Sample records for ablation plume propagation

  1. Plume collimation for laser ablation electrospray ionization mass spectrometry

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

    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.

  2. Plume collimation for laser ablation electrospray ionization mass spectrometry

    DOEpatents

    Vertes, Akos; Stolee, Jessica A.

    2014-09-09

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

  3. Higher Order Chemistry Models in the CFD Simulation of Laser-Ablated Carbon Plumes

    NASA Technical Reports Server (NTRS)

    Scott, C. D.; Greendyke, R. B.; Creel, J. R.; Payne, B. T.

    2005-01-01

    oven facility is heated to a temperature of 1473 K prior to nanotube production runs. Upon laser irradiation, part of the carbon target ablates immediately and forms a carbon vapor plume that penetrates into the argon base flow towards the laser initially at supersonic velocities. In the previous studies either a single carbon species, C3, was used to model the plume development, or a simplified 11 species carbon model reduced down from the Krestinin and Moravsky model for full fullerene chemistry was used. While both of these options yielded significant results, it was felt that the actual chemistry occ&g in the carbon plume might have a greater affect on the plume than assumed. Indeed, in the earlier attempts at modeling the carbon plume, several thermophysical characteristics could never be matched to experimental observations of plume development - mainly the propagation distance of the plume itself. In the present study, two additional chemistry models will be used to duplicate the previous studies simulations of the carbon plume. The first chemistry model used in this study is again a reduced form of the Krestinin and Moravsky rates. However the highest order carbon species allowed has been increased from C6 to C30 - therefore allowing the simulation of up to a half of the standard C60 fullerene. The second chemistry model investigated is a reduced form of a full carbon nanotube model developed at NASA-JSC. The C30 studies have already been accomplished at the present time, and the reduced SWNT model studies are currently underway. To pursue the current study, one sacrifice had to be made in that the simulation grid spacing had to be increased from 0.5 mm spacing to 1 mm spacing for the sake of computational efficiency since computational effort is proportional to the square of the number of grid points multiplied by the number of species considered. propagation that is far more in line with the experimental results observed by Puretzky et al as shown in Fig. 2

  4. Experimental and computational study of complex shockwave dynamics in laser ablation plumes in argon atmosphere

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

    Harilal, S. S.; Miloshevsky, G. V.; Diwakar, P. K.

    2012-08-15

    We investigated spatio-temporal evolution of ns laser ablation plumes at atmospheric pressure, a favored condition for laser-induced breakdown spectroscopy and laser-ablation inductively coupled plasma mass-spectrometry. The 1064 nm, 6 ns pulses from a Nd:YAG laser were focused on to an Al target and the generated plasma was allowed to expand in 1 atm Ar. The hydrodynamic expansion features were studied using focused shadowgraphy and gated 2 ns self-emission visible imaging. Shadowgram images showed material ejection and generation of shock fronts. A secondary shock is observed behind the primary shock during the time window of 100-500 ns with instabilities near themore » laser cone angle. By comparing the self-emission images obtained using fast photography, it is concluded that the secondary shocks observed in the shadowgraphy were generated by fast moving target material. The plume front estimates using fast photography exhibited reasonable agreement with data obtained from shadowgraphy at early times {<=}400 ns. However, at later times, fast photography images showed plume confinement while the shadowgraphic images showed propagation of the plume front even at greater times. The structure and dynamics of the plume obtained from optical diagnostic tools were compared to numerical simulations. We have shown that the main features of plume expansion in ambient Ar observed in the experiments can be reproduced using a continuum hydrodynamics model which provided valuable insight into the expansion dynamics and shock structure of the plasma plume.« less

  5. Plume propagation direction determination with SO2 cameras

    NASA Astrophysics Data System (ADS)

    Klein, Angelika; Lübcke, Peter; Bobrowski, Nicole; Kuhn, Jonas; Platt, Ulrich

    2017-03-01

    SO2 cameras are becoming an established tool for measuring sulfur dioxide (SO2) fluxes in volcanic plumes with good precision and high temporal resolution. The primary result of SO2 camera measurements are time series of two-dimensional SO2 column density distributions (i.e. SO2 column density images). However, it is frequently overlooked that, in order to determine the correct SO2 fluxes, not only the SO2 column density, but also the distance between the camera and the volcanic plume, has to be precisely known. This is because cameras only measure angular extents of objects while flux measurements require knowledge of the spatial plume extent. The distance to the plume may vary within the image array (i.e. the field of view of the SO2 camera) since the plume propagation direction (i.e. the wind direction) might not be parallel to the image plane of the SO2 camera. If the wind direction and thus the camera-plume distance are not well known, this error propagates into the determined SO2 fluxes and can cause errors exceeding 50 %. This is a source of error which is independent of the frequently quoted (approximate) compensation of apparently higher SO2 column densities and apparently lower plume propagation velocities at non-perpendicular plume observation angles.Here, we propose a new method to estimate the propagation direction of the volcanic plume directly from SO2 camera image time series by analysing apparent flux gradients along the image plane. From the plume propagation direction and the known location of the SO2 source (i.e. volcanic vent) and camera position, the camera-plume distance can be determined. Besides being able to determine the plume propagation direction and thus the wind direction in the plume region directly from SO2 camera images, we additionally found that it is possible to detect changes of the propagation direction at a time resolution of the order of minutes. In addition to theoretical studies we applied our method to SO2 flux

  6. Morphological changes in ultrafast laser ablation plumes with varying spot size

    DOE PAGES

    Harilal, S. S.; Diwakar, P. K.; Polek, M. P.; ...

    2015-06-04

    We investigated the role of spot size on plume morphology during ultrafast laser ablation of metal targets. Our results show that the spatial features of fs LA plumes are strongly dependent on the focal spot size. Two-dimensional self-emission images showed that the shape of the ultrafast laser ablation plumes changes from spherical to cylindrical with an increasing spot size from 100 to 600 μm. The changes in plume morphology and internal structures are related to ion emission dynamics from the plasma, where broader angular ion distribution and faster ions are noticed for the smallest spot size used. The present resultsmore » clearly show that the morphological changes in the plume with spot size are independent of laser pulse width.« less

  7. Morphological changes in ultrafast laser ablation plumes with varying spot size.

    PubMed

    Harilal, S S; Diwakar, P K; Polek, M P; Phillips, M C

    2015-06-15

    We investigated the role of spot size on plume morphology during ultrafast laser ablation of metal targets. Our results show that the spatial features of fs LA plumes are strongly dependent on the focal spot size. Two-dimensional self-emission images showed that the shape of the ultrafast laser ablation plumes changes from spherical to cylindrical with an increasing spot size from 100 to 600 μm. The changes in plume morphology and internal structures are related to ion emission dynamics from the plasma, where broader angular ion distribution and faster ions are noticed for the smallest spot size used. The present results clearly show that the morphological changes in the plume with spot size are independent of laser pulse width.

  8. 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.

  9. Higher Order Chemistry Models in the CFD Simulation of Laser-Ablated Carbon Plumes

    NASA Technical Reports Server (NTRS)

    Greendyke, R. B.; Creel, J. R.; Payne, B. T.; Scott, C. D.

    2005-01-01

    Production of single-walled carbon nanotubes (SWNT) has taken place for a number of years and by a variety of methods such as laser ablation, chemical vapor deposition, and arc-jet ablation. Yet, little is actually understood about the exact chemical kinetics and processes that occur in SWNT formation. In recent time, NASA Johnson Space Center has devoted a considerable effort to the experimental evaluation of the laser ablation production process for SWNT originally developed at Rice University. To fully understand the nature of the laser ablation process it is necessary to understand the development of the carbon plume dynamics within the laser ablation oven. The present work is a continuation of previous studies into the efforts to model plume dynamics using computational fluid dynamics (CFD). The ultimate goal of the work is to improve understanding of the laser ablation process, and through that improved understanding, refine the laser ablation production of SWNT.

  10. Effect of defocusing on laser ablation plume observed by laser-induced fluorescence imaging spectroscopy

    NASA Astrophysics Data System (ADS)

    Oba, Masaki; Miyabe, Masabumi; Akaoka, Katsuaki; Wakaida, Ikuo

    2016-02-01

    We used laser-induced fluorescence imaging with a varying beam focal point to observe ablation plumes from metal and oxide samples of gadolinium. The plumes expand vertically when the focal point is far from the sample surface. In contrast, the plume becomes hemispherical when the focal point is on the sample surface. In addition, the internal plume structure and the composition of the ablated atomic and ionic particles also vary significantly. The fluorescence intensity of a plume from a metal sample is greater than that from an oxide sample, which suggests that the number of monatomic species produced in each plume differs. For both the metal and oxide samples, the most intense fluorescence from atomic (ionic) species is observed with the beam focal point at 3-4 mm (2 mm) from the sample surface.

  11. Investigation of plume dynamics during picosecond laser ablation of H13 steel using high-speed digital holography

    NASA Astrophysics Data System (ADS)

    Pangovski, Krste; Otanocha, Omonigho B.; Zhong, Shan; Sparkes, Martin; Liu, Zhu; O'Neill, William; Li, Lin

    2017-02-01

    Ablation of H13 tool steel using pulse packets with repetition rates of 400 and 1000 kHz and pulse energies of 75 and 44 μ {J}, respectively, is investigated. A drop in ablation efficiency (defined here as the depth per pulse or μ {m}{/}μ {J}) is shown to occur when using pulse energies of E_{{pulse}} > 44 μ {J}, accompanied by a marked difference in crater morphology. A pulsed digital holographic system is applied to image the resulting plumes, showing a persistent plume in both cases. Holographic data are used to calculate the plume absorption and subsequently the fraction of pulse energy arriving at the surface after traversing the plume for different pulse arrival times. A significant proportion of the pulse energy is shown to be absorbed in the plume for E_{{pulse}} > 44 μ {J} for pulse arrival times corresponding to {>}1 MHz pulse repetition rate, shifting the interaction to a vapour-dominated ablation regime, an energetically costlier ablation mechanism.

  12. Toward single-cell analysis by plume collimation in laser ablation electrospray ionization mass spectrometry.

    PubMed

    Stolee, Jessica A; Vertes, Akos

    2013-04-02

    Ambient ionization methods for mass spectrometry have enabled the in situ and in vivo analysis of biological tissues and cells. When an etched optical fiber is used to deliver laser energy to a sample in laser ablation electrospray ionization (LAESI) mass spectrometry, the analysis of large single cells becomes possible. However, because in this arrangement the ablation plume expands in three dimensions, only a small portion of it is ionized by the electrospray. Here we show that sample ablation within a capillary helps to confine the radial expansion of the plume. Plume collimation, due to the altered expansion dynamics, leads to greater interaction with the electrospray plume resulting in increased ionization efficiency, reduced limit of detection (by a factor of ~13, reaching 600 amol for verapamil), and extended dynamic range (6 orders of magnitude) compared to conventional LAESI. This enhanced sensitivity enables the analysis of a range of metabolites from small cell populations and single cells in the ambient environment. This technique has the potential to be integrated with flow cytometry for high-throughput metabolite analysis of sorted cells.

  13. Influence of the ablation plume on the removal process during ArF-excimer laser photoablation

    NASA Astrophysics Data System (ADS)

    Doerbecker, Christina; Lubatschowski, Holger; Lohmann, Stefan; Ruff, Christine; Kermani, Omid; Ertmer, Wolfgang

    1996-01-01

    Correction of myopia with the ArF-excimer laser (PRK) sometimes leads to a so called 'central island' formation on the anterior corneal surface. The attenuation of the laser beam by the ablation plume might be one reason for this phenomenon. The attenuation properties of the ablation plume were investigated by a probe beam parallel to the surface of the tissue probe. By varying the laser parameters (fluence, repetition rate, spot size) and the target tissue (cornea, PMMA) the attenuation of the probe beam was measured time and spatial resolved. As a result of this study, a significant influence of the removal process due to scattering and absorption within the ablation plume can be assumed as a function of repetition rate, spot size and air flow on the tissue surface.

  14. Two-dimensional fluorescence spectroscopy of uranium isotopes in femtosecond laser ablation plumes

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

    Phillips, Mark C.; Brumfield, Brian E.; LaHaye, Nicole

    Here, we demonstrate measurement of uranium isotopes in femtosecond laser ablation plumes using two-dimensional fluorescence spectroscopy (2DFS). The high-resolution, tunable CW-laser spectroscopy technique clearly distinguishes atomic absorption from 235U and 238U in natural and highly enriched uranium metal samples. We present analysis of spectral resolution and analytical performance of 2DFS as a function of ambient pressure. Simultaneous measurement using time-resolved absorption spectroscopy provides information on temporal dynamics of the laser ablation plume and saturation behavior of fluorescence signals. The rapid, non-contact measurement is promising for in-field, standoff measurements of uranium enrichment for nuclear safety and security.

  15. Two-dimensional fluorescence spectroscopy of uranium isotopes in femtosecond laser ablation plumes

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

    Phillips, Mark C.; Brumfield, Brian E.; LaHaye, Nicole L.

    We demonstrate measurement of uranium isotopes in femtosecond laser ablation plumes using two-dimensional fluorescence spectroscopy (2DFS). The high-resolution, tunable CW-laser spectroscopy technique clearly distinguishes atomic absorption from 235U and 238U in natural and highly enriched uranium metal samples. We present analysis of spectral resolution and analytical performance of 2DFS as a function of ambient pressure. Simultaneous measurement using time-resolved absorption spectroscopy provides information on temporal dynamics of the laser ablation plume and saturation behavior of fluorescence signals. The rapid, non-contact measurement is promising for in-field, standoff measurements of uranium enrichment for nuclear safety and security applications.

  16. Two-dimensional fluorescence spectroscopy of uranium isotopes in femtosecond laser ablation plumes

    DOE PAGES

    Phillips, Mark C.; Brumfield, Brian E.; LaHaye, Nicole; ...

    2017-06-19

    Here, we demonstrate measurement of uranium isotopes in femtosecond laser ablation plumes using two-dimensional fluorescence spectroscopy (2DFS). The high-resolution, tunable CW-laser spectroscopy technique clearly distinguishes atomic absorption from 235U and 238U in natural and highly enriched uranium metal samples. We present analysis of spectral resolution and analytical performance of 2DFS as a function of ambient pressure. Simultaneous measurement using time-resolved absorption spectroscopy provides information on temporal dynamics of the laser ablation plume and saturation behavior of fluorescence signals. The rapid, non-contact measurement is promising for in-field, standoff measurements of uranium enrichment for nuclear safety and security.

  17. Diagnostics of Carbon Nanotube Formation in a Laser Produced Plume: An Investigation of the Metal Catalyst by Laser Ablation Atomic Fluorescence Spectroscopy

    NASA Technical Reports Server (NTRS)

    deBoer, Gary; Scott, Carl

    2003-01-01

    Carbon nanotubes, elongated molecular tubes with diameters of nanometers and lengths in microns, hold great promise for material science. Hopes for super strong light-weight material to be used in spacecraft design is the driving force behind nanotube work at JSC. The molecular nature of these materials requires the appropriate tools for investigation of their structure, properties, and formation. The mechanism of nanotube formation is of particular interest because it may hold keys to controlling the formation of different types of nanotubes and allow them to be produced in much greater quantities at less cost than is currently available. This summer's work involved the interpretation of data taken last summer and analyzed over the academic year. The work involved diagnostic studies of carbon nanotube formation processes occurring in a laser-produced plume. Laser ablation of metal doped graphite to produce a plasma plume in which carbon nanotubes self assemble is one method of making carbon nanotube. The laser ablation method is amenable to applying the techniques of laser spectroscopy, a powerful tool for probing the energies and dynamics of atomic and molecular species. The experimental work performed last summer involved probing one of the metal catalysts, nickel, by laser induced fluorescence. The nickel atom was studied as a function of oven temperature, probe laser wavelength, time after ablation, and position in the laser produced plume. This data along with previously obtained data on carbon was analyzed over the academic year. Interpretations of the data were developed this summer along with discussions of future work. The temperature of the oven in which the target is ablated greatly influences the amount of material ablated and the propagation of the plume. The ablation conditions and the time scale of atomic and molecular lifetimes suggest that initial ablation of the metal doped carbon target results in atomic and small molecular species. The metal

  18. Periodic Phenomena In Laser-Ablation Plasma Plumes: A Self-Organization Scenario

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

    Gurlui, S.; Sanduloviciu, M.; Mihesan, C.

    2006-01-15

    Experimental evidence of the appearance of a proper periodic dynamics in a plasma plume created by pulsed laser ablation is considered as a hint for the presence of a self-organization scenario that explains similar phenomena observed in plasma diodes.

  19. Experimental studies of laser-ablated zirconium carbide plasma plumes: Fuel corrosion diagnostic development

    NASA Astrophysics Data System (ADS)

    Wantuck, P. J.; Butt, D. P.; Sappey, A. D.

    Understanding the corrosion behavior of nuclear fuel materials, such as refractory carbides, in a high temperature hydrogen environment is critical for several proposed nuclear thermal propulsion (NTP) concepts. Monitoring the fuel corrosion products is important not only for understanding corrosion characteristics, but to assess the performance of an actual, operating nuclear propulsion system as well. In this paper, we describe an experimental study initiated to develop, test, and subsequently utilize non-intrusive, laser-based diagnostics to characterize the gaseous product species which are expected to evolve during the exposure of representative fuel samples to hydrogen. Laser ablation is used to produce high temperature, vapor plumes from solid solution, uranium-free, zirconium carbide (ZrC) forms for probing by other laser diagnostic methods, predominantly laser-induced fluorescence (LIF). We discuss the laser ablation technique, results of plume emission measurements, as well as the use of planar LIF to image both the ZrC plumes and actual NTP fuel corrosion constituents.

  20. The role of laser wavelength on plasma generation and expansion of ablation plumes in air

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

    Hussein, A. E.; Department of Physics, McGill University, Montreal, Quebec H3A 0G4; Diwakar, P. K.

    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 photographymore » 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.« less

  1. Dynamics of plasma expansion and shockwave formation in femtosecond laser-ablated aluminum plumes in argon gas at atmospheric pressures

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

    Miloshevsky, Alexander; Harilal, Sivanandan S.; Miloshevsky, Gennady, E-mail: gennady@purdue.edu

    2014-04-15

    Plasma expansion with shockwave formation during laser ablation of materials in a background gasses is a complex process. The spatial and temporal evolution of pressure, temperature, density, and velocity fields is needed for its complete understanding. We have studied the expansion of femtosecond (fs) laser-ablated aluminum (Al) plumes in Argon (Ar) gas at 0.5 and 1 atmosphere (atm). The expansion of the plume is investigated experimentally using shadowgraphy and fast-gated imaging. The computational fluid dynamics (CFD) modeling is also carried out. The position of the shock front measured by shadowgraphy and fast-gated imaging is then compared to that obtained frommore » the CFD modeling. The results from the three methods are found to be in good agreement, especially during the initial stage of plasma expansion. The computed time- and space-resolved fields of gas-dynamic parameters have provided valuable insights into the dynamics of plasma expansion and shockwave formation in fs-pulse ablated Al plumes in Ar gas at 0.5 and 1 atm. These results are compared to our previous data on nanosecond (ns) laser ablation of Al [S. S. Harilal et al., Phys. Plasmas 19, 083504 (2012)]. It is observed that both fs and ns plumes acquire a nearly spherical shape at the end of expansion in Ar gas at 1 atm. However, due to significantly lower pulse energy of the fs laser (5 mJ) compared to pulse energy of the ns laser (100 mJ) used in our studies, the values of pressure, temperature, mass density, and velocity are found to be smaller in the fs laser plume, and their time evolution occurs much faster on the same time scale. The oscillatory shock waves clearly visible in the ns plume are not observed in the internal region of the fs plume. These experimental and computational results provide a quantitative understanding of plasma expansion and shockwave formation in fs-pulse and ns-pulse laser ablated Al plumes in an ambient gas at atmospheric pressures.« less

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

    NASA Technical Reports Server (NTRS)

    Harris, Michael F.; Vu, Bruce T.

    2012-01-01

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

  3. Condensation of ablation plumes in the irradiation of metals by high-intensity nanosecond laser pulses at atmospheric pressure

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

    Kozadaev, K V

    2016-01-31

    The Anisimov–Luk'yanchuk model is adapted for describing the condensation of vapour-plasma plumes produced in the irradiation of metal targets by high-intensity (10{sup 8} – 10{sup 10} W cm{sup -2}) nanosecond (10 – 100 ns) pulses at atmospheric pressure. The resultant data suggest that the initial stages of the development of metal ablation plumes correspond with a high degree of accuracy to the Zel'dovich–Raizer theory of dynamic condensation; however, at the stage of the ablation plume decay, the liquid-droplet phase is formed primarily by coalescence of 'nuclei'. (interaction of laser radiation with matter. laser plasma)

  4. Improving Thermal Ablation Delineation With Electrode Vibration Elastography Using a Bidirectional Wave Propagation Assumption

    PubMed Central

    DeWall, Ryan J.; Varghese, Tomy

    2013-01-01

    Thermal ablation procedures are commonly used to treat hepatic cancers and accurate ablation representation on shear wave velocity images is crucial to ensure complete treatment of the malignant target. Electrode vibration elastography is a shear wave imaging technique recently developed to monitor thermal ablation extent during treatment procedures. Previous work has shown good lateral boundary delineation of ablated volumes, but axial delineation was more ambiguous, which may have resulted from the assumption of lateral shear wave propagation. In this work, we assume both lateral and axial wave propagation and compare wave velocity images to those assuming only lateral shear wave propagation in finite element simulations, tissue-mimicking phantoms, and bovine liver tissue. Our results show that assuming bidirectional wave propagation minimizes artifacts above and below ablated volumes, yielding a more accurate representation of the ablated region on shear wave velocity images. Area overestimation was reduced from 13.4% to 3.6% in a stiff-inclusion tissue-mimicking phantom and from 9.1% to 0.8% in a radio-frequency ablation in bovine liver tissue. More accurate ablation representation during ablation procedures increases the likelihood of complete treatment of the malignant target, decreasing tumor recurrence. PMID:22293748

  5. Improving thermal ablation delineation with electrode vibration elastography using a bidirectional wave propagation assumption.

    PubMed

    DeWall, Ryan J; Varghese, Tomy

    2012-01-01

    Thermal ablation procedures are commonly used to treat hepatic cancers and accurate ablation representation on shear wave velocity images is crucial to ensure complete treatment of the malignant target. Electrode vibration elastography is a shear wave imaging technique recently developed to monitor thermal ablation extent during treatment procedures. Previous work has shown good lateral boundary delineation of ablated volumes, but axial delineation was more ambiguous, which may have resulted from the assumption of lateral shear wave propagation. In this work, we assume both lateral and axial wave propagation and compare wave velocity images to those assuming only lateral shear wave propagation in finite element simulations, tissue-mimicking phantoms, and bovine liver tissue. Our results show that assuming bidirectional wave propagation minimizes artifacts above and below ablated volumes, yielding a more accurate representation of the ablated region on shear wave velocity images. Area overestimation was reduced from 13.4% to 3.6% in a stiff-inclusion tissue-mimicking phantom and from 9.1% to 0.8% in a radio-frequency ablation in bovine liver tissue. More accurate ablation representation during ablation procedures increases the likelihood of complete treatment of the malignant target, decreasing tumor recurrence. © 2012 IEEE

  6. Plume dynamics from UV pulsed ablation of Al and Ti

    NASA Astrophysics Data System (ADS)

    Bauer, William; Perram, Glen; Haugan, Timothy

    2016-12-01

    Pulsed laser ablation of Al and Ti with a < 3.3 J/cm2 KrF laser and Ar background pressure of up to 1 Torr was performed to study the ablated plume. Mass loss experiments revealed the number of ablated atoms per pulse increases by 30% for Ti and 20% for Al as pressure decreases from 1 Torr to vacuum. Optical emission imaging performed using a gated ICCD revealed a strong dependence of shock front parameters, defined by the Sedov-Taylor blast and classical drag models, on background pressure. Spatially resolved optical emission spectroscopy from Al I, Al II, Ti I, and Ti II revealed ion temperatures of 104 K that decreased away from the target surface along the surface normal and neutral temperatures of 103 K independent of target distance. Comparison between kinetic energy in the shock and internal excitation energy reveals that nearly 100% of the energy is partitioned into shock front kinetic energy and 1% into internal excitation.

  7. Characterization of ultrafast laser-ablation plasma plumes at various Ar ambient pressures

    DOE PAGES

    Diwakar, P. K.; Harilal, S. S.; Phillips, M. C.; ...

    2015-07-30

    Expansion dynamics and internal plume structures of fs laser ablated brass plasma in Ar at various pressure levels ranging from vacuum to atmospheric were studied using multitude of diagnostic tools including time resolved and time integrated 2-dimensional imaging, optical time of flight measurements and visible emission spectroscopy. Temporal evolution of excited Cu and Zn species in the plume were imaged using band pass interference filters and compared its hydrodynamic expansion features with spectrally integrated images of the plume. 2D imaging coupled with monochromatic line selection showed several interesting features at various pressure levels which include velocity differences among the plumemore » species, emission intensity distribution, plasma temperature, electron density etc. Plume confinement, enhanced signal intensity, and dual peak structures in time-of-flight profiles were observed at intermediate pressure range of ~10 Torr. Optimum signal to background ratio was also observed in this pressure range. As a result, possible mechanisms for observed changes in plume shape, optical emission intensity and dual peak structures in time-of-flight profiles were discussed.« less

  8. Comparison of plume dynamics for laser ablated metals: Al and Ti

    NASA Astrophysics Data System (ADS)

    Bauer, William; Perram, Glen P.; Haugan, Timothy

    2018-03-01

    Emissive plumes from pulsed laser ablation of bulk Ti and Al from KrF laser irradiation at laser fluence up to 3.5 J/cm2 and argon background pressures of 0-1 Torr have been observed using gated intensified charged-coupled device imagery. Mass loss for Ti increases from 0.1 to 0.8 μg/pulse as pulse energy increase from 174 to 282 mJ/pulse (35-170 photons/atom) and decreases by ˜30% as pressure increases from vacuum to 1 Torr. Early plume energies are described by the free expansion velocities of 1.57 ± 0.02 and of 1.81 ± 0.07 cm/μs for Ti and Al, respectively, and up to 90% of the incoming laser energy can be attributed to the Al shock front in the mid-field. The ablation thresholds of 90 ± 27 mJ (1.12 ± 0.34 J/cm2) for Ti and 126 ± 13 mJ (1.58 ± 0.16 J/cm2) for Al also represent 30%-70% of the incident laser energy. The decrease in mass loss at higher pressures is attributed to plasma shielding of the target surface.

  9. Characteristics of plasma plume in ultrafast laser ablation with a weakly ionized air channel

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

    Hou, Huaming; Yang, Bo; Mao, Xianglei

    We report the influence of femtosecond (fs) laser weakly ionized air channel on characteristics of plasma induced from fs-laser ablation of solid Zr metal target. A novel method to create high temperature, low electron density plasma with intense elemental emission and weak bremsstrahlung emission was demonstrated. Weakly ionized air channel was generated as a result of a non-linear phenomenon. Two-dimensional time-resolved optical-emission images of plasma plumes were taken for plume dynamics analysis. Dynamic physical properties of filament channels were simulated. In particular, we investigated the influence of weakly ionized air channel on the evolution of solid plasma plume. Plasma plumemore » splitting was observed whilst longer weakly ionized air channel formed above the ablation spot. The domination mechanism for splitting is attributed to the long-lived underdense channel created by fs-laser induced weakly ionization of air. The evolutions of atomic/molecular emission intensity, peak broadening, and plasma temperature were analyzed, and the results show that the part of plasma entering weakly ionized air channel features higher initial temperature, lower electron density and faster decay.« less

  10. Characteristics of plasma plume in ultrafast laser ablation with a weakly ionized air channel

    DOE PAGES

    Hou, Huaming; Yang, Bo; Mao, Xianglei; ...

    2018-05-10

    We report the influence of femtosecond (fs) laser weakly ionized air channel on characteristics of plasma induced from fs-laser ablation of solid Zr metal target. A novel method to create high temperature, low electron density plasma with intense elemental emission and weak bremsstrahlung emission was demonstrated. Weakly ionized air channel was generated as a result of a non-linear phenomenon. Two-dimensional time-resolved optical-emission images of plasma plumes were taken for plume dynamics analysis. Dynamic physical properties of filament channels were simulated. In particular, we investigated the influence of weakly ionized air channel on the evolution of solid plasma plume. Plasma plumemore » splitting was observed whilst longer weakly ionized air channel formed above the ablation spot. The domination mechanism for splitting is attributed to the long-lived underdense channel created by fs-laser induced weakly ionization of air. The evolutions of atomic/molecular emission intensity, peak broadening, and plasma temperature were analyzed, and the results show that the part of plasma entering weakly ionized air channel features higher initial temperature, lower electron density and faster decay.« less

  11. Range safety signal propagation through the SRM exhaust plume of the space shuttle

    NASA Technical Reports Server (NTRS)

    Boynton, F. P.; Davies, A. R.; Rajasekhar, P. S.; Thompson, J. A.

    1977-01-01

    Theoretical predictions of plume interference for the space shuttle range safety system by solid rocket booster exhaust plumes are reported. The signal propagation was calculated using a split operator technique based upon the Fresnel-Kirchoff integral, using fast Fourier transforms to evaluate the convolution and treating the plume as a series of absorbing and phase-changing screens. Talanov's lens transformation was applied to reduce aliasing problems caused by ray divergence.

  12. Monitoring of KrF excimer laser ablation for burn scars: a comparative study of transient reflection measurement and time-resolved photography of ablation plume

    NASA Astrophysics Data System (ADS)

    Nakajima, Akio; Arai, Tsunenori; Kikuchi, Makoto; Iwaya, Akimi; Arai, Katsuyuki; Inazaki, Satoshi; Takaoka, Takatsugu; Kato, Masayoshi

    1995-05-01

    A simple laser ablation monitoring during burn scar removal by KrF laser irradiation was studied to control laser fluence in real-time. Because, to obtain suitable surface for auto skin-graft, the laser fluence should be precisely controlled at each laser shot. We employed simple probe transmission method which could detect ejected material/phenomena from irradiated surface. The time-course of measured probe intensity contained a couple of attenuated peaks, which might corresponded to a shock wave front and debris plume. The delay time from laser irradiation to the debris plume peak appearance varied with the ablation fluence. The delay time of 1 J/cm2 (near ablation threshold) case prolonged 25% from 8 J/cm2 (far above threshold) case. Therefore, we think the delay time measurement by means of the simple probe transmission method may be available to attain the laser fluence control for nonuniform burn scar removal. The time-resolved photography and probe reflection method were also studied to understand the measured time-course of the transmitted probe intensity.

  13. Plume splitting and oscillatory behavior in transient plasmas generated by high-fluence laser ablation in vacuum

    NASA Astrophysics Data System (ADS)

    Focsa, C.; Gurlui, S.; Nica, P.; Agop, M.; Ziskind, M.

    2017-12-01

    We present a short overview of studies performed in our research groups over the last decade on the characterization of transient plasma plumes generated by laser ablation in various temporal regimes, from nanosecond to femtosecond. New results are also presented along with this overview, both being placed in the context of similar studies performed by other investigators. Optical (fast gate intensified CCD camera imaging and space- and time-resolved emission spectroscopy) and electrical (mainly Langmuir probe) methods have been applied to experimentally explore the dynamics of the plasma plume and its constituents. Peculiar effects as plume splitting and sharpening or oscillations onset have been evidenced in vacuum at high laser fluence. New theoretical approaches have been developed to account for the experimental observations.

  14. Time-resolved imaging of gas phase nanoparticle synthesis by laser ablation

    NASA Astrophysics Data System (ADS)

    Geohegan, David B.; Puretzky, Alex A.; Duscher, Gerd; Pennycook, Stephen J.

    1998-06-01

    The dynamics of nanoparticle formation, transport, and deposition by pulsed laser ablation of c-Si into 1-10 Torr He and Ar gases are revealed by imaging laser-induced photoluminescence and Rayleigh-scattered light from gas-suspended 1-10 nm SiOx particles. Two sets of dynamic phenomena are presented for times up to 15 s after KrF-laser ablation. Ablation of Si into heavier Ar results in a uniform, stationary plume of nanoparticles, while Si ablation into lighter He results in a turbulent ring of particles which propagates forward at 10 m/s. Nanoparticles unambiguously formed in the gas phase were collected on transmission electron microscope grids for Z-contrast imaging and electron energy loss spectroscopy analysis. The effects of gas flow on nanoparticle formation, photoluminescence, and collection are described.

  15. Time-of-flight spectroscopy characterization of the plasma plume from a laser-ablated potassium titanyl phosphate crystal

    NASA Astrophysics Data System (ADS)

    Ying, Minju; Wang, XiaoXiao; Cheng, Wei; Liao, Bin; Zhang, Xu

    2015-06-01

    Optical emission spectra of the plasma produced by 1.06-μm Nd:YAG laser irradiation of a potassium titanyl phosphate (KTP) crystal were recorded and analyzed in a time- and spatially resolved manner. The composition and evolution of the plasma plume were studied in low vacuum conditions. Emission lines associated with Ti(I), Ti(II) and K(I) were identified in the plasma. The delay times of emission peaks for the ablated species were investigated as a function of the observation distance from the target surface, and the velocities of these species were derived accordingly. Two emission peaks corresponding to a fast and a slow component of ablated Ti(I) were observed by optical time-of-flight spectroscopy. The origins of the two peaks and a possible mechanism for the laser ablation are discussed.

  16. 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.

  17. Spectroscopic diagnostics of plume rebound and shockwave dynamics of confined aluminum laser plasma plumes

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

    Yeates, P.; Kennedy, E. T.; School of Physical Sciences, Dublin City University

    2011-06-15

    Generation and expansion dynamics of aluminum laser plasma plumes generated between parallel plates of varying separation ({Delta}Z = 2.0, 3.2, 4.0, and 5.6 mm), which confined plume expansion normal to the ablation surface, were diagnosed. Space and time resolved visible emission spectroscopy in the spectral range {lambda} = 355-470 nm and time gated visible imaging were employed to record emission spectra and plume dynamics. Space and time resolved profiles of N{sub e} (the electron density), T{sub e} (the electron temperature), and T{sub ionz} (the ionization temperature) were compared for different positions in the plasma plume. Significant modifications of the profilesmore » of the above parameters were observed for plasma-surface collisions at the inner surface of the front plate, which formed a barrier to the free expansion of the plasma plume generated by the laser light on the surface of the back plate. Shockwave generation at the collision interface resulted in delayed compression of the low-density plasma plume near the inner ablation surface, at late stages in the plasma history. Upon exiting the cavity formed by the two plates, through an aperture in the front plate, the plasma plume underwent a second phase of free expansion.« less

  18. Propagation of the Sea of Azov plume in the Black Sea and its relation with atmospheric forcing

    NASA Astrophysics Data System (ADS)

    Zavialov, Ivan; Osadchiev, Alexander

    2017-04-01

    This work is devoted to research of the influence of wind forcing on propagation of the Sea of Azov water plume in the Black Sea. The Sea of Azov water is characterized by relatively low salinity and high concentrations of suspended matter, terrigenic nutrients, and anthropogenic pollutants. Thus, the Sea of Azov inflow has significant impacts on physical, chemical, and biological processes in the Black Sea. The increased concentration of the suspended matter in the Sea of Azov plume allows to determine accurately its borders based on remote sensing data. For this purpose, data of the satellite color scanner MERIS/EnviSat with 300-meter spatial resolution were used. Atmospheric forcing on the Sea of Azov plume was investigated with the data of 6-hour reanalysis of winds (MERRA and NCAR/NCEP) with spatial resolution at 1/2 degrees in latitude and 2/3 degrees in longitude. Based on satellite images and wind reanalysis data for 2002-2012 period, it was established that the Azov Sea water inflow is favored by strong N and NE winds, which prevail in the region. It is evident in the processed satellite data that the Sea of Azov plume mainly extends along the east coast of the Crimean peninsula. In some cases under sufficiently strong winds, the Azov waters spread to the southern coast of the Crimea, and sometimes even to its south-west extremity. Factors influencing the propagation of the Azov Sea plume include intensity of water exchange between the Azov and the Black seas, the Rim Current, mesoscale eddies and other dynamic processes. However, the study demonstrated that the influence of wind forcing is dominant. Empirical regressions are derived expressing the dependence of the Azov plume area and its orientation on the magnitude and directions of the wind stress. Satellite-derived statistics of the Azov plume in the Black Sea characteristics are obtained.

  19. Time resolved optical diagnostics of ZnO plasma plumes in air

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

    Gupta, Shyam L.; Singh, Ravi Pratap; Thareja, Raj K.

    2013-10-15

    We report dynamical evolution of laser ablated ZnO plasma plumes using interferometry and shadowgraphy; 2-D fast imaging and optical emission spectroscopy in air ambient at atmospheric pressure. Recorded interferograms using Nomarski interferometer and shadowgram images at various time delays show the presence of electrons and neutrals in the ablated plumes. The inference drawn from sign change of fringe shifts is consistent with two dimensional images of the plume and optical emission spectra at varying time delays with respect to ablating pulse. Zinc oxide plasma plumes are created by focusing 1.06 μm radiation on to ZnO target in air and 532more » nm is used as probe beam.« less

  20. The propagation of GPS signals through electrically charged plumes

    NASA Astrophysics Data System (ADS)

    Méndez Harper, J.; Steffes, P. G.; Dufek, J.

    2017-12-01

    Probing the interior dynamics of eruptive columns using electrostatic processes generated within the flows themselves has garnered much interest in the recent years. Indeed, large eruptions are often accompanied by brilliant displays of lightning, testifying to the high potentials that can be accumulated by a diverse set of electrification mechanisms. Unfortunately, lightning on its own cannot be used as a general remote sensing tool because not all volcanic eruptions produce spark discharges. As pointed out by McNutt and Williams, 2010, only 30-35% of volcanoes maintain lightning storms. The absence of lightning in two thirds of all eruptions indicates that most volcanoes produce flows with 1) inefficient or limited granular charging processes or 2) dynamics that do not promote the charge separation that sets up coherent electric fields needed for lightning. Yet, even if the prerequisites for spark discharges are not met, it is difficult to argue for plumes which are completely electrostatically neutral. The problems permeating passive electromagnetic sensing may be overcome through the use of active methods which involve interrogating charged volcanic plumes with electromagnetic radiation. The scattering of electromagnetic waves has been a common method to retrieve the physical properties of collections of particles, specifically those which cannot be accessed directly. By modifying the standard Mie formulation, Klavcka et al., 2007 showed that surface charge may influence the extinction properties of grains if such particles are much smaller than the wavelength of the incident radiation. Based on this model, we posit that the properties of charged clouds of particles can be readily assessed using robust, existing infrastructure-the Global Positioning System. In the present work, we numerically explore the manner in which electrostatic charge on particles affect the propagation of electromagnetic waves through volcanic plumes. We show that, for the range of

  1. Simulation of ablation and plume dynamics under femtosecond double-pulse laser irradiation of aluminum: Comparison of atomistic and continual approaches

    NASA Astrophysics Data System (ADS)

    Fokin, Vladimir B.; Povarnitsyn, Mikhail E.; Levashov, Pavel R.

    2017-02-01

    We elaborated two numerical methods, two-temperature hydrodynamics and hybrid two-temperature molecular dynamics, which take into account basic mechanisms of a metal target response to ultrashort laser irradiation. The model used for the description of the electronic subsystem is identical for both approaches, while the ionic part is defined by an equation of state in hydrodynamics and by an interatomic potential in molecular dynamics. Since the phase diagram of the equation of state and corresponding potential match reasonably well, the dynamics of laser ablation obtained by both methods is quite similar. This correspondence can be considered as a first step towards the development of a self-consistent combined model. Two important processes are highlighted in simulations of double-pulse ablation: (1) the crater depth decrease as a result of recoil flux formation in the nascent plume when the delay between the pulses increases; (2) the plume reheating by the second pulse that gives rise to two- three-fold growth of the electron temperature with the delay varying from 0 to 200 ps.

  2. A Mass Spectrometry Study of Isotope Separation in the Laser Plume

    NASA Astrophysics Data System (ADS)

    Suen, Timothy Wu

    Accurate quantification of isotope ratios is critical for both preventing the development of illicit weapons programs in nuclear safeguards and identifying the source of smuggled material in nuclear forensics. While isotope analysis has traditionally been performed by mass spectrometry, the need for in situ measurements has prompted the development of optical techniques, such as laser-induced breakdown spectroscopy (LIBS) and laser ablation molecular isotopic spectrometry (LAMIS). These optical measurements rely on laser ablation for direct solid sampling, but several past studies have suggested that the distribution of isotopes in the ablation plume is not uniform. This study seeks to characterize isotope separation in the laser plume through the use of orthogonal-acceleration time-of-flight mass spectrometry. A silver foil was ablated with a Nd:YAG at 355 nm at an energy of 50 muJ with a spot size of 71 mum, for a fluence of 1.3 J/cm2 and an irradiance of 250 MW/cm2. Flat-plate repellers were used to sample the plume, and a temporal profile of the ions was obtained by varying the time delay on the high-voltage pulse. A spatial profile along the axis of the plume was generated by changing the position of the sample, which yielded snapshots of the isotopic composition with time. In addition, the reflectron time-of-flight system was used as an energy filter in conjunction with the repellers to sample slices of the laser plasma orthogonal to the plume axis. Mass spectrometry of the plume revealed a fast ion distribution and a slow ion distribution. Measurements taken across the entire plume showed the fast 109Ag ions slightly ahead in both space and time, causing the 107Ag fraction to drop to 0.34 at 3 mus, 4 mm from the sample surface. Although measurements centered on the near side of the plume did not show isotope separation, the slow ions on the far side of the plume included much more 109Ag than 107Ag. In addition to examining the isotope content of the ablation

  3. Pulsed laser ablation of complex oxides: The role of congruent ablation and preferential scattering for the film stoichiometry

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

    Wicklein, S.; Koehl, A.; Dittmann, R.

    2012-09-24

    By combining structural and chemical thin film analysis with detailed plume diagnostics and modeling of the laser plume dynamics, we are able to elucidate the different physical mechanisms determining the stoichiometry of the complex oxides model material SrTiO{sub 3} during pulsed laser deposition. Deviations between thin film and target stoichiometry are basically a result of two effects, namely, incongruent ablation and preferential scattering of lighter ablated species during their motion towards the substrate in the O{sub 2} background gas. On the one hand, a progressive preferential ablation of the Ti species with increasing laser fluence leads to a regime ofmore » Ti-rich thin film growth at larger fluences. On the other hand, in the low laser fluence regime, a more effective scattering of the lighter Ti plume species results in Sr rich films.« less

  4. Effects of Plume Hydrodynamics and Oxidation on the Composition of a Condensing Laser-Induced Plasma

    DOE PAGES

    Weisz, David G.; Crowhurst, Jonathan C.; Finko, Mikhail S.; ...

    2018-02-01

    High-temperature chemistry in laser ablation plumes leads to vapor-phase speciation, which can induce chemical fractionation during condensation. In this work, using emission spectroscopy acquired after ablation of a SrZrO 3 target, we have experimentally observed the formation of multiple molecular species (ZrO and SrO) as a function of time as the laser ablation plume evolves. Although the stable oxides SrO and ZrO 2 are both refractory, we observed emission from the ZrO intermediate at earlier times than SrO. We deduced the time-scale of oxygen entrainment into the laser ablation plume using an 18O 2 environment by observing the in-growth ofmore » Zr 18O in the emission spectra relative to Zr 16O, which was formed by reaction of Zr with 16O from the target itself. Using temporally resolved plume-imaging, we determined that ZrO formed more readily at early times, volumetrically in the plume, while SrO formed later in time, around the periphery. Lastly, using a simple temperature-dependent reaction model, we have illustrated that the formation sequence of these oxides subsequent to ablation is predictable to first order.« less

  5. EM Modelling of RF Propagation Through Plasma Plumes

    NASA Astrophysics Data System (ADS)

    Pandolfo, L.; Bandinelli, M.; Araque Quijano, J. L.; Vecchi, G.; Pawlak, H.; Marliani, F.

    2012-05-01

    Electric propulsion is a commercially attractive solution for attitude and position control of geostationary satellites. Hall-effect ion thrusters generate a localized plasma flow in the surrounding of the satellite, whose impact on the communication system needs to be qualitatively and quantitatively assessed. An electromagnetic modelling tool has been developed and integrated into the Antenna Design Framework- ElectroMagnetic Satellite (ADF-EMS). The system is able to guide the user from the plume definition phases through plume installation and simulation. A validation activity has been carried out and the system has been applied to the plume modulation analysis of SGEO/Hispasat mission.

  6. Plume radiation

    NASA Astrophysics Data System (ADS)

    Dirscherl, R.

    1993-06-01

    The electromagnetic radiation originating from the exhaust plume of tactical missile motors is of outstanding importance for military system designers. Both missile- and countermeasure engineer rely on the knowledge of plume radiation properties, be it for guidance/interference control or for passive detection of adversary missiles. To allow access to plume radiation properties, they are characterized with respect to the radiation producing mechanisms like afterburning, its chemical constituents, and reactions as well as particle radiation. A classification of plume spectral emissivity regions is given due to the constraints imposed by available sensor technology and atmospheric propagation windows. Additionally assessment methods are presented that allow a common and general grouping of rocket motor properties into various categories. These methods describe state of the art experimental evaluation techniques as well as calculation codes that are most commonly used by developers of NATO countries. Dominant aspects influencing plume radiation are discussed and a standardized test technique is proposed for the assessment of plume radiation properties that include prediction procedures. These recommendations on terminology and assessment methods should be common to all employers of plume radiation. Special emphasis is put on the omnipresent need for self-protection by the passive detection of plume radiation in the ultraviolet (UV) and infrared (IR) spectral band.

  7. Laser ablated copper plasmas in liquid and gas ambient

    NASA Astrophysics Data System (ADS)

    Kumar, Bhupesh; Thareja, Raj K.

    2013-05-01

    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 (ne) determined using Stark broadening of the Cu I (3d104d1 2D3/2-3d104p1 2P3/2 at 521.8 nm) line is estimated and compared for both plasma plumes. The electron temperature (Te) 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.

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

    DOEpatents

    Mashburn, Douglas N.

    1996-01-01

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

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

    DOEpatents

    Mashburn, D.N.

    1996-09-24

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

  10. Mass Spectrometric Imaging Using Laser Ablation and Solvent Capture by Aspiration (LASCA)

    NASA Astrophysics Data System (ADS)

    Brauer, Jonathan I.; Beech, Iwona B.; Sunner, Jan

    2015-09-01

    A novel interface for ambient, laser ablation-based mass spectrometric imaging (MSI) referred to as laser ablation and solvent capture by aspiration (LASCA) is presented and its performance demonstrated using selected, unaltered biological materials. LASCA employs a pulsed 2.94 μm laser beam for specimen ablation. Ablated materials in the laser plumes are collected on a hanging solvent droplet with electric field-enhanced trapping, followed by aspiration of droplets and remaining plume material in the form of a coarse aerosol into a collection capillary. The gas and liquid phases are subsequently separated in a 10 μL-volume separatory funnel, and the solution is analyzed with electrospray ionization in a high mass resolution Q-ToF mass spectrometer. The LASCA system separates the sampling and ionization steps in MSI and combines high efficiencies of laser plume sampling and of electrospray ionization (ESI) with high mass resolution MS. Up to 2000 different compounds are detected from a single ablation spot (pixel). Using the LASCA platform, rapid (6 s per pixel), high sensitivity, high mass-resolution ambient imaging of "as-received" biological material is achieved routinely and reproducibly.

  11. Femtosecond ablation applied to deep-drilling of hard metals

    NASA Astrophysics Data System (ADS)

    Bruneau, Sebastien; Hermann, Joerg; Dumitru, Gabriel; Sentis, Marc L.

    2004-09-01

    Mechanisms responsible for the limitation of the aspect ratio obtained by deep drilling of hard metals are investigated in the present work. Cemented carbide targets have been irradiated with laser pulses of 100 fs duration and 100 μJ maximum energy delivered by a Ti:sapphire laser system. The experiments are carried out in different gas environments (vacuum, air, helium up to atmospheric pressure) with incident laser fluences ranging from 1 to 20 Jcm-2. During deep drilling, the laser-induced ablation plume is characterized by means of in-situ plasma diagnostics. Fast imaging is used to observe the expansion behavior of the plasma plume whereas time- and space-resolved emission spectroscopy is employed to analyze the plasma composition. After irradiation, the laser-produced craters were examined by optical microscopy. A correlation between the ablation plume characteristics and the morphological changes of the mciro-holes is established. The results indicate that nanoclusters, that present a significant part of the ablated material, are responsbile for the alteration of the crater shape in the high laser fluence regime.

  12. Laser ablation for the synthesis of carbon nanotubes

    DOEpatents

    Holloway, Brian C; Eklund, Peter C; Smith, Michael W; Jordan, Kevin C; Shinn, Michelle

    2012-11-27

    Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces and output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

  13. Laser ablation for the synthesis of carbon nanotubes

    DOEpatents

    Holloway, Brian C.; Eklund, Peter C.; Smith, Michael W.; Jordan, Kevin C.; Shinn, Michelle

    2010-04-06

    Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces an output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

  14. Laser ablation for the synthesis of carbon nanotubes

    NASA Technical Reports Server (NTRS)

    Holloway, Brian C. (Inventor); Eklund, Peter C. (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Shinn, Michelle (Inventor)

    2010-01-01

    Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces an output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of side pumped, preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

  15. Laser ablation for the synthesis of carbon nanotubes

    NASA Technical Reports Server (NTRS)

    Holloway, Brian C. (Inventor); Eklund, Peter C. (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Shinn, Michelle (Inventor)

    2012-01-01

    Single walled carbon nanotubes are produced in a novel apparatus by the laser-induced ablation of moving carbon target. The laser used is of high average power and ultra-fast pulsing. According to various preferred embodiments, the laser produces and output above about 50 watts/cm.sup.2 at a repetition rate above about 15 MHz and exhibits a pulse duration below about 10 picoseconds. The carbon, carbon/catalyst target and the laser beam are moved relative to one another and a focused flow of "side pumped", preheated inert gas is introduced near the point of ablation to minimize or eliminate interference by the ablated plume by removal of the plume and introduction of new target area for incidence with the laser beam. When the target is moved relative to the laser beam, rotational or translational movement may be imparted thereto, but rotation of the target is preferred.

  16. Understanding plume splitting of laser ablated plasma: A view from ion distribution dynamics

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

    Wu, Jian; Li, Xingwen; Wei, Wenfu

    2013-11-15

    Plume splitting in low-pressure ambient air was understood in view of ion distribution dynamics from the laser ablated Al plasma (1064 nm 0.57 J/mm{sup 2}) by combining fast photography and spatially resolved spectroscopy. In the beginning, the spectral lines were mainly from the Al III ion. Then, the Bragg peak in stopping power of the ambient gas to Al III could be the dominant reason for the enhanced emission from the fast moving part, and the recombination of Al III to Al I-II ions near the target surface was response to the radiations from the slow moving/stationary part. As themore » ambient gas pressure increased, stopping distances of the Al III decreased, and radiation from the air ions became pronounced. The laser shadowgraph image at 1100 Pa indicated that the shock wave front located between the fast moving and slow moving parts. Electron densities of the fast moving plasma, which peaked at the plasma front, were on the order of 10{sup 16} cm{sup −3}, and the electron temperatures were 2–3 eV.« less

  17. Plasma plume expansion dynamics in nanosecond Nd:YAG laserosteotome

    NASA Astrophysics Data System (ADS)

    Abbasi, Hamed; Rauter, Georg; Guzman, Raphael; Cattin, Philippe C.; Zam, Azhar

    2018-02-01

    In minimal invasive laser osteotomy precise information about the ablation process can be obtained with LIBS in order to avoid carbonization, or cutting of wrong types of tissue. Therefore, the collecting fiber for LIBS needs to be optimally placed in narrow cavities in the endoscope. To determine this optimal placement, the plasma plume expansion dynamics in ablation of bone tissue by the second harmonic of a nanosecond Nd:YAG laser at 532 nm has been studied. The laserinduced plasma plume was monitored in different time delays, from one nanosecond up to one hundred microseconds. Measurements were performed using high-speed gated illumination imaging. The expansion features were studied using illumination of the overall visible emission by using a gated intensified charged coupled device (ICCD). The camera was capable of having a minimum gate width (Optical FWHM) of 3 ns and the timing resolution (minimum temporal shift of the gate) of 10 ps. The imaging data were used to generate position-time data of the luminous plasma-front. Moreover, the velocity of the plasma plume expansion was studied based on the time-resolved intensity data. By knowing the plasma plume profile over time, the optimum position (axial distance from the laser spot) of the collecting fiber and optimal time delay (to have the best signal to noise ratio) in spatial-resolved and time-resolved laser-induced breakdown spectroscopy (LIBS) can be determined. Additionally, the function of plasma plume expansion could be used to study the shock wave of the plasma plume.

  18. Computational Modeling of Ablation on an Irradiated Target

    NASA Astrophysics Data System (ADS)

    Mehmedagic, Igbal; Thangam, Siva

    2017-11-01

    Computational modeling of pulsed nanosecond laser interaction with an irradiated metallic target is presented. The model formulation involves ablation of the metallic target irradiated by pulsed high intensity laser at normal atmospheric conditions. Computational findings based on effective representation and prediction of the heat transfer, melting and vaporization of the targeting material as well as plume formation and expansion are presented along with its relevance for the development of protective shields. In this context, the available results for a representative irradiation from 1064 nm laser pulse is used to analyze various ablation mechanisms, variable thermo-physical and optical properties, plume expansion and surface geometry. Funded in part by U. S. Army ARDEC, Picatinny Arsenal, NJ.

  19. Dynamics of Molecular Emission Features from Nanosecond, Femtosecond Laser and Filament Ablation Plasmas

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

    Harilal, Sivanandan S.; Yeak, J.; Brumfield, Brian E.

    2016-06-15

    The evolutionary paths of molecular species and nanoparticles in laser ablation plumes are not well understood due to the complexity of numerous physical processes that occur simultaneously in a transient laser-plasma system. It is well known that the emission features of ions, atoms, molecules and nanoparticles in a laser ablation plume strongly depend on the laser irradiation conditions. In this letter we report the temporal emission features of AlO molecules in plasmas generated using a nanosecond laser, a femtosecond laser and filaments generated from a femtosecond laser. Our results show that, at a fixed laser energy, the persistence of AlOmore » is found to be highest and lowest in ns and filament laser plasmas respectively while molecular species are formed at early times for both ultrashort pulse (fs and filament) generated plasmas. Analysis of the AlO emission band features show that the vibrational temperature of AlO decays rapidly in filament assisted laser ablation plumes.« less

  20. Single-shot femtosecond laser ablation of gold surface in air and isopropyl alcohol

    NASA Astrophysics Data System (ADS)

    Kudryashov, S. I.; Saraeva, I. N.; Lednev, V. N.; Pershin, S. M.; Rudenko, A. A.; Ionin, A. A.

    2018-05-01

    Single-shot IR femtosecond-laser ablation of gold surfaces in ambient air and liquid isopropyl alcohol was studied by scanning electron microscopy characterization of crater topographies and time-resolved optical emission spectroscopy of ablative plumes in regimes, typical for non-filamentary and non-fragmentation laser production of nanoparticle sols. Despite one order of magnitude shorter (few nanoseconds) lifetimes and almost two orders of magnitude lower intensities of the quenched ablative plume emission in the alcohol ambient at the same peak laser fluence, craters for the dry and wet conditions appeared with rather similar nanofoam-like spallative topographies and the same thresholds. These facts envision the underlying surface spallation as one of the basic ablation mechanisms relevant for both dry and wet advanced femtosecond laser surface nano/micro-machining and texturing, as well as for high-throughput femtosecond laser ablative production of colloidal nanoparticles by MHz laser-pulse trains via their direct nanoscale jetting from the nanofoam in air and fluid environments.

  1. 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.

  2. 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.

  3. Laser ablation in an ambient gas: Modelling and experiment

    NASA Astrophysics Data System (ADS)

    Moscicki, Tomasz; Hoffman, Jacek; Szymanski, Zygmunt

    2018-02-01

    The laser ablation of graphite in ambient argon is studied both experimentally and theoretically in conditions corresponding to the initial conditions of carbon nanotube synthesis by the laser vaporization method. The results of the experiment show that the maximum plasma temperature of 24 000 K is reached 25 ns after the beginning of the laser pulse and decreases to about 4000-4500 K after 10 μs. The maximum electron density of 8 × 1025 m-3 is reached 15 ns from the beginning of the laser pulse. The hydrodynamic model applied shows comparable plasma temperatures and electron densities. The model also replicates well a shock wave and plume confinement—intrinsic features of supersonic flow of the ablated plume in an ambient gas. The results show that the theoretical model can be used to simulate nanosecond laser ablation in an ambient gas from the beginning of the process up to several microseconds.

  4. Comparative study of the expansion dynamics of laser-driven plasma and shock wave in in-air and underwater ablation regimes

    NASA Astrophysics Data System (ADS)

    Nguyen, Thao T. P.; Tanabe, Rie; Ito, Yoshiro

    2018-03-01

    We compared the expansion characteristics of the plasma plumes and shock waves generated in laser-induced shock process between the two ablation regimes: in air and under water. The observation was made from the initial moment when the laser pulse hit the target until 1.5 μs. The shock processes were driven by focusing a single laser pulse (1064 nm, FWHM = 13 ns) onto the surface of epoxy-resin blocks using a 40-mm focal length lens. The estimated laser intensity at the target plane is approximate to 9 ×109Wcm-2 . We used the fast-imaging technique to observe the expansion of the plasma plume and a custom-designed time-resolved photoelasticity imaging technique to observe the propagation of shock waves with the time resolution of nanoseconds. We found that at the same intensity of the laser beam, the plasma expansion during the laser pulse follows different mechanisms: the plasma plume that grows in air follows a radiation-wave model while a detonation-wave model can explain the expansion of the plasma plume induced in water. The ideal blast wave theory can be used to predict the decay of the shock wave in air but is not appropriate to describe the decay of the shock wave induced under water.

  5. Impact of oxygen chemistry on the emission and fluorescence spectroscopy of laser ablation plumes

    NASA Astrophysics Data System (ADS)

    Hartig, K. C.; Brumfield, B. E.; Phillips, M. C.; Harilal, S. S.

    2017-09-01

    Oxygen present in the ambient gas medium may affect both laser-induced breakdown spectroscopy (LIBS) and laser-induced fluorescence (LIF) emission through a reduction of emission intensity and persistence. In this study, an evaluation is made on the role of oxygen in the ambient environment under atmospheric pressure conditions in LIBS and laser ablation (LA)-LIF emission. To generate plasmas, 1064 nm, 10 ns pulses were focused on an aluminum alloy sample. LIF was performed by frequency scanning a CW laser over the 396.15 nm (3s24s 2S1/2 → 3s23p 2P°3/2) Al I transition. Time-resolved emission and fluorescence signals were recorded to evaluate the variation in emission intensity caused by the presence of oxygen. The oxygen partial pressure (po) in the atmospheric pressure environment using N2 as the makeup gas was varied from 0 to 400 Torr O2. 2D-fluorescence spectroscopy images were obtained for various oxygen concentrations for simultaneous evaluation of the emission and excitation spectral features. Results showed that the presence of oxygen in the ambient environment reduces the persistence of the LIBS and LIF emission through an oxidation process that depletes the density of atomic species within the resulting laser-produced plasma (LPP) plume.

  6. Effect of mass and density of ambient gas on the interaction of laser-blow-off plasma plumes propagating in close proximity

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

    Kumar, Bhupesh; Singh, R. K.; Kumar, Ajai, E-mail: ajai@ipr.res.in

    2016-04-15

    The effects of mass and pressure of ambient gas on the propagation dynamics of two laser-blow-off plasma plumes created in close proximity are investigated. A time gated fast imaging technique is used for recording the images of the laterally colliding plumes under different experimental conditions. Pressure is varied from 0.1 to 3 mbar in three ambient, i.e., helium, neon, and argon. Emphasis is given on the nature of shock-shock interaction under different ambient conditions. It has been observed that the shock-velocity, shape, strength, and their interactions are strongly dependent on the mass and density of the ambient gases. The rolemore » of the interacting shocks and their subsequent reflections on the formation and geometrical shape of the interaction region in different ambient conditions is briefly described.« less

  7. Dynamical Study of Femtosecond-Laser-Ablated Liquid-Aluminum Nanoparticles Using Spatiotemporally Resolved X-Ray-Absorption Fine-Structure Spectroscopy

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

    Oguri, Katsuya; Okano, Yasuaki; Nishikawa, Tadashi

    2007-10-19

    We study the temperature evolution of aluminum nanoparticles generated by femtosecond laser ablation with spatiotemporally resolved x-ray-absorption fine-structure spectroscopy. We successfully identify the nanoparticles based on the L-edge absorption fine structure of the ablation plume in combination with the dependence of the edge structure on the irradiation intensity and the expansion velocity of the plume. In particular, we show that the lattice temperature of the nanoparticles is estimated from the L-edge slope, and that its spatial dependence reflects the cooling of the nanoparticles during plume expansion. The results reveal that the emitted nanoparticles travel in a vacuum as a condensedmore » liquid phase with a lattice temperature of about 2500 to 4200 K in the early stage of plume expansion.« less

  8. Study of Mn laser ablation in methane atmosphere

    NASA Astrophysics Data System (ADS)

    Krstulović, N.; Labazan, I.; Milošević, S.

    2006-02-01

    Laser ablation of Mn target in vacuum and in the presence of CH4 was studied under 308 nm laser irradiation. Time-resolved emission using gated detection and scanning monochromator and absorption using the cavity ring-down spectroscopy were used to study vaporized plume. In the CH4 atmosphere we observed transitions identified as C2 and MnH bands, while these spectral features were not detected in emission spectra. This is a clear evidence of importance in combining both spectroscopic techniques in laser vaporized plume study.

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

    NASA Astrophysics Data System (ADS)

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

    2009-10-01

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

  10. [INVITED] Control of femtosecond pulsed laser ablation and deposition by temporal pulse shaping

    NASA Astrophysics Data System (ADS)

    Garrelie, Florence; Bourquard, Florent; Loir, Anne--Sophie; Donnet, Christophe; Colombier, Jean-Philippe

    2016-04-01

    This study explores the effects of temporal laser pulse shaping on femtosecond pulsed laser deposition (PLD). The potential of laser pulses temporally tailored on ultrafast time scales is used to control the expansion and the excitation degree of ablation products including atomic species and nanoparticles. The ablation plume generated by temporally shaped femtosecond pulsed laser ablation of aluminum and graphite targets is studied by in situ optical diagnostic methods. Taking advantage of automated pulse shaping techniques, an adaptive procedure based on spectroscopic feedback regulates the irradiance for the enhancement of typical plasma features. Thin films elaborated by unshaped femtosecond laser pulses and by optimized sequence indicate that the nanoparticles generation efficiency is strongly influenced by the temporal shaping of the laser irradiation. The ablation processes leading either to the generation of the nanoparticles either to the formation of plasma can be favored by using a temporal shaping of the laser pulse. Insights are given on the possibility to control the quantity of the nanoparticles. The temporal laser pulse shaping is shown also to strongly modify the laser-induced plasma contents and kinetics for graphite ablation. Temporal pulse shaping proves its capability to reduce the number of slow radicals while increasing the proportion of monomers, with the addition of ionized species in front of the plume. This modification of the composition and kinetics of plumes in graphite ablation using temporal laser pulse shaping is discussed in terms of modification of the structural properties of deposited Diamond-Like Carbon films (DLC). This gives rise to a better understanding of the growth processes involved in femtosecond-PLD and picosecond-PLD of DLC suggesting the importance of neutral C atoms, which are responsible for the subplantation process.

  11. Infrared laser ablation of polymeric nanocomposites: A study of surface structure and plume formation

    NASA Astrophysics Data System (ADS)

    Bartolucci, S. F.; Miller, M. J.; Warrender, J. M.

    2016-12-01

    The behavior of carbon nanotube composites subjected to laser pulse heating with a 1070 nm variable pulse duration laser has been studied. Previous work has shown that carbon nanotube composites form a protective network on the surface of a composite, which reduces heat input to the underlying polymer and slows mass loss. In this work, we have studied the interaction between the incident laser and the plume formed above the composite. We have correlated these interactions with features observed in the time-resolved mass loss data and confirmed them with observations using high-speed video of the laser irradiations. Beam interactions were studied as a function of laser irradiance and nanotube content. It is shown that beam-plume interactions occur for the carbon nanotube composites and that the interactions occur at shorter pulse durations for increased nanotube content and laser irradiance. When we eliminate beam-plume interaction through alteration of the sample orientation relative to the incident beam, we are able to elucidate the individual contributions of the carbon nanotube surface network and the plume to the observed decrease in mass loss after laser irradiation. We examine the plume content using microscopy and Raman spectroscopy and show that greater beam absorption occurs when there is a higher graphitic content in the plume.

  12. ON THE PARALLEL AND PERPENDICULAR PROPAGATING MOTIONS VISIBLE IN POLAR PLUMES: AN INCUBATOR FOR (FAST) SOLAR WIND ACCELERATION?

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

    Liu, Jiajia; Wang, Yuming; McIntosh, Scott W.

    We combine observations of the Coronal Multi-channel Polarimeter and the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory to study the characteristic properties of (propagating) Alfvénic motions and quasi-periodic intensity disturbances in polar plumes. This unique combination of instruments highlights the physical richness of the processes taking place at the base of the (fast) solar wind. The (parallel) intensity perturbations with intensity enhancements around 1% have an apparent speed of 120 km s{sup −1} (in both the 171 and 193 Å passbands) and a periodicity of 15 minutes, while the (perpendicular) Alfvénic wave motions have a velocity amplitude ofmore » 0.5 km s{sup −1}, a phase speed of 830 km s{sup −1}, and a shorter period of 5 minutes on the same structures. These observations illustrate a scenario where the excited Alfvénic motions are propagating along an inhomogeneously loaded magnetic field structure such that the combination could be a potential progenitor of the magnetohydrodynamic turbulence required to accelerate the fast solar wind.« less

  13. On possible plume-guided seismic waves

    USGS Publications Warehouse

    Julian, B.R.; Evans, J.R.

    2010-01-01

    Hypothetical thermal plumes in the Earth's mantle are expected to have low seismic-wave speeds and thus would support the propagation of guided elastic waves analogous to fault-zone guided seismic waves, fiber-optic waves, and acoustic waves in the oceanic SOund Fixing And Ranging channel. Plume-guided waves would be insensitive to geometric complexities in the wave guide, and their dispersion would make them distinctive on seismograms and would provide information about wave-guide structure that would complement seismic tomography. Detecting such waves would constitute strong evidence of a new kind for the existence of plumes. A cylindrical channel embedded in an infinite medium supports two classes of axially symmetric elastic-wave modes, torsional and longitudinal-radial. Torsional modes have rectilinear particle motion tangent to the cylinder surface. Longitudinal-radial modes have elliptical particle motion in planes that include the cylinder axis, with retrograde motion near the axis. The direction of elliptical particle motion reverses with distance from the axis: once for the fundamental mode, twice for the first overtone, and so on. Each mode exists only above its cut-off frequency, where the phase and group speeds equal the shear-wave speed in the infinite medium. At high frequencies, both speeds approach the shear-wave speed in the channel. All modes have minima in their group speeds, which produce Airy phases on seismograms. For shear wave-speed contrasts of a few percent, thought to be realistic for thermal plumes in the Earth, the largest signals are inversely dispersed and have dominant frequencies of about 0.1-1 Hz and durations of 15-30 sec. There are at least two possible sources of observable plume waves: (1) the intersection of mantle plumes with high-amplitude core-phase caustics in the deep mantle; and (2) ScS-like reflection at the core-mantle boundary of downward-propagating guided waves. The widespread recent deployment of broadband

  14. Interplay of wavelength, fluence and spot-size in free-electron laser ablation of cornea.

    PubMed

    Hutson, M Shane; Ivanov, Borislav; Jayasinghe, Aroshan; Adunas, Gilma; Xiao, Yaowu; Guo, Mingsheng; Kozub, John

    2009-06-08

    Infrared free-electron lasers ablate tissue with high efficiency and low collateral damage when tuned to the 6-microm range. This wavelength-dependence has been hypothesized to arise from a multi-step process following differential absorption by tissue water and proteins. Here, we test this hypothesis at wavelengths for which cornea has matching overall absorption, but drastically different differential absorption. We measure etch depth, collateral damage and plume images and find that the hypothesis is not confirmed. We do find larger etch depths for larger spot sizes--an effect that can lead to an apparent wavelength dependence. Plume imaging at several wavelengths and spot sizes suggests that this effect is due to increased post-pulse ablation at larger spots.

