Connect

    Anderson, J.E.; Allen, T.M.; Garrett, A.W.; Gill, C.G.; Hemberger, P.H.; Kelly, P.B.; Nogar, N.S.

    1996-10-01

    We report on aspects of resonant laser ablation (RLA) behavior for a number of sample types: metals, alloys, thin films, zeolites and soil. The versatility of RLA is demonstrated, with results on a variety of samples and in several mass spectrometers. In addition, the application to depth profiling of thin films is described; absolute removal rates and detection limits are also displayed. A discussion of possible mechanisms for low-power ablation is presented.

  10. Percutaneous ablation of colorectal lung metastases

    PubMed Central

    Solomon, Stephen B.

    2015-01-01

    Lung metastasectomy can prolong survival in patients with metastatic colorectal carcinoma. Thermal ablation offers a potential solution with similar reported survival outcomes. It has minimal effect on pulmonary function, or quality of life, can be repeated, and may be considered more acceptable to patients because of the associated shorter hospital stay and recovery. This review describes the indications, technique, reported outcomes, complications and radiologic appearances after thermal ablation of colorectal lung metastases. PMID:26697202

  11. Sharp Interface Algorithm for Large Density Ratio Incompressible Multiphase Magnetohydrodynamic Flows

    DTIC Science & Technology

    2013-01-01

    neutrino factory, ablation of pellets in tokamaks, and processes in hybrid magnetoinertial fusion. Sharp Interface Algorithm for Large Density Rati...for the proposed muon collider / neutrino factory, ablation of pellets in tokamaks, and processes in hybrid magnetoinertial fusion. Keywords: Front

  12. Laser Ablated Carbon Nanodots for Light Emission.

    PubMed

    Reyes, Delfino; Camacho, Marco; Camacho, Miguel; Mayorga, Miguel; Weathers, Duncan; Salamo, Greg; Wang, Zhiming; Neogi, Arup

    2016-12-01

    The synthesis of fluorescent carbon dots-like nanostructures (CNDs) obtained through the laser ablation of a carbon solid target in liquid environment is reported. The ablation process was induced in acetone with laser pulses of 1064, 532, and 355 nm under different irradiation times. Close-spherical amorphous CNDs with sizes between 5 and 20 nm, whose abundance strongly depends on the ablation parameters were investigated using electron microscopy and was confirmed using absorption and emission spectroscopies. The π- π* electronic transition at 3.76 eV dominates the absorption for all the CNDs species synthesized under different irradiation conditions. The light emission is most efficient due to excitation at 3.54 eV with the photoluminescence intensity centered at 3.23 eV. The light emission from the CNDs is most efficient due to ablation at 355 nm. The emission wavelength of the CNDs can be tuned from the near-UV to the green wavelength region by controlling the ablation time and modifying the ablation and excitation laser wavelength.

  13. Pulsed HF laser ablation of dentin

    NASA Astrophysics Data System (ADS)

    Papagiakoumou, Eirini I.; Papadopoulos, Dimitris N.; Makropoulou, Mersini I.; Khabbaz, Maruan G.; Serafetinides, Alexander A.

    2005-03-01

    The interaction of a TEA (Transversally Excited Atmospheric pressure) corona preionized oscillator double amplifier HF (hydrogen fluoride) laser beam with dentin tissue is reported. Pulses of 39 ns in the wavelength range of 2.65-3.35 μm and output energies in the range of 10-45 mJ, in a predominantly TEM00 beam were used to interact with dentin tissue. Ablation experiments were conducted with the laser beam directly focused on the tissue. Several samples of freshly extracted human teeth were used, cut longitudinally in facets of about 1mm thick and stored in phosphate buffered saline after being cleaned from the soft tissue remains. The experimental data (ablation thresholds, ablation rates) are discussed with respect to the ablation mechanism(s). Adequate tissue removal was observed and the ablation behavior was, in the greates part of the available fluences, almost linear. From the microscopic examination of teh samples, in a scanning electron microscope (SEM), the irradiated surfaces displayed oval craters (reflecting the laser beam shape) with absence of any melting or carbonization zone. It is suggested that the specific laser removes hard tissue by a combined photothermal and plasma mediated ablation mechanism, leaving a surface free from thermal damage and with a well-shaped crater.

  14. ERTS-1 image enhancement by optically combining density slices

    NASA Technical Reports Server (NTRS)

    Tapper, G. O.; Pease, R. W.

    1973-01-01

    The technique of density slicing using a photographic film and its application to enhancement of ERTS-1 imagery has proved to be useful for mapping varigated areal phenomena and provides a useful supplement ot the I2S MiniAddcol viewing system. The intial experiments conducted with this film were encouraging, and indicated that this technique of density slicing using readily accessible darkroom facilities and simple darkroom procedures allows rapid, accurate, and facile interpretation of certain areal phenomena to be made from the imagery. The distribution of the tree yucca, Yucca brevifolia Jaegeriana, in the eastern Mojave Desert of Southern California and southern Nevada was used as an example to test the accuracy of the technique for mapping purposes. The distribution was mapped at a relatively high level of accuracy.

  15. Topographic organization of areas V3 and V4 and its relation to supra-areal organization of the primate visual system

    PubMed Central

    ARCARO, M.J.; KASTNER, S.

    2016-01-01

    Areas V3 and V4 are commonly thought of as individual entities in the primate visual system, based on definition criteria such as their representation of visual space, connectivity, functional response properties, and relative anatomical location in cortex. Yet, large-scale functional and anatomical organization patterns not only emphasize distinctions within each area, but also links across visual cortex. Specifically, the visuotopic organization of V3 and V4 appears to be part of a larger, supra-areal organization, clustering these areas with early visual areas V1 and V2. In addition, connectivity patterns across visual cortex appear to vary within these areas as a function of their supra-areal eccentricity organization. This complicates the traditional view of these regions as individual functional “areas.” Here, we will review the criteria for defining areas V3 and V4 and will discuss functional and anatomical studies in humans and monkeys that emphasize the integration of individual visual areas into broad, supra-areal clusters that work in concert for a common computational goal. Specifically, we propose that the visuotopic organization of V3 and V4, which provides the criteria for differentiating these areas, also unifies these areas into the supra-areal organization of early visual cortex. We propose that V3 and V4 play a critical role in this supra-areal organization by filtering information about the visual environment along parallel pathways across higher-order cortex. PMID:26241035

  16. Topographic organization of areas V3 and V4 and its relation to supra-areal organization of the primate visual system.

    PubMed

    Arcaro, M J; Kastner, S

    2015-01-01

    Areas V3 and V4 are commonly thought of as individual entities in the primate visual system, based on definition criteria such as their representation of visual space, connectivity, functional response properties, and relative anatomical location in cortex. Yet, large-scale functional and anatomical organization patterns not only emphasize distinctions within each area, but also links across visual cortex. Specifically, the visuotopic organization of V3 and V4 appears to be part of a larger, supra-areal organization, clustering these areas with early visual areas V1 and V2. In addition, connectivity patterns across visual cortex appear to vary within these areas as a function of their supra-areal eccentricity organization. This complicates the traditional view of these regions as individual functional "areas." Here, we will review the criteria for defining areas V3 and V4 and will discuss functional and anatomical studies in humans and monkeys that emphasize the integration of individual visual areas into broad, supra-areal clusters that work in concert for a common computational goal. Specifically, we propose that the visuotopic organization of V3 and V4, which provides the criteria for differentiating these areas, also unifies these areas into the supra-areal organization of early visual cortex. We propose that V3 and V4 play a critical role in this supra-areal organization by filtering information about the visual environment along parallel pathways across higher-order cortex.

  17. Quantifying Leisure Physical Activity and Its Relation to Bone Density and Strength

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Purpose: Compare three published methods of quantifying physical activity (total activity, peak strain, and bone loading exposure [BLE] scores) and identify their associations with areal bone mineral density (aBMD), volumetric BMD (vBMD), and bone strength. Methods: Postmenopausal women (N = 239; me...

  18. Dust ablation in Pluto's atmosphere

    NASA Astrophysics Data System (ADS)

    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.

  19. Radiofrequency Ablation Beyond the Liver

    PubMed Central

    Neeman, Ziv; Wood, Bradford J.

    2008-01-01

    Radiofrequency ablation (RFA) has begun to show promise for extrahepatic indications. Although much of the reported work on image-guided RFA of liver neoplasms is quite promising, it is even earlier in the evaluation and validation process for extrahepatic RFA, with few short-term and no long-term studies reported. Although there are much more data for liver RFA with almost 3,000 cases reported in the literature, there are a number of ongoing investigations of RFA for tumors in the kidney, lung, bone, breast, bone, and adrenal gland. Debulking and pain control with RFA present palliative options becoming increasingly popular weapons in the interventionalist's oncology arsenal. Metastatic disease with a wide variety of primary histologies in a myriad of locations may be treated with RFA after a careful consideration of the risk-to-benefit ratio balance. The RFA technique can be slightly different outside the liver. Specifically, differing dielectric tissue characteristics may markedly alter the RFA treatment. Each different RFA system has a unique risk and advantage profile. Extrahepatic indications and contraindications will be suggested. Treatment tips and the unique complications and considerations will be introduced for some of the more common extrahepatic locations. PMID:12524646

  20. Plans and status of the Beryllium ablator campaign on NIF

    NASA Astrophysics Data System (ADS)

    Kline, J. L.; Yi, S. A.; Simakov, A. N.; Wilson, D. C.; Olson, R. E.; Krasheninnikova, N. S.; Kyrala, G. A.; Perry, T. S.; Batha, S. H.; Dewald, E. L.; Edwards, M. J.; MacKinnon, A. J.; Meezan, N. B.

    2014-10-01

    Beryllium has long been known to have excellent properties for indirectly driven ICF implosions including enhanced ablation pressure, implosion velocity, and mass ablation rate. The high ablation velocity leads to stabilization of ablative hydrodynamic instabilities and higher ablation pressures. Recent ``high foot'' experiments have shown ablative Rayleigh-Taylor to be a leading cause of degraded performance for ICF implosions. While Beryllium ablators have these advantages, there are also risks associated with Beryllium target designs. A campaign is underway to design and to test these advantages for comparison with other ablator options and determine which provides the best path forward for ICF. Experiments using Beryllium ablators are expected to start in the late summer of 2014. This presentation will discuss the status of the experiments and layout the plans/goals for the campaign. This work is supported by the US DOE.

  1. Percutaneous Microwave Ablation of Renal Angiomyolipomas

    SciTech Connect

    Cristescu, Mircea; Abel, E. Jason; Wells, Shane Ziemlewicz, Timothy J.; Hedican, Sean P.; Lubner, Megan G. Hinshaw, J. Louis Brace, Christopher L. Lee, Fred T.

    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.