  15. Composition of the excimer laser-induced plume produced during LASIK refractive surgery

    NASA Astrophysics Data System (ADS)

    Glickman, Randolph D.; Liu, Yun; Mayo, George L.; Baribeau, Alan D.; Starck, Tomy; Bankhead, Tom

    2003-07-01

    Because of concerns about potential hazards to surgical personnel of the plume associated with laser refractive surgery, this study was performed to characterize the composition of such plumes. Filter elements were removed from the smoke evacuator of a VISX S3 excimer laser (filter pore size ~0.3 microns) and from a Mastel Clean Room ( filter pore size ~0.2 microns) used with a LADARVISION excimer laser. The filters from both laser systems captured the laser-induced plumes from multiple, routine, LASIK patient procedures. Some filters were processed for scanning electron microscopy, while others were extracted with methanol and chloroform for biochemical analysis. Both the VISX "Final Air" filter and the Mastel "Clean Room" filter captured material that was not observed in filters that had clean operating room air only passed through them. In the VISX system, air flows through the filter unit parallel to the filter matrix. SEM analysis showed these filters captured discrete particles of 0.3 to 3.0 microns in size. In the Mastel Clean Room unit, air flows orthogonally through the filter, and the filter matrix was heavily layered with captured debris so that individual particles were not readily distinguished. Amino acid analysis and gel electrophoresis of extracted material revealed proteinaceous molecules as large as 5000 molecular weight. Such large molecules in the laser plume are not predicted by the existing theory of photochemical ablation. The presence of relatively large biomolecules may constitute a risk of allergenic reactions in personnel exposed to the plume, and also calls into question the precise mechanism of excimer laser photochemical ablation. Supported by the RMG Research Endowment, and Research to Prevent Blindness

  16. Evaluation of pressure in a plasma produced by laser ablation of steel

    NASA Astrophysics Data System (ADS)

    Hermann, Jörg; Axente, Emanuel; Craciun, Valentin; Taleb, Aya; Pelascini, Frédéric

    2018-05-01

    We investigated the time evolution of pressure in the plume generated by laser ablation with ultraviolet nanosecond laser pulses in a near-atmospheric argon atmosphere. These conditions were previously identified to produce a plasma of properties that facilitate accurate spectroscopic diagnostics. Using steel as sample material, the present investigations benefit from the large number of reliable spectroscopic data available for iron. Recording time-resolved emission spectra with an echelle spectrometer, we were able to perform accurate measurements of electron density and temperature over a time interval from 200 ns to 12 μs. Assuming local thermodynamic equilibrium, we computed the plasma composition within the ablated vapor material and the corresponding kinetic pressure. The time evolution of plume pressure is shown to reach a minimum value below the pressure of the background gas. This indicates that the process of vapor-gas interdiffusion has a negligible influence on the plume expansion dynamics in the considered timescale. Moreover, the results promote the plasma pressure as a control parameter in calibration-free laser-induced breakdown spectroscopy.

  17. Plume interference with space shuttle range safety signals

    NASA Technical Reports Server (NTRS)

    Boynton, F. P.; Rajaseknar, P. S.

    1979-01-01

    The computational procedure for signal propagation in the presence of an exhaust plume is presented. Comparisons with well-known analytic diffraction solutions indicate that accuracy suffers when mesh spacing is inadequate to resolve the first unobstructed Fresnel zone at the plume edge. Revisions to the procedure to improve its accuracy without requiring very large arrays are discussed. Comparisons to field measurements during a shuttle solid rocket motor (SRM) test firing suggest that the plume is sharper edged than one would expect on the basis of time averaged electron density calculations. The effects, both of revisions to the computational procedure and of allowing for a sharper plume edge, are to raise the signal level near tail aspect. The attenuation levels then predicted are still high enough to be of concern near SRM burnout for northerly launches of the space shuttle.

  18. Analysis of plume emissions after papovavirus irradiation with the carbon dioxide laser

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

    Bellina, J.H.; Stjernholm, R.L.; Kurpel, J.E.

    1982-05-01

    This study was undertaken to evaluate potential inhalation hazards to operating room personnel after irradiation of tumors with the carbon dioxide laser. Cellular debris was analyzed for viability using labeled nucleotides and labeled glucose. In this way the plume was investigated for the presence of material with oncogenic potential. Most surgeons who have ablated venereal warts or certain tumors with the carbon dioxide laser have worried about possible hazards of inhaling the vapor that is produced as a result of their work. We utilized three methods to determine whether viable particles exist in the laser plume. Fortunately, it is mostmore » comforting that the metabolic studies, DNA and RNA studies and cytologic studies seem to indicate that the plume is biologically inactive.« less

  19. Double-pulse femtosecond laser peening of aluminum alloy AA5038: Effect of inter-pulse delay on transient optical plume emission and final surface micro-hardness

    NASA Astrophysics Data System (ADS)

    Ageev, E. I.; Bychenkov, V. Yu.; Ionin, A. A.; Kudryashov, S. I.; Petrov, A. A.; Samokhvalov, A. A.; Veiko, V. P.

    2016-11-01

    Double-pulse ablative femtosecond laser peening of the AA5038 aluminum alloy surface in the phase explosion regime results in its enhanced microhardness, which monotonously decreases till the initial value versus inter-pulse delay, increasing on a sub-nanosecond timescale. Optical emission spectroscopy of the double-pulse ablative plume reveals the same trend in the yield of the corresponding atomic and ion emission versus inter-pulse delay, enlightening the interaction of the second femtosecond laser pump pulse with the surface and the resulting plume.

  20. Consequences of Femtosecond Laser Filament Generation Conditions in Standoff Laser Induced Breakdown Spectroscopy

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

    Harilal, Sivanandan S.; Yeak, J.; Brumfield, Brian E.

    2016-08-08

    We investigate the role of femtosecond laser focusing conditions on ablation properties and its implications on analytical merits and standoff detection applications. Femtosecond laser pulses can be used for ablation either by tightly focusing or by using filaments generated during its propagation. We evaluated the persistence of atomic, and molecular emission features as well as time evolution of the fundamental properties (temperature and density) of ablation plumes generated using different methods.

  1. Unsteady motion of laser ablation plume by vortex induced by the expansion of curved shock wave

    NASA Astrophysics Data System (ADS)

    Tran, D. T.; Mori, K.

    2017-02-01

    There are a number of industrial applications of laser ablation in a gas atmosphere. When an intense pulsed laser beam is irradiated on a solid surface in the gas atmosphere, the surface material is ablated and expands into the atmosphere. At the same time, a spherical shock wave is launched by the ablation jet to induce the unsteady flow around the target surface. The ablated materials, luminously working as tracer, exhibit strange unsteady motions depending on the experimental conditions. By using a high-speed video camera (HPV-X2), unsteady motion ablated materials are visualized at the frame rate more than 106 fps, and qualitatively characterized.

  2. Subduction disfigured mantle plumes: Plumes that are not plumes?

    NASA Astrophysics Data System (ADS)

    Druken, K. A.; Stegman, D. R.; Kincaid, C. R.; Griffiths, R. W.

    2012-12-01

    "Hotspot" volcanism is generally attributed to upwelling of anomalously warm mantle plumes, the intra-plate Hawaiian island chain and its simple age progression serving as an archetypal example. However, interactions of such plumes with plate margins, and in particular with subduction zones, is likely to have been a common occurrence and leads to more complicated geological records. Here we present results from a series of complementary, three-dimensional numerical and laboratory experiments that examine the dynamic interaction between negatively buoyant subducting slabs and positively buoyant mantle plumes. Slab-driven flow is shown to significantly influence the evolution and morphology of nearby plumes, which leads to a range of deformation regimes of the plume head and conduit. The success or failure of an ascending plume head to reach the lithosphere depends on the combination of plume buoyancy and position within the subduction system, where the mantle flow owing to downdip and rollback components of slab motion entrain plume material both vertically and laterally. Plumes rising within the sub-slab region tend to be suppressed by the surrounding flow field, while wedge-side plumes experience a slight enhancement before ultimately being entrained by subduction. Hotspot motion is more complex than that expected at intraplate settings and is primarily controlled by position alone. Regimes include severely deflected conduits as well as retrograde (corkscrew) motion from rollback-driven flow, often with weak and variable age-progression. The interaction styles and surface manifestations of plumes can be predicted from these models, and the results have important implications for potential hotspot evolution near convergent margins.

  3. Why the SL9 Plumes Were All About the Same Height

    NASA Technical Reports Server (NTRS)

    Zahnle, K.; MacLow, M.-M.; Cuzzi, Jeffery N. (Technical Monitor)

    1995-01-01

    Several of the SL9 ejecta plumes were observed by the HST to reach approximately the same height, about 3000 km above the jovian cloud tops. The duration of the infrared events, which were produced by the plume falling back on the atmosphere, measures time aloft and hence provides a second, more sensitive measure of plume height; the light curves indicate that the largest impacts produced modestly higher plumes. Evidently these plumes were launched with about the same vertical velocity, roughly 10-13 kilometers per second. As the impactors themselves were not all the same, nor the impacts equally luminous, nor the plumes equally opaque, the similar plume heights has been seen as a puzzle needing explanation. A second, closely related matter that needs to addressed quantitatively is the popular contention that a big plume requires a big impact. This view is misleading at best, yet plume heights can be used to constrain impact parameters. Dimensional analysis indicates that plume height goes as z alpha v (sup 2) (sub ej) alpha E/pH (sup 2), where v (sub ej) is the ejection velocity, E the explosion energy, and p and H the ambient pressure and scale height at termination. Using a semi-analytic model for the deceleration, disintegration, and destruction of intruding bodies by an ever-vigilant atmosphere, we find that the ratio E/pH(sup 2) is roughly constant for fragments with diameters of order 100 m to 1000 m. Constancy of v(sub ej) is in part due to the greater role of radiative ablation on the flight of smaller objects. We conclude that similar plume heights is a direct consequence of smaller impactors exploding at higher altitudes, in such a way that the different explosions were geometrically similar.

  4. Confluence or independence of microwave plasma bullets in atmospheric argon plasma jet plumes

    NASA Astrophysics Data System (ADS)

    Li, Ping; Chen, Zhaoquan; Mu, Haibao; Xu, Guimin; Yao, Congwei; Sun, Anbang; Zhou, Yuming; Zhang, Guanjun

    2018-03-01

    Plasma bullet is the formation and propagation of a guided ionization wave (streamer), normally generated in atmospheric pressure plasma jet (APPJ). In most cases, only an ionization front produces in a dielectric tube. The present study shows that two or three ionization fronts can be generated in a single quartz tube by using a microwave coaxial resonator. The argon APPJ plumes with a maximum length of 170 mm can be driven by continuous microwaves or microwave pulses. When the input power is higher than 90 W, two or three ionization fronts propagate independently at first; thereafter, they confluence to form a central plasma jet plume. On the other hand, the plasma bullets move independently as the lower input power is applied. For pulsed microwave discharges, the discharge images captured by a fast camera show the ionization process in detail. Another interesting finding is that the strongest lightening plasma jet plumes always appear at the shrinking phase. Both the discharge images and electromagnetic simulations suggest that the confluence or independent propagation of plasma bullets is resonantly excited by the local enhanced electric fields, in terms of wave modes of traveling surface plasmon polaritons.

  5. Near field interaction of microwave signals with a bounded plasma plume

    NASA Technical Reports Server (NTRS)

    Ling, Hao; Hallock, Gary A.; Kim, Hyeongdong; Birkner, Bjorn

    1991-01-01

    The objective was to study the effect of the arcjet thruster plume on the performance of an onboard satellite reflector antenna. A project summary is presented along with sections on plasma and electromagnetic modeling. The plasma modeling section includes the following topics: wave propagation; plasma analysis; plume electron density model; and the proposed experimental program. The section on electromagnetic modeling includes new developments in ray modeling and the validation of three dimensional ray results.

  6. Modeling a three-dimensional river plume over continental shelf using a 3D unstructured grid model

    USGS Publications Warehouse

    Cheng, R.T.; Casulli, V.; ,

    2004-01-01

    River derived fresh water discharging into an adjacent continental shelf forms a trapped river plume that propagates in a narrow region along the coast. These river plumes are real and they have been observed in the field. Many previous investigations have reported some aspects of the river plume properties, which are sensitive to stratification, Coriolis acceleration, winds (upwelling or downwelling), coastal currents, and river discharge. Numerical modeling of the dynamics of river plumes is very challenging, because the complete problem involves a wide range of vertical and horizontal scales. Proper simulations of river plume dynamics cannot be achieved without a realistic representation of the flow and salinity structure near the river mouth that controls the initial formation and propagation of the plume in the coastal ocean. In this study, an unstructured grid model was used for simulations of river plume dynamics allowing fine grid resolution in the river and in regions near the coast with a coarse grid in the far field of the river plume in the coastal ocean, in the vertical, fine fixed levels were used near the free surface, and coarse vertical levels were used over the continental shelf. The simulations have demonstrated the uniquely important role played by Coriolis acceleration. Without Coriolis acceleration, no trapped river plume can be formed no matter how favorable the ambient conditions might be. The simulation results show properties of the river plume and the characteristics of flow and salinity within the estuary; they are completely consistent with the physics of estuaries and coastal oceans.

  7. Debris Albedo from Laser Ablation in Low and High Vacuum: Comparisons to Hypervelocity Impact

    NASA Astrophysics Data System (ADS)

    Radhakrishnan, G.; Adams, P. M.; Alaan, D. R.; Panetta, C. J.

    The albedo of orbital debris fragments in space is a critical parameter used in the derivation of their physical sizes from optical measurements. The change in albedo results from scattering due to micron and sub-micron particles on the surface. There are however no known hypervelocity collision ground tests that simulate the high-vacuum conditions on-orbit. While hypervelocity impact experiments at a gun range can offer a realistic representation of the energy of impact and fragmentation, and can aid the understanding of albedo, they are conducted in low-pressure air that is not representative of the very high vacuum of 10-8 Torr or less that exists in the Low Earth Orbit environment. Laboratory simulation using laser ablation with a high power laser, on the same target materials as used in current satellite structures, is appealing because it allows for well-controlled investigations that can be coupled to optical albedo (reflectance) measurements of the resultant debris. This relatively low-cost laboratory approach can complement the significantly more elaborate and expensive field-testing of single-shot hypervelocity impact on representative satellite structures. Debris generated is optically characterized with UV-VIS-NIR reflectance, and particle size distributions can be measured. In-situ spectroscopic diagnostics (nanosecond time frame) provide an identification of atoms and ions in the plume, and plasma temperatures, allowing a correlation of the energetics of the ablated plume with resulting albedo and particle size distributions of ablated debris. Our laboratory experiments offer both a high-vacuum environment, and selection of any gaseous ambient, at any controlled pressure, thus allowing for comparison to the hypervelocity impact experiments in low-pressure air. Initial results from plume analysis, and size distribution and microstructure of debris collected on witness plates show that laser ablations in low-pressure air offer many similarities to the

  8. Tracing the plasma interactions for pulsed reactive crossed-beam laser ablation

    NASA Astrophysics Data System (ADS)

    Chen, Jikun; Stender, Dieter; Pichler, Markus; Döbeli, Max; Pergolesi, Daniele; Schneider, Christof W.; Wokaun, Alexander; Lippert, Thomas

    2015-10-01

    Pulsed reactive crossed-beam laser ablation is an effective technique to govern the chemical activity of plasma species and background molecules during pulsed laser deposition. Instead of using a constant background pressure, a gas pulse with a reactive gas, synchronized with the laser beam, is injected into vacuum or a low background pressure near the ablated area of the target. It intercepts the initially generated plasma plume, thereby enhancing the physicochemical interactions between the gaseous environment and the plasma species. For this study, kinetic energy resolved mass-spectrometry and time-resolved plasma imaging were used to study the physicochemical processes occurring during the reactive crossed beam laser ablation of a partially 18O substituted La0.6Sr0.4MnO3 target using oxygen as gas pulse. The characteristics of the ablated plasma are compared with those observed during pulsed laser deposition in different oxygen background pressures.

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

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

    Katzy, R.; Singer, M.; Izadnia, S.

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

  10. Slowing of Femtosecond Laser-Generated Nanoparticles in a Background Gas

    DOE PAGES

    Rouleau, Christopher M.; Puretzky, Alexander A.; Geohegan, David B.

    2014-11-25

    The slowing of Pt nanoparticles in argon background gas was characterized by Rayleigh scattering imaging using a plume of nanoparticles generated by femtosecond laser through thin film ablation (fs-TTFA) of 20 nanometers-thick Pt films. The ablation was performed at threshold laser energy fluences for complete film removal to provide a well-defined plume consisting almost entirely of nanoparticles traveling with a narrow velocity distribution, providing a unique system to unambiguously characterize the slowing of nanoparticles during interaction with background gases. Nanoparticles of ~200 nm diameter were found to decelerate in background Ar gas with pressures less than 50 Torr in goodmore » agreement with a linear drag model in the Epstein regime. Based on this model, the stopping distance of small nanoparticles in the plume was predicted and tested by particle collection in an off-axis geometry, and size distribution analysis by transmission electron microscopy. These results permit a basis to interpret nanoparticle propagation through background gases in laser ablation plumes that contain mixed components.« less

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

    Rouleau, Christopher M.; Puretzky, Alexander A.; Geohegan, David B.

    The slowing of Pt nanoparticles in argon background gas was characterized by Rayleigh scattering imaging using a plume of nanoparticles generated by femtosecond laser through thin film ablation (fs-TTFA) of 20 nanometers-thick Pt films. The ablation was performed at threshold laser energy fluences for complete film removal to provide a well-defined plume consisting almost entirely of nanoparticles traveling with a narrow velocity distribution, providing a unique system to unambiguously characterize the slowing of nanoparticles during interaction with background gases. Nanoparticles of ~200 nm diameter were found to decelerate in background Ar gas with pressures less than 50 Torr in goodmore » agreement with a linear drag model in the Epstein regime. Based on this model, the stopping distance of small nanoparticles in the plume was predicted and tested by particle collection in an off-axis geometry, and size distribution analysis by transmission electron microscopy. These results permit a basis to interpret nanoparticle propagation through background gases in laser ablation plumes that contain mixed components.« less

  12. Emission spectroscopy analysis during Nopal cladodes dethorning by laser ablation

    NASA Astrophysics Data System (ADS)

    Peña-Díaz, M.; Ponce, L.; Arronte, M.; Flores, T.

    2007-04-01

    Optical emission spectroscopy of the pulsed laser ablation of spines and glochids from Opuntia (Nopal) cladodes was performed. Nopal cladodes were irradiated with Nd:YAG free-running laser pulses on their body, glochids and spines. Emission spectroscopy analyses in the 350-1000 nm region of the laser induced plasma were made. Plasma plume evolution characterization, theoretical calculations of plasma plume temperature and experiments varying the processing atmosphere showed that the process is dominated by a thermally activated combustion reaction which increases the dethorning process efficiency. Therefore, appropriate laser pulse energy for minimal damage of cladodes body and in the area beneath glochids and spines can be obtained.

  13. Implementation of microwave transmissions for rocket exhaust plume diagnostics

    NASA Astrophysics Data System (ADS)

    Coutu, Nicholas George

    Rocket-launched vehicles produce a trail of exhaust that contains ions, free electrons, and soot. The exhaust plume increases the effective conductor length of the rocket. A conductor in the presence of an electric field (e.g. near the electric charge stored within a cloud) can channel an electric discharge. The electrical conductivity of the exhaust plume is related to its concentration of free electrons. The risk of a lightning strike in-flight is a function of both the conductivity of the body and its effective length. This paper presents an approach that relates the electron number density of the exhaust plume to its propagation constant. Estimated values of the collision frequency and electron number density generated from a numerical simulation of a rocket plume are used to guide the design of the experimental apparatus. Test par meters are identified for the apparatus designed to transmit a signal sweep form 4 GHz to 7 GHz through the exhaust plume of a J-class solid rocket motor. Measurements of the scattering parameters imply that the transmission does not penetrate the plume, but instead diffracts around it. The electron density 20 cm downstream from the nozzle exit is estimated to be between 2.7x1014 m--3 and 5.6x10 15 m--3.

  14. The 2010 Eyjafjallajökull and 2011 Grimsvötn ash plumes as seen by GPS

    NASA Astrophysics Data System (ADS)

    Grapenthin, R.; Hreinsdottir, S.; Gudmundsson, M. T.

    2015-12-01

    The injection of a volcanic plume introduces a dynamic, localized, short-term heterogeneity in the atmosphere. Satellite-imagery based remote sensing techniques provide good spatial coverage for the detection of such plumes, but slow satellite repeat times (>30 minutes) and cloud cover can delay, if not entirely prevent, the detection. GPS, in turn, provides excellent temporal coverage, but requires favorable satellite-station-geometry such that the signal propagates through the plume if it is to be used for plume detection and analysis. Two methods exist to detect / analyze ash plumes with GPS: (a) Ash-heavy plumes result in signal dispersion and hence a lowered signal-to-noise ratio (SNR). A lowered SNR, recorded by some receivers, can provide useful information about the plume, such as location and velocity of ascent. These data can be evaluated directly as they are recorded by the receiver; without the need of solving for a receiver's position. (b) Wet plumes refract the GPS signals piercing the plume and hence induce a propagation delay. When solving for a receiver position GPS analysis tools do not model this localized phase delay effect and solutions for plume-piercing satellites do not fit the data well. This can be exploited for plume analysis such as the estimation of changes to the atmospheric refractivity index. We analyze GPS data of the ~2 month 2010 Eyafjallajökull erption and the week-long 2011 Grímsvötn eruption to infer a first order estimate of plume geometry and its progression. Using SNR and phase delay information, we evaluate the evolution of the partitioning of wet versus dry parts of the plume. During the GPS processing we iteratively solve for phase-delay and position and fix other parameters, hence reducing the mapping of least-squares misfit into position estimates and other parameters. Nearly continuous webcam imagery provides independent observations of first-order plume characteristics for the Eyafjallajökull event.

  15. Experimental and computational study of the effect of 1 atm background gas on nanoparticle generation in femtosecond laser ablation of metals

    NASA Astrophysics Data System (ADS)

    Wu, Han; Wu, Chengping; Zhang, Nan; Zhu, Xiaonong; Ma, Xiuquan; Zhigilei, Leonid V.

    2018-03-01

    Laser ablation of metal targets is actively used for generation of chemically clean nanoparticles for a broad range of practical applications. The processes involved in the nanoparticle formation at all relevant spatial and temporal scales are still not fully understood, making the precise control of the size and shape of the nanoparticles challenging. In this paper, a combination of molecular dynamics simulations and experiments is applied to investigate femtosecond laser ablation of aluminum targets in vacuum and in 1 atm argon background gas. The results of the simulations reveal a strong effect of the background gas environment on the initial plume expansion and evolution of the nanoparticle size distribution. The suppression of the generation of small/medium-size Al clusters and formation of a dense layer at the front of the expanding ablation plume, observed during the first nanosecond of the plume expansion in a simulation performed in the gas environment, have important implications on the characteristics of the nanoparticles deposited on a substrate and characterized in the experiments. The nanoparticles deposited in the gas environment are found to be more round-shaped and less flattened as compared to those deposited in vacuum. The nanoparticle size distributions exhibit power-law dependences with similar values of exponents obtained from fitting experimental and simulated data. Taken together, the results of this study suggest that the gas environment may be effectively used to control size and shape of nanoparticles generated by laser ablation.

  16. Space Shuttle Plume and Plume Impingement Study

    NASA Technical Reports Server (NTRS)

    Tevepaugh, J. A.; Penny, M. M.

    1977-01-01

    The extent of the influence of the propulsion system exhaust plumes on the vehicle performance and control characteristics is a complex function of vehicle geometry, propulsion system geometry, engine operating conditions and vehicle flight trajectory were investigated. Analytical support of the plume technology test program was directed at the two latter problem areas: (1) definition of the full-scale exhaust plume characteristics, (2) application of appropriate similarity parameters; and (3) analysis of wind tunnel test data. Verification of the two-phase plume and plume impingement models was directed toward the definition of the full-scale exhaust plume characteristics and the separation motor impingement problem.

  17. Exploring the effects of temperature and grain size on plumes associated with PDCs through analogue experimentation

    NASA Astrophysics Data System (ADS)

    Mitchell, S. J.; Eychenne, J.; Rust, A.

    2015-12-01

    Pyroclastic density currents (PDCs) often loft upwards into convective, buoyant co-PDC plumes. Recent analogue experiments using a unimodal grain size of 22 ± 6 μm (Andrews & Manga, 2012) have established that plume generation is aided by PDC interaction with a topographic barrier. Here, we have simulated the onset of co-PDC plumes from the collapse of concentrated particle-gas mixtures comprised of unimodal or bimodal grain size distributions (GSD) of glass beads, using combinations of lognormal populations with modes of 35, 195 and 590 μm. The collapse of a mixture, with constant mass 2950 ± 150 g, induced the propagation of a gravity current channelized down a 13° sloping tank; a barrier in the tank caused the gravity current to produce a plume of particles. Experiments were recorded with high speed visible and thermal-infrared cameras. Initial GSD and temperature of the mixture were varied to assess the effects of the addition of a coarser component on plume generation. Analogue co-PDC plumes were only produced when a proportion of fine grains (35 μm) was present in the initial granular mixture. Sampling of the particles entrained in the co-PDC plumes revealed that fine grains (35 μm) are preferentially lofted, although a few coarser particles (195 or 590 μm) are also entrained in the co-PDC plumes and settle closer to the area of uplift. Increasing the initial temperature of the mixture increases plume height measured at 1 and 2s after onset; this is supported by repeat experiments at specific conditions. Bimodal mixtures containing both fine (35 μm) and coarser (195 or 590 μm) grains result in plume heights and initial flow velocities higher than observed in unimodal fine-grained experiments of the same total mass of particles. Repeat experiments identify the natural variability in plume generation under the same nominal conditions, which is likely due to the combined variations of momentum during flow propagation and heat-driven buoyancy, as well

  18. Experimental Results of the Impact of an Ion Thruster Plasma on Microwave Propagation

    NASA Technical Reports Server (NTRS)

    Zaman, Afroz J.; Lambert, Kevin M.

    2000-01-01

    Electric thrusters are being considered for a variety of space missions because of the significant propellant savings that result from the use of high performance, electric propulsion technologies. Propellant mass savings reduces spacecraft launch requirements and increases mission lifetime and payload. The impact of electric thruster plasma plumes on microwave signal propagation however is an important spacecraft integration concern. Arcjets were the first electric thrusters to be considered for operational missions. Ling, et al. studied the effect of arcjet plumes on propagation. Arcjets produce a lightly ionized plume and Ling's analysis predicted that the plume would have a negligible effect on communication. Plumes from the higher performance ion thrusters being developed exhibit higher ionization levels, plasma temperatures and particle velocities than arcjets. Therefore, there was a need to assess the impact due to these plumes. To address this need, the authors designed and performed a series of experiments to examine propagation effects of plumes. The challenge with these experiments was that they had to be performed in the operational environment of the thruster. Therefore, the experiments were conducted inside a metal chamber which could be depressurized to simulate a near vacuum condition of space. The metal chamber presents a potential large source of error to the propagation measurements due to the corruption of the desired data by multiple wall reflections within the chamber. This chamber effect was minimized by employing a pulsed-continuous wave transmitter and receiver system. This system based on an HP8510 Network Analyzer, uses external hardware time gating to eliminate the clutter of the spurious reflections. Additionally, high gain antennas were used in the measurements to ensure that minimal amounts of energy were transmitted/received in undesirable directions. The measurements took place in Vacuum Facility 5 of the Electric Propulsion

  19. Experimental Results of the Impact of an Ion Thruster Plasma on Microwave Propagation

    NASA Technical Reports Server (NTRS)

    Zaman, Afroz J.; Lambert, Kevin M.

    2000-01-01

    Electric thrusters are being considered for a variety of space missions because of the significant propellant savings that result from the use of high performance, electric propulsion technologies, Propellant mass savings reduces spacecraft launch requirements and increases mission lifetime and payload. The impact of electric thruster plasma plumes on microwave signal propagation however is an important spacecraft integration concern. Arcjets were the first electric thrusters to be considered for operational missions. Ling, et al., studied the effect of arcjet plumes on propagation. Arcjets produce a lightly ionized plume and Ling's analysis predicted that the plume would have a negligible effect on communication. Plumes from the higher performance ion thrusters being developed exhibit higher ionization levels, plasma temperatures and particle velo@ities than arcjets. Therefore, there was a need to assess the impact due to these plumes. To address this need, the authors designed and performed a series of experiments to examine propagation effects of plumes. The challenge with these experiments was that they had to be performed in the operational environment of the thruster. Therefore, the experiments were conducted inside a metal chamber which could be depressurized to simulate a near vacuum condition of space. The metal chamber presents a potential large source of error to the propagation measurements due to the corruption of the desired data by multiple wall reflections within the chamber. This chamber effect was minimized by employing a pulsed-continuous wave transmitter and receiver system. This system, based on an HP8510 Network Analyzer, uses external hardware time gating to eliminate the clutter of the spurious reflections. Additionally, high gain antennas were used in the measurements to ensure that minimal amounts of energy ",ere transmitted/received in undesirable directions. The measurements took place in Vacuum Facility 5 of the Electric Propulsion

  20. Global Modeling of Uranium Molecular Species Formation Using Laser-Ablated Plasmas

    NASA Astrophysics Data System (ADS)

    Curreli, Davide; Finko, Mikhail; Azer, Magdi; Armstrong, Mike; Crowhurst, Jonathan; Radousky, Harry; Rose, Timothy; Stavrou, Elissaios; Weisz, David; Zaug, Joseph

    2016-10-01

    Uranium is chemically fractionated from other refractory elements in post-detonation nuclear debris but the mechanism is poorly understood. Fractionation alters the chemistry of the nuclear debris so that it no longer reflects the chemistry of the source weapon. The conditions of a condensing fireball can be simulated by a low-temperature plasma formed by vaporizing a uranium sample via laser heating. We have developed a global plasma kinetic model in order to model the chemical evolution of U/UOx species within an ablated plasma plume. The model allows to track the time evolution of the density and energy of an uranium plasma plume moving through an oxygen atmosphere of given fugacity, as well as other relevant quantities such as average electron and gas temperature. Comparison of model predictions with absorption spectroscopy of uranium-ablated plasmas provide preliminary insights on the key chemical species and evolution pathways involved during the fractionation process. This project was sponsored by the DoD, Defense Threat Reduction Agency, Grant HDTRA1-16-1-0020. This work was performed in part under the auspices of the U.S. DoE by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  1. Numerical analysis of laser ablation and damage in glass with multiple picosecond laser pulses.

    PubMed

    Sun, Mingying; Eppelt, Urs; Russ, Simone; Hartmann, Claudia; Siebert, Christof; Zhu, Jianqiang; Schulz, Wolfgang

    2013-04-08

    This study presents a novel numerical model for laser ablation and laser damage in glass including beam propagation and nonlinear absorption of multiple incident ultrashort laser pulses. The laser ablation and damage in the glass cutting process with a picosecond pulsed laser was studied. The numerical results were in good agreement with our experimental observations, thereby revealing the damage mechanism induced by laser ablation. Beam propagation effects such as interference, diffraction and refraction, play a major role in the evolution of the crater structure and the damage region. There are three different damage regions, a thin layer and two different kinds of spikes. Moreover, the electronic damage mechanism was verified and distinguished from heat modification using the experimental results with different pulse spatial overlaps.

  2. The controversy over plumes: Who is actually right?

    NASA Astrophysics Data System (ADS)

    Puchkov, V. N.

    2009-01-01

    The current state of the theory of mantle plumes and its relation to classic plate tectonics show that the “plume” line of geodynamic research is in a period of serious crisis. The number of publications criticizing this concept is steadily increasing. The initial suggestions of plumes’ advocates are disputed, and not without grounds. Questions have been raised as to whether all plumes are derived from the mantle-core interface; whether they all have a wide head and a narrow tail; whether they are always accompanied by uplifting of the Earth’s surface; and whether they can be reliably identified by geochemical signatures, e.g., by the helium-isotope ratio. Rather convincing evidence indicates that plumes cannot be regarded as a strictly fixed reference frame for moving lithospheric plates. More generally, the very existence of plumes has become the subject of debate. Alternative ideas contend that all plumes, or hot spots, are directly related to plate-tectonic mechanisms and appear as a result of shallow tectonic stress, subsequent decompression, and melting of the mantle enriched in basaltic material. Attempts have been made to explain the regular variation in age of volcanoes in ocean ridges by the crack propagation mechanism or by drift of melted segregations of enriched mantle in a nearly horizontal asthenospheric flow. In the author’s opinion, the crisis may be overcome by returning to the beginnings of the plume concept and by providing an adequate specification of plume attributes. Only mantle flows with sources situated below the asthenosphere should be referred to as plumes. These flows are not directly related to such plate-tectonic mechanisms as passive rifting and decompression melting in the upper asthenosphere and are marked by time-progressive volcanic chains; their subasthenospheric roots are detected in seismic tomographic images. Such plumes are mostly located at the margins of superswells, regions of attenuation of seismic waves at the

  3. Atmospheric-pressure plasma jets: Effect of gas flow, active species, and snake-like bullet propagation

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

    Wu, S.; Wang, Z.; Huang, Q.

    2013-02-15

    Cold atmospheric-pressure plasma jets have recently attracted enormous interest owing to numerous applications in plasma biology, health care, medicine, and nanotechnology. A dedicated study of the interaction between the upstream and downstream plasma plumes revealed that the active species (electrons, ions, excited OH, metastable Ar, and nitrogen-related species) generated by the upstream plasma plume enhance the propagation of the downstream plasma plume. At gas flows exceeding 2 l/min, the downstream plasma plume is longer than the upstream plasma plume. Detailed plasma diagnostics and discharge species analysis suggest that this effect is due to the electrons and ions that are generatedmore » by the upstream plasma and flow into the downstream plume. This in turn leads to the relatively higher electron density in the downstream plasma. Moreover, high-speed photography reveals a highly unusual behavior of the plasma bullets, which propagate in snake-like motions, very differently from the previous reports. This behavior is related to the hydrodynamic instability of the gas flow, which results in non-uniform distributions of long-lifetime active species in the discharge tube and of surface charges on the inner surface of the tube.« less

  4. Infrasonic ray tracing applied to small-scale atmospheric structures: thermal plumes and updrafts/downdrafts.

    PubMed

    Jones, R Michael; Bedard, Alfred J

    2015-02-01

    A ray-tracing program is used to estimate the refraction of infrasound by the vertical structure of the atmosphere in thermal plumes, showing only weak effects, as well as in updrafts and downdrafts, which can act as vertical wave guides. Thermal plumes are ubiquitous features of the daytime atmospheric boundary layer. The effects of thermal plumes on lower frequency sound propagation are minor with the exception of major events, such as volcanoes, forest fires, or industrial explosions where quite strong temperature gradients are involved. On the other hand, when strong, organized vertical flows occur (e.g., in mature thunderstorms and microbursts), there are significant effects. For example, a downdraft surrounded by an updraft focuses sound as it travels upward, and defocuses sound as it travels downward. Such propagation asymmetry may help explain observations that balloonists can hear people on the ground; but conversely, people on the ground cannot hear balloonists aloft. These results are pertinent for those making surface measurements from acoustic sources aloft, as well as for measurements of surface sound sources using elevated receivers.

  5. Cross-shore transport of nearshore sediment by river plume frontal pumping

    NASA Astrophysics Data System (ADS)

    Horner-Devine, Alexander R.; Pietrzak, Julie D.; Souza, Alejandro J.; McKeon, Margaret A.; Meirelles, Saulo; Henriquez, Martijn; Flores, Raúl P.; Rijnsburger, Sabine

    2017-06-01

    We present a new mechanism for cross-shore transport of fine sediment from the nearshore to the inner shelf resulting from the onshore propagation of river plume fronts. Onshore frontal propagation is observed in moorings and radar images, which show that fronts penetrate onshore through the nearshore and surf zone, almost to the waterline. During frontal passage a two-layer counterrotating velocity field characteristic of tidal straining is immediately set up, generating a net offshore flow beneath the plume. The seaward flow at depth carries with it high suspended sediment concentrations, which appear to have been generated by wave resuspension in the nearshore region. These observations describe a mechanism by which vertical density stratification can drive exchange of material between the nearshore region and the inner shelf. To our knowledge these are the first observations of this frontal pumping mechanism, which is expected to play an important role in sediment transport near river mouths.

  6. The influence of ns- and fs-LA plume local conditions on the performance of a combined LIBS/LA-ICP-MS sensor

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

    LaHaye, Nicole L.; Phillips, Mark C.; Duffin, Andrew M.

    2016-01-01

    Both laser-induced breakdown spectroscopy (LIBS) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) are well-established analytical techniques with their own unique advantages and disadvantages. The combination of the two analytical methods is a very promising way to overcome the challenges faced by each method individually. We made a comprehensive comparison of local plasma conditions between nanosecond (ns) and femtosecond (fs) laser ablation (LA) sources in a combined LIBS and LA-ICP-MS system. The optical emission spectra and ICP-MS signal were recorded simultaneously for both ns- and fs-LA and figures of merit of the system were analyzed. Characterization of the plasma was conductedmore » by evaluating temperature and density of the plume under various irradiation conditions using optical emission spectroscopy, and correlations to ns- and fs-LIBS and LA-ICP-MS signal were made. The present study is very useful for providing conditions for a multimodal system as well as giving insight into how laser ablation plume parameters are related to LA-ICP-MS and LIBS results for both ns- and fs-LA.« less

  7. Can Plume-Forming Asteroid Airbursts Generate Meteotsunami in Deep Water?

    NASA Astrophysics Data System (ADS)

    Boslough, M.

    2015-12-01

    Hydrocode simulations suggest that the 1908 Tunguska explosion was a plume-forming airburst analogous to those caused by Comet Shoemaker-Levy 9 (SL9) collisions with Jupiter in 1994. A noctilucent cloud that appeared over Europe following the Tunguska event is similar to post-impact features on Jupiter, consistent with a collapsed plume containing condensation from the vaporized asteroid. Previous workers treated Tunguska as a point explosion and used seismic records, barograms, and extent of fallen trees to determine explosive yield. Estimates were based on scaling laws derived from nuclear weapons data, neglecting directionality, mass, and momentum of the asteroid. This point-source assumption, with other simplifications, led to a significant overestimate. Tunguska seismic data were consistent with ground motion from a vertical point impulse of 7×1018dyn sec caused by the downward blast wave of a 12.5-megaton nuclear explosion at an altitude of 8.5 km for an effective momentum multiplication factor (β) of ~80. However, simulations of a 3-megaton collisional airburst reveal that the upward-directed momentum contained in a ballistic plume can reach this level within the first minute after the explosion (β≈300). The reaction impulse from such an airburst is therefore similar to a much larger non-plume-forming nuclear explosion. Momentum is coupled through the atmosphere to the surface, generating disproportionately large seismic signatures. This result suggests that coupling from an over-water plume-forming airburst could be a more efficient tsunami source mechanism than a collapsing impact cavity or direct air blast because the characteristic time of the plume is closer to that of a long-period wave in deep water. As the plume accelerates upward, it creates a slowly-rising and sustained overpressure with a ramp wave that propagates outward at the speed of sound, generating a tsunami in deep ocean by the same mechanism that yields slower meteotsunami in shallow

  8. Experimental Investigation of Molecular Species Formation in Metal Plasmas During Laser Ablation

    NASA Astrophysics Data System (ADS)

    Radousky, H.; Crowhurst, J.; Rose, T.; Armstrong, M.; Stavrou, E.; Zaug, J.; Weisz, D.; Azer, M.; Finko, M.; Curreli, D.

    2016-10-01

    Atomic and molecular spectra on metal plasmas generated by laser ablation have been measured using single, nominally 6-7 ns pulses at 1064 nm, and with energies less than 50 mJ. The primary goal for these studies is to constrain the physical and chemical mechanisms that control the distribution of radionuclides in fallout after a nuclear detonation. In this work, laser emission spectroscopy was used to obtain in situdata for vapor phase molecular species as they form in a controlled oxygen atmosphere for a variety of metals such as Fe, Al, as well as preliminary results for U. In particular, the ablation plumes created from these metals have been imaged with a resolution of 10 ns, and it is possible to observe the expansion of the plume out to 0.5 us. These data serve as one set of inputs for a semi-empirical model to describe the chemical fractionation of uranium during fallout formation. Prepared by LLNL under Contract DE-AC52-07NA27344. This project was sponsored by the Department of the Defense, Defense Threat Reduction Agency, under Grant Number HDTRA1-16-1-0020.

  9. Correlation of plume dynamics and oxygen pressure with VO2 stoichiometry during pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Lafane, S.; Kerdja, T.; Abdelli-Messaci, S.; Khereddine, Y.; Kechouane, M.; Nemraoui, O.

    2013-07-01

    Vanadium dioxide thin films have been deposited on Corning glass substrates by a KrF laser ablation of V2O5 target at the laser fluence of 2 J cm-2. The substrate temperature and the target-substrate distance were set to 500 ∘C and 4 cm, respectively. X-ray diffraction analysis showed that pure VO2 is only obtained at an oxygen pressure range of 4×10-3-2×10-2 mbar. A higher optical switching contrast was obtained for the VO2 films deposited at 4×10-3-10-2 mbar. The films properties were correlated to the plume-oxygen gas interaction monitored by fast imaging of the plume.

  10. Laser ablation and deposition of wide bandgap semiconductors: plasma and nanostructure of deposits diagnosis

    NASA Astrophysics Data System (ADS)

    Sanz, M.; López-Arias, M.; Rebollar, E.; de Nalda, R.; Castillejo, M.

    2011-12-01

    Nanostructured CdS and ZnS films on Si (100) substrates were obtained by nanosecond pulsed laser deposition at the wavelengths of 266 and 532 nm. The effect of laser irradiation wavelength on the surface structure and crystallinity of deposits was characterized, together with the composition, expansion dynamics and thermodynamic parameters of the ablation plume. Deposits were analyzed by environmental scanning electron microscopy, atomic force microscopy and X-ray diffraction, while in situ monitoring of the plume was carried out with spectral, temporal and spatial resolution by optical emission spectroscopy. The deposits consist of 25-50 nm nanoparticle assembled films but ablation in the visible results in larger aggregates (150 nm) over imposed on the film surface. The aggregate free films grown at 266 nm on heated substrates are thicker than those grown at room temperature and in the former case they reveal a crystalline structure congruent with that of the initial target material. The observed trends are discussed in reference to the light absorption step, the plasma composition and the nucleation processes occurring on the substrate.

  11. Modeling of Laser Vaporization and Plume Chemistry in a Boron Nitride Nanotube Production Rig

    NASA Technical Reports Server (NTRS)

    Gnoffo, Peter A.; Fay, Catharine C.

    2012-01-01

    Flow in a pressurized, vapor condensation (PVC) boron nitride nanotube (BNNT) production rig is modeled. A laser provides a thermal energy source to the tip of a boron ber bundle in a high pressure nitrogen chamber causing a plume of boron-rich gas to rise. The buoyancy driven flow is modeled as a mixture of thermally perfect gases (B, B2, N, N2, BN) in either thermochemical equilibrium or chemical nonequilibrium assuming steady-state melt and vaporization from a 1 mm radius spot at the axis of an axisymmetric chamber. The simulation is intended to define the macroscopic thermochemical environment from which boron-rich species, including nanotubes, condense out of the plume. Simulations indicate a high temperature environment (T > 4400K) for elevated pressures within 1 mm of the surface sufficient to dissociate molecular nitrogen and form BN at the base of the plume. Modifications to Program LAURA, a finite-volume based solver for hypersonic flows including coupled radiation and ablation, are described to enable this simulation. Simulations indicate that high pressure synthesis conditions enable formation of BN vapor in the plume that may serve to enhance formation of exceptionally long nanotubes in the PVC process.

  12. Propagating intensity disturbances in polar corona as seen from AIA/SDO

    NASA Astrophysics Data System (ADS)

    Krishna Prasad, S.; Banerjee, D.; Gupta, G. R.

    2011-04-01

    Context. Polar corona is often explored to find the energy source for the acceleration of the fast solar wind. Earlier observations show omni-presence of quasi-periodic disturbances, traveling outward, which is believed to be caused by the ubiquitous presence of outward propagating waves. These waves, mostly of compressional type, might provide the additional momentum and heat required for the fast solar wind acceleration. It has been conjectured that these disturbances are not due to waves but high speed plasma outflows, which are difficult to distinguish using the current available techniques. Aims: With the unprecedented high spatial and temporal resolution of AIA/SDO, we search for these quasi-periodic disturbances in both plume and interplume regions of the polar corona. We investigate their nature of propagation and search for a plausible interpretation. We also aim to study their multi-thermal nature by using three different coronal passbands of AIA. Methods: We chose several clean plume and interplume structures and studied the time evolution of specific channels by making artificial slits along them. Taking the average across the slits, space-time maps are constructed and then filtration techniques are applied to amplify the low-amplitude oscillations. To suppress the effect of fainter jets, we chose wider slits than usual. Results: In almost all the locations chosen, in both plume and interplume regions we find the presence of propagating quasi-periodic disturbances, of periodicities ranging from 10-30 min. These are clearly seen in two channels and in a few cases out to very large distances (≈250″) off-limb, almost to the edge of the AIA field of view. The propagation speeds are in the range of 100-170 km s-1. The average speeds are different for different passbands and higher in interplume regions. Conclusions: Propagating disturbances are observed, even after removing the effects of jets and are insensitive to changes in slit width. This indicates

  13. Measurement of magnetic field fluctuations and diamagnetic currents within a laser ablation plasma interacting with an axial magnetic field

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

    Ikeda, S.; Horioka, K.; Okamura, M.

    Here, the guiding of laser ablation plasmas with axial magnetic fields has been used for many applications, since its effectiveness has been proven empirically. For more sophisticated and complicated manipulations of the plasma flow, the behavior of the magnetic field during the interaction and the induced diamagnetic current in the plasma plume needs to be clearly understood. To achieve the first milestone for establishing magnetic plasma manipulation, we measured the spatial and temporal fluctuations of the magnetic field caused by the diamagnetic current. We showed that the small fluctuations of the magnetic field can be detected by using a simplemore » magnetic probe. We observed that the field penetrates to the core of the plasma plume. The diamagnetic current estimated from the magnetic field had temporal and spatial distributions which were confirmed to be correlated with the transformation of the plasma plume. Our results show that the measurement by the magnetic probe is an effective method to observe the temporal and spatial distributions of the magnetic field and diamagnetic current. The systematic measurement of the magnetic field variations is a valuable method to establish the magnetic field manipulation of the laser ablation plasma.« less

  14. Measurement of magnetic field fluctuations and diamagnetic currents within a laser ablation plasma interacting with an axial magnetic field

    DOE PAGES

    Ikeda, S.; Horioka, K.; Okamura, M.

    2017-10-10

    Here, the guiding of laser ablation plasmas with axial magnetic fields has been used for many applications, since its effectiveness has been proven empirically. For more sophisticated and complicated manipulations of the plasma flow, the behavior of the magnetic field during the interaction and the induced diamagnetic current in the plasma plume needs to be clearly understood. To achieve the first milestone for establishing magnetic plasma manipulation, we measured the spatial and temporal fluctuations of the magnetic field caused by the diamagnetic current. We showed that the small fluctuations of the magnetic field can be detected by using a simplemore » magnetic probe. We observed that the field penetrates to the core of the plasma plume. The diamagnetic current estimated from the magnetic field had temporal and spatial distributions which were confirmed to be correlated with the transformation of the plasma plume. Our results show that the measurement by the magnetic probe is an effective method to observe the temporal and spatial distributions of the magnetic field and diamagnetic current. The systematic measurement of the magnetic field variations is a valuable method to establish the magnetic field manipulation of the laser ablation plasma.« less

  15. Characteristic properties of laser ablation of translucent targets

    NASA Astrophysics Data System (ADS)

    Platonov, V. V.; Kochurin, E. A.; Osipov, V. V.; Lisenkov, V. V.; Zubarev, N. M.

    2018-07-01

    This study reveals the characteristic features of the laser ablation of the solid Nd:Y2O3 targets, such as the dynamics of the laser plume, the crater depth, and the weight and size distribution of liquid melt droplets. The ablation was initiated by the ytterbium fiber laser radiation pulses with constant energy (0.67 J) and with different power densities. The dependence on the power density of such parameters as the injection time of drops, mass distribution of drops, crater depth, and productivity of synthesis of nonopowder was revealed. To explain the formation of deep craters a model was proposed, stating that the formation of liquid droplets is a consequence of the Kelvin–Helmholtz instability’s appearing and developing on the border between the liquid melt on the crater’s wall and the vapor flow from the crater. The increment of this instability and its characteristic size was determined.

  16. Infrared thermography and thermocouple mapping of radiofrequency renal ablation to assess treatment adequacy and ablation margins.

    PubMed

    Ogan, Kenneth; Roberts, William W; Wilhelm, David M; Bonnell, Leonard; Leiner, Dennis; Lindberg, Guy; Kavoussi, Louis R; Cadeddu, Jeffrey A

    2003-07-01

    The primary disadvantage of renal tumor RF ablation is the inability to monitor the intraoperative propagation of the RF lesion with real-time imaging. We sought to assess whether adequately lethal temperatures are obtained at the margins of the intended ablation zone using laparoscopic thermography to monitor radiofrequency (RF) lesions in real time, thermocouple measurements, and histopathologic evaluation. Renal RF lesions were created under direct laparoscopic vision in the upper (1 cm diameter) and lower (2 cm) poles of the right kidney in 5 female pigs. The RF lesions were produced with the RITA generator and probe, set at 105 degrees C for 5-minute ablations. During RF treatment, a laparoscopic infrared (IR) camera measured the surface parenchymal temperatures, as did multiple thermocouples. The pigs were then either immediately killed (n = 3) or allowed to live for 2 weeks (n = 2). The kidneys were removed to correlate the temperature measurements with histologic analysis of the ablated lesion. Using a threshold temperature of greater than 70 degrees C for visual "temperature" color change, the IR camera identified the region of pathologic necrosis of the renal parenchyma during RF ablation. Thermocouple measurements demonstrated that the temperatures at the intended ablation radius reached 77.5 degrees C at the renal surface and 83.7 degrees C centrally, and temperatures 5 mm beyond the set radius reached 52.6 degrees C at the surface and 47.7 degrees C centrally. The average diameter of the gross lesion on the surface of the kidney measured 17.1 mm and 22.4 mm for 1-cm and 2-cm ablations, respectively. These surface measurements correlated with an average diameter of 16.1 mm and 15.9 mm (1-cm and 2-cm ablations, respectively) as measured with the IR camera. All cells within these ablation zones were nonviable by nicotinamide adenine dinucleotide diaphorase analysis. The average depth of the lesions measured 19 mm (1-cm ablation) and 25 mm (2-cm ablation

  17. Spectroscopic measurements of plasma plume induced during the laser deposition of the hydroxyapatite

    NASA Astrophysics Data System (ADS)

    Jedyński, M.; Szymański, Z.; Mróz, W.; Prokopiuk, A.; Jelinek, M.; Kocourek, T.

    2004-03-01

    Plasma plume induced by ArF exeimer laser ablation of a Ca10(PO4)6(OH)2 hydroxyapatite target during deposition process has been studied in different ambient conditions, i.e. in air or water vapour. ArF laser operated at the wavelength of 193 nm with the pulse energy of 300 mJ and 20 ns pulse duration. Spectroscopic measurements of the emission spectra of plasma plume have been made with the use of a fast gate, lens coupled micro-channel plate (MCP) image intensifier placed between a spectrograph and a 1254 silicon intensified target (SIT) detector connected to an optical multichannel analyser. The electron densities of 1022 ÷ 1023m-3 have been determined from the Stark broadening of Ca I lines as a function of the distance from the target. The expansion of the plasma plume has been studied using the time of flight method. The time-dependent radiation of the 422.673 nm Ca I and 393.366 nm Ca II lines has been, registered with the use of a monochromator and photomultiplier at various distances from the target. Velocities between 104 ÷ 103 m/s have been found. The velocity in air is several times higher than in the case with water vapour. The plasma plume dynamics is also different in both cases. In the presence of water vapour the spliting of the plasma plume appears.

  18. Asymmetric sea-floor spreading caused by ridge-plume interactions

    NASA Astrophysics Data System (ADS)

    Müller, R. Dietmar; Roest, Walter R.; Royer, Jean-Yves

    1998-12-01

    Crustal accretion at mid-ocean ridges is generally modelled as a symmetric process. Regional analyses, however, often show either small-scale asymmetries, which vary rapidly between individual spreading corridors, or large-scale asymmetries represented by consistent excess accretion on one of the two separating plates over geological time spans. In neither case is the origin of the asymmetry well understood. Here we present a comprehensive analysis of the asymmetry of crustal accretion over the past 83Myr based on a set of self-consistent digital isochrons and models of absolute plate motion,. We find that deficits in crustal accretion occur mainly on ridge flanks overlying one or several hotspots. We therefore propose that asymmetric accretion is caused by ridge propagation towards mantle plumes or minor ridge jumps sustained by asthenospheric flow, between ridges and plumes. Quantifying the asymmetry of crustal accretion provides a complementary approach to that based on geochemical and other geophysical data, in helping to unravel how mantle plumes and mid-ocean ridges are linked through mantle convection processes.

  19. A linear-field plasma jet for generating a brush-shaped laminar plume at atmospheric pressure

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

    Li, Xuechen; Jia, Pengying, E-mail: plasmalab@126.com; Key Laboratory of Photo-Electronics Information Materials of Hebei Province, Baoding 071002

    2016-06-15

    A linear-field plasma jet composed of line-to-plate electrodes is used to generate a large-scale brush-shaped plasma plume with flowing argon used as working gas. Through electrical measurement and fast photography, it is found that the plasma plume bridges the two electrodes for the discharge in the positive voltage half-cycle, which behaves like fast moving plasma bullets directed from the anode to the cathode. Compared with the positive discharge, the negative discharge only develops inside the nozzle and propagates much slower. Results also indicate that the gas temperature of the plume is close to room temperature, which is promising for biomedicalmore » application.« less

  20. Signatures of Nonlinear Waves in Coronal Plumes and Holes

    NASA Technical Reports Server (NTRS)

    Ofman, Leon

    1999-01-01

    In recent Ultraviolet Coronagraph Spectrometer/Solar and Heliospheric Observatory (UVCS/SOHO) White Light Channel (WLC) observations we found quasi-periodic variations in the polarized brightness (pB) in the polar coronal holes at heliocentric distances of 1.9-2.45 solar radii. The motivation for the observation is the 2.5D Magnetohydrodynamics (MHD) model of solar wind acceleration by nonlinear waves, that predicts compressive fluctuations in coronal holes. To help identify the waves observed with the UVCS/WLC we model the propagation and dissipation of slow magnetosonic waves in polar plumes using 1D MHD code in spherical geometry, We find that the slow waves nonlinearly steepen in the gravitationally stratified plumes. The nonlinear steepening of the waves leads to enhanced dissipation due to compressive viscosity at the wave-fronts.

  1. A uniform laminar air plasma plume with large volume excited by an alternating current voltage

    NASA Astrophysics Data System (ADS)

    Li, Xuechen; Bao, Wenting; Chu, Jingdi; Zhang, Panpan; Jia, Pengying

    2015-12-01

    Using a plasma jet composed of two needle electrodes, a laminar plasma plume with large volume is generated in air through an alternating current voltage excitation. Based on high-speed photography, a train of filaments is observed to propagate periodically away from their birth place along the gas flow. The laminar plume is in fact a temporal superposition of the arched filament train. The filament consists of a negative glow near the real time cathode, a positive column near the real time anode, and a Faraday dark space between them. It has been found that the propagation velocity of the filament increases with increasing the gas flow rate. Furthermore, the filament lifetime tends to follow a normal distribution (Gaussian distribution). The most probable lifetime decreases with increasing the gas flow rate or decreasing the averaged peak voltage. Results also indicate that the real time peak current decreases and the real time peak voltage increases with the propagation of the filament along the gas flow. The voltage-current curve indicates that, in every discharge cycle, the filament evolves from a Townsend discharge to a glow one and then the discharge quenches. Characteristic regions including a negative glow, a Faraday dark space, and a positive column can be discerned from the discharge filament. Furthermore, the plasma parameters such as the electron density, the vibrational temperature and the gas temperature are investigated based on the optical spectrum emitted from the laminar plume.

  2. Propagation of ion acoustic wave energy in the plume of a high-current LaB6 hollow cathode

    NASA Astrophysics Data System (ADS)

    Jorns, Benjamin A.; Dodson, Christoper; Goebel, Dan M.; Wirz, Richard

    2017-08-01

    A frequency-averaged quasilinear model is derived and experimentally validated for the evolution of ion acoustic turbulence (IAT) along the centerline of a 100-A class, LaB6 hollow cathode. Probe-based diagnostics and a laser induced fluorescence system are employed to measure the properties of both the turbulence and the background plasma parameters as they vary spatially in the cathode plume. It is shown that for the three discharge currents investigated, 100 A, 130 A, and 160 A, the spatial growth of the total energy density of the IAT in the near field of the cathode plume is exponential and agrees quantitatively with the predicted growth rates from the quasilinear formulation. However, in the downstream region of the cathode plume, the growth of IAT energy saturates at a level that is commensurate with the Sagdeev limit. The experimental validation of the quasilinear model for IAT growth and its limitations are discussed in the context of numerical efforts to describe self-consistently the plasma processes in the hollow cathode plume.

  3. Isopycnal deepening of an under-ice river plume in coastal waters: Field observations and modeling

    NASA Astrophysics Data System (ADS)

    Li, S. Samuel; Ingram, R. Grant

    2007-07-01

    The Great Whale River, located on the southeast coast of Hudson Bay in Canada, forms a large river plume under complete landfast ice during early spring. Short-term fluctuations of plume depth have motivated the present numerical study of an under-ice river plume subject to tidal motion and friction. We introduce a simple two-layer model for predicting the vertical penetration of the under-ice river plume as it propagates over a deepening topography. The topography is idealized but representative. Friction on the bottom surface of the ice cover, on the seabed, and at the plume interface is parameterized using the quadratic friction law. The extent of the vertical penetration is controlled by dimensionless parameters related to tidal motion and river outflow. Model predictions are shown to compare favorably with under-ice plume measurements from the river mouth. This study illustrates that isopycnal deepening occurs when the ice-cover vertical motion creates a reduced flow cross-section during the ebbing tide. This results in supercritical flow and triggers the downward plume penetration in the offshore. For a given river discharge, the freshwater source over a tidal cycle is unsteady in terms of discharge velocity because of the variation in the effective cross-sectional area at the river mouth, through which freshwater flows.

  4. Experimental studies of the effect target geometry on the evolution of laser produced plasma plumes

    NASA Astrophysics Data System (ADS)

    Beatty, Cuyler; Anderson, Austin; Iratcabal, Jeremy; Dutra, Eric; Covington, Aaron

    2016-10-01

    The expansion of the laser plumes was shown to be dependent on the initial target geometry. A 16 channel framing camera was used to record the plume shape and propagation speeds were determined from analysis of the images. Plastic targets were manufactured using different methods including 3D printing, CNC machining and vacuum casting. Preliminary target designs were made using a 3D printer and ABS plastic material. These targets were then tested using a 3 J laser with a 5 ns duration pulse. Targets with a deep conical depression were shown to produce highly collimated plumes when compared to flat top targets. Preliminary results of these experiments will be discussed along with planned future experiments that will use the indented targets with a 30 J laser with a 0.8 ns duration pulse in preparation for pinched laser plume experiments at the Nevada Terawatt Facility. Other polymers that are readily available in a deuterated form will also be explored as part of an effort to develop a cost effective plasma plume target for follow on neutron production experiments. Dr. Austin Anderson.

  5. Toxic Alexandrium blooms in the western Gulf of Maine: The plume advection hypothesis revisited

    USGS Publications Warehouse

    Anderson, D.M.; Keafer, B.A.; Geyer, W.R.; Signell, R.P.; Loder, T.C.

    2005-01-01

    The plume advection hypothesis links blooms of the toxic dinoflagellate Alexandrium fundyense in the western Gulf of Maine (GOM) to a buoyant plume derived from river outflows. This hypothesis was examined with cruise and moored-instrument observations in 1993 when levels of paralytic shellfish poisoning (PSP) toxins were high, and in 1994 when toxicity was low. A coupled physical-biological model simulated hydrography and A. fundyense distributions. Initial A. fundyense populations were restricted to low-salinity nearshore waters near Casco Bay, but also occurred in higher salinity waters along the plume boundary. This suggests two sources of cells - those from shallow-water cyst populations and those transported to shore from offshore blooms in the eastern segment of the Maine coastal current (EMCC). Observations confirm the role of the plume in A. fundyense transport and growth. Downwelling-favorable winds in 1993 transported the plume and its cells rapidly alongshore, enhancing toxicity and propagating PSP to the south. In 1994, sustained upwelling moved the plume offshore, resulting in low toxicity in intertidal shellfish. A. fundyense blooms were likely nutrient limited, leading to low growth rates and moderate cell abundances. These observations and mechanisms were reproduced by coupled physical-biological model simulations. The plume advection hypothesis provides a viable explanation for outbreaks of PSP in the western GOM, but should be refined to include two sources for cells that populate the plume and two major pathways for transport: one within the low-salinity plume and another where A. fundyense cells originating in the EMCC are transported along the outer boundary of the plume front with the western segment of the Maine coastal current.

  6. Computational models for the analysis of three-dimensional internal and exhaust plume flowfields

    NASA Technical Reports Server (NTRS)

    Dash, S. M.; Delguidice, P. D.

    1977-01-01

    This paper describes computational procedures developed for the analysis of three-dimensional supersonic ducted flows and multinozzle exhaust plume flowfields. The models/codes embodying these procedures cater to a broad spectrum of geometric situations via the use of multiple reference plane grid networks in several coordinate systems. Shock capturing techniques are employed to trace the propagation and interaction of multiple shock surfaces while the plume interface, separating the exhaust and external flows, and the plume external shock are discretely analyzed. The computational grid within the reference planes follows the trace of streamlines to facilitate the incorporation of finite-rate chemistry and viscous computational capabilities. Exhaust gas properties consist of combustion products in chemical equilibrium. The computational accuracy of the models/codes is assessed via comparisons with exact solutions, results of other codes and experimental data. Results are presented for the flows in two-dimensional convergent and divergent ducts, expansive and compressive corner flows, flow in a rectangular nozzle and the plume flowfields for exhausts issuing out of single and multiple rectangular nozzles.

  7. DYNAMICS OF ON-DISK PLUMES AS OBSERVED WITH THE INTERFACE REGION IMAGING SPECTROGRAPH, THE ATMOSPHERIC IMAGING ASSEMBLY, AND THE HELIOSEISMIC AND MAGNETIC IMAGER

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

    Pant, Vaibhav; Mazumder, Rakesh; Banerjee, Dipankar

    2015-07-01

    We examine the role of small-scale transients in the formation and evolution of solar coronal plumes. We study the dynamics of plume footpoints seen in the vicinity of a coronal hole using the Atmospheric Imaging Assembly (AIA) images, the Helioseismic and Magnetic Imager magnetogram on board the Solar Dynamics Observatory and spectroscopic data from the Interface Region Imaging Spectrograph (IRIS). Quasi-periodic brightenings are observed in the base of the plumes and are associated with magnetic flux changes. With the high spectral and spatial resolution of IRIS, we identify the sources of these oscillations and try to understand what role themore » transients at the footpoints can play in sustaining the coronal plumes. IRIS “sit-and-stare” observations provide a unique opportunity to study the evolution of footpoints of the plumes. We notice enhanced line width and intensity, and large deviation from the average Doppler shift in the line profiles at specific instances, which indicate the presence of flows at the footpoints of plumes. We propose that outflows (jet-like features) as a result of small-scale reconnections affect the line profiles. These jet-like features may also be responsible for the generation of propagating disturbances (PDs) within the plumes, which are observed to be propagating to larger distances as recorded from multiple AIA channels. These PDs can be explained in terms of slow magnetoacoustic waves.« less

  8. Influence of the shielding effect on the formation of a micro-texture on the cermet with nanosecond pulsed laser ablation.

    PubMed

    Yuan, Jiandong; Liang, Liang; Jiang, Lelun; Liu, Xin

    2018-04-01

    The degree of laser pulse overlapping in a laser scanning path has a significant impact on the ablation regime in the laser machining of a micro-texture. In this Letter, a nanosecond pulsed laser is used to prepare the micro-scaled groove on WC-8Co cermet under different scanning speeds. It is observed that as the scanning speed increases, the ablated trace morphology in the first scanning pass transits from a succession of intermittent deep dimples to the consecutive overlapped shallow pits. The test result also indicates that ablated trace morphology with respect to the low scanning speed stems from a plume shielding effect. Moreover, the ablation regime considering the shielding effect in micro-groove formation process is clarified. The critical scanning speed that can circumvent the shielding effect is also summarized with respect to different laser powers.

  9. Time-resolved investigations of the non-thermal ablation process of graphite induced by femtosecond laser pulses

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

    Kalupka, C., E-mail: christian.kalupka@llt.rwth-aachen.de; Finger, J.; Reininghaus, M.

    2016-04-21

    We report on the in-situ analysis of the ablation dynamics of the, so-called, laser induced non-thermal ablation process of graphite. A highly oriented pyrolytic graphite is excited by femtosecond laser pulses with fluences below the classic thermal ablation threshold. The ablation dynamics are investigated by axial pump-probe reflection measurements, transversal pump-probe shadowgraphy, and time-resolved transversal emission photography. The combination of the applied analysis methods allows for a continuous and detailed time-resolved observation of the non-thermal ablation dynamics from several picoseconds up to 180 ns. Formation of large, μm-sized particles takes place within the first 3.5 ns after irradiation. The following propagation ofmore » ablation products and the shock wave front are tracked by transversal shadowgraphy up to 16 ns. The comparison of ablation dynamics of different fluences by emission photography reveals thermal ablation products even for non-thermal fluences.« less

  10. Photoactive dye-enhanced tissue ablation for endoscopic laser prostatectomy.

    PubMed

    Ahn, Minwoo; Hau, Nguyen Trung; Van Phuc, Nguyen; Oh, Junghwan; Kang, Hyun Wook

    2014-11-01

    Laser light has been widely used as a surgical tool to treat benign prostate hyperplasia (BPH) over 20 years. Recently, application of high laser power up to 200 W was often reported to swiftly remove a large amount of prostatic tissue. The purpose of this study was to validate the feasibility of photoactive dye injection to enhance light absorption and eventually to facilitate tissue vaporization with low laser power. Chicken breast tissue was selected as a target tissue due to minimal optical absorption at the visible wavelength. Four biocompatible photoactive dyes, including amaranth (AR), black dye (BD), hemoglobin powder (HP), and endoscopic marker (EM), were selected and tested in vitro with a customized 532 nm laser system with radiant exposure ranging from 0.9 to 3.9 J/cm(2) . Light absorbance and ablation threshold were measured with UV-Vis spectrometer and Probit analysis, respectively, and compared to feature the function of the injected dyes. Ablation performance with dye-injection was evaluated in light of radiant exposure, dye concentration, and number of injection. Higher light absorption by injected dyes led to lower ablation threshold as well as more efficient tissue removal in the order of AR, BD, HP, and EM. Regardless of the injected dyes, ablation efficiency principally increased with radiant exposure, dye concentration, and number of injection. Among the dyes, AR created the highest ablation rate of 44.2 ± 0.2 µm/pulse due to higher absorbance and lower ablation threshold. High aspect ratios up to 7.1 ± 0.4 entailed saturation behavior in the tissue ablation injected with AR and BD, possibly resulting from plume shielding and increased scattering due to coagulation. Preliminary tests on canine prostate with a hydraulic injection system demonstrated that 80 W with dye injection yielded comparable ablation efficiency to 120 W with no injection, indicating 33% reduced laser power with almost equivalent performance. Due to

  11. Involvement of small carbon clusters in the enhancement of high-order harmonic generation of ultrashort pulses in the plasmas produced during ablation of carbon-contained nanoparticles

    NASA Astrophysics Data System (ADS)

    Ganeev, R. A.

    2017-09-01

    Various carbon-based nanoparticles ablated at the conditions suitable for efficient harmonic generation during propagation of ultrashort pulses through the laser-produced plasmas were studied. The transmission electron microscopy of ablated debris and the time-of-flight mass-spectroscopy studies of plasmas are presented. The conditions of laser ablation of the carbon-contained nanoparticles (fullerenes, graphene, carbon nanotubes, carbon nanofibers, and diamond nanoparticles) were varied to define the impeding processes restricting the harmonic yield from such laser-produced plasmas. These studies show that the enhancement of harmonics during ablation of nanoparticle targets was related with the appearance of small carbon clusters at the moment of propagation of the ultrashort laser pulses though such plasmas.

  12. Spectroscopic studies of the exhaust plume of a quasi-steady MPD accelerator. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Bruckner, A. P.

    1972-01-01

    Spectroscopic and photographic investigations are reported that reveal a complex azimuthal species structure in the exhaust plume of a quasi-steady argon MPD accelerator. Over a wide range of operating conditions the injected argon remains collimated in discrete jets which are azimuthally in line with the six propellant injector orifices. The regions between these argon jets, including the central core of the exhaust flow, are occupied by impurities such as carbon, hydrogen and oxygen ablated from the Plexiglas back plate of the arc chamber. The features of this plume structure are found to be dependent on the arc current and mass flow rate. It is found that nearly half the observed velocity is attained in an acceleration region well downstream of the region of significant electromagnetic interaction. Recombination calculations show that the ionization energy is essentially frozen.

  13. Low-buoyancy thermochemical plumes resolve controversy of classical mantle plume concept

    PubMed Central

    Dannberg, Juliane; Sobolev, Stephan V.

    2015-01-01

    The Earth's biggest magmatic events are believed to originate from massive melting when hot mantle plumes rising from the lowermost mantle reach the base of the lithosphere. Classical models predict large plume heads that cause kilometre-scale surface uplift, and narrow (100 km radius) plume tails that remain in the mantle after the plume head spreads below the lithosphere. However, in many cases, such uplifts and narrow plume tails are not observed. Here using numerical models, we show that the issue can be resolved if major mantle plumes contain up to 15–20% of recycled oceanic crust in a form of dense eclogite, which drastically decreases their buoyancy and makes it depth dependent. We demonstrate that, despite their low buoyancy, large enough thermochemical plumes can rise through the whole mantle causing only negligible surface uplift. Their tails are bulky (>200 km radius) and remain in the upper mantle for 100 millions of years. PMID:25907970

  14. Low-buoyancy thermochemical plumes resolve controversy of classical mantle plume concept

    NASA Astrophysics Data System (ADS)

    Dannberg, Juliane; Sobolev, Stephan V.

    2015-04-01

    The Earth's biggest magmatic events are believed to originate from massive melting when hot mantle plumes rising from the lowermost mantle reach the base of the lithosphere. Classical models predict large plume heads that cause kilometre-scale surface uplift, and narrow (100 km radius) plume tails that remain in the mantle after the plume head spreads below the lithosphere. However, in many cases, such uplifts and narrow plume tails are not observed. Here using numerical models, we show that the issue can be resolved if major mantle plumes contain up to 15-20% of recycled oceanic crust in a form of dense eclogite, which drastically decreases their buoyancy and makes it depth dependent. We demonstrate that, despite their low buoyancy, large enough thermochemical plumes can rise through the whole mantle causing only negligible surface uplift. Their tails are bulky (>200 km radius) and remain in the upper mantle for 100 millions of years.

  15. Influence of electric field on the behavior of Si nanoparticles generated by laser ablation

    NASA Astrophysics Data System (ADS)

    Muramoto, Junichi; Sakamoto, Ippei; Nakata, Yoshiki; Okada, Tatsuo; Maeda, Mitsuo

    1999-08-01

    The influence of an electric field on particle behavior was investigated to control the transport of Si nanoparticles in a laser ablation plume by an ultraviolet Rayleigh scattering (UV-RS) technique. The majority of the nanoparticles, which could be observed by the UV-RS technique, were transported to the negatively biased electrode, indicating that they were positively charged. The deposition efficiency of nanoparticles onto a substrate was also improved by applying an electric field.

  16. Moth-inspired navigation algorithm in a turbulent odor plume from a pulsating source.

    PubMed

    Liberzon, Alexander; Harrington, Kyra; Daniel, Nimrod; Gurka, Roi; Harari, Ally; Zilman, Gregory

    2018-01-01

    Some female moths attract male moths by emitting series of pulses of pheromone filaments propagating downwind. The turbulent nature of the wind creates a complex flow environment, and causes the filaments to propagate in the form of patches with varying concentration distributions. Inspired by moth navigation capabilities, we propose a navigation strategy that enables a flier to locate an upwind pulsating odor source in a windy environment using a single threshold-based detection sensor. This optomotor anemotaxis strategy is constructed based on the physical properties of the turbulent flow carrying discrete puffs of odor and does not involve learning, memory, complex decision making or statistical methods. We suggest that in turbulent plumes from a pulsating point source, an instantaneously measurable quantity referred as a "puff crossing time", improves the success rate as compared to the navigation strategies based on temporally regular zigzags due to intermittent contact, or an "internal counter", that do not use this information. Using computer simulations of fliers navigating in turbulent plumes of the pulsating point source for varying flow parameters such as turbulent intensities, plume meandering and wind gusts, we obtained statistics of navigation paths towards the pheromone sources. We quantified the probability of a successful navigation as well as the flight parameters such as the time spent searching and the total flight time, with respect to different turbulent intensities, meandering or gusts. The concepts learned using this model may help to design odor-based navigation of miniature airborne autonomous vehicles.

  17. The modeling and synthesis of nanodiamonds by laser ablation of graphite and diamond-like carbon in liquid-confined ambient

    NASA Astrophysics Data System (ADS)

    Basso, L.; Gorrini, F.; Bazzanella, N.; Cazzanelli, M.; Dorigoni, C.; Bifone, A.; Miotello, A.

    2018-01-01

    Nanodiamonds have attracted considerable interest for their potential applications in quantum computation, sensing, and bioimaging. However, synthesis of nanodiamonds typically requires high pressures and temperatures, and is still a challenge. Here, we demonstrate production of nanodiamonds by pulsed laser ablation of graphite and diamond-like carbon in water. Importantly, this technique enables production of nanocrystalline diamonds at room temperature and standard pressure conditions. Moreover, we propose a method for the purification of nanodiamonds from graphitic and amorphous carbon phases that do not require strong acids and harsh chemical conditions. Finally, we present a thermodynamic model that describes the formation of nanodiamonds during pulsed laser ablation. We show that synthesis of the crystalline phase is driven by a graphite-liquid-diamond transition process that occurs at the extreme thermodynamic conditions reached inside the ablation plume.

  18. Is surgical plume developing during routine LEEPs contaminated with high-risk HPV? A pilot series of experiments.

    PubMed

    Neumann, Kay; Cavalar, Markus; Rody, Achim; Friemert, Luisa; Beyer, Daniel A

    2018-02-01

    Growing evidence shows a causal role of high-risk humane papillomavirus (HPV) infections in the development of head and neck cancer. A recent case report shows two patients suffering from tonsillar cancer without any risk factors apart from their work as gynecologists doing laser ablations and loop electrosurgical excision procedures (LEEP). The aim of the present investigation is to evaluate whether surgical plume resulting from routine LEEPs of HSIL of the cervix uteri might be contaminated with the DNA of high-risk HPV. The prospective pilot study is done at the Department of Gynecology and Obstetrics of the University of Lübeck, Germany. The primary outcome was defined as HPV subtype in resected cone and in surgical plume resulting from LEEPs of HSIL of the cervix uteri. Plume resulting from LEEPs was analyzed using a Whatman FTA Elute Indicating Card which was placed in the tube of an exhaust suction device used to remove the resulting aerosols. For detection of HPV and analysis of its subtype, the novel EUROArray HPV test was performed. Resected cones of LEEPs were evaluated separately for HPV subtypes. Four samples of surgical plume resulting from routine LEEPs indicated contamination with high-risk HPV and showed the same HPV subtype as identified in the resected cones. Surgical plume resulting from routine LEEPs for HSIL of the cervix uteri has the risk of contamination with high-risk HPV. Further investigations of infectiousness of surgical plume are necessary for evaluation of potential hazards to involved healthcare professionals.

  19. Plume-ridge interaction: Shaping the geometry of mid-ocean ridges

    NASA Astrophysics Data System (ADS)

    Mittelstaedt, Eric L.

    Manifestations of plume-ridge interaction are found across the ocean basins. Currently there are interactions between at least 21 hot spots and nearby ridges along 15--20% of the global mid-ocean ridge network. These interactions produce a number of anomalies including the presence of elevated topography, negative gravity anomalies, and anomalous crustal production. One form of anomalous crustal production is the formation of volcanic lineaments between hotspots and nearby mid-ocean ridges. In addition, observations indicate that mantle plumes tend to "capture" nearby mid-ocean ridges through asymmetric spreading, increased ridge propagation, and discrete shifts of the ridge axis, or ridge jumps. The initiation of ridge jumps and the formation of off-axis volcanic lineaments likely involve similar processes and may be closely related. In the following work, I use theoretical and numerical models to quantify the processes that control the formation of volcanic lineaments (Chapter 2), the initiation of mid-ocean ridge jumps associated with lithospheric heating due to magma passing through the plate (Chapter 3), and the initiation of jumps due to an upwelling mantle plume and magmatic heating governed by melt migration (Chapter 4). Results indicate that lineaments and ridge jumps associated with plume-ridge interaction are most likely to occur on young lithosphere. The shape of lineaments on the seafloor is predicted to be controlled by the pattern of lithospheric stresses associated with a laterally spreading, near-ridge mantle plume. Ridge jumps are likely to occur due to magmatic heating alone only in lithosphere ˜1Myr old, because the heating rate required to jump increases with spreading rate and plate age. The added effect of an upwelling plume introduces competing effects that both promote and inhibit ridge jumps. For models where magmatic heating is controlled by melt migration, repeat ridge jumps are predicted to occur as the plume and ridge separate, but

  20. Controls on Plume Spacing and Plume Population in 3-D High Rayleigh Number Thermal Convection

    NASA Astrophysics Data System (ADS)

    Zhong, S.

    2004-12-01

    Dynamics of mantle plumes are important for understanding intra-plate volcanism and heat transfer in the mantle. Using 3D numerical models and scaling analyses, we investigated the controls of convective vigor or Ra on the dynamics of thermal plumes in isoviscous and basal heating thermal convection. We examined Ra-dependence of plume population, plume spacing, plume vertical velocity, and plume radius. We found that plume population does not increase with Ra monotonically. At relatively small Ra (<106), plume population is insensitive to Ra. For 3x106plume population scales as Ra0.31 and plume spacing ˜ Ra-0.16 ˜ δ 1/2, where δ is the thermal boundary layer thickness. However, for larger Ra ( ˜ 108) plume population and plume spacing become insensitive to Ra again. This indicates that the box depth poses a limit on plume spacing and plume population. We demonstrated from both scaling analyses and numerical experiments that the scaling exponents for plume population, n, heat flux, β , and average velocity on the bottom boundary, v, satisfy n = 4β - 2v. Our scaling analyses also suggest that vertical velocity in upwelling plumes Vup ˜ Ra2(1-n+β /2)/3 and that plume radius Rup ˜ Ra2(β -1-n/2)/3, differing from the scalings for the bottom boundary velocity and boundary layer thickness.

  1. Radiofrequency catheter ablation in patients with symptomatic atrial flutter/tachycardia after orthotopic heart transplantation.

    PubMed

    Li, Yi-gang; Grönefeld, Gerian; Israel, Carsten; Lu, Shang-biao; Wang, Qun-shan; Hohnloser, Stefan H

    2006-12-20

    Atrial tachycardia or flutter is common in patients after orthotopic heart transplantation. Radiofrequency catheter ablation to treat this arrhythmia has not been well defined in this setting. This study was conducted to assess the incidence of various symptomatic atrial arrhythmias and the efficacy and safety of radiofrequency catheter ablation in these patients. Electrophysiological study and catheter ablation were performed in patients with symptomatic tachyarrhythmia. One Halo catheter with 20 poles was positioned around the tricuspid annulus of the donor right atrium, or positioned around the surgical anastomosis when it is necessary. Three quadripolar electrode catheters were inserted via the right or left femoral vein and positioned in the recipient atrium, the bundle of His position, the coronary sinus. Programmed atrial stimulation and burst pacing were performed to prove electrical conduction between the recipient and the donor atria and to induce atrial arrhythmias. Out of 55 consecutive heart transplantation patients, 6 males [(58 +/- 12) years] developed symptomatic tachycardias at a mean of (5 +/- 4) years after heart transplantation. Electrical propagation through the suture line between the recipient and the donor atrium was demonstrated during atrial flutter or during recipient atrium and donor atrium pacing in 2 patients. By mapping around the suture line, the earliest fragmented electrogram of donor atrium was assessed. This electrical connection was successfully ablated in the anterior lateral atrium in both patients. There was no electrical propagation through the suture line in the other 4 patients. Two had typical atrial flutter in the donor atrium which was successfully ablated by completing a linear ablation between the tricuspid annulus and the inferior vena cava. Two patients had atrial tachycardia which was ablated in the anterior septal and lateral donor atrium. There were no procedure-related complications. Patients were free of

  2. Imaging spectroscopy of polymer ablation plasmas for laser propulsion applications

    NASA Astrophysics Data System (ADS)

    Jiao, Long; Truscott, Benjamin S.; Liu, Hao; Ashfold, Michael N. R.; Ma, Honghao

    2017-01-01

    A number of polymers have been proposed for use as propellants in space launch and thruster applications based on laser ablation, although few prior studies have either evaluated their performance at background pressures representative of the upper atmosphere or investigated interactions with ambient gases other than air. Here, we use spatially and temporally resolved optical emission spectroscopy to compare three polymers, poly(ethylene), poly(oxymethylene), and glycidyl azide polymer, ablated using a 532 nm, nanosecond pulsed laser under Ar and O2 at pressures below 1 Torr. Emission lines from neutrally and positively charged atoms are observed in each case, along with the recombination radiation at the interaction front between the plasma plume and the background gas. C2 radicals arise either as a direct fragmentation product or by a three-body recombination of C atoms, depending on the structure of the polymer backbone, and exhibit a rotational temperature of ≈5000 K. The Sedov-Taylor point blast model is used to infer the energy release relative to the incident laser energy, which for all polymers is greater in the presence of O2, as to be expected based on their negative oxygen balance. Under Ar, plume confinement is seen to enhance the self-reactivity of the ejecta from poly(oxymethylene) and glycidyl azide polymer, with maximum exothermicity close to 0.5 Torr. However, little advantage of the latter, widely considered one of the most promising energetic polymers, is apparent under the present conditions over the former, a common engineering plastic.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  4. Magneto-absorption effects in magnetic-field assisted laser ablation of silicon by UV nanosecond pulses

    NASA Astrophysics Data System (ADS)

    Farrokhi, H.; Gruzdev, V.; Zheng, H. Y.; Rawat, R. S.; Zhou, W.

    2016-06-01

    A constant magnetic field can significantly improve the quality and speed of ablation by nanosecond laser pulses. These improvements are usually attributed to the confinement of laser-produced plasma by the magnetic field and specific propagation effects in the magnetized plasma. Here we report a strong influence of constant axial magnetic field on the ablation of silicon by 20-ns laser pulses at wavelength 355 nm, which results in an increase of ablation depth by a factor of 1.3 to 69 depending on laser parameters and magnitude of the magnetic field. The traditional plasma effects do not explain this result, and magneto-absorption of silicon is proposed as one of the major mechanisms of the significant enhancement of ablation.

  5. Detecting frontal ablation processes from direct observations of submarine terminus morphology

    NASA Astrophysics Data System (ADS)

    Fried, M.; Carroll, D.; Catania, G. A.; Sutherland, D. A.; Stearns, L. A.; Bartholomaus, T. C.; Shroyer, E.; Nash, J. D.

    2017-12-01

    Tidewater glacier termini couple glacier and ocean systems. Subglacial discharge emerging from the terminus produces buoyant plumes that modulate submarine melting, calving, fjord circulation and, in turn, changes in ice dynamics from back-stress perturbations. However, the absence of critical observational data at the ice-ocean interface limits plume and, by extension, melt models from incorporating realistic submarine terminus face morphologies and assessing their impact on terminus behavior at tidewater glaciers. Here we present a comprehensive inventory and characterization of submarine terminus face shapes from a side-looking, multibeam echo sounding campaign across Kangerdlugssuaq Sermerssua glacier, central-west Greenland. We combine these observations with in-situ measurements of ocean stratification and remotely sensed subglacial discharge, terminus positions, ice velocity, and ice surface datasets to infer the spectrum of processes sculpting the submarine terminus face. Subglacial discharge outlet locations are confirmed through observations of sediment plumes, localized melt-driven undercutting of the terminus face, and bathymetry of the adjacent seafloor. From our analysis, we differentiate terminus morphologies resulting from submarine melt and calving and assess the contribution of each process to the net frontal ablation budget. Finally, we constrain a plume model using direct observations of the submarine terminus face and conduit geometry. Plume model simulations demonstrate that the majority of discharge outlets are fed by small discharge fluxes, suggestive of a distributed subglacial hydrologic system. Outlets with the largest, concentrated discharge fluxes are morphologically unique and strongly control seasonal terminus position. At these locations, we show that the spatiotemporal pattern of terminus retreat is well correlated with time periods when local melt rate exceeds ice velocity.

  6. Orbital Maneuvering Vehicle (OMV) plume and plume effects study

    NASA Technical Reports Server (NTRS)

    Smith, Sheldon D.

    1991-01-01

    The objective was to characterize the Orbital Maneuvering Vehicle (OMV) propulsion and attitude control system engine exhaust plumes and predict the resultant plume impingement pressure, heat loads, forces, and moments. Detailed description is provided of the OMV gaseous nitrogen (GN2) thruster exhaust plume flow field characteristics calculated with the RAMP2 snd SFPGEN computer codes. Brief descriptions are included of the two models, GN2 thruster characteristics and RAMP2 input data files. The RAMP2 flow field could be recalculated by other organizations using the information presented. The GN2 flow field can be readily used by other organizations who are interested in GN2 plume induced environments which require local flow field properties which can be supplied using the SFPGEN GN2 model.

  7. Modeling Europa's dust plumes

    NASA Astrophysics Data System (ADS)

    Southworth, B. S.; Kempf, S.; Schmidt, J.

    2015-12-01

    The discovery of Jupiter's moon Europa maintaining a probably sporadic water vapor plume constitutes a huge scientific opportunity for NASA's upcoming mission to this Galilean moon. Measuring properties of material emerging from interior sources offers a unique chance to understand conditions at Europa's subsurface ocean. Exploiting results obtained for the Enceladus plume, we simulate possible Europa plume configurations, analyze particle number density and surface deposition results, and estimate the expected flux of ice grains on a spacecraft. Due to Europa's high escape speed, observing an active plume will require low-altitude flybys, preferably at altitudes of 5-100 km. At higher altitudes a plume may escape detection. Our simulations provide an extensive library documenting the possible structure of Europa dust plumes, which can be quickly refined as more data on Europa dust plumes are collected.

  8. The effect of wind on the dispersal of a tropical small river plume

    NASA Astrophysics Data System (ADS)

    Zhao, Junpeng; Gong, Wenping; Shen, Jian

    2018-03-01

    Wanquan River is a small river located in Hainan, a tropical island in China. As the third largest river in Hainan, the river plume plays an important role in the regional terrigenous mass transport, coastal circulation, and the coral reef's ecosystem. Studies have shown that wind forcings significantly influence river plume dynamics. In this study, wind effects on the dispersal of the river plume and freshwater transport were examined numerically using a calibrated, unstructured, finite volume numerical model (FVCOM). Both wind direction and magnitude were determined to influence plume dispersal. Northeasterly (downwelling-favorable) winds drove freshwater down-shelf while southeasterly (onshore) winds drove water up-shelf (in the sense of Kelvin wave propagation), and were confined near the coast. Southwesterly (upwelling-favorable) and north-westerly (offshore) winds transport more freshwater offshore. The transport flux is decomposed into an advection, a vertical shear, and an oscillatory component. The advection flux dominates the freshwater transport in the coastal area and the vertical shear flux is dominant in the offshore area. For the upwelling-favorable wind, the freshwater transport becomes more controlled by the advection transport with an increase in wind stress, due to enhanced vertical mixing. The relative importance of wind forcing and buoyancy force was investigated. It was found that, when the Wedderburn number is larger than one, the plume was dominated by wind forcing, although the importance of wind varies in different parts of the plume. The water column stratification decreased as a whole under the prevailing southwesterly wind, with the exception of the up-shelf and offshore areas.

  9. Predictive analysis of optical ablation in several dermatological tumoral tissues

    NASA Astrophysics Data System (ADS)

    Fanjul-Vélez, F.; Blanco-Gutiérrez, A.; Salas-García, I.; Ortega-Quijano, N.; Arce-Diego, J. L.

    2013-06-01

    Optical techniques for treatment and characterization of biological tissues are revolutionizing several branches of medical praxis, for example in ophthalmology or dermatology. The non-invasive, non-contact and non-ionizing character of optical radiation makes it specially suitable for these applications. Optical radiation can be employed in medical ablation applications, either for tissue resection or surgery. Optical ablation may provide a controlled and clean cut on a biological tissue. This is particularly relevant in tumoral tissue resection, where a small amount of cancerous cells could make the tumor appear again. A very important aspect of tissue optical ablation is then the estimation of the affected volume. In this work we propose a complete predictive model of tissue ablation that provides an estimation of the resected volume. The model is based on a Monte Carlo approach for the optical propagation of radiation inside the tissue, and a blow-off model for tissue ablation. This model is applied to several types of dermatological tumoral tissues, specifically squamous cells, basocellular and infiltrative carcinomas. The parameters of the optical source are varied and the estimated resected volume is calculated. The results for the different tumor types are presented and compared. This model can be used for surgical planning, in order to assure the complete resection of the tumoral tissue.

  10. Modification of modulated plasma plumes for the quasi-phase-matching of high-order harmonics in different spectral ranges

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

    Ganeev, R. A., E-mail: rashid-ganeev@mail.ru; Ophthalmology and Advanced Laser Medical Center, Saitama Medical University, Saitama 350-0495; Boltaev, G. S.

    We demonstrate the technique allowing the fine tuning of the distance between the laser-produced plasma plumes on the surfaces of different materials, as well as the variation of the sizes of these plumes. The modification of plasma formations is based on the tilting of the multi-slit mask placed between the heating laser beam and target surface, as well as the positioning of this mask in the telescope placed on the path of heating radiation. The modulated plasma plumes with the sizes of single plume ranging between 0.1 and 1 mm were produced on the manganese and silver targets. Modification of themore » geometrical parameters of plasma plumes proved to be useful for the fine tuning of the quasi-phase-matched high-order harmonics generated in such structures during propagation of the ultrashort laser pulses. We show the enhancement of some groups of harmonics along the plateau range and the tuning of maximally enhanced harmonic by variable modulation of the plasma.« less

  11. An evaluation of modeled plume injection height with satellite-derived observed plume height

    Treesearch

    Sean M. Raffuse; Kenneth J. Craig; Narasimhan K. Larkin; Tara T. Strand; Dana Coe Sullivan; Neil J.M. Wheeler; Robert Solomon

    2012-01-01

    Plume injection height influences plume transport characteristics, such as range and potential for dilution. We evaluated plume injection height from a predictive wildland fire smoke transport model over the contiguous United States (U.S.) from 2006 to 2008 using satellite-derived information, including plume top heights from the Multi-angle Imaging SpectroRadiometer (...

  12. Estimation of Al2O3 critical temperature using a Langmuir probe in laser ablation

    NASA Astrophysics Data System (ADS)

    Yahiaoui, K.; Abdelli-Messaci, S.; Messaoud Aberkane, S.; Kellou, A.

    2016-11-01

    Pulsed laser deposition (PLD) has demonstrated its capacity in thin films growing under the moderate laser intensity. But when the laser intensity increases, the presence of droplets on the thin film limits the PLD efficiency such that the process needs an optimization study. In this way, an experimental study has been conducted in order to correlate between the appearance of those droplets and the laser fluence. The comprehension of the physical mechanism during ablation and the control of the deposition parameters allowed to get a safe process. Our experiment consists in measuring the amount of ejected matter from polycrystalline alumina target as a function of the laser fluence when irradiated by a KrF laser. According to laser fluence, several kinds of ablation regimes have been identified. Below a threshold value found as 12 J/cm2, the mechanism of ablation was assigned to normal evaporation, desorption and nonthermal processes. While above this threshold value, the mechanism of ablation was assigned to phase explosion phenomenon which is responsible of droplets formation when the surface temperature approaches the critical temperature T tc. A negative charge collector was used to collect the positive ions in the plume. Their times of flight (TOF) signal were used to estimate the appropriate T tc for alumina target. Ions yield, current as well as kinetic energy were deduced from the TOF signal. Their evolutions show the occurrence of an optical breakdown in the vapor plume which is well correlated with the onset of the phase explosion phenomenon. At 10 J/cm2, the ions velocities collected by the probe have been compared to those obtained from optical emission spectroscopy diagnostic and were discussed. To prove the occurrence of phase explosion by the appearance of droplets, several thin films were elaborated on Si (100) substrate at different laser fluence into vacuum. They have been characterized by scanning electron microscope. The results were well

  13. Ablation of multi-wavelet re-entry: general principles and in silico analyses.

    PubMed

    Spector, Peter S; Correa de Sa, Daniel D; Tischler, Ethan S; Thompson, Nathaniel C; Habel, Nicole; Stinnett-Donnelly, Justin; Benson, Bryce E; Bielau, Philipp; Bates, Jason H T

    2012-11-01

    Catheter ablation strategies for treatment of cardiac arrhythmias are quite successful when targeting spatially constrained substrates. Complex, dynamic, and spatially varying substrates, however, pose a significant challenge for ablation, which delivers spatially fixed lesions. We describe tissue excitation using concepts of surface topology which provides a framework for addressing this challenge. The aim of this study was to test the efficacy of mechanism-based ablation strategies in the setting of complex dynamic substrates. We used a computational model of propagation through electrically excitable tissue to test the effects of ablation on excitation patterns of progressively greater complexity, from fixed rotors to multi-wavelet re-entry. Our results indicate that (i) focal ablation at a spiral-wave core does not result in termination; (ii) termination requires linear lesions from the tissue edge to the spiral-wave core; (iii) meandering spiral-waves terminate upon collision with a boundary (linear lesion or tissue edge); (iv) the probability of terminating multi-wavelet re-entry is proportional to the ratio of total boundary length to tissue area; (v) the efficacy of linear lesions varies directly with the regional density of spiral-waves. We establish a theoretical framework for re-entrant arrhythmias that explains the requirements for their successful treatment. We demonstrate the inadequacy of focal ablation for spatially fixed spiral-waves. Mechanistically guided principles for ablating multi-wavelet re-entry are provided. The potential to capitalize upon regional heterogeneity of spiral-wave density for improved ablation efficacy is described.

  14. Combining Laser Ablation/Liquid Phase Collection Surface Sampling and High-Performance Liquid Chromatography Electrospray Ionization Mass Spectrometry

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

    Ovchinnikova, Olga S; Kertesz, Vilmos; Van Berkel, Gary J

    This paper describes the coupling of ambient pressure transmission geometry laser ablation with a liquid phase sample collection method for surface sampling and ionization with subsequent mass spectral analysis. A commercially available autosampler was adapted to produce a liquid droplet at the end of the syringe injection needle while in close proximity to the surface to collect the sample plume produced by laser ablation. The sample collection was followed by either flow injection or a high performance liquid chromatography (HPLC) separation of the extracted components and detection with electrospray ionization mass spectrometry (ESI-MS). To illustrate the analytical utility of thismore » coupling, thin films of a commercial ink sample containing rhodamine 6G and of mixed isobaric rhodamine B and 6G dyes on glass microscope slides were analyzed. The flow injection and HPLC/ESI-MS analysis revealed successful laser ablation, capture and, with HPLC, the separation of the two compounds. The ablated circular area was about 70 m in diameter for these experiments. The spatial sampling resolution afforded by the laser ablation, as well as the ability to use sample processing methods like HPLC between the sample collection and ionization steps, makes this combined surface sampling/ionization technique a highly versatile analytical tool.« less

  15. Waves, Plumes and Bubbles from Jupiter Comet Impacts

    NASA Astrophysics Data System (ADS)

    Palotai, Csaba J.; Sankar, Ramanakumar; McCabe, Tyler; Korycansky, Donald

    2017-10-01

    We present results from our numerical simulations of jovian comet impacts that investigate various phases of the Shoemaker-Levy 9 (SL9) and the 2009 impacts into Jupiter's atmosphere. Our work includes a linked series of observationally constrained, three-dimensional radiative-hydrodynamic simulations to model the impact, plume blowout, plume flight/splash, and wave-propagation phases of those impact events. Studying these stages using a single model is challenging because the spatial and temporal scales and the temperature range of those phases may differ by orders of magnitudes (Harrington et al. 2004). In our simulations we model subsequent phases starting with the interpolation of the results of previous simulations onto a new, larger grid that is optimized for capturing all key physics of the relevant phenomena while maintaining computational efficiency. This enables us to carry out end-to-end simulations that require no ad-hoc initial conditions. In this work, we focus on the waves generated by various phenomena during the impact event and study the temporal evolution of their position and speed. In particular, we investigate the shocks generated by the impactor during atmospheric entry, the expansion of the ejected plume and the ascent of the hot bubble of material from terminal depth. These results are compared to the observed characteristics of the expanding SL9 rings (Hammel et al. 1995). Additionally, we present results from our sensitivity tests that focus on studying the differences in the ejecta plume generation using various impactor parameters (e.g., impact angle, impactor size, material, etc.). These simulations are used to explain various phenomena related to the SL9 event and to constrain the characteristics of the unknown 2009 impactor body. This research was supported by National Science Foundation Grant AST-1627409.

  16. Investigation of power-plant plume photochemistry using a reactive plume model

    NASA Astrophysics Data System (ADS)

    Kim, Y. H.; Kim, H. S.; Song, C. H.

    2016-12-01

    Emissions from large-scale point sources have continuously increased due to the rapid industrial growth. In particular, primary and secondary air pollutants are directly relevant to atmospheric environment and human health. Thus, we tried to precisely describe the atmospheric photochemical conversion from primary to secondary air pollutants inside the plumes emitted from large-scale point sources. A reactive plume model (RPM) was developed to comprehensively consider power-plant plume photochemistry with 255 condensed photochemical reactions. The RPM can simulate two main components of power-plant plumes: turbulent dispersion of plumes and compositional changes of plumes via photochemical reactions. In order to evaluate the performance of the RPM developed in the present study, two sets of observational data obtained from the TexAQS II 2006 (Texas Air Quality Study II 2006) campaign were compared with RPM-simulated data. Comparison shows that the RPM produces relatively accurate concentrations for major primary and secondary in-plume species such as NO2, SO2, ozone, and H2SO4. Statistical analyses show good correlation, with correlation coefficients (R) ranging from 0.61 to 0.92, and good agreement with the Index of Agreement (IOA) ranging from 0.70 to 0.95. Following evaluation of the performance of the RPM, a demonstration was also carried out to show the applicability of the RPM. The RPM can calculate NOx photochemical lifetimes inside the two plumes (Monticello and Welsh power plants). Further applicability and possible uses of the RPM are also discussed together with some limitations of the current version of the RPM.

  17. 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

  18. Tvashtar's Plume

    NASA Technical Reports Server (NTRS)

    2007-01-01

    This dramatic image of Io was taken by the Long Range Reconnaissance Imager (LORRI) on New Horizons at 11:04 Universal Time on February 28, 2007, just about 5 hours after the spacecraft's closest approach to Jupiter. The distance to Io was 2.5 million kilometers (1.5 million miles) and the image is centered at 85 degrees west longitude. At this distance, one LORRI pixel subtends 12 kilometers (7.4 miles) on Io.

    This processed image provides the best view yet of the enormous 290-kilometer (180-mile) high plume from the volcano Tvashtar, in the 11 o'clock direction near Io's north pole. The plume was first seen by the Hubble Space Telescope two weeks ago and then by New Horizons on February 26; this image is clearer than the February 26 image because Io was closer to the spacecraft, the plume was more backlit by the Sun, and a longer exposure time (75 milliseconds versus 20 milliseconds) was used. Io's dayside was deliberately overexposed in this picture to image the faint plumes, and the long exposure also provided an excellent view of Io's night side, illuminated by Jupiter. The remarkable filamentary structure in the Tvashtar plume is similar to details glimpsed faintly in 1979 Voyager images of a similar plume produced by Io's volcano Pele. However, no previous image by any spacecraft has shown these mysterious structures so clearly.

    The image also shows the much smaller symmetrical fountain of the plume, about 60 kilometers (or 40 miles) high, from the Prometheus volcano in the 9 o'clock direction. The top of a third volcanic plume, from the volcano Masubi, erupts high enough to catch the setting Sun on the night side near the bottom of the image, appearing as an irregular bright patch against Io's Jupiter-lit surface. Several Everest-sized mountains are highlighted by the setting Sun along the terminator, the line between day and night.

    This is the last of a handful of LORRI images that New Horizons is sending 'home' during its busy close

  19. Mantle plume capture, anchoring, and outflow during Galápagos plume-ridge interaction

    NASA Astrophysics Data System (ADS)

    Gibson, S. A.; Geist, D. J.; Richards, M. A.

    2015-05-01

    Compositions of basalts erupted between the main zone of Galápagos plume upwelling and adjacent Galápagos Spreading Center (GSC) provide important constraints on dynamic processes involved in transfer of deep-mantle-sourced material to mid-ocean ridges. We examine recent basalts from central and northeast Galápagos including some that have less radiogenic Sr, Nd, and Pb isotopic compositions than plume-influenced basalts (E-MORB) from the nearby ridge. We show that the location of E-MORB, greatest crustal thickness, and elevated topography on the GSC correlates with a confined zone of low-velocity, high-temperature mantle connecting the plume stem and ridge at depths of ˜100 km. At this site on the ridge, plume-driven upwelling involving deep melting of partially dehydrated, recycled ancient oceanic crust, plus plate-limited shallow melting of anhydrous peridotite, generate E-MORB and larger amounts of melt than elsewhere on the GSC. The first-order control on plume stem to ridge flow is rheological rather than gravitational, and strongly influenced by flow regimes initiated when the plume was on axis (>5 Ma). During subsequent northeast ridge migration material upwelling in the plume stem appears to have remained "anchored" to a contact point on the GSC. This deep, confined NE plume stem-to-ridge flow occurs via a network of melt channels, embedded within the normal spreading and advection of plume material beneath the Nazca plate, and coincides with locations of historic volcanism. Our observations require a more dynamically complex model than proposed by most studies, which rely on radial solid-state outflow of heterogeneous plume material to the ridge.

  20. Constraining the Enceladus plume using numerical simulation and Cassini data

    NASA Astrophysics Data System (ADS)

    Yeoh, Seng Keat; Li, Zheng; Goldstein, David B.; Varghese, Philip L.; Levin, Deborah A.; Trafton, Laurence M.

    2017-01-01

    Since its discovery, the Enceladus plume has been subjected to intense study due to the major effects that it has on the Saturnian system and the window that it provides into the interior of Enceladus. However, several questions remain and we attempt to answer some of them in this work. In particular, we aim to constrain the H2O production rate from the plume, evaluate the relative importance of the jets and the distributed sources along the Tiger Stripes, and make inferences about the source of the plume by accurately modeling the plume and constraining the model using the Cassini INMS and UVIS data. This is an extension of a previous work (Yeoh, S.K., et al. [2015] Icarus, 253, 205-222) in which we only modeled the collisional part of the Enceladus plume and studied its important physical processes. In this work, we propagate the plume farther into space where the flow has become free-molecular and the Cassini INMS and UVIS data were sampled. Then, we fit this part of the plume to the INMS H2O density distributions sampled along the E3, E5 and E7 trajectories and also compare some of the fit results with the UVIS measurements of the plume optical depth collected during the solar occultation observation on 18 May 2010. We consider several vent conditions and source configurations for the plume. By constraining our model using the INMS and UVIS data, we estimate H2O production rates of several hundred kgs-1: 400-500 kg/s during the E3 and E7 flybys and ∼900 kg/s during the E5 flyby. These values agree with other estimates and are consistent with the observed temporal variability of the plume over the orbital period of Enceladus (Hedman, M.M., et al. [2013] Nature, 500, 182-184). In addition, we determine that one of the Tiger Stripes, Cairo, exhibits a local temporal variability consistent with the observed overall temporal variability of the plume. We also find that the distributed sources along the Tiger Stripes are likely dominant while the jets provide a

  1. Mitigate the tent-induced perturbation in ignition capsules by supersonic radiation propagation

    NASA Astrophysics Data System (ADS)

    Dai, Zhensheng; Gu, Jianfa; Zheng, Wudi

    2017-10-01

    In the inertial confinement fusion (ICF) scheme, to trap the alpha particle products of the D-T reaction, the capsules needs to be imploded and compressed with high symmetry In the laser indirect drive scheme, the capsules are held at the center of high-Z hohlraums by thin membranes (tents). However, the tents are recognized as one of the most important contributors to hot spot asymmetries, areal density perturbations and reduced performance. To improve the capsule implosion performance, various alternatives such as the micro-scale rods, a larger fill-tube and a low-density foam layer around the capsule have been presented. Our simulations show that the radiation propagates supersonically in the low-density foam layer and starts to ablate the capsule before the perturbations induced by the tents reach the ablating fronts. The tent induced perturbations are remarkably weakened when they are propagating in the blow-off plasma.

  2. Comparison of remote magnetic navigation ablation and manual ablation of idiopathic ventricular arrhythmia after failed manual ablation.

    PubMed

    Kawamura, Mitsuharu; Scheinman, Melvin M; Tseng, Zian H; Lee, Byron K; Marcus, Gregory M; Badhwar, Nitish

    2017-01-01

    Catheter ablation for idiopathic ventricular arrhythmia (VA) is effective and safe, but efficacy is frequently limited due to an epicardial origin and difficult anatomy. The remote magnetic navigation (RMN) catheter has a flexible catheter design allowing access to difficult anatomy. We describe the efficacy of the RMN for ablation of idiopathic VA after failed manual ablation. Among 235 patients with idiopathic VA referred for catheter ablation, we identified 51 patients who were referred for repeat ablation after a failed manual ablation. We analyzed the clinical characteristics, including the successful ablation site and findings at electrophysiology study, in repeat procedures conducted using RMN as compared with manual ablation. Among these patients, 22 (43 %) underwent repeat ablation with the RMN and 29 (57 %) underwent repeat ablation with a manual ablation. Overall, successful ablation rate was significantly higher using RMN as compared with manual ablation (91 vs. 69 %, P = 0.02). Fluoroscopy time in the RMN was 17 ± 12 min as compared with 43 ± 18 min in the manual ablation (P = 0.009). Successful ablation rate in the posterior right ventricular outflow tract (RVOT) plus posterior-tricuspid annulus was higher with RMN as compared with manual ablation (92 vs. 50 %, P = 0.03). Neither groups exhibited any major complications. The RMN is more effective in selected patients with recurrent idiopathic VA after failed manual ablation and is associated with less fluoroscopy time. The RMN catheters have a flexible design enabling them to access otherwise difficult anatomy including the posterior tricuspid annulus and posterior RVOT.

  3. Flow speed of the ablation vapors generated during laser drilling of CFRP with a continuous-wave laser beam

    NASA Astrophysics Data System (ADS)

    Faas, S.; Freitag, C.; Boley, S.; Berger, P.; Weber, R.; Graf, T.

    2017-03-01

    The hot plume of ablation products generated during the laser drilling process of carbon fiber reinforced plastics (CFRP) with a continuous-wave laser beam was analyzed by means of high-speed imaging. The formation of compression shocks was observed within the flow of the evaporated material, which is an indication of flow speeds well above the local speed of sound. The flow speed of the hot ablation products can be estimated by analyzing the position of these compression shocks. We investigated the temporal evolution of the flow speed during the drilling process and the influence of the average laser power on the flow speed. The flow speed increases with increasing average laser powers. The moment of drilling through the material changes the conditions for the drilling process and was confirmed to influence the flow speed of the ablated material. Compression shocks can also be observed during laser cutting of CFRP with a moving laser beam.

  4. Laser Ablation Molecular Isotopic Spectrometry for Molecules Formation Chemistry in Femtosecond-Laser Ablated Plasmas.

    PubMed

    Hou, Huaming; Mao, Xianglei; Zorba, Vassilia; Russo, Richard E

    2017-07-18

    Recently, laser ablated molecular isotopic spectrometry (LAMIS) has expanded its capability to explore molecules formation mechanism in laser-induced plasma in addition to isotope analysis. LAMIS is a powerful tool for tracking the origination of atoms that is involved in formation of investigated molecules by labeling atoms with their isotopic substitution. The evolutionary formation pathways of organic molecules, especially of C 2 dimers and CN radicals, were frequently reported. However, very little is known about the formation pathways for metallic radicals and heterodimers in laser ablated plasma. This research focuses on elucidating the formation pathways of AlO radicals in femtosecond laser ablated plasma from 18 O-labeled Al 2 O 3 pellet. Plasmas expanding with strong forward bias in the direction normal to the sample surface were generated in the wake of a weakly ionized channel created by a femtosecond laser. The formation mechanism of AlO and influence of air were investigated with multiple plasma diagnostic methods such as monochromatic fast gating imaging, spatiotemporal resolved optical emission spectroscopy, and LAMIS. An advanced LAMIS fitting procedure was used to deduce the spatiotemporal distributions of Al 18 O and Al 16 O number densities and also their ratios. We found that the Al 16 O/Al 18 O number density ratio is higher for plasma portion closer to the sample surface, which suggests that chemical reactions between the plasma plume and ambient air are more intense at the tail of the plasma. The results also reveals that direct association of free Al and O atoms is the main mechanism for the formation of AlO at the early stage of the plasma. To the contrast, chemical reactions between plasma materials and ambient oxygen molecules and the isotope exchange effect are the dominant mechanisms of the formation of AlO and evolution of Al 16 O/Al 18 O number density ratio at the late stage of the plasma.

  5. The effect of elastic modulus on ablation catheter contact area.

    PubMed

    Camp, Jon J; Linte, Cristian A; Rettmann, Maryam E; Sun, Deyu; Packer, Douglas L; Robb, Richard A; Holmes, David R

    2015-02-21

    Cardiac ablation consists of navigating a catheter into the heart and delivering RF energy to electrically isolate tissue regions that generate or propagate arrhythmia. Besides the challenges of accurate and precise targeting of the arrhythmic sites within the beating heart, limited information is currently available to the cardiologist regarding intricate electrode-tissue contact, which directly impacts the quality of produced lesions. Recent advances in ablation catheter design provide intra-procedural estimates of tissue-catheter contact force, but the most direct indicator of lesion quality for any particular energy level and duration is the tissue-catheter contact area, and that is a function of not only force, but catheter pose and material elasticity as well. In this experiment, we have employed real-time ultrasound (US) imaging to determine the complete interaction between the ablation electrode and tissue to accurately estimate contact, which will help to better understand the effect of catheter pose and position relative to the tissue. By simultaneously recording tracked position, force reading and US image of the ablation catheter, the differing material properties of polyvinyl alcohol cryogel [1] phantoms are shown to produce varying amounts of tissue depression and contact area (implying varying lesion quality) for equivalent force readings. We have shown that the elastic modulus significantly affects the surface-contact area between the catheter and tissue at any level of contact force. Thus we provide evidence that a prescribed level of catheter force may not always provide sufficient contact area to produce an effective ablation lesion in the prescribed ablation time.

  6. Dynamic absorption and scattering of water and hydrogel during high-repetition-rate (>100 MHz) burst-mode ultrafast-pulse laser ablation.

    PubMed

    Qian, Zuoming; Covarrubias, Andrés; Grindal, Alexander W; Akens, Margarete K; Lilge, Lothar; Marjoribanks, Robin S

    2016-06-01

    High-repetition-rate burst-mode ultrafast-laser ablation and disruption of biological tissues depends on interaction of each pulse with the sample, but under those particular conditions which persist from previous pulses. This work characterizes and compares the dynamics of absorption and scattering of a 133-MHz repetition-rate, burst-mode ultrafast-pulse laser, in agar hydrogel targets and distilled water. The differences in energy partition are quantified, pulse-by-pulse, using a time-resolving integrating-sphere-based device. These measurements reveal that high-repetition-rate burst-mode ultrafast-laser ablation is a highly dynamical process affected by the persistence of ionization, dissipation of plasma plume, neutral material flow, tissue tensile strength, and the hydrodynamic oscillation of cavitation bubbles.

  7. Seismic Imaging of Mantle Plumes

    NASA Astrophysics Data System (ADS)

    Nataf, Henri-Claude

    The mantle plume hypothesis was proposed thirty years ago by Jason Morgan to explain hotspot volcanoes such as Hawaii. A thermal diapir (or plume) rises from the thermal boundary layer at the base of the mantle and produces a chain of volcanoes as a plate moves on top of it. The idea is very attractive, but direct evidence for actual plumes is weak, and many questions remain unanswered. With the great improvement of seismic imagery in the past ten years, new prospects have arisen. Mantle plumes are expected to be rather narrow, and their detection by seismic techniques requires specific developments as well as dedicated field experiments. Regional travel-time tomography has provided good evidence for plumes in the upper mantle beneath a few hotspots (Yellowstone, Massif Central, Iceland). Beneath Hawaii and Iceland, the plume can be detected in the transition zone because it deflects the seismic discontinuities at 410 and 660 km depths. In the lower mantle, plumes are very difficult to detect, so specific methods have been worked out for this purpose. There are hints of a plume beneath the weak Bowie hotspot, as well as intriguing observations for Hawaii. Beneath Iceland, high-resolution tomography has just revealed a wide and meandering plume-like structure extending from the core-mantle boundary up to the surface. Among the many phenomena that seem to take place in the lowermost mantle (or D''), there are also signs there of the presence of plumes. In this article I review the main results obtained so far from these studies and discuss their implications for plume dynamics. Seismic imaging of mantle plumes is still in its infancy but should soon become a turbulent teenager.

  8. Low altitude plume impingement handbook

    NASA Technical Reports Server (NTRS)

    Smith, Sheldon D.

    1991-01-01

    Plume Impingement modeling is required whenever an object immersed in a rocket exhaust plume must survive or remain undamaged within specified limits, due to thermal and pressure environments induced by the plume. At high altitudes inviscid plume models, Monte Carlo techniques along with the Plume Impingement Program can be used to predict reasonably accurate environments since there are usually no strong flowfield/body interactions or atmospheric effects. However, at low altitudes there is plume-atmospheric mixing and potential large flowfield perturbations due to plume-structure interaction. If the impinged surface is large relative to the flowfield and the flowfield is supersonic, the shock near the surface can stand off the surface several exit radii. This results in an effective total pressure that is higher than that which exists in the free plume at the surface. Additionally, in two phase plumes, there can be strong particle-gas interaction in the flowfield immediately ahead of the surface. To date there have been three levels of sophistication that have been used for low altitude plume induced environment predictions. Level 1 calculations rely on empirical characterizations of the flowfield and relatively simple impingement modeling. An example of this technique is described by Piesik. A Level 2 approach consists of characterizing the viscous plume using the SPF/2 code or RAMP2/LAMP and using the Plume Impingement Program to predict the environments. A Level 3 analysis would consist of using a Navier-Stokes code such as the FDNS code to model the flowfield and structure during a single calculation. To date, Level 1 and Level 2 type analyses have been primarily used to perform environment calculations. The recent advances in CFD modeling and computer resources allow Level 2 type analysis to be used for final design studies. Following some background on low altitude impingement, Level 1, 2, and 3 type analysis will be described.

  9. Frontal dynamics at the edge of the Columbia River plume

    NASA Astrophysics Data System (ADS)

    Akan, Çiğdem; McWilliams, James C.; Moghimi, Saeed; Özkan-Haller, H. Tuba

    2018-02-01

    In the tidal ebb-cycle at the Mouth of the Columbia River, strong density and velocity fronts sometimes form perpendicular to the coast at the edges of the freshwater plume. They are distinct from previously analyzed fronts at the offshore western edge of the plume that evolve as a gravity-wave bore. We present simulation results to demonstrate their occurrence and investigate the mechanisms behind their frontogenesis and evolution. Tidal velocities on average ranged between 1.5 m s-1 in flood and 2.5 m s-1 in ebb during the brief hindcast period. The tidal fronts exhibit strong horizontal velocity and buoyancy gradients on a scale ∼ 100 m in width with normalized relative vorticity (ζz/f) values reaching up to 50. We specifically focus on the front on the northern edge of the plume and examine the evolution in plume characteristics such as its water mass gradients, horizontal and vertical velocity structure, vertical velocity, turbulent vertical mixing, horizontal propagation, cross-front momentum balance, and Lagrangian frontogenetic tendencies in both buoyancy and velocity gradients. Advective frontogenesis leads to a very sharp front where lateral mixing near the grid-resolution limit arrests its further contraction. The negative vorticity within the front is initiated by the positive bottom drag curl on the north side of the Columbia estuary and against the north jetty. Because of the large negative vorticity and horizontal vorticity gradient, centrifugal and lateral shear instability begins to develop along the front, but frontal fragmentation and decay set in only after the turn of the tide because of the briefness of the ebb interval.

  10. Discontinuous Galerkin modeling of the Columbia River's coupled estuary-plume dynamics

    NASA Astrophysics Data System (ADS)

    Vallaeys, Valentin; Kärnä, Tuomas; Delandmeter, Philippe; Lambrechts, Jonathan; Baptista, António M.; Deleersnijder, Eric; Hanert, Emmanuel

    2018-04-01

    The Columbia River (CR) estuary is characterized by high river discharge and strong tides that generate high velocity flows and sharp density gradients. Its dynamics strongly affects the coastal ocean circulation. Tidal straining in turn modulates the stratification in the estuary. Simulating the hydrodynamics of the CR estuary and plume therefore requires a multi-scale model as both shelf and estuarine circulations are coupled. Such a model has to keep numerical dissipation as low as possible in order to correctly represent the plume propagation and the salinity intrusion in the estuary. Here, we show that the 3D baroclinic discontinuous Galerkin finite element model SLIM 3D is able to reproduce the main features of the CR estuary-to-ocean continuum. We introduce new vertical discretization and mode splitting that allow us to model a region characterized by complex bathymetry and sharp density and velocity gradients. Our model takes into account the major forcings, i.e. tides, surface wind stress and river discharge, on a single multi-scale grid. The simulation period covers the end of spring-early summer of 2006, a period of high river flow and strong changes in the wind regime. SLIM 3D is validated with in-situ data on the shelf and at multiple locations in the estuary and compared with an operational implementation of SELFE. The model skill in the estuary and on the shelf indicate that SLIM 3D is able to reproduce the key processes driving the river plume dynamics, such as the occurrence of bidirectional plumes or reversals of the inner shelf coastal currents.

  11. Thin films deposited by femtosecond pulsed laser ablation of tungsten carbide

    NASA Astrophysics Data System (ADS)

    De Bonis, A.; Teghil, R.; Santagata, A.; Galasso, A.; Rau, J. V.

    2012-09-01

    Ultra-short Pulsed Laser Deposition has been applied to the production of thin films from a tungsten carbide target. The gaseous phase obtained by the laser ablation shows a very weak primary plume, in contrast with a very strong secondary one. The deposited films, investigated by Scanning Electron Microscopy, Atomic Force Microscopy, X-Ray Photoelectron Spectroscopy and X-Ray Diffraction, present a mixture of WC and other phases with lower carbon content. All films are amorphous, independently from the substrate temperature. The characteristics of the deposits have been explained in terms of thermal evaporation and cooling rate of molten particles ejected from the target.

  12. Thermal imaging of afterburning plumes

    NASA Astrophysics Data System (ADS)

    Ajdari, E.; Gutmark, E.; Parr, T. P.; Wilson, K. J.; Schadow, K. C.

    1989-01-01

    Afterburning and nonafterburning exhaust plumes were studied experimentally for underexpanded sonic and supersonic conical circular nozzles. The plume structure was visualized using thermal imaging camera and regular photography. IR emission by the plume is mainly dependent on the presence of afterburning. Temperature and reducing power of the exhaust gases, in addition to the nozzle configuration, determine the structure of the plume core, the location where the afterburning is initiated, its size and intensity. Comparison between single shot and average thermal images of the plume show that afterburning is a highly turbulent combustion process.

  13. Coastal river plumes: Collisions and coalescence

    USGS Publications Warehouse

    Warrick, Jonathan; Farnsworth, Katherine L

    2017-01-01

    Plumes of buoyant river water spread in the ocean from river mouths, and these plumes influence water quality, sediment dispersal, primary productivity, and circulation along the world’s coasts. Most investigations of river plumes have focused on large rivers in a coastal region, for which the physical spreading of the plume is assumed to be independent from the influence of other buoyant plumes. Here we provide new understanding of the spreading patterns of multiple plumes interacting along simplified coastal settings by investigating: (i) the relative likelihood of plume-to-plume interactions at different settings using geophysical scaling, (ii) the diversity of plume frontal collision types and the effects of these collisions on spreading patterns of plume waters using a two-dimensional hydrodynamic model, and (iii) the fundamental differences in plume spreading patterns between coasts with single and multiple rivers using a three-dimensional hydrodynamic model. Geophysical scaling suggests that coastal margins with numerous small rivers (watershed areas < 10,000 km2), such as found along most active geologic coastal margins, were much more likely to have river plumes that collide and interact than coastal settings with large rivers (watershed areas > 100,000 km2). When two plume fronts meet, several types of collision attributes were found, including refection, subduction and occlusion. We found that the relative differences in pre-collision plume densities and thicknesses strongly influenced the resulting collision types. The three-dimensional spreading of buoyant plumes was found to be influenced by the presence of additional rivers for all modeled scenarios, including those with and without Coriolis and wind. Combined, these results suggest that plume-to-plume interactions are common phenomena for coastal regions offshore of the world’s smaller rivers and for coastal settings with multiple river mouths in close proximity, and that the spreading and

  14. A buoyant plume adjacent to a headland-Observations of the Elwha River plume

    USGS Publications Warehouse

    Warrick, J.A.; Stevens, A.W.

    2011-01-01

    Small rivers commonly discharge into coastal settings with topographic complexities - such as headlands and islands - but these settings are underrepresented in river plume studies compared to more simplified, straight coasts. The Elwha River provides a unique opportunity to study the effects of coastal topography on a buoyant plume, because it discharges into the Strait of Juan de Fuca on the western side of its deltaic headland. Here we show that this headland induces flow separation and transient eddies in the tidally dominated currents (O(100. cm/s)), consistent with other headlands in oscillatory flow. These flow conditions are observed to strongly influence the buoyant river plume, as predicted by the "small-scale" or "narrow" dynamical classification using Garvine's (1995) system. Because of the transient eddies and the location of the river mouth on the headland, flow immediately offshore of the river mouth is directed eastward twice as frequently as it is westward. This results in a buoyant plume that is much more frequently "bent over" toward the east than the west. During bent over plume conditions, the plume was attached to the eastern shoreline while having a distinct, cuspate front along its westernmost boundary. The location of the front was found to be related to the magnitude and direction of local flow during the preceding O(1. h), and increases in alongshore flow resulted in deeper freshwater mixing, stronger baroclinic anomalies, and stronger hugging of the coast. During bent over plume conditions, we observed significant convergence of river plume water toward the frontal boundary within 1. km of the river mouth. These results show how coastal topography can strongly influence buoyant plume behavior, and they should assist with understanding of initial coastal sediment dispersal pathways from the Elwha River during a pending dam removal project. ?? 2010.

  15. Marine bird aggregations associated with the tidally-driven plume and plume fronts of the Columbia River

    NASA Astrophysics Data System (ADS)

    Zamon, Jeannette E.; Phillips, Elizabeth M.; Guy, Troy J.

    2014-09-01

    Freshwater discharge from large rivers into the coastal ocean creates tidally-driven frontal systems known to enhance mixing, primary production, and secondary production. Many authors suggest that tidal plume fronts increase energy flow to fish-eating predators by attracting planktivorous fishes to feed on plankton aggregated by the fronts. However, few studies of plume fronts directly examine piscivorous predator response to plume fronts. Our work examined densities of piscivorous seabirds relative to the plume region and plume fronts of the Columbia River, USA. Common murres (Uria aalge) and sooty shearwaters (Puffinus griseus) composed 83% of all birds detected on mesoscale surveys of the Washington and Oregon coasts (June 2003-2006), and 91.3% of all birds detected on fine scale surveys of the plume region less than 40 km from the river mouth (May 2003 and 2006). Mesoscale comparisons showed consistently more predators in the central plume area compared to the surrounding marine area (murres: 10.1-21.5 vs. 3.4-8.2 birds km-2; shearwaters: 24.2-75.1 vs. 11.8-25.9 birds km-2). Fine scale comparisons showed that murre density in 2003 and shearwater density in both 2003 and 2006 were significantly elevated in the tidal plume region composed of the most recently discharged river water. Murres tended to be more abundant on the north face of the plume. In May 2003, more murres and shearwaters were found within 3 km of the front on any given transect, although maximum bird density was not necessarily found in the same location as the front itself. Predator density on a given transect was not correlated with frontal strength in either year. The high bird densities we observed associated with the tidal plume demonstrate that the turbid Columbia River plume does not necessarily provide fish with refuge from visual predators. Bird predation in the plume region may therefore impact early marine survival of Pacific salmon (Oncorhynchus spp.), which must migrate through the

  16. Swirling plumes and spinning tops

    NASA Astrophysics Data System (ADS)

    Frank, Daria; Landel, Julien; Dalziel, Stuart; Linden, Paul

    2017-11-01

    Motivated by potential effects of the Earth's rotation on the dynamics of the oil plume resulting from the Deepwater Horizon disaster in 2010, we conducted laboratory experiments on saltwater and bubble axisymmetric point plumes in a homogeneous rotating environment. The effect of rotation is conventionally characterized by a Rossby number, based on the source buoyancy flux, the rotation rate of the system and the total water depth and which ranged from 0.02 to 1.3 in our experiments. In the range of parameters studied, we report a striking new physical instability in the plume dynamics near the source. After approximately one rotation period, the plume axis tilts away laterally from the centreline and the plume starts to precess in the anticyclonic direction. We find that the mean precession frequency of the plume scales linearly with the rotation rate of the environment. Surprisingly, the precession frequency is found to be independent of the diameter of the plume nozzle, the source buoyancy flux, the water depth and the geometry of the domain. In this talk, we present our experimental results and develop simple theoretical toy models to explain the observed plume behaviour.

  17. Ridge jumps associated with plume-ridge interaction: Mantle plume-lithosphere interaction and hotspot magmatism

    NASA Astrophysics Data System (ADS)

    Mittelstaedt, E.; Ito, G.

    2007-12-01

    Interaction of mantle plumes and young lithosphere near mid-ocean ridges can lead to changes in spreading geometry by shifts of the ridge-axis toward the plume as seen at various hotspots, notably Iceland and the Galapagos. Previous work has shown that, with a sufficient magma flux, heating of the lithosphere by magmatism can significantly weaken the plate and, in some cases, could cause ridge jumps. Upwelling hot asthenosphere can also weaken the plate through thermal and mechanical thinning of the lithosphere. Using the finite element code CITCOM, we solve the equations of continuity, momentum and energy to examine deformation in near-ridge lithosphere associated with relatively hot upwelling asthenosphere and seafloor spreading. The mantle and lithosphere obey a non-Newtonian viscous rheology with plastic failure in the cold part of the lithosphere simulated by imposing an effective yield stress. Temperatures of the lithospheric thermal boundary region are initially given a square-root of age thermal profile while a hot patch is placed at the bottom to initiate a mantle-plume like upwelling. The effect of upwelling asthenosphere on ridge jumps is evaluated by varying three parameters: the plume excess temperature, the spreading rate and the distance of the plume from the ridge axis. Preliminary results show plume related thinning and weakening of the lithosphere over a wide area (100's of km's) with the rate of thinning increasing with the excess temperature of the plume. Initially, thinning occurs as the plume approaches the lithosphere and asthenospheric material is forced out of the way. As the plume material comes into contact with the lithosphere, thinning occurs through heating and mechanical removal of the thermal boundary layer. Thinning of the lithosphere is one of the primary factors in achieving a ridge jump. Another is large tensile stresses which can facilitate the initiation of rifting at this weakened location. Model stresses induced by the

  18. Toward a comprehensive UV laser ablation modeling of multicomponent materials—A non-equilibrium investigation on titanium carbide

    NASA Astrophysics Data System (ADS)

    Ait Oumeziane, Amina; Parisse, Jean-Denis

    2018-05-01

    Titanium carbide (TiC) coatings of great quality can be produced using nanosecond pulsed laser deposition (PLD). Because the deposition rate and the transfer of the target stoichiometry depend strongly on the laser-target/laser-plasma interaction as well as the composition of the laser induced plume, investigating the ruling fundamental mechanisms behind the material ablation and the plasma evolution in the background environment under PLD conditions is essential. This work, which extends previous investigations dedicated to the study of nanosecond laser ablation of pure target materials, is a first step toward a comprehensive non-equilibrium model of multicomponent ones. A laser-material interaction model coupled to a laser-plasma interaction one is presented. A UV 20 ns KrF (248 nm) laser pulse is considered. Ablation depths, plasma ignition thresholds, and shielding rates have been calculated for a wide range of laser beam fluences. A comparison of TiC behavior with pure titanium material under the same conditions is made. Plasma characteristics such as temperature and composition have been investigated. An overall correlation between the various results is presented.

  19. African Equatorial and Subtropical Ozone Plumes: Recurrences Timescales of the Brown Cloud Trans-African Plumes and Other Plumes

    NASA Technical Reports Server (NTRS)

    Chatfield, Robert B.; Thompson, Anne M.; Guan, Hong; Witte, Jacquelyn C.

    2004-01-01

    We have found repeated illustrations in the maps of Total Tropospheric Ozone (TTO) of apparent transport of ozone from the Indian Ocean to the Equatorial Atlantic Ocean. Most interesting are examples that coincide with the INDOEX observations of late northern winter, 1999. Three soundings associated with the SHADOZ (Southern Hemisphere Additional Ozonesondes) network help confirm and quantify degree of influence of pollution, lightning, and stratospheric sources, suggesting that perhaps 40% of increased Atlantic ozone could be Asian pollution during periods of maximum identified in the TTO maps. We outline recurrent periods of apparent ozone transport from Indian to Atlantic Ocean regions both during and outside the late-winter period. These are placed in the context of some general observations about factors controlling recurrence timescales for the expression of both equatorial and subtropical plumes. Low-level subtropical plumes are often controlled by frontal systems approaching the Namib coast; these direct mid-level air into either easterly equatorial plumes or westerly mid- troposphere plumes. Equatorial plumes of ozone cross Africa on an easterly path due to the occasional coincidence of two phenomena: (1) lofting of ozone to mid and upper levels, often in the Western Indian Ocean, and (2) the eastward extension of an Equatorial African easterly jet.

  20. Oxide or carbide nanoparticles synthesized by laser ablation of a bulk Hf target in liquids and their structural, optical, and dielectric properties

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

    Semaltianos, N. G., E-mail: nsemaltianos@yahoo.com; Friedt, J.-M.; Blondeau-Patissier, V.

    2016-05-28

    Laser ablation of a bulk Hf target in deionized (DI) water, ethanol, or toluene was carried out for the production of nanoparticles' colloidal solutions. Due to the interaction of the ablation plasma plume species with the species which are produced by the liquid decomposition at the plume-liquid interface, hafnia (HfO{sub 2}) nanoparticles are synthesized in DI water, hafnium carbide (HfC) nanoparticles in toluene, and a mixture of these in ethanol. The hafnia nanoparticles are in the monoclinic low temperature phase and in the tetragonal and fcc high temperature phases. Their size distribution follows log-normal function with a median diameter inmore » the range of 4.3–5.3 nm. Nanoparticles synthesized in DI water have band gaps of 5.6 and 5.4 eV, in ethanol 5.72 and 5.65 eV (using low and high pulse energy), and in toluene 3 eV. The values for the relative permittivity in the range of 7.74–8.90 were measured for hafnia nanoparticles' thin films deposited on substrates by drop-casting (self-assembled layers) in parallel plate capacitor structures.« less

  1. Key stages of material expansion in dielectrics upon femtosecond laser ablation revealed by double-color illumination time-resolved microscopy

    NASA Astrophysics Data System (ADS)

    Garcia-Lechuga, Mario; Solis, Javier; Siegel, Jan

    2018-03-01

    The physical origin of material removal in dielectrics upon femtosecond laser pulse irradiation (800 nm, 120 fs pulse duration) has been investigated at fluences slightly above ablation threshold. Making use of a versatile pump-probe microscopy setup, the dynamics and different key stages of the ablation process in lithium niobate have been monitored. The use of two different illumination wavelengths, 400 and 800 nm, and a rigorous image analysis combined with theoretical modelling, enables drawing a clear picture of the material excitation and expansion stages. Immediately after excitation, a dense electron plasma is generated. Few picoseconds later, direct evidence of a rarefaction wave propagating into the bulk is obtained, with an estimated speed of 3650 m/s. This process marks the onset of material expansion, which is confirmed by the appearance of transient Newton rings, which dynamically change during the expansion up to approximately 1 ns. Exploring delays up to 15 ns, a second dynamic Newton ring pattern is observed, consistent with the formation of a second ablation front propagating five times slower than the first one.

  2. Ablation article and method

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

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

  3. The 2016 Case for Mantle Plumes and a Plume-Fed Asthenosphere (Augustus Love Medal Lecture)

    NASA Astrophysics Data System (ADS)

    Morgan, Jason P.