  2. A systematic review of surgical ablation versus catheter ablation for atrial fibrillation

    PubMed Central

    Kearney, Katherine; Stephenson, Rowan; Phan, Kevin; Chan, Wei Yen; Huang, Min Yin

    2014-01-01

    Background Atrial fibrillation (AF) is an increasingly prevalent condition in the ageing population, with significantly associated morbidity and mortality. Surgical and catheter ablative strategies both aim to reduce mortality and morbidity through freedom from AF. This review consolidates all currently available comparative data to evaluate these two interventions. Methods A systematic search was conducted across MEDLINE, PubMed, Embase, Cochrane Central Register of Controlled Trials and the Cochrane Database of Systematic Reviews from January 2000 until August 2013. All studies were critically appraised and only those directly comparing surgical and catheter ablation were included. Results Seven studies were deemed suitable for analysis according to the inclusion criteria. Freedom from AF was significantly higher in the surgical ablation group versus the catheter ablation group at 6-month, 12-month and study endpoint follow-up periods. Subgroup analysis demonstrated similar trends, with higher freedom from AF in the surgical ablation group for paroxysmal AF patients. The incidence of pacemaker implantation was higher, while no difference in stroke or cardiac tamponade was demonstrated for the surgical versus catheter ablation groups. Conclusions Current evidence suggests that epicardial ablative strategies are associated with higher freedom from AF, higher pacemaker implantation rates and comparable neurological complications and cardiac tamponade incidence to catheter ablative treatment. Other complications and risks were poorly reported, which warrants further randomized controlled trials (RCTs) of adequate power and follow-up duration. PMID:24516794

  3. Weakly Regular Einstein-Euler Spacetimes with Gowdy Symmetry: The Global Areal Foliation

    NASA Astrophysics Data System (ADS)

    Grubic, Nastasia; LeFloch, Philippe G.

    2013-05-01

    We consider weakly regular Gowdy-symmetric spacetimes on T 3 satisfying the Einstein-Euler equations of general relativity, and we solve the initial value problem when the initial data set has bounded variation, only so that the corresponding spacetime may contain impulsive gravitational waves as well as shock waves. By analyzing both future expanding and future contracting spacetimes, we establish the existence of a global foliation by spacelike hypersurfaces so that the time function coincides with the area of the surfaces of symmetry and asymptotically approaches infinity in the expanding case and zero in the contracting case. More precisely, the latter property in the contracting case holds provided the mass density does not exceed a certain threshold, which is a natural assumption since certain exceptional data with sufficiently large mass density are known to give rise to a Cauchy horizon, on which the area function attains a positive value. An earlier result by LeFloch and Rendall assumed a different class of weak regularity and did not determine the range of the area function in the contracting case. Our method of proof is based on a version of the random choice scheme adapted to the Einstein equations for the symmetry and regularity class under consideration. We also analyze the Einstein constraint equations under weak regularity.

  4. Online monitoring of nanoparticles formed during nanosecond laser ablation

    NASA Astrophysics Data System (ADS)

    Nováková, Hana; Holá, Markéta; Vojtíšek-Lom, Michal; Ondráček, Jakub; Kanický, Viktor

    2016-11-01

    The particle size distribution of dry aerosol originating from laser ablation of glass material was monitored simultaneously with Laser Ablation - Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) analysis and two aerosol spectrometers - Fast Mobility Particle Sizer (FMPS) and Aerodynamic Particle Sizer (APS). The unique combination of LA-ICP-MS and FMPS offers the possibility of measuring the particle size distribution every 1 s of the ablation process in the size range of 5.6-560 nm. APS extends the information about particle concentration in the size range 0.54-17 μm. Online monitoring of the dry aerosol was performed for two ablation modes (spot and line with a duration of 80 s) with a 193 nm excimer laser system, using the glass reference material NIST 610 as a sample. Different sizes of laser spot for spot ablation and different scan speeds for line ablation were tested. It was found that the FMPS device is capable of detecting changes in particle size distribution at the first pulses of spot laser ablation and is suitable for laser ablation control simultaneously with LA-ICP-MS analysis. The studied parameters of laser ablation have an influence on the resulting particle size distribution. The line mode of laser ablation produces larger particles during the whole ablation process, while spot ablation produces larger particles only at the beginning, during the ablation of the intact layer of the ablated material. Moreover, spot ablation produces more primary nano-particles (in ultrafine mode size range < 100 nm) than line ablation. This effect is most probably caused by a reduced amount of large particles released from the spot ablation crater. The larger particles scavenge the ultrafine particles during the line ablation mode.

  5. Ablation from calving and surface melt at lake-terminating Bridge Glacier, British Columbia, 1984-2013

    NASA Astrophysics Data System (ADS)

    Chernos, M.; Koppes, M.; Moore, R. D.

    2016-01-01

    Bridge Glacier is a lake-calving glacier in the Coast Mountains of British Columbia and has retreated over 3.55 km since 1972. The majority of this retreat has occurred since 1991. This retreat is substantially greater than what has been inferred from regional climate indices, suggesting that it has been driven primarily by calving as the glacier retreated across an overdeepened basin. In order to better understand the primary drivers of ablation, surface melt (below the equilibrium line altitude, ELA) and calving were quantified during the 2013 melt season using a distributed energy balance model (DEBM) and time-lapse imagery. Calving, estimated using areal change, velocity measurements, and assuming flotation were responsible for 23 % of the glacier's ablation below the ELA during the 2013 melt season and were limited by modest flow speeds and a small terminus cross-section. Calving and surface melt estimates from 1984 to 2013 suggest that calving was consistently a smaller contributor of ablation. Although calving was estimated to be responsible for up to 49 % of the glacier's ablation for individual seasons, averaged over multiple summers it accounted between 10 and 25 %. Calving was enhanced primarily by buoyancy and water depths, and fluxes were greatest between 2005 and 2010 as the glacier retreated over the deepest part of Bridge Lake. The recent rapid rate of calving is part of a transient stage in the glacier's retreat and is expected to diminish within 10 years as the terminus recedes into shallower water at the proximal end of the lake. These findings are in line with observations from other lake-calving glacier studies across the globe and suggest a common large-scale pattern in calving-induced retreat in lake-terminating alpine glaciers. Despite enhancing glacial retreat, calving remains a relatively small component of ablation and is expected to decrease in importance in the future. Hence, surface melt remains the primary driver of ablation at Bridge

  6. Contact pulsed Nd:YAG ablation of human dentin: ablation rates and tissue effects

    NASA Astrophysics Data System (ADS)

    Harris, David M.; Yessik, Michael J.

    1994-09-01

    Dentin from freshly extracted human teeth was exposed to flashlamp pumped Nd:YAG pulses (100 microsecond(s) duration, 50 - 200 mJ/pulse) delivered through a flat cut fiberoptic in contact with the dentin surface. Ablation depth and volume were measured optically and confirmed with electron microscope morphometrics. Ablation depth increased with force applied at the fiber tip up to 5 - 10 g. Above this ablation depths were insensitive to applied force. Craters made in dental stone were deeper and narrower than those made in normal dentin. Ablation depths per pulse and volumes per pulse decrease as the number of pulses increase. This is more prominent for 200 mJ pulses. At 60 mJ the ablation depths are the same from 10 to 100 Hz repetition rates, although qualitative changes (collateral damage) are greater at higher repetition rates. A progressive increase in collateral damage is seen from the 1st through the 200th pulse.

  7. Modeling of ablation threshold dependence on pulse duration for dielectrics with ultrashort pulsed laser

    NASA Astrophysics Data System (ADS)

    Sun, Mingying; Zhu, Jianqiang; Lin, Zunqi

    2017-01-01

    We present a numerical model of plasma formation in ultrafast laser ablation on the dielectrics surface. Ablation threshold dependence on pulse duration is predicted with the model and the numerical results for water agrees well with the experimental data for pulse duration from 140 fs to 10 ps. Influences of parameters and approximations of photo- and avalanche-ionization on the ablation threshold prediction are analyzed in detail for various pulse lengths. The calculated ablation threshold is strongly dependent on electron collision time for all the pulse durations. The complete photoionization model is preferred for pulses shorter than 1 ps rather than the multiphoton ionization approximations. The transition time of inverse bremsstrahlung absorption needs to be considered when pulses are shorter than 5 ps and it can also ensure the avalanche ionization (AI) coefficient consistent with that in multiple rate equations (MREs) for pulses shorter than 300 fs. The threshold electron density for AI is only crucial for longer pulses. It is reasonable to ignore the recombination loss for pulses shorter than 100 fs. In addition to thermal transport and hydrodynamics, neglecting the threshold density for AI and recombination could also contribute to the disagreements between the numerical and the experimental results for longer pulses.

  8. The role of laser wavelength on plasma generation and expansion of ablation plumes in air

    NASA Astrophysics Data System (ADS)

    Hussein, A. E.; Diwakar, P. K.; Harilal, S. S.; Hassanein, A.

    2013-04-01

    We investigated the role of excitation laser wavelength on plasma generation and the expansion and confinement of ablation plumes at early times (0-500 ns) in the presence of atmospheric pressure. Fundamental, second, and fourth harmonic radiation from Nd:YAG laser was focused on Al target to produce plasma. Shadowgraphy, fast photography, and optical emission spectroscopy were employed to analyze the plasma plumes, and white light interferometry was used to characterize the laser ablation craters. Our results indicated that excitation wavelength plays a crucial role in laser-target and laser-plasma coupling, which in turn affects plasma plume morphology and radiation emission. Fast photography and shadowgraphy images showed that plasmas generated by 1064 nm are more cylindrical compared to plasmas generated by shorter wavelengths, indicating the role of inverse bremsstrahlung absorption at longer laser wavelength excitation. Electron density estimates using Stark broadening showed higher densities for shorter wavelength laser generated plasmas, demonstrating the significance of absorption caused by photoionization. Crater depth analysis showed that ablated mass is significantly higher for UV wavelengths compared to IR laser radiation. In this experimental study, the use of multiple diagnostic tools provided a comprehensive picture of the differing roles of laser absorption mechanisms during ablation.

  9. Responses of polymers to laser plasma EUV light beyond ablation threshold and micromachining

    NASA Astrophysics Data System (ADS)

    Makimura, Tetsuya; Torii, Shuichi; Okazaki, Kota; Nakamura, Daisuke; Takahashi, Akihiko; Niino, Hiroyuki; Okada, Tatsuo; Murakami, Kouichi

    2011-06-01

    We have investigated responses of PDMS, PMMA and acrylic block copolymers (BCP) to EUV light from laserproduced plasma beyond ablation thresholds and micromachining. We generated wide band EUV light around 100 eV by irradiation of Ta targets with Nd:YAG laser light. In addition, narrow band EUV light at 11 and 13 nm were generated by irradiation of solid Xe and Sn targets, respectively, with pulsed CO2 laser light. The generated EUV light was condensed onto samples, using an ellipsoidal mirror. The EUV light was incident through windows of contact masks on the samples. We found that through-holes with a diameter of 1 μm can be fabricated in PDMS sheets with thicknesses of 10 μm. PDMS sheets are ablated if they are irradiated with EUV light beyond a threshold power density, while PDMS surfaces were modified by irradiation with the narrow band EUV light at lower power densities. Effective ablation of PMMA sheets can be applied to a LIGA-like process for fabricating micro-structures of metals using the practical apparatus. Furthermore, BCP sheets were ablated to have micro-structures. Thus, we have developed a practical technique for microma chining of PMMA, PDMS and BCP sheets in a micrometer scale.

  10. The role of laser wavelength on plasma generation and expansion of ablation plumes in air

    SciTech Connect

    Hussein, A. E.; Diwakar, P. K.; Harilal, S. S.; Hassanein, A.

    2013-04-14

    We investigated the role of excitation laser wavelength on plasma generation and the expansion and confinement of ablation plumes at early times (0-500 ns) in the presence of atmospheric pressure. Fundamental, second, and fourth harmonic radiation from Nd:YAG laser was focused on Al target to produce plasma. Shadowgraphy, fast photography, and optical emission spectroscopy were employed to analyze the plasma plumes, and white light interferometry was used to characterize the laser ablation craters. Our results indicated that excitation wavelength plays a crucial role in laser-target and laser-plasma coupling, which in turn affects plasma plume morphology and radiation emission. Fast photography and shadowgraphy images showed that plasmas generated by 1064 nm are more cylindrical compared to plasmas generated by shorter wavelengths, indicating the role of inverse bremsstrahlung absorption at longer laser wavelength excitation. Electron density estimates using Stark broadening showed higher densities for shorter wavelength laser generated plasmas, demonstrating the significance of absorption caused by photoionization. Crater depth analysis showed that ablated mass is significantly higher for UV wavelengths compared to IR laser radiation. In this experimental study, the use of multiple diagnostic tools provided a comprehensive picture of the differing roles of laser absorption mechanisms during ablation.

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

    NASA Astrophysics Data System (ADS)

    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.

  12. Radioiodine Remnant Ablation: A Critical Review

    PubMed Central

    Bal, Chandra Sekhar; Padhy, Ajit Kumar

    2015-01-01

    Radioiodine remnant ablation (RRA) is considered a safe and effective method for eliminating residual thyroid tissue, as well as microscopic disease if at all present in thyroid bed following thyroidectomy. The rationale of RRA is that in the absence of thyroid tissue, serum thyroglobulin (Tg) measurement can be used as an excellent tumor marker. Other considerations are like the presence of significant remnant thyroid tissue makes detection and treatment of nodal or distant metastases difficult. Rarely, microscopic disease in the thyroid bed if not ablated, in the future, could be a source of anaplastic transformation. On the other hand, microscopic tumor emboli in distant sites could be the cause of distant metastasis too. The ablation of remnant tissue would in all probability eliminate these theoretical risks. It may be noted that all these are unproven contentious issues except postablation serum Tg estimation that could be a good tumor marker for detecting early biochemical recurrence in long-term follow-up strategy. Radioactive iodine is administered as a form of “adjuvant therapy” for remnant ablation. There have been several reports with regard to the administered dose for remnant ablation. The first report of a prospective randomized clinical trial was published from India by a prospective randomized study conducted at the All India Institute of Medical Sciences, New Delhi in the year 1996. The study reported that increasing the empirical 131I initial dose to more than 50 mCi results in plateauing of the dose-response curve and thus, conventional high-dose remnant ablation needs critical evaluation. Recently, two important studies were published: One from French group and the other from UK on a similar line. Interestingly, all three studies conducted in three different geographical regions of the world showed exactly similar conclusion. The new era of low-dose remnant ablation has taken a firm scientific footing across the continents. PMID:26420983

  13. Photoacoustic characterization of radiofrequency ablation lesions

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  14. Catheter Ablation of Fascicular Ventricular Tachycardia

    PubMed Central

    Liu, Yaowu; Fang, Zhen; Yang, Bing; Kojodjojo, Pipin; Chen, Hongwu; Ju, Weizhu; Cao, Kejiang; Chen, Minglong

    2015-01-01

    Background— Fascicular ventricular tachycardia (FVT) is a common form of sustained idiopathic left ventricular tachycardia with an Asian preponderance. This study aimed to prospectively investigate long-term clinical outcomes of patients undergoing ablation of FVT and identify predictors of arrhythmia recurrence. Methods and Results— Consecutive patients undergoing FVT ablation at a single tertiary center were enrolled. Activation mapping was performed to identify the earliest presystolic Purkinje potential during FVT that was targeted by radiofrequency ablation. Follow-up with clinic visits, ECG, and Holter monitoring was performed at least every 6 months. A total of 120 consecutive patients (mean age, 29.3±12.7 years; 82% men; all patients with normal ejection fraction) were enrolled. FVT involved left posterior fascicle and left anterior fascicle in 118 and 2 subjects, respectively. VT was noninducible in 3 patients, and ablation was acutely successful in 117 patients. With a median follow-up of 55.7 months, VT of a similar ECG morphology recurred in 17 patients, and repeat procedure confirmed FVT recurrence involving the same fascicle. Shorter VT cycle length was the only significant predictor of FVT recurrence (P=0.03). Six other patients developed new-onset upper septal FVT that was successfully ablated. Conclusions— Ablation of FVT guided by activation mapping is associated with a single procedural success rate without the use of antiarrhythmic drugs of 80.3%. Arrhythmia recurrences after an initially successful ablation were caused by recurrent FVT involving the same fascicle in two thirds of patients or new onset of upper septal FVT in the remainder. PMID:26386017

  15. Determination of areal sedimentation rates in rivers by using plate sediment trap measurements and flow velocity-settling flux relationship.

    PubMed

    Kozerski, Hans-Peter

    2002-07-01

    Not much is known about sedimentation of organic particles in rivers. Plate sediment traps deployed in fast flowing River Spree and in a slowly flowing side arm yielded trapping rates between 0.7 and 52gDW m(-2) d(-1). A linear regression between flow velocity and trapping rates was used to extrapolate from point measurements to areal average trapping rates, which were 11 gDW m(-2) d(-1) in the side arm and 1.4 gDW m(-2) d(-1) in the free flowing river section. These rates are typical for the River Spree, but different from other rivers. The plate trap measurements provide the basic variables for the sedimentation rate sed = C x W*s(1-V/V(crit,sed)), i.e. concentration of particles (C), sinking velocity (Ws) flow velocity (V), and a threshold velocity (V(crit,sed)).

  16. Buckling in serpentine microstructures and applications in elastomer-supported ultra-stretchable electronics with high areal coverage.

    PubMed

    Zhang, Yihui; Xu, Sheng; Fu, Haoran; Lee, Juhwan; Su, Jessica; Hwang, Keh-Chih; Rogers, John A; Huang, Yonggang

    2013-01-01

    Lithographically defined electrical interconnects with thin, filamentary serpentine layouts have been widely explored for use in stretchable electronics supported by elastomeric substrates. We present a systematic and thorough study of buckling physics in such stretchable serpentine microstructures, and a strategic design of serpentine layout for ultra-stretchable electrode, via analytical models, finite element method (FEM) computations, and quantitative experiments. Both the onset of buckling and the postbuckling behaviors are examined, to determine scaling laws for the critical buckling strain and the limits of elastic behavior. Two buckling modes, namely the symmetric and anti-symmetric modes, are identified and analyzed, with experimental images and numerical results that show remarkable levels of agreement for the associated postbuckling processes. Based on these studies and an optimization in design layout, we demonstrate routes for application of serpentine interconnects in an ultra-stretchable electrode that offer, simultaneously, an areal coverage as high as 81%, and a biaxial stretchability as large as ~170%.

  17. Enabling high areal capacitance in electrochemical double layer capacitors by means of the environmentally friendly starch binder

    NASA Astrophysics Data System (ADS)

    Varzi, Alberto; Passerini, Stefano

    2015-12-01

    Potatoes starch (PS), a natural polymer obtainable from non-edible sources, is for the first time evaluated as alternative water-processable binder for Electrochemical Double-Layer Capacitor (EDLC) electrodes. Morphological and electrochemical properties of activated carbon (AC)-based electrodes are investigated and compared to those achieved with the state-of-the-art aqueous binder (CMC, i.e. Na-carboxymethyl cellulose). The obtained results suggest substantial benefits of PS, in particular regarding the electrode fabrication process. As a matter of fact, owing to its amylopectin content (moderately branched polysaccharide), PS displays only minimal shrinkage upon drying, resulting on rather homogeneous electrodes not presenting the dramatic surface cracking observed with CMC. Furthermore, owing to the smaller volume of water required for the processing, much higher active material loading per area unit can be achieved. This is reflected on improvements of up to 60% in terms of areal capacitance.

  18. Buckling in serpentine microstructures and applications in elastomer-supported ultra-stretchable electronics with high areal coverage

    PubMed Central

    Zhang, Yihui; Xu, Sheng; Fu, Haoran; Lee, Juhwan; Su, Jessica; Hwang, Keh-Chih; Rogers, John A.; Huang, Yonggang

    2014-01-01

    Lithographically defined electrical interconnects with thin, filamentary serpentine layouts have been widely explored for use in stretchable electronics supported by elastomeric substrates. We present a systematic and thorough study of buckling physics in such stretchable serpentine microstructures, and a strategic design of serpentine layout for ultra-stretchable electrode, via analytical models, finite element method (FEM) computations, and quantitative experiments. Both the onset of buckling and the postbuckling behaviors are examined, to determine scaling laws for the critical buckling strain and the limits of elastic behavior. Two buckling modes, namely the symmetric and anti-symmetric modes, are identified and analyzed, with experimental images and numerical results that show remarkable levels of agreement for the associated postbuckling processes. Based on these studies and an optimization in design layout, we demonstrate routes for application of serpentine interconnects in an ultra-stretchable electrode that offer, simultaneously, an areal coverage as high as 81%, and a biaxial stretchability as large as ~170%. PMID:25309616

  19. Subsurface ablation of atherosclerotic plaque using ultrafast laser pulses

    PubMed Central

    Lanvin, Thomas; Conkey, Donald B.; Frobert, Aurelien; Valentin, Jeremy; Goy, Jean-Jacques; Cook, Stéphane; Giraud, Marie-Noelle; Psaltis, Demetri

    2015-01-01

    We perform subsurface ablation of atherosclerotic plaque using ultrafast pulses. Excised mouse aortas containing atherosclerotic plaque were ablated with ultrafast near-infrared (NIR) laser pulses. Optical coherence tomography (OCT) was used to observe the ablation result, while the physical damage was inspected in histological sections. We characterize the effects of incident pulse energy on surface damage, ablation hole size, and filament propagation. We find that it is possible to ablate plaque just below the surface without causing surface damage, which motivates further investigation of ultrafast ablation for subsurface atherosclerotic plaque removal. PMID:26203381

  20. Subsurface ablation of atherosclerotic plaque using ultrafast laser pulses.

    PubMed

    Lanvin, Thomas; Conkey, Donald B; Frobert, Aurelien; Valentin, Jeremy; Goy, Jean-Jacques; Cook, Stéphane; Giraud, Marie-Noelle; Psaltis, Demetri

    2015-07-01

    We perform subsurface ablation of atherosclerotic plaque using ultrafast pulses. Excised mouse aortas containing atherosclerotic plaque were ablated with ultrafast near-infrared (NIR) laser pulses. Optical coherence tomography (OCT) was used to observe the ablation result, while the physical damage was inspected in histological sections. We characterize the effects of incident pulse energy on surface damage, ablation hole size, and filament propagation. We find that it is possible to ablate plaque just below the surface without causing surface damage, which motivates further investigation of ultrafast ablation for subsurface atherosclerotic plaque removal.

  1. New tumor ablation techniques for cancer treatment (microwave, electroporation).

    PubMed

    de Baere, T; Deschamps, F

    2014-01-01

    Since the introduction of radiofrequency ablation (RFA) for the treatment of liver tumors at the end of the 1990s, indications for local ablation techniques have been extended to other organs, in particular, the lungs, kidneys and bones. These techniques have also been improved, in particular to try and overcome the limitations of radiofrequency techniques, especially the significant decrease in complete ablation rates for tumors larger than 3cm and tumors that are contiguous to vessels larger than 3mm. Microwave ablation is a rapidly developing thermal ablation technique similar to RFA but with numerous differences. Electroporation, a non-thermal ablation technique with other possibilities, is in earlier stages of clinical development.