    2016-04-01

    The process of science always returns to weighing evidence and arguments for and against a given hypothesis. As hypotheses can only be falsified, never universally proved, doubt and skepticism remain essential elements of the scientific method. In the past decade, even the hypothesis that mantle plumes exist as upwelling currents in the convecting mantle has been subject to intense scrutiny; from geochemists and geochronologists concerned that idealized plume models could not fit many details of their observations, and from seismologists concerned that mantle plumes can sometimes not be 'seen' in their increasingly high-resolution tomographic images of the mantle. In the place of mantle plumes, various locally specific and largely non-predictive hypotheses have been proposed to explain the origins of non-plate boundary volcanism at Hawaii, Samoa, etc. In my opinion, this debate has now passed from what was initially an extremely useful restorative from simply 'believing' in the idealized conventional mantle plume/hotspot scenario to becoming an active impediment to our community's ability to better understand the dynamics of the solid Earth. Having no working hypothesis at all is usually worse for making progress than having an imperfect and incomplete but partially correct one. There continues to be strong arguments and strong emerging evidence for deep mantle plumes. Furthermore, deep thermal plumes should exist in a mantle that is heated at its base, and the existence of Earth's (convective) geodynamo clearly indicates that heat flows from the core to heat the mantle's base. Here I review recent seismic evidence by French, Romanowicz, and coworkers that I feel lends strong new observational support for the existence of deep mantle plumes. I also review recent evidence consistent with the idea that secular core cooling replenishes half the mantle's heat loss through its top surface, e.g. that the present-day mantle is strongly bottom heated. Causes for

  4. Ablative Rayleigh-Taylor and Richtmyer-Meshkov Instabilities in Laser-Accelerated Colliding Foils

    NASA Astrophysics Data System (ADS)

    Aglitskiy, Y.; Metzler, N.; Karasik, M.; Serlin, V.; Weaver, J.; Obenschain, S. P.; Oh, J.; Schmitt, A. J.; Velikovich, A. L.; Zalesak, S. T.; Gardner, J. H.; Harding, E. C.

    2008-11-01

    In our experiments done on the Nike KrF laser, we study instability growth at shock-decelerated interfaces in planar colliding-foil experiments. We use streaked monochromatic (1.86 keV) x-ray face-on imaging diagnostics to measure the areal mass modulation growth caused by the instability. Higher x-ray energies up to 5.25 keV are used to follow the shock propagation as well as the 1D dynamics of the collision. While a laser-driven foil is accelerated towards the stationary low-density foam layer, an ablative RT instability develops. Having reached a high velocity, the foil hits the foam layer. The impact generates strong shocks in the plastic and in the foam. The reflected shock wave re-shocks the ablation front, its acceleration stops, and so does the observed RT growth. This is followed by areal mass oscillations due to the ablative RM instability and feedout mechanisms, of which the latter dominates.

  5. A Brilliant Plume

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The Long Range Reconnaissance Imager (LORRI) on New Horizons captured another dramatic picture of Jupiter's moon Io and its volcanic plumes, 19 hours after the spacecraft's closest approach to Jupiter on Feb. 28, 2007. LORRI took this 75 millisecond exposure at 0035 Universal Time on March 1, 2007, when Io was 2.3 million kilometers (1.4 million miles) from the spacecraft.

    Io's dayside is deliberately overexposed to bring out faint details in the plumes and on the moon's night side. The continuing eruption of the volcano Tvashtar, at the 1 o'clock position, produces an enormous plume roughly 330 kilometers (200 miles) high, which is illuminated both by sunlight and 'Jupiter light.'

    The shadow of Io, cast by the Sun, slices across the plume. The plume is quite asymmetrical and has a complicated wispy texture, for reasons that are still mysterious. At the heart of the eruption incandescent lava, seen here as a brilliant point of light, is reminding scientists of the fire fountains spotted by the Galileo Jupiter orbiter at Tvashtar in 1999.

    The sunlit plume faintly illuminates the surface underneath. 'New Horizons and Io continue to astonish us with these unprecedented views of the solar system's most geologically active body' says John Spencer, deputy leader of the New Horizons Jupiter Encounter Science Team and an Io expert from Southwest Research Institute.

    Because this image shows the side of Io that faces away from Jupiter, the large planet does not illuminate the moon's night side except for an extremely thin crescent outlining the edge of the disk at lower right. Another plume, likely from the volcano Masubi, is illuminated by Jupiter just above this lower right edge. A third and much fainter plume, barely visible at the 2 o'clock position, could be the first plume seen from the volcano Zal Patera.

    As in other New Horizons images of Io, mountains catch the setting Sun just beyond the terminator (the line dividing day and night

  6. Life Cycle of Mantle Plumes: A perspective from the Galapagos Plume (Invited)

    NASA Astrophysics Data System (ADS)

    Gazel, E.; Herzberg, C. T.

    2009-12-01

    Hotspots are localized sources of heat and magmatism considered as modern-day evidence of mantle plumes. Some hotspots are related to massive magmatic production that generated Large Igneous Provinces (LIPS), an initial-peak phase of plume activity with a mantle source hotter and more magmatically productive than present-day hotspots. Geological mapping and geochronological studies have shown much lower eruption rates for OIB compared to lavas from Large Igneous Provinces LIPS such as oceanic plateaus and continental flood provinces. Our study is the first quantitative petrological comparison of mantle source temperatures and extent of melting for OIB and LIP sources. The wide range of primary magma compositions and inferred mantle potential temperatures for each LIP and OIB occurrence suggest that this rocks originated form a hotspot, a spatially localized source of heat and magmatism restricted in time. Extensive outcrops of basalt, picrite, and sometimes komatiite with circa 65-95 Ma ages occupy portions of the pacific shore of Central and South America included in the Caribbean Large Igneous Province (CLIP). There is general consensus of a Pacific-origin of CLIP and most studies suggest that it was produced by melting in the Galapagos mantle plume. The Galapagos connection is consistent with isotopic and geochemical similarities with lavas from the present-day Galapagos hotspot. A Galapagos link for rocks in South American oceanic complexes (eg. the island of Gorgona) is more controversial and requires future work. The MgO and FeO contents of lavas from the Galapagos related lavas and their primary magmas have decreased since the Cretaceous. From petrological modeling we infer that these changes reflect a cooling of the Galapagos mantle plume from a potential temperature of 1560-1620 C in the Cretaceous to 1500 C at the present time. These temperatures are higher than 1350 C for ambient mantle associated with oceanic ridges, and provide support for the mantle

  7. Impact of radiofrequency ablation geometry on electrical conduction

    NASA Astrophysics Data System (ADS)

    Rivas, Rhiana N.; Lye, Theresa H.; Hendon, Christine P.

    2018-02-01

    The gold standard of current treatment for atrial fibrillation is radiofrequency ablation (RFA). Single RFA procedures have low long-term, single-procedure success rates, which can be attributed to factors including inability to measure and visualize lesion depth in real time and incomplete knowledge of how atrial fibrillation manifests and persists. One way to address this problem is to develop a heart model that accurately fits lesion dimensions and depth using OCT to extract structural information. Twenty-three lesions of varying transmurality in left and right swine atrial tissue have been imaged with a Thorlabs OCT system with 6.5-micron axial resolution and a custom Ultra High Resolution system with 2.5-micron axial resolution. The boundaries of the ablation lesions were identified by the appearance of the birefringence artifact to identify areas of un-ablated tissue, as well as by changes to depth penetration and structural features, including decreased contrast between the endocardium and myocardium and disappearance of collagen fibers within the ablation lesion. Using these features, the lateral positions of the lesion boundaries were identified. An algorithm that fit ellipses to the lesion contours modeled the ablation geometry in depth. Lesion dimensions and shape were confirmed by comparison with trichrome histological processing. Finite-element models were fitted with these parameters and electrophysiological simulations were run with the Continuity 6 package. Next steps include correlating lesion geometry to conduction velocity, and including further tissue complexity such as varying tissue composition and fiber orientation. Additional models of linear lesions with gaps and adjacent lesions created with non-perpendicular contact will be created. This work will provide insight into how lesion geometry, tissue composition, and fiber organization impact electrophysiological propagation.

  8. Modeling and Simulation of Ablation-Controlled Plasmas

    NASA Astrophysics Data System (ADS)

    Kundrapu, Madhusudhan N.

    Ablation and plasma formation in high energy laser target interactions and arc discharges are studied numerically. Each of the two processes is modeled separately due to the type of energy source and the resulting flow eld. Ablation of the target material and plasma formation are coupled to obtain evaporation rate, temperature distribution, velocity eld, and species concentration self-consistently. Laser ablation is studied in the perspective of directed energy applications, where beam size varies from few centimeters to tens of centimeters with energies extending up to 10 kW/cm2. Because of this high energy deposition, the evaporated material expands to supersonic speeds into the free space. Due to the large spot sizes and associated supersonic flow, one dimensional Euler equations are considered to be sufficient for modeling the plume. Instead, more emphasis was given to evaporation model, by introducing Knudsen layer kinetics at the plume target interface, and plasma shielding. The evaporation rate is validated with results from the experiments and simulations are carried out to nd the in fluence of laser beam frequency on evaporation rates. The evaporation model used in this work is found to be more accurate than the widely used model based on sonic speed assumption. The optimum beam wavelength for Al surfaces is found to be 850 nm. Attenuation of telemetry data by plasma is a concern for the testing of directed energy systems. Electrostatic approach for the mitigation of communication attenuation is analyzed to obtain the fluency limits up to which the approach can be implemented. It is found from sheath calculations that uninterrupted telemetry can be achieved through Al plasma for fluences below 4 J/cm2 at a background pressure of 1 atm, using a maximum bias voltage of 10 kV . Arc discharge ablation is modeled for the synthesis of nanoparticles. The electric arc generated between the electrodes, placed inside a Helium chamber, evaporates the catalyst

  9. Mass Median Plume Angle: A novel approach to characterize plume geometry in solution based pMDIs.

    PubMed

    Moraga-Espinoza, Daniel; Eshaghian, Eli; Smyth, Hugh D C

    2018-05-30

    High-speed laser imaging (HSLI) is the preferred technique to characterize the geometry of the plume in pressurized metered dose inhalers (pMDIs). However, current methods do not allow for simulation of inhalation airflow and do not use drug mass quantification to determine plume angles. To address these limitations, a Plume Induction Port Evaluator (PIPE) was designed to characterize the plume geometry based on mass deposition patterns. The method is easily adaptable to current pMDI characterization methodologies, uses similar calculations methods, and can be used under airflow. The effect of airflow and formulation on the plume geometry were evaluated using PIPE and HSLI. Deposition patterns in PIPE were highly reproducible and log-normal distributed. Mass Median Plume Angle (MMPA) was a new characterization parameter to describe the effective angle of the droplets deposited in the induction port. Plume angles determined by mass showed a significant decrease in size as ethanol increases which correlates to the decrease on vapor pressure in the formulation. Additionally, airflow significantly decreased the angle of the plumes when cascade impactor was operated under flow. PIPE is an alternative to laser-based characterization methods to evaluate the plume angle of pMDIs based on reliable drug quantification while simulating patient inhalation. Copyright © 2018. Published by Elsevier B.V.

  10. Scaling for turbulent viscosity of buoyant plumes in stratified fluids: PIV measurement with implications for submarine hydrothermal plume turbulence

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; He, Zhiguo; Jiang, Houshuo

    2017-11-01

    Time-resolved particle image velocimetry (PIV) has been used to measure instantaneous two-dimensional velocity vector fields of laboratory-generated turbulent buoyant plumes in linearly stratified saltwater over extended periods of time. From PIV-measured time-series flow data, characteristics of plume mean flow and turbulence have been quantified. To be specific, maximum plume penetration scaling and entrainment coefficient determined from the mean flow agree well with the theory based on the entrainment hypothesis for buoyant plumes in stratified fluids. Besides the well-known persistent entrainment along the plume stem (i.e., the 'plume-stem' entrainment), the mean plume velocity field shows persistent entrainment along the outer edge of the plume cap (i.e., the 'plume-cap' entrainment), thereby confirming predictions from previous numerical simulation studies. To our knowledge, the present PIV investigation provides the first measured flow field data in the plume cap region. As to measured plume turbulence, both the turbulent kinetic energy field and the turbulence dissipation rate field attain their maximum close to the source, while the turbulent viscosity field reaches its maximum within the plume cap region; the results also show that maximum turbulent viscosity scales as νt,max = 0.030(B/N)1/2, where B is source buoyancy flux and N is ambient buoyancy frequency. These PIV data combined with previously published numerical simulation results have implications for understanding the roles of hydrothermal plume turbulence, i.e. plume turbulence within the cap region causes the 'plume-cap' entrainment that plays an equally important role as the 'plume-stem' entrainment in supplying the final volume flux at the plume spreading level.

  11. Monitoring the formation of inorganic fullerene-like MoS2 nanostructures by laser ablation in liquid environments

    NASA Astrophysics Data System (ADS)

    Compagnini, Giuseppe; Sinatra, Marco G.; Messina, Gabriele C.; Patanè, Giacomo; Scalese, Silvia; Puglisi, Orazio

    2012-05-01

    Laser ablation of solid targets in liquid media is emerging as a simple, clean and reproducible way to generate a large number of intriguing nanometric structures with peculiar properties. In this work we present some results on the formation of MoS2 fullerene-like nanoparticles (10-15 nm diameter) obtained by the ablation of crystalline targets in water. Such a top-down approach can be considered greener than standard sulphidization reactions and represents an intriguing single step procedure. The generation of the MoS2 nanostructures is in competition with that of oxide clusters and strongly depends on the oxidative environment created by the plasma plume. The size, shape and crystalline phase of the obtained nanoparticles are studied by microscopy while X-Ray Photoelectron Spectroscopy is used to investigate the chemical state of produced nanostructures and to propose mechanisms for their growth.

  12. The planet beyond the plume hypothesis

    NASA Astrophysics Data System (ADS)

    Smith, Alan D.; Lewis, Charles

    1999-12-01

    but not counterflow, though convergent margin geometry may still induce propagating fractures which set up melting anomalies. Lateral migration of asthenospheric domains allows the sources of Pacific intraplate volcanism to be traced back to continental mantle eroded during the breakup of Gondwana and the amalgamation of Asia in the Paleozoic. Intraplate volcanism in the South Pacific therefore has a common Gondwanan origin to intraplate volcanism in the South Atlantic and Indian Oceans, hence the DUPAL anomaly is entirely of shallow origin. Such domains constitute a second order geochemical heterogeneity superimposed on a streaky/marble-cake structure arising from remixing of subducted crust with the convecting mantle. During the Proterozoic and Phanerozoic, remixing of slabs has buffered the evolution of the depleted mantle to a rate of 2.2 ɛNd units Ga -1, with fractionation of Lu from Hf in the sediment component imparting the large range in 176Hf/ 177Hf relative to 143Nd/ 144Nd observed in MORB. Only the high ɛNd values of some Archean komatiites are compatible with derivation from unbuffered mantle. The existence of a very depleted reservoir is attributed to stabilisation of a large early continental crust through either obduction tectonics or slab melting regimes which reduced the efficiency of crustal recycling back into the mantle. Generation of komatiite is therefore a consequence of mantle composition, and is permitted in ocean ridge environments and/or under hydrous melting conditions. Correspondingly, as intraplate volcanism depends on survival of volatile-bearing sources, its appearance in the Middle Proterozoic corresponds to the time in the Earth's thermal evolution at which minerals such as phlogopite and amphibole could survive in off-ridge environments in the shallow asthenosphere. The geodynamic evolution of the Earth was thus determined at convergent margins, not by plumes and hotspots, with the decline in thermal regime causing both a reduction

  13. Sonic and Supersonic Jet Plumes

    NASA Technical Reports Server (NTRS)

    Venkatapathy, E.; Naughton, J. W.; Flethcher, D. G.; Edwards, Thomas A. (Technical Monitor)

    1994-01-01

    Study of sonic and supersonic jet plumes are relevant to understanding such phenomenon as jet-noise, plume signatures, and rocket base-heating and radiation. Jet plumes are simple to simulate and yet, have complex flow structures such as Mach disks, triple points, shear-layers, barrel shocks, shock- shear- layer interaction, etc. Experimental and computational simulation of sonic and supersonic jet plumes have been performed for under- and over-expanded, axisymmetric plume conditions. The computational simulation compare very well with the experimental observations of schlieren pictures. Experimental data such as temperature measurements with hot-wire probes are yet to be measured and will be compared with computed values. Extensive analysis of the computational simulations presents a clear picture of how the complex flow structure develops and the conditions under which self-similar flow structures evolve. From the computations, the plume structure can be further classified into many sub-groups. In the proposed paper, detail results from the experimental and computational simulations for single, axisymmetric, under- and over-expanded, sonic and supersonic plumes will be compared and the fluid dynamic aspects of flow structures will be discussed.

  14. A novel method for fabrication of size-controlled metallic nanoparticles by laser ablation

    NASA Astrophysics Data System (ADS)

    Choudhury, Kaushik; Singh, R. K.; Ranjan, Mukesh; Kumar, Ajai; Srivastava, Atul

    2017-12-01

    Time resolved experimental investigation of laser produced plasma-induced shockwaves has been carried out in the presence of confining walls placed along the lateral directions using a Mach Zehnder interferometer in air ambient. Copper was used as target material. The primary and the reflected shock waves and their effects on the evolution of medium density and the plasma density have been studied. The reflected shock wave has been seen to be affecting the shape and density of the plasma plume in the confined geometry. The same experiments were performed with water and isopropyl alcohol as the ambient liquids and the produced nanoparticles were characterised for size and size distribution. Significant differences in the size and size distribution are seen in case of the nanoparticles produced from the ablation of the targets with and without confining boundary. The observed trend has been attributed to the presence of confining boundary and the way it affects the thermalisation time of the plasma plume. The experiments also show the effect of medium density on the mean size of the copper nanoparticles produced.

  15. The Time Variability of Individual Geysers in the Plume of Enceladus

    NASA Astrophysics Data System (ADS)

    Trumbo, S. K.; Ewald, S. P.; Ingersoll, A. P.

    2016-12-01

    Porco et al. (2014) [1] published the locations of 100 jets along the so-called "tiger stripes" that feed the massive plume of Enceladus. Hedman et al. (2013) [2] observed fluctuations in integrated plume brightness in response to periodic tidal forcing on the orbital timescale of Enceladus, in which the plume is brightest near apocenter and dimmest near pericenter. The thin crack models of Hurford et al. (2007, 2012) [3, 4] suggest that individual jets should respond to the same forces on similar timescales. However, if the jets are produced via vapor and liquid propagation through thin subterranean cracks, then they may also be controlled thermodynamically and dependent on the timescale of ice buildup on the conduit walls. Ingersoll and Ewald (2016) [5] demonstrate that the plume also varies on decadal timescales, perhaps as a result of an eleven-year tide or long-term ice accumulation within source cracks. We examine Cassini ISS Narrow Angle Camera images spanning 2005 - 2012 in order to assess the temporal variability of individual geysers and regional emission in the plume. We observe both the appearance and disappearance of individual jets, as well as visible changes in regional emission. Our observations suggest localized variations on timescales of months to years that are not easily tied to mean anomaly, but that may be indicative of subsurface processes. Theoretical models of the geyser mechanisms and subsurface plumbing predict closure timescales of individual cracks that are dependent on model parameters, such as crack width, crack tortuosity, and water table depth [6, 7, 8]. Thus, we discuss possible implications of these observations for both the mechanism and anatomy of an Enceladus geyser. [1] Porco et al. (2014), AJ, 148, 3. [2] Hedman et al. (2013), Nature, 500, 182 - 184. [3] Hurford et al. (2007), Nature, 447, 292 - 294. [4] Hurford et al. (2012), Icarus, 220, 896 - 903. [5] Ingersoll and Ewald (2016), Icarus, in review. [6] Ingersoll and

  16. Atmospheric chemistry in volcanic plumes.

    PubMed

    von Glasow, Roland

    2010-04-13

    Recent field observations have shown that the atmospheric plumes of quiescently degassing volcanoes are chemically very active, pointing to the role of chemical cycles involving halogen species and heterogeneous reactions on aerosol particles that have previously been unexplored for this type of volcanic plumes. Key features of these measurements can be reproduced by numerical models such as the one employed in this study. The model shows sustained high levels of reactive bromine in the plume, leading to extensive ozone destruction, that, depending on plume dispersal, can be maintained for several days. The very high concentrations of sulfur dioxide in the volcanic plume reduces the lifetime of the OH radical drastically, so that it is virtually absent in the volcanic plume. This would imply an increased lifetime of methane in volcanic plumes, unless reactive chlorine chemistry in the plume is strong enough to offset the lack of OH chemistry. A further effect of bromine chemistry in addition to ozone destruction shown by the model studies presented here, is the oxidation of mercury. This relates to mercury that has been coemitted with bromine from the volcano but also to background atmospheric mercury. The rapid oxidation of mercury implies a drastically reduced atmospheric lifetime of mercury so that the contribution of volcanic mercury to the atmospheric background might be less than previously thought. However, the implications, especially health and environmental effects due to deposition, might be substantial and warrant further studies, especially field measurements to test this hypothesis.

  17. Interannual variability of Danube waters propagation in summer period of 1992-2015 and its influence on the Black Sea ecosystem

    NASA Astrophysics Data System (ADS)

    Kubryakov, A. A.; Stanichny, S. V.; Zatsepin, A. G.

    2018-03-01

    The propagation of the Danube River plume has strong interannual variability that impacts the local balance of nutrients and the thermohaline structure in the western Black Sea. In the present study, we use a particle-tracking model based on satellite altimetry measurements and wind reanalysis data, as well as satellite measurements (SeaWiFS, MODIS), to investigate the interannual variability in the Danube plume pathways during the summer from 1993 to 2015. The wind conditions largely define the variability in the Danube water propagation. Relatively low-frequency variability (on periods of a week to months) in the wind stress curl modulates the intensity of the geostrophic Rim Current and related mesoscale eddy dynamics. High-frequency offshore wind-drift currents transport the plume across isobaths and provide an important transport link between shelf and offshore circulation. Inherent plume dynamics play an additional role in the near-mouth transport of the plume and its connection with offshore circulation. During the years with prevailing northeast winds ( 30% of studied cases), which are usually accompanied by increased wind curl over the Black Sea and higher Danube discharge, an alongshore southward current at the NorthWestern Shelf (NWS) is formed near the western Black Sea coast. Advected southward, the Danube waters are entrained in the Rim Current jet, which transports them along the west coast of the basin. The strong Rim Current, fewer eddies and downwelling winds substantially decrease the cross-shelf exchange of nutrients. During the years with prevailing southeastern winds ( 40%), the Rim Current is less intense. Mesoscale eddies effectively trap the Danube waters, transporting them to the deep western part of the basin. The low- and high-frequency southeastern wind-drift currents contribute significantly to cross-isobath plume transport and its connection with offshore circulation. During several years ( 15%), the Danube waters moved eastward to

  18. Modeling absolute plate and plume motions

    NASA Astrophysics Data System (ADS)

    Bodinier, G. P.; Wessel, P.; Conrad, C. P.

    2016-12-01

    Paleomagnetic evidence for plume drift has made modeling of absolute plate motions challenging, especially since direct observations of plume drift are lacking. Predictions of plume drift arising from mantle convection models and broadly satisfying observed paleolatitudes have so far provided the only framework for deriving absolute plate motions over moving hotspots. However, uncertainties in mantle rheology, temperature, and initial conditions make such models nonunique. Using simulated and real data, we will show that age progressions along Pacific hotspot trails provide strong constraints on plume motions for all major trails, and furthermore that it is possible to derive models for relative plume drift from these data alone. Relative plume drift depends on the inter-hotspot distances derived from age progressions but lacks a fixed reference point and orientation. By incorporating paleolatitude histories for the Hawaii and Louisville chains we add further constraints on allowable plume motions, yet one unknown parameter remains: a longitude shift that applies equally to all plumes. To obtain a solution we could restrict either the Hawaii or Louisville plume to have latitudinal motion only, thus satisfying paleolatitude constraints. Yet, restricting one plume to latitudinal motion while all others move freely is not realistic. Consequently, it is only possible to resolve the motion of hotspots relative to an overall and unknown longitudinal shift as a function of time. Our plate motions are therefore dependent on the same shift via an unknown rotation about the north pole. Yet, as plume drifts are consequences of mantle convection, our results place strong constraints on the pattern of convection. Other considerations, such as imposed limits on plate speed, plume speed, proximity to LLSVP edges, model smoothness, or relative plate motions via ridge-spotting may add further constraints that allow a unique model of Pacific absolute plate and plume motions to be

  19. Constraining the Enceladus Plume and Understanding Its Physics via Numerical Simulation from Underground Source to Infinity

    NASA Astrophysics Data System (ADS)

    Yeoh, S. K.; Li, Z.; Goldstein, D. B.; Varghese, P. L.; Trafton, L. M.; Levin, D. A.

    2014-12-01

    The Enceladus ice/vapor plume not only accounts for the various features observed in the Saturnian system, such as the E-ring, the narrow neutral H2O torus, and Enceladus' own bright albedo, but also raises exciting new possibilities, including the existence of liquid water on Enceladus. Therefore, understanding the plume and its physics is important. Here we assume that the plume arises from flow expansion within multiple narrow subsurface cracks connected to reservoirs of liquid water underground, and simulate this expanding flow from the underground reservoir out to several Enceladus radii where Cassini data are available for comparison. The direct simulation Monte Carlo (DSMC) method is used to simulate the subsurface and near-field collisional regions and a free-molecular model is used to propagate the plume out into the far-field. We include the following physical processes in our simulations: the flow interaction with the crack walls, grain condensation from the vapor phase, non-equilibrium effects (e.g. freezing of molecular internal energy modes), the interaction between the vapor and the ice grains, the gravitational fields of Enceladus and Saturn, and Coriolis and centrifugal forces (due to motion in non-inertial reference frame). The end result is a plume model that includes the relevant physics of the flow from the underground source out to where Cassini measurements are taken. We have made certain assumptions about the channel geometry and reservoir conditions. The model is constrained using various available Cassini data (particularly those of INMS, CDA and UVIS) to understand the plume physics as well as estimate the vapor and grain production rates and its temporal variability.

  20. Nonequilibrium Ablation of Phenolic Impregnated Carbon Ablator

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  1. Modeling and observations of ULF waves trapped in a plasmaspheric density plume

    NASA Astrophysics Data System (ADS)

    Degeling, A. W.; Zhang, S.; Foster, J. C.; Shi, Q.; Zong, Q. G.; Rankin, R.

    2017-12-01

    In order for ULF waves to effectively energise radiation belt electrons by drift-resonance, wave power must be significant in regions within the magnetosphere where the ULF wave phase propagation and electron drift directions are roughly aligned. For waves launched along the dayside magnetopause, such a region would be located in the afternoon - dusk sector of the inner magnetosphere. During periods of storm activity and enhanced convection, the plasma density in this region is highly dynamic due to the development of plasmaspheric drainage plume (PDP) structure. This significantly affects the local Alfvén speed, and alters the propagation of ULF waves launched from the magnetopause. It can therefore be expected that the accessibility of ULF wave power for radiation belt energisation is sensitively dependent on the recent history of magnetospheric convection, and the stage of development of the PDP. This is investigated using a 3D model for ULF waves within the magnetosphere in which the plasma density distribution is evolved using an advection model for cold plasma, driven by a (Volland - Stern) convection electrostatic field (resulting in PDP structure). The wave model includes magnetic-field day/night asymmetry, and extends to a paraboloid dayside magnetopause, from which ULF waves are launched at various stages during the PDP development. We find that the plume structure significantly alters the field line resonance (FLR) location, and the turning point for MHD fast waves, introducing strong asymmetry in the ULF wave distribution across the noon meridian. Moreover, the density enhancement within the PDP creates a waveguide or local cavity for MHD fast waves, such that eigenmodes formed allow the penetration of ULF wave power to much lower L within the plume than outside. This may explain satellite observations of the appearance of ULF wave activity within localized density enhancements associated with a PDP. Such an example, made by THEMIS following a

  2. Deposition of high quality YBa2Cu3O(7-delta) thin films over large areas by pulsed laser ablation with substrate scanning

    NASA Technical Reports Server (NTRS)

    Davis, M. F.; Wosik, J.; Forster, K.; Deshmukh, S. C.; Rampersad, H. R.

    1991-01-01

    The paper describes thin films deposited in a system where substrates are scanned over areas up to 3.5 x 3.5 cm through the stationary plume of an ablated material defined by an aperture. These YBCO films are deposited on LaAlO3 and SrTiO3 substrates with the thickness of 90 and 160 nm. Attention is focused on the main features of the deposition system: line focusing of the laser beam on the target; an aperture defining the area of the plume; computerized stepper motor-driven X-Y stage translating the heated sampler holder behind the plume-defining aperture in programmed patterns; and substrate mounting block with uniform heating at high temperatures over large areas. It is noted that the high degree of uniformity of the properties in each film batch illustrates that the technique of pulsed laser deposition can be applied to produce large YBCO films of high quality.

  3. Modelling the fate of the Tijuana River discharge plume

    NASA Astrophysics Data System (ADS)

    van Ormondt, M.; Terrill, E.; Hibler, L. F.; van Dongeren, A. R.

    2010-12-01

    After rainfall events, the Tijuana River discharges excess runoff into the ocean in a highly turbid plume. The runoff waters contain large suspended solids concentrations, as well as high levels of toxic contaminants, bacteria, and hepatitis and enteroviruses. Public health hazards posed by the effluent often result in beach closures for several kilometers northward along the U.S. shoreline. A Delft3D model has been set up to predict the fate of the Tijuana River plume. The model takes into account the effects of tides, wind, waves, salinity, and temperature stratification. Heat exchange with the atmosphere is also included. The model consists of a relatively coarse outer domain and a high-resolution surf zone domain that are coupled with Domain Decomposition. The offshore boundary conditions are obtained from the larger NCOM SoCal model (operated by the US Navy) that spans the entire Southern California Bight. A number of discharge events are investigated, in which model results are validated against a wide range of field measurements in the San Diego Bight. These include HF Radar surface currents, REMUS tracks, drifter deployments, satellite imagery, as well as current and temperature profile measurements at a number of locations. The model is able to reproduce the observed current and temperature patterns reasonably well. Under calm conditions, the model results suggest that the hydrodynamics in the San Diego Bight are largely governed by internal waves. During rainfall events, which are typically accompanied by strong winds and high waves, wind and wave driven currents become dominant. An analysis will be made of what conditions determine the trapping and mixing of the plume inside the surfzone and/or the propagation of the plume through the breakers and onto the coastal shelf. The model is now also running in operational mode. Three day forecasts are made every 24 hours. This study was funded by the Office of Naval Research.

  4. Application of NIR Laser Spectroscopy to the Monitoring of Volcanic Plumes: Principles and Practicalities

    NASA Astrophysics Data System (ADS)

    Hamish, A.; Christenson, B. W.; Mazot, A.

    2014-12-01

    The major volatile species in volcanic plume emissions (i.e., H2O, CO2, SO2, HCl, HF) are all strongly infrared (IR)-active, and lend themselves to infrared spectroscopic analysis. However, physical/optical access to plume gases along pathways which include a suitable natural or active IR radiation source is often difficult or impossible to achieve, particularly for timeframes extending beyond short campaign periods. In this study, we present results from preliminary tests conducted on three volcanic CO2 plume emissions using a tunable diode NIR laser system (TDL, Boreal Laser Inc.). The approach is proving itself as a good candidate for continuous monitoring of volcanic plume CO2, and by default all other IR-active constituents for which lasers of appropriate wavelength are available. The CO2 system is configured with a TDL in a transceiver generating laser light which can be tuned to coincide with one of several absorption lines in the CO2 absorption band between 1575 nm and 1585 nm. This beam propagates through the atmosphere (and plume) to a retro-reflector, which returns the beam to a photodiode detector in the transceiver which processes the signal to report real time CO2 column densities. The CO2 absorption line at 1579.1 nm was used to good effect on Mt Ruapehu (NZ) where volcanic gases emanate through a 100 m deep crater lake, resulting in CO2 concentrations of > 78 ppm above background in the mixing zone varying from 4 to 30 m above the lake surface. Subsequent tests on the main plume at White Island, however, generated only poor results with indicated CO2 amounts being less than atmospheric. We concluded that this was the result of interference from a neighboring but comparatively minor H2O absorption band which in the proximal, higher temperature plume (estimated 50-70 °C), had H2O concentrations some 4-5 times greater than ambient. A change to a less sensitive absorption line further removed from potential H2O band interference (1567.9 nm) appears to

  5. Generation of nanoclusters by ultrafast laser ablation of Al: Molecular dynamics study

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

    Miloshevsky, Alexander; Phillips, Mark C.; Harilal, Sivanandan S.

    The laser ablation of materials induced by an ultrashort femtosecond pulse is a complex phenomenon, which depends on both the material properties and the properties of the laser pulse. The unique capability of a combination of molecular dynamics (MD) and Momentum Scaling Model (MSM) methods is developed and applied to a large atomic system for studying the process of ultrafast laser-material interactions, behavior of matter in a highly non-equilibrium state, material disintegration, and formation of nanoparticles (NPs). Laser pulses with several fluences in the range from 500 J/m2 to 5000 J/m2 interacting with a large system of aluminum atoms aremore » simulated. The response of Al material to the laser energy deposition is investigated within the finite-size laser spot. It is found that the shape of the plasma plume is dynamically changing during an expansion process. At several tens of picoseconds it can be characterized as a long hollow ellipsoid surrounded by atomized and nano-clustered particles. The time evolution of NP clusters in the plume is investigated. The collisions between the single Al atoms and generated NPs and fragmentation of large NPs determine the fractions of different-size NP clusters in the plume. The MD-MSM simulations show that laser fluence greatly affects the size distribution of NPs, their polar angles, magnitude and direction vectors of NP velocities. These results and predictions are supported by the experimental data and previous MD simulations.« less

  6. An advanced optical system for laser ablation propulsion in space

    NASA Astrophysics Data System (ADS)

    Bergstue, Grant; Fork, Richard; Reardon, Patrick

    2014-03-01

    We propose a novel space-based ablation driven propulsion engine concept utilizing transmitted energy in the form of a series of ultra-short optical pulses. Key differences are generating the pulses at the transmitting spacecraft and the safe delivery of that energy to the receiving spacecraft for propulsion. By expanding the beam diameter during transmission in space, the energy can propagate at relatively low intensity and then be refocused and redistributed to create an array of ablation sites at the receiver. The ablation array strategy allows greater control over flight dynamics and eases thermal management. Research efforts for this transmission and reception of ultra-short optical pulses include: (1) optical system design; (2) electrical system requirements; (3) thermal management; (4) structured energy transmission safety. Research has also been focused on developing an optical switch concept for the multiplexing of the ultra-short pulses. This optical switch strategy implements multiple reflectors polished into a rotating momentum wheel device to combine the pulses from different laser sources. The optical system design must minimize the thermal load on any one optical element. Initial specifications and modeling for the optical system are being produced using geometrical ray-tracing software to give a better understanding of the optical requirements. In regards to safety, we have advanced the retro-reflective beam locking strategy to include look-ahead capabilities for long propagation distances. Additional applications and missions utilizing multiplexed pulse transmission are also presented. Because the research is in early development, it provides an opportunity for new and valuable advances in the area of transmitted energy for propulsion as well as encourages joint international efforts. Researchers from different countries can cooperate in order to find constructive and safe uses of ordered pulse transmission for propulsion in future space

  7. Electrical Evolution of a Dust Plume from a Low Energy Lunar Impact: A Model Analog to LCROSS

    NASA Technical Reports Server (NTRS)

    Farrell, W. M.; Stubbs, T. J.; Jackson, T. L.; Colaprete, A.; Heldmann, J. L.; Schultz, P. H.; Killen, R. M.; Delory, G. T.; Halekas, J. S.; Marshall, J. R.; hide

    2011-01-01

    A Monte Carlo test particle model was developed that simulates the charge evolution of micron and sub-micron sized dust grains ejected upon low-energy impact of a moderate-size object onto a lunar polar crater floor. Our analog is the LCROSS impact into Cabeus crater. Our primary objective is to model grain discharging as the plume propagates upwards from shadowed crater into sunlight.

  8. Remote sensing the plasmasphere, plasmapause, plumes and other features using ground-based magnetometers

    NASA Astrophysics Data System (ADS)

    Menk, Frederick; Kale, Zoë; Sciffer, Murray; Robinson, Peter; Waters, Colin; Grew, Russell; Clilverd, Mark; Mann, Ian

    2014-11-01

    The plasmapause is a highly dynamic boundary between different magnetospheric particle populations and convection regimes. Some of the most important space weather processes involve wave-particle interactions in this region, but wave properties may also be used to remote sense the plasmasphere and plasmapause, contributing to plasmasphere models. This paper discusses the use of existing ground magnetometer arrays for such remote sensing. Using case studies we illustrate measurement of plasmapause location, shape and movement during storms; refilling of flux tubes within and outside the plasmasphere; storm-time increase in heavy ion concentration near the plasmapause; and detection and mapping of density irregularities near the plasmapause, including drainage plumes, biteouts and bulges. We also use a 2D MHD model of wave propagation through the magnetosphere, incorporating a realistic ionosphere boundary and Alfvén speed profile, to simulate ground array observations of power and cross-phase spectra, hence confirming the signatures of plumes and other density structures.

  9. Mantle plumes and continental tectonics.

    PubMed

    Hill, R I; Campbell, I H; Davies, G F; Griffiths, R W

    1992-04-10

    Mantle plumes and plate tectonics, the result of two distinct modes of convection within the Earth, operate largely independently. Although plumes are secondary in terms of heat transport, they have probably played an important role in continental geology. A new plume starts with a large spherical head that can cause uplift and flood basalt volcanism, and may be responsible for regional-scale metamorphism or crustal melting and varying amounts of crustal extension. Plume heads are followed by narrow tails that give rise to the familiar hot-spot tracks. The cumulative effect of processes associated with tail volcanism may also significantly affect continental crust.

  10. Dynamics and Deposits of Coignimbrite Plumes

    NASA Astrophysics Data System (ADS)

    Engwell, Samantha; de'Michieli Vitturi, Mattia; Esposti Ongaro, Tomaso; Neri, Augusto

    2014-05-01

    Fine ash in the atmosphere poses a significant hazard, with potentially disastrous consequences for aviation and, on deposition, health and infrastructure. Fine-grained particles form a large proportion of ejecta in Plinian volcanic clouds. However, another common, but poorly studied phenomena exists whereby large amounts of fine ash are injected into the atmosphere. Coignimbrite plumes form as material is elutriated from the top of pyroclastic density currents. The ash in these plumes is considerably finer grained than that in Plinian plumes and can be distributed over thousands of kilometres in the atmosphere. Despite their significance, very little is known regarding coignimbrite plume formation and dispersion, predominantly due to the poor preservation of resultant deposits. As a result, consequences of coignimbrite plume formation are usually overlooked when conducting hazard and risk analysis. In this study, deposit characteristics and numerical models of plumes are combined to investigate the conditions required for coignimbrite plume formation. Coignimbrite deposits from the Campanian Ignimbrite eruption (Magnitude 7.7, 39 ka) are well sorted and very fine, with a mode of between 30 and 50 microns, and a significant component of respirable ash (less than 10 microns). Analogous distributions are found for coignimbrite deposits from Tungurahua 2006 and Volcan de Colima (2004-2006), amongst others, regardless of magnitude, type or chemistry of eruption. These results indicate that elutriation processes are the dominant control on coignimbrite grainsize distribution. To further investigate elutriation and coignimbrite plume dynamics, the numerical plume model of Bursik (2001) is applied. Model sensitivity analysis demonstrates that neutral buoyancy conditions (required for the formation of the plume) are controlled by a balance between temperature and gas mass flux in the upper most parts of the pyroclastic density current. In addition, results emphasize the

  11. Numerical Simulations of Europa Hydrothermal Plumes

    NASA Astrophysics Data System (ADS)

    Goodman, J. C.; Lenferink, E.

    2009-12-01

    The liquid water interiors of Europa and other icy moons of the outer solar system are likely to be driven by geothermal heating from the sea floor, leading to the development of buoyant hydrothermal plumes. These plumes potentially control icy surface geomorphology, and are of interest to astrobiologists. We have performed a series of simulations of these plumes using the MITGCM. We assume in this experiment that Europa's ocean is deep (of order 100 km) and unstratified, and that plume buoyancy is controlled by temperature, not composition. A series of experiments was performed to explore a limited region of parameter space, with ocean depth H ranging from 50 to 100 km deep, source heat flux Q between 1 and 10 GW, and values of the Coriolis parameter f between 30% and 90% of the Europa average value. As predicted by earlier work, the plumes in our simulations form narrow cylindrical chimneys (a few km across) under the influence of the Coriolis effect. These plumes broaden over time until they become baroclinically unstable, breaking up into cone-shaped eddies when they become 20-35 km in diameter; the shed eddies are of a similar size. Large-scale currents in the region of the plume range between 1.5 and 5 cm/s; temperature anomalies in the plume far from the seafloor are tiny, varying between 30 and 160 microkelvin. Variations in plume size, shape, speed, and temperature are in excellent agreement with previous laboratory tank experiments, and in rough agreement with theoretical predictions. Plume dynamics and geometry are controlled by a "natural Rossby number" which depends strongly on depth H and Coriolis parameter f, but only weakly on source heat flux Q. However, some specific theoretical predictions are not borne out by these simulations. The time elapsed between startup of the source and the beginning of eddy-shedding is much less variable than predicted; also, the plume temperature varies with ocean depth H when our theory says it should not. Both of

  12. Inter-plume aerodynamics for gasoline spray collapse

    DOE PAGES

    Sphicas, Panos; Pickett, Lyle M.; Skeen, Scott A.; ...

    2017-11-10

    The collapse or merging of individual plumes of direct-injection gasoline injectors is of fundamental importance to engine performance because of its impact on fuel–air mixing. But, the mechanisms of spray collapse are not fully understood and are difficult to predict. The purpose of this work is to study the aerodynamics in the inter-spray region, which can potentially lead to plume collapse. High-speed (100 kHz) particle image velocimetry is applied along a plane between plumes to observe the full temporal evolution of plume interaction and potential collapse, resolved for individual injection events. Supporting information along a line of sight is obtainedmore » using simultaneous diffused back illumination and Mie-scatter techniques. Experiments are performed under simulated engine conditions using a symmetric eight-hole injector in a high-temperature, high-pressure vessel at the “Spray G” operating conditions of the engine combustion network. Indicators of plume interaction and collapse include changes in counter-flow recirculation of ambient gas toward the injector along the axis of the injector or in the inter-plume region between plumes. Furthermore, the effect of ambient temperature and gas density on the inter-plume aerodynamics and the subsequent plume collapse are assessed. Increasing ambient temperature or density, with enhanced vaporization and momentum exchange, accelerates the plume interaction. Plume direction progressively shifts toward the injector axis with time, demonstrating that the plume interaction and collapse are inherently transient.« less

  13. Inter-plume aerodynamics for gasoline spray collapse

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

    Sphicas, Panos; Pickett, Lyle M.; Skeen, Scott A.

    The collapse or merging of individual plumes of direct-injection gasoline injectors is of fundamental importance to engine performance because of its impact on fuel–air mixing. But, the mechanisms of spray collapse are not fully understood and are difficult to predict. The purpose of this work is to study the aerodynamics in the inter-spray region, which can potentially lead to plume collapse. High-speed (100 kHz) particle image velocimetry is applied along a plane between plumes to observe the full temporal evolution of plume interaction and potential collapse, resolved for individual injection events. Supporting information along a line of sight is obtainedmore » using simultaneous diffused back illumination and Mie-scatter techniques. Experiments are performed under simulated engine conditions using a symmetric eight-hole injector in a high-temperature, high-pressure vessel at the “Spray G” operating conditions of the engine combustion network. Indicators of plume interaction and collapse include changes in counter-flow recirculation of ambient gas toward the injector along the axis of the injector or in the inter-plume region between plumes. Furthermore, the effect of ambient temperature and gas density on the inter-plume aerodynamics and the subsequent plume collapse are assessed. Increasing ambient temperature or density, with enhanced vaporization and momentum exchange, accelerates the plume interaction. Plume direction progressively shifts toward the injector axis with time, demonstrating that the plume interaction and collapse are inherently transient.« less

  14. Mantle plumes in the vicinity of subduction zones

    NASA Astrophysics Data System (ADS)

    Mériaux, C. A.; Mériaux, A.-S.; Schellart, W. P.; Duarte, J. C.; Duarte, S. S.; Chen, Z.

    2016-11-01

    We present three-dimensional deep-mantle laboratory models of a compositional plume within the vicinity of a buoyancy-driven subducting plate with a fixed trailing edge. We modelled front plumes (in the mantle wedge), rear plumes (beneath the subducting plate) and side plumes with slab/plume systems of buoyancy flux ratio spanning a range from 2 to 100 that overlaps the ratios in nature of 0.2-100. This study shows that 1) rising side and front plumes can be dragged over thousands of kilometres into the mantle wedge, 2) flattening of rear plumes in the trench-normal direction can be initiated 700 km away from the trench, and a plume material layer of lesser density and viscosity can ultimately almost entirely underlay a retreating slab after slab/plume impact, 3) while side and rear plumes are not tilted until they reach ∼600 km depth, front plumes can be tilted at increasing depths as their plume buoyancy is lessened, and rise at a slower rate when subjected to a slab-induced downwelling, 4) rear plumes whose buoyancy flux is close to that of a slab, can retard subduction until the slab is 600 km long, and 5) slab-plume interaction can lead to a diversity of spatial plume material distributions into the mantle wedge. We discuss natural slab/plume systems of the Cascadia/Bowie-Cobb, and Nazca/San Felix-Juan Fernandez systems on the basis of our experiments and each geodynamic context and assess the influence of slab downwelling at depths for the starting plumes of Java, Coral Sea and East Solomon. Overall, this study shows how slab/plume interactions can result in a variety of geological, geophysical and geochemical signatures.

  15. Cluster formation in laser-induced ablation and evaporation of solids observed by laser ionization time-of-flight mass spectrometry and scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Tench, R. J.; Balooch, M.; Bernardez, L.; Allen, Mike J.; Siekhaus, W. J.; Olander, D. R.; Wang, W.

    1990-04-01

    Laser ionization time-of-flight mass analysis (LIMA) used pulses (5ns) of a frequency-quadrupled Nd-YAG laser (266 nm) focused onto spots of 4 to 100 microns diameter to ablate material, and a reflectron time of flight tube to mass-analyze the plume. The observed mass spectra for Si, Pt, SiC, and UO 2 varied in the distribution of ablation products among atoms, molecules and clusters, depending on laser power density and target material. Cleaved surfaces of highly oriented pyrolytic graphite (HOPG) positioned at room temperature either 10 cm away from materials ablated at 10(exp -5) Torr by 1 to 3 excimer laser (308 nm) pulses of 20 ns duration or 1 m away from materials vaporized at 10(exp -8) Torr by 10 Nd-Glass laser pulses of 1 ms duration were analyzed by Scanning Tunneling Microscopy (STM) in air with angstrom resolution. Clusters up to 30 A in diameter were observed.

  16. MISR Aoba Volcano Plume

    Atmospheric Science Data Center

    2018-06-07

    ... in ongoing eruptions using parallax. View the MISR Active Aerosol Plume-Height (AAP) Project paper to see peak altitude and settling ... R. Kahn/NASA GSFC Access Project Paper: MISR Active Aerosol Plume-Height (AAP) Project Access and Order MISR Data and ...

  17. Active Volcanic Plumes on Io

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This color image, acquired during Galileo's ninth orbit around Jupiter, shows two volcanic plumes on Io. One plume was captured on the bright limb or edge of the moon (see inset at upper right), erupting over a caldera (volcanic depression) named Pillan Patera after a South American god of thunder, fire and volcanoes. The plume seen by Galileo is 140 kilometers (86 miles) high and was also detected by the Hubble Space Telescope. The Galileo spacecraft will pass almost directly over Pillan Patera in 1999 at a range of only 600 kilometers (373 miles).

    The second plume, seen near the terminator (boundary between day and night), is called Prometheus after the Greek fire god (see inset at lower right). The shadow of the 75-kilometer (45- mile) high airborne plume can be seen extending to the right of the eruption vent. The vent is near the center of the bright and dark rings. Plumes on Io have a blue color, so the plume shadow is reddish. The Prometheus plume can be seen in every Galileo image with the appropriate geometry, as well as every such Voyager image acquired in 1979. It is possible that this plume has been continuously active for more than 18 years. In contrast, a plume has never been seen at Pillan Patera prior to the recent Galileo and Hubble Space Telescope images.

    North is toward the top of the picture. The resolution is about 6 kilometers (3.7 miles) per picture element. This composite uses images taken with the green, violet and near infrared filters of the solid state imaging (CCD) system on NASA's Galileo spacecraft. The images were obtained on June 28, 1997, at a range of more than 600,000 kilometers (372,000 miles).

    The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC. JPL is an operating division of California Institute of Technology (Caltech).

    This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page

  18. Significance of ambient conditions in uranium absorption and emission features of laser ablation plasmas

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

    Skrodzki, P. J.; Shah, N. P.; Taylor, N.

    2016-11-01

    This study employs laser ablation (LA) to investigate mechanisms for U optical signal variation under various environmental conditions during laser absorption spectroscopy (LAS) and optical emission spectroscopy (OES). Potential explored mechanisms for signal quenching related to ambient conditions include plasma chemistry (e.g., uranium oxide formation), ambient gas confinement effects, and other collisional interactions between plasma constituents and the ambient gas. LA-LAS studies show that the persistence of the U ground state population is significantly reduced in the presence of air ambient compared to nitrogen. LA-OES results yield congested spectra from which the U I 356.18 nm transition is prominent andmore » serves as the basis for signal tracking. LA-OES signal and persistence vary negligibly between the test gases (air and N2), unlike the LA-LAS results. The plume hydrodynamic features and plume fundamental properties showed similar results in both air and nitrogen ambient. Investigation of U oxide formation in the laser-produced plasma suggests that low U concentration in a sample hinders consistent detection of UO molecular spectra.« less

  19. Significance of ambient conditions in uranium absorption and emission features of laser ablation plasmas

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

    Skrodzki, P. J.; Shah, N. P.; Taylor, N.

    2016-10-02

    This study employs laser ablation (LA) to investigate mechanisms for U optical signal variation under various environmental conditions during laser absorption spectroscopy (LAS) and optical emission spectroscopy (OES). Potential mechanisms explored for signal quenching related to ambient conditions include plasma chemistry (e.g., uranium oxide formation), ambient gas confinement effects, and other collisional interactions between plas-ma constituents and the ambient gas. LA-LAS studies show that the persistence of the U ground state population is significantly reduced in the presence of air ambient compared to nitrogen. LA-OES yields congested spectra from which the U I 356.18 nm transition is prominent and servesmore » as the basis for signal tracking. LA-OES signal and per-sistence vary negligibly between the test gases (air and N 2), unlike the LA-LAS results. The plume hydrodynamic features and plume fundamental properties showed similar results in both air and nitrogen ambient. In conclusion, investigation of U oxide formation in the laser-produced plasma suggests that low U concentration in a sample hinders consistent detection of UO molecular spectra.« less

  20. Exhaust Nozzle Plume and Shock Wave Interaction

    NASA Technical Reports Server (NTRS)

    Castner, Raymond S.; Elmiligui, Alaa; Cliff, Susan

    2013-01-01

    Fundamental research for sonic boom reduction is needed to quantify the interaction of shock waves generated from the aircraft wing or tail surfaces with the exhaust plume. Both the nozzle exhaust plume shape and the tail shock shape may be affected by an interaction that may alter the vehicle sonic boom signature. The plume and shock interaction was studied using Computational Fluid Dynamics simulation on two types of convergent-divergent nozzles and a simple wedge shock generator. The nozzle plume effects on the lower wedge compression region are evaluated for two- and three-dimensional nozzle plumes. Results show that the compression from the wedge deflects the nozzle plume and shocks form on the deflected lower plume boundary. The sonic boom pressure signature of the wedge is modified by the presence of the plume, and the computational predictions show significant (8 to 15 percent) changes in shock amplitude.

  1. Shuttle PRCS plume contamination analysis for Astro-2 mission

    NASA Technical Reports Server (NTRS)

    Wang, Francis C.; Greene, Cindy

    1993-01-01

    The Astro-2 mission scheduled for Jan. 1995 flight is co-manifested with the Spartan experiment. The Astro instrument array consists of several telescopes operating in the UV spectrum. To obtain the desired 300 observations with the telescope array in a shorter time than the Astro-1 mission, it will be necessary to use the primary reaction control system (PRCS) rather than just the Vernier reaction control system. The high mass flow rate of the PRCS engines cause considerable concern about contamination due to PRCS plume return flux. Performance of these instruments depends heavily on the environment they encounter. The ability of the optical system to detect a remote signal depends not only on the intensity of the incoming signal, but also on the ensuing transmission loss through the optical train of the instrument. Performance of these instruments is thus dependent on the properties of the optical surface and the medium through which it propagates. The on-orbit contamination environment will have a strong influence on the performance of these instruments. The finding of a two-month study of the molecular contamination environment of the Astro-2 instruments due to PRCS thruster plumes during the planned Astro-2 mission are summarized.

  2. Plume Detection and Plume Top Height Estimation using SLSTR

    NASA Astrophysics Data System (ADS)

    Virtanen, Timo H.; Kolmonen, Pekka; Sogacheva, Larisa; Rodriguez, Edith; Saponaro, Giulia; de Leeuw, Gerrit

    2017-04-01

    We present preliminary results on ash and desert dust plume detection and plume top height estimates based on satellite data from the Sea and Land Surface Temperature Radiometer (SLSTR) aboard Sentinel-3, launched in 2016. The methods are based on the previously developed AATSR Correlation Method (ACM) height estimation algorithm, which utilized the data of the preceding similar instrument, Advanced Along Track Scanning Radiometer (AATSR). The height estimate is based on the stereo-viewing capability of SLSTR, which allows to determine the parallax between the satellite's 55° backward and nadir views, and thus the corresponding height. The ash plume detection is based on the brightness temperature difference between between thermal infrared (TIR) channels centered at 11 and 12 μm, which show characteristic signals for both desert dust and ash plumes. The SLSTR instrument provides a unique combination of dual-view capability and a wavelength range from visible to thermal infrared, rendering it an ideal instrument for this work. Accurate information on the volcanic ash position is important for air traffic safety. The ACM algorithm can provide valuable data of both horizontal and vertical ash dispersion. These data may be useful for comparisons with other volcanic ash and desert dust retrieval methods and dispersion models. The current work is being carried out as part of the H2020 project EUNADICS-AV ("European Natural Disaster Coordination and Information System for Aviation"), which started in October 2016.

  3. Comparison of jet plume shape predictions and plume influence on sonic boom signature

    NASA Technical Reports Server (NTRS)

    Barger, Raymond L.; Melson, N. Duane

    1992-01-01

    An Euler shock-fitting marching code yields good agreement with semiempirically determined plume shapes, although the agreement decreases somewhat with increasing nozzle angle and the attendant increase in the nonisentropic nature of the flow. Some calculations for the low boom configuration with a simple engine indicated that, for flight at altitudes above 60,000 feet, the plume effect is dominant. This negates the advantages of a low boom design. At lower altitudes, plume effects are significant, but of the order that can be incorporated into the low boom design process.

  4. On the use of a laser ablation as a laboratory seismic source

    NASA Astrophysics Data System (ADS)

    Shen, Chengyi; Brito, Daniel; Diaz, Julien; Zhang, Deyuan; Poydenot, Valier; Bordes, Clarisse; Garambois, Stéphane

    2017-04-01

    Mimic near-surface seismic imaging conducted in well-controlled laboratory conditions is potentially a powerful tool to study large scale wave propagations in geological media by means of upscaling. Laboratory measurements are indeed particularly suited for tests of theoretical modellings and comparisons with numerical approaches. We have developed an automated Laser Doppler Vibrometer (LDV) platform, which is able to detect and register broadband nano-scale displacements on the surface of various materials. This laboratory equipment has already been validated in experiments where piezoelectric transducers were used as seismic sources. We are currently exploring a new seismic source in our experiments, a laser ablation, in order to compensate some drawbacks encountered with piezoelectric sources. The laser ablation source is considered to be an interesting ultrasound wave generator since the 1960s. It was believed to have numerous potential applications such as the Non-Destructive Testing (NDT) and the measurements of velocities and attenuations in solid samples. We aim at adapting and developing this technique into geophysical experimental investigations in order to produce and explore complete micro-seismic data sets in the laboratory. We will first present the laser characteristics including its mechanism, stability, reproducibility, and will evaluate in particular the directivity patterns of such a seismic source. We have started by applying the laser ablation source on the surfaces of multi-scale homogeneous aluminum samples and are now testing it on heterogeneous and fractured limestone cores. Some other results of data processing will also be shown, especially the 2D-slice V P and V S tomographic images obtained in limestone samples. Apart from the experimental records, numerical simulations will be carried out for both the laser source modelling and the wave propagation in different media. First attempts will be done to compare quantitatively the

  5. Enceladus Plume Movie

    NASA Image and Video Library

    2005-12-06

    Jets of icy particles burst from Saturn’s moon Enceladus in this brief movie sequence of four images taken on Nov. 27, 2005. The sensational discovery of active eruptions on a third outer solar system body (Io and Triton are the others) is surely one of the great highlights of the Cassini mission. Imaging scientists, as reported in the journal Science on March 10, 2006, believe that the jets are geysers erupting from pressurized subsurface reservoirs of liquid water above 273 degrees Kelvin (0 degrees Celsius). Images taken in January 2005 appeared to show the plume emanating from the fractured south polar region of Enceladus, but the visible plume was only slightly brighter than the background noise in the image, because the lighting geometry was not suitable to reveal the true details of the feature. This potential sighting, in addition to the detection of the icy particles in the plume by other Cassini instruments, prompted imaging scientists to target Enceladus again with exposures designed to confirm the validity of the earlier plume sighting. The new views show individual jets, or plume sources, that contribute to the plume with much greater visibility than the earlier images. The full plume towers over the 505-kilometer-wide (314-mile) moon and is at least as tall as the moon's diameter. The four 10-second exposures were taken over the course of about 36 minutes at approximately 12 minute intervals. Enceladus rotates about 7.5 degrees in longitude over the course of the frames, and most of the observed changes in the appearances of the jets is likely attributable to changes in the viewing geometry. However, some of the changes may be due to actual variation in the flow from the jets on a time scale of tens of minutes. Additionally, the shift of the sources seen here should provide information about their location in front of and behind the visible limb (edge) of Enceladus. These images were obtained using the Cassini spacecraft narrow-angle camera at

  6. COMPARING AND LINKING PLUMES ACROSS MODELING APPROACHES

    EPA Science Inventory

    River plumes carry many pollutants, including microorganisms, into lakes and the coastal ocean. The physical scales of many stream and river plumes often lie between the scales for mixing zone plume models, such as the EPA Visual Plumes model, and larger-sized grid scales for re...

  7. Third harmonic generation in air ambient and laser ablated carbon plasma

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

    Singh, Ravi Pratap, E-mail: ravips@iitk.ac.in; Gupta, Shyam L.; Thareja, Raj K.

    2015-12-15

    We report the third harmonic generation of a nanosecond laser pulse (1.06 μm) in air ambient and in the presence of nanoparticles from laser ablated carbon plasma. Significant decrease in the threshold of third harmonic generation and multi-fold increment in the intensity of generated third harmonic is observed in presence of carbon plasma. The third harmonic in air is due to the quasi-resonant four photon process involving vibrationally excited states of molecular ion of nitrogen due to electron impact ionization and laser pulse. Following optical emission spectroscopic observations we conclude that the presence of C{sub 2} and CN in the ablatedmore » plume play a vital role in the observed third harmonic signals.« less

  8. Assessment of analytical techniques for predicting solid propellant exhaust plumes and plume impingement environments

    NASA Technical Reports Server (NTRS)

    Tevepaugh, J. A.; Smith, S. D.; Penny, M. M.

    1977-01-01

    An analysis of experimental nozzle, exhaust plume, and exhaust plume impingement data is presented. The data were obtained for subscale solid propellant motors with propellant Al loadings of 2, 10 and 15% exhausting to simulated altitudes of 50,000, 100,000 and 112,000 ft. Analytical predictions were made using a fully coupled two-phase method of characteristics numerical solution and a technique for defining thermal and pressure environments experienced by bodies immersed in two-phase exhaust plumes.

  9. Influence of the Minho River plume on the Rias Baixas (NW of the Iberian Peninsula)

    NASA Astrophysics Data System (ADS)

    Sousa, M. C.; Vaz, N.; Alvarez, I.; Gomez-Gesteira, M.; Dias, J. M.

    2014-11-01

    The buoyancy generated by the Minho estuarine plume can flood the Rias Baixas for long periods, reversing the normal salinity gradients. Thus, the main purpose of this work was to study the propagation of Minho estuarine plume to the Rias Baixas, establishing the wind and river discharge conditions in which this plume affects the circulation and hydrography features of these coastal systems as well as the plume characteristics under the most probable forcing conditions, through the application of the numerical model MOHID. For this purpose, several scenarios with different river discharges and wind were simulated. The numerical results revealed that the Minho estuarine plume responds rapidly to wind variations and is influenced by coastline geometry. Under Minho River discharges higher than 700 m3 s- 1 and weak northward winds (3 m s- 1) the circulation patterns of the Rias de Vigo and Pontevedra are reversed. On the other hand, moderate northward winds (6 m s- 1) combined with Minho River discharges higher than 200 m3 s- 1, 300 m3 s- 1 and 700 m3 s- 1 reverse the circulation pattern of the Rias de Vigo, Pontevedra and Arousa, respectively. Under the same conditions, the water exchange between Rias Baixas was analyzed using a particle-tracking model following the trajectories of particles released close to the Minho River mouth. Over 5 days, under Minho River discharges higher than 2100 m3 s- 1 combined with northward winds of 6 m s- 1, an intense water exchange between Rias was observed. However, only 20% of the particles found in Ria de Pontevedra come directly from the Minho River.

  10. MISR Observations of Etna Volcanic Plumes

    NASA Technical Reports Server (NTRS)

    Scollo, S.; Kahn, R. A.; Nelson, D. L.; Coltelli, M.; Diner, D. J.; Garay, M. J.; Realmuto, V. J.

    2012-01-01

    In the last twelve years, Mt. Etna, located in eastern Sicily, has produced a great number of explosive eruptions. Volcanic plumes have risen to several km above sea level and created problems for aviation and the communities living near the volcano. A reduction of hazards may be accomplished using remote sensing techniques to evaluate important features of volcanic plumes. Since 2000, the Multiangle Imaging SpectroRadiometer (MISR) on board NASA s Terra spacecraft has been extensively used to study aerosol dispersal and to extract the three-dimensional structure of plumes coming from anthropogenic or natural sources, including volcanoes. In the present work, MISR data from several explosive events occurring at Etna are analyzed using a program named MINX (MISR INteractive eXplorer). MINX uses stereo matching techniques to evaluate the height of the volcanic aerosol with a precision of a few hundred meters, and extracts aerosol properties from the MISR Standard products. We analyzed twenty volcanic plumes produced during the 2000, 2001, 2002-03, 2006 and 2008 Etna eruptions, finding that volcanic aerosol dispersal and column height obtained by this analysis is in good agreement with ground-based observations. MISR aerosol type retrievals: (1) clearly distinguish volcanic plumes that are sulphate and/or water vapor dominated from ash-dominated ones; (2) detect even low concentrations of volcanic ash in the atmosphere; (3) demonstrate that sulphate and/or water vapor dominated plumes consist of smaller-sized particles compared to ash plumes. This work highlights the potential of MISR to detect important volcanic plume characteristics that can be used to constrain the eruption source parameters in volcanic ash dispersion models. Further, the possibility of discriminating sulphate and/or water vapor dominated plumes from ash-dominated ones is important to better understand the atmospheric impact of these plumes.

  11. Segregation of acid plume pixels from background water pixels, signatures of background water and dispersed acid plumes, and implications for calculation of iron concentration in dense plumes

    NASA Technical Reports Server (NTRS)

    Bahn, G. S.

    1978-01-01

    Two files of data, obtained with a modular multiband scanner, for an acid waste dump into ocean water, were analyzed intensively. Signatures were derived for background water at different levels of effective sunlight intensity, and for different iron concentrations in the dispersed plume from the dump. The effect of increased sunlight intensity on the calculated iron concentration was found to be relatively important at low iron concentrations and relatively unimportant at high values of iron concentration in dispersed plumes. It was concluded that the basic equation for iron concentration is not applicable to dense plumes, particularly because lower values are indicated at the very core of the plume, than in the surrounding sheath, whereas radiances increase consistently from background water to dispersed plume to inner sheath to innermost core. It was likewise concluded that in the dense plume the iron concentration would probably best be measured by the higher wave length radiances, although the suitable relationship remains unknown.

  12. Single laser based pump-probe technique to study plasma shielding during nanosecond laser ablation of copper thin films

    NASA Astrophysics Data System (ADS)

    Nammi, Srinagalakshmi; Vasa, Nilesh J.; Gurusamy, Balaganesan; Mathur, Anil C.

    2017-09-01

    A plasma shielding phenomenon and its influence on micromachining is studied experimentally and theoretically for laser wavelengths of 355 nm, 532 nm and 1064 nm. A time resolved pump-probe technique is proposed and demonstrated by splitting a single nanosecond Nd3+:YAG laser into an ablation laser (pump laser) and a probe laser to understand the influence of plasma shielding on laser ablation of copper (Cu) clad on polyimide thin films. The proposed nanosecond pump-probe technique allows simultaneous measurement of the absorption characteristics of plasma produced during Cu film ablation by the pump laser. Experimental measurements of the probe intensity distinctly show that the absorption by the ablated plume increases with increase in the pump intensity, as a result of plasma shielding. Theoretical estimation of the intensity of the transmitted pump beam based on the thermo-temporal modeling is in qualitative agreement with the pump-probe based experimental measurements. The theoretical estimate of the depth attained for a single pulse with high pump intensity value on a Cu thin film is limited by the plasma shielding of the incident laser beam, similar to that observed experimentally. Further, the depth of micro-channels produced shows a similar trend for all three wavelengths, however, the channel depth achieved is lesser at the wavelength of 1064 nm.

  13. Measuring the iron spectral opacity in solar conditions using a double ablation front scheme

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

    Colaitis, A.; Ducret, J. E.; Turck-Chieze, S

    We propose a new method to achieve hydrodynamic conditions relevant for the investigation of the radiation transport properties of the plasma at the base of the solar convection zone. The method is designed in the framework of opacity measurements with high-power lasers and exploits the temporal and spatial stability of hydrodynamic parameters in counter-propagating Double Ablation Front (DAF) structures.

  14. Modeling basin- and plume-scale processes of CO2 storage for full-scale deployment

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

    Zhou, Q.; Birkholzer, J.T.; Mehnert, E.

    Integrated modeling of basin- and plume-scale processes induced by full-scale deployment of CO{sub 2} storage was applied to the Mt. Simon Aquifer in the Illinois Basin. A three-dimensional mesh was generated with local refinement around 20 injection sites, with approximately 30 km spacing. A total annual injection rate of 100 Mt CO{sub 2} over 50 years was used. The CO{sub 2}-brine flow at the plume scale and the single-phase flow at the basin scale were simulated. Simulation results show the overall shape of a CO{sub 2} plume consisting of a typical gravity-override subplume in the bottom injection zone of highmore » injectivity and a pyramid-shaped subplume in the overlying multilayered Mt. Simon, indicating the important role of a secondary seal with relatively low-permeability and high-entry capillary pressure. The secondary-seal effect is manifested by retarded upward CO{sub 2} migration as a result of multiple secondary seals, coupled with lateral preferential CO{sub 2} viscous fingering through high-permeability layers. The plume width varies from 9.0 to 13.5 km at 200 years, indicating the slow CO{sub 2} migration and no plume interference between storage sites. On the basin scale, pressure perturbations propagate quickly away from injection centers, interfere after less than 1 year, and eventually reach basin margins. The simulated pressure buildup of 35 bar in the injection area is not expected to affect caprock geomechanical integrity. Moderate pressure buildup is observed in Mt. Simon in northern Illinois. However, its impact on groundwater resources is less than the hydraulic drawdown induced by long-term extensive pumping from overlying freshwater aquifers.« less

  15. Microwave ablation versus radiofrequency ablation in the kidney: high-power triaxial antennas create larger ablation zones than similarly sized internally cooled electrodes.