  2. Areal Changes of Lentic Water Bodies Within an Agricultural Basin of the Argentinean Pampas. Disentangling Land Management from Climatic Causes

    NASA Astrophysics Data System (ADS)

    Booman, Gisel Carolina; Calandroni, Mirta; Laterra, Pedro; Cabria, Fabián; Iribarne, Oscar; Vázquez, Pablo

    2012-12-01

    Wetland loss is a frequent concern for the environmental management of rural landscapes, but poor disentanglement between climatic and land management causes frequently constrains both proper diagnoses and planning. The aim of this study is to address areal changes induced by non-climatic factors on lentic water bodies (LWB) within an agricultural basin of the Argentinean Pampas, and the human activities that might be involved. The LWB of the Mar Chiquita basin (Buenos Aires province, Argentina) were mapped using Landsat images from 1998-2008 and then corrected for precipitation variability by considering the regional hydrological status on each date. LWB areal changes were statistically and spatially analyzed in relation to land use changes, channelization of streams, and drainage of small SWB in the catchment areas. We found that 12 % of the total LWB in the basin had changed ( P < 0.05) due to non-climatic causes. During the evaluated decade, 30 % of the LWB that changed size had decreased while 70 % showed steady increases in area. The number of altered LWB within watersheds lineally increased or decreased according to the proportion of grasslands replaced by sown pastures, or the proportion of sown pastures replaced by crop fields, respectively. Drainage and channelization do not appear to be related to the alteration of LWB; however some of these hydrologic modifications may predate 1998, and thus earlier effects cannot be discarded. This study shows that large-scale changes in land cover (e.g., grasslands reduction) can cause a noticeable loss of hydrologic regulation at the catchment scale within a decade.

  3. Retrieval of Areal-averaged Spectral Surface Albedo from Transmission Data Alone: Computationally Simple and Fast Approach

    SciTech Connect

    Kassianov, Evgueni I.; Barnard, James C.; Flynn, Connor J.; Riihimaki, Laura D.; Michalsky, Joseph; Hodges, G. B.

    2014-10-25

    We introduce and evaluate a simple retrieval of areal-averaged surface albedo using ground-based measurements of atmospheric transmission alone at five wavelengths (415, 500, 615, 673 and 870nm), under fully overcast conditions. Our retrieval is based on a one-line semi-analytical equation and widely accepted assumptions regarding the weak spectral dependence of cloud optical properties, such as cloud optical depth and asymmetry parameter, in the visible and near-infrared spectral range. To illustrate the performance of our retrieval, we use as input measurements of spectral atmospheric transmission from Multi-Filter Rotating Shadowband Radiometer (MFRSR). These MFRSR data are collected at two well-established continental sites in the United States supported by the U.S. Department of Energy’s (DOE’s) Atmospheric Radiation Measurement (ARM) Program and National Oceanic and Atmospheric Administration (NOAA). The areal-averaged albedos obtained from the MFRSR are compared with collocated and coincident Moderate Resolution Imaging Spectroradiometer (MODIS) white-sky albedo. In particular, these comparisons are made at four MFRSR wavelengths (500, 615, 673 and 870nm) and for four seasons (winter, spring, summer and fall) at the ARM site using multi-year (2008-2013) MFRSR and MODIS data. Good agreement, on average, for these wavelengths results in small values (≤0.01) of the corresponding root mean square errors (RMSEs) for these two sites. The obtained RMSEs are comparable with those obtained previously for the shortwave albedos (MODIS-derived versus tower-measured) for these sites during growing seasons. We also demonstrate good agreement between tower-based daily-averaged surface albedos measured for “nearby” overcast and non-overcast days. Thus, our retrieval originally developed for overcast conditions likely can be extended for non-overcast days by interpolating between overcast retrievals.

  4. Areal-averaged and Spectrally-resolved Surface Albedo from Ground-based Transmission Data Alone: Toward an Operational Retrieval

    SciTech Connect

    Kassianov, Evgueni I.; Barnard, James C.; Flynn, Connor J.; Riihimaki, Laura D.; Michalsky, Joseph; Hodges, G. B.

    2014-08-22

    We present here a simple retrieval of the areal-averaged and spectrally resolved surface albedo using only ground-based measurements of atmospheric transmission under fully overcast conditions. Our retrieval is based on a one-line equation and widely accepted assumptions regarding the weak spectral dependence of cloud optical properties in the visible and near-infrared spectral range. The feasibility of our approach for the routine determinations of albedo is demonstrated for different landscapes with various degrees of heterogeneity using three sets of measurements:(1) spectrally resolved atmospheric transmission from Multi-Filter Rotating Shadowband Radiometer (MFRSR) at wavelength 415, 500, 615, 673, and 870 nm, (2) tower-based measurements of local surface albedo at the same wavelengths, and (3) areal-averaged surface albedo at four wavelengths (470, 560, 670 and 860 nm) from collocated and coincident Moderate Resolution Imaging Spectroradiometer (MODIS) observations. These integrated datasets cover both long (2008-2013) and short (April-May, 2010) periods at the ARM Southern Great Plains (SGP) site and the NOAA Table Mountain site, respectively. The calculated root mean square error (RMSE), which is defined here as the root mean squared difference between the MODIS-derived surface albedo and the retrieved area-averaged albedo, is quite small (RMSE≤0.01) and comparable with that obtained previously by other investigators for the shortwave broadband albedo. Good agreement between the tower-based daily averages of surface albedo for the completely overcast and non-overcast conditions is also demonstrated. This agreement suggests that our retrieval originally developed for the overcast conditions likely will work for non-overcast conditions as well.

  5. Heat sink effect on tumor ablation characteristics as observed in monopolar radiofrequency, bipolar radiofrequency, and microwave, using ex vivo calf liver model.

    PubMed

    Pillai, Krishna; Akhter, Javid; Chua, Terence C; Shehata, Mena; Alzahrani, Nayef; Al-Alem, Issan; Morris, David L

    2015-03-01

    Thermal ablation of liver tumors near large blood vessels is affected by the cooling effect of blood flow, leading to incomplete ablation. Hence, we conducted a comparative investigation of heat sink effect in monopolar (MP) and bipolar (BP) radiofrequency ablation (RFA), and microwave (MW) ablation devices.With a perfused calf liver, the ablative performances (volume, mass, density, dimensions), with and without heat sink, were measured. Heat sink was present when the ablative tip of the probes were 8.0 mm close to a major hepatic vein and absent when >30 mm away. Temperatures (T1 and T2) on either side of the hepatic vein near the tip of the probes, heating probe temperature (T3), outlet perfusate temperature (T4), and ablation time were monitored.With or without heat sink, BP radiofrequency ablated a larger volume and mass, compared with MP RFA or MW ablation, with latter device producing the highest density of tissue ablated. MW ablation produced an ellipsoidal shape while radiofrequency devices produced spheres.Percentage heat sink effect in Bipolar radiofrequency : Mono-polar radiofrequency : Microwave was (Volume) 33:41:22; (mass) 23:56:34; (density) 9.0:26:18; and (relative elipscity) 5.8:12.9:1.3, indicating that BP and MW devices were less affected.Percentage heat sink effect on time (minutes) to reach maximum temperature (W) = 13.28:9.2:29.8; time at maximum temperature (X) is 87:66:16.66; temperature difference (Y) between the thermal probes (T3) and the temperature (T1 + T2)/2 on either side of the hepatic vessel was 100:87:20; and temperature difference between the (T1 + T2)/2 and temperature of outlet circulating solution (T4), Z was 20.33:30.23:37.5.MW and BP radiofrequencies were less affected by heat sink while MP RFA was the most affected. With a single ablation, BP radiofrequency ablated a larger volume and mass regardless of heat sink.

  6. Guiding and Ionization Blueshift in Ablative Capillary Waveguide Accelerators

    SciTech Connect

    McGuffey, Chris; Matsuoka, Takeshi; Bulanov, Stepan; Chvykov, Vladimir; Kalintchenko, Galina; Rousseau, Pascal; Yanovsky, Victor; Maksimchuk, Anatoly; Krushelnick, Karl; Levin, Michael; Zigler, Arie

    2009-01-22

    Laser wakefield acceleration (LWFA) in plasmas has been demonstrated with gradients which are orders of magnitude greater than the limit on conventional Radio Frequency accelerators. However, the acceleration length is limited by two factors, the dephasing length and the Rayleigh range of the laser pulse. Dephasing length is the distance in which electrons overtake the laser pulse and can be increased by decreasing plasma density. Alternatively the interaction length can be extended by orders of magnitude by using ablative wall discharge capillary targets, in which a plasma is preformed with a transverse density profile capable of guiding the focused laser. We have demonstrated guiding of high intensity laser pulses from the HERCULES laser over 3 cm for powers up to 35 TW. The quality of the laser spot can be retained and the intensity remains high even at the exit of the capillary. The transmitted laser spectrum shows blueshifting due to field ionization by the laser pulse. This ionization might enhance electron injection at low electron density for LWFA GeV accelerators. The field ionization affects carbon atoms and ions from the ablated capillary, which are not present in hydrogen-filled capillaries. This creates an additional challenge to guiding compared to hydrogen-filled capillaries. However, the setup and materials are easier to come by. The use of these capillary targets may also be of interest to other high intensity laser-plasma interactions requiring long interaction lengths such as high harmonic generation from gases and plasmas, or x-ray lasing in underdense plasmas.

  7. Approximate model for laser ablation of carbon

    NASA Astrophysics Data System (ADS)

    Shusser, Michael

    2010-08-01

    The paper presents an approximate kinetic theory model of ablation of carbon by a nanosecond laser pulse. The model approximates the process as sublimation and combines conduction heat transfer in the target with the gas dynamics of the ablated plume which are coupled through the boundary conditions at the interface. The ablated mass flux and the temperature of the ablating material are obtained from the assumption that the ablation rate is restricted by the kinetic theory limitation on the maximum mass flux that can be attained in a phase-change process. To account for non-uniform distribution of the laser intensity while keeping the calculation simple the quasi-one-dimensional approximation is used in both gas and solid phases. The results are compared with the predictions of the exact axisymmetric model that uses the conservation relations at the interface derived from the momentum solution of the Boltzmann equation for arbitrary strong evaporation. It is seen that the simpler approximate model provides good accuracy.

  8. Fracture in Phenolic Impregnated Carbon Ablator

    NASA Technical Reports Server (NTRS)

    Agrawal, Parul; Chavez-Garcia, Jose; Pham, John

    2013-01-01

    This paper describes the development of a novel technique to understand the failure mechanisms inside thermal protection materials. The focus of this research is on the class of materials known as phenolic impregnated carbon ablators. It has successfully flown on the Stardust spacecraft and is the thermal protection system material chosen for the Mars Science Laboratory and SpaceX Dragon spacecraft. Although it has good thermal properties, structurally, it is a weak material. To understand failure mechanisms in carbon ablators, fracture tests were performed on FiberForm(Registered TradeMark) (precursor), virgin, and charred ablator materials. Several samples of these materials were tested to investigate failure mechanisms at a microstructural scale. Stress-strain data were obtained simultaneously to estimate the tensile strength and toughness. It was observed that cracks initiated and grew in the FiberForm when a critical stress limit was reached such that the carbon fibers separated from the binder. However, both for virgin and charred carbon ablators, crack initiation and growth occurred in the matrix (phenolic) phase. Both virgin and charred carbon ablators showed greater strength values compared with FiberForm samples, confirming that the presence of the porous matrix helps in absorbing the fracture energy.

  9. Stark broadening measurements in plasmas produced by laser ablation of hydrogen containing compounds

    NASA Astrophysics Data System (ADS)

    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.

  10. Carbon nanocrystals produced by pulsed laser ablation of carbon

    NASA Astrophysics Data System (ADS)

    Mangione, A.; Torrisi, L.; Picciotto, A.; Caridi, F.; Margarone, D.; Fazio, E.; La Mantia, A.; di Marco, G.

    2005-10-01

    Plasma laser ablation experiments were performed irradiating glassy-carbon targets placed in vacuum through a pulsed Nd:YAG laser operating at the second harmonic (532 nm), 9 ns pulse width and 10(9) W/cm(2) density power. Thin films of ablated carbon were deposited on silicon oxide substrates placed at different distances and angles with respect to the target. The analysis of the deposited material was carried out by using surface profiler, scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and Raman spectroscopy. Results show the evidence of carbon nanocrystals and nanostructures with dimension of the order of 100 nm deposited on the substrates together with a large amount of amorphous phase. The spectroscopic investigations and the SEM images indicate the formation of nanodiamond seeds as a nucleation process induced on the substrate surface. Nanostructures were investigated as a function of the laser intensity and angle distribution. Experimental results were compared with the literature data coming from nanodiamonds growth with different techniques. Experiments performed at Instituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud (INFN-LNS) of Catania (Italy) and data analysis conducted at Dipartimento di Fisica and DFMTA of the Universita of Messina (Italy), CNR-ITIS of Messina and ST-Microelectronics of Catania will be presented and discussed.

  11. Effect of dry and wet ambient environment on the pulsed laser ablation of titanium

    NASA Astrophysics Data System (ADS)

    Ali, Nisar; Bashir, Shazia; Umm-i-Kalsoom; Akram, Mahreen; Mahmood, Khaliq

    2013-04-01

    Surface and structural properties of the laser irradiated titanium targets have been investigated under dry and wet ambient environments. For this purpose KrF Excimer laser of wavelength 248 nm, pulse duration of 20 ns and repetition rate of 20 Hz has been employed. The targets were exposed for various number of laser pulses ranging from 500 to 2000 in the ambient environment of air, de-ionized water and propanol at a fluence of 3.6 J/cm2. The surface morphology, chemical composition and crystallographical analysis were performed by using Scanning Electron Microscope (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD), respectively. For both central and peripheral ablated areas, significant difference in surface morphology has been observed in case of dry and wet ambient conditions. Large sized and diffused grains are observed in case of dry ablation. Whereas, in case of wet ablation, small sized, and well defined grains with distinct grain boundaries and significantly enhanced density are revealed. This difference is ascribed to the confinement effects of the liquid. The peripheral ablated area shows redeposition in case of dry ablation whereas small sized grain like structures are formed in case of wet ablation. EDS analysis exhibits variation in chemical composition under both ambient conditions. When the targets are treated in air environment, enhancement of the oxygen as well as nitrogen content is observed while in case of de-ionized water and propanol only increase in content of oxygen is observed. X-ray diffraction analysis exhibits formation of oxides and nitrides in case of air, whereas, in case of de-ionized water and propanol only oxides along with hydrides are formed. For various number of laser pulses the variation in the peak intensity, crystallinity and d-spacing is observed under both ambient conditions.

  12. Microwave ablation versus laser ablation in occluding lateral veins in goats.

    PubMed

    Wang, Xu-hong; Wang, Xiao-ping; Su, Wen-juan; Yuan, Yuan

    2016-02-01

    Increasing number of endovenous techniques are available for the treatment of saphenous vein reflux and endovenous laser ablation (EVLA) is a frequently used method. A newly developed alternative, based on thermal therapy, is endovenous microwave ablation (EMA). This study evaluated the effect of the two procedures, in terms of coagulation and histological changes, in occluding lateral veins in goats. Twelve animals were randomized into two group, with 6 treated with EMA (EMA group), and the rest 6 with EVLA (EVLA group). Results of coagulation, including coagulation, fibrinolysis and platelet activation, were assessed at three or four different time points: before, immediately after, 24 h (and 48 h) after ablation. The diameter change, a measure of efficacy, was ultrasonographically measured before and 1 month after the ablation. Histological changes were grossly and microscopically evaluated immediately, 1 and 3 month(s) after the ablation. The length of the ablated vein and preoperative average diameter were comparable between the two groups. In both EMA and EVLA groups, several coagulation parameters, fibrinolysis and platelet activation parameters only underwent slight changes. Ultrasound imaging displayed that the diameter reduction of the veins treated by EMA was significantly larger than by EVLA, in consistent with the results of macroscopic examination. Microscopic examination revealed necrosis and thickening of the vein wall, and occlusion of the lumen within 3 months after ablation in both EMA and EVLA groups. It is concluded that EMA is a minimally invasive therapy, which appears to be safe and effective for treatment of lateral veins in goats.

  13. Thermal Ablation Modeling for Silicate Materials

    NASA Technical Reports Server (NTRS)

    Chen, Yih-Kanq

    2016-01-01

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

  14. Deep Dive Topic: Choosing between ablators

    SciTech Connect

    Hurricane, O. A.; Thomas, C.; Olson, R.

    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.

  15. Numerical Modeling of Ablation Heat Transfer

    NASA Technical Reports Server (NTRS)

    Ewing, Mark E.; Laker, Travis S.; Walker, David T.

    2013-01-01

    A unique numerical method has been developed for solving one-dimensional ablation heat transfer problems. This paper provides a comprehensive description of the method, along with detailed derivations of the governing equations. This methodology supports solutions for traditional ablation modeling including such effects as heat transfer, material decomposition, pyrolysis gas permeation and heat exchange, and thermochemical surface erosion. The numerical scheme utilizes a control-volume approach with a variable grid to account for surface movement. This method directly supports implementation of nontraditional models such as material swelling and mechanical erosion, extending capabilities for modeling complex ablation phenomena. Verifications of the numerical implementation are provided using analytical solutions, code comparisons, and the method of manufactured solutions. These verifications are used to demonstrate solution accuracy and proper error convergence rates. A simple demonstration of a mechanical erosion (spallation) model is also provided to illustrate the unique capabilities of the method.

  16. Optically thick ablation fronts. [in interstellar medium

    NASA Technical Reports Server (NTRS)

    Konigl, A.

    1984-01-01

    The physical characteristics of optically thick ablation fronts such as interstellar clouds are analyzed. Attention is given to cold clumps in both planar and spherical geometries and modifications caused by accelerations in a gravitational field or by evaporation of the clumps when encountered hot gas. The effects of ablation on the appearance of the Rayleigh-Taylor instability are examined in both linear and nonlinear regimes. The results of the calculations are applied to the astrophysical phenomena of cold clumps immersed in a supersonic flow, optically thick jets, and ablation in stellar envelopes. Evaporation in an optically thick front is projected to be orders of magnitude larger than evaporation in electron-conduction fronts in optically thin conditions. The optically thick processes could then be useful for modeling flows from, e.g., newly formed stars and active galactic nuclei.

  17. Laser ablated hard coating for microtools

    DOEpatents

    McLean, W. II; Balooch, M.; Siekhaus, W.J.

    1998-05-05

    Wear-resistant coatings composed of laser ablated hard carbon films, are deposited by pulsed laser ablation using visible light, on instruments such as microscope tips and micro-surgical tools. Hard carbon, known as diamond-like carbon (DLC), films produced by pulsed laser ablation using visible light enhances the abrasion resistance, wear characteristics, and lifetimes of small tools or instruments, such as small, sharp silicon tips used in atomic probe microscopy without significantly affecting the sharpness or size of these devices. For example, a 10--20 nm layer of diamond-like carbon on a standard silicon atomic force microscope (AFM) tip, enables the useful operating life of the tip to be increased by at least twofold. Moreover, the low inherent friction coefficient of the DLC coating leads to higher resolution for AFM tips operating in the contact mode. 12 figs.

  18. Specific Impulse Definition for Ablative Laser Propulsion

    NASA Technical Reports Server (NTRS)

    Herren, Kenneth A.; Gregory, Don A.

    2004-01-01

    The term "specific impulse" is so ingrained in the field of rocket propulsion that it is unlikely that any fundamental argument would be taken seriously for its removal. It is not an ideal measure but it does give an indication of the amount of mass flow (mass loss/time), as in fuel rate, required to produce a measured thrust over some time period This investigation explores the implications of being able to accurately measure the ablation rate and how the language used to describe the specific impulse results may have to change slightly, and recasts the specific impulse as something that is not a time average. It is not currently possible to measure the ablation rate accurately in real time so it is generally just assumed that a constant amount of material will be removed for each laser pulse delivered The specific impulse dependence on the ablation rate is determined here as a correction to the classical textbook definition.

  19. Caries-selective ablation: the second threshold

    NASA Astrophysics Data System (ADS)

    Hennig, Thomas; Rechmann, Peter; Jeitner, Peter; Kaufmann, Raimund

    1993-07-01

    The aim of the study was to describe the appropriate fluence necessary for the effective removal of dental decay by ablation processes without or with at least minimal removal of healthy dentin. The experiments were conducted at two wavelengths [355 nm (frequency tripled, Q-switched Nd:YAG-laser) and 377 nm (frequency doubled, gain-switched Alexandrite-laser)] found to be close to the maximum of preferential absorption of carious dentin over healthy dentin. Optoacoustic techniques were applied to determine the ablation thresholds of healthy and carious dentin. The ablation efficiencies at characteristic fluences were determined using non-tactile microtopography. During all experiments a fiber optic delivery system was engaged.

  20. Performance of Conformable Ablators in Aerothermal Environments

    NASA Technical Reports Server (NTRS)

    Thornton, J.; Fan, W.; Skokova, K.; Stackpoole, M.; Beck, R.; Chavez-Garcia, J.

    2012-01-01

    Conformable Phenolic Impregnated Carbon Ablator, a cousin of Phenolic Impregnated Carbon Ablator (PICA), was developed at NASA Ames Research Center as a lightweight thermal protection system under the Fundamental Aeronautics Program. PICA is made using a brittle carbon substrate, which has a very low strain to failure. Conformable PICA is made using a flexible carbon substrate, a felt in this case. The flexible felt significantly increases the strain to failure of the ablator. PICA is limited by its thermal mechanical properties. Future NASA missions will require heatshields that are more fracture resistant than PICA and, as a result, NASA Ames is working to improve PICAs performance by developing conformable PICA to meet these needs. Research efforts include tailoring the chemistry of conformable PICA with varying amounts of additives to enhance mechanical properties and testing them in aerothermal environments. This poster shows the performance of conformable PICA variants in arc jets tests. Some mechanical and thermal properties will also be presented.

  1. Laser ablated hard coating for microtools

    DOEpatents

    McLean, II, William; Balooch, Mehdi; Siekhaus, Wigbert J.

    1998-05-05

    Wear-resistant coatings composed of laser ablated hard carbon films, are deposited by pulsed laser ablation using visible light, on instruments such as microscope tips and micro-surgical tools. Hard carbon, known as diamond-like carbon (DLC), films produced by pulsed laser ablation using visible light enhances the abrasion resistance, wear characteristics, and lifetimes of small tools or instruments, such as small, sharp silicon tips used in atomic probe microscopy without significantly affecting the sharpness or size of these devices. For example, a 10-20 nm layer of diamond-like carbon on a standard silicon atomic force microscope (AFM) tip, enables the useful operating life of the tip to be increased by at least twofold. Moreover, the low inherent friction coefficient of the DLC coating leads to higher resolution for AFM tips operating in the contact mode.