    PubMed

    Laeseke, Paul F; Lee, Fred T; Sampson, Lisa A; van der Weide, Daniel W; Brace, Christopher L

    2009-09-01

    To determine whether microwave ablation with high-power triaxial antennas creates significantly larger ablation zones than radiofrequency (RF) ablation with similarly sized internally cooled electrodes. Twenty-eight 12-minute ablations were performed in an in vivo porcine kidney model. RF ablations were performed with a 200-W pulsed generator and either a single 17-gauge cooled electrode (n = 9) or three switched electrodes spaced 1.5 cm apart (n = 7). Microwave ablations were performed with one (n = 7), two (n = 3), or three (n = 2) 17-gauge triaxial antennas to deliver 90 W continuous power per antenna. Multiple antennas were powered simultaneously. Temperatures 1 cm from the applicator were measured during two RF and microwave ablations each. Animals were euthanized after ablation and ablation zone diameter, cross-sectional area, and circularity were measured. Comparisons between groups were performed with use of a mixed-effects model with P values less than .05 indicating statistical significance. No adverse events occurred during the procedures. Three-electrode RF (mean area, 14.7 cm(2)) and single-antenna microwave (mean area, 10.9 cm(2)) ablation zones were significantly larger than single-electrode RF zones (mean area, 5.6 cm(2); P = .001 and P = .0355, respectively). No significant differences were detected between single-antenna microwave and multiple-electrode RF. Ablation zone circularity was similar across groups (P > .05). Tissue temperatures were higher during microwave ablation (maximum temperature of 123 degrees C vs 100 degrees C for RF). Microwave ablation with high-power triaxial antennas created larger ablation zones in normal porcine kidneys than RF ablation with similarly sized applicators.

  16. Ablation mass features in multi-pulses femtosecond laser ablate molybdenum target

    NASA Astrophysics Data System (ADS)

    Zhao, Dongye; Gierse, Niels; Wegner, Julian; Pretzler, Georg; Oelmann, Jannis; Brezinsek, Sebastijan; Liang, Yunfeng; Neubauer, Olaf; Rasinski, Marcin; Linsmeier, Christian; Ding, Hongbin

    2018-03-01

    In this study, the ablation mass features related to reflectivity of bulk Molybdenum (Mo) were investigated by a Ti: Sa 6 fs laser pulse at central wavelength 790 nm. The ablated mass removal was determined using Confocal Microscopy (CM) technique. The surface reflectivity was calibrated and measured by a Lambda 950 spectrophotometer as well as a CCD camera during laser ablation. The ablation mass loss per pulse increase with the increasing of laser shots, meanwhile the surface reflectivity decrease. The multi-pulses (100 shots) ablation threshold of Mo was determined to be 0.15 J/cm2. The incubation coefficient was estimated as 0.835. The reflectivity change of the Mo target surface following multi-pulses laser ablation were studied as a function of laser ablation shots at various laser fluences from 1.07 J/cm2 to 36.23 J/cm2. The results of measured reflectivity indicate that surface reflectivity of Mo target has a significant decline in the first 3-laser pulses at the various fluences. These results are important for developing a quantitative analysis model for laser induced ablation and laser induced breakdown spectroscopy for the first wall diagnosis of EAST tokamak.

  17. Transmission Geometry Laser Ablation into a Non-Contact Liquid Vortex Capture Probe for Mass Spectrometry Imaging

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

    Ovchinnikova, Olga S; Bhandari, Deepak; Lorenz, Matthias

    2014-01-01

    RATIONALE: Capture of material from a laser ablation plume into a continuous flow stream of solvent provides the means for uninterrupted sampling, transport and ionization of collected material for coupling with mass spectral analysis. Reported here is the use of vertically aligned transmission geometry laser ablation in combination with a new non-contact liquid vortex capture probe coupled with electrospray ionization for spot sampling and chemical imaging with mass spectrometry. Methods: A vertically aligned continuous flow liquid vortex capture probe was positioned directly underneath a sample surface in a transmission geometry laser ablation (355 nm, 10 Hz, 7 ns pulse width)more » setup to capture into solution the ablated material. The outlet of the vortex probe was coupled to the Turbo V ion source of an AB SCIEX TripleTOF 5600+ mass spectrometer. System operation and performance metrics were tested using inked patterns and thin tissue sections. Glass slides and slides designed especially for laser capture microdissection, viz., DIRECTOR slides and PEN 1.0 (polyethylene naphthalate) membrane slides, were used as sample substrates. Results: The estimated capture efficiency of laser ablated material was 24%, which was enabled by the use of a probe with large liquid surface area (~ 2.8 mm2) and with gravity to help direct ablated material vertically down towards the probe. The swirling vortex action of the liquid surface potentially enhanced capture and dissolution of not only particulates, but also gaseous products of the laser ablation. The use of DIRECTOR slides and PEN 1.0 (polyethylene naphthalate) membrane slides as sample substrates enabled effective ablation of a wide range of sample types (basic blue 7, polypropylene glycol, insulin and cyctochrome c) without photodamage using a UV laser. Imaging resolution of about 6 m was demonstrated for stamped ink on DIRECTOR slides based on the ability to distinguish features present both in the optical and in

  18. Ambient infrared laser ablation mass spectrometry (AIRLAB-MS) with plume capture by continuous flow solvent probe

    DOEpatents

    O'Brien, Jeremy T.; Williams, Evan R.; Holman, Hoi-Ying N.

    2017-10-31

    A new experimental setup for spatially resolved ambient infrared laser ablation mass spectrometry (AIRLAB-MS) that uses an infrared microscope with an infinity-corrected reflective objective and a continuous flow solvent probe coupled to a Fourier transform ion cyclotron resonance mass spectrometer is described. The efficiency of material transfer from the sample to the electrospray ionization emitter was determined using glycerol/methanol droplets containing 1 mM nicotine and is .about.50%. This transfer efficiency is significantly higher than values reported for similar techniques.

  19. Global ablation techniques.

    PubMed

    Woods, Sarah; Taylor, Betsy

    2013-12-01

    Global endometrial ablation techniques are a relatively new surgical technology for the treatment of heavy menstrual bleeding that can now be used even in an outpatient clinic setting. A comparison of global ablation versus earlier ablation technologies notes no significant differences in success rates and some improvement in patient satisfaction. The advantages of the newer global endometrial ablation systems include less operative time, improved recovery time, and decreased anesthetic risk. Ablation procedures performed in an outpatient surgical or clinic setting provide advantages both of potential cost savings for patients and the health care system and improved patient convenience. Copyright © 2013. Published by Elsevier Inc.

  20. Liquid Booster Module (LBM) plume flowfield model

    NASA Technical Reports Server (NTRS)

    Smith, S. D.

    1981-01-01

    A complete definition of the LBM plume is important for many Shuttle design criteria. The exhaust plume shape has a significant effect on the vehicle base pressure. The LBM definition is also important to the Shuttle base heating, aerodynamics and the influence of the exhaust plume on the launch stand and environment. For these reasons a knowledge of the LBM plume characteristics is necessary. A definition of the sea level LBM plume as well as at several points along the Shuttle trajectory to LBM, burnout is presented.

  1. Plasma plume MHD power generator and method

    DOEpatents

    Hammer, James H.

    1993-01-01

    Highly-conducting plasma plumes are ejected across the interplanetary magnetic field from a situs that is moving relative to the solar wind, such as a spacecraft or an astral body, such as the moon, having no magnetosphere that excludes the solar wind. Discrete plasma plumes are generated by plasma guns at the situs extending in opposite directions to one another and at an angle, preferably orthogonal, to the magnetic field direction of the solar wind plasma. The opposed plumes are separately electrically connected to their source by a low impedance connection. The relative movement between the plasma plumes and the solar wind plasma creates a voltage drop across the plumes which is tapped by placing the desired electrical load between the electrical connections of the plumes to their sources. A portion of the energy produced may be used in generating the plasma plumes for sustained operation.

  2. Lithospheric mantle structure beneath Northern Scotland: Pre-plume remnant or syn-plume signature?

    NASA Astrophysics Data System (ADS)

    Knapp, J.

    2003-04-01

    Upper mantle reflectors (Flannan and W) beneath the northwestern British Isles are some of the best-known and most-studied examples of preserved structure within the continental mantle lithosphere, and are spatially coincident with the surface location of early Iceland plume volcanism in the British Tertiary Province. First observed on BIRPS (British Institutions Reflection Profiling Syndicate) marine deep seismic reflection profiles in the early 1980's, these reflectors have subsequently been imaged and correlated on additional reflection and refraction profiles in the offshore area of northern and western Scotland. The age and tectonic significance of these reflectors remains a subject of wide debate, due in part to the absence of robust characterization of the upper mantle velocity structure in this tectonically complex area. Interpretations advanced over the past two decades for the dipping Flannan reflector range from fossilized subduction complex to large-scale extensional shear zone, and span ages from Proterozoic to early Mesozoic. Crustal geology of the region records early Paleozoic continental collision and late Paleozoic to Mesozoic extension. Significant modification of the British lithosphere in early Tertiary time, including dramatic thinning and extensive basaltic intrusion associated with initiation and development of the Iceland plume, suggests either (1) an early Tertiary age for the Flannan reflector or (2) preservation of ancient features within the mantle lithosphere despite such pervasive modification. Exisitng constraints are consistent with a model for early Tertiary origin of the Flannan reflector as the downdip continuation of the Rockall Trough extensional system of latest Cretaceous to earliest Tertiary age during opening of the northern Atlantic Ocean and initiation of the Iceland plume. Lithopsheric thinning beneath present-day northern Scotland could have served to focus the early expression of plume volcanism (British Tertiary

  3. Prometheus: Io's wandering plume.

    PubMed

    Kieffer, S W; Lopes-Gautier, R; McEwen, A; Smythe, W; Keszthelyi, L; Carlson, R

    2000-05-19

    Unlike any volcanic behavior ever observed on Earth, the plume from Prometheus on Io has wandered 75 to 95 kilometers west over the last 20 years since it was first discovered by Voyager and more recently observed by Galileo. Despite the source motion, the geometric and optical properties of the plume have remained constant. We propose that this can be explained by vaporization of a sulfur dioxide and/or sulfur "snowfield" over which a lava flow is moving. Eruption of a boundary-layer slurry through a rootless conduit with sonic conditions at the intake of the melted snow can account for the constancy of plume properties.

  4. The Alberta smoke plume observation study

    NASA Astrophysics Data System (ADS)

    Anderson, Kerry; Pankratz, Al; Mooney, Curtis; Fleetham, Kelly

    2018-02-01

    A field project was conducted to observe and measure smoke plumes from wildland fires in Alberta. This study used handheld inclinometer measurements and photos taken at lookout towers in the province. Observations of 222 plumes were collected from 21 lookout towers over a 6-year period from 2010 to 2015. Observers reported the equilibrium and maximum plume heights based on the plumes' final levelling heights and the maximum lofting heights, respectively. Observations were tabulated at the end of each year and matched to reported fires. Fire sizes at assessment times and forest fuel types were reported by the province. Fire weather conditions were obtained from the Canadian Wildland Fire Information System (CWFIS). Assessed fire sizes were adjusted to the appropriate size at plume observation time using elliptical fire-growth projections. Though a logical method to collect plume observations in principle, many unanticipated issues were uncovered as the project developed. Instrument limitations and environmental conditions presented challenges to the investigators, whereas human error and the subjectivity of observations affected data quality. Despite these problems, the data set showed that responses to fire behaviour conditions were consistent with the physical processes leading to plume rise. The Alberta smoke plume observation study data can be found on the Canadian Wildland Fire Information System datamart (Natural Resources Canada, 2018) at http://cwfis.cfs.nrcan.gc.ca/datamart.

  5. Mt Agung (Bali) Eruption Plumes

    Atmospheric Science Data Center

    2018-05-23

    article title:  Mt Agung (Bali) Eruption Plumes     View larger image ... 2017 (left) and calculated plume heights (right)   Volcanic eruptions can generate a significant amount of atmospheric aerosols ...

  6. Understanding the plume dynamics of explosive super-eruptions.

    PubMed

    Costa, Antonio; J Suzuki, Yujiro; Koyaguchi, Takehiro

    2018-02-13

    Explosive super-eruptions can erupt up to thousands of km 3 of magma with extremely high mass flow rates (MFR). The plume dynamics of these super-eruptions are still poorly understood. To understand the processes operating in these plumes we used a fluid-dynamical model to simulate what happens at a range of MFR, from values generating intense Plinian columns, as did the 1991 Pinatubo eruption, to upper end-members resulting in co-ignimbrite plumes like Toba super-eruption. Here, we show that simple extrapolations of integral models for Plinian columns to those of super-eruption plumes are not valid and their dynamics diverge from current ideas of how volcanic plumes operate. The different regimes of air entrainment lead to different shaped plumes. For the upper end-members can generate local up-lifts above the main plume (over-plumes). These over-plumes can extend up to the mesosphere. Injecting volatiles into such heights would amplify their impact on Earth climate and ecosystems.

  7. Stable plume rise in a shear layer.

    PubMed

    Overcamp, Thomas J

    2007-03-01

    Solutions are given for plume rise assuming a power-law wind speed profile in a stably stratified layer for point and finite sources with initial vertical momentum and buoyancy. For a constant wind speed, these solutions simplify to the conventional plume rise equations in a stable atmosphere. In a shear layer, the point of maximum rise occurs further downwind and is slightly lower compared with the plume rise with a constant wind speed equal to the wind speed at the top of the stack. If the predictions with shear are compared with predictions for an equivalent average wind speed over the depth of the plume, the plume rise with shear is higher than plume rise with an equivalent average wind speed.

  8. Robotically assisted ablation produces more rapid and greater signal attenuation than manual ablation.

    PubMed

    Koa-Wing, Michael; Kojodjojo, Pipin; Malcolme-Lawes, Louisa C; Salukhe, Tushar V; Linton, Nick W F; Grogan, Aaron P; Bergman, Dale; Lim, Phang Boon; Whinnett, Zachary I; McCarthy, Karen; Ho, Siew Yen; O'Neill, Mark D; Peters, Nicholas S; Davies, D Wyn; Kanagaratnam, Prapa

    2009-12-01

    Robotic remote catheter ablation potentially provides improved catheter-tip stability, which should improve the efficiency of radiofrequency energy delivery. Percentage reduction in electrogram peak-to-peak voltage has been used as a measure of effectiveness of ablation. We tested the hypothesis that improved catheter-tip stability of robotic ablation can diminish signals to a greater degree than manual ablation. In vivo NavX maps of 7 pig atria were constructed. Separate lines of ablation were performed robotically and manually, recording pre- and postablation peak-to-peak voltages at 10, 20, 30, and 60 seconds and calculating signal amplitude reduction. Catheter ablation settings were constant (25W, 50 degrees , 17 mL/min, 20-30 g catheter tip pressure). The pigs were sacrificed and ablation lesions correlated with NavX maps. Robotic ablation reduced signal amplitude to a greater degree than manual ablation (49 +/- 2.6% vs 29 +/- 4.5% signal reduction after 1 minute [P = 0.0002]). The mean energy delivered (223 +/- 184 J vs 231 +/- 190 J, P = 0.42), power (19 +/- 3.5 W vs 19 +/- 4 W, P = 0.84), and duration of ablation (15 +/- 9 seconds vs 15 +/- 9 seconds, P = 0.89) was the same for manual and robotic. The mean peak catheter-tip temperature was higher for robotic (45 +/- 5 degrees C vs 42 +/- 3 degrees C [P < 0.0001]). The incidence of >50% signal reduction was greater for robotic (37%) than manual (21%) ablation (P = 0.0001). Robotically assisted ablation appears to be more effective than manual ablation at signal amplitude reduction, therefore may be expected to produce improved clinical outcomes.

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

    PubMed

    Wu, Po-Hung; Brace, Chris L

    2016-08-21

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

  10. Quantification of plume opacity by digital photography.

    PubMed

    Du, Ke; Rood, Mark J; Kim, Byung J; Kemme, Michael R; Franek, Bill; Mattison, Kevin

    2007-02-01

    The United States Environmental Protection Agency (USEPA) developed Method 9 to describe how plume opacity can be quantified by humans. However, use of observations by humans introduces subjectivity, and is expensive due to semiannual certification requirements of the observers. The Digital Opacity Method (DOM) was developed to quantify plume opacity at lower cost, with improved objectivity, and to provide a digital record. Photographs of plumes were taken with a calibrated digital camera under specified conditions. Pixel values from those photographs were then interpreted to quantify the plume's opacity using a contrast model and a transmission model. The contrast model determines plume opacity based on pixel values that are related to the change in contrast between two backgrounds that are located behind and next to the plume. The transmission model determines the plume's opacity based on pixel values that are related to radiances from the plume and its background. DOM was field tested with a smoke generator. The individual and average opacity errors of DOM were within the USEPA Method 9 acceptable error limits for both field campaigns. Such results are encouraging and support the use of DOM as an alternative to Method 9.

  11. Is the 'Fast Halo' around Hawaii as imaged in the PLUME experiment direct evidence for buoyant plume-fed asthenosphere?

    NASA Astrophysics Data System (ADS)

    Morgan, J. P.; Shi, C.; Hasenclever, J.

    2010-12-01

    An intriguing spatial pattern of variations in shear-wave arrival times has been mapped in the PLUME ocean bottom experiment (Wolfe et al., 2009) around Hawaii. The pattern consists of a halo of fast travel times surrounding a disk of slow arrivals from waves traveling up though the plume. We think it is directly sensing the pattern of dynamic uplift of the base of a buoyant asthenosphere - the buoyancy of the plume conduit lifting a 'rim' of the cooler, denser mantle that the plume rises through. The PLUME analysis inverted for lateral shear velocity variations beneath the lithosphere, after removing the assumed 1-D model velocity structure IASP91. They found that a slow plume-conduit extends to at least 1200 km below the Hawaiian hotspot. In this inversion the slow plume conduit is — quite surprisingly - surrounded by a fast wavespeed halo. A fast halo is impossible to explain as a thermal halo around the plume; this should lead to a slow wavespeed halo, not a fast one. Plume-related shearwave anisotropy also cannot simply explain this pattern — simple vertical strain around the plume conduit would result in an anisotropic slow shear-wavespeed halo, not a fast one. (Note the PLUME experiment’s uniform ‘fast-halo’ structure from 50-400km is likely to have strong vertical streaking in the seismic image; Pacific Plate-driven shear across a low-viscosity asthenosphere would be expected to disrupt and distort any cold sheet of vertical downwelling structure between 50-400km depths so that it would no longer be vertical as it is in the 2009 PLUME image with its extremely poor vertical depth control.) If the asthenosphere is plume-fed, hence more buoyant than underlying mantle, then there can be a simple explanation for this pattern. The anomaly would be due to faster traveltimes resulting from dynamic relief at the asthenosphere-mesosphere interface; uplift of the denser mesosphere by the buoyancy of the rising plume increases the distance a wave travels

  12. Diagnostic budgets of analyzed and modelled tropical plumes

    NASA Technical Reports Server (NTRS)

    Mcguirk, James P.; Vest, Gerry W.

    1993-01-01

    Blackwell et al. successfully simulated tropical plumes in a global barotropic model valid at 200 mb. The plume evolved in response to strong equatorial convergence which simulated a surge in the Walker Circulation. The defining characteristics of simulated plumes are: a subtropical jet with southerlies emanating from the deep tropics; a tropical/mid-latitude trough to the west; a convergence/divergence dipole straddling the trough; and strong cross contour flow at the tropical base of the jet. Diagnostic budgets of vorticity, divergence, and kinetic energy are calculated to explain the evolution of the modelled plumes. Budgets describe the unforced (basic) state, forced plumes, forced cases with no plumes, and ECMWF analyzed plumes.

  13. Submarine Alkalic Lavas Around the Hawaiian Hotspot; Plume and Non-Plume Signatures Determined by Noble Gases

    NASA Astrophysics Data System (ADS)

    Hanyu, T.; Clague, D. A.; Kaneoka, I.; Dunai, T. J.; Davies, G. R.

    2004-12-01

    Noble gas isotopic ratios were determined for submarine alkalic volcanic rocks distributed around the Hawaiian islands to constrain the origin of such alkalic volcanism. Samples were collected by dredging or using submersibles from the Kauai Channel between Oahu and Kauai, north of Molokai, northwest of Niihau, Southwest Oahu, South Arch and North Arch volcanic fields. Sites located downstream from the center of the hotspot have 3He/4He ratios close to MORB at about 8 Ra, demonstrating that the magmas erupted at these sites had minimum contribution of volatiles from a mantle plume. In contrast, the South Arch, located upstream of the hotspot on the Hawaiian Arch, has 3He/4He ratios between 17 and 21 Ra, indicating a strong plume influence. Differences in noble gas isotopic characteristics between alkalic volcanism downstream and upstream of the hotspot imply that upstream volcanism contains incipient melts from an upwelling mantle plume, having primitive 3He/4He. In combination with lithophile element isotopic data, we conclude that the most likely source of the upstream magmatism is depleted asthenospheric mantle that has been metasomatised by incipient melt from a mantle plume. After major melt extraction from the mantle plume during production of magmas for the shield stage, the plume material is highly depleted in noble gases and moderately depleted in lithophile elements. Partial melting of the depleted mantle impregnated by melts derived from this volatile depleted plume source may explain the isotopic characteristics of the downstream alkalic magmatism.

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

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

    Zhao, Xin; Shin, Yung C.

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

  15. Modelling oil plumes from subsurface spills.

    PubMed

    Lardner, Robin; Zodiatis, George

    2017-11-15

    An oil plume model to simulate the behavior of oil from spills located at any given depth below the sea surface is presented, following major modifications to a plume model developed earlier by Malačič (2001) and drawing on ideas in a paper by Yapa and Zheng (1997). The paper presents improvements in those models and numerical testing of the various parameters in the plume model. The plume model described in this paper is one of the numerous modules of the well-established MEDSLIK oil spill model. The deep blowout scenario of the MEDEXPOL 2013 oil spill modelling exercise, organized by REMPEC, has been applied using the improved oil plume module of the MEDSLIK model and inter-comparison with results having the oil spill source at the sea surface are discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Experiments on point plumes in a rotating environment

    NASA Astrophysics Data System (ADS)

    Frank, Daria; Landel, Julien; Dalziel, Stuart; Linden, Paul

    2016-11-01

    Motivated by the Deepwater Horizon oil spill in the Gulf of Mexico we study the dynamics of point plumes in a stratified and homogeneous rotating environment. To this end, we conduct small-scale experiments in the laboratory on salt water and bubble plumes over a wide range of Rossby numbers. The rotation modifies the entrainment into the plume and also inhibits the lateral spreading of the plume fluid which leads to various instabilities in the flow. In particular, we focus on the plume behaviour in the near-source region (where the plume is dominated by the source conditions) and at intermediate water depths, e.g., lateral intrusions at the neutral buoyancy level in the stratified environment. One of the striking features in the rotating environment is the anticyclonic precession of the plume axis which leads to an enhanced dispersion of the plume fluid in the ambient and which is absent in the non-rotating system. In this talk, we present our experimental results and develop simple models to explain the observed plume dynamics.

  17. Detection of plumes at Redoubt and Etna volcanoes using the GPS SNR method

    NASA Astrophysics Data System (ADS)

    Larson, Kristine M.; Palo, Scott; Roesler, Carolyn; Mattia, Mario; Bruno, Valentina; Coltelli, Mauro; Fee, David

    2017-09-01

    Detection and characterization of volcanic eruptions is important both for public health and aircraft safety. A variety of ground sensors are used to monitor volcanic eruptions. Data from these ground sensors are subsequently incorporated into models that predict the movement of ash. Here a method to detect volcanic plumes using GPS signals is described. Rather than carrier phase data used by geodesists, the method takes advantage of attenuations in signal to noise ratio (SNR) data. Two datasets are evaluated: the 2009 Redoubt Volcano eruptions and the 2013/2015 eruptions at Mt. Etna. SNR-based eruption durations are compared with previously published seismic, infrasonic, and radar studies at Redoubt Volcano. SNR-based plume detections from Mt. Etna are compared with L-band radar and tremor observations. To place these SNR observations from Redoubt and Etna in context, a model of the propagation of GPS signals through both water/water vapor and tephra is developed. Neither water nor fine ash particles will produce the observed attenuation of GPS signals, while scattering caused by particles > 1 cm in diameter potentially could.

  18. Endometrial Ablation

    MedlinePlus

    ... or lighter levels. If ablation does not control heavy bleeding, further treatment or surgery may be needed. ... ablation is used to treat many causes of heavy bleeding. In most cases, women with heavy bleeding ...

  19. Geodynamic modelling of low-buoyancy thermo-chemical plumes

    NASA Astrophysics Data System (ADS)

    Dannberg, Juliane; Sobolev, Stephan

    2015-04-01

    The Earth's biggest magmatic events that form Large Igneous Provinces are believed to originate from massive melting when hot mantle plumes rising from the lowermost mantle reach the base of the lithosphere. Classical models of thermal mantle plumes predict a flattening of the plume head to a disk-like structure, a kilometer-scale surface uplift just before the initiation of LIPs and thin plume tails. However, there are seismic observations and paleo-topography data that are difficult to explain with this classical approach. Here, using numerical models, we show that the issue can be resolved if major mantle plumes are thermo-chemical rather than purely thermal. It has been suggested a long time ago that subducted oceanic crust could be recycled by mantle plumes; and based on geochemical data, they may contain up to 15-20% of this recycled material in the form of dense eclogite, which drastically decreases their buoyancy and makes it depth-dependent. We perform numerical experiments in a 3D spherical shell geometry to investigate the dynamics of the plume ascent, the interaction between plume- and plate-driven flow and the dynamics of melting in a plume head. For this purpose, we use the finite-element code ASPECT, which allows for complex temperature-, pressure- and composition-dependent material properties. Moreover, our models incorporate phase transitions (including melting) with the accompanying rheological and density changes, Clapeyron slopes and latent heat effects for both peridotite and eclogite, mantle compressibility and a strong temperature- and depth-dependent viscosity. We demonstrate that despite their low buoyancy, such plumes can rise through the whole mantle causing only negligible surface uplift. Conditions for this ascent are high plume volume and moderate lower mantle subadiabaticity. While high plume buoyancy results in plumes directly advancing to the base of the lithosphere, plumes with slightly lower buoyancy pond in a depth of 300-400 km

  20. Turbulent forces within river plumes affect spread

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Atreyee

    2012-08-01

    When rivers drain into oceans through narrow mouths, hydraulic forces squeeze the river water into buoyant plumes that are clearly visible in satellite images. Worldwide, river plumes not only disperse freshwater, sediments, and nutrients but also spread pollutants and organisms from estuaries into the open ocean. In the United States, the Columbia River—the largest river by volume draining into the Pacific Ocean from North America—generates a plume at its mouth that transports juvenile salmon and other fish into the ocean. Clearly, the behavior and spread of river plumes, such as the Columbia River plume, affect the nation's fishing industry as well as the global economy.

  1. Active Volcanic Plumes on Io

    NASA Image and Video Library

    1998-03-26

    This color image, acquired during NASA Galileo ninth orbit around Jupiter, shows two volcanic plumes on Io. One plume was captured on the bright limb or edge of the moon, erupting over a caldera volcanic depression named Pillan Patera.

  2. Eiffel Tower Plume

    NASA Image and Video Library

    2015-08-19

    This still image from an animation from NASA GSFC Solar Dynamics Observatory shows a single plume of plasma, many times taller than the diameter of Earth, spewing streams of particles for over two days Aug. 17-19, 2015 before breaking apart. At times, its shape resembled the Eiffel Tower. Other lesser plumes and streams of particles can be seen dancing above the solar surface as well. The action was observed in a wavelength of extreme ultraviolet light. http://photojournal.jpl.nasa.gov/catalog/PIA19875

  3. Chesapeake Bay plume dynamics from LANDSAT

    NASA Technical Reports Server (NTRS)

    Munday, J. C., Jr.; Fedosh, M. S.

    1981-01-01

    LANDSAT images with enhancement and density slicing show that the Chesapeake Bay plume usually frequents the Virginia coast south of the Bay mouth. Southwestern (compared to northern) winds spread the plume easterly over a large area. Ebb tide images (compared to flood tide images) show a more dispersed plume. Flooding waters produce high turbidity levels over the shallow northern portion of the Bay mouth.

  4. Laser ablation of single-crystalline silicon by radiation of pulsed frequency-selective fiber laser

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    We have studied the process of destruction of the surface of a single-crystalline silicon wafer scanned by the beam of a pulsed ytterbium-doped fiber laser radiation with a wavelength of λ = 1062 nm. It is established that the laser ablation can proceed without melting of silicon and the formation of a plasma plume. Under certain parameters of the process (radiation power, beam scan velocity, and beam overlap density), pronounced oxidation of silicon microparticles with the formation of a characteristic loose layer of fine powdered silicon dioxide has been observed for the first time. The range of lasing and beam scanning regimes in which the growth of SiO2 layer takes place is determined.

  5. PLUME-MoM 1.0: A new integral model of volcanic plumes based on the method of moments

    NASA Astrophysics Data System (ADS)

    de'Michieli Vitturi, M.; Neri, A.; Barsotti, S.

    2015-08-01

    In this paper a new integral mathematical model for volcanic plumes, named PLUME-MoM, is presented. The model describes the steady-state dynamics of a plume in a 3-D coordinate system, accounting for continuous variability in particle size distribution of the pyroclastic mixture ejected at the vent. Volcanic plumes are composed of pyroclastic particles of many different sizes ranging from a few microns up to several centimeters and more. A proper description of such a multi-particle nature is crucial when quantifying changes in grain-size distribution along the plume and, therefore, for better characterization of source conditions of ash dispersal models. The new model is based on the method of moments, which allows for a description of the pyroclastic mixture dynamics not only in the spatial domain but also in the space of parameters of the continuous size distribution of the particles. This is achieved by formulation of fundamental transport equations for the multi-particle mixture with respect to the different moments of the grain-size distribution. Different formulations, in terms of the distribution of the particle number, as well as of the mass distribution expressed in terms of the Krumbein log scale, are also derived. Comparison between the new moments-based formulation and the classical approach, based on the discretization of the mixture in N discrete phases, shows that the new model allows for the same results to be obtained with a significantly lower computational cost (particularly when a large number of discrete phases is adopted). Application of the new model, coupled with uncertainty quantification and global sensitivity analyses, enables the investigation of the response of four key output variables (mean and standard deviation of the grain-size distribution at the top of the plume, plume height and amount of mass lost by the plume during the ascent) to changes in the main input parameters (mean and standard deviation) characterizing the

  6. Charge structure in volcanic plumes: a comparison of plume properties predicted by an integral plume model to observations of volcanic lightning during the 2010 eruption of Eyjafjallajökull, Iceland.

    PubMed

    Woodhouse, Mark J; Behnke, Sonja A

    Observations of volcanic lightning made using a lightning mapping array during the 2010 eruption of Eyjafjallajökull allow the trajectory and growth of the volcanic plume to be determined. The lightning observations are compared with predictions of an integral model of volcanic plumes that includes descriptions of the interaction with wind and the effects of moisture. We show that the trajectory predicted by the integral model closely matches the observational data and the model well describes the growth of the plume downwind of the vent. Analysis of the lightning signals reveals information on the dominant charge structure within the volcanic plume. During the Eyjafjallajökull eruption both monopole and dipole charge structures were observed in the plume. By using the integral plume model, we propose the varying charge structure is connected to the availability of condensed water and low temperatures at high altitudes in the plume, suggesting ice formation may have contributed to the generation of a dipole charge structure via thunderstorm-style ice-based charging mechanisms, though overall this charging mechanism is believed to have had only a weak influence on the production of lightning.

  7. Fossil plume head beneath the Arabian lithosphere?

    NASA Astrophysics Data System (ADS)

    Stein, Mordechai; Hofmann, Albrecht W.

    1992-12-01

    Phanerozoic alkali basalts from Israel, which have erupted over the past 200 Ma, have isotopic compositions similar to PREMA ("prevalent mantle") with narrow ranges of initial ɛ Nd(T) = +3.9-+5.9; 87Sr/ 86Sr(T)= 0.70292-0.70334; 206Pb/ 204Pb(T)= 18.88-19.99; 207Pb/ 204Pb(T)= 15.58-15.70; and 208Pb/ 204Pb(T)= 38.42-39.57. Their Nb/U(43 ± 9) and Ce/Pb(26 ± 6) ratios are identical to those of normal oceanic basalts, demonstrating that the basalts are essentially free of crustal contamination. Overall, the basalts are chemically and isotopically indistinguishable from many ordinary plume basalts, but no plume track can be identified. We propose that these and other, similar, magmas from the Arabian plate originated from a "fossilized" head of a mantle plume, which was unable to penetrate the continental lithosphere and was therefore trapped and stored beneath it. The plume head was emplaced some time between the late Proterozoic crust formation and the initiation of the Phanerozoic magmatic cycles. Basalts from rift environments in other continental localities show similar geochemistry to that of the Arabian basalts and their sources may also represent fossil plume heads trapped below the continents. We suggest that plume heads are, in general, characterized by the PREMA isotopic mantle signature, because the original plume sources (which may have HIMU or EM-type composition) have been diluted by overlying mantle material, which has been entrained by the plume heads during ascent. On the Arabian plate, rifting and thinning of the lithosphere caused partial melting of the stored plume, which led to periodic volcanism. In the late Cenozoic, the lithosphere broke up and the Red Sea opened. N-MORB tholeiites are now erupting in the central trough of the Red Sea, where the lithosphere has moved apart and the fossil plume has been exhausted, whereas E-MORBs are erupting in the northern and southern troughs, still tapping the plume reservoir. Fossil plumes, which are

  8. Plume Characteristics of the Busek 600 W Hall Thruster

    DTIC Science & Technology

    2006-07-12

    that can then be applied to estimate the effect of the energetic plume on complex spacecraft geometries. Early measurement of plume properties, such...produced a measurable effect on ion current density and plume divergence, experimentally showing an increase or decrease of ±15-20%. Ionic energy...can then be applied to estimate the effect of the energetic plume on complex spacecraft geometries. Early measurement of plume properties, such as plume

  9. Plume Tracker: A New Toolkit for the Mapping of Volcanic Plumes with Multispectral Thermal Infrared Remote Sensing

    NASA Astrophysics Data System (ADS)

    Realmuto, V. J.; Baxter, S.; Webley, P. W.

    2011-12-01

    Plume Tracker is the next generation of interactive plume mapping tools pioneered by MAP_SO2. First developed in 1995, MAP_SO2 has been used to study plumes at a number of volcanoes worldwide with data acquired by both airborne and space-borne instruments. The foundation of these tools is a radiative transfer (RT) model, based on MODTRAN, which we use as the forward model for our estimation of ground temperature and sulfur dioxide concentration. Plume Tracker retains the main functions of MAP_SO2, providing interactive tools to input radiance measurements and ancillary data, such as profiles of atmospheric temperature and humidity, to the retrieval procedure, generating the retrievals, and visualizing the resulting retrievals. Plume Tracker improves upon MAP_SO2 in the following areas: (1) an RT model based on an updated version of MODTRAN, (2) a retrieval procedure based on maximizing the vector projection of model spectra onto observed spectra, rather than minimizing the least-squares misfit between the model and observed spectra, (3) an ability to input ozone profiles to the RT model, (4) increased control over the vertical distribution of the atmospheric gas species used in the model, (5) a standard programmatic interface to the RT model code, based on the Component Object Model (COM) interface, which will provide access to any programming language that conforms to the COM standard, and (6) a new binning algorithm that decreases running time by exploiting spatial redundancy in the radiance data. Based on our initial testing, the binning algorithm can reduce running time by an order of magnitude. The Plume Tracker project is a collaborative effort between the Jet Propulsion Laboratory and Geophysical Institute (GI) of the University of Alaska-Fairbanks. Plume Tracker is integrated into the GI's operational plume dispersion modeling system and will ingest temperature and humidity profiles generated by the Weather Research and Forecasting model, together with

  10. Dynamics of thermal plumes in three-dimensional isoviscous thermal convection

    NASA Astrophysics Data System (ADS)

    Zhong, Shijie

    2005-07-01

    The dynamics of mantle plumes are important for understanding intraplate volcanism and heat transfer in the mantle. Using 3-D numerical models and scaling analyses, we investigated the controls of convective vigour or Ra (Rayleigh number) on the dynamics of thermal plumes in isoviscous and basal heating thermal convection. We examined the Ra dependence of plume number, plume spacing, plume vertical velocity and plume radius. We found that plume number does not increase monotonically with Ra. At relatively small Ra(<=106), plume number is insensitive to Ra. For 3 × 106<=Ra<= 3 × 107, plume number scales as Ra0.31 and plume spacing λ~Ra-0.16~δ1/2, where δ is the thickness of the thermal boundary layer. However, for larger Ra(~108) plume number and plume spacing again become insensitive to Ra. This indicates that the box depth poses a limit on plume spacing and plume number. We demonstrate from both scaling analyses and numerical experiments that the scaling exponents for plume number, n, heat flux, β, and average velocity on the bottom boundary, v, satisfy n= 4β- 2v. Our scaling analyses also suggest that vertical velocity in upwelling plumes Vup~Ra2(1-n+β/2)/3 and that plume radius Rup~Ra(β-1-n/2)/3, which differ from the scalings for the bottom boundary velocity and boundary layer thickness.

  11. The role of unsteady buoyancy flux on transient eruption plume velocity structure and evolution

    NASA Astrophysics Data System (ADS)

    Chojnicki, K. N.; Clarke, A. B.; Phillips, J. C.

    2010-12-01

    Volcanic vent exit velocities, eruption column velocity profiles, and atmospheric entrainment are important parameters that control the evolution of explosive volcanic eruption plumes. New data sets tracking short-term variability in such parameters are becoming more abundant in volcanology and are being used to indirectly estimate eruption source conditions such vent flux, material properties of the plume, and source mechanisms. However, inadequate theory describing the relationships between time-varying source fluxes and evolution of unsteady turbulent flows such as eruption plumes, limits the interpretation potential of these data sets. In particular, the relative roles of gas-thrust and buoyancy in volcanic explosions is known to generate distinct differences in the ascent dynamics. Here we investigate the role of initial buoyancy in unsteady, short-duration eruption dynamics through scaled laboratory experiments and provide an empirical description of the relationship between unsteady source flux and plume evolution. The experiments involved source fluids of various densities (960-1000 kg/m3) injected, with a range of initial momentum and buoyancy, into a tank of fresh water through a range of vent diameters (3-15 mm). A scaled analysis was used to determine the fundamental parameters governing the evolution of the laboratory plumes as a function of unsteady source conditions. The subsequent model can be applied to predict flow front propagation speeds, and maximum flow height and width of transient volcanic eruption plumes which can not be adequately described by existing steady approximations. In addition, the model describes the relative roles of momentum or gas-thrust and buoyancy in plume motion which is suspected to be a key parameter in quantitatively defining explosive eruption style. The velocity structure of the resulting flows was measured using the Particle Image Velocimetry (PIV) technique in which velocity vector fields were generated from

  12. Highly buoyant bent-over plumes in a boundary layer

    NASA Astrophysics Data System (ADS)

    Tohidi, Ali; Kaye, Nigel B.

    2016-04-01

    Highly buoyant plumes, such as wildfire plumes, in low to moderate wind speeds have initial trajectories that are steeper than many industrial waste plumes. They will rise further into the atmosphere before bending significantly. In such cases the plume's trajectory will be influenced by the vertical variation in horizontal velocity of the atmospheric boundary layer. This paper examined the behavior of a plume in an unstratified environment with a power-law ambient velocity profile. Examination of previously published experimental measurements of plume trajectory show that inclusion of the boundary layer velocity profile in the plume model often provides better predictions of the plume trajectory compared to algebraic expressions developed for uniform flow plumes. However, there are many cases in which uniform velocity profile algebraic expressions are as good as boundary layer models. It is shown that it is only important to model the role of the atmospheric boundary layer velocity profile in cases where either the momentum length (square root of source momentum flux divided by the reference wind speed) or buoyancy length (buoyancy flux divided by the reference wind speed cubed) is significantly greater than the plume release height within the boundary layer. This criteria is rarely met with industrial waste plumes, but it is important in modeling wildfire plumes.

  13. PLUME and research sotware

    NASA Astrophysics Data System (ADS)

    Baudin, Veronique; Gomez-Diaz, Teresa

    2013-04-01

    The PLUME open platform (https://www.projet-plume.org) has as first goal to share competences and to value the knowledge of software experts within the French higher education and research communities. The project proposes in its platform the access to more than 380 index cards describing useful and economic software for this community, with open access to everybody. The second goal of PLUME focuses on to improve the visibility of software produced by research laboratories within the higher education and research communities. The "development-ESR" index cards briefly describe the main features of the software, including references to research publications associated to it. The platform counts more than 300 cards describing research software, where 89 cards have an English version. In this talk we describe the theme classification and the taxonomy of the index cards and the evolution with new themes added to the project. We will also focus on the organisation of PLUME as an open project and its interests in the promotion of free/open source software from and for research, contributing to the creation of a community of shared knowledge.

  14. Laser ablation-miniature mass spectrometer for elemental and isotopic analysis of rocks.

    PubMed

    Sinha, M P; Neidholdt, E L; Hurowitz, J; Sturhahn, W; Beard, B; Hecht, M H

    2011-09-01

    A laser ablation-miniature mass spectrometer (LA-MMS) for the chemical and isotopic measurement of rocks and minerals is described. In the LA-MMS method, neutral atoms ablated by a pulsed laser are led into an electron impact ionization source, where they are ionized by a 70 eV electron beam. This results in a secondary ion pulse typically 10-100 μs wide, compared to the original 5-10 ns laser pulse duration. Ions of different masses are then spatially dispersed along the focal plane of the magnetic sector of the miniature mass spectrometer (MMS) and measured in parallel by a modified CCD array detector capable of detecting ions directly. Compared to conventional scanning techniques, simultaneous measurement of the ion pulse along the focal plane effectively offers a 100% duty cycle over a wide mass range. LA-MMS offers a more quantitative assessment of elemental composition than techniques that detect ions directly generated by the ablation process because the latter can be strongly influenced by matrix effects that vary with the structure and geometry of the surface, the wavelength of the laser beam, and the not well characterized ionization efficiencies of the elements in the process. The above problems attendant to the direct ion analysis has been minimized in the LA-MMS by analyzing the ablated neutral species after their post-ionization by electron impaction. These neutral species are much more abundant than the directly ablated ions in the ablated vapor plume and are, therefore, expected to be characteristic of the chemical composition of the solid. Also, the electron impact ionization of elements is well studied and their ionization cross sections are known and easy to find in databases. Currently, the LA-MMS limit of detection is 0.4 wt.%. Here we describe LA-MMS elemental composition measurements of various minerals including microcline, lepidolite, anorthoclase, and USGS BCR-2G samples. The measurements of high precision isotopic ratios including (41)K

  15. Quantifying the North Pacific silica plume

    NASA Astrophysics Data System (ADS)

    Johnson, H. P.; Hautala, S. L.; Bjorklund, T. A.; Zarnetske, M. R.

    2006-05-01

    New hydrostations plus a comprehensive compilation of existing data have allowed us to characterize the dissolved silica plume located at midwater depths in the North Pacific. The North Pacific silica plume is a global-scale anomaly, extending from the North American continental margin in the east to beyond the Hawaii-Emperor seamount chain in the west. Inventory of the plume between 2000 and 3000 m depth indicates that it contains 164 Tmols (164 × 1012 mols) of anomalous dissolved silica and is maintained by a horizontal flux of approximately 1.5 Tmols/yr from the east. The source region of this plume has been previously suggested to be Cascadia Basin in the NE Pacific. Biochemical and geothermal processes within this small region can produce approximately one third of the required flux, but the majority of silica contained within the North Pacific plume may originate in crustal fluid venting from the warm upper basement aquifer that underlies the easternmost Pacific plate.

  16. Plume meander and dispersion in a stable boundary layer

    NASA Astrophysics Data System (ADS)

    Hiscox, April L.; Miller, David R.; Nappo, Carmen J.

    2010-11-01

    Continuous lidar measurements of elevated plume dispersion and corresponding micrometeorology data are analyzed to establish the relationship between plume behavior and nocturnal boundary layer dynamics. Contrasting nights of data from the JORNADA field campaign in the New Mexico desert are analyzed. The aerosol lidar measurements were used to separate the plume diffusion (plume spread) from plume meander (displacement). Mutiresolution decomposition was used to separate the turbulence scale (<90 s) from the submesoscale (>90 s). Durations of turbulent kinetic energy stationarity and the wind steadiness were used to characterize the local scale and submesoscale turbulence. Plume meander, driven by submesoscale wind motions, was responsible for most of the total horizontal plume dispersion in weak and variable winds and strong stability. This proportion was reduced in high winds (i.e., >4 m s-1), weakly stable conditions but remained the dominant dispersion mechanism. The remainder of the plume dispersion in all cases was accounted for by internal spread of the plume, which is a small eddy diffusion process driven by turbulence. Turbulence stationarity and the wind steadiness are demonstrated to be closely related to plume diffusion and plume meander, respectively.

  17. Ridge suction drives plume-ridge interactions

    NASA Astrophysics Data System (ADS)

    Niu, Y.; Hékinian, R.

    2003-04-01

    Deep-sourced mantle plumes, if existing, are genetically independent of plate tectonics. When the ascending plumes approach lithospheric plates, interactions between the two occur. Such interactions are most prominent near ocean ridges where the lithosphere is thin and the effect of plumes is best revealed. While ocean ridges are mostly passive features in terms of plate tectonics, they play an active role in the context of plume-ridge interactions. This active role is a ridge suction force that drives asthenospheric mantle flow towards ridges because of material needs to form the ocean crust at ridges and lithospheric mantle in the vicinity of ridges. This ridge suction force increases with increasing plate separation rate because of increased material demand per unit time. As the seismic low-velocity zone atop the asthenosphere has the lowest viscosity that increases rapidly with depth, the ridge-ward asthenospheric flow is largely horizontal beneath the lithosphere. Recognizing that plume materials have two components with easily-melted dikes/veins enriched in volatiles and incompatible elements dispersed in the more refractory and depleted peridotitic matrix, geochemistry of some seafloor volcanics well illustrates that plume-ridge interactions are consequences of ridge-suction-driven flow of plume materials, which melt by decompression because of lithospheric thinning towards ridges. There are excellent examples: 1. The decreasing La/Sm and increasing MgO and CaO/Al_2O_3 in Easter Seamount lavas from Salas-y-Gomez Islands to the Easter Microplate East rift zone result from progressive decompression melting of ridge-ward flowing plume materials. 2. The similar geochemical observations in lavas along the Foundation hotline towards the Pacific-Antarctic Ridge result from the same process. 3. The increasing ridge suction force with increasing spreading rate explains why the Iceland plume has asymmetric effects on its neighboring ridges: both topographic and

  18. Transmission geometry laser ablation into a non-contact liquid vortex capture probe for mass spectrometry imaging.

    PubMed

    Ovchinnikova, Olga S; Bhandari, Deepak; Lorenz, Matthias; Van Berkel, Gary J

    2014-08-15

    Capture of material from a laser ablation plume into a continuous flow stream of solvent provides the means for uninterrupted sampling, transport and ionization of collected material for coupling with mass spectral analysis. Reported here is the use of vertically aligned transmission geometry laser ablation in combination with a new non-contact liquid vortex capture probe coupled with electrospray ionization for spot sampling and chemical imaging with mass spectrometry. A vertically aligned continuous flow liquid vortex capture probe was positioned directly underneath a sample surface in a transmission geometry laser ablation (355 nm, 10 Hz, 7 ns pulse width) set up to capture into solution the ablated material. The outlet of the vortex probe was coupled to the Turbo V™ ion source of an AB SCIEX TripleTOF 5600+ mass spectrometer. System operation and performance metrics were tested using inked patterns and thin tissue sections. Glass slides and slides designed especially for laser capture microdissection, viz., DIRECTOR(®) slides and PEN 1.0 (polyethylene naphthalate) membrane slides, were used as sample substrates. The estimated capture efficiency of laser-ablated material was 24%, which was enabled by the use of a probe with large liquid surface area (~2.8 mm(2) ) and with gravity to help direct ablated material vertically down towards the probe. The swirling vortex action of the liquid surface potentially enhanced capture and dissolution not only of particulates, but also of gaseous products of the laser ablation. The use of DIRECTOR(®) slides and PEN 1.0 (polyethylene naphthalate) membrane slides as sample substrates enabled effective ablation of a wide range of sample types (basic blue 7, polypropylene glycol, insulin and cyctochrome c) without photodamage using a UV laser. Imaging resolution of about 6 µm was demonstrated for stamped ink on DIRECTOR(®) slides based on the ability to distinguish features present both in the optical and in the chemical

  19. Particle dynamics during nanoparticle synthesis by laser ablation in a background gas

    NASA Astrophysics Data System (ADS)

    Nakata, Yoshiki; Muramoto, Junichi; Okada, Tatsuo; Maeda, Mitsuo

    2002-02-01

    Particle dynamics during Si nanoparticle synthesis in a laser-ablation plume in different background gases were investigated by laser-spectroscopic imaging techniques. Two-dimensional laser induced fluorescence and ultraviolet Rayleigh scattering techniques were used to visualize the spatial distribution of the Si atoms and nanoparticles grown, respectively. We have developed a visualization technique called re-decomposition laser-induced fluorescence to observe small nanoparticles (hereafter called clusters) which are difficult to observe by the conventional imaging techniques. In this article, the whole process of nanoparticle synthesis in different background gases of He, Ne, Ar, N2 and O2 was investigated by these techniques. In He, Ne, Ar and N2 background gases at 10 Torr, the clustering of the Si atoms started 200, 250, 300 and 800 μs after ablation, respectively. The growth rate of the clusters in He background gas was much larger than that in the other gases. The spatial distributions of the Si nanoparticles were mushroom like in He, N2 and O2, and column like in Ne and Ar. It is thought that the difference in distribution was caused by differences in the flow characteristics of the background gases, which would imply that the viscosity of the background gas is one of the main governing parameters.

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

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

    Tanaka, Toshihiro, E-mail: toshihir@bf6.so-net.ne.jp; Westphal, Saskia, E-mail: swestphal@ukaachen.de; Isfort, Peter, E-mail: isfort@hia.rwth-aachen.de

    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 MWmore » 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.« less

  1. Three Dimensional Volcanic Plume Simulations on Early Mars

    NASA Astrophysics Data System (ADS)

    Fisher, M. A.; Kobs-Nawotniak, S. E.

    2016-12-01

    Current explosive volcanic plume models for early Mars are thought to overestimate plume height by tens of kilometers. They are based on 1D empirical terrestrial plume models, which determine plume rise using Morton-style convection. Not only do these models fail to account for turbulent mixing processes, but the Martian versions also violate assumptions regarding the speed of sound, radial expansion, and availability of ambient air for entrainment. Since volcanically derived volatiles are hypothesized to have increased early Martian warming, it is vital to understand how high these volatiles can be injected into the atmosphere. Active Tracer High-resolution Atmospheric Model (ATHAM; Oberhuber et al., 1998) is a 3D plume simulator that circumvents the underlying assumptions of the current Martian plume models by solving the Navier-Stokes equations. Martian-ATHAM (M-ATHAM) simulates Martian volcanic eruptions by replacing terrestrial planetary and atmospheric conditions with those appropriate for early Mars. In particular we evaluate three different atmospheric compositions with unique temperature and density profiles: 99.5% CO2/0.5% SO2 and 85% CO2/15% H2 representing a "warm and wet" climate and 100% CO2 representing a "cold and wet" climate. We evaluated for mass eruption rates from 10^3 kg/s to 10^10 kg/s using the Idaho National Laboratory's supercomputer Falcon in order determine what conditions produced stable eruption columns. Of the three different atmospheric compositions, 100% CO2 and 99.5% CO2/0.5% SO2 produced stable plumes for the same mass eruption rates whereas the 85% CO2/15% H2 atmosphere produced stable plumes for a slightly higher range of mass eruption rates. The tallest plumes were produced by 85% CO2/15% H2 atmosphere, producing plumes 5% taller than the revised empirical models, suggesting closer agreement than previously assumed under certain conditions. In comparison to terrestrial plumes, all early Martian plumes needed higher mass

  2. Benign thyroid nodule unresponsive to radiofrequency ablation treated with laser ablation: a case report.

    PubMed

    Oddo, Silvia; Balestra, Margherita; Vera, Lara; Giusti, Massimo

    2018-05-11

    Radiofrequency ablation and laser ablation are safe and effective techniques for reducing thyroid nodule volume, neck symptoms, and cosmetic complaints. Therapeutic success is defined as a nodule reduction > 50% between 6 and 12 months after the procedure, but a percentage of nodules inexplicably do not respond to thermal ablation. We describe the case of a young Caucasian woman with a solid benign thyroid nodule who refused surgery and who had undergone radiofrequency ablation in 2013. The nodule did not respond in terms of either volume reduction or improvement in neck symptoms. After 2 years, given the patient's continued refusal of thyroidectomy, we proposed laser ablation. The nodule displayed a significant volume reduction (- 50% from radiofrequency ablation baseline volume, - 57% from laser ablation baseline), and the patient reported a significant improvement in neck symptoms (from 6/10 to 1/10 on a visual analogue scale). We conjecture that some benign thyroid nodules may be intrinsically resistant to necrosis when one specific ablation technique is used, but may respond to another technique. To the best of our knowledge, this is the first description of the effect of performing a different percutaneous ablation technique in a nodule that does not respond to radiofrequency ablation.

  3. Stationary Plasma Thruster Plume Characteristics

    NASA Technical Reports Server (NTRS)

    Myers, Roger M.; Manzella, David H.

    1994-01-01

    Stationary Plasma Thrusters (SPT's) are being investigated for application to a variety of near-term missions. This paper presents the results of a preliminary study of the thruster plume characteristics which are needed to assess spacecraft integration requirements. Langmuir probes, planar probes, Faraday cups, and a retarding potential analyzer were used to measure plume properties. For the design operating voltage of 300 V the centerline electron density was found to decrease from approximately 1.8 x 10 exp 17 cubic meters at a distance of 0.3 m to 1.8 X 10 exp 14 cubic meters at a distance of 4 m from the thruster. The electron temperature over the same region was between 1.7 and 3.5 eV. Ion current density measurements showed that the plume was sharply peaked, dropping by a factor of 2.6 within 22 degrees of centerline. The ion energy 4 m from the thruster and 15 degrees off-centerline was approximately 270 V. The thruster cathode flow rate and facility pressure were found to strongly affect the plume properties. In addition to the plume measurements, the data from the various probe types were used to assess the impact of probe design criteria

  4. A model of early formation of uranium molecular oxides in laser-ablated plasmas

    NASA Astrophysics Data System (ADS)

    Finko, Mikhail S.; Curreli, Davide; Weisz, David G.; Crowhurst, Jonathan C.; Rose, Timothy P.; Koroglu, Batikan; Radousky, Harry B.; Armstrong, Michael R.

    2017-12-01

    In this work, we present a newly constructed U x O y reaction mechanism that consists of 30 reaction channels (21 of which are reversible channels) for 11 uranium molecular species (including ions). Both the selection of reaction channels and calculation of corresponding rate coefficients is accomplished via a comprehensive literature review and application of basic reaction rate theory. The reaction mechanism is supplemented by a detailed description of oxygen plasma chemistry (19 species and 142 reaction channels) and is used to model an atmospheric laser ablated uranium plume via a 0D (global) model. The global model is used to analyze the evolution of key uranium molecular species predicted by the reaction mechanism, and the initial stage of formation of uranium oxide species.

  5. Nonthermal ablation of deep brain targets: A simulation study on a large animal model

    PubMed Central

    Top, Can Barış; White, P. Jason; McDannold, Nathan J.

    2016-01-01

    Purpose: Thermal ablation with transcranial MRI-guided focused ultrasound (FUS) is currently limited to central brain targets because of heating and other beam effects caused by the presence of the skull. Recently, it was shown that it is possible to ablate tissues without depositing thermal energy by driving intravenously administered microbubbles to inertial cavitation using low-duty-cycle burst sonications. A recent study demonstrated that this ablation method could ablate tissue volumes near the skull base in nonhuman primates without thermally damaging the nearby bone. However, blood–brain disruption was observed in the prefocal region, and in some cases, this region contained small areas of tissue damage. The objective of this study was to analyze the experimental model with simulations and to interpret the cause of these effects. Methods: The authors simulated prior experiments where nonthermal ablation was performed in the brain in anesthetized rhesus macaques using a 220 kHz clinical prototype transcranial MRI-guided FUS system. Low-duty-cycle sonications were applied at deep brain targets with the ultrasound contrast agent Definity. For simulations, a 3D pseudospectral finite difference time domain tool was used. The effects of shear mode conversion, focal steering, skull aberrations, nonlinear propagation, and the presence of skull base on the pressure field were investigated using acoustic and elastic wave propagation models. Results: The simulation results were in agreement with the experimental findings in the prefocal region. In the postfocal region, however, side lobes were predicted by the simulations, but no effects were evident in the experiments. The main beam was not affected by the different simulated scenarios except for a shift of about 1 mm in peak position due to skull aberrations. However, the authors observed differences in the volume, amplitude, and distribution of the side lobes. In the experiments, a single element passive

  6. Ambient infrared laser ablation mass spectrometry (AIRLAB-MS) of live plant tissue with plume capture by continuous flow solvent probe.

    PubMed

    O'Brien, Jeremy T; Williams, Evan R; Holman, Hoi-Ying N

    2015-03-03

    A new experimental setup for spatially resolved ambient infrared laser ablation-mass spectrometry (AIRLAB-MS) that uses an infrared microscope with an infinity-corrected reflective objective and a continuous flow solvent probe coupled to a Fourier transform ion cyclotron resonance mass spectrometer is described. The efficiency of material transfer from the sample to the electrospray ionization emitter was determined using glycerol/methanol droplets containing 1 mM nicotine and is ∼50%. This transfer efficiency is significantly higher than values reported for similar techniques. Laser desorption does not induce fragmentation of biomolecules in droplets containing bradykinin, leucine enkephalin and myoglobin, but loss of the heme group from myoglobin occurs as a result of the denaturing solution used. An application of AIRLAB-MS to biological materials is demonstrated for tobacco leaves. Chemical components are identified from the spatially resolved mass spectra of the ablated plant material, including nicotine and uridine. The reproducibility of measurements made using AIRLAB-MS on plant material was demonstrated by the ablation of six closely spaced areas (within 2 × 2 mm) on a young tobacco leaf, and the results indicate a standard deviation of <10% in the uridine signal obtained for each area. The spatial distribution of nicotine was measured for selected leaf areas and variation in the relative nicotine levels (15-100%) was observed. Comparative analysis of the nicotine distribution was demonstrated for two tobacco plant varieties, a genetically modified plant and its corresponding wild-type, indicating generally higher nicotine levels in the mutant.

  7. 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.

  8. Effects of NOx control and plume mixing on nighttime chemical processing of plumes from coal-fired power plants

    NASA Astrophysics Data System (ADS)

    Brown, Steven S.; Dubé, William P.; Karamchandani, Prakash; Yarwood, Greg; Peischl, Jeff; Ryerson, Thomas B.; Neuman, J. Andrew; Nowak, John B.; Holloway, John S.; Washenfelder, Rebecca A.; Brock, Charles A.; Frost, Gregory J.; Trainer, Michael; Parrish, David D.; Fehsenfeld, Frederick C.; Ravishankara, A. R.

    2012-04-01

    Coal-fired electric power plants produce a large fraction of total U.S. NOx emissions, but NOx from this sector has been declining in the last decade owing to installation of control technology. Nighttime aircraft intercepts of plumes from two different Texas power plants (Oklaunion near Wichita Falls and W. A. Parish near Houston) with different control technologies demonstrate the effect of these reductions on nighttime NOxoxidation rates. The analysis shows that the spatial extent of nighttime-emitted plumes to be quite limited and that mixing of highly concentrated plume NOx with ambient ozone is a determining factor for its nighttime oxidation. The plume from the uncontrolled plant had full titration of ozone through 74 km/2.4 h of downwind transport that suppressed nighttime oxidation of NO2 to higher oxides of nitrogen across the majority of the plume. The plume from the controlled plant did not have sufficient NOx to titrate background ozone, which led to rapid nighttime oxidation of NO2 during downwind transport. A plume model that includes horizontal mixing and nighttime chemistry reproduces the observed structures of the nitrogen species in the plumes from the two plants. The model shows that NOx controls not only reduce the emissions directly but also lead to an additional overnight NOx loss of 36-44% on average. The maximum reduction for 12 h of transport in darkness was 73%. The results imply that power plant NOxemissions controls may produce a larger than linear reduction in next-day, downwind ozone production following nighttime transport.

  9. Femtosecond laser ablation of dentin and enamel: relationship between laser fluence and ablation efficiency.

    PubMed

    Chen, Hu; Liu, Jing; Li, Hong; Ge, Wenqi; Sun, Yuchun; Wang, Yong; Lü, Peijun

    2015-02-01

    The objective was to study the relationship between laser fluence and ablation efficiency of a femtosecond laser with a Gaussian-shaped pulse used to ablate dentin and enamel for prosthodontic tooth preparation. A diode-pumped thin-disk femtosecond laser with wavelength of 1025 nm and pulse width of 400 fs was used for the ablation of dentin and enamel. The laser spot was guided in a line on the dentin and enamel surfaces to form a groove-shaped ablation zone under a series of laser pulse energies. The width and volume of the ablated line were measured under a three-dimensional confocal microscope to calculate the ablation efficiency. Ablation efficiency for dentin reached a maximum value of 0.020 mm3∕J when the laser fluence was set at 6.51 J∕cm2. For enamel, the maximum ablation efficiency was 0.009 mm3∕J at a fluence of 7.59 J∕cm2.Ablation efficiency of the femtosecond laser on dentin and enamel is closely related to the laser fluence and may reach a maximum when the laser fluence is set to an appropriate value. © 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)

  10. Visualising the procedures in the influence of water on the ablation of dental hard tissue with erbium:yttrium-aluminium-garnet and erbium, chromium:yttrium-scandium-gallium-garnet laser pulses.

    PubMed

    Mir, Maziar; Gutknecht, Norbert; Poprawe, Reinhart; Vanweersch, Leon; Lampert, Friedrich

    2009-05-01

    The exact mechanism of the ablation of tooth hard tissue with most common wavelengths, which are 2,940 nm and 2,780 nm, is not yet clear. There are several different theories, but none of them has yet been established. Concepts and methods of looking at these mechanisms have been based on heat formation and transformation, and mathematical calculations evaluating the outcome of ablation, such as looking at the shape of cuts. This study provides a new concept, which is the monitoring of the direct interactions between laser light, water and enamel, with a high-speed camera. For this purpose, both the above-mentioned wavelengths were examined. Bovine anterior teeth were prepared as thin slices. Each imaged slice had a thickness close to that of the beam diameter so that the ablation effect could be shown in two dimensional pictures. The single images were extracted from the video-clips and then were animated. The following steps, explaining the ablation procedures during each pulse, were seen and reported: (1) low-output energy intensity in the first pulses that did not lead to an ablative effect; (2) bubble formation with higher output energy density; (3) the tooth surface during the pulse was covered with the plume of vapour (comparable with a cloud), and the margins of ablation on the tooth were not clear; (4) when the vapour bubble (cloud) was collapsing, an additional ablative process at the surface could be seen.

  11. On the elemental analysis of different cigarette brands using laser induced breakdown spectroscopy and laser-ablation time of flight mass spectrometry

    NASA Astrophysics Data System (ADS)

    Ahmed, Nasar; Umar, Zeshan A.; Ahmed, Rizwan; Aslam Baig, M.

    2017-10-01

    We present qualitative and quantitative analysis of the trace elements present in different brands of tobacco available in Pakistan using laser induced breakdown spectroscopy (LIBS) and Laser ablation Time of Flight Mass Spectrometer (LA-TOFMS). The compositional analysis using the calibration free LIBS technique is based on the observed emission spectra of the laser produced plasma plume whereas the elemental composition analysis using LA-TOFMS is based on the mass spectra of the ions produced by laser ablation. The optical emission spectra of these samples contain spectral lines of calcium, magnesium, sodium, potassium, silicon, strontium, barium, lithium and aluminum with varying intensities. The corresponding mass spectra of the elements were detected in LA-TOF-MS with their composition concentration. The analysis of different brands of cigarettes demonstrates that LIBS coupled with a LA-TOF-MS is a powerful technique for the elemental analysis of the trace elements in any solid sample.

  12. Winds and the orientation of a coastal plane estuary plume

    NASA Astrophysics Data System (ADS)

    Xia, Meng; Xie, Lian; Pietrafesa, Leonard J.

    2010-10-01

    Based on a calibrated coastal plane estuary plume model, ideal model hindcasts of estuary plumes are used to describe the evolution of the plume pattern in response to river discharge and local wind forcing by selecting a typical partially mixed estuary (the Cape Fear River Estuary or CFRE). With the help of an existing calibrated plume model, as described by Xia et al. (2007), simulations were conducted using different parameters to evaluate the plume behavior type and its change associated with the variation of wind forcing and river discharge. The simulations indicate that relatively moderate winds can mechanically reverse the flow direction of the plume. Downwelling favorably wind will pin the plume to the coasts while the upwelling plume could induce plume from the left side to right side in the application to CFRE. It was found that six major types of plumes may occur in the estuary and in the corresponding coastal ocean. To better understand these plumes in the CFRE and other similar river estuary systems, we also investigated how the plumes transition from one type to another. Results showed that wind direction, wind speed, and sometimes river discharge contribute to plume transitions.

  13. Localization of gaps during redo ablations of paroxysmal atrial fibrillation: Preferential patterns depending on the choice of cryoballoon ablation or radiofrequency ablation for the initial procedure.

    PubMed

    Galand, Vincent; Pavin, Dominique; Behar, Nathalie; Auffret, Vincent; Fénéon, Damien; Behaghel, Albin; Daubert, Jean-Claude; Mabo, Philippe; Martins, Raphaël P

    2016-11-01

    Pulmonary vein (PV) isolation, using cryoballoon or radiofrequency ablation, is the cornerstone therapy for symptomatic paroxysmal atrial fibrillation (AF) refractory to antiarrhythmic drugs. One-third of the patients have recurrences, mainly due to PV reconnections. To describe the different locations of reconnection sites in patients who had previously undergone radiofrequency or cryoballoon ablation, and to compare the characteristics of the redo procedures in both instances. Demographic data and characteristics of the initial ablation (cryoballoon or radiofrequency) were collected. Number and localization of reconduction gaps, and redo characteristics were reviewed. Seventy-four patients scheduled for a redo ablation of paroxysmal AF were included; 38 had been treated by radiofrequency ablation and 36 by cryoballoon ablation during the first procedure. For the initial ablation, procedural and fluoroscopy times were significantly shorter for cryoballoon ablation (147.8±52.6min vs. 226.6±64.3min [P<0.001] and 37.0±17.7min vs. 50.8±22.7min [P=0.005], respectively). Overall, an identical number of gaps was found during redo procedures of cryoballoon and radiofrequency ablations. However, a significantly higher number of gaps were located in the right superior PV for patients first ablated with radiofrequency (0.9±1.0 vs. 0.5±0.9; P=0.009). Gap localization displayed different patterns. Although not significant, redo procedures of cryoballoon ablation were slightly shorter and needed shorter durations of radiofrequency to achieve PV isolation. During redo procedures, gap localization pattern is different for patients first ablated with cryoballoon or radiofrequency ablation, and right superior PV reconnections occur more frequently after radiofrequency ablation. Redo ablation of a previous cryoballoon ablation appears to be easier. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  14. Galileo observations of volcanic plumes on Io

    USGS Publications Warehouse

    Geissler, P.E.; McMillan, M.T.

    2008-01-01

    Io's volcanic plumes erupt in a dazzling variety of sizes, shapes, colors and opacities. In general, the plumes fall into two classes, representing distinct source gas temperatures. Most of the Galileo imaging observations were of the smaller, more numerous Prometheus-type plumes that are produced when hot flows of silicate lava impinge on volatile surface ices of SO2. Few detections were made of the giant, Pele-type plumes that vent high temperature, sulfur-rich gases from the interior of Io; this was partly because of the insensitivity of Galileo's camera to ultraviolet wavelengths. Both gas and dust spout from plumes of each class. Favorably located gas plumes were detected during eclipse, when Io was in Jupiter's shadow. Dense dust columns were imaged in daylight above several Prometheus-type eruptions, reaching heights typically less than 100 km. Comparisons between eclipse observations, sunlit images, and the record of surface changes show that these optically thick dust columns are much smaller in stature than the corresponding gas plumes but are adequate to produce the observed surface deposits. Mie scattering calculations suggest that these conspicuous dust plumes are made up of coarse grained “ash” particles with radii on the order of 100 nm, and total masses on the order of 106 kg per plume. Long exposure images of Thor in sunlight show a faint outer envelope apparently populated by particles small enough to be carried along with the gas flow, perhaps formed by condensation of sulfurous “snowflakes” as suggested by the plasma instrumentation aboard Galileo as it flew through Thor's plume [Frank, L.A., Paterson, W.R., 2002. J. Geophys. Res. (Space Phys.) 107, doi:10.1029/2002JA009240. 31-1]. If so, the total mass of these fine, nearly invisible particles may be comparable to the mass of the gas, and could account for much of Io's rapid resurfacing.

  15. Improving operational plume forecasts

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2012-04-01

    Forecasting how plumes of particles, such as radioactive particles from a nuclear disaster, will be transported and dispersed in the atmosphere is an important but computationally challenging task. During the Fukushima nuclear disaster in Japan, operational plume forecasts were produced each day, but as the emissions continued, previous emissions were not included in the simulations used for forecasts because it became impractical to rerun the simulations each day from the beginning of the accident. Draxler and Rolph examine whether it is possible to improve plume simulation speed and flexibility as conditions and input data change. The authors use a method known as a transfer coefficient matrix approach that allows them to simulate many radionuclides using only a few generic species for the computation. Their simulations work faster by dividing the computation into separate independent segments in such a way that the most computationally time consuming pieces of the calculation need to be done only once. This makes it possible to provide real-time operational plume forecasts by continuously updating the previous simulations as new data become available. They tested their method using data from the Fukushima incident to show that it performed well. (Journal of Geophysical Research-Atmospheres, doi:10.1029/2011JD017205, 2012)

  16. Ridge-crossing mantle plumes and gaps in tracks

    NASA Astrophysics Data System (ADS)

    Sleep, Norman H.

    2002-12-01

    Hot spot tracks approach, cross, and leave ridge axes. The complications of this process make it difficult to determine the track followed by a plume and the evolution of its vigor. When a plume is sufficiently near the ridge axis, buoyant plume material flows along the base of the lithosphere toward the axis, forming an on-axis hot spot. The track of the on-axis hot spot is a symmetric V on both plates and an unreliable indication of the path followed by the plume. Aseismic ridges form more or less along flowlines from a plume to a ridge axis when channels form at the base of the lithosphere. A dynamic effect is that off-axis hot spots appear to shut off at the time that an on-axis hot spot becomes active along an axis-approaching track. This produces a gap in the obvious track and a jump of the hot spot to the ridge axis. The gap results from the effects of ponded plume material on intraplate (membrane) stress. Membrane tension lets dikes ascend efficiently to produce obvious tracks of edifices. An off-axis hot spot shuts down when the plume is sufficiently near the ridge axis that plume material flows there, putting the nearby lithosphere above the plume into compression, preventing dikes. In addition, the off-axis thickness of plume material, which produces membrane tension, decreases as the slope of the base of the lithosphere increases beneath young lithosphere. Slow spreading rates favor gaps produced in this way. Gaps are observed near both fast and slow ridges.

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

    NASA Astrophysics Data System (ADS)

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

    2006-02-01

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

  18. PLUME-MoM 1.0: a new 1-D model of volcanic plumes based on the method of moments

    NASA Astrophysics Data System (ADS)

    de'Michieli Vitturi, M.; Neri, A.; Barsotti, S.

    2015-05-01

    In this paper a new mathematical model for volcanic plumes, named PlumeMoM, is presented. The model describes the steady-state 1-D dynamics of the plume in a 3-D coordinate system, accounting for continuous variability in particle distribution of the pyroclastic mixture ejected at the vent. Volcanic plumes are composed of pyroclastic particles of many different sizes ranging from a few microns up to several centimeters and more. Proper description of such a multiparticle nature is crucial when quantifying changes in grain-size distribution along the plume and, therefore, for better characterization of source conditions of ash dispersal models. The new model is based on the method of moments, which allows description of the pyroclastic mixture dynamics not only in the spatial domain but also in the space of properties of the continuous size-distribution of the particles. This is achieved by formulation of fundamental transport equations for the multiparticle mixture with respect to the different moments of the grain-size distribution. Different formulations, in terms of the distribution of the particle number, as well as of the mass distribution expressed in terms of the Krumbein log scale, are also derived. Comparison between the new moments-based formulation and the classical approach, based on the discretization of the mixture in N discrete phases, shows that the new model allows the same results to be obtained with a significantly lower computational cost (particularly when a large number of discrete phases is adopted). Application of the new model, coupled with uncertainty quantification and global sensitivity analyses, enables investigation of the response of four key output variables (mean and standard deviation (SD) of the grain-size distribution at the top of the plume, plume height and amount of mass lost by the plume during the ascent) to changes in the main input parameters (mean and SD) characterizing the pyroclastic mixture at the base of the plume

  19. Voltage and pace-capture mapping of linear ablation lesions overestimates chronic ablation gap size.

    PubMed

    O'Neill, Louisa; Harrison, James; Chubb, Henry; Whitaker, John; Mukherjee, Rahul K; Bloch, Lars Ølgaard; Andersen, Niels Peter; Dam, Høgni; Jensen, Henrik K; Niederer, Steven; Wright, Matthew; O'Neill, Mark; Williams, Steven E

    2018-04-26

    Conducting gaps in lesion sets are a major reason for failure of ablation procedures. Voltage mapping and pace-capture have been proposed for intra-procedural identification of gaps. We aimed to compare gap size measured acutely and chronically post-ablation to macroscopic gap size in a porcine model. Intercaval linear ablation was performed in eight Göttingen minipigs with a deliberate gap of ∼5 mm left in the ablation line. Gap size was measured by interpolating ablation contact force values between ablation tags and thresholding at a low force cut-off of 5 g. Bipolar voltage mapping and pace-capture mapping along the length of the line were performed immediately, and at 2 months, post-ablation. Animals were euthanized and gap sizes were measured macroscopically. Voltage thresholds to define scar were determined by receiver operating characteristic analysis as <0.56 mV (acutely) and <0.62 mV (chronically). Taking the macroscopic gap size as gold standard, error in gap measurements were determined for voltage, pace-capture, and ablation contact force maps. All modalities overestimated chronic gap size, by 1.4 ± 2.0 mm (ablation contact force map), 5.1 ± 3.4 mm (pace-capture), and 9.5 ± 3.8 mm (voltage mapping). Error on ablation contact force map gap measurements were significantly less than for voltage mapping (P = 0.003, Tukey's multiple comparisons test). Chronically, voltage mapping and pace-capture mapping overestimated macroscopic gap size by 11.9 ± 3.7 and 9.8 ± 3.5 mm, respectively. Bipolar voltage and pace-capture mapping overestimate the size of chronic gap formation in linear ablation lesions. The most accurate estimation of chronic gap size was achieved by analysis of catheter-myocardium contact force during ablation.

  20. Plasma plume MHD power generator and method

    DOEpatents

    Hammer, J.H.

    1993-08-10

    A method is described of generating power at a situs exposed to the solar wind which comprises creating at separate sources at the situs discrete plasma plumes extending in opposed directions, providing electrical communication between the plumes at their source and interposing a desired electrical load in the said electrical communication between the plumes.

  1. Effects of plume afterburning on infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhu, Xijuan; Xu, Ying; Ma, Jing; Duan, Ran; Wu, Jie

    2017-10-01

    Contains H2, CO and unburned components of high-temperature plume of rocket engine, then injected into the atmosphere, continue to carry out the oxidation reaction in the plume near field region with the volume in the plume of oxygen in the air, two times burning. The afterburning is an important cause of infrared radiation intensification of propellant plume, which increases the temperature of the flame and changes the components of the gas, thus enhancing the infrared radiation intensity of the flame. [1]. Two the combustion numerical using chemical reaction mechanism involving HO2 intermediate reaction, the study confirmed that HO2 is a key intermediate, plays a decisive role to trigger early response, on afterburning temperature and flow concentration distribution effect. A finite rate chemical reaction model is used to describe the two burning phenomenon in high temperature plume[2]. In this paper, a numerical simulation of the flame flow field and radiative transfer is carried out for the afterburning phenomenon. The effects of afterburning on the composition, temperature and infrared radiation of the plume are obtained by comparison.

  2. Total plankton respiration in the Chesapeake Bay plume

    NASA Technical Reports Server (NTRS)

    Robertson, C. N.; Thomas, J. P.

    1981-01-01

    Total plankton respiration (TPR) was measured at 17 stations within the Chesapeake Bay plume off the Virginia coast during March, June, and October 1980. Elevated rates of TPR, as well as higher concentrations of chlorophyll a and phaeopigment a, were found to be associated with the Bay plume during each survey. The TPR rates within the Bay plume were close to those found associated with the Hudson River plume for comparable times of the year. The data examined indicate that the Chesapeake Bay plume stimulates biological activity and is a source of organic loading to the contiguous shelf ecosystem.

  3. The Afar Depression: Was There a Triple Junction Above the Mantle Plume?

    NASA Astrophysics Data System (ADS)

    Ebinger, C.; Wolfenden, E.; Yirgu, G.; Ayalew, D.; Eagles, G.; Gloaguen, R.; Tiberi, C.; Rowland, J. R.; Deino, A.; Tesfaye, A.; Tesfaye, S.

    2002-12-01

    The Red Sea - Gulf of Aden- Main Ethiopian rift systems (Afar Depression) have served as the textbook example of a R-R-R triple junction zone which formed above a mantle plume (Ethiopia-Yemen flood basalt province, 31-28 Ma). Recent work has documented the onset and propagation of seafloor along the length of the Gulf of Aden and Red Sea arms, but the timing of continental rifting had been poorly constrained. Our aims were to constrain the timing of rift initiation in each arm of the rift near the proposed Oligocene triple junction and to re-assess models for break-up above a mantle plume. Although much of the early history of rifting is deeply buried by Pliocene-Recent lavas, erosional dissection of the rift margins provides windows into the early rift history. Along the southernmost Red Sea, faults commonly marked by eruptive centers initiated at about 26 Ma, coincident with rifting along the easternmost Gulf of Aden. New data from the rift immediately south of the southernmost Red Sea basin (ca.10N) constrain the earliest rift sequences in the northern Main Ethiopian rift (MER). Field and Ar-Ar data from sequences overlying the pre-rift flood basalts show that extension in the northern MER commenced at 12-10 Ma when the two rift systems were finally linked. The active zone of extension and magmatism in the southern Red Sea and eastern Gulf of Aden, however, had migrated east and north, respectively. Summarising, rifting in southern Ethiopia had commenced by 16-18 Ma, and had propagated northward to cut across Oligo-Miocene rift structures of the Red Sea and Gulf of Aden by 10 Ma, consistent with plate kinematic data. A triple junction could have developed only during the past 10 My, long after flood basaltic magmatism. Inverse models of gravity data predict a significant step (2-4 km) in the Moho where the youthful, less extended MER breaks into the Afar Depression. Project EAGLE (UK-US-Ethiopia) is now acquiring seismic data across and along this zone to

  4. Sulfur plumes off Namibia

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Sulfur plumes rising up from the bottom of the ocean floor produce colorful swirls in the waters off the coast of Namibia in southern Africa. The plumes come from the breakdown of marine plant matter by anaerobic bacteria that do not need oxygen to live. This image was acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Terra satellite on April 24, 2002 Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  5. Ablation for Atrial Fibrillation

    PubMed Central

    2006-01-01

    Executive Summary Objective To review the effectiveness, safety, and costing of ablation methods to manage atrial fibrillation (AF). The ablation methods reviewed were catheter ablation and surgical ablation. Clinical Need Atrial fibrillation is characterized by an irregular, usually rapid, heart rate that limits the ability of the atria to pump blood effectively to the ventricles. Atrial fibrillation can be a primary diagnosis or it may be associated with other diseases, such as high blood pressure, abnormal heart muscle function, chronic lung diseases, and coronary heart disease. The most common symptom of AF is palpitations. Symptoms caused by decreased blood flow include dizziness, fatigue, and shortness of breath. Some patients with AF do not experience any symptoms. According to United States data, the incidence of AF increases with age, with a prevalence of 1 per 200 people aged between 50 and 60 years, and 1 per 10 people aged over 80 years. In 2004, the Institute for Clinical Evaluative Sciences (ICES) estimated that the rate of hospitalization for AF in Canada was 582.7 per 100,000 population. They also reported that of the patients discharged alive, 2.7% were readmitted within 1 year for stroke. One United States prevalence study of AF indicated that the overall prevalence of AF was 0.95%. When the results of this study were extrapolated to the population of Ontario, the prevalence of AF in Ontario is 98,758 for residents aged over 20 years. Currently, the first-line therapy for AF is medical therapy with antiarrhythmic drugs (AADs). There are several AADs available, because there is no one AAD that is effective for all patients. The AADs have critical adverse effects that can aggravate existing arrhythmias. The drug selection process frequently involves trial and error until the patient’s symptoms subside. The Technology Ablation has been frequently described as a “cure” for AF, compared with drug therapy, which controls AF but does not cure it

  6. Near-field entrainment in black smoker plumes

    NASA Astrophysics Data System (ADS)

    Smith, J. E.; Germanovich, L. N.; Lowell, R. P.

    2013-12-01

    In this work, we study the entrainment rate of the ambient fluid into a plume in the extreme conditions of hydrothermal venting at ocean floor depths that would be difficult to reproduce in the laboratory. Specifically, we investigate the flow regime in the lower parts of three black smoker plumes in the Main Endeavour Field on the Juan de Fuca Ridge discharging at temperatures of 249°C, 333°C, and 336°C and a pressure of 21 MPa. Such flow conditions are typical for ocean floor hydrothermal venting but would be difficult to reproduce in the laboratory. The centerline temperature was measured at several heights in the plume above the orifice. Using a previously developed turbine flow meter, we also measured the mean flow velocity at the orifice. Measurements were conducted during dives 4452 and 4518 on the submersible Alvin. Using these measurements, we obtained a range of 0.064 - 0.068 for values of the entrainment coefficient α, which is assumed constant near the orifice. This is half the value of α ≈ 0.12 - 0.13 that would be expected for plume flow regimes based on the existing laboratory results and field measurements in lower temperature and pressure conditions. In fact, α = 0.064 - 0.068 is even smaller than the value of α ≈ 0.075 characteristic of jet flow regimes and appears to be the lowest reported in the literature. Assuming that the mean value α = 0.066 is typical for hydrothermal venting at ocean floor depths, we then characterized the flow regimes of 63 black smoker plumes located on the Endeavor Segment of the Juan de Fuca Ridge. Work with the obtained data is ongoing, but current results indicate that approximately half of these black smokers are lazy in the sense that their plumes exhibit momentum deficits compared to the pure plume flow that develops as the plume rises. The remaining half produces forced plumes that show the momentum excess compared to the pure plumes. The lower value of the entrainment coefficient has important

  7. Analysis of Nozzle Jet Plume Effects on Sonic Boom Signature

    NASA Technical Reports Server (NTRS)

    Bui, Trong

    2010-01-01

    An axisymmetric full Navier-Stokes computational fluid dynamics (CFD) study was conducted to examine nozzle exhaust jet plume effects on the sonic boom signature of a supersonic aircraft. A simplified axisymmetric nozzle geometry, representative of the nozzle on the NASA Dryden NF-15B Lift and Nozzle Change Effects on Tail Shock (LaNCETS) research airplane, was considered. The highly underexpanded nozzle flow is found to provide significantly more reduction in the tail shock strength in the sonic boom N-wave pressure signature than perfectly expanded and overexpanded nozzle flows. A tail shock train in the sonic boom signature, similar to what was observed in the LaNCETS flight data, is observed for the highly underexpanded nozzle flow. The CFD results provide a detailed description of the nozzle flow physics involved in the LaNCETS nozzle at different nozzle expansion conditions and help in interpreting LaNCETS flight data as well as in the eventual CFD analysis of a full LaNCETS aircraft. The current study also provided important information on proper modeling of the LaNCETS aircraft nozzle. The primary objective of the current CFD research effort was to support the LaNCETS flight research data analysis effort by studying the detailed nozzle exhaust jet plume s imperfect expansion effects on the sonic boom signature of a supersonic aircraft. Figure 1 illustrates the primary flow physics present in the interaction between the exhaust jet plume shock and the sonic boom coming off of an axisymmetric body in supersonic flight. The steeper tail shock from highly expanded jet plume reduces the dip of the sonic boom N-wave signature. A structured finite-volume compressible full Navier-Stokes CFD code was used in the current study. This approach is not limited by the simplifying assumptions inherent in previous sonic boom analysis efforts. Also, this study was the first known jet plume sonic boom CFD study in which the full viscous nozzle flow field was modeled, without

  8. A numerical study of the Magellan Plume

    NASA Astrophysics Data System (ADS)

    Palma, Elbio D.; Matano, Ricardo P.

    2012-05-01

    In this modeling study we investigate the dynamical mechanisms controlling the spreading of the Magellan Plume, which is a low-salinity tongue that extends along the Patagonian Shelf. Our results indicate that the overall characteristics of the plume (width, depth, spreading rate, etc.) are primarily influenced by tidal forcing, which manifests through tidal mixing and tidal residual currents. Tidal forcing produces a homogenization of the plume's waters and an offshore displacement of its salinity front. The interaction between tidal and wind-forcing reinforces the downstream and upstream buoyancy transports of the plume. The influence of the Malvinas Current on the Magellan Plume is more dominant north of 50°S, where it increases the along-shelf velocities and generates intrusions of saltier waters from the outer shelf, thus causing a reduction of the downstream buoyancy transport. Our experiments also indicate that the northern limit of the Magellan Plume is set by a high salinity discharge from the San Matias Gulf. Sensitivity experiments show that increments of the wind stress cause a decrease of the downstream buoyancy transport and an increase of the upstream buoyancy transport. Variations of the magnitude of the discharge produce substantial modifications in the downstream penetration of the plume and buoyancy transport. The Magellan discharge generates a northeastward current in the middle shelf, a recirculation gyre south of the inlet and a region of weak currents father north.

  9. Radiation from advanced solid rocket motor plumes

    NASA Technical Reports Server (NTRS)

    Farmer, Richard C.; Smith, Sheldon D.; Myruski, Brian L.

    1994-01-01

    The overall objective of this study was to develop an understanding of solid rocket motor (SRM) plumes in sufficient detail to accurately explain the majority of plume radiation test data. Improved flowfield and radiation analysis codes were developed to accurately and efficiently account for all the factors which effect radiation heating from rocket plumes. These codes were verified by comparing predicted plume behavior with measured NASA/MSFC ASRM test data. Upon conducting a thorough review of the current state-of-the-art of SRM plume flowfield and radiation prediction methodology and the pertinent data base, the following analyses were developed for future design use. The NOZZRAD code was developed for preliminary base heating design and Al2O3 particle optical property data evaluation using a generalized two-flux solution to the radiative transfer equation. The IDARAD code was developed for rapid evaluation of plume radiation effects using the spherical harmonics method of differential approximation to the radiative transfer equation. The FDNS CFD code with fully coupled Euler-Lagrange particle tracking was validated by comparison to predictions made with the industry standard RAMP code for SRM nozzle flowfield analysis. The FDNS code provides the ability to analyze not only rocket nozzle flow, but also axisymmetric and three-dimensional plume flowfields with state-of-the-art CFD methodology. Procedures for conducting meaningful thermo-vision camera studies were developed.

  10. Conjecture of plume components in hydrothermal sea area

    NASA Astrophysics Data System (ADS)

    Noda, K., IV; Aoyama, C.

    2017-12-01

    Investigation at Southern Okinawa Trough, western Kume Island, and Tokara Islands was performed from June 26 to July 12, 2016, as a part of Japan's cross ministerial Strategic Innovation Promotion Program (SIP) for a complete understanding of active hydrothermal vents. In this investigation, water column sonar data was obtained using multi-beam sonar (EM122) onboard YOKOSUKA (Japan Agency for Marine-Earth Science and Technology) and methane plumes were alsp monitored (YK16-07). Multi-beam sonar is an acoustic instrument used to measure submarine topography, and in this investigation, plumes were observed to successfully regenerate the data. It also became clear that volume backscattering strength (SV) of plumes varies, depending on the area where they are settled. On the other hand, components of plumes are still unknown. In this study, acoustic data obtained from YK16-07 will be reviewed using analytical software (echo view 7) to calculate volume backscattering strength (SV) of plumes. Likewise, multi-beam sonar (EM122) onboard DAIICHI KAIYOMARU (KAIYO ENGINEERING CO., LTD) was used to collect acoustic data. This already known data of methane plume from Sea of Japan will be analyzed using echo view 7. By comparing these data, plume components will be examined from plume size.

  11. Plume Collection Strategies for Icy World Sample Return

    NASA Technical Reports Server (NTRS)

    Neveu, M.; Glavin, D. P.; Tsou, P.; Anbar, A. D.; Williams, P.

    2015-01-01

    Three icy worlds in the solar system display evidence of pluming activity. Water vapor and ice particles emanate from cracks near the south pole of Saturn's moon Enceladus. The plume gas contains simple hydrocarbons that could be fragments of larger, more complex organics. More recently, observations using the Hubble and Herschel space telescopes have hinted at transient water vapor plumes at Jupiter's moon Europa and the dwarf planet Ceres. Plume materials may be ejected directly from possible sub-surface oceans, at least on Enceladus. In such oceans, liquid water, organics, and energy may co-exist, making these environments habitable. The venting of habitable ocean material into space provides a unique opportunity to capture this material during a relatively simple flyby mission and return it to Earth. Plume collection strategies should enable investigations of evidence for life in the returned samples via laboratory analyses of the structure, distribution, isotopic composition, and chirality of the chemical components (including biomolecules) of plume materials. Here, we discuss approaches for the collection of dust and volatiles during flybys through Enceladus' plume, based on Cassini results and lessons learned from the Stardust comet sample return mission. We also highlight areas where sample collector and containment technology development and testing may be needed for future plume sample return missions.

  12. Simulation of Europa's water plume .

    NASA Astrophysics Data System (ADS)

    Lucchetti, A.; Cremonese, G.; Schneider, N. M.; Plainaki, C.; Mazzotta Epifani, E.; Zusi, M.; Palumbo, P.

    Plumes on Europa would be extremely interesting science and mission targets, particularly due to the unique opportunity to obtain direct information on the subsurface composition, thereby addressing Europa's potential habitability. The existence of water plume on the Jupiter's moon Europa has been long speculated until the recent discover. HST imaged surpluses of hydrogen Lyman alpha and oxygen emissions above the southern hemisphere in December 2012 that are consistent with two 200 km high plumes of water vapor (Roth et al. 2013). In previous works ballistic cryovolcanism has been considered and modeled as a possible mechanism for the formation of low-albedo features on Europa's surface (Fagents et al. 2000). Our simulation agrees with the model of Fagents et al. (2000) and consists of icy particles that follow ballistic trajectories. The goal of such an analysis is to define the height, the distribution and the extension of the icy particles falling on the moon's surface as well as the thickness of the deposited layer. We expect to observe high albedo regions in contrast with the background albedo of Europa surface since we consider that material falling after a cryovolcanic plume consists of snow. In order to understand if this phenomenon is detectable we convert the particles deposit in a pixel image of albedo data. We consider also the limb view of the plume because, even if this detection requires optimal viewing geometry, it is easier detectable in principle against sky. Furthermore, we are studying the loss rates due to impact electron dissociation and ionization to understand how these reactions decrease the intensity of the phenomenon. We expect to obtain constraints on imaging requirements necessary to detect potential plumes that could be useful for ESA's JUICE mission, and in particular for the JANUS camera (Palumbo et al. 2014).

  13. Ocean outfall plume characterization using an Autonomous Underwater Vehicle.

    PubMed

    Rogowski, Peter; Terrill, Eric; Otero, Mark; Hazard, Lisa; Middleton, William

    2013-01-01

    A monitoring mission to map and characterize the Point Loma Ocean Outfall (PLOO) wastewater plume using an Autonomous Underwater Vehicle (AUV) was performed on 3 March 2011. The mobility of an AUV provides a significant advantage in surveying discharge plumes over traditional cast-based methods, and when combined with optical and oceanographic sensors, provides a capability for both detecting plumes and assessing their mixing in the near and far-fields. Unique to this study is the measurement of Colored Dissolved Organic Matter (CDOM) in the discharge plume and its application for quantitative estimates of the plume's dilution. AUV mission planning methodologies for discharge plume sampling, plume characterization using onboard optical sensors, and comparison of observational data to model results are presented. The results suggest that even under variable oceanic conditions, properly planned missions for AUVs equipped with an optical CDOM sensor in addition to traditional oceanographic sensors, can accurately characterize and track ocean outfall plumes at higher resolutions than cast-based techniques.

  14. UV Detection and Characterization of Plume Activity

    NASA Astrophysics Data System (ADS)

    Hansen, C. J.; Esposito, L. W.; Hendrix, A. R.

    2017-12-01

    Observations at ultraviolet wavelengths offer multiple techniques for detecting and characterizing plumes of gas erupting from planetary bodies. At Enceladus and Europa, UV observations include emission and absorption by water vapor molecules, and reflectance from ice particles. Emission: Emission features from electrons' interaction with water products H, OH, O and O2 can signal the presence of a plume. OH and O form a torus in the Saturn system, supplied by Enceladus' water vapor plume, that was detected before Cassini arrived in orbit [1, 2]. The nature of the ratio of H, O, and O2 emissions from Europa allow separation of the possible presence of plume(s) from Europa's O2 exosphere [3]. Absorption: The spectrum of starlight transmitted through an absorbing gas will have attenuation at UV wavelengths that are diagnostic of the composition of the gas. At Enceladus stellar and solar occultations by Enceladus' plume showed the primary composition to be water, constrained plume dimensions and revealed the presence of imbedded supersonic jets [4]. The amount of water coming from Enceladus and its variability over a decade has been measured [5]. Using Saturn as a source was not useful for Enceladus when it was observed in transit across Saturn. In contrast the putative detection of plume(s) at Europa has been bolstered by evidence that reflected light from Jupiter was being absorbed at particular places along Europa's limb as it transited Jupiter [6]. This contrast may reveal fundamental differences in the plumes at Europa and Enceladus [7]. Reflectance: With extremely long integration times the Enceladus plume has been observed reflecting light - light which is in turn absorbed by a small percentage of C2H4 gas being expelled [8]. The ice grain / gas ratio has been estimated by comparison of reflected light at near-IR wavelengths to the gas absorption of sunlight in the UV [9]. [1] Shemansky, D. E. et al. (1993) Nature 363:329; [2] Esposito, L. W. et al. (2005

  15. Atrial fibrillation ablation using a closed irrigation radiofrequency ablation catheter.

    PubMed

    Golden, Keith; Mounsey, John Paul; Chung, Eugene; Roomiani, Pahresah; Morse, Michael Andew; Patel, Ankit; Gehi, Anil

    2012-05-01

    Catheter ablation is an effective therapy for symptomatic, medically refractory atrial fibrillation (AF). Open-irrigated radiofrequency (RF) ablation catheters produce transmural lesions at the cost of increased fluid delivery. In vivo models suggest closed-irrigated RF catheters create equivalent lesions, but clinical outcomes are limited. A cohort of 195 sequential patients with symptomatic AF underwent stepwise AF ablation (AFA) using a closed-irrigation ablation catheter. Recurrence of AF was monitored and outcomes were evaluated using Kaplan-Meier survival analysis and Cox proportional hazards models. Mean age was 59.0 years, 74.9% were male, 56.4% of patients were paroxysmal and mean duration of AF was 5.4 years. Patients had multiple comorbidities including hypertension (76.4%), tobacco abuse (42.1%), diabetes (17.4%), and obesity (mean body mass index 30.8). The median follow-up was 55.8 weeks. Overall event-free survival was 73.6% with one ablation and 77.4% after reablation (reablation rate was 8.7%). Median time to recurrence was 26.9 weeks. AF was more likely to recur in patients being treated with antiarrhythmic therapy at the time of last follow-up (recurrence rate 30.3% with antiarrhythmic drugs, 13.2% without antiarrhythmic drugs; hazard ratio [HR] 2.2, 95% confidence interval [CI] 1.1-4.4, P = 0.024) and in those with a history of AF greater than 2 years duration (HR 2.7, 95% CI 1.1-6.9, P = 0.038). Our study represents the largest cohort of patients receiving AFA with closed-irrigation ablation catheters. We demonstrate comparable outcomes to those previously reported in studies of open-irrigation ablation catheters. Given the theoretical benefits of a closed-irrigation system, a large head-to-head comparison using this catheter is warranted. ©2012, The Authors. Journal compilation ©2012 Wiley Periodicals, Inc.

  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. Explosive change in crater properties during high power nanosecond laser ablation of silicon

    NASA Astrophysics Data System (ADS)

    Yoo, J. H.; Jeong, S. H.; Greif, R.; Russo, R. E.

    2000-08-01

    Mass removed from single crystal silicon samples by high irradiance (1×109 to 1×1011W/cm2) single pulse laser ablation was studied by measuring the resulting crater morphology with a white light interferometric microscope. The craters show a strong nonlinear change in both the volume and depth when the laser irradiance is less than or greater than ≈2.2×1010W/cm2. Time-resolved shadowgraph images of the ablated silicon plume were obtained over this irradiance range. The images show that the increase in crater volume and depth at the threshold of 2.2×1010W/cm2 is accompanied by large size droplets leaving the silicon surface, with a time delay ˜300 ns. A numerical model was used to estimate the thickness of the layer heated to approximately the critical temperature. The model includes transformation of liquid metal into liquid dielectric near the critical state (i.e., induced transparency). In this case, the estimated thickness of the superheated layer at a delay time of 200-300 ns shows a close agreement with measured crater depths. Induced transparency is demonstrated to play an important role in the formation of a deep superheated liquid layer, with subsequent explosive boiling responsible for large-particulate ejection.

  18. Feasibility Study on Cardiac Arrhythmia Ablation Using High-Energy Heavy Ion Beams

    NASA Astrophysics Data System (ADS)

    Lehmann, H. Immo; Graeff, Christian; Simoniello, Palma; Constantinescu, Anna; Takami, Mitsuru; Lugenbiel, Patrick; Richter, Daniel; Eichhorn, Anna; Prall, Matthias; Kaderka, Robert; Fiedler, Fine; Helmbrecht, Stephan; Fournier, Claudia; Erbeldinger, Nadine; Rahm, Ann-Kathrin; Rivinius, Rasmus; Thomas, Dierk; Katus, Hugo A.; Johnson, Susan B.; Parker, Kay D.; Debus, Jürgen; Asirvatham, Samuel J.; Bert, Christoph; Durante, Marco; Packer, Douglas L.

    2016-12-01

    High-energy ion beams are successfully used in cancer therapy and precisely deliver high doses of ionizing radiation to small deep-seated target volumes. A similar noninvasive treatment modality for cardiac arrhythmias was tested here. This study used high-energy carbon ions for ablation of cardiac tissue in pigs. Doses of 25, 40, and 55 Gy were applied in forced-breath-hold to the atrioventricular junction, left atrial pulmonary vein junction, and freewall left ventricle of intact animals. Procedural success was tracked by (1.) in-beam positron-emission tomography (PET) imaging; (2.) intracardiac voltage mapping with visible lesion on ultrasound; (3.) lesion outcomes in pathohistolgy. High doses (40-55 Gy) caused slowing and interruption of cardiac impulse propagation. Target fibrosis was the main mediator of the ablation effect. In irradiated tissue, apoptosis was present after 3, but not 6 months. Our study shows feasibility to use high-energy ion beams for creation of cardiac lesions that chronically interrupt cardiac conduction.

  19. Inter-comparison of three-dimensional models of volcanic plumes

    USGS Publications Warehouse

    Suzuki, Yujiro; Costa, Antonio; Cerminara, Matteo; Esposti Ongaro, Tomaso; Herzog, Michael; Van Eaton, Alexa; Denby, Leif

    2016-01-01

    We performed an inter-comparison study of three-dimensional models of volcanic plumes. A set of common volcanological input parameters and meteorological conditions were provided for two kinds of eruptions, representing a weak and a strong eruption column. From the different models, we compared the maximum plume height, neutral buoyancy level (where plume density equals that of the atmosphere), and level of maximum radial spreading of the umbrella cloud. We also compared the vertical profiles of eruption column properties, integrated across cross-sections of the plume (integral variables). Although the models use different numerical procedures and treatments of subgrid turbulence and particle dynamics, the inter-comparison shows qualitatively consistent results. In the weak plume case (mass eruption rate 1.5 × 106 kg s− 1), the vertical profiles of plume properties (e.g., vertical velocity, temperature) are similar among models, especially in the buoyant plume region. Variability among the simulated maximum heights is ~ 20%, whereas neutral buoyancy level and level of maximum radial spreading vary by ~ 10%. Time-averaging of the three-dimensional (3D) flow fields indicates an effective entrainment coefficient around 0.1 in the buoyant plume region, with much lower values in the jet region, which is consistent with findings of small-scale laboratory experiments. On the other hand, the strong plume case (mass eruption rate 1.5 × 109 kg s− 1) shows greater variability in the vertical plume profiles predicted by the different models. Our analysis suggests that the unstable flow dynamics in the strong plume enhances differences in the formulation and numerical solution of the models. This is especially evident in the overshooting top of the plume, which extends a significant portion (~ 1/8) of the maximum plume height. Nonetheless, overall variability in the spreading level and neutral buoyancy level is ~ 20%, whereas that of maximum height is ~ 10

  20. Plume structure in high-Rayleigh-number convection

    NASA Astrophysics Data System (ADS)

    Puthenveettil, Baburaj A.; Arakeri, Jaywant H.

    2005-10-01

    Near-wall structures in turbulent natural convection at Rayleigh numbers of 10^{10} to 10^{11} at A Schmidt number of 602 are visualized by a new method of driving the convection across a fine membrane using concentration differences of sodium chloride. The visualizations show the near-wall flow to consist of sheet plumes. A wide variety of large-scale flow cells, scaling with the cross-section dimension, are observed. Multiple large-scale flow cells are seen at aspect ratio (AR)= 0.65, while only a single circulation cell is detected at AR= 0.435. The cells (or the mean wind) are driven by plumes coming together to form columns of rising lighter fluid. The wind in turn aligns the sheet plumes along the direction of shear. the mean wind direction is seen to change with time. The near-wall dynamics show plumes initiated at points, which elongate to form sheets and then merge. Increase in rayleigh number results in a larger number of closely and regularly spaced plumes. The plume spacings show a common log normal probability distribution function, independent of the rayleigh number and the aspect ratio. We propose that the near-wall structure is made of laminar natural-convection boundary layers, which become unstable to give rise to sheet plumes, and show that the predictions of a model constructed on this hypothesis match the experiments. Based on these findings, we conclude that in the presence of a mean wind, the local near-wall boundary layers associated with each sheet plume in high-rayleigh-number turbulent natural convection are likely to be laminar mixed convection type.

  1. Enceladus's Plumes: A Rocket Analogy

    NASA Astrophysics Data System (ADS)

    McNutt, R. L.; Perry, M. E.; Waite, J. H.; Fletcher, G.; Cravens, T. E.

    2009-12-01

    The plumes of Enceladus, and the source of the E-ring in the Saturnian system, easily rank as the major, significant, and unexpected discovery of the Cassini mission. While clearly the source of the E-ring,the nature of the sources and the energetics and dynamics of the plumes and underlying jets remains a subject of intensive study. Refinements of the observations suggest supersonic flow of the primary, water-vapor effluent. Such behavior implies a sonic critical point in the flow beginning from a heated reservoir of vapor, through a constriction, and out at supersonic speeds in the space above the plume/jet channels. Such geometry and thermal conditions mimic that of a de Laval nozzle, such as used in rocket engines for converting chemically heated combustion products into a directional flow. A chamber temperature of 180K suggests an outflow speed as high as 0.8 km/s. With a column density across a jet of ~3 x 1016 cm-2 (about twice that of the broad plume) and a jet width of ~10 km, the implied outflow of water molecules is ~3 x 1010 cm-3 x π/4 (106 cm)2 x 18 amu x 1.66 x 10-27 amu/kg x 8 x 104 cm/s = ~60 kg/s in each constituent jet, of which eight were identified by the Cassini Ultraviolet Imaging Spectrograph (UVIS) during the occultation measurements of the plume region of Enceladus carried out on 24 October 2007.

  2. Bromine oxidation in volcanic plumes

    NASA Astrophysics Data System (ADS)

    Bobrowski, N.; Vogel, L.; Kern, C.; Giuffrida, G. B.; Delgado-Granados, H.; Platt, U.

    2009-04-01

    Volcanoes are very strong sources of hydrogen, carbon, sulphur and halogen compounds, as well as of particles. Some gases only behave as passive tracers; others interact and affect the formation, growth or chemical characteristics of aerosol particles in a complex system. Recent measurements of halogen radicals in volcanic plumes showed that volcanic plumes are chemically very active. Kinetic considerations (Oppenheimer et al., 2006) and detailed calculations with an atmospheric chemistry model (Bobrowski et al., 2007) explain the halogen chemistry mainly with photochemical reactions involving both, the gas and particle phase. They reproduce the measured gas-phase concentrations quite well. However, temporal evolution of BrO in the early plume is not well described in the models. The understanding of chemical kinetics of BrO formation is still not complete. Recent measurement results (Vogel et al., 2008) do not fit with initial model calculation. The new data lead to the suggestion that the BrO formation could be much faster during the first few minutes after emission than initially suggested. Old and recent data sets will be confronted, compared and possible causes of their differences discussed. The measurements considered were taken at Mt. Etna (Italy), Villarica (Chile), and Popocatépetl (Mexico) volcanoes. Additionally, at Mt Etna the emission consists of up to four individual plumes from four summit craters. The differences between the individual plumes have been investigated during the last years and will be presented.

  3. Remote sensing of aerosol plumes: a semianalytical model

    NASA Astrophysics Data System (ADS)

    Alakian, Alexandre; Marion, Rodolphe; Briottet, Xavier

    2008-04-01

    A semianalytical model, named APOM (aerosol plume optical model) and predicting the radiative effects of aerosol plumes in the spectral range [0.4,2.5 μm], is presented in the case of nadir viewing. It is devoted to the analysis of plumes arising from single strong emission events (high optical depths) such as fires or industrial discharges. The scene is represented by a standard atmosphere (molecules and natural aerosols) on which a plume layer is added at the bottom. The estimated at-sensor reflectance depends on the atmosphere without plume, the solar zenith angle, the plume optical properties (optical depth, single-scattering albedo, and asymmetry parameter), the ground reflectance, and the wavelength. Its mathematical expression as well as its numerical coefficients are derived from MODTRAN4 radiative transfer simulations. The DISORT option is used with 16 fluxes to provide a sufficiently accurate calculation of multiple scattering effects that are important for dense smokes. Model accuracy is assessed by using a set of simulations performed in the case of biomass burning and industrial plumes. APOM proves to be accurate and robust for solar zenith angles between 0° and 60° whatever the sensor altitude, the standard atmosphere, for plume phase functions defined from urban and rural models, and for plume locations that extend from the ground to a height below 3 km. The modeling errors in the at-sensor reflectance are on average below 0.002. They can reach values of 0.01 but correspond to low relative errors then (below 3% on average). This model can be used for forward modeling (quick simulations of multi/hyperspectral images and help in sensor design) as well as for the retrieval of the plume optical properties from remotely sensed images.

  4. Remote sensing of aerosol plumes: a semianalytical model.

    PubMed

    Alakian, Alexandre; Marion, Rodolphe; Briottet, Xavier

    2008-04-10

    A semianalytical model, named APOM (aerosol plume optical model) and predicting the radiative effects of aerosol plumes in the spectral range [0.4,2.5 microm], is presented in the case of nadir viewing. It is devoted to the analysis of plumes arising from single strong emission events (high optical depths) such as fires or industrial discharges. The scene is represented by a standard atmosphere (molecules and natural aerosols) on which a plume layer is added at the bottom. The estimated at-sensor reflectance depends on the atmosphere without plume, the solar zenith angle, the plume optical properties (optical depth, single-scattering albedo, and asymmetry parameter), the ground reflectance, and the wavelength. Its mathematical expression as well as its numerical coefficients are derived from MODTRAN4 radiative transfer simulations. The DISORT option is used with 16 fluxes to provide a sufficiently accurate calculation of multiple scattering effects that are important for dense smokes. Model accuracy is assessed by using a set of simulations performed in the case of biomass burning and industrial plumes. APOM proves to be accurate and robust for solar zenith angles between 0 degrees and 60 degrees whatever the sensor altitude, the standard atmosphere, for plume phase functions defined from urban and rural models, and for plume locations that extend from the ground to a height below 3 km. The modeling errors in the at-sensor reflectance are on average below 0.002. They can reach values of 0.01 but correspond to low relative errors then (below 3% on average). This model can be used for forward modeling (quick simulations of multi/hyperspectral images and help in sensor design) as well as for the retrieval of the plume optical properties from remotely sensed images.

  5. Statistical characterization of thermal plumes in turbulent thermal convection

    NASA Astrophysics Data System (ADS)

    Zhou, Sheng-Qi; Xie, Yi-Chao; Sun, Chao; Xia, Ke-Qing

    2016-09-01

    We report an experimental study on the statistical properties of the thermal plumes in turbulent thermal convection. A method has been proposed to extract the basic characteristics of thermal plumes from temporal temperature measurement inside the convection cell. It has been found that both plume amplitude A and cap width w , in a time domain, are approximately in the log-normal distribution. In particular, the normalized most probable front width is found to be a characteristic scale of thermal plumes, which is much larger than the thermal boundary layer thickness. Over a wide range of the Rayleigh number, the statistical characterizations of the thermal fluctuations of plumes, and the turbulent background, the plume front width and plume spacing have been discussed and compared with the theoretical predictions and morphological observations. For the most part good agreements have been found with the direct observations.

  6. A model of early formation of uranium molecular oxides in laser-ablated plasmas

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

    Finko, Mikhail S.; Curreli, Davide; Weisz, David G.

    Here, in this work, we present a newly constructed U xO y reaction mechanism that consists of 30 reaction channels (21 of which are reversible channels) for 11 uranium molecular species (including ions). Both the selection of reaction channels and calculation of corresponding rate coefficients is accomplished via a comprehensive literature review and application of basic reaction rate theory. The reaction mechanism is supplemented by a detailed description of oxygen plasma chemistry (19 species and 142 reaction channels) and is used to model an atmospheric laser ablated uranium plume via a 0D (global) model. Finally, the global model is usedmore » to analyze the evolution of key uranium molecular species predicted by the reaction mechanism, and the initial stage of formation of uranium oxide species.« less

  7. A model of early formation of uranium molecular oxides in laser-ablated plasmas

    DOE PAGES

    Finko, Mikhail S.; Curreli, Davide; Weisz, David G.; ...

    2017-10-12

    Here, in this work, we present a newly constructed U xO y reaction mechanism that consists of 30 reaction channels (21 of which are reversible channels) for 11 uranium molecular species (including ions). Both the selection of reaction channels and calculation of corresponding rate coefficients is accomplished via a comprehensive literature review and application of basic reaction rate theory. The reaction mechanism is supplemented by a detailed description of oxygen plasma chemistry (19 species and 142 reaction channels) and is used to model an atmospheric laser ablated uranium plume via a 0D (global) model. Finally, the global model is usedmore » to analyze the evolution of key uranium molecular species predicted by the reaction mechanism, and the initial stage of formation of uranium oxide species.« less

  8. Modeling the Complex Photochemistry of Biomass Burning Plumes in Plume-Scale, Regional, and Global Air Quality Models

    NASA Astrophysics Data System (ADS)

    Alvarado, M. J.; Lonsdale, C. R.; Yokelson, R. J.; Travis, K.; Fischer, E. V.; Lin, J. C.

    2014-12-01

    Forecasting the impacts of biomass burning (BB) plumes on air quality is difficult due to the complex photochemistry that takes place in the concentrated young BB plumes. The spatial grid of global and regional scale Eulerian models is generally too large to resolve BB photochemistry, which can lead to errors in predicting the formation of secondary organic aerosol (SOA) and O3, as well as the partitioning of NOyspecies. AER's Aerosol Simulation Program (ASP v2.1) can be used within plume-scale Lagrangian models to simulate this complex photochemistry. We will present results of validation studies of the ASP model against aircraft observations of young BB smoke plumes. We will also present initial results from the coupling of ASP v2.1 into the Lagrangian particle dispersion model STILT-Chem in order to better examine the interactions between BB plume chemistry and dispersion. In addition, we have used ASP to develop a sub-grid scale parameterization of the near-source chemistry of BB plumes for use in regional and global air quality models. The parameterization takes inputs from the host model, such as solar zenith angle, temperature, and fire fuel type, and calculates enhancement ratios of O3, NOx, PAN, aerosol nitrate, and other NOy species, as well as organic aerosol (OA). We will present results from the ASP-based BB parameterization as well as its implementation into the global atmospheric composition model GEOS-Chem for the SEAC4RS campaign.

  9. 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. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

  10. Evaluation of electrical propagation delay with cardiomyocytes by photosensitization reaction in vitro

    NASA Astrophysics Data System (ADS)

    Doi, Marika; Ogawa, Emiyu; Arai, Tsunenori

    2017-02-01

    In order to study cardiomyocyte electrical conduction damage by a photosensitization reaction (PR) mostly comes from outside of the cells in a few minutes after the PR, we studied propagation delay of contact action potential with cardiomyocyte by the PR. To determine appropriate PR condition for tachyarrhythmia ablation, a precise electrophysiological experiment in vitro has been preferable. We measured the contact action potential using a microelectrode array system of which information may be correct than conventional Ca2+ measurement. We investigated the propagation delays of an evoked potential to evaluate the electrical conduction damage by the PR. Rat cardiomyocytes were cultivated for 5-7 days on a dish with which 64 electrodes were patterned, in an incubator controlled to 37°C, 5% CO2. The following conditions were used for the PR: 40 μg/ml talapordfin sodium and 290 mW/cm2, 40-78 J/cm2 for an irradiation. A 2D map was obtained to visualize the propagation delays of the evoked potential. The propagation speed, which was calculated based on the measured propagation delays, was decreased by about 30-50% on average of all electrodes after the PR. Therefore, we think 2D propagation delays measurement of the evoked potential with contact action potential measuring system might be available to evaluate the acute electrical conduction damage of cardiomyocyte by the PR.

  11. Image-Guided Ablation of Adrenal Lesions

    PubMed Central

    Yamakado, Koichiro

    2014-01-01

    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. PMID:25049444

  12. Sensitivity of air quality simulation to smoke plume rise

    Treesearch

    Yongqiang Liu; Gary Achtemeier; Scott Goodrick

    2008-01-01

    Plume rise is the height smoke plumes can reach. This information is needed by air quality models such as the Community Multiscale Air Quality (CMAQ) model to simulate physical and chemical processes of point-source fire emissions. This study seeks to understand the importance of plume rise to CMAQ air quality simulation of prescribed burning to plume rise. CMAQ...

  13. Follow the plume: the habitability of Enceladus.

    PubMed

    McKay, Christopher P; Anbar, Ariel D; Porco, Carolyn; Tsou, Peter

    2014-04-01

    The astrobiological exploration of other worlds in our Solar System is moving from initial exploration to more focused astrobiology missions. In this context, we present the case that the plume of Enceladus currently represents the best astrobiology target in the Solar System. Analysis of the plume by the Cassini mission indicates that the steady plume derives from a subsurface liquid water reservoir that contains organic carbon, biologically available nitrogen, redox energy sources, and inorganic salts. Furthermore, samples from the plume jetting out into space are accessible to a low-cost flyby mission. No other world has such well-studied indications of habitable conditions. Thus, the science goals that would motivate an Enceladus mission are more advanced than for any other Solar System body. The goals of such a mission must go beyond further geophysical characterization, extending to the search for biomolecular evidence of life in the organic-rich plume. This will require improved in situ investigations and a sample return.

  14. 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.

  15. Mantle plume capture, anchoring and outflow during ridge interaction

    NASA Astrophysics Data System (ADS)

    Gibson, S. A.; Richards, M. A.; Geist, D.

    2015-12-01

    Geochemical and geophysical studies have shown that >40% of the world's mantle plumes are currently interacting with the global ridge system and such interactions may continue for up to 180 Myr[1]. At sites of plume-ridge interaction up to 1400 km of the spreading centre is influenced by dispersed plume material but there are few constraints on how and where the ridge-ward transfer of deep-sourced material occurs, and also how it is sustained over long time intervals. Galápagos is an archetypal example of an off-axis plume and sheds important light on these mechanisms. The Galápagos plume stem is located ~200 km south of the spreading axis and its head influences 1000 km of the ridge. Nevertheless, the site of enriched basalts, greatest crustal thickness and elevated topography on the ridge, together with active volcanism in the archipelago, correlate with a narrow zone (~150 km) of low-velocity, high-temperature mantle that connects the plume stem and ridge at depths of ~100 km[2]. The enriched ridge basalts contain a greater amount of partially-dehydrated, recycled oceanic crust than basalts elsewhere on the spreading axis, or indeed basalts erupted in the region between the plume stem and ridge. The presence of these relatively volatile-rich ridge basalts requires flow of plume material below the peridotite solidus (i.e.>80 km). We propose a 2-stage model for the development and sustainment of a confined zone of deep ridge-ward plume flow. This involves initial on-axis capture and establishment of a sub-ridge channel of plume flow. Subsequent anchoring of the plume stem to a contact point on the ridge during axis migration results in confined ridge-ward flow of plume material via a deep network of melt channels embedded in the normal spreading and advection of the plume head[2]. Importantly, sub-ridge flow is maintained. The physical parameters and styles of mantle flow we have defined for Galápagos are less-well known at other sites of plume

  16. The Plasmaspheric Plume and Magnetopause Reconnection

    NASA Technical Reports Server (NTRS)

    Walsh, B. M.; Phan, T. D.; Sibeck, D. G.; Souza, V. M.

    2014-01-01

    We present near-simultaneous measurements from two THEMIS spacecraft at the dayside magnetopause with a 1.5 h separation in local time. One spacecraft observes a high-density plasmaspheric plume while the other does not. Both spacecraft observe signatures of magnetic reconnection, providing a test for the changes to reconnection in local time along the magnetopause as well as the impact of high densities on the reconnection process. When the plume is present and the magnetospheric density exceeds that in the magnetosheath, the reconnection jet velocity decreases, the density within the jet increases, and the location of the faster jet is primarily on field lines with magnetosheath orientation. Slower jet velocities indicate that reconnection is occurring less efficiently. In the localized region where the plume contacts the magnetopause, the high-density plume may impede the solar wind-magnetosphere coupling by mass loading the reconnection site.

  17. Is AF Ablation Cost Effective?

    PubMed Central

    Martin-Doyle, William; Reynolds, Matthew R.

    2010-01-01

    The use of catheter ablation to treat AF is increasing rapidly, but there is presently an incomplete understanding of its cost-effectiveness. AF ablation procedures involve significant up-front expenditures, but multiple randomized trials have demonstrated that ablation is more effective than antiarrhythmic drugs at maintaining sinus rhythm in a second-line and possibly first-line rhythm control setting. Although truly long-term data are limited, ablation, as compared with antiarrrhythmic drugs, also appears associated with improved symptoms and quality of life and a reduction in downstream hospitalization and other health care resource utilization. Several groups have developed cost effectiveness models comparing AF ablation primarily to antiarrhythmic drugs and the model results suggest that ablation likely falls within the range generally accepted as cost-effective in developed nations. This paper will review available information on the cost-effectiveness of catheter ablation for the treatment of atrial fibrillation, and discuss continued areas of uncertainty where further research is required. PMID:20936083

  18. Comparing an optical parametric oscillator (OPO) as a viable alternative for mid-infrared tissue ablation with a free electron laser (FEL).

    PubMed

    Mackanos, Mark A; Simanovskii, Dmitrii M; Contag, Christopher H; Kozub, John A; Jansen, E Duco

    2012-11-01

    Beneficial medical laser ablation removes material efficiently with minimal collateral damage. A Mark-III free electron laser (FEL), at a wavelength of 6.45 μm has demonstrated minimal damage and high ablation yield in ocular and neural tissues. While this wavelength has shown promise for surgical applications, further advances are limited by the high overhead for FEL use. Alternative mid-infrared sources are needed for further development. We compared the FEL with a 5-μs pulse duration with a Q-switched ZGP-OPO with a 100-ns pulse duration at mid-infrared wavelengths. There were no differences in the ablation threshold of water and mouse dermis with these two sources in spite of the difference in their pulse structures. There was a significant difference in crater depth between the ZGP:OPO and the FEL. At 6.1 μm, the OPO craters are eight times the depth of the FEL craters. The OPO craters at 6.45 and 6.73 μm were six and five times the depth of the FEL craters, respectively. Bright-field (pump-probe) images showed the classic ablation mechanism from formation of a plume through collapse and recoil. The crater formation, ejection, and collapse phases occurred on a faster time-scale with the OPO than with the FEL. This research showed that a ZGP-OPO laser could be a viable alternative to FEL for clinical applications.

  19. Birth, life, and death of a solar coronal plume

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

    Pucci, Stefano; Romoli, Marco; Poletto, Giannina

    2014-10-01

    We analyze a solar polar-coronal-hole (CH) plume over its entire ≈40 hr lifetime, using high-resolution Solar Dynamic Observatory Atmospheric Imaging Assembly (AIA) data. We examine (1) the plume's relationship to a bright point (BP) that persists at its base, (2) plume outflows and their possible contribution to the solar wind mass supply, and (3) the physical properties of the plume. We find that the plume started ≈2 hr after the BP first appeared and became undetectable ≈1 hr after the BP disappeared. We detected radially moving radiance variations from both the plume and from interplume regions, corresponding to apparent outflowmore » speeds ranging over ≈(30-300) km s{sup –1} with outflow velocities being higher in the 'cooler' AIA 171 Å channel than in the 'hotter' 193 Å and 211 Å channels, which is inconsistent with wave motions; therefore, we conclude that the observed radiance variations represent material outflows. If they persist into the heliosphere and plumes cover ≈10% of a typical CH area, these flows could account for ≈50% of the solar wind mass. From a differential emission measure analysis of the AIA images, we find that the average electron temperature of the plume remained approximately constant over its lifetime, at T {sub e} ≈ 8.5 × 10{sup 5} K. Its density, however, decreased with the age of the plume, being about a factor of three lower when the plume faded compared to when it was born. We conclude that the plume died due to a density reduction rather than to a temperature decrease.« less

  20. Hubble Sees Recurring Plume Erupting From Europa

    NASA Image and Video Library

    2017-04-13

    These composite images show a suspected plume of material erupting two years apart from the same location on Jupiter's icy moon Europa. The images bolster evidence that the plumes are a real phenomenon, flaring up intermittently in the same region on the satellite. Both plumes, photographed in ultraviolet light by NASA's Hubble's Space Telescope Imaging Spectrograph, were seen in silhouette as the moon passed in front of Jupiter. The newly imaged plume, shown at right, rises about 62 miles (100 kilometers) above Europa's frozen surface. The image was taken Feb. 22, 2016. The plume in the image at left, observed by Hubble on March 17, 2014, originates from the same location. It is estimated to be about 30 miles (50 kilometers) high. The snapshot of Europa, superimposed on the Hubble image, was assembled from data from NASA's Galileo mission to Jupiter. The plumes correspond to the location of an unusually warm spot on the moon's icy crust, seen in the late 1990s by the Galileo spacecraft (see PIA21444). Researchers speculate that this might be circumstantial evidence for water venting from the moon's subsurface. The material could be associated with the global ocean that is believed to be present beneath the frozen crust. https://photojournal.jpl.nasa.gov/catalog/PIA21443

  1. VISUAL PLUMES MIXING ZONE MODELING SOFTWARE

    EPA Science Inventory

    The US Environmental Protection Agency has a history of developing plume models and providing technical assistance. The Visual Plumes model (VP) is a recent addition to the public-domain models available on the EPA Center for Exposure Assessment Modeling (CEAM) web page. The Wind...

  2. VISUAL PLUMES MIXING ZONE MODELING SOFTWARE

    EPA Science Inventory

    The U.S. Environmental Protection Agency has a long history of both supporting plume model development and providing mixing zone modeling software. The Visual Plumes model is the most recent addition to the suite of public-domain models available through the EPA-Athens Center f...

  3. Digital filtering of plume emission spectra

    NASA Technical Reports Server (NTRS)

    Madzsar, George C.

    1990-01-01

    Fourier transformation and digital filtering techniques were used to separate the superpositioned spectral phenomena observed in the exhaust plumes of liquid propellant rocket engines. Space shuttle main engine (SSME) spectral data were used to show that extraction of spectral lines in the spatial frequency domain does not introduce error, and extraction of the background continuum introduces only minimal error. Error introduced during band extraction could not be quantified due to poor spectrometer resolution. Based on the atomic and molecular species found in the SSME plume, it was determined that spectrometer resolution must be 0.03 nm for SSME plume spectral monitoring.

  4. The interaction of plume heads with compositional discontinuities in the Earth's mantle

    NASA Technical Reports Server (NTRS)

    Manga, Michael; Stone, Howard A.; O'Connell, Richard J.

    1993-01-01

    The effects of compositional discontinuities of density and viscosity in the Earth's mantle on the ascent of mantle plume heads is studied using a boundary integral numerical technique. Three specific problems are considered: (1) a plume head rising away from a deformable interface, (2) a plume head passing through an interface, and (3) a plume head approaching the surface of the Earth. For the case of a plume attached to a free-surface, the calculated time-dependent plume shapesare compared with experimental results. Two principle modes of plume head deformation are observed: plume head elingation or the formation of a cavity inside the plume head. The inferred structure of mantle plumes, namely, a large plume head with a long tail, is characteristic of plumes attached to their source region, and also of buoyant material moving away from an interface and of buoyant material moving through an interface from a high- to low-viscosity region. As a rising plume head approaches the upper mantle, most of the lower mantle will quickly drain from the gap between the plume head and the upper mantle if the plume head enters the upper mantle. If the plume head moves from a high- to low-viscosity region, the plume head becomes significantly elongated and, for the viscosity contrasts thought to exist in the Earth, could extend from the 670 km discontinuity to the surface. Plume heads that are extended owing to a viscosity decrease in the upper mantle have a cylindrical geometry. The dynamic surface topography induced by plume heads is bell-shaped when the top of the plume head is at depths greater than about 0.1 plume head radii. As the plume head approaches the surface and spreads, the dynamic topography becomes plateau-shaped. The largest stresses are produced in the early stages of plume spreading when the plume head is still nearly spherical, and the surface expression of these stresses is likely to be dominated by radial extension. As the plume spreads, compressional

  5. Direct observation of impact propagation and absorption in dense colloidal monolayers

    NASA Astrophysics Data System (ADS)

    Buttinoni, Ivo; Cha, Jinwoong; Lin, Wei-Hsun; Job, Stéphane; Daraio, Chiara; Isa, Lucio

    2017-11-01

    Dense colloidal suspensions can propagate and absorb large mechanical stresses, including impacts and shocks. The wave transport stems from the delicate interplay between the spatial arrangement of the structural units and solvent-mediated effects. For dynamic microscopic systems, elastic deformations of the colloids are usually disregarded due to the damping imposed by the surrounding fluid. Here, we study the propagation of localized mechanical pulses in aqueous monolayers of micron-sized particles of controlled microstructure. We generate extreme localized deformation rates by exciting a target particle via pulsed-laser ablation. In crystalline monolayers, stress propagation fronts take place, where fast-moving particles (V approximately a few meters per second) are aligned along the symmetry axes of the lattice. Conversely, more viscous solvents and disordered structures lead to faster and isotropic energy absorption. Our results demonstrate the accessibility of a regime where elastic collisions also become relevant for suspensions of microscopic particles, behaving as “billiard balls” in a liquid, in analogy with regular packings of macroscopic spheres. We furthermore quantify the scattering of an impact as a function of the local structural disorder.

  6. Robotic navigation and ablation.

    PubMed

    Malcolme-Lawes, L; Kanagaratnam, P

    2010-12-01

    Robotic technologies have been developed to allow optimal catheter stability and reproducible catheter movements with the aim of achieving contiguous and transmural lesion delivery. Two systems for remote navigation of catheters within the heart have been developed; the first is based on a magnetic navigation system (MNS) Niobe, Stereotaxis, Saint-Louis, Missouri, USA, the second is based on a steerable sheath system (Sensei, Hansen Medical, Mountain View, CA, USA). Both robotic and magnetic navigation systems have proven to be feasible for performing ablation of both simple and complex arrhythmias, particularly atrial fibrillation. Studies to date have shown similar success rates for AF ablation compared to that of manual ablation, with many groups finding a reduction in fluoroscopy times. However, the early learning curve of cases demonstrated longer procedure times, mainly due to additional setup times. With centres performing increasing numbers of robotic ablations and the introduction of a pressure monitoring system, lower power settings and instinctive driving software, complication rates are reducing, and fluoroscopy times have been lower than manual ablation in many studies. As the demand for catheter ablation for arrhythmias such as atrial fibrillation increases and the number of centres performing these ablations increases, the demand for systems which reduce the hand skill requirement and improve the comfort of the operator will also increase.

  7. Space shuttle main engine plume radiation model

    NASA Technical Reports Server (NTRS)

    Reardon, J. E.; Lee, Y. C.

    1978-01-01

    The methods are described which are used in predicting the thermal radiation received by space shuttles, from the plumes of the main engines. Radiation to representative surface locations were predicted using the NASA gaseous plume radiation GASRAD program. The plume model is used with the radiative view factor (RAVFAC) program to predict sea level radiation at specified body points. The GASRAD program is described along with the predictions. The RAVFAC model is also discussed.

  8. Smoke plumes: Emissions and effects

    Treesearch

    Susan O' Neill; Shawn Urbanski; Scott Goodrick; Sim Larkin

    2017-01-01

    Smoke can manifest itself as a towering plume rising against the clear blue sky-or as a vast swath of thick haze, with fingers that settle into valleys overnight. It comes in many forms and colors, from fluffy and white to thick and black. Smoke plumes can rise high into the atmosphere and travel great distances across oceans and continents. Or smoke can remain close...

  9. Plume Splitting in a Two-layer Stratified Ambient Fluid

    NASA Astrophysics Data System (ADS)

    Ma, Yongxing; Flynn, Morris; Sutherland, Bruce

    2017-11-01

    A line-source plume descending into a two-layer stratified ambient fluid in a finite sized tank is studied experimentally. Although the total volume of ambient fluid is fixed, lower- and upper-layer fluids are respectively removed and added at a constant rate mimicking marine outfall through diffusers and natural and hybrid ventilated buildings. The influence of the plume on the ambient depends on the value of λ, defined as the ratio of the plume buoyancy to the buoyancy loss of the plume as it crosses the ambient interface. Similar to classical filling-box experiments, the plume can always reach the bottom of the tank if λ > 1 . By contrast, if λ < 1 , an intermediate layer eventually forms as a result of plume splitting. Eventually all of the plume fluid spreads within the intermediate layer. The starting time, tv, and the ending time, tt, of the transition process measured from experiments correlate with the value of λ. A three-layer ambient fluid is observed after transition, and the mean value of the measured densities of the intermediate layer fluid is well predicted using plume theory. Acknowledgments: Funding for this study was provided by NSERC.

  10. Teaching the Mantle Plumes Debate

    NASA Astrophysics Data System (ADS)

    Foulger, G. R.

    2010-12-01

    There is an ongoing debate regarding whether or not mantle plumes exist. This debate has highlighted a number of issues regarding how Earth science is currently practised, and how this feeds into approaches toward teaching students. The plume model is an hypothesis, not a proven fact. And yet many researchers assume a priori that plumes exist. This assumption feeds into teaching. That the plume model is unproven, and that many practising researchers are skeptical, may be at best only mentioned in passing to students, with most teachers assuming that plumes are proven to exist. There is typically little emphasis, in particular in undergraduate teaching, that the origin of melting anomalies is currently uncertain and that scientists do not know all the answers. Little encouragement is given to students to become involved in the debate and to consider the pros and cons for themselves. Typically teachers take the approach that “an answer” (or even “the answer”) must be taught to students. Such a pedagogic approach misses an excellent opportunity to allow students to participate in an important ongoing debate in Earth sciences. It also misses the opportunity to illustrate to students several critical aspects regarding correct application of the scientific method. The scientific method involves attempting to disprove hypotheses, not to prove them. A priori assumptions should be kept uppermost in mind and reconsidered at all stages. Multiple working hypotheses should be entertained. The predictions of a hypothesis should be tested, and unpredicted observations taken as weakening the original hypothesis. Hypotheses should not be endlessly adapted to fit unexpected observations. The difficulty with pedagogic treatment of the mantle plumes debate highlights a general uncertainty about how to teach issues in Earth science that are not yet resolved with certainty. It also represents a missed opportunity to let students experience how scientific theories evolve, warts

  11. Inorganic fullerene-like molybdenum selenide with good biocompatibility synthesized by laser ablation in liquids

    NASA Astrophysics Data System (ADS)

    Wu, Xiaoju; Tian, Xiumei; Chen, Tongming; Zeng, Ao; Yang, Guowei

    2018-07-01

    The fabrication of inorganic fullerene-like nanoparticles (IFNPs) is an attractive idea due to their unique structures and various potential applications. To date, IFNPs have been made from numerous compounds with layered two-dimensional structures, based on various synthetic methods. Here we have demonstrated for the first time that inorganic fullerene-like molybdenum selenide nanoparticles (MoSe2 IFNPs) can be synthesized by laser ablating a molybdenum selenide target in 30 vol % ethanol/water mixture at ambient temperature and pressure. The formation mechanism was proposed to elucidate the production of MoSe2 IFNPs in the process of laser ablation in liquids (LAL). The appropriate solvent facilitates the condensation of the plasma plume created by LAL to planar MoSe2. Then, laser-induced high temperature and high pressure lead to the formation of a vacancy in the planar MoSe2, causing the generation of nucleation and growth of the MoSe2 IFNPs. In addition, a CCK-8 (cell counting kit-8) assay and a cell viability assay were performed to examine the cytotoxic behavior and the effect on cell viability of MoSe2 IFNPs. The results show that MoSe2 IFNPs are reasonably nontoxic and biocompatible with the given cells, showing they have significant potential in biomedical applications.