  2. Effects of endocardial microwave energy ablation

    PubMed Central

    Climent, Vicente; Hurlé, Aquilino; Ho, Siew Yen; Sánchez-Quintana, Damián

    2005-01-01

    Until recently the treatment of atrial fibrillation (AF) consisted primarily of palliation, mostly in the form of pharmacological intervention. However because of recent advances in nonpharmacologic therapies, the current expectation of patients and referring physicians is that AF will be cured, rather than palliated. In recent years there has been a rapid expansion in the availability and variety of energy sources and devices for ablation. One of these energies, microwave, has been applied clinically only in the last few years, and may be a promising technique that is potentially capable of treating a wide range of ventricular and supraventricular arrhythmias. The purpose of this study was to review microwave energy ablation in surgical treatment of AF with special interest in histology and ultrastructure of lesions produced by this endocardial ablation procedure. PMID:16943871

  3. Laser Thermal Ablation of Thyroid Benign Nodules

    PubMed Central

    Shahrzad, Mohammad Karim

    2015-01-01

    Thermal ablation therapies for benign thyroid nodules have been introduced in recent years to avoid the complications of traditional methods such as surgery. Despite the little complications and the reportedly acceptable efficacy of thermal ablation methods, quite few medical centers have sought the potential benefits of employing them. This paper provides an introduction to the literature, principles and advances of Percutaneous Laser Ablation therapy of thyroid benign nodules, as well as a discussion on its efficacy, complications and future. Several clinical research papers evaluating the thermal effect of laser on the alleviation of thyroid nodules have been reviewed to illuminate the important points. The results of this research can help researchers to advance the approach and medical centers to decide on investing in these novel therapies. PMID:26705459

  4. Catheter ablation of fascicular ventricular tachycardia.

    PubMed

    Ramprakash, B; Jaishankar, S; Rao, Hygriv B; Narasimhan, C

    2008-08-01

    Fascicular ventricular tachycardia (VT) is an idiopathic VT with right bundle branch block morphology and left-axis deviation occuring predominantly in young males. Fascicular tachycardia has been classified into three subtypes namely, left posterior fascicular VT, left anterior fascicular VT and upper septal fascicular VT. The mechanism of this tachycardia is believed to be localized reentry close to the fascicle of the left bundle branch. The reentrant circuit is composed of a verapamil sensitive zone, activated antegradely during tachycardia and the fast conduction Purkinje fibers activated retrogradely during tachycardia recorded as the pre Purkinje and the Purkinje potentials respectively. Catheter ablation is the preferred choice of therapy in patients with fascicular VT. Ablation is carried out during tachycardia, using conventional mapping techniques in majority of the patients, while three dimensional mapping and sinus rhythm ablation is reserved for patients with nonmappable tachycardia.

  5. Depth Profiling of Polymer Composites by Ultrafast Laser Ablation

    NASA Astrophysics Data System (ADS)

    Young, Christopher; Clayton, Clive; Longtin, Jon

    2009-03-01

    Past work has shown femtosecond laser ablation to be an athermal process at low fluences in polymer systems. The ablation rate in this low fluence regime is very low, allowing for micro-scale removal of material. We have taken advantage of this fact to perform shallow depth profiling ablation on carbon fiber reinforced polymer (CFRP) composites. Neat composite and resin samples were studied to establish reference ablation profiles. These profiles and the effects of the heterogeneous distribution of carbon fibers were observed through confocal laser profilometry and optical and scanning electron microscopy. Weathered materials that have been subjected to accelerated tests in artificial sunlight or water conditions were ablated to determine the correlation between exposure and change in ablation characteristics. Preliminary Raman and micro-ATR analysis performed before and after ablation shows no chemical changes indicative of thermal effects. The low-volume-ablation property was utilized in an attempt to expose the sizing-matrix interphase for analysis.

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

    PubMed

    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.

  7. EUS-Guided Ethanol Ablation of Insulinomas

    PubMed Central

    Qin, Shan-yu; Lu, Xiu-ping; Jiang, Hai-xing

    2014-01-01

    Abstract Surgical resection is a standard treatment for insulinomas; however, it is associated with a high risk of complications and limited to specific suitable candidates. In recent years, endoscopic ultrasound (EUS)-guided ethanol ablation of insulinomas has emerged as a new therapeutic option, especially for elderly patients and candidates unfit for surgery. We aimed to evaluate the feasibility and safety of this technique for insulinomas. Four patients diagnosed with insulinomas based on EUS–fine-needle aspiration and immunohistochemistry results underwent EUS-guided 95% ethanol ablation. A comprehensive literature review was performed to understand the current status of the feasibility, safety, and effects of EUS-guided ethanol ablation of insulinomas. EUS-guided ethanol ablation of insulinomas was successfully completed in all the 4 patients. There were no perioperative or postoperative complications. The patients were discharged at 3 days after the procedure. No recurrence of hypoglycemia or tumors was noted during follow-up (range, 3–6 months). Literature review showed 8 patients with insulinomas who underwent EUS-guided ethanol ablation. All the procedures were successful, with no need for further surgical treatment. Among these reviewed cases, 6 patients had no post-procedural complications, while other 2 patients showed a mild increase in the serum levels of lipase and/or pancreatic enzymes within 48 h post-procedure; furthermore, 1 of these 2 patients presented at a later date with medically controllable hematoma and ulceration. During follow-up, 6 patients remained asymptomatic and normoglycemic, while the 2 patients who presented post-procedural complications developed occasional mild confusion. EUS-guided ethanol ablation of insulinomas is an effective and safe modality, with an acceptable level of post-procedural complications. However, the long-term effects of this new therapeutic option need to be validated in a large randomized controlled

  8. Revisiting the interplay between ablation, collisional, and radiative processes during ns-laser ablation

    NASA Astrophysics Data System (ADS)

    Autrique, D.; Gornushkin, I.; Alexiades, V.; Chen, Z.; Bogaerts, A.; Rethfeld, B.

    2013-10-01

    A study of ns-laser ablation is presented, which focuses on the transient behavior of the physical processes that act in and above a copper sample. A dimensionless multiphase collisional radiative model describes the interplay between the ablation, collisional, and radiative mechanisms. Calculations are done for a 6 ns-Nd:YAG laser pulse operating at 532 nm and fluences up to 15 J/cm2. Temporal intensity profiles as well as transmissivities are in good agreement with experimental results. It is found that volumetric ablation mechanisms and photo-processes both play an essential role in the onset of ns-laser induced breakdown.

  9. Subcellular analysis by laser ablation electrospray ionization mass spectrometry

    DOEpatents

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

    2014-12-02

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

  10. High throughput solar cell ablation system

    SciTech Connect

    Harley, Gabriel; Pass, Thomas; Cousins, Peter John; Viatella, John

    2014-10-14

    A solar cell is formed using a solar cell ablation system. The ablation system includes a single laser source and several laser scanners. The laser scanners include a master laser scanner, with the rest of the laser scanners being slaved to the master laser scanner. A laser beam from the laser source is split into several laser beams, with the laser beams being scanned onto corresponding wafers using the laser scanners in accordance with one or more patterns. The laser beams may be scanned on the wafers using the same or different power levels of the laser source.

  11. General Model for Multicomponent Ablation Thermochemistry

    NASA Technical Reports Server (NTRS)

    Milos, Frank S.; Marschall, Jochen; Rasky, Daniel J. (Technical Monitor)

    1994-01-01

    A previous paper (AIAA 94-2042) presented equations and numerical procedures for modeling the thermochemical ablation and pyrolysis of thermal protection materials which contain multiple surface species. This work describes modifications and enhancements to the Multicomponent Ablation Thermochemistry (MAT) theory and code for application to the general case which includes surface area constraints, rate limited surface reactions, and non-thermochemical mass loss (failure). Detailed results and comparisons with data are presented for the Shuttle Orbiter reinforced carbon-carbon oxidation protection system which contains a mixture of sodium silicate (Na2SiO3), silica (SiO2), silicon carbide (SiC), and carbon (C).

  12. Thermal tumor ablation in clinical use.

    PubMed

    Brace, C

    2011-01-01

    Although a surgical procedure is performed by visual inspection with histopathological assessment of the excised tumor and margins, percutaneous and noninvasive thermal ablation is performed strictly with the aid of imaging. Applicator guidance into the target zone, treatment monitoring and verification, and clinical follow-up rely on effective imaging. Detailed discussion of imaging is beyond the scope of this article, but the influence of imaging on the choice of thermal ablation or procedural approach will be discussed as needed. More information on imaging for interventional therapies can be found in other articles in this issue of IEEE Pulse.

  13. High throughput solar cell ablation system

    DOEpatents

    Harley, Gabriel; Pass, Thomas; Cousins, Peter John; Viatella, John

    2012-09-11

    A solar cell is formed using a solar cell ablation system. The ablation system includes a single laser source and several laser scanners. The laser scanners include a master laser scanner, with the rest of the laser scanners being slaved to the master laser scanner. A laser beam from the laser source is split into several laser beams, with the laser beams being scanned onto corresponding wafers using the laser scanners in accordance with one or more patterns. The laser beams may be scanned on the wafers using the same or different power levels of the laser source.

  14. Thermal Shock and Ablation Behavior of Tungsten Nozzle Produced by Plasma Spray Forming and Hot Isostatic Pressing

    NASA Astrophysics Data System (ADS)

    Wang, Y. M.; Xiong, X.; Zhao, Z. W.; Xie, L.; Min, X. B.; Yan, J. H.; Xia, G. M.; Zheng, F.

    2015-08-01

    Tungsten nozzle was produced by plasma spray forming (PSF, relative density of 86 ± 2%) followed by hot isostatic pressing (HIPing, 97 ± 2%) at 2000 °C and 180 MPa for 180 min. Scanning electron microscope, x-ray diffractometer, Archimedes method, Vickers hardness, and tensile tests have been employed to study microstructure, phase composition, density, micro-hardness, and mechanical properties of the parts. Resistance of thermal shock and ablation behavior of W nozzle were investigated by hot-firing test on solid rocket motor (SRM). Comparing with PSF nozzle, less damage was observed for HIPed sample after SRM test. Linear ablation rate of nozzle made by PSF was (0.120 ± 0.048) mm/s, while that after HIPing reduced to (0.0075 ± 0.0025) mm/s. Three types of ablation mechanisms including mechanical erosion, thermophysical erosion, and thermochemical ablation took place during hot-firing test. The order of degree of ablation was nozzle throat > convergence > dilation inside W nozzle.

  15. Density Measurements of Be Shells

    SciTech Connect

    Cook, R C

    2005-02-15

    The purpose of this memo is to lay out the uncertainties associated with the measurement of density of Be ablators by the weigh and volume method. I am counting on the readers to point out any faulty assumptions about the techniques or uncertainties associated with them. Based on the analysis presented below we should expect that 30 {micro}m thick shells will have an uncertainty in the measured density of about 2% of the value, coming more or less equally from the mass and volume measurement. The uncertainty is roughly inversely proportional to the coating thickness, thus a 60 {micro}m walled shell would result in a 1% uncertainty in the density.

  16. Experimental measurement of ablation effects in plasma armature railguns

    SciTech Connect

    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.

  17. Ablation techniques for primary and metastatic liver tumors

    PubMed Central

    Ryan, Michael J; Willatt, Jonathon; Majdalany, Bill S; Kielar, Ania Z; Chong, Suzanne; Ruma, Julie A; Pandya, Amit

    2016-01-01

    Ablative treatment methods have emerged as safe and effective therapies for patients with primary and secondary liver tumors who are not surgical candidates at the time of diagnosis. This article reviews the current literature and describes the techniques, complications and results for radiofrequency ablation, microwave ablation, cryoablation, and irreversible electroporation. PMID:26839642

  18. How Well Can We Estimate Areal-Averaged Spectral Surface Albedo from Ground-Based Transmission in an Atlantic Coastal Area?