  12. Inorganic fullerene-like molybdenum selenide with good biocompatibility synthesized by laser ablation in liquids.

    PubMed

    Wu, Xiaoju; Tian, Xiumei; Chen, Tongming; Zeng, Ao; Yang, Guowei

    2018-07-20

    The fabrication of inorganic fullerene-like nanoparticles (IFNPs) is an attractive idea due to their unique structures and various potential applications. To date, IFNPs have been made from numerous compounds with layered two-dimensional structures, based on various synthetic methods. Here we have demonstrated for the first time that inorganic fullerene-like molybdenum selenide nanoparticles (MoSe 2 IFNPs) can be synthesized by laser ablating a molybdenum selenide target in 30 vol % ethanol/water mixture at ambient temperature and pressure. The formation mechanism was proposed to elucidate the production of MoSe 2 IFNPs in the process of laser ablation in liquids (LAL). The appropriate solvent facilitates the condensation of the plasma plume created by LAL to planar MoSe 2 . Then, laser-induced high temperature and high pressure lead to the formation of a vacancy in the planar MoSe 2 , causing the generation of nucleation and growth of the MoSe 2 IFNPs. In addition, a CCK-8 (cell counting kit-8) assay and a cell viability assay were performed to examine the cytotoxic behavior and the effect on cell viability of MoSe 2 IFNPs. The results show that MoSe 2 IFNPs are reasonably nontoxic and biocompatible with the given cells, showing they have significant potential in biomedical applications.

  13. Epicardial Radiofrequency Ablation Failure During Ablation Procedures for Ventricular Arrhythmias: Reasons and Implications for Outcomes.

    PubMed

    Baldinger, Samuel H; Kumar, Saurabh; Barbhaiya, Chirag R; Mahida, Saagar; Epstein, Laurence M; Michaud, Gregory F; John, Roy; Tedrow, Usha B; Stevenson, William G

    2015-12-01

    Radiofrequency ablation (RFA) from the epicardial space for ventricular arrhythmias is limited or impossible in some cases. Reasons for epicardial ablation failure and the effect on outcome have not been systematically analyzed. We assessed reasons for epicardial RFA failure relative to the anatomic target area and the type of heart disease and assessed the effect of failed epicardial RFA on outcome after ablation procedures for ventricular arrhythmias in a large single-center cohort. Epicardial access was attempted during 309 ablation procedures in 277 patients and was achieved in 291 procedures (94%). Unlimited ablation in an identified target region could be performed in 181 cases (59%), limited ablation was possible in 22 cases (7%), and epicardial ablation was deemed not feasible in 88 cases (28%). Reasons for failed or limited ablation were unsuccessful epicardial access (6%), failure to identify an epicardial target (15%), proximity to a coronary artery (13%), proximity to the phrenic nerve (6%), and complications (<1%). Epicardial RFA was impeded in the majority of cases targeting the left ventricular summit region. Acute complications occurred in 9%. The risk for acute ablation failure was 8.3× higher (4.5-15.0; P<0.001) after no or limited epicardial RFA compared with unlimited RFA, and patients with unlimited epicardial RFA had better recurrence-free survival rates (P<0.001). Epicardial RFA for ventricular arrhythmias is often limited even when pericardial access is successful. Variability of success is dependent on the target area, and the presence of factors limiting ablation is associated with worse outcomes. © 2015 American Heart Association, Inc.

  14. Tidal modulation on the Changjiang River plume in summer

    NASA Astrophysics Data System (ADS)

    WU, H.

    2011-12-01

    Tide effects on the structure of the near-field Changjiang River Plume and on the extension of the far-field plume have often been neglected in analysis and numerical simulations, which is the focus of this study. Numerical experiments highlighted the crucial role of the tidal forcing in modulating the Changjiang River plume. Without the tidal forcing, the plume results in an unrealistic upstream extension along the Jiangsu Coast. With the tidal forcing, the vertical mixing increases, resulting in a strong horizontal salinity gradient at the northern side of the Changjiang River mouth along the Jiangsu Coast, which acts as a dynamic barrier and restricts the northward migration of the plume. Furthermore, the tidal forcing produces a bi-directional plume structure in the near field and the plume separation is located at the head of the submarine canyon. A significant bulge occurs around the head of submarine canyon and rotates anticyclonically, which carries large portion of the diluted water towards the northeast and merges into the far-field plume. A portion of the diluted water moves towards the southeast, which is mainly caused by tidal ratification. This bi-directional plume structure is more evident under certain wind condition. During the neap tide with the reduced tidal energy, the near-field plume extends farther offshore and the bulge becomes less evident. These dynamic behaviors are maintained and fundamentally important in the region around the river mouth even under the summer monsoon and the shelf currents, although in the far field the wind forcing and shelf currents eventually dominate the plume extension.
    H. Wu

  15. Outcomes of repeat catheter ablation using magnetic navigation or conventional ablation.

    PubMed

    Akca, Ferdi; Theuns, Dominic A M J; Abkenari, Lara Dabiri; de Groot, Natasja M S; Jordaens, Luc; Szili-Torok, Tamas

    2013-10-01

    After initial catheter ablation, repeat procedures could be necessary. This study evaluates the efficacy of the magnetic navigation system (MNS) in repeat catheter ablation as compared with manual conventional techniques (MANs). The results of 163 repeat ablation procedures were analysed. Ablations were performed either using MNS (n = 84) or conventional manual ablation (n = 79). Procedures were divided into four groups based on the technique used during the initial and repeat ablation procedure: MAN-MAN (n = 66), MAN-MNS (n = 31), MNS-MNS (n = 53), and MNS-MAN (n = 13). Three subgroups were analysed: supraventricular tachycardias (SVTs, n = 68), atrial fibrillation (AF, n = 67), and ventricular tachycardias (VT, n = 28). Recurrences were assessed during 19 ± 11 months follow-up. Overall, repeat procedures using MNS were successful in 89.0% as compared with 96.2% in the MAN group (P = ns). The overall recurrence rate was significantly lower using MNS (25.0 vs. 41.4%, P = 0.045). Acute success and recurrence rates for the MAN-MAN, MAN-MNS, MNS-MNS, and MNS-MAN groups were comparable. For the SVT subgroup a higher acute success rate was achieved using MAN (87.9 vs. 100.0%, P = 0.049). The use of MNS for SVT is associated with longer procedure times (205 ± 82 vs. 172 ± 69 min, P = 0.040). For AF procedure and fluoroscopy times were longer (257 ± 72 vs. 185 ± 64, P = 0.001; 59.5 ± 19.3 vs. 41.1 ± 18.3 min, P < 0.001). Less fluoroscopy was used for MNS-guided VT procedures (22.8 ± 14.7 vs. 41.2 ± 10.9, P = 0.011). Our data suggest that overall MNS is comparable with MAN in acute success after repeat catheter ablation. However, MNS is related to fewer recurrences as compared with MAN.

  16. Lidar sounding of volcanic plumes

    NASA Astrophysics Data System (ADS)

    Fiorani, Luca; Aiuppa, Alessandro; Angelini, Federico; Borelli, Rodolfo; Del Franco, Mario; Murra, Daniele; Pistilli, Marco; Puiu, Adriana; Santoro, Simone

    2013-10-01

    Accurate knowledge of gas composition in volcanic plumes has high scientific and societal value. On the one hand, it gives information on the geophysical processes taking place inside volcanos; on the other hand, it provides alert on possible eruptions. For this reasons, it has been suggested to monitor volcanic plumes by lidar. In particular, one of the aims of the FP7 ERC project BRIDGE is the measurement of CO2 concentration in volcanic gases by differential absorption lidar. This is a very challenging task due to the harsh environment, the narrowness and weakness of the CO2 absorption lines and the difficulty to procure a suitable laser source. This paper, after a review on remote sensing of volcanic plumes, reports on the current progress of the lidar system.

  17. Enceladus Plumes: Causes of Decadal Variability

    NASA Astrophysics Data System (ADS)

    Ingersoll, Andrew P.; Ewald, Shawn P.

    2016-10-01

    The Enceladus plumes have decreased over the decade that Cassini has been observing them. This long-term variation is superposed on the much shorter-term variation tied to the position of Enceladus in its orbit around Saturn. The observations are ISS and VIMS images, which reveal the particles in the plumes but not the gas. The decadal variability largely consists of a 2-fold decline in the mass of plume material, but there is a hint of a recent turnaround. Here we offer three hypotheses, each with its strengths and weaknesses, to explain the long-term variability. The first is seasonal change, from summer to fall in the southern hemisphere. The loss of sunlight could increase the build-up of ice around the tiger stripes. The weakness is that the sunlight is likely to have a small effect, e.g., decreasing the sublimation rate of the ice by only ~1 cm/year. The second hypothesis is a statistical fluctuation in the number of active plumes, which tend to turn themselves off due to build-up of ice at the throat of the vent. The weakness is that the plumes are likely to fluctuate independently, and if there are ~100 plumes, their sum will only fluctuate by 10%. The third hypothesis is that the variation is part of a well-known decadal cycle of orbital eccentricity, which varies by ±2.5% around a mean of 0.0047. The peak eccentricity occurred in 2009-2010, and the minimum occurred in 2015. Since eccentricity controls the short-term orbital cycle variations, it could also control the longer-term decadal variations. The weakness is that the eccentricity variation is small, from 0.0046 to 0.0048. It is not certain that such a small variation could cause a 2-fold variation in the strength of the plumes. An independent study, still in its infancy, is the possibility that liquid water reaches the surface during part of the orbital cycle.

  18. The thin hot plume beneath Iceland

    USGS Publications Warehouse

    Allen, R.M.; Nolet, G.; Morgan, W.J.; Vogfjord, K.; Bergsson, B.H.; Erlendsson, P.; Foulger, G.R.; Jakobsdottir, S.; Julian, B.R.; Pritchard, M.; Ragnarsson, S.; Stefansson, R.

    1999-01-01

    We present the results of a seismological investigation of the frequency-dependent amplitude variations across Iceland using data from the HOTSPOT array currently deployed there. The array is composed of 30 broad-band PASSCAL instruments. We use the parameter t(*), defined in the usual manner from spectral ratios (Halderman and Davis 1991), to compare observed S-wave amplitude variations with those predicted due to both anelastic attenuation and diffraction effects. Four teleseismic events at a range of azimuths are used to measure t(*). A 2-D vertical cylindrical plume model with a Gaussian-shaped velocity anomaly is used to model the variations. That part of t(*) caused by attenuation was estimated by tracing a ray through IASP91, then superimposing our plume model velocity anomaly and calculating the path integral of 1/vQ. That part of t(*) caused by diffraction was estimated using a 2-D finite difference code to generate synthetic seismograms. The same spectral ratio technique used for the data was then used to extract a predicted t(*). The t(*) variations caused by anelastic attenuation are unable to account for the variations we observe, but those caused by diffraction do. We calculate the t(*) variations caused by diffraction for different plume models and obtain our best-fit plume, which exhibits good agreement between the observed and measured t(*). The best-fit plume model has a maximum S-velocity anomaly of - 12 per cent and falls to 1/e of its maximum at 100 km from the plume centre. This is narrower than previous estimates from seismic tomography, which are broadened and damped by the methods of tomography. This velocity model would suggest greater ray theoretical traveltime delays than observed. However, we find that for such a plume, wave-front healing effects at frequencies of 0.03-0.175 Hz (the frequency range used to pick S-wave arrivals) causes a 40 per cent reduction in traveltime delay, reducing the ray theoretical delay to that observed.

  19. Rocket exhaust plume computer program improvement. Volume 1: Summary: Method of characteristics nozzle and plume programs

    NASA Technical Reports Server (NTRS)

    Ratliff, A. W.; Smith, S. D.; Penny, N. M.

    1972-01-01

    A summary is presented of the various documents that discuss and describe the computer programs and analysis techniques which are available for rocket nozzle and exhaust plume calculations. The basic method of characteristics program is discussed, along with such auxiliary programs as the plume impingement program, the plot program and the thermochemical properties program.

  20. Capability of MODIS radiance to analyze Iberian turbid plumes

    NASA Astrophysics Data System (ADS)

    Fernandez-Novoa, Diego; deCastro, Maite; Des, Marisela; Costoya, Xurxo; Mendes, Renato; Gomez-Gesteira, Moncho

    2017-04-01

    River plumes are formed near river mouths by freshwater and riverine materials. Therefore, the area influenced by freshwater (salinity plume) is usually negatively correlated with the area occupied by suspension and dissolved material (turbid plume). Suspended material results in a strong signal detected by satellite sensors whereas ocean clear waters have negligible contributions. Thus, remote sensing data, such as radiance obtained from Moderate Resolution Imaging Spectroradiometer (MODIS), are a very useful tool to analyze turbid plumes due to the high spatial and time resolution provided. Here, MODIS capability for characterizing similarities and differences among the most important Iberian plumes was assessed under the influence of their main forcing. Daily radiance data from MODIS-Aqua and MODIS-Terra satellite sensors were processed obtaining a resolution of 500 m. Two approaches are usually used for atmospheric correction treatments: Near-Infrared (NIR) bands and a combined algorithm using NIR and Short Wave Infrared (SWIR) bands. In the particular case of Iberian Peninsula plumes both methods offered similar results, although NIR bands present a lower associated error. MODIS allows working with several bands of normalized water-leaving radiances (nLw). Focusing in the resolution provided, nLw555 and 645 were the most appropriate because both provide the best coverage and correlation with river discharge. The nLw645 band was chosen because has a lower water penetration avoiding overestimations of turbidity caused by shallow seafloor areas and/or upwelling blooms. Daily data from both satellites were merged to enhance the robustness and precision of the study by increasing the number of available pixels. Results indicate that differences between radiance data from both satellites are negligible for Iberian plumes, justifying the merging. By last, each turbid limit, to delimit the respective plume from adjacent seawater, was obtained using two alternative

  1. Saharan dust plume charging observed over the UK

    NASA Astrophysics Data System (ADS)

    Harrison, R. Giles; Nicoll, Keri A.; Marlton, Graeme J.; Ryder, Claire L.; Bennett, Alec J.

    2018-05-01

    A plume of Saharan dust and Iberian smoke was carried across the southern UK on 16th October 2017, entrained into an Atlantic cyclone which had originated as Hurricane Ophelia. The dust plume aloft was widely noticed as it was sufficiently dense to redden the visual appearance of the sun. Time series of backscatter from ceilometers at Reading and Chilbolton show two plumes: one carried upwards to 2.5 km, and another below 800 m into the boundary layer, with a clear slot between. Steady descent of particles at about 50 cm s‑1 continued throughout the morning, and coarse mode particles reached the surface. Plumes containing dust are frequently observed to be strongly charged, often through frictional effects. This plume passed over atmospheric electric field sensors at Bristol, Chilbolton and Reading. Consistent measurements at these three sites indicated negative plume charge. The lower edge plume charge density was (‑8.0 ± 3.3) nC m‑2, which is several times greater than that typical for stratiform water clouds, implying an active in situ charge generation mechanism such as turbulent triboelectrification. A meteorological radiosonde measuring temperature and humidity was launched into the plume at 1412 UTC, specially instrumented with charge and turbulence sensors. This detected charge in the boundary layer and in the upper plume region, and strong turbulent mixing was observed throughout the atmosphere’s lowest 4 km. The clear slot region, through which particles sedimented, was anomalously dry compared with modelled values, with water clouds forming intermittently in the air beneath. Electrical aspects of dust should be included in numerical models, particularly the charge-related effects on cloud microphysical properties, to accurately represent particle behaviour and transport.

  2. 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.

  3. Rocket Engine Plume Diagnostics at Stennis Space Center

    NASA Technical Reports Server (NTRS)

    Tejwani, Gopal D.; Langford, Lester A.; VanDyke, David B.; McVay, Gregory P.; Thurman, Charles C.

    2003-01-01

    The Stennis Space Center has been at the forefront of development and application of exhaust plume spectroscopy to rocket engine health monitoring since 1989. Various spectroscopic techniques, such as emission, absorption, FTIR, LIF, and CARS, have been considered for application at the engine test stands. By far the most successful technology h a been exhaust plume emission spectroscopy. In particular, its application to the Space Shuttle Main Engine (SSME) ground test health monitoring has been invaluable in various engine testing and development activities at SSC since 1989. On several occasions, plume diagnostic methods have successfully detected a problem with one or more components of an engine long before any other sensor indicated a problem. More often, they provide corroboration for a failure mode, if any occurred during an engine test. This paper gives a brief overview of our instrumentation and computational systems for rocket engine plume diagnostics at SSC. Some examples of successful application of exhaust plume spectroscopy (emission as well as absorption) to the SSME testing are presented. Our on-going plume diagnostics technology development projects and future requirements are discussed.

  4. 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.

  5. The relative effects of particles and turbulence on acoustic scattering from deep-sea hydrothermal vent plumes.

    PubMed

    Xu, Guangyu; Di Iorio, Daniela

    2011-10-01

    Acoustic methods are applied to the investigation and monitoring of a vigorous hydrothermal plume within the Main Endeavor vent field at the Endeavor segment of the Juan de Fuca Ridge. Forward propagation and scattering from suspended particulates using Rayleigh scattering theory is shown to be negligible (log-amplitude variance σ(χ) (2)~10(-7)) compared to turbulence induced by temperature fluctuations (σ(χ) (2)~0.1). The backscattering from turbulence is then quantified using the forward scattering derived turbulence level, which gives a volume backscattering strength of s(V)=6.5 × 10(-8) m(-1). The volume backscattering cross section from particulates can range from s(V)=3.3 × 10(-6) to 7.2 × 10(-10) m(-1) depending on the particle size. These results show that forward scatter acoustic methods in hydrothermal vent applications can be used to quantify turbulence and its effect on backscatter measurements, which can be a dominant factor depending on the particle size and its location within the plume. © 2011 Acoustical Society of America

  6. Space Shuttle Plume Simulation Effect on Aerodynamics

    NASA Technical Reports Server (NTRS)

    Hair, L. M.

    1978-01-01

    Technology for simulating plumes in wind tunnel tests was not adequate to provide the required confidence in test data where plume induced aerodynamic effects might be significant. A broad research program was undertaken to correct the deficiency. Four tasks within the program are reported. Three of these tasks involve conducting experiments, related to three different aspects of the plume simulation problem: (1) base pressures; (2) lateral jet pressures; and (3) plume parameters. The fourth task involves collecting all of the base pressure test data generated during the program. Base pressures were measured on a classic cone ogive cylinder body as affected by the coaxial, high temperature exhaust plumes of a variety of solid propellant rockets. Valid data were obtained at supersonic freestream conditions but not at transonic. Pressure data related to lateral (separation) jets at M infinity = 4.5, for multiple clustered nozzles canted to the freestream and operating at high dynamic pressure ratios. All program goals were met although the model hardware was found to be large relative to the wind tunnel size so that operation was limited for some nozzle configurations.

  7. Chemical Plume Detection with an Iterative Background Estimation Technique

    DTIC Science & Technology

    2016-05-17

    schemes because of contamination of background statistics by the plume. To mitigate the effects of plume contamination , a first pass of the detector...can be used to create a background mask. However, large diffuse plumes are typically not removed by a single pass. Instead, contamination can be...is estimated using plume-pixels, the covariance matrix is contaminated and detection performance may be significantly reduced. To avoid Further author

  8. Investigation of solid plume simulation criteria to produce flight plume effects on multibody configuration in wind tunnel tests

    NASA Technical Reports Server (NTRS)

    Frost, A. L.; Dill, C. C.

    1986-01-01

    An investigation to determine the sensitivity of the space shuttle base and forebody aerodynamics to the size and shape of various solid plume simulators was conducted. Families of cones of varying angle and base diameter, at various axial positions behind a Space Shuttle launch vehicle model, were wind tunnel tested. This parametric evaluation yielded base pressure and force coefficient data which indicated that solid plume simulators are an inexpensive, quick method of approximating the effect of engine exhaust plumes on the base and forebody aerodynamics of future, complex multibody launch vehicles.

  9. Triton's Geyser-like Plumes

    NASA Astrophysics Data System (ADS)

    Brown, Robert H.; Soderblom, Laurence A.

    In August of 1989, while flying by Neptune's largest satellite Triton, Voyager 2 made another of its stunning discoveries in its epic journey through the outer solar system. First seen by one of us (LAS) and Tammy Becker (also of the USGS), after stereoscopic examination of a group of images taken very near Voyager's closest approach to the satellite, were at least two, geyser-like plumes spewing almost perfectly vertical columns of material 1-km across roughly 8-km high into Triton's atmosphere; there the columns were sheared by stratospheric winds into 100-km-long, dark clouds thought to composed of condensed nitrogen mixed with organic particles. Triton's plumes may be the most unique of all the manifestations of geologic activity on satellites in the outer solar system in that their energy source may be sunlight trapped below Triton's surface in a so-called "solid-state greenhouse". This talk will focus on the physical characteristics of those plumes, and on the various mechanisms proposed to explain their presence and apparent persistence on Triton.

  10. Ion acceleration enhanced by target ablation

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

    Zhao, S.; State Key Laboratory of Nuclear Physics and Technology, and Key Lab of HEDPS, CAPT, Peking University, Beijing 100871; Institute of Radiation, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden

    2015-07-15

    Laser proton acceleration can be enhanced by using target ablation, due to the energetic electrons generated in the ablation preplasma. When the ablation pulse matches main pulse, the enhancement gets optimized because the electrons' energy density is highest. A scaling law between the ablation pulse and main pulse is confirmed by the simulation, showing that for given CPA pulse and target, proton energy improvement can be achieved several times by adjusting the target ablation.

  11. Geological factors affecting CO2 plume distribution

    USGS Publications Warehouse

    Frailey, S.M.; Leetaru, H.

    2009-01-01

    Understanding the lateral extent of a CO2 plume has important implications with regards to buying/leasing pore volume rights, defining the area of review for an injection permit, determining the extent of an MMV plan, and managing basin-scale sequestration from multiple injection sites. The vertical and lateral distribution of CO2 has implications with regards to estimating CO2 storage volume at a specific site and the pore pressure below the caprock. Geologic and flow characteristics such as effective permeability and porosity, capillary pressure, lateral and vertical permeability anisotropy, geologic structure, and thickness all influence and affect the plume distribution to varying degrees. Depending on the variations in these parameters one may dominate the shape and size of the plume. Additionally, these parameters do not necessarily act independently. A comparison of viscous and gravity forces will determine the degree of vertical and lateral flow. However, this is dependent on formation thickness. For example in a thick zone with injection near the base, the CO2 moves radially from the well but will slow at greater radii and vertical movement will dominate. Generally the CO2 plume will not appreciably move laterally until the caprock or a relatively low permeability interval is contacted by the CO2. Conversely, in a relatively thin zone with the injection interval over nearly the entire zone, near the wellbore the CO2 will be distributed over the entire vertical component and will move laterally much further with minimal vertical movement. Assuming no geologic structure, injecting into a thin zone or into a thick zone immediately under a caprock will result in a larger plume size. With a geologic structure such as an anticline, CO2 plume size may be restricted and injection immediately below the caprock may have less lateral plume growth because the structure will induce downward vertical movement of the CO2 until the outer edge of the plume reaches a spill

  12. Learning to Rapidly Re-Contact the Lost Plume in Chemical Plume Tracing

    PubMed Central

    Cao, Meng-Li; Meng, Qing-Hao; Wang, Jia-Ying; Luo, Bing; Jing, Ya-Qi; Ma, Shu-Gen

    2015-01-01

    Maintaining contact between the robot and plume is significant in chemical plume tracing (CPT). In the time immediately following the loss of chemical detection during the process of CPT, Track-Out activities bias the robot heading relative to the upwind direction, expecting to rapidly re-contact the plume. To determine the bias angle used in the Track-Out activity, we propose an online instance-based reinforcement learning method, namely virtual trail following (VTF). In VTF, action-value is generalized from recently stored instances of successful Track-Out activities. We also propose a collaborative VTF (cVTF) method, in which multiple robots store their own instances, and learn from the stored instances, in the same database. The proposed VTF and cVTF methods are compared with biased upwind surge (BUS) method, in which all Track-Out activities utilize an offline optimized universal bias angle, in an indoor environment with three different airflow fields. With respect to our experimental conditions, VTF and cVTF show stronger adaptability to different airflow environments than BUS, and furthermore, cVTF yields higher success rates and time-efficiencies than VTF. PMID:25825974

  13. The interaction of Io's plumes and sublimation atmosphere

    NASA Astrophysics Data System (ADS)

    McDoniel, William J.; Goldstein, David B.; Varghese, Philip L.; Trafton, Laurence M.

    2017-09-01

    Io's volcanic plumes are the ultimate source of its SO2 atmosphere, but past eruptions have covered the moon in surface frost which sublimates in sunlight. Today, Io's atmosphere is a result of some combination of volcanism and sublimation, but it is unknown exactly how these processes work together to create the observed atmosphere. We use the direct simulation Monte Carlo (DSMC) method to model the interaction of giant plumes with a sublimation atmosphere. Axisymmetric plume/atmosphere simulations demonstrate that the total mass of SO2 above Io's surface is only poorly approximated as the sum of independent volcanic and sublimated components. A simple analytic model is developed to show how variation in the mass of erupting gas above Io's surface can counteract variation in the mass of its hydrostatic atmosphere as surface temperature changes over a Jupiter year. Three-dimensional, unsteady simulations of giant plumes over an Io day are also presented, showing how plume material becomes suspended in the sublimation atmosphere. We find that a plume which produces some total mass above Io's surface at night will cause a net increase in the noon-time atmosphere of only a fraction of the night-time value. However, as much as seven times the night-side mass of the plume will become suspended in the sublimation atmosphere, altering its composition and displacing sublimated material.

  14. Laboratory Simulations of Micrometeoroid Ablation

    NASA Astrophysics Data System (ADS)

    Thomas, Evan Williamson

    Each day, several tons of meteoric material enters Earth's atmosphere, the majority of which consist of small dust particles (micrometeoroids) that completely ablate at high altitudes. The dust input has been suggested to play a role in a variety of phenomena including: layers of metal atoms and ions, nucleation of noctilucent clouds, effects on stratospheric aerosols and ozone chemistry, and the fertilization of the ocean with bio-available iron. Furthermore, a correct understanding of the dust input to the Earth provides constraints on inner solar system dust models. Various methods are used to measure the dust input to the Earth including satellite detectors, radar, lidar, rocket-borne detectors, ice core and deep-sea sediment analysis. However, the best way to interpret each of these measurements is uncertain, which leads to large uncertainties in the total dust input. To better understand the ablation process, and thereby reduce uncertainties in micrometeoroid ablation measurements, a facility has been developed to simulate the ablation of micrometeoroids in laboratory conditions. An electrostatic dust accelerator is used to accelerate iron particles to relevant meteoric velocities (10-70 km/s). The particles are then introduced into a chamber pressurized with a target gas, and they partially or completely ablate over a short distance. An array of diagnostics then measure, with timing and spatial resolution, the charge and light that is generated in the ablation process. In this thesis, we present results from the newly developed ablation facility. The ionization coefficient, an important parameter for interpreting meteor radar measurements, is measured for various target gases. Furthermore, experimental ablation measurements are compared to predictions from commonly used ablation models. In light of these measurements, implications to the broader context of meteor ablation are discussed.

  15. Hubble Captures Volcanic Eruption Plume From Io

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The Hubble Space Telescope has snapped a picture of a 400-km-high (250-mile-high) plume of gas and dust from a volcanic eruption on Io, Jupiter's large innermost moon.

    Io was passing in front of Jupiter when this image was taken by the Wide Field and Planetary Camera 2 in July 1996. The plume appears as an orange patch just off the edge of Io in the eight o'clock position, against the blue background of Jupiter's clouds. Io's volcanic eruptions blasts material hundreds of kilometers into space in giant plumes of gas and dust. In this image, material must have been blown out of the volcano at more than 2,000 mph to form a plume of this size, which is the largest yet seen on Io.

    Until now, these plumes have only been seen by spacecraft near Jupiter, and their detection from the Earth-orbiting Hubble Space Telescope opens up new opportunities for long-term studies of these remarkable phenomena.

    The plume seen here is from Pele, one of Io's most powerful volcanos. Pele's eruptions have been seen before. In March 1979, the Voyager 1 spacecraft recorded a 300-km-high eruption cloud from Pele. But the volcano was inactive when the Voyager 2 spacecraft flew by Jupiter in July 1979. This Hubble observation is the first glimpse of a Pele eruption plume since the Voyager expeditions.

    Io's volcanic plumes are much taller than those produced by terrestrial volcanos because of a combination of factors. The moon's thin atmosphere offers no resistance to the expanding volcanic gases; its weak gravity (one-sixth that of Earth) allows material to climb higher before falling; and its biggest volcanos are more powerful than most of Earth's volcanos.

    This image is a contrast-enhanced composite of an ultraviolet image (2600 Angstrom wavelength), shown in blue, and a violet image (4100 Angstrom wavelength), shown in orange. The orange color probably occurs because of the absorption and/or scattering of ultraviolet light in the plume. This light from Jupiter passes through

  16. Elastic plate flexure above mantle plumes explains the upstream offset of volcanic activity at la Réunion and Hawaii

    NASA Astrophysics Data System (ADS)

    Gerbault, Muriel; Fontaine, Fabrice; Rabinowicz, Michel; Bystricky, Micha

    2017-04-01

    Surface volcanism at la Réunion and Hawaii occurs with an offset of 150-180 km upstream to the plume axis with respect to the plate motion. This striking observation raises questions about the forcing of plume-lithosphere thermo-mechanical interactions on melt trajectories beneath these islands. Based on visco-elasto-plastic numerical models handled at kilometric resolution, we propose to explain this offset by the development of compressional stresses at the base of the lithosphere, that result from elastic plate bending above the upward load exerted by the plume head. This horizontal compression adopts a disc shape centered around the plume axis, 20 km thick and 150 km in radius, at 50-70 km depth where the temperature varies from 600°C to 750°C. It lasts for 5 to 10 My in an oceanic plate of age greater than 70 My, a timing that is controlled by the visco-elastic relaxation time at 50-70 km depth. This period of time exceeds the time during which both the Somalian/East-African and Pacific plates drift over the Reunion and Hawaii plumes, respectively, thus rendering this basal compression a persistent feature. It is inferred that the buoyant melts percolating in the plume head pond below this zone of compression and eventually spread laterally until the most compressive principal elastic stresses reverse to the vertical, i.e., 150 km away from the plume head. There, melts propagate through dikes upwards to 35 km depth, where the plate curvature reverses and ambient compression diminishes. This 30-35 km depth may thus host magmatic reservoirs where melts pond, until further differentiation can relaunch ascension up to the surface and form a volcanic edifice. In a second stage, as the volcano grows because of melt accumulation at the top of the plate, the lithosphere is flexed downwards, inducing extra tensile stress at 30-35 km depth and compression at 15 km depth. It implies that now the melts pond at 15 km and form another magmatic reservoir lying just

  17. The He isotope composition of the earliest picrites erupted by the Ethiopia plume, implications for mantle plume source

    NASA Astrophysics Data System (ADS)

    Stuart, Finlay; Rogers, Nick; Davies, Marc

    2016-04-01

    The earliest basalts erupted by mantle plumes are Mg-rich, and typically derived from mantle with higher potential temperature than those derived from the convecting upper mantle at mid-ocean ridges and ocean islands. The chemistry and isotopic composition of picrites from CFB provide constraints on the composition of deep Earth and thus the origin and differentiation history. We report new He-Sr-Nd-Pb isotopic composition of the picrites from the Ethiopian flood basalt province from the Dilb (Chinese Road) section. They are characterized by high Fe and Ti contents for MgO = 10-22 wt. % implying that the parent magma was derived from a high temperature low melt fraction, most probably from the Afar plume head. The picrite 3He/4He does not exceed 21 Ra, and there is a negative correlation with MgO, the highest 3He/4He corresponding to MgO = 15.4 wt. %. Age-corrected 87Sr/86Sr (0.70392-0.70408) and 143Nd/144Nd (0.512912-0.512987) display little variation and are distinct from MORB and OIB. Age-corrected Pb isotopes display a significant range (e.g. 206Pb/204Pb = 18.70-19.04) and plot above the NHRL. These values contrast with estimates of the modern Afar mantle plume which has lower 3He/4He and Sr, Nd and Pb isotope ratios that are more comparable with typical OIB. These results imply either interaction between melts derived from the Afar mantle plume and a lithospheric component, or that the original Afar mantle plume had a rather unique radiogenic isotope composition. Regardless of the details of the origins of this unusual signal, our observations place a minimum 3He/4He value of 21 Ra for the Afar mantle plume, significantly greater than the present day value of 16 Ra, implying a significant reduction over 30 Myr. In addition the Afar source was less degassed than convecting mantle but more degassed than mantle sampled by the proto-Iceland plume (3He/4He ~50 Ra). This suggests that the largest mantle plumes are not sourced in a single deep mantle domain with a

  18. Ventricular fibrillation occurring after atrioventricular node ablation despite minimal difference between pre- and post-ablation heart rates.

    PubMed

    Squara, F; Theodore, G; Scarlatti, D; Ferrari, E

    2017-02-01

    We report the case of an 82-year-old man presenting with ventricular fibrillation (VF) occurring acutely after atrioventricular node (AVN) ablation. This patient had severe valvular cardiomyopathy, chronic atrial fibrillation (AF), and underwent prior to the AVN ablation a biventricular implantable cardiac defibrillator positioning. The VF was successfully cardioverted with one external electrical shock. What makes this presentation original is that the pre-ablation spontaneous heart rate in AF was slow (84 bpm), and that VF occurred after ablation despite a minimal heart rate drop of only 14 bpm. VF is the most feared complication of AVN ablation, but it had previously only been described in case of acute heart rate drop after ablation of at least 30 bpm (and more frequently>50 bpm). This case report highlights the fact that VF may occur after AVN ablation regardless of the heart rate drop, rendering temporary fast ventricular pacing mandatory whatever the pre-ablation heart rate. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  19. Thermal Ablation of T1c Renal Cell Carcinoma: A Comparative Assessment of Technical Performance, Procedural Outcome, and Safety of Microwave Ablation, Radiofrequency Ablation, and Cryoablation.

    PubMed

    Zhou, Wenhui; Arellano, Ronald S

    2018-04-06

    To evaluate perioperative outcomes of thermal ablation with microwave (MW), radiofrequency (RF), and cryoablation for stage T1c renal cell carcinoma (RCC). A retrospective analysis of 384 patients (mean age, 71 y; range, 22-88 y) was performed between October 2006 and October 2016. Mean radius, exophytic/endophytic, nearness to collecting system or sinus, anterior/posterior, and location relative to polar lines; preoperative aspects and dimensions used for anatomic classification; and centrality index scores were 6.3, 7.9, and 2.7, respectively. Assessment of pre- and postablation serum blood urea nitrogen, creatinine, and estimated glomerular filtration rate was performed to assess functional outcomes. Linear regression analyses were performed to compare sedation medication dosages among the three treatment cohorts. Univariable and multivariable logistic regression analyses were performed to compare rates of residual disease and complications among treatment modalities. A total of 437 clinical stage T1N0M0 biopsy-proven RCCs measuring 1.2-6.9 cm were treated with computed tomography (CT)-guided MW ablation (n = 44; 10%), RF ablation (n = 347; 79%), or cryoablation (n = 46; 11%). There were no significant differences in patient demographic or tumor characteristics among cohorts. Complication rates and immediate renal function changes were similar among the three ablation modalities (P = .46 and P = .08, respectively). MW ablation was associated with significantly decreased ablation time (P < .05), procedural time (P < .05), and dosage of sedative medication (P < .05) compared with RF ablation and cryoablation. CT-guided percutaneous MW ablation is comparable to RF ablation or cryoablation for the treatment of stage T1N0M0 RCC with regard to treatment response and is associated with shorter treatment times and less sedation than RF ablation or cryoablation. In addition, the safety profile of CT-guided MW ablation is noninferior to those of RF ablation or

  20. Regimes of plume-slab interaction and consequences for hotspot volcanism

    NASA Astrophysics Data System (ADS)

    Druken, Kelsey; Stegman, Dave; Kincaid, Christopher; Griffiths, Ross

    2013-04-01

    "Hotspot" volcanism is generally attributed to upwelling of anomalously warm mantle plumes, the intra-plate Hawaiian island chain and its simple age progression serving as an archetypal example. However, interactions of such plumes with plate margins, and in particular with subduction zones, is likely to have been a common occurrence and leads to more complicated geological records. Here we present results from a series of complementary, three-dimensional numerical and laboratory experiments that examine the dynamic interaction between negatively buoyant subducting slabs and positively buoyant mantle plumes. Slab-driven flow is shown to significantly influence the evolution and morphology of nearby plumes, which leads to a range of deformation regimes of the plume head and conduit. The success or failure of an ascending plume head to reach the lithosphere depends on the combination of plume buoyancy and position within the subduction system, where the mantle flow owing to downdip and rollback components of slab motion entrain plume material both vertically and laterally. Plumes rising within the sub-slab region tend to be suppressed by the surrounding flow field, while wedge-side plumes experience a slight enhancement before ultimately being entrained by subduction. Hotspot motion is more complex than that expected at intraplate settings and is primarily controlled by position alone. Regimes include severely deflected conduits as well as retrograde (corkscrew) motion from rollback-driven flow, often with weak and variable age-progression. The interaction styles and surface manifestations of plumes can be predicted from these models, and the results have important implications for potential hotspot evolution near convergent margins.

  1. A spreading drop model for plumes on Venus

    NASA Astrophysics Data System (ADS)

    Koch, D. M.

    1994-01-01

    Many of the large-scale, plume-related features on Venus can be modeled by a buoyant viscous drop, or plume head, as it rises and spreads laterally below a free fluid surface. The drop has arbitrary density and viscosity contrast and begins as a sphere below the surface of a fluid half space. The boundary integral method is used to solve for the motion of the plume head and for the topography, geoid, and stress at the fluid surface. As the plume approaches the surface, stresses in the fluid above it cause it to spread and become thin below the surface. During the spreading, the surface swell above evolves through various stages whose morphologies resemble several different plume-related features observed on Venus. When the plume head first approaches the surface, a high broad topographic dome develops, with a large geoid, and radial extensional deformation patterns. At later stages, the topography subsides and becomes plateau-like, the geoid to topography ratio (GTR) decreases, and the dominant stress pattern consists of a band of concentric extension surrounded by a band of concentric compression. We find that a low-viscosity model plume head (viscosity that is 0.1 times the mantle viscosity) produces maximum topography that is 20% lower, and swell features which evolve faster, than for an isoviscous plume. We compare model results with both the large-scale highland swells, and smaller-scale features such as coronae and novae. The dome-shaped highlands with large GTRs such as Beta, Atla, and Western Eistla Regiones may be the result of early stage plume motion, while the flatter highlands such as Ovda and Thetis Regiones which have lower GTRs may be later stage features. Comparison of model results with GTR data indicates that the highlands result from plume heads with initial diameters of about 1000 km. On a smaller scale, an evolutionary sequence may begin with novae (domes having radial extensional deformation), followed by features with radial and concentric

  2. A preliminary characterization of applied-field MPD thruster plumes

    NASA Technical Reports Server (NTRS)

    Myers, Roger M.; Wehrle, David; Vernyi, Mark; Biaglow, James; Reese, Shawn

    1991-01-01

    Electric probes, quantitative imaging, and emission spectroscopy were used to study the plume characteristics of applied field magnetohydrodynamic thrusters. The measurements showed that the applied magnetic field plays the dominant role in establishing the plume structure, followed in importance by the cathode geometry and propellant. The anode radius had no measurable impact on the plume characteristics. For all cases studied the plume was highly ionized, though spectral lines of neutral species were always present. Centerline electron densities and temperatures ranged from 2 times 10 (exp 18) to 8 times 10 (exp 18) m(exp -3) and from 7500 to 20,000 K, respectively. The plume was strongly confined by the magnetic field, with radial density gradients increasing monotonically with applied field strength. Plasma potential measurements show a strong effect of the magnetic field on the electrical conductivity and indicate the presence of radial current conduction in the plume.

  3. Io Plume Monitoring (frames 1-36)

    NASA Image and Video Library

    1997-11-04

    A sequence of full disk Io images was taken prior to Galileo's second encounter with Ganymede. The purpose of these observations was to view all longitudes of Io and search for active volcanic plumes. The images were taken at intervals of approximately one hour corresponding to Io longitude increments of about ten degrees. Because both the spacecraft and Io were traveling around Jupiter the lighting conditions on Io (e.g. the phase of Io) changed dramatically during the sequence. These images were registered at a common scale and processed to produce a time-lapse "movie" of Io. This movie combines all of the plume monitoring frames obtained by the Solid State Imaging system aboard NASA's Galileo spacecraft. The most prominent volcanic plume seen in this movie is Prometheus (latitude 1.6 south, longitude 153 west). The plume becomes visible as it moves into daylight, crosses the center of the disk, and is seen in profile against the dark of space at the edge of Io. This plume was first seen by the Voyager 1 spacecraft in 1979 and is believed to be a geyser-like eruption of sulfur dioxide snow and gas. Although details of the region around Prometheus have changed in the seventeen years since Voyager's visit, the shape and height of the plume have not changed significantly. It is possible that this geyser has been erupting nearly continuously over this time. Galileo's primary 24 month mission includes eleven orbits around Jupiter and will provide observations of Jupiter, its moons and its magnetosphere. North is to the top of all frames. The smallest features which can be discerned range from 13 to 31 kilometers across. The images were obtained between the 2nd and the 6th of September, 1996. The animation can be viewed at http://photojournal.jpl.nasa.gov/catalog/PIA01073

  4. Meteorological overview and plume transport patterns during Cal-Mex 2010

    NASA Astrophysics Data System (ADS)

    Bei, Naifang; Li, Guohui; Zavala, Miguel; Barrera, Hugo; Torres, Ricardo; Grutter, Michel; Gutiérrez, Wilfredo; García, Manuel; Ruiz-Suarez, Luis Gerardo; Ortinez, Abraham; Guitierrez, Yaneth; Alvarado, Carlos; Flores, Israel; Molina, Luisa T.

    2013-05-01

    Cal-Mex 2010 Field Study is a US-Mexico collaborative project to investigate cross-border transport of emissions in the California-Mexico border region, which took place from May 15 to June 30, 2010. The current study presents an overview of the meteorological conditions and plume transport patterns during Cal-Mex 2010 based on the analysis of surface and vertical measurements (radiosonde, ceilometers and tethered balloon) conducted in Tijuana, Mexico and the modeling output using a trajectory model (FLEXPRT-WRF) and a regional model (WRF). The WRF model has been applied for providing the meteorological daily forecasts that are verified using the available observations. Both synoptic-scale and urban-scale forecasts (including wind, temperature, and humidity) agree reasonably well with the NCEP-FNL reanalysis data and the measurements; however, the WRF model frequently underestimates surface temperature and planetary boundary layer (PBL) height during nighttime compared to measurements. Based on the WRF-FLEXPART simulations with particles released in Tijuana in the morning, four representative plume transport patterns are identified as “plume-southeast”, “plume-southwest”, “plume-east” and “plume-north”, indicating the downwind direction of the plume; this will be useful for linking meteorological conditions with observed changes in trace gases and particular matter (PM). Most of the days during May and June are classified as plume-east and plume-southeast days, showing that the plumes in Tijuana are mostly carried to the southeast and east of Tijuana within the boundary layer during daytime. The plume transport directions are generally consistent with the prevailing wind directions on 850 hPa. The low level (below 800 m) wind, temperature, and moisture characteristics are different for each plume transport category according to the measurements from the tethered balloon. Future studies (such as using data assimilation and ensemble forecasts) will be

  5. Starting buoyant plumes and vortex ring pinch-off

    NASA Astrophysics Data System (ADS)

    Pottebaum, Tait; Gharib, Mory

    2003-11-01

    The vortex ring formation process of a starting buoyant plume was studied experimentally. Buoyant plumes were produced using a heating element at the base of a water tank. The velocity and temperature fields in the flow were measured using digital particle image thermometry and velocimetry (DPITV), allowing the density and vorticity fields to be determined. The vortex ring initially grew, with additional circulation being supplied by the trailing plume. At later times, the vortex ring became disconnected from the trailing plume. This is analogous to the pinch-off of a vortex ring produced by a piston-cylinder apparatus reported by Gharib et al (1998 JFM 360: 121-140). The existence of a pinch-off process for starting buoyant plumes has many implications for environmental flows. Of particular interest is the effect of vortex ring pinch-off on the dispersal of particulates and contaminants in intermittent or sudden convection events.

  6. Perioral Rejuvenation With Ablative Erbium Resurfacing.

    PubMed

    Cohen, Joel L

    2015-11-01

    Since the introduction of the scanning full-field erbium laser, misconceptions regarding ablative erbium resurfacing have resulted in its being largely overshadowed by ablative fractional resurfacing. This case report illustrates the appropriateness of full-field erbium ablation for perioral resurfacing. A patient with profoundly severe perioral photodamage etched-in lines underwent full-field ablative perioral resurfacing with an erbium laser (Contour TRL, Sciton Inc., Palo Alto, CA) that allows separate control of ablation and coagulation. The pre-procedure consultations included evaluation of the severity of etched-in lines, and discussion of patient goals, expectations, and appropriate treatment options, as well as a review of patient photos and post-treatment care required. The author generally avoids full-field erbium ablation in patients with Fitzpatrick type IV and above. For each of 2 treatment sessions (separated by approximately 4 months), the patient received (12 cc plain 2% lidodaine) sulcus blocks before undergoing 4 passes with the erbium laser at 150 μ ablation, no coagulation, and then some very focal 30 μ ablation to areas of residual lines still visualized through the pinpoint bleeding. Similarly, full-field ablative resurfacing can be very reliable for significant wrinkles and creping in the lower eyelid skin--where often a single treatment of 80 μ ablation, 50 μ coagulation can lead to a nice improvement. Standardized digital imaging revealed significant improvement in deeply etched rhytides without significant adverse events. For appropriately selected patients requiring perioral (or periorbital) rejuvenation, full-field ablative erbium resurfacing is safe, efficacious and merits consideration.

  7. Space-based Observational Constraints for 1-D Plume Rise Models

    NASA Technical Reports Server (NTRS)

    Martin, Maria Val; Kahn, Ralph A.; Logan, Jennifer A.; Paguam, Ronan; Wooster, Martin; Ichoku, Charles

    2012-01-01

    We use a space-based plume height climatology derived from observations made by the Multi-angle Imaging SpectroRadiometer (MISR) instrument aboard the NASA Terra satellite to evaluate the ability of a plume-rise model currently embedded in several atmospheric chemical transport models (CTMs) to produce accurate smoke injection heights. We initialize the plume-rise model with assimilated meteorological fields from the NASA Goddard Earth Observing System and estimated fuel moisture content at the location and time of the MISR measurements. Fire properties that drive the plume-rise model are difficult to estimate and we test the model with four estimates for active fire area and four for total heat flux, obtained using empirical data and Moderate Resolution Imaging Spectroradiometer (MODIS) re radiative power (FRP) thermal anomalies available for each MISR plume. We show that the model is not able to reproduce the plume heights observed by MISR over the range of conditions studied (maximum r2 obtained in all configurations is 0.3). The model also fails to determine which plumes are in the free troposphere (according to MISR), key information needed for atmospheric models to simulate properly smoke dispersion. We conclude that embedding a plume-rise model using currently available re constraints in large-scale atmospheric studies remains a difficult proposition. However, we demonstrate the degree to which the fire dynamical heat flux (related to active fire area and sensible heat flux), and atmospheric stability structure influence plume rise, although other factors less well constrained (e.g., entrainment) may also be significant. Using atmospheric stability conditions, MODIS FRP, and MISR plume heights, we offer some constraints on the main physical factors that drive smoke plume rise. We find that smoke plumes reaching high altitudes are characterized by higher FRP and weaker atmospheric stability conditions than those at low altitude, which tend to remain confined

  8. CONVERGING SUPERGRANULAR FLOWS AND THE FORMATION OF CORONAL PLUMES

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

    Wang, Y.-M.; Warren, H. P.; Muglach, K., E-mail: yi.wang@nrl.navy.mil, E-mail: harry.warren@nrl.navy.mil, E-mail: karin.muglach@nasa.gov

    Earlier studies have suggested that coronal plumes are energized by magnetic reconnection between unipolar flux concentrations and nearby bipoles, even though magnetograms sometimes show very little minority-polarity flux near the footpoints of plumes. Here we use high-resolution extreme-ultraviolet (EUV) images and magnetograms from the Solar Dynamics Observatory (SDO) to clarify the relationship between plume emission and the underlying photospheric field. We find that plumes form where unipolar network elements inside coronal holes converge to form dense clumps, and fade as the clumps disperse again. The converging flows also carry internetwork fields of both polarities. Although the minority-polarity flux is sometimesmore » barely visible in the magnetograms, the corresponding EUV images almost invariably show loop-like features in the core of the plumes, with the fine structure changing on timescales of minutes or less. We conclude that the SDO observations are consistent with a model in which plume emission originates from interchange reconnection in converging flows, with the plume lifetime being determined by the ∼1 day evolutionary timescale of the supergranular network. Furthermore, the presence of large EUV bright points and/or ephemeral regions is not a necessary precondition for the formation of plumes, which can be energized even by the weak, mixed-polarity internetwork fields swept up by converging flows.« less

  9. Wind and tidal forcing of a buoyant plume, Mobile Bay, Alabama

    USGS Publications Warehouse

    Stumpf, R.P.; Gelfenbaum, G.; Pennock, J.R.

    1993-01-01

    AVHRR satellite imagery and in situ observations were combined to study the motion of a buoyant plume at the mouth of Mobile Bay, Alabama. The plume extended up to 30 km from shore, with a thickness of about 1 m. The inner plume, which was 3-8 m thick, moved between the Bay and inner shelf in response to tidal forcing. The tidal prism could be identified through the movement of plume waters between satellite images. The plume responded rapidly to alongshore wind, with sections of the plume moving at speeds of more than 70 cm s-1, about 11% of the wind speed. The plume moved predominantly in the direction of the wind with a weak Ekman drift. The enhanced speed of the plume relative to normal surface drift is probably due to the strong stratification in the plume, which limits the transfer of momentum into the underlying ambient waters. ?? 1993.

  10. RELATIVE ABUNDANCE MEASUREMENTS IN PLUMES AND INTERPLUMES

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

    Guennou, C.; Hahn, M.; Savin, D. W., E-mail: cguennou@iac.es

    2015-07-10

    We present measurements of relative elemental abundances in plumes and interplumes. Plumes are bright, narrow structures in coronal holes that extend along open magnetic field lines far out into the corona. Previous work has found that in some coronal structures the abundances of elements with a low first ionization potential (FIP) <10 eV are enhanced relative to their photospheric abundances. This coronal-to-photospheric abundance ratio, commonly called the FIP bias, is typically 1 for elements with a high-FIP (>10 eV). We have used Extreme Ultraviolet Imaging Spectrometer observations made on 2007 March 13 and 14 over a ≈24 hr period tomore » characterize abundance variations in plumes and interplumes. To assess their elemental composition, we used a differential emission measure analysis, which accounts for the thermal structure of the observed plasma. We used lines from ions of iron, silicon, and sulfur. From these we estimated the ratio of the iron and silicon FIP bias relative to that for sulfur. From the results, we have created FIP-bias-ratio maps. We find that the FIP-bias ratio is sometimes higher in plumes than in interplumes and that this enhancement can be time dependent. These results may help to identify whether plumes or interplumes contribute to the fast solar wind observed in situ and may also provide constraints on the formation and heating mechanisms of plumes.« less

  11. Optimizing smoke and plume rise modeling approaches at local scales

    Treesearch

    Derek V. Mallia; Adam K. Kochanski; Shawn P. Urbanski; John C. Lin

    2018-01-01

    Heating from wildfires adds buoyancy to the overlying air, often producing plumes that vertically distribute fire emissions throughout the atmospheric column over the fire. The height of the rising wildfire plume is a complex function of the size of the wildfire, fire heat flux, plume geometry, and atmospheric conditions, which can make simulating plume rises difficult...

  12. CALIOP-based Biomass Burning Smoke Plume Injection Height

    NASA Astrophysics Data System (ADS)

    Soja, A. J.; Choi, H. D.; Fairlie, T. D.; Pouliot, G.; Baker, K. R.; Winker, D. M.; Trepte, C. R.; Szykman, J.

    2017-12-01

    Carbon and aerosols are cycled between terrestrial and atmosphere environments during fire events, and these emissions have strong feedbacks to near-field weather, air quality, and longer-term climate systems. Fire severity and burned area are under the control of weather and climate, and fire emissions have the potential to alter numerous land and atmospheric processes that, in turn, feedback to and interact with climate systems (e.g., changes in patterns of precipitation, black/brown carbon deposition on ice/snow, alteration in landscape and atmospheric/cloud albedo). If plume injection height is incorrectly estimated, then the transport and deposition of those emissions will also be incorrect. The heights to which smoke is injected governs short- or long-range transport, which influences surface pollution, cloud interaction (altered albedo), and modifies patterns of precipitation (cloud condensation nuclei). We are working with the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) science team and other stakeholder agencies, primarily the Environmental Protection Agency and regional partners, to generate a biomass burning (BB) plume injection height database using multiple platforms, sensors and models (CALIOP, MODIS, NOAA HMS, Langley Trajectory Model). These data have the capacity to provide enhanced smoke plume injection height parameterization in regional, national and international scientific and air quality models. Statistics that link fire behavior and weather to plume rise are crucial for verifying and enhancing plume rise parameterization in local-, regional- and global-scale models used for air quality, chemical transport and climate. Specifically, we will present: (1) a methodology that links BB injection height and CALIOP air parcels to specific fires; (2) the daily evolution of smoke plumes for specific fires; (3) plumes transport and deposited on the Greenland Ice Sheet; and (4) compare CALIOP-derived smoke plume injection

  13. Integrating wildfire plume rises within atmospheric transport models

    NASA Astrophysics Data System (ADS)

    Mallia, D. V.; Kochanski, A.; Wu, D.; Urbanski, S. P.; Krueger, S. K.; Lin, J. C.

    2016-12-01

    Wildfires can generate significant pyro-convection that is responsible for releasing pollutants, greenhouse gases, and trace species into the free troposphere, which are then transported a significant distance downwind from the fire. Oftentimes, atmospheric transport and chemistry models have a difficult time resolving the transport of smoke from these wildfires, primarily due to deficiencies in estimating the plume injection height, which has been highlighted in previous work as the most important aspect of simulating wildfire plume transport. As a result of the uncertainties associated with modeled wildfire plume rise, researchers face difficulties modeling the impacts of wildfire smoke on air quality and constraining fire emissions using inverse modeling techniques. Currently, several plume rise parameterizations exist that are able to determine the injection height of fire emissions; however, the success of these parameterizations has been mixed. With the advent of WRF-SFIRE, the wildfire plume rise and injection height can now be explicitly calculated using a fire spread model (SFIRE) that is dynamically linked with the atmosphere simulated by WRF. However, this model has only been tested on a limited basis due to computational costs. Here, we will test the performance of WRF-SFIRE in addition to several commonly adopted plume parameterizations (Freitas, Sofiev, and Briggs) for the 2013 Patch Springs (Utah) and 2012 Baker Canyon (Washington) fires, for both of which observations of plume rise heights are available. These plume rise techniques will then be incorporated within a Lagrangian atmospheric transport model (STILT) in order to simulate CO and CO2 concentrations during NASA's CARVE Earth Science Airborne Program over Alaska during the summer of 2012. Initial model results showed that STILT model simulations were unable to reproduce enhanced CO concentrations produced by Alaskan fires observed during 2012. Near-surface concentrations were drastically

  14. CT-guided bipolar and multipolar radiofrequency ablation (RF ablation) of renal cell carcinoma: specific technical aspects and clinical results.

    PubMed

    Sommer, C M; Lemm, G; Hohenstein, E; Bellemann, N; Stampfl, U; Goezen, A S; Rassweiler, J; Kauczor, H U; Radeleff, B A; Pereira, P L

    2013-06-01

    This study was designed to evaluate the clinical efficacy of CT-guided bipolar and multipolar radiofrequency ablation (RF ablation) of renal cell carcinoma (RCC) and to analyze specific technical aspects between both technologies. We included 22 consecutive patients (3 women; age 74.2 ± 8.6 years) after 28 CT-guided bipolar or multipolar RF ablations of 28 RCCs (diameter 2.5 ± 0.8 cm). Procedures were performed with a commercially available RF system (Celon AG Olympus, Berlin, Germany). Technical aspects of RF ablation procedures (ablation mode [bipolar or multipolar], number of applicators and ablation cycles, overall ablation time and deployed energy, and technical success rate) were analyzed. Clinical results (local recurrence-free survival and local tumor control rate, renal function [glomerular filtration rate (GFR)]) and complication rates were evaluated. Bipolar RF ablation was performed in 12 procedures and multipolar RF ablation in 16 procedures (2 applicators in 14 procedures and 3 applicators in 2 procedures). One ablation cycle was performed in 15 procedures and two ablation cycles in 13 procedures. Overall ablation time and deployed energy were 35.0 ± 13.6 min and 43.7 ± 17.9 kJ. Technical success rate was 100 %. Major and minor complication rates were 4 and 14 %. At an imaging follow-up of 15.2 ± 8.8 months, local recurrence-free survival was 14.4 ± 8.8 months and local tumor control rate was 93 %. GFR did not deteriorate after RF ablation (50.8 ± 16.6 ml/min/1.73 m(2) before RF ablation vs. 47.2 ± 11.9 ml/min/1.73 m(2) after RF ablation; not significant). CT-guided bipolar and multipolar RF ablation of RCC has a high rate of clinical success and low complication rates. At short-term follow-up, clinical efficacy is high without deterioration of the renal function.

  15. Ejection of Metal Particles into Superfluid 4He by Laser Ablation.

    PubMed

    Buelna, Xavier; Freund, Adam; Gonzalez, Daniel; Popov, Evgeny; Eloranta, Jussi

    2016-10-05

    The dynamics following laser ablation of a metal target immersed in superfluid $^4$He is studied by time-resolved shadowgraph photography. The delayed ejection of hot micrometer-sized particles from the target surface into the liquid was indirectly observed by monitoring the formation and growth of gaseous bubbles around the particles. The experimentally determined particle average velocity distribution appears similar as previously measured in vacuum but exhibits a sharp cutoff at the speed of sound of the liquid. The propagation of the subsonic particles terminates in slightly elongated non-spherical gas bubbles residing near the target whereas faster particles reveal an unusual hydrodynamic response of the liquid. Based on the previously established semi-empirical model developed for macroscopic objects, the ejected transonic particles exhibit supercavitating flow to reduce their hydrodynamic drag. Supersonic particles appear to follow a completely different propagation mechanism as they leave discrete and semi-continuous bubble trails in the liquid. The relatively low number density of the observed non-spherical gas bubbles indicates that only large micron-sized particles are visualized in the experiments. Although the unique properties of superfluid helium allow a detailed characterization of these processes, the developed technique can be used to study the hydrodynamic response of any liquid to fast propagating objects on the micrometer-scale.

  16. On the relative motions of long-lived Pacific mantle plumes.

    PubMed

    Konrad, Kevin; Koppers, Anthony A P; Steinberger, Bernhard; Finlayson, Valerie A; Konter, Jasper G; Jackson, Matthew G

    2018-02-27

    Mantle plumes upwelling beneath moving tectonic plates generate age-progressive chains of volcanos (hotspot chains) used to reconstruct plate motion. However, these hotspots appear to move relative to each other, implying that plumes are not laterally fixed. The lack of age constraints on long-lived, coeval hotspot chains hinders attempts to reconstruct plate motion and quantify relative plume motions. Here we provide 40 Ar/ 39 Ar ages for a newly identified long-lived mantle plume, which formed the Rurutu hotspot chain. By comparing the inter-hotspot distances between three Pacific hotspots, we show that Hawaii is unique in its strong, rapid southward motion from 60 to 50 Myrs ago, consistent with paleomagnetic observations. Conversely, the Rurutu and Louisville chains show little motion. Current geodynamic plume motion models can reproduce the first-order motions for these plumes, but only when each plume is rooted in the lowermost mantle.

  17. 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.

  18. Effects of axisymmetric and normal air jet plumes and solid plume on cylindrical afterbody pressure distributions at Mach numbers from 1.65 to 2.50

    NASA Technical Reports Server (NTRS)

    Covell, P. F.

    1982-01-01

    A wind tunnel investigation of the interference effects of axisymmetric nozzle air plumes, a solid plume, and normal air jet plumes on the afterbody pressure distributions and base pressures of a cylindrical afterbody model was conducted at Mach numbers from 1.65 to 2.50. The axisymmetric nozzles, which varied in exit lip Mach number from 1.7 to 2.7, and the normal air jet nozzle were tested at jet pressure ratios from 1 (jet off) to 615. The tests were conducted at an angle of attack of 0 deg and a Reynolds number per meter of 6.56 million. The results of the investigation show that the solid plume induces greater interference effects than those induced by the axisymmetric nozzle plumes at the selected underexpanded design conditions. A thrust coefficient parameter based on nozzle lip conditons was found to correlate the afterbody disturbance distance and the base pressure between the different axisymmetric nozzles. The normal air jet plume and the solid plume induce afterbody disturbance distances similar to those induced by the axisymmetric air plumes when base pressure is held constant.

  19. Sedimentation from particle-bearing plumes in a stratified ambient

    NASA Astrophysics Data System (ADS)

    Sutherland, Bruce R.; Hong, Youn Sub Dominic

    2016-11-01

    Laboratory experiments are performed to examine the sedimentation of particles that initially rise in a plume, then spread radially and settle in uniformly stratified fluid. Using light attenuation, the depth of the sediment bed is measured nonintrusively as a function of radius from the center of the plume. To gain some insight into these dynamics, an idealized model is developed by adapting well-established plume theory and a theory that accounts for sedimentation from surface gravity currents emanating from a plume impacting a rigid lid. We also account for recycling of falling particles that are re-entrained into the plume. With a suitable choice of parameters determining the intrusion height, entrainment during fountain collapse, and the radius at which settling from the intrusion begins, in most cases for which particles are predicted to be drawn back into the plume and recycled. The predictions for intrusion height, particle mound height, and spread agree within 20% of observations.

  20. Accurately measuring volcanic plume velocity with multiple UV spectrometers

    USGS Publications Warehouse

    Williams-Jones, Glyn; Horton, Keith A.; Elias, Tamar; Garbeil, Harold; Mouginis-Mark, Peter J; Sutton, A. Jeff; Harris, Andrew J. L.

    2006-01-01

    A fundamental problem with all ground-based remotely sensed measurements of volcanic gas flux is the difficulty in accurately measuring the velocity of the gas plume. Since a representative wind speed and direction are used as proxies for the actual plume velocity, there can be considerable uncertainty in reported gas flux values. Here we present a method that uses at least two time-synchronized simultaneously recording UV spectrometers (FLYSPECs) placed a known distance apart. By analyzing the time varying structure of SO2 concentration signals at each instrument, the plume velocity can accurately be determined. Experiments were conducted on Kīlauea (USA) and Masaya (Nicaragua) volcanoes in March and August 2003 at plume velocities between 1 and 10 m s−1. Concurrent ground-based anemometer measurements differed from FLYSPEC-measured plume speeds by up to 320%. This multi-spectrometer method allows for the accurate remote measurement of plume velocity and can therefore greatly improve the precision of volcanic or industrial gas flux measurements.

  1. River plume patterns and dynamics within the Southern California Bight

    USGS Publications Warehouse

    Warrick, J.A.; DiGiacomo, P.M.; Weisberg, S.B.; Nezlin, N.P.; Mengel, M.; Jones, B.H.; Ohlmann, J.C.; Washburn, L.; Terrill, E.J.; Farnsworth, K.L.

    2007-01-01

    Stormwater river plumes are important vectors of marine contaminants and pathogens in the Southern California Bight. Here we report the results of a multi-institution investigation of the river plumes across eight major river systems of southern California. We use in situ water samples from multi-day cruises in combination with MODIS satellite remote sensing, buoy meteorological observations, drifters, and HF radar current measurements to evaluate the dispersal patterns and dynamics of the freshwater plumes. River discharge was exceptionally episodic, and the majority of storm discharge occurred in a few hours. The combined plume observing techniques revealed that plumes commonly detach from the coast and turn to the left, which is the opposite direction of Coriolis influence. Although initial offshore velocity of the buoyant plumes was ∼50 cm/s and was influenced by river discharge inertia (i.e., the direct momentum of the river flux) and buoyancy, subsequent advection of the plumes was largely observed in an alongshore direction and dominated by local winds. Due to the multiple day upwelling wind conditions that commonly follow discharge events, plumes were observed to flow from their respective river mouths to down-coast waters at rates of 20–40 km/d. Lastly, we note that suspended-sediment concentration and beam-attenuation were poorly correlated with plume salinity across and within the sampled plumes (mean r2=0.12 and 0.25, respectively), while colored dissolved organic matter (CDOM) fluorescence was well correlated (mean r2=0.56), suggesting that CDOM may serve as a good tracer of the discharged freshwater in subsequent remote sensing and monitoring efforts of plumes.

  2. Transgenic Reproductive Cell Ablation.

    PubMed

    Lawit, Shai J; Chamberlin, Mark A

    2017-01-01

    Numerous cell ablation technologies are available and have been used in reproductive tissues, particularly for male tissues and cells. The importance of ablation of reproductive tissues is toward a fundamental understanding reproductive tissue development and fertilization, as well as, in developing sterility lines important to breeding strategies. Here, we describe techniques for developing ablation lines for both male and female reproductive cells. Also discussed are techniques for analysis, quality control, maintenance, and the lessening of pleiotropism in such lines.

  3. Atrial Tachycardias Following Atrial Fibrillation Ablation

    PubMed Central

    Sághy, László; Tutuianu, Cristina; Szilágyi, Judith

    2015-01-01

    One of the most important proarrhythmic complications after left atrial (LA) ablation is regular atrial tachycardia (AT) or flutter. Those tachycardias that occur after atrial fibrillation (AF) ablation can cause even more severe symptoms than those from the original arrhythmia prior to the index ablation procedure since they are often incessant and associated with rapid ventricular response. Depending on the method and extent of LA ablation and on the electrophysiological properties of underlying LA substrate, the reported incidence of late ATs is variable. To establish the exact mechanism of these tachycardias can be difficult and controversial but correlates with the ablation technique and in the vast majority of cases the mechanism is reentry related to gaps in prior ablation lines. When tachycardias occur, conservative therapy usually is not effective, radiofrequency ablation procedure is mostly successful, but can be challenging, and requires a complex approach. PMID:25308808

  4. Long-lived plasmaspheric drainage plumes: Where does the plasma come from?

    NASA Astrophysics Data System (ADS)

    Borovsky, Joseph E.; Welling, Daniel T.; Thomsen, Michelle F.; Denton, Michael H.

    2014-08-01

    Long-lived (weeks) plasmaspheric drainage plumes are explored. The long-lived plumes occur during long-lived high-speed-stream-driven storms. Spacecraft in geosynchronous orbit see the plumes as dense plasmaspheric plasma advecting sunward toward the dayside magnetopause. The older plumes have the same densities and local time widths as younger plumes, and like younger plumes they are lumpy in density and they reside in a spatial gap in the electron plasma sheet (in sort of a drainage corridor). Magnetospheric-convection simulations indicate that drainage from a filled outer plasmasphere can only supply a plume for 1.5-2 days. The question arises for long-lived plumes (and for any plume older than about 2 days): Where is the plasma coming from? Three candidate sources appear promising: (1) substorm disruption of the nightside plasmasphere which may transport plasmaspheric plasma outward onto open drift orbits, (2) radial transport of plasmaspheric plasma in velocity-shear-driven instabilities near the duskside plasmapause, and (3) an anomalously high upflux of cold ionospheric protons from the tongue of ionization in the dayside ionosphere, which may directly supply ionospheric plasma into the plume. In the first two cases the plume is drainage of plasma from the magnetosphere; in the third case it is not. Where the plasma in long-lived plumes is coming from is a quandary: to fix this dilemma, further work and probably full-scale simulations are needed.

  5. Femtosecond laser-ablated Fresnel zone plate fiber probe and sensing applications

    NASA Astrophysics Data System (ADS)

    Tan, Xiaoling; Geng, Youfu; Chen, Yan; Li, Shiguo; Wang, Xinzhong

    2018-02-01

    We investigate the Fresnel zone plate (FZP) inscribed on multimode fiber endface using femtosecond laser ablation and its application in sensing. The mode transmission through fiber tips with FZP is investigated both by the beam propagation method theoretically and by measuring the beam images with a charge-coupled device camera experimentally, which show a good agreement. Such devices are tested for surface-enhanced Raman scattering (SERS) using the aqueous solution of rhodamine 6G under a Raman spectroscopy. The experimental results demonstrate that the SERS signal is enhanced benefiting from focal ability of FZP, which is a promising method for the particular biochemical spectra sensing applications.

  6. Characterization of redox conditions in groundwater contaminant plumes

    NASA Astrophysics Data System (ADS)

    Christensen, Thomas H.; Bjerg, Poul L.; Banwart, Steven A.; Jakobsen, Rasmus; Heron, Gorm; Albrechtsen, Hans-Jørgen

    2000-10-01

    Evaluation of redox conditions in groundwater pollution plumes is often a prerequisite for understanding the behaviour of the pollutants in the plume and for selecting remediation approaches. Measuring of redox conditions in pollution plumes is, however, a fairly recent issue and yet relative few cases have been reported. No standardised or generally accepted approach exists. Slow electrode kinetics and the common lack of internal equilibrium of redox processes in pollution plumes make, with a few exceptions, direct electrochemical measurement and rigorous interpretation of redox potentials dubious, if not erroneous. Several other approaches have been used in addressing redox conditions in pollution plumes: redox-sensitive compounds in groundwater samples, hydrogen concentrations in groundwater, concentrations of volatile fatty acids in groundwater, sediment characteristics and microbial tools, such as MPN counts, PLFA biomarkers and redox bioassays. This paper reviews the principles behind the different approaches, summarizes methods used and evaluates the approaches based on the experience from the reported applications.

  7. Numerical Simulations Of The Impact Of Comet Shoemaker-Levy 9: Plume Development

    NASA Astrophysics Data System (ADS)

    Palotai, Csaba J.; Korycansky, D.; Deming, D.; Harrington, J.; Reese, C.

    2007-10-01

    We present results of our three-dimensional, hydrodynamic simulations of the impact of comet Shoemaker-Levy 9 (SL9) into the atmosphere of Jupiter. In the current phase of the research we focus on the plume blowout and splashback phases of the SL9 event. We have modified the Zeus-MP/2 model (Hayes et al. 2006) to be suitable for our investigation, adding a Jovian atmospheric profile, Tillotson equation of state for the impactor, and the Coriolis terms. As an initial condition of our high-resolution simulations we use the energy deposition profile taken from the SL9 impact modeling of Korycansky et al. (2006). The effects of the Coriolis force during the shockwave propagation are tested through sensitivity tests. The viscosity in the splash model is adjusted until the outer part of the plume re-entry shock matches the expanding infrared rings (McGregor et al. 1996). The molecular viscosity being well-known, this will place a strong constraint on the Jovian eddy viscosity. We add radiative terms from previous 2D splash calculation of Deming and Harrington (2001) to allow us to calculate realistic wavelength-dependent lightcurves and low-resolution spectra for direct comparison to data. This work is supported by National Science Foundation Grant No. 0307638 and National Aeronautics and Space Administration Grant No. NNG 04GQ35G.

  8. Smoke Plume Over Eastern Canada

    NASA Technical Reports Server (NTRS)

    2007-01-01

    In late May, a massive smoke plume hundreds of kilometers across blew eastward over New Brunswick toward the Atlantic Ocean. On May 26, 2007, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured this image at 11:40 a.m. local time. By the time MODIS took this picture, the smoke appeared to have completely detached itself from the source, a large fire burning in southwestern Quebec, beyond the western edge of this image. In this image, the smoke appears as a gray-beige opaque mass with fuzzy, translucent edges. The plume is thickest in the southwest and diminishes toward the northeast. Just southwest of the plume is a red outline indicating a hotspot an area where MODIS detected anomalously warm surface temperatures, such as those resulting from fires. This hotspot, however, is not the source for this smoke plume. According to a bulletin from the National Oceanic and Atmospheric Administration, the southwestern Quebec fire was the source. According to reports from the Canadian Interagency Forest Fire Centre on May 29, that fire was estimated at 63,211 hectares (156,197 acres), and it was classified as 'being held.' At the same time, more than 20 wildfires burned in Quebec, news sources reported, and firefighters from other Canadian provinces and the United States had been brought in to provide reinforcements for the area's firefighters.

  9. Primary hydrothermal input above nonbuoyant plume level in the water column.

    NASA Astrophysics Data System (ADS)

    Nakamura, K.

    2008-12-01

    Accumulating in-situ Eh measurements of seawater by CTD hydrothermal plume chasing above ridges in various oceans suggest that some ill-diluted reduced water can be eventually observed above nonbuoyant plume level, which indicate locations of buoyant rising plume penetration through spread nonbuoyant plume. Such location can even be intentionally detectable by successive three to four orthogonal CTD tow-yo operations. See an example in the South Atlantic (http://www.divediscover.whoi.edu/expedition12/daily/080109.html). Large/rapid voltage drops recorded by in- situ Eh (ORP) electrodes on moving platform like CTD (non-equilibrated measurement) occur when electrodes pass from oxygen-controlled to sulfide-controlled redox condition. Assuming a common chemical compositions of 350 deg C hydrothermal fluid source, the calculated redox potential of mixture of hydrothermal fluid and ambient seawater shows a sharp discontinuity around the dilution factor of 130 (aquatic chemistry textbooks of Morel(1983) p.345, (1993) p.460). In popular turbulent plume models based on Morton, Taylor and Turner (1956, point source and homogeneous dilution by ambient seawater entrainment along by an amount proportional to the vertical velocity in the plume), the dilution factors at the level of zero rising momentum are calculated as 5500 to 10,000 (ex., McDuff, 1995). Evidence of redox anomalies above nonbuoyant plume level contradicts momentum overshoot by popular turbulent plume models and prefers a plume cap overshoot in starting plume (Turner, 1973) or heterogeneous dilution. Turner's starting plume were thought to be generated by on and off of buoyant fluid input. The plume cap is assumed to have vortex structure like thermal and resistant to dilution. In the ridge environment with ocean tide it is likely generated spatially and temporary by semidiurnal to diurnal bottom current direction change. Some recent AUV profiles cross-cutting rising buoyant plume will be also presented to

  10. Constraints on the detection of cryovolcanic plumes on Europa

    NASA Astrophysics Data System (ADS)

    Quick, Lynnae C.; Barnouin, Olivier S.; Prockter, Louise M.; Patterson, G. Wesley

    2013-09-01

    Surface venting is a common occurrence on several outer solar system satellites. Spacecraft have observed plumes erupting from the geologically young surfaces of Io, Triton and Enceladus. Europa also has a relatively young surface and previous studies have suggested that cryovolcanic eruptions may be responsible for the production of low-albedo deposits surrounding lenticulae and along triple band margins and lineae. Here, we have used the projected thicknesses of these deposits as constraints to determine the lifetimes of detectable cryovolcanic plumes that may have emplaced them. In an effort to explore the feasibility of detection of the particle component of plumes by spacecraft cameras operating at visible wavelengths, we present a conservative model to estimate plume characteristics such as height, eruption velocity, and optical depth under a variety of conditions. We find that cryovolcanic plumes on Europa are likely to be fairly small in stature with heights between 2.5 and 26 km, and eruption velocities between 81 and 261 m/s, respectively. Under these conditions and assuming that plumes are products of steady eruptions with particle radii of 0.5 μm, our model suggests that easily detectable plumes will have optical depths, τ, greater than or equal to 0.04, and that their lifetimes may be no more than 300,000 years. Plume detection may be possible if high phase angle limb observations and/or stereo imaging of the surface are undertaken in areas where eruptive activity is likely to occur. Cameras with imaging resolutions greater than 50 m/pixel should be used to make all observations. Future missions could employ the results of our model in searches for plume activity at Europa.

  11. Secondary organic aerosol formation in biomass-burning plumes: theoretical analysis of lab studies and ambient plumes

    NASA Astrophysics Data System (ADS)

    Bian, Qijing; Jathar, Shantanu H.; Kodros, John K.; Barsanti, Kelley C.; Hatch, Lindsay E.; May, Andrew A.; Kreidenweis, Sonia M.; Pierce, Jeffrey R.

    2017-04-01

    Secondary organic aerosol (SOA) has been shown to form in biomass-burning emissions in laboratory and field studies. However, there is significant variability among studies in mass enhancement, which could be due to differences in fuels, fire conditions, dilution, and/or limitations of laboratory experiments and observations. This study focuses on understanding processes affecting biomass-burning SOA formation in laboratory smog-chamber experiments and in ambient plumes. Vapor wall losses have been demonstrated to be an important factor that can suppress SOA formation in laboratory studies of traditional SOA precursors; however, impacts of vapor wall losses on biomass-burning SOA have not yet been investigated. We use an aerosol-microphysical model that includes representations of volatility and oxidation chemistry to estimate the influence of vapor wall loss on SOA formation observed in the FLAME III smog-chamber studies. Our simulations with base-case assumptions for chemistry and wall loss predict a mean OA mass enhancement (the ratio of final to initial OA mass, corrected for particle-phase wall losses) of 1.8 across all experiments when vapor wall losses are modeled, roughly matching the mean observed enhancement during FLAME III. The mean OA enhancement increases to over 3 when vapor wall losses are turned off, implying that vapor wall losses reduce the apparent SOA formation. We find that this decrease in the apparent SOA formation due to vapor wall losses is robust across the ranges of uncertainties in the key model assumptions for wall-loss and mass-transfer coefficients and chemical mechanisms.We then apply similar assumptions regarding SOA formation chemistry and physics to smoke emitted into the atmosphere. In ambient plumes, the plume dilution rate impacts the organic partitioning between the gas and particle phases, which may impact the potential for SOA to form as well as the rate of SOA formation. We add Gaussian dispersion to our aerosol

  12. Secondary organic aerosol formation in biomass-burning plumes: theoretical analysis of lab studies and ambient plumes

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

    Bian, Qijing; Jathar, Shantanu H.; Kodros, John K.

    Secondary organic aerosol (SOA) has been shown to form in biomass-burning emissions in laboratory and field studies. However, there is significant variability among studies in mass enhancement, which could be due to differences in fuels, fire conditions, dilution, and/or limitations of laboratory experiments and observations. This study focuses on understanding processes affecting biomass-burning SOA formation in laboratory smog-chamber experiments and in ambient plumes. Vapor wall losses have been demonstrated to be an important factor that can suppress SOA formation in laboratory studies of traditional SOA precursors; however, impacts of vapor wall losses on biomass-burning SOA have not yet been investigated.more » We use an aerosol-microphysical model that includes representations of volatility and oxidation chemistry to estimate the influence of vapor wall loss on SOA formation observed in the FLAME III smog-chamber studies. Our simulations with base-case assumptions for chemistry and wall loss predict a mean OA mass enhancement (the ratio of final to initial OA mass, corrected for particle-phase wall losses) of 1.8 across all experiments when vapor wall losses are modeled, roughly matching the mean observed enhancement during FLAME III. The mean OA enhancement increases to over 3 when vapor wall losses are turned off, implying that vapor wall losses reduce the apparent SOA formation. We find that this decrease in the apparent SOA formation due to vapor wall losses is robust across the ranges of uncertainties in the key model assumptions for wall-loss and mass-transfer coefficients and chemical mechanisms. We then apply similar assumptions regarding SOA formation chemistry and physics to smoke emitted into the atmosphere. In ambient plumes, the plume dilution rate impacts the organic partitioning between the gas and particle phases, which may impact the potential for SOA to form as well as the rate of SOA formation. We add Gaussian dispersion to our aerosol

  13. Secondary organic aerosol formation in biomass-burning plumes: theoretical analysis of lab studies and ambient plumes

    DOE PAGES

    Bian, Qijing; Jathar, Shantanu H.; Kodros, John K.; ...

    2017-04-28

    Secondary organic aerosol (SOA) has been shown to form in biomass-burning emissions in laboratory and field studies. However, there is significant variability among studies in mass enhancement, which could be due to differences in fuels, fire conditions, dilution, and/or limitations of laboratory experiments and observations. This study focuses on understanding processes affecting biomass-burning SOA formation in laboratory smog-chamber experiments and in ambient plumes. Vapor wall losses have been demonstrated to be an important factor that can suppress SOA formation in laboratory studies of traditional SOA precursors; however, impacts of vapor wall losses on biomass-burning SOA have not yet been investigated.more » We use an aerosol-microphysical model that includes representations of volatility and oxidation chemistry to estimate the influence of vapor wall loss on SOA formation observed in the FLAME III smog-chamber studies. Our simulations with base-case assumptions for chemistry and wall loss predict a mean OA mass enhancement (the ratio of final to initial OA mass, corrected for particle-phase wall losses) of 1.8 across all experiments when vapor wall losses are modeled, roughly matching the mean observed enhancement during FLAME III. The mean OA enhancement increases to over 3 when vapor wall losses are turned off, implying that vapor wall losses reduce the apparent SOA formation. We find that this decrease in the apparent SOA formation due to vapor wall losses is robust across the ranges of uncertainties in the key model assumptions for wall-loss and mass-transfer coefficients and chemical mechanisms. We then apply similar assumptions regarding SOA formation chemistry and physics to smoke emitted into the atmosphere. In ambient plumes, the plume dilution rate impacts the organic partitioning between the gas and particle phases, which may impact the potential for SOA to form as well as the rate of SOA formation. We add Gaussian dispersion to our aerosol

  14. Volcanic Plume Measurements with UAV (Invited)

    NASA Astrophysics Data System (ADS)

    Shinohara, H.; Kaneko, T.; Ohminato, T.

    2013-12-01

    Volatiles in magmas are the driving force of volcanic eruptions and quantification of volcanic gas flux and composition is important for the volcano monitoring. Recently we developed a portable gas sensor system (Multi-GAS) to quantify the volcanic gas composition by measuring volcanic plumes and obtained volcanic gas compositions of actively degassing volcanoes. As the Multi-GAS measures variation of volcanic gas component concentrations in the pumped air (volcanic plume), we need to bring the apparatus into the volcanic plume. Commonly the observer brings the apparatus to the summit crater by himself but such measurements are not possible under conditions of high risk of volcanic eruption or difficulty to approach the summit due to topography etc. In order to overcome these difficulties, volcanic plume measurements were performed by using manned and unmanned aerial vehicles. The volcanic plume measurements by manned aerial vehicles, however, are also not possible under high risk of eruption. The strict regulation against the modification of the aircraft, such as installing sampling pipes, also causes difficulty due to the high cost. Application of the UAVs for the volcanic plume measurements has a big advantage to avoid these problems. The Multi-GAS consists of IR-CO2 and H2O gas analyzer, SO2-H2O chemical sensors and H2 semiconductor sensor and the total weight ranges 3-6 kg including batteries. The necessary conditions of the UAV for the volcanic plumes measurements with the Multi-GAS are the payloads larger than 3 kg, maximum altitude larger than the plume height and installation of the sampling pipe without contamination of the exhaust gases, as the exhaust gases contain high concentrations of H2, SO2 and CO2. Up to now, three different types of UAVs were applied for the measurements; Kite-plane (Sky Remote) at Miyakejima operated by JMA, Unmanned airplane (Air Photo Service) at Shinomoedake, Kirishima volcano, and Unmanned helicopter (Yamaha) at Sakurajima

  15. CONSEQUENCES OF NON-LINEAR DENSITY EFFECTS ON BUOYANCY AND PLUME BEHAVIOR

    EPA Science Inventory

    Aquatic plumes, as turbulent streams, grow by entraining ambient water. Buoyant plumes rise and dense ones sink, but, non-linear kinetic effects can reverse the buoyant force in mid-phenomenon. The class of nascent-density plumes begin as buoyant, upwardly accelerating plumes tha...

  16. Influence of mass transfer on bubble plume hydrodynamics.

    PubMed

    Lima Neto, Iran E; Parente, Priscila A B

    2016-03-01

    This paper presents an integral model to evaluate the impact of gas transfer on the hydrodynamics of bubble plumes. The model is based on the Gaussian type self-similarity and functional relationships for the entrainment coefficient and factor of momentum amplification due to turbulence. The impact of mass transfer on bubble plume hydrodynamics is investigated considering different bubble sizes, gas flow rates and water depths. The results revealed a relevant impact when fine bubbles are considered, even for moderate water depths. Additionally, model simulations indicate that for weak bubble plumes (i.e., with relatively low flow rates and large depths and slip velocities), both dissolution and turbulence can affect plume hydrodynamics, which demonstrates the importance of taking the momentum amplification factor relationship into account. For deeper water conditions, simulations of bubble dissolution/decompression using the present model and classical models available in the literature resulted in a very good agreement for both aeration and oxygenation processes. Sensitivity analysis showed that the water depth, followed by the bubble size and the flow rate are the most important parameters that affect plume hydrodynamics. Lastly, dimensionless correlations are proposed to assess the impact of mass transfer on plume hydrodynamics, including both the aeration and oxygenation modes.

  17. Laser tailored nanoparticle arrays to detect molecules at dilute concentration

    NASA Astrophysics Data System (ADS)

    Zanchi, Chiara; Lucotti, Andrea; Tommasini, Matteo; Trusso, Sebastiano; de Grazia, Ugo; Ciusani, Emilio; Ossi, Paolo M.

    2017-02-01

    By nanosecond pulsed laser ablation in an ambient gas gold nanoparticles (NPs) were produced that self-assemble on a substrate resulting in increasingly elaborated architectures of growing thickness, from isolated NP arrays up to percolated films. NPs nucleate and grow in the plasma plume propagating through the gas. Process parameters including laser wavelength, laser energy density, target to substrate distance, nature and pressure of the gas affect plasma expansion, thus asymptotic NP size and kinetic energy. NP size, energy and mobility at landing determine film growth and morphology that affect the physico-chemical properties of the film. Keeping fixed the other process parameters, we discuss the sensitive dependence of film surface nanostructure on Ar pressure and on laser pulse number. The initial plume velocity and average ablated mass per pulse allow predicting the asymptotic NP size. The control of growth parameters favors fine-tuning of NP aggregation, relevant to plasmonics to get optimized substrates for surface enhanced Raman spectroscopy (SERS). Their behavior is discussed for testing conditions of interest for clinical application. Both in aqueous and in biological solutions we obtained good sensitivity and reproducibility of the SERS signals for the anti-Parkinson drug apomorphine, and for the anti-epilepsy drug carbamazepine.

  18. Advanced Ablative TPS

    NASA Technical Reports Server (NTRS)

    Gasch, Matthew J.

    2011-01-01

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

  19. Is Cryoballoon Ablation Preferable to Radiofrequency Ablation for Treatment of Atrial Fibrillation by Pulmonary Vein Isolation? A Meta-Analysis

    PubMed Central

    Xu, Junxia; Huang, Yingqun; Cai, Hongbin; Qi, Yue; Jia, Nan; Shen, Weifeng; Lin, Jinxiu; Peng, Feng; Niu, Wenquan

    2014-01-01

    Objective Currently radiofrequency and cryoballoon ablations are the two standard ablation systems used for catheter ablation of atrial fibrillation; however, there is no universal consensus on which ablation is the optimal choice. We therefore sought to undertake a meta-analysis with special emphases on comparing the efficacy and safety between cryoballoon and radiofrequency ablations by synthesizing published clinical trials. Methods and Results Articles were identified by searching the MEDLINE and EMBASE databases before September 2013, by reviewing the bibliographies of eligible reports, and by consulting with experts in this field. Data were extracted independently and in duplicate. There were respectively 469 and 635 patients referred for cryoballoon and radiofrequency ablations from 14 qualified clinical trials. Overall analyses indicated that cryoballoon ablation significantly reduced fluoroscopic time and total procedure time by a weighted mean of 14.13 (95% confidence interval [95% CI]: 2.82 to 25.45; P = 0.014) minutes and 29.65 (95% CI: 8.54 to 50.77; P = 0.006) minutes compared with radiofrequency ablation, respectively, whereas ablation time in cryoballoon ablation was nonsignificantly elongated by a weighted mean of 11.66 (95% CI: −10.71 to 34.04; P = 0.307) minutes. Patients referred for cryoballoon ablation had a high yet nonsignificant success rate of catheter ablation compared with cryoballoon ablation (odds ratio; 95% CI; P: 1.34; 0.53 to 3.36; 0.538), and cryoballoon ablation was also found to be associated with the relatively low risk of having recurrent atrial fibrillation (0.75; 0.3 to 1.88; 0.538) and major complications (0.46; 0.11 to 1.83; 0.269). There was strong evidence of heterogeneity and low probability of publication bias. Conclusion Our findings demonstrate greater improvement in fluoroscopic time and total procedure duration for atrial fibrillation patients referred for cryoballoon ablation than those for

  20. Radiofrequency ablation during continuous saline infusion can extend ablation margins

    PubMed Central

    Ishikawa, Toru; Kubota, Tomoyuki; Horigome, Ryoko; Kimura, Naruhiro; Honda, Hiroki; Iwanaga, Akito; Seki, Keiichi; Honma, Terasu; Yoshida, Toshiaki

    2013-01-01

    AIM: To determine whether fluid injection during radiofrequency ablation (RFA) can increase the coagulation area. METHODS: Bovine liver (1-2 kg) was placed on an aluminum tray with a return electrode affixed to the base, and the liver was punctured by an expandable electrode. During RFA, 5% glucose; 50% glucose; or saline fluid was infused continuously at a rate of 1.0 mL/min through the infusion line connected to the infusion port. The area and volume of the thermocoagulated region of bovine liver were determined after RFA. The Joule heat generated was determined from the temporal change in output during the RFA experiment. RESULTS: No liquid infusion was 17.3 ± 1.6 mL, similar to the volume of a 3-cm diameter sphere (14.1 mL). Mean thermocoagulated volume was significantly larger with continuous infusion of saline (29.3 ± 3.3 mL) than with 5% glucose (21.4 ± 2.2 mL), 50% glucose (16.5 ± 0.9 mL) or no liquid infusion (17.3 ± 1.6 mL). The ablated volume for RFA with saline was approximately 1.7-times greater than for RFA with no liquid infusion, representing a significant difference between these two conditions. Total Joule heat generated during RFA was highest with saline, and lowest with 50% glucose. CONCLUSION: RFA with continuous saline infusion achieves a large ablation zone, and may help inhibit local recurrence by obtaining sufficient ablation margins. RFA during continuous saline infusion can extend ablation margins, and may be prevent local recurrence. PMID:23483097

  1. Linking Europa's plume activity to tides, tectonics, and liquid water

    NASA Astrophysics Data System (ADS)

    Rhoden, Alyssa Rose; Hurford, Terry A.; Roth, Lorenz; Retherford, Kurt

    2015-06-01

    Much of the geologic activity preserved on Europa's icy surface has been attributed to tidal deformation, mainly due to Europa's eccentric orbit. Although the surface is geologically young (30-80 Myr), there is little information as to whether tidally-driven surface processes are ongoing. However, a recent detection of water vapor near Europa's south pole suggests that it may be geologically active. Initial observations indicated that Europa's plume eruptions are time-variable and may be linked to its tidal cycle. Saturn's moon, Enceladus, which shares many similar traits with Europa, displays tidally-modulated plume eruptions, which bolstered this interpretation. However, additional observations of Europa at the same time in its orbit failed to yield a plume detection, casting doubt on the tidal control hypothesis. The purpose of this study is to analyze the timing of plume eruptions within the context of Europa's tidal cycle to determine whether such a link exists and examine the inferred similarities and differences between plume activity on Europa and Enceladus. To do this, we determine the locations and orientations of hypothetical tidally-driven fractures that best match the temporal variability of the plumes observed at Europa. Specifically, we identify model faults that are in tension at the time in Europa's orbit when a plume was detected and in compression at times when the plume was not detected. We find that tidal stress driven solely by eccentricity is incompatible with the observations unless additional mechanisms are controlling the eruption timing or restricting the longevity of the plumes. The addition of obliquity tides, and corresponding precession of the spin pole, can generate a number of model faults that are consistent with the pattern of plume detections. The locations and orientations of these hypothetical source fractures are robust across a broad range of precession rates and spin pole directions. Analysis of the stress variations across

  2. UV missile-plume signature model

    NASA Astrophysics Data System (ADS)

    Roblin, Antoine; Baudoux, Pierre E.; Chervet, Patrick

    2002-08-01

    A new 3D radiative code is used to solve the radiative transfer equation in the UV spectral domain for a nonequilibrium and axisymmetric media such as a rocket plume composed of hot reactive gases and metallic oxide particles like alumina. Calculations take into account the dominant chemiluminescence radiation mechanism and multiple scattering effects produced by alumina particles. Plume radiative properties are studied by using a simple cylindrical media of finite length, deduced from different aerothermochemical real rocket plume afterburning zones. Assumed a log-normal size distribution of alumina particles, optical properties are calculated by using Mie theory. Due to large uncertainties of particles properties, systematic tests have been performed in order to evaluate the influence of the different input data (refractive index, particle mean geometric radius) upon the radiance field. These computations will help us to define the set of parameters which need to be known accurately in order to compare computations with radiance measurements obtained during field experiments.

  3. Ash Plume from Shiveluch

    NASA Image and Video Library

    2012-10-09

    When NASA’s Terra satellite passed over Russia’s Kamchatka Peninsula at noon local time (00:00 Universal Time) on October 6, 2012, Shilveluch Volcano was quiet. By the time NASA’s Aqua satellite passed over the area two hours later (bottom image), the volcano had erupted and sent a plume of ash over the Kamchatskiy Zaliv. The plume traveled about 90 kilometers (55 miles) toward the south-southeast, where a change in wind direction began pushing the plume toward the east. On October 6, 2012, the Kamchatka Volcanic Emergency Response Team (KVERT) reported that the ash plume from Shiveluch reached an altitude of 3 kilometers (9,800 feet) above sea level, and had traveled some 220 kilometers (140 miles) from the volcano summit. Shiveluch (also spelled Sheveluch) ranks among the biggest and most active volcanoes on the Kamchatka Peninsula. Rising to 3,283 meters (10,771 feet) above sea level, Shiveluch is a stratovolcano composed of alternating layers of hardened lava, compacted ash, and rocks ejected by previous eruptions. The beige-colored expanse of rock on the volcano’s southern slopes (visible in both images) is due to an explosive eruption that occurred in 1964. Part of Shiveluch’s southern flank collapsed, and the light-colored rock is avalanche debris left by that event. High-resolution imagery of Shiveluch shows very little vegetation within that avalanche zone. On October 6, 2012, KVERT cited observations from the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on Terra and Aqua in detecting the Shiveluch eruption. This was not the first time that MODIS observed a Shiveluch eruption shortly after it started. In 2007, MODIS captured an image within minutes of the eruption’s start, before winds could blow the ash away from the summit. When NASA’s Terra satellite passed over Russia’s Kamchatka Peninsula at noon local time (00:00 Universal Time) on October 6, 2012, Shilveluch Volcano was quiet (top image). By the time NASA

  4. Treatment of Recurrent Nonparoxysmal Atrial Fibrillation Using Focal Impulse and Rotor Mapping (FIRM)-Guided Rotor Ablation: Early Recurrence and Long-Term Outcomes.

    PubMed

    Spitzer, Stefan Georg; Károlyi, László; Rämmler, Carola; Scharfe, Frank; Weinmann, Thomas; Zieschank, Mirko; Langbein, Anke

    2017-01-01

    A patient-tailored ablation approach focused on the elimination of both pulmonary vein triggers as well as substrate drivers may result in favorable outcomes in recurrent persistent AF patients. We evaluated the long-term outcomes of rotor ablation combined with conventional pulmonary vein isolation (PVI) in patients with recurrent nonparoxysmal AF. Fifty-eight consecutive patients underwent FIRM-guided rotor ablation followed by conventional PVI for the treatment of recurrent nonparoxysmal AF. A software algorithm was used to display rotational activity at rotor sites by creating propagation maps from unipolar electrograms recorded using a 64-electrode basket catheter. These rotor sites were targeted for ablation, followed by conventional PVI. All patients had nonparoxysmal AF (83% longstanding persistent) and a previously failed conventional ablation procedure. Stable rotors were identified in all patients (mean of 3.0 ± 1.6 per patient), with 55.2% having right atrial rotors and 96.6% left atrial rotors, respectively. Complications occurred in 5.2% of patients, none related to the FIRM procedure. The median follow-up was 12 months. At 6 and 12 months of follow-up, 73.2% and 76.9% of patients remained free from AF/AT, respectively. Excluding 2 patients who underwent a successful redo ablation procedure/electrical cardioversion, at 12 months of follow-up, 69.2% were free from any AF/AT and 73.1% were free from AF after a single FIRM-guided ablation procedure. A high degree of success was observed in this cohort of primarily longstanding persistent AF patients treated for recurrent AF with FIRM-guided rotor ablation. Prospective randomized controlled trials are needed. © 2016 Wiley Periodicals, Inc.

  5. Influence of ablation wavelength and time on optical properties of laser ablated carbon dots

    NASA Astrophysics Data System (ADS)

    Isnaeni, Hanna, M. Yusrul; Pambudi, A. A.; Murdaka, F. H.

    2017-01-01

    Carbon dots, which are unique and applicable materials, have been produced using many techniques. In this work, we have fabricated carbon dots made of coconut fiber using laser ablation technique. The purpose of this work is to evaluate two ablation parameters, which are ablation wavelength and ablation time. We used pulsed laser from Nd:YAG laser with emit wavelength at 355 nm, 532 nm and 1064 nm. We varied ablation time one hour and two hours. Photoluminescence and time-resolved photoluminescence setup were used to study the optical properties of fabricated carbon dots. In general, fabricated carbon dots emit bluish green color emission upon excitation by blue laser. We found that carbon dots fabricated using 1064 nm laser produced the highest carbon dots emission among other samples. The peak wavelength of carbon dots emission is between 495 nm until 505 nm, which gives bluish green color emission. Two hours fabricated carbon dots gave four times higher emission than one hour fabricated carbon dot. More emission intensity of carbon dots means more carbon dots nanoparticles were fabricated during laser ablation process. In addition, we also measured electron dynamics of carbon dots using time-resolved photoluminescence. We found that sample with higher emission has longer electron decay time. Our finding gives optimum condition of carbon dots fabrication from coconut fiber using laser ablation technique. Moreover, fabricated carbon dots are non-toxic nanoparticles that can be applied for health, bio-tagging and medical applications.

  6. Numerical Simulation of Laser Ablative Shock Waves From Aluminum in Presence of Helium Gas At Different Ambient Pressures

    NASA Astrophysics Data System (ADS)

    Paturi, Prem Kiran; Durvasula, P. S. L. Kameswari; S, Sai Shiva; Acrhem, University Of Hyderabad Team

    2017-06-01

    A two dimensional comparative study of Laser Ablative Shock Wave into the Aluminum target in the presence of Helium gas at different ambient pressures over a range of 690 - 105 Pa performed using FLASH hydrodynamic codes will be presented. The irradiation of Aluminum target (thickness 2 mm and radius 3 mm) with a 7 ns laser pulse of energy 175 mJ, spot size of 150 µm on the target surface at a wavelength of 532 nm at normal incidence is simulated. Helium gas enclosed in a chamber of height 3 mm and width 3 mm. The electron-ion inverse bremsstrahlung absorption coefficient is considered in the laser energy deposition process. The simulation was performed over a duration of 1 μs. It was observed that an ablative shock is launched into the Helium gas for the pressures of 0.5 atm and above. However, for pressure less than the 0.5 atm the plasma expanded into the He gas upto 12ns and after which due to pressure equilibration with the surroundings and plume splitting shock wave is launched in to Al. Authors acknowledge funding from DRDO, India.

  7. Stormwater plume detection by MODIS imagery in the southern California coastal ocean

    NASA Astrophysics Data System (ADS)

    Nezlin, Nikolay P.; DiGiacomo, Paul M.; Diehl, Dario W.; Jones, Burton H.; Johnson, Scott C.; Mengel, Michael J.; Reifel, Kristen M.; Warrick, Jonathan A.; Wang, Menghua

    2008-10-01

    Stormwater plumes in the southern California coastal ocean were detected by MODIS-Aqua satellite imagery and compared to ship-based data on surface salinity and fecal indicator bacterial (FIB) counts collected during the Bight'03 Regional Water Quality Program surveys in February-March of 2004 and 2005. MODIS imagery was processed using a combined near-infrared/shortwave-infrared (NIR-SWIR) atmospheric correction method, which substantially improved normalized water-leaving radiation (nLw) optical spectra in coastal waters with high turbidity. Plumes were detected using a minimum-distance supervised classification method based on nLw spectra averaged within the training areas, defined as circular zones of 1.5-5.0-km radii around field stations with a surface salinity of S < 32.0 ("plume") and S > 33.0 ("ocean"). The plume optical signatures (i.e., the nLw differences between "plume" and "ocean") were most evident during the first 2 days after the rainstorms. To assess the accuracy of plume detection, stations were classified into "plume" and "ocean" using two criteria: (1) "plume" included the stations with salinity below a certain threshold estimated from the maximum accuracy of plume detection; and (2) FIB counts in "plume" exceeded the California State Water Board standards. The salinity threshold between "plume" and "ocean" was estimated as 32.2. The total accuracy of plume detection in terms of surface salinity was not high (68% on average), seemingly because of imperfect correlation between plume salinity and ocean color. The accuracy of plume detection in terms of FIB exceedances was even lower (64% on average), resulting from low correlation between ocean color and bacterial contamination. Nevertheless, satellite imagery was shown to be a useful tool for the estimation of the extent of potentially polluted plumes, which was hardly achievable by direct sampling methods (in particular, because the grids of ship-based stations covered only small parts of the

  8. Direct observation of impact propagation and absorption in dense colloidal monolayers

    PubMed Central

    Cha, Jinwoong; Lin, Wei-Hsun; Job, Stéphane; Daraio, Chiara

    2017-01-01

    Dense colloidal suspensions can propagate and absorb large mechanical stresses, including impacts and shocks. The wave transport stems from the delicate interplay between the spatial arrangement of the structural units and solvent-mediated effects. For dynamic microscopic systems, elastic deformations of the colloids are usually disregarded due to the damping imposed by the surrounding fluid. Here, we study the propagation of localized mechanical pulses in aqueous monolayers of micron-sized particles of controlled microstructure. We generate extreme localized deformation rates by exciting a target particle via pulsed-laser ablation. In crystalline monolayers, stress propagation fronts take place, where fast-moving particles (V approximately a few meters per second) are aligned along the symmetry axes of the lattice. Conversely, more viscous solvents and disordered structures lead to faster and isotropic energy absorption. Our results demonstrate the accessibility of a regime where elastic collisions also become relevant for suspensions of microscopic particles, behaving as “billiard balls” in a liquid, in analogy with regular packings of macroscopic spheres. We furthermore quantify the scattering of an impact as a function of the local structural disorder. PMID:29087329

  9. Eiffel Tower Plume

    NASA Image and Video Library

    2015-08-31

    A single plume of plasma, many times taller than the diameter of Earth, rose up from the Sun, twisted and spun around, all the while spewing streams of particles for over two days (Aug. 17-19, 2015) before breaking apart. At times, its shape resembled the Eiffel Tower. Other lesser plumes and streams of particles can be seen dancing above the solar surface as well. The action was observed in a wavelength of extreme ultraviolet light. Credit: NASA/Goddard/SDO NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

  10. Brain Emboli After Left Ventricular Endocardial Ablation.

    PubMed

    Whitman, Isaac R; Gladstone, Rachel A; Badhwar, Nitish; Hsia, Henry H; Lee, Byron K; Josephson, S Andrew; Meisel, Karl M; Dillon, William P; Hess, Christopher P; Gerstenfeld, Edward P; Marcus, Gregory M

    2017-02-28

    Catheter ablation for ventricular tachycardia and premature ventricular complexes (PVCs) is common. Catheter ablation of atrial fibrillation is associated with a risk of cerebral emboli attributed to cardioversions and numerous ablation lesions in the low-flow left atrium, but cerebral embolic risk in ventricular ablation has not been evaluated. We enrolled 18 consecutive patients meeting study criteria scheduled for ventricular tachycardia or PVC ablation over a 9-month period. Patients undergoing left ventricular (LV) ablation were compared with a control group of those undergoing right ventricular ablation only. Patients were excluded if they had implantable cardioverter defibrillators or permanent pacemakers. Radiofrequency energy was used for ablation in all cases and heparin was administered with goal-activated clotting times of 300 to 400 seconds for all LV procedures. Pre- and postprocedural brain MRI was performed on each patient within a week of the ablation procedure. Embolic infarcts were defined as new foci of reduced diffusion and high signal intensity on fluid-attenuated inversion recovery brain MRI within a vascular distribution. The mean age was 58 years, half of the patients were men, half had a history of hypertension, and the majority had no known vascular disease or heart failure. LV ablation was performed in 12 patients (ventricular tachycardia, n=2; PVC, n=10) and right ventricular ablation was performed exclusively in 6 patients (ventricular tachycardia, n=1; PVC, n=5). Seven patients (58%) undergoing LV ablation experienced a total of 16 cerebral emboli, in comparison with zero patients undergoing right ventricular ablation ( P =0.04). Seven of 11 patients (63%) undergoing a retrograde approach to the LV developed at least 1 new brain lesion. More than half of patients undergoing routine LV ablation procedures (predominately PVC ablations) experienced new brain emboli after the procedure. Future research is critical to understanding the

  11. Experiments on Plume Spreading by Engineered Injection and Extraction

    NASA Astrophysics Data System (ADS)

    Mays, D. C.; Jones, M.; Tigera, R. G.; Neupauer, R.

    2014-12-01

    The notion that groundwater remediation is transport-limited emphasizes the coupling between physical (i.e., hydrodynamic), geochemical, and microbiological processes in the subsurface. Here we leverage this coupling to promote groundwater remediation using the approach of engineered injection and extraction. In this approach, inspired by the literature on chaotic advection, uncontaminated groundwater is injected and extracted through a manifold of wells surrounding the contaminated plume. The potential of this approach lies in its ability to actively manipulate the velocity field near the contaminated plume, generating plume spreading above and beyond that resulting from aquifer heterogeneity. Plume spreading, in turn, promotes mixing and reaction by chemical and biological processes. Simulations have predicted that engineered injection and extraction generates (1) chaotic advection whose characteristics depend on aquifer heterogeneity, and (2) faster rates and increased extent of groundwater remediation. This presentation focuses on a complimentary effort to experimentally demonstrate these predictions experimentally. In preparation for future work using refractive index matched (RIM) porous media, the experiments reported here use a Hele-Shaw apparatus containing silicone oil. Engineered injection and extraction is used to manipulate the geometry of an initially circular plume of black pigment, and photographs record the plume geometry after each step of injection of extraction. Image analysis, using complimentary Eulerian and Lagrangian approaches, reveals the thickness and variability of the dispersion zone surrounding the deformed plume of black pigment. The size, shape, and evolution of this dispersion zone provides insight into the interplay between engineered injection and extraction, which generates plume structure, and dispersion (here Taylor dispersion), which destroys plume structure. These experiments lay the groundwork for application of engineered

  12. Quantification of Plume-Soil Interaction and Excavation Due to the Sky Crane Descent Stage

    NASA Technical Reports Server (NTRS)

    Vizcaino, Jeffrey; Mehta, Manish

    2015-01-01

    The quantification of the particulate erosion that occurs as a result of a rocket exhaust plume impinging on soil during extraterrestrial landings is critical for future robotic and human lander mission design. The aerodynamic environment that results from the reflected plumes results in dust lifting, site alteration and saltation, all of which create a potentially erosive and contaminant heavy environment for the lander vehicle and any surrounding structures. The Mars Science Lab (MSL), weighing nearly one metric ton, required higher levels of thrust from its retro propulsive systems and an entirely new descent system to minimize these effects. In this work we seek to quantify plume soil interaction and its resultant soil erosion caused by the MSL's Sky Crane descent stage engines by performing three dimensional digital terrain and elevation mapping of the Curiosity rover's landing site. Analysis of plume soil interaction altitude and time was performed by detailed examination of the Mars Descent Imager (MARDI) still frames and reconstructed inertial measurement unit (IMU) sensor data. Results show initial plume soil interaction from the Sky Crane's eight engines began at ground elevations greater than 60 meters and more than 25 seconds before the rovers' touchdown event. During this time, viscous shear erosion (VSE) was dominant typically resulting in dusting of the surface with flow propagating nearly parallel to the surface. As the vehicle descended and decreased to four powered engines plume-plume and plume soil interaction increased the overall erosion rate at the surface. Visibility was greatly reduced at a height of roughly 20 meters above the surface and fell to zero ground visibility shortly after. The deployment phase of the Sky Crane descent stage hovering at nearly six meters above the surface showed the greatest amount of erosion with several large particles of soil being kicked up, recirculated, and impacting the bottom of the rover chassis. Image

  13. Atmospheric Modeling of Mars Methane Plumes

    NASA Astrophysics Data System (ADS)

    Mischna, Michael A.; Allen, M.; Lee, S.

    2010-10-01

    We present two complementary methods for isolating and modeling surface source releases of methane in the martian atmosphere. From recent observations, there is strong evidence that periodic releases of methane occur from discrete surface locations, although the exact location and mechanism of release is still unknown. Numerical model simulations with the Mars Weather Research and Forecasting (MarsWRF) general circulation model (GCM) have been applied to the ground-based observations of atmospheric methane by Mumma et al., (2009). MarsWRF simulations reproduce the natural behavior of trace gas plumes in the martian atmosphere, and reveal the development of the plume over time. These results provide constraints on the timing and location of release of the methane plume. Additional detections of methane have been accumulated by the Planetary Fourier Spectrometer (PFS) on board Mars Express. For orbital observations, which generally have higher frequency and resolution, an alternate approach to source isolation has been developed. Drawing from the concept of natural selection within biology, we apply an evolutionary computational model to this problem of isolating source locations. Using genetic algorithms that `reward’ best-fit matches between observations and GCM plume simulations (also from MarsWRF) over many generations, we find that we can potentially isolate source locations to within tens of km, which is within the roving capabilities of future Mars rovers. Together, these methods present viable numerical approaches to restricting the timing, duration and size of methane release events, and can be used for other trace gas plumes on Mars as well as elsewhere in the solar system.

  14. Europa Scene: Plume, Galileo, Magnetic Field (Artist's Concept)

    NASA Image and Video Library

    2018-05-14

    Artist's illustration of Jupiter and Europa (in the foreground) with the Galileo spacecraft after its pass through a plume erupting from Europa's surface. A new computer simulation gives us an idea of how the magnetic field interacted with a plume. The magnetic field lines (depicted in blue) show how the plume interacts with the ambient flow of Jovian plasma. The red colors on the lines show more dense areas of plasma. https://photojournal.jpl.nasa.gov/catalog/PIA21922

  15. Role of transients in the sustainability of solar coronal plumes

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

    Raouafi, N.-E.; Stenborg, G., E-mail: NourEddine.Raouafi@jhuapl.edu

    2014-06-01

    We report on the role of small-scale, transient magnetic activity in the formation and evolution of solar coronal plumes. Three plumes within equatorial coronal holes are analyzed over the span of several days based on the Solar Dynamic Observatory (SDO)/Atmospheric Imaging Assembly 171 Å and 193 Å images and SDO/Helioseismic and Magnetic Imager line-of-sight magnetograms. The focus is on the role of transient structures at the footpoints in sustaining coronal plumes for relatively long periods of time (i.e., several days). The appearance of plumes is a gradual and lengthy process. In some cases, the initial stages of plume formation aremore » marked by the appearance of pillar-like structures whose footpoints are the sources of transient brightenings. In addition to nominal jets occurring prior to and during the development of plumes, the data show that a large number of small jets (i.e., {sup j}etlets{sup )} and plume transient bright points (PTBPs) occur on timescales of tens of seconds to a few minutes. These features are the result of quasi-random cancellations of fragmented and diffuse minority magnetic polarity with the dominant unipolar magnetic field concentration over an extended period of time. They unambiguously reflect a highly dynamical evolution at the footpoints and are seemingly the main energy source for plumes. This suggests a tendency for plumes to be dependent on the occurrence of transients (i.e., jetlets, and PTBPs) resulting from low-rate magnetic reconnection. The decay phase of plumes is characterized by gradual fainting and multiple rejuvenations as a result of the dispersal of the unipolar magnetic concentration and its precipitation into multiple magnetic centers.« less

  16. Cassini Radio Occultation by Enceladus Plume

    NASA Astrophysics Data System (ADS)

    Kliore, A.; Armstrong, J.; Flasar, F.; French, R.; Marouf, E.; Nagy, A.; Rappaport, N.; McGhee, C.; Schinder, P.; Anabtawi, A.; Asmar, S.; Barbinis, E.; Fleischman, D.; Goltz, G.; Aguilar, R.; Rochblatt, D.

    2006-12-01

    A fortuitous Cassini radio occultation by Enceladus plume occurs on September 15, 2006. The occultation track (the spacecraft trajectory in the plane of the sky as viewed from the Earth) has been designed to pass behind the plume (to pass above the south polar region of Enceladus) in a roughly symmetrical geometry centered on a minimum altitude above the surface of about 20 km. The minimum altitude was selected primarily to ensure probing much of the plume with good confidence given the uncertainty in the spacecraft trajectory. Three nearly-pure sinusoidal signals of 0.94, 3.6, and 13 cm-wavelength (Ka-, X-, and S-band, respectively) are simultaneously transmitted from Cassini and are monitored at two 34-m Earth receiving stations of the Deep Space Network (DSN) in Madrid, Spain (DSS-55 and DSS-65). The occultation of the visible plume is extremely fast, lasting less than about two minutes. The actual observation time extends over a much longer time interval, however, to provide a good reference baseline for potential detection of signal perturbations introduced by the tenuous neutral and ionized plume environment. Given the likely very small fraction of optical depth due to neutral particles of sizes larger than about 1 mm, detectable changes in signal intensity is perhaps unlikely. Detection of plume plasma along the radio path as perturbations in the signals frequency/phase is more likely and the magnitude will depend on the electron columnar density probed. The occultation time occurs not far from solar conjunction time (Sun-Earth-probe angle of about 33 degrees), causing phase scintillations due to the solar wind to be the primary limiting noise source. We estimate a delectability limit of about 1 to 3E16 electrons per square meter columnar density assuming about 100 seconds integration time. Potential measurement of the profile of electron columnar density along the occultation track is an exciting prospect at this time.

  17. Plasma plume effects on the conductivity of amorphous-LaAlO{sub 3}/SrTiO{sub 3} interfaces grown by pulsed laser deposition in O{sub 2} and Ar

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

    Sambri, A.; Amoruso, S.; Bruzzese, R.

    2012-06-04

    Amorphous-LaAlO{sub 3}/SrTiO{sub 3} interfaces exhibit metallic conductivity similar to those found for the extensively studied crystalline-LaAlO{sub 3}/SrTiO{sub 3} interfaces. Here, we investigate the conductivity of the amorphous-LaAlO{sub 3}/SrTiO{sub 3} interfaces grown in different pressures of O{sub 2} and Ar background gases. During the deposition, the LaAlO{sub 3} ablation plume is also studied, in situ, by fast photography and space-resolved optical emission spectroscopy. An interesting correlation between interfacial conductivity and kinetic energy of the Al atoms in the plume is observed: to assure conducting interfaces of amorphous-LaAlO{sub 3}/SrTiO{sub 3}, the kinetic energy of Al should be higher than 1 eV. Ourmore » findings add further insights on mechanisms leading to interfacial conductivity in SrTiO{sub 3}-based oxide heterostructures.« less

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

    Harilal, S. S.; Diwakar, P. K.; Polek, M. P.

    We investigated the role of spot size on plume morphology during ultrafast laser ablation of metal targets. Our results show that the spatial features of fs LA plumes are strongly dependent on the focal spot size. Two-dimensional self-emission images showed that the shape of the ultrafast laser ablation plumes changes from spherical to cylindrical with an increasing spot size from 100 to 600 μm. The changes in plume morphology and internal structures are related to ion emission dynamics from the plasma, where broader angular ion distribution and faster ions are noticed for the smallest spot size used. The present resultsmore » clearly show that the morphological changes in the plume with spot size are independent of laser pulse width.« less

  19. Experimental study of oil plume stability: Parametric dependences and optimization.

    PubMed

    Li, Haoshuai; Shen, Tiantian; Bao, Mutai

    2016-10-15

    Oil plume is known to interact with density layer in spilled oil. Previous studies mainly focused on tracking oil plumes and predicting their impact on marine environment. Here, simulated experiments are presented that investigated the conditions inducing the formation of oil plume, focusing especially on the effects of oil/water volume ratio, oil/dispersant volume rate, ambient stratification and optimal conditions of oil plume on determining whether a plume will trap or escape. Scenario simulations showed that OWR influences the residence time most, dispersants dosage comes second and salinity least. The optimum residence time starts from 2387s, occurred at approximately condition (OWR, 0.1, DOR, 25.53% and salinity, 32.38). No change in the relative distribution under the more scale tank was observed, indicating these provide the time evolution of the oil plumes. Copyright © 2016 Elsevier Ltd. All rights reserved.

  20. Observations of cloud chemistry during longrange transport of power plant plumes

    NASA Astrophysics Data System (ADS)

    Clark, P. A.; Fletcher, I. S.; Kallend, A. S.; McElroy, W. J.; Marsh, A. R. W.; Webb, A. H.

    Measurements of the chemical composition of cloud water have been made as part of a programme to study the chemical development of power plant plumes in trajectories over the North Sea. During a two-day study (28-29 January 1981), the conditions were anticyclonic with light winds advecting the plume from the NE coast of England towards Denmark. The mixing layer overland was capped by stratocumulus beneath a very strong subsidence inversion, which resulted in the plume being entirely trapped within the layer. Low level acceleration occurred as the plume travelled towards the coast, accompanied by a shallowing of the mixing layer. This led to the unusual situation whereby the plume was confined to a shallow (400m) stratocumulus-filled boundary layer throughout most of its travel. The light winds enabled approximately Lagrangian sampling of the plume after about 5 and 22 h travel (~ 100 and 650km from source). The very shallow boundary layer constrained the dilution of the plume to such an extent that even though ambient O 3 was consumed within the plume by the reaction with NO, the NO 2/NO x ratio was still < 0.5 along the plume centre line after 22 h travel. The measurements have been compared with the predictions of a reactive plume model involving both gas phase and solution phase chemistry. The model predicts oxidation rates for SO 2 in the ambient air outside the plume to be substantially higher than those within the plume, at values of 0.5-1.0 and ~ 0.04 % h -1, respectively. This leads to the conclusion that nearly all the sulphate in the plume arose from entrainment of sulphate produced in cloud droplets outside the plume. The absence of an effective oxidation mechanism in solution for the conversion of NOx to HNO 3 suggests that nitrate in the cloud water was derived from the gas phase oxidation of NOx. HC1 was found to be the major contributor to cloud water acidity in the plume on this occasion. The resultant acidity suppressed the solubility of SO 2 and

  1. Stormwater plume detection by MODIS imagery in the southern California coastal ocean

    USGS Publications Warehouse

    Nezlin, N.P.; DiGiacomo, P.M.; Diehl, D.W.; Jones, B.H.; Johnson, S.C.; Mengel, M.J.; Reifel, K.M.; Warrick, J.A.; Wang, M.

    2008-01-01

    Stormwater plumes in the southern California coastal ocean were detected by MODIS-Aqua satellite imagery and compared to ship-based data on surface salinity and fecal indicator bacterial (FIB) counts collected during the Bight'03 Regional Water Quality Program surveys in February-March of 2004 and 2005. MODIS imagery was processed using a combined near-infrared/shortwave-infrared (NIR-SWIR) atmospheric correction method, which substantially improved normalized water-leaving radiation (nLw) optical spectra in coastal waters with high turbidity. Plumes were detected using a minimum-distance supervised classification method based on nLw spectra averaged within the training areas, defined as circular zones of 1.5-5.0-km radii around field stations with a surface salinity of S 33.0 ('ocean'). The plume optical signatures (i.e., the nLw differences between 'plume' and 'ocean') were most evident during the first 2 days after the rainstorms. To assess the accuracy of plume detection, stations were classified into 'plume' and 'ocean' using two criteria: (1) 'plume' included the stations with salinity below a certain threshold estimated from the maximum accuracy of plume detection; and (2) FIB counts in 'plume' exceeded the California State Water Board standards. The salinity threshold between 'plume' and 'ocean' was estimated as 32.2. The total accuracy of plume detection in terms of surface salinity was not high (68% on average), seemingly because of imperfect correlation between plume salinity and ocean color. The accuracy of plume detection in terms of FIB exceedances was even lower (64% on average), resulting from low correlation between ocean color and bacterial contamination. Nevertheless, satellite imagery was shown to be a useful tool for the estimation of the extent of potentially polluted plumes, which was hardly achievable by direct sampling methods (in particular, because the grids of ship-based stations covered only small parts of the plumes detected via

  2. Field experimental observations of highly graded sediment plumes.

    PubMed

    Jensen, Jacob Hjelmager; Saremi, Sina; Jimenez, Carlos; Hadjioannou, Louis

    2015-06-15

    A field experiment in the waters off the south-eastern coast of Cyprus was carried out to study near-field formation of sediment plumes from dumping. Different loads of sediment were poured into calm and limpid waters one at the time from just above the sea surface. The associated plumes, gravitating towards the seafloor, were filmed simultaneously by four divers situated at different depths in the water column, and facing the plume at different angles. The processes were captured using GoPro-Hero-series cameras. The high-quality underwater footage from near-surface, mid-depth and near-bed positions gives unique insight into the dynamics of the descending plume and near-field dispersion processes, and enables good understanding of flow and sediment transport processes involved from-release-to-deposition of the load in a non-scaled environment. The high resolution images and footages are available through the link provided herein. Observations support the development of a detailed multi-fractional sediment plume model. Copyright © 2015 Elsevier Ltd. All rights reserved.

  3. AATSR Based Volcanic Ash Plume Top Height Estimation

    NASA Astrophysics Data System (ADS)

    Virtanen, Timo H.; Kolmonen, Pekka; Sogacheva, Larisa; Sundstrom, Anu-Maija; Rodriguez, Edith; de Leeuw, Gerrit

    2015-11-01

    The AATSR Correlation Method (ACM) height estimation algorithm is presented. The algorithm uses Advanced Along Track Scanning Radiometer (AATSR) satellite data to detect volcanic ash plumes and to estimate the plume top height. The height estimate is based on the stereo-viewing capability of the AATSR instrument, which allows to determine the parallax between the satellite's nadir and 55◦ forward views, and thus the corresponding height. AATSR provides an advantage compared to other stereo-view satellite instruments: with AATSR it is possible to detect ash plumes using brightness temperature difference between thermal infrared (TIR) channels centered at 11 and 12 μm. The automatic ash detection makes the algorithm efficient in processing large quantities of data: the height estimate is calculated only for the ash-flagged pixels. Besides ash plumes, the algorithm can be applied to any elevated feature with sufficient contrast to the background, such as smoke and dust plumes and clouds. The ACM algorithm can be applied to the Sea and Land Surface Temperature Radiometer (SLSTR), scheduled for launch at the end of 2015.

  4. Mantle plumes and hotspot geochemistry

    NASA Astrophysics Data System (ADS)

    Jackson, M. G.; Becker, T. W.; Konter, J.

    2017-12-01

    Ever improving global seismic models, together with expanding databases of mantle derived hotspot lavas, herald advances that relate the geochemistry of hotspots with low seismic shear-wave velocity conduits (plumes) in the mantle. Early efforts linked hotspot geochemistry with deep mantle large low velocity provinces (LLVPs) [1]. More recently, Konter and Becker (2012) [2] observed that the proportion of the C mantle component (inferred from Sr-Nd-Pb isotopes) in hotspot lavas shows an inverse relationship with seismic S-wave velocity anomalies in the shallow mantle (200 km) beneath each hotspot. They proposed that these correlations should also be made based on 3He/4He. Thus, we compare 3He/4He versus seismic S-wave velocity anomalies at 200 km depth. We find that plume-fed hotspots with the highest maximum 3He/4He (i.e., which host more of the C component) have higher hotspot buoyancy fluxes and overlie regions of lower seismic S-wave velocity (interpreted to relate to hotter mantle temperatures) at 200 km depth than hotspots that have only low 3He/4He [3]. This result complements recent work that shows an inverse relationship between maximum 3He/4He and seismic S-wave velocity anomalies in the mantle beneath the western USA [4]. The relationship between 3He/4He, shallow mantle seismic S-wave velocity anomalies, and buoyancy flux is most easily explained by a model where hotter plumes are more buoyant and entrain more of a deep, dense high 3He/4He reservoir than cooler plumes that underlie low 3He/4He hotspots. If the high 3He/4He domain is denser than other mantle components, it will be entrained only by the hottest, most buoyant plumes [3]. Such a deep, dense reservoir is ideally suited to preserving early-formed Hadean domains sampled in modern plume-fed hotspots. An important question is whether, like 3He/4He, seismic S-wave velocity anomalies in the mantle are associated with distinct heavy radiogenic isotopic compositions. C signatures are related to hot

  5. Instability growth seeded by ablator material inhomogeneity in indirect drive implosions on the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Haan, Steven; Ali, S. J.; Baxamusa, S. H.; Celliers, P. M.; Clark, D. S.; Kritcher, A. L.; Nikroo, A.; Stadermann, M.; Biener, J.; Wallace, R.; Smalyuk, V.; Robey, H.; Weber, C. R.; Huang, H.; Reynolds, H.; Carlson, L.; Rice, N.; Kline, J. L.; Simakov, A. N.; Yi, S. A.

    2017-10-01

    NIF indirect drive ablators (CH, Be, and high density carbon HDC) show hydrodynamic irregularity beyond that expected from surface features. Characterizing these seeds and estimating their growth is important in projecting performance. The resulting modulations can be measured in x-ray backlit implosions on NIF called Hydro Growth Radiography, and on Omega with 2D velocimetry. This presentation summarizes the experiments for the three ablators, along with simulations thereof and projections of the significance for NIF. For CH, dominant seeds are photo-induced oxidation, which might be mitigated with alumina coating. For Be, perturbations result from Ar and O contamination. For HDC, perturbations are seeded by shock propagation around melt, depend on shock strength, and may constrain the adiabat of future HDC implosions. Work performed under the auspices of the U.S. D.O.E. by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

  6. Sphere-enhanced microwave ablation (sMWA) versus bland microwave ablation (bMWA): technical parameters, specific CT 3D rendering and histopathology.

    PubMed

    Gockner, T L; Zelzer, S; Mokry, T; Gnutzmann, D; Bellemann, N; Mogler, C; Beierfuß, A; Köllensperger, E; Germann, G; Radeleff, B A; Stampfl, U; Kauczor, H U; Pereira, P L; Sommer, C M

    2015-04-01

    This study was designed to compare technical parameters during ablation as well as CT 3D rendering and histopathology of the ablation zone between sphere-enhanced microwave ablation (sMWA) and bland microwave ablation (bMWA). In six sheep-livers, 18 microwave ablations were performed with identical system presets (power output: 80 W, ablation time: 120 s). In three sheep, transarterial embolisation (TAE) was performed immediately before microwave ablation using spheres (diameter: 40 ± 10 μm) (sMWA). In the other three sheep, microwave ablation was performed without spheres embolisation (bMWA). Contrast-enhanced CT, sacrifice, and liver harvest followed immediately after microwave ablation. Study goals included technical parameters during ablation (resulting power output, ablation time), geometry of the ablation zone applying specific CT 3D rendering with a software prototype (short axis of the ablation zone, volume of the largest aligned ablation sphere within the ablation zone), and histopathology (hematoxylin-eosin, Masson Goldner and TUNEL). Resulting power output/ablation times were 78.7 ± 1.0 W/120 ± 0.0 s for bMWA and 78.4 ± 1.0 W/120 ± 0.0 s for sMWA (n.s., respectively). Short axis/volume were 23.7 ± 3.7 mm/7.0 ± 2.4 cm(3) for bMWA and 29.1 ± 3.4 mm/11.5 ± 3.9 cm(3) for sMWA (P < 0.01, respectively). Histopathology confirmed the signs of coagulation necrosis as well as early and irreversible cell death for bMWA and sMWA. For sMWA, spheres were detected within, at the rim, and outside of the ablation zone without conspicuous features. Specific CT 3D rendering identifies a larger ablation zone for sMWA compared with bMWA. The histopathological signs and the detectable amount of cell death are comparable for both groups. When comparing sMWA with bMWA, TAE has no effect on the technical parameters during ablation.

  7. Effects of meteorological conditions on spore plumes

    NASA Astrophysics Data System (ADS)

    Burch, M.; Levetin, E.

    2002-05-01

    Fungal spores are an ever-present component of the atmosphere, and have long been known to trigger asthma and hay fever symptoms in sensitive individuals. The atmosphere around Tulsa has been monitored for airborne spores and pollen with Burkard spore traps at several sampling stations. This study involved the examination of the hourly spore concentrations on days that had average daily concentrations near 50,000 spores/m3 or greater. Hourly concentrations of Cladosporium, Alternaria, Epicoccum, Curvularia, Pithomyces, Drechslera, smut spores, ascospores, basidiospores, other, and total spores were determined on 4 days at three sites and then correlated with hourly meteorological data including temperature, rainfall, wind speed, dew point, air pressure, and wind direction. On each of these days there was a spore plume, a phenomenon in which spore concentrations increased dramatically over a very short period of time. Spore plumes generally occurred near midday, and concentrations were seen to increase from lows around 20,000 total spores/m3 to highs over 170,000 total spores/m3 in 2 h. Multiple regression analysis of the data indicated that increases in temperature, dew point, and air pressure correlated with the increase in spore concentrations, but no single weather variable predicted the appearance of a spore plume. The proper combination of changes in these meteorological parameters that result in a spore plume may be due to the changing weather conditions associated with thunderstorms, as on 3 of the 4 days when spore plumes occurred there were thunderstorms later that evening. The occurrence of spore plumes may have clinical significance, because other studies have shown that sensitization to certain spore types can occur during exposure to high spore concentrations.

  8. Summary of nozzle-exhaust plume flowfield analyses related to space shuttle applications

    NASA Technical Reports Server (NTRS)

    Penny, M. M.

    1975-01-01

    Exhaust plume shape simulation is studied, with the major effort directed toward computer program development and analytical support of various plume related problems associated with the space shuttle. Program development centered on (1) two-phase nozzle-exhaust plume flows, (2) plume impingement, and (3) support of exhaust plume simulation studies. Several studies were also conducted to provide full-scale data for defining exhaust plume simulation criteria. Model nozzles used in launch vehicle test were analyzed and compared to experimental calibration data.

  9. Ablation of Rotor and Focal Sources Reduces Late Recurrence of Atrial Fibrillation Compared to Trigger Ablation Alone

    PubMed Central

    Narayan, Sanjiv M.; Baykaner, Tina; Clopton, Paul; Schricker, Amir; Lalani, Gautam; Krummen, David E.; Shivkumar, Kalyanam; Miller, John M.

    2014-01-01

    Objectives To determine if ablation that targets patient-specific AF-sustaining substrates (rotors or focal sources) is more durable than trigger ablation alone at preventing late AF recurrences. Background Late recurrence substantially limits the efficacy of pulmonary vein (PV) isolation for AF, and is associated with PV reconnection and the emergence of new triggers. Methods We performed 3 year follow-up of the CONFIRM trial, in which 92 consecutive AF patients (70.7% persistent) underwent novel computational mapping to reveal a median of 2 (IQR 1–2) rotors or focal sources in 97.7% of patients during AF. Ablation comprised source (Focal Impulse and Rotor Modulation, FIRM) then conventional ablation in n=27 (FIRM-guided), and conventional ablation alone in n=65 (FIRM-blinded). Patients were followed with implanted ECG monitors when possible (85.2% FIRM guided, 23.1% FIRM-blinded). Results On 890 days follow-up (median; IQR 224–1563) compared FIRM-blinded therapy, patients receiving FIRM-guided ablation maintained higher freedom from AF after 1.2±0.4 procedures (median 1, IQR 1–1) (77.8% vs 38.5%; p=0.001) and a single procedure (p>0.001), and higher freedom from all atrial arrhythmias (p=0.003). Freedom from AF was higher when ablation directly or coincidentally passed through sources than when it missed sources (p>0.001). CONCLUSIONS FIRM-guided ablation is more durable than conventional trigger-based ablation at preventing 3 year AF recurrence. Future studies should investigate how ablation of patient-specific AF-sustaining rotors and focal sources alters the natural history of arrhythmia recurrence. PMID:24632280

  10. Microwave Ablation of Porcine Kidneys in vivo: Effect of two Different Ablation Modes ('Temperature Control' and 'Power Control') on Procedural Outcome

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

    Sommer, C. M., E-mail: christof.sommer@med.uni-heidelberg.de; Arnegger, F.; Koch, V.

    2012-06-15

    Purpose: This study was designed to analyze the effect of two different ablation modes ('temperature control' and 'power control') of a microwave system on procedural outcome in porcine kidneys in vivo. Methods: A commercially available microwave system (Avecure Microwave Generator; MedWaves, San Diego, CA) was used. The system offers the possibility to ablate with two different ablation modes: temperature control and power control. Thirty-two microwave ablations were performed in 16 kidneys of 8 pigs. In each animal, one kidney was ablated twice by applying temperature control (ablation duration set point at 60 s, ablation temperature set point at 96 Degree-Signmore » C, automatic power set point; group I). The other kidney was ablated twice by applying power control (ablation duration set point at 60 s, ablation temperature set point at 96 Degree-Sign C, ablation power set point at 24 W; group II). Procedural outcome was analyzed: (1) technical success (e.g., system failures, duration of the ablation cycle), and (2) ablation geometry (e.g., long axis diameter, short axis diameter, and circularity). Results: System failures occurred in 0% in group I and 13% in group II. Duration of the ablation cycle was 60 {+-} 0 s in group I and 102 {+-} 21 s in group II. Long axis diameter was 20.3 {+-} 4.6 mm in group I and 19.8 {+-} 3.5 mm in group II (not significant (NS)). Short axis diameter was 10.3 {+-} 2 mm in group I and 10.5 {+-} 2.4 mm in group II (NS). Circularity was 0.5 {+-} 0.1 in group I and 0.5 {+-} 0.1 in group II (NS). Conclusions: Microwave ablations performed with temperature control showed fewer system failures and were finished faster. Both ablation modes demonstrated no significant differences with respect to ablation geometry.« less

  11. EXPERIMENTS ON BUOYANT PLUME DISPERSION IN A LABORATORY CONVENTION TANK

    EPA Science Inventory

    Buoyant plume dispersion in the convective boundary layer (CBL) is investigated experimentally in a laboratory convection tank. The focus is on highly-buoyant plumes that loft near the CBL capping inversion and resist downward mixing. Highly- buoyant plumes are those with dimen...

  12. Mantle plumes on Venus revisited

    NASA Technical Reports Server (NTRS)

    Kiefer, Walter S.

    1992-01-01

    The Equatorial Highlands of Venus consist of a series of quasicircular regions of high topography, rising up to about 5 km above the mean planetary radius. These highlands