    SciTech Connect

    Kassianov, Evgueni I.; Barnard, James C.; Flynn, Connor J.; Riihimaki, Laura D.; Marinovici, Maria C.

    2015-10-15

    Areal-averaged albedos are particularly difficult to measure in coastal regions, because the surface is not homogenous, consisting of a sharp demarcation between land and water. With this difficulty in mind, we evaluate a simple retrieval of areal-averaged surface albedo using ground-based measurements of atmospheric transmission alone under fully overcast conditions. To illustrate the performance of our retrieval, we find the areal-averaged albedo using measurements from the Multi-Filter Rotating Shadowband Radiometer (MFRSR) at five wavelengths (415, 500, 615, 673, and 870 nm). These MFRSR data are collected at a coastal site in Graciosa Island, Azores supported by the U.S. Department of Energy’s (DOE’s) Atmospheric Radiation Measurement (ARM) Program. The areal-averaged albedos obtained from the MFRSR are compared with collocated and coincident Moderate Resolution Imaging Spectroradiometer (MODIS) white-sky albedo at four nominal wavelengths (470, 560, 670 and 860 nm). These comparisons are made during a 19-month period (June 2009 - December 2010). We also calculate composite-based spectral values of surface albedo by a weighted-average approach using estimated fractions of major surface types observed in an area surrounding this coastal site. Taken as a whole, these three methods of finding albedo show spectral and temporal similarities, and suggest that our simple, transmission-based technique holds promise, but with estimated errors of about ±0.03. Additional work is needed to reduce this uncertainty in areas with inhomogeneous surfaces.

  19. Stretchable semiconductor technologies with high areal coverages and strain-limiting behavior: demonstration in high-efficiency dual-junction GaInP/GaAs photovoltaics.

    PubMed

    Lee, Jongho; Wu, Jian; Ryu, Jae Ha; Liu, Zhuangjian; Meitl, Matthew; Zhang, Yong-Wei; Huang, Yonggang; Rogers, John A

    2012-06-25

    Notched islands on a thin elastomeric substrate serve as a platform for dual-junction GaInP/GaAs solar cells with microscale dimensions and ultrathin forms for stretchable photovoltaic modules. These designs allow for a high degree of stretchability and areal coverage, and they provide a natural form of strain-limiting behavior, helping to avoid destructive effects of extreme deformations.

  20. How well can we estimate areal-averaged spectral surface albedo from ground-based transmission in the Atlantic coastal area?

    NASA Astrophysics Data System (ADS)

    Kassianov, Evgueni; Barnard, James; Flynn, Connor; Riihimaki, Laura; Marinovici, Cristina

    2015-10-01

    Areal-averaged albedos are particularly difficult to measure in coastal regions, because the surface is not homogenous, consisting of a sharp demarcation between land and water. With this difficulty in mind, we evaluate a simple retrieval of areal-averaged surface albedo using ground-based measurements of atmospheric transmission alone under fully overcast conditions. To illustrate the performance of our retrieval, we find the areal-averaged albedo using measurements from the Multi-Filter Rotating Shadowband Radiometer (MFRSR) at five wavelengths (415, 500, 615, 673, and 870 nm). These MFRSR data are collected at a coastal site in Graciosa Island, Azores supported by the U.S. Department of Energy's (DOE's) Atmospheric Radiation Measurement (ARM) Program. The areal-averaged albedos obtained from the MFRSR are compared with collocated and coincident Moderate Resolution Imaging Spectroradiometer (MODIS) whitesky albedo at four nominal wavelengths (470, 560, 670 and 860 nm). These comparisons are made during a 19-month period (June 2009 - December 2010). We also calculate composite-based spectral values of surface albedo by a weighted-average approach using estimated fractions of major surface types observed in an area surrounding this coastal site. Taken as a whole, these three methods of finding albedo show spectral and temporal similarities, and suggest that our simple, transmission-based technique holds promise, but with estimated errors of about ±0.03. Additional work is needed to reduce this uncertainty in areas with inhomogeneous surfaces.

  1. Nonlinear spectrum of the ablative Rayleigh-Taylor instability in laser-accelerated planar plasmas

    SciTech Connect

    Keskinen, M. J.; Schmitt, A.

    2007-01-15

    A model for the nonlinear spectrum of the ablative Rayleigh-Taylor instability in laser-accelerated planar plasmas has been developed for a wide range of Froude numbers and scale sizes. It is found that the spectrum can be characterized by an inverse power law with spectral index of approximately 2 in the limit of small-wavenumber spectrum cutoffs and small-scale density gradient scale lengths. Comparison of the model spectrum with recent experimental observations is made with good agreement.

  2. Generation of nanostructures on metals by laser ablation in liquids: new results

    SciTech Connect

    Barmina, E V; Shafeev, Georgii A; Stratakis, E; Fotakis, K

    2010-12-29

    Surface nanostructuring of titanium, nickel, molybdenum, and tungsten by ablation with pico- and femtosecond laser pulses in liquids is studied experimentally for the first time. The morphology and properties of obtained nanostructures are investigated using a field emission scanning electron microscope and Raman spectroscopy. The size of nanostructures depends on the laser pulse duration and energy density and on the target material. As a rule, the size distribution of structures is bimodal. Potential applications of such nanostructured substrates are discussed. (photonics and nanotechnology)

  3. Perivascular parenchymal extension of the ablation zone following liver microwave ablation.

    PubMed

    Singh, Saurabh; Siriwardana, Pulathis Nilantha; Johnston, Edward William; Bandula, Steven; Davidson, Brian Ritchie; Illing, Rowland Oliver

    2016-03-31

    A 69-year-old man who presented with abdominal discomfort was, on examination, found to have a palpable abdominal mass. Contrast-enhanced CT showed a mass arising from the inferior vena cava, which biopsy confirmed to be a leiomyosarcoma. One month after chemoradiotherapy, CT demonstrated a new 15 mm solitary central right liver metastasis. Microwave ablation (MWA) of the metastasis was performed using an Acculis Sulis V system (Angiodynamics, USA) at a power of 140 Watts for 4 min, with no immediate complications. After 1 month, MRI with gadolinium was performed to assess the liver ablation zone. The MRI demonstrated thrombosis of a right inferior hepatic vein branch leading to the ablation zone and extension of the ablation zone 1 cm into the tissue around the thrombosed vessel.

  4. Variation of tumoral marker after radiofrequency ablation of pancreatic adenocarcinoma

    PubMed Central

    Barbi, Emilio; Girelli, Roberto; Tinazzi Martini, Paolo; De Robertis, Riccardo; Ciaravino, Valentina; Salvia, Roberto; Butturini, Giovanni; Frigerio, Isabella; Milazzo, Teresa; Crosara, Stefano; Paiella, Salvatore; Pederzoli, Paolo; Bassi, Claudio

    2016-01-01

    Background To evaluate the correlation between variations of CA 19.9 blood levels and the entity of necrosis at CT after radiofrequency ablation (RFA) of unresectable pancreatic adenocarcinoma. Methods In this study, from June 2010 to February 2014, patients with diagnosis of unresectable and not metastatic pancreatic ductal adenocarcinoma, expressing tumor marker CA 19.9, treated with RFA procedure were included. All these patients underwent RFA. CT study was performed 1 week after RFA. The dosage of CA 19.9 levels was performed 1 month after RFA. Features of necrosis at CT, as mean entity, density and necrosis percentages compared to the original lesion, were evaluated and compared by using t-test with CA 19.9 blood levels variations after RFA procedure. Results In this study were included 51 patients with diagnosis of unresectable and not metastatic pancreatic ductal adenocarcinoma, expressing tumor marker CA 19.9, treated with RFA procedure and with CT study and CA 19.9 available for analysis. After the procedure, CA 19.9 blood levels reduced in 24/51 (47%), remained stable in 10/51 (20%) and increased in 17/51 (33%). In patients with CA 19.9 levels reduced, the tumor marker were reduced less than 20% in 4/24 (17%) and more than 20% in 20/24 (83%); instead the tumor marker were reduced less than 30% in 8/24 (33%) and more than 30% in 16/24 (67%). At CT scan necrotic area density difference was not statistically significant. Also there was no statistically significant difference among the mean area, the mean volume and the mean ablation volume in percentage related to the treated tumor among the three different groups of patients divided depending on the CA 19.9 blood levels. But a tendency to a statistically significant difference was found in comparing the mean percentage of ablation volume between two subgroups of patients with a decrease of CA 19.9 levels with less or more than 20% reduction of tumor markers and between two subgroups with less or more than

  5. Enhancement of the maximum energy density in atomic layer deposited oxide based thin film capacitors

    NASA Astrophysics Data System (ADS)

    Spahr, Holger; Nowak, Christine; Hirschberg, Felix; Reinker, Johannes; Kowalsky, Wolfgang; Hente, Dirk; Johannes, Hans-Hermann

    2013-07-01

    Thin film capacitors on areas up to 6 mm2 have been measured regarding capacitance density, relative permittivity, and electrical breakdown. The maximum storable energy density of the thin film capacitors will be discussed as a parameter to evaluate the thin film capacitors applicability. Therefore the measurements of the layer thickness, capacitance density, and the breakdown voltage were combined to achieve the maximum storable areal and volume energy density depending on the dielectric layer thickness. Thickness dependent volume energy densities of up to 50 J/cm3 for pure Al2O3 and 60 J/cm3 for Al2O3/TiO2 nanolaminates were reached.

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

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  7. Ablation plume structure and dynamics in ambient gas observed by laser-induced fluorescence imaging spectroscopy

    NASA Astrophysics Data System (ADS)

    Miyabe, M.; Oba, M.; Iimura, H.; Akaoka, K.; Khumaeni, A.; Kato, M.; Wakaida, I.

    2015-08-01

    The dynamic behavior of an ablation plume in ambient gas has been investigated by laser-induced fluorescence imaging spectroscopy. The second harmonic beam from an Nd:YAG laser (0.5-6 J/cm2) was focused on a sintered oxide pellet or a metal chip of gadolinium. The produced plume was subsequently intersected with a sheet-shaped UV beam from a dye laser so that time-resolved fluorescence images were acquired with an intensified CCD camera at various delay times. The obtained cross-sectional images of the plume indicate that the ablated ground state atoms and ions of gadolinium accumulate in a hemispherical contact layer between the plume and the ambient gas, and a cavity containing a smaller density of ablated species is formed near the center of the plume. At earlier expansion stage, another luminous component also expands in the cavity so that it coalesces into the hemispherical layer. The splitting and coalescence for atomic plume occur later than those for ionic plume. Furthermore, the hemispherical layer of neutral atoms appears later than that of ions; however, the locations of the layers are nearly identical. This coincidence of the appearance locations of the layers strongly suggests that the neutral atoms in the hemispherical layer are produced as a consequence of three-body recombination of ions through collisions with gas atoms. The obtained knowledge regarding plume expansion dynamics and detailed plume structure is useful for optimizing the experimental conditions for ablation-based spectroscopic analysis.

  8. Nanopillar formation from two-shot femtosecond laser ablation of poly-methyl methacrylate

    NASA Astrophysics Data System (ADS)

    Baset, F.; Popov, K.; Villafranca, A.; Alshehri, A. M.; Guay, J.-M.; Ramunno, L.; Bhardwaj, V. R.

    2015-12-01

    We present experimental and numerical studies on the morphological evolution and dynamics of femtosecond laser ablation of bulk poly-methyl methacrylate (PMMA) irradiated with a pair of pulses. We show that a nanopillar-like structure is formed in the middle of the ablation crater for pulse energies below single-shot ablation threshold. The nanopillar is ∼400 nm long, lies adjacent to a nanopore, and protrudes ∼150 nm above the sample surface. As the pulse energy is increased gradually, the nanopillar disappears and the nanopore inside the ablation crater becomes larger. At higher pulse energies, a volcanic eruption like structure appears in the middle of the crater whose size and height increases with energy. 2D molecular dynamics simulations reveal that a nanojet and other features observed at higher pulse energies can be formed when the reflection of a shockwave, induced by the second laser pulse, causes density pinching in the middle of the interaction region that rapidly pushes out molten material towards the surface. The shockwave is reflected from the cold boundaries of a modified region created by the first laser pulse.

  9. UV laser ablation patterns in intraocular lenses

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    The aim of this work is to investigate the effect of UV solid state laser radiation on intraocular lens (IOL) polymer surfaces as an alternative method to conventional surface shaping techniques for IOLs customization. Laser ablation experiments were performed on PMMA plates and commercially available hydrophobic and hydrophilic acrylic IOLs with the 5th harmonic of a Q-switched Nd:YAG laser (λ=213 nm). Circular arrays of holes were drilled on the polymer surface, covering the centre and the peripheries of the IOL. The morphology of the ablated IOL surface was examined with a conventional optical microscope (Leitz GMBH Wetzlar) and with a scanning electron microscope (SEM, Fei - Innova Nanoscope) at various laser parameters. Quantitative measurements of ablation rates were performed with a contact profilometer (Dektak-150), in which a mechanical stylus scanned across the surface of gold-coated IOLs (after SEM imaging) to measure variationsF in surface height. Laser interaction with IOLs depends on optical and mechanical material properties, in addition to laser radiation parameters. The exact ablation mechanism is discussed. Some polymer materials, depending on their properties, are more susceptible to the photothermal mechanism than the photochemical one or vice versa. In summary, every IOL polymer exhibits specific attributes in its interaction with the 5th harmonic of Nd:YAG laser.

  10. Organized Atrial Tachycardias after Atrial Fibrillation Ablation

    PubMed Central

    Castrejón-Castrejón, Sergio; Ortega, Marta; Pérez-Silva, Armando; Doiny, David; Estrada, Alejandro; Filgueiras, David; López-Sendón, José L.; Merino, José L.

    2011-01-01

    The efficacy of catheter-based ablation techniques to treat atrial fibrillation is limited not only by recurrences of this arrhythmia but also, and not less importantly, by new-onset organized atrial tachycardias. The incidence of such tachycardias depends on the type and duration of the baseline atrial fibrillation and specially on the ablation technique which was used during the index procedure. It has been repeatedly reported that the more extensive the left atrial surface ablated, the higher the incidence of organized atrial tachycardias. The exact origin of the pathologic substrate of these trachycardias is not fully understood and may result from the interaction between preexistent regions with abnormal electrical properties and the new ones resultant from radiofrequency delivery. From a clinical point of view these atrial tachycardias tend to remit after a variable time but in some cases are responsible for significant symptoms. A precise knowledge of the most frequent types of these arrhythmias, of their mechanisms and components is necessary for a thorough electrophysiologic characterization if a new ablation procedure is required. PMID:21941669

  11. Outpatient laser tonsillar ablation under local anaesthetic.

    PubMed

    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.

  12. Highspeed laser ablation cutting of metal

    NASA Astrophysics Data System (ADS)

    Ullmann, F.; Loeschner, U.; Hartwig, L.; Szczepanski, D.; Schille, J.; Gronau, S.; Knebel, T.; Drechsel, J.; Ebert, R.; Exner, H.

    2013-02-01

    In laser ablation cutting, irradiation of high-intense laser beams causes ejection of molten and evaporated material out of the cutting zone as a result of high pressure gradients, induced by expanding plasma plumes. This paper investigates highspeed laser ablation cutting of industrial grade metal sheets using high-brilliant continuous wave fiber lasers with output powers up to 5 kW. The laser beam was deflected with scan speeds up to 2700 m/min utilizing both a fast galvanometer scan system and a polygon scan system. By sharp laser beam focusing using different objectives with focal lengths ranging between 160 mm and 500 mm, small laser spot diameters between 16.5 μm and 60 μm were obtained, respectively. As a result high peak intensities between 3*108 W/cm² and 2.5*109 W/cm² were irradiated on the sample surface, and cutting kerfs with a maximum depth of 1.4 mm have been produced. In this study the impact of the processing parameters laser power, laser spot diameter, cutting speed, and number of scans on both the achievable cutting depth and the cutting edge quality was investigated. The ablation depths, the heights of the cutting burr, as well as the removed material volumes were evaluated by means of optical microscope images and cross section photographs. Finally highspeed laser ablation cutting was studied using an intensified ultra highspeed camera in order to get useful insights into the cutting process.

  13. Intumescent-ablator coatings using endothermic fillers

    NASA Technical Reports Server (NTRS)

    Sawko, P. M.; Riccitiello, S. R. (Inventor)

    1978-01-01

    An intumescent-ablator coating composition which contains the ammonium salt of 1,4-nitroaniline-2-sulfonic acid or 4,4 dinitrosul fanilide, a polymeric binder system and about 5 to 30% weight of an endothermic filler is reported. The filler has a decomposition temperature about or within the exothermic region of the intumescent agent.

  14. Microwave ablation devices for interventional oncology.

    PubMed

    Ward, Robert C; Healey, Terrance T; Dupuy, Damian E

    2013-03-01

    Microwave ablation is one of the several options in the ablation armamentarium for the treatment of malignancy, offering several potential benefits when compared with other ablation, radiation, surgical and medical treatment modalities. The basic microwave system consists of the generator, power distribution system and antennas. Often under image (computed tomography or ultrasound) guidance, a needle-like antenna is inserted percutaneously into the tumor, where local microwave electromagnetic radiation is emitted from the probe's active tip, producing frictional tissue heating, capable of causing cell death by coagulation necrosis. Half of the microwave ablation systems use a 915 MHz generator and the other half use a 2450 MHz generator. To date, there are no completed clinical trials comparing microwave devices head-to-head. Prospective comparisons of microwave technology with other treatment alternatives, as well as head-to-head comparison with each microwave device, is needed if this promising field will garner more widespread support and use in the oncology community.

  15. Ablation Resistant Zirconium and Hafnium Ceramics

    NASA Technical Reports Server (NTRS)

    Bull, Jeffrey (Inventor); White, Michael J. (Inventor); Kaufman, Larry (Inventor)

    1998-01-01

    High temperature ablation resistant ceramic composites have been made. These ceramics are composites of zirconium diboride and zirconium carbide with silicon carbide, hafnium diboride and hafnium carbide with silicon carbide and ceramic composites which contain mixed diborides and/or carbides of zirconium and hafnium. along with silicon carbide.

  16. Combining Electrolysis and Electroporation for Tissue Ablation.

    PubMed

    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.

  17. Microwave tumors ablation: principles, clinical applications and review of preliminary experiences.

    PubMed

    Carrafiello, Gianpaolo; Laganà, Domenico; Mangini, Monica; Fontana, Federico; Dionigi, Gianlorenzo; Boni, Luigi; Rovera, Francesca; Cuffari, Salvatore; Fugazzola, Carlo

    2008-01-01

    Local ablative techniques have been developed to enable local control of unresectable tumors. Ablation has been performed with several modalities including ethanol ablation, laser ablation, cryoablation, and radiofrequency ablation. Microwave technology is a new thermal ablation technique for different types of tumors, providing all the benefits of radiofrequency and substantial advantages. Microwave ablation has been applied to liver, lung, kidney and more rarely to bone, pancreas and adrenal glands. Preliminary works show that microwave ablation may be a viable alternative to other ablation techniques in selected patients. However further studies are necessary to confirm short- and long-term effectiveness of the methods and to compare it with other ablative techniques, especially RF.

  18. Thermochemical Ablation Analysis of the Orion Heatshield

    NASA Technical Reports Server (NTRS)

    Sixel, William

    2015-01-01

    The Orion Multi-Purpose Crew Vehicle will one day carry astronauts to the Moon and beyond, and Orion's heatshield is a critical component in ensuring their safe return to Earth. The Orion heatshield is the structural component responsible for absorbing the intense heating environment caused by re-entry to Earth's atmosphere. The heatshield is primarily composed of Avcoat, an ablative material that is consumed during the re-entry process. Ablation is primarily characterized by two processes: pyrolysis and recession. The decomposition of in-depth virgin material is known as pyrolysis. Recession occurs when the exposed surface of the heatshield reacts with the surrounding flow. The Orion heatshield design was changed from an individually filled Avcoat honeycomb to a molded block Avcoat design. The molded block Avcoat heatshield relies on an adhesive bond to keep it attached to the capsule. In some locations on the heatshield, the integrity of the adhesive bond cannot be verified. For these locations, a mechanical retention device was proposed. Avcoat ablation was modelled in CHAR and the in-depth virgin material temperatures were used in a Thermal Desktop model of the mechanical retention device. The retention device was analyzed and shown to cause a large increase in the maximum bondline temperature. In order to study the impact of individual ablation modelling parameters on the heatshield sizing process, a Monte Carlo simulation of the sizing process was proposed. The simulation will give the sensitivity of the ablation model to each of its input parameters. As part of the Monte Carlo simulation, statistical uncertainties on material properties were required for Avcoat. Several properties were difficult to acquire uncertainties for: the pyrolysis gas enthalpy, non-dimensional mass loss rate (B´c), and Arrhenius equation parameters. Variability in the elemental composition of Avcoat was used as the basis for determining the statistical uncertainty in pyrolysis gas

  19. Fascicular ventricular tachycardia: experience with radiofrequency ablation.

    PubMed

    Magalhaes, Sónia; Gonçalves, Helena; Primo, João; Sá, Ana Paula; Silva, Paula; Rosas, Rui; Gama, Vasco

    2006-05-01

    Fascicular ventricular tachycardia (VT), the commonest form of idiopathic left VT, occurs more frequently in young males without structural heart disease and usually presents as paroxysmal palpitations. It is subdivided into two more common subtypes, posterior and anterior. A macro-reentrant circuit involving a considerable and variable extent of the left interventricular septum is presumed to be the underlying arrhythmogenic mechanism. A slow conduction zone with particular sensitivity to verapamil participates in the circuit and it seems that diastolic potentials (DP) represent the electrical activity in or near this zone. The fascicles of the left bundle appear to constitute part of the retrograde pathway and Purkinje potentials (PP) are assumed to represent their activation. In the present retrospective study, the authors review twelve cases of fascicular VT (ten posterior and two anterior) evaluated in the electrophysiology laboratory. Although initial induction was obtained in all patients, reproducibility was poor as a consequence of frequent contact inhibition during endocardial mapping of the left ventricle and this meant that ablation was not possible in two cases. Two cases of associated atrioventricular nodal reentrant tachycardia (AVNRT) and a case of associated atrioventricular reentrant tachycardia by a right posterior accessory pathway were documented, which suggest a correlated anatomic substrate. After ablation of the slow nodal pathway in one of the AVNRTs, fascicular VT was no longer inducible. Ablation of the fascicular VT was attempted in nine patients, at the tachycardia exit site (characterized by an early ventricular electrogram fused with a Purkinje potential) in two patients with anterior fascicular VT and in five patients with the posterior subtype, and near the slow conduction pathway (site with simultaneous recording of DP and PP) in the other two patients. The initial success rate with a single procedure was 78%, two of the ablations

  20. Plume collimation for laser ablation electrospray ionization mass spectrometry

    DOEpatents

    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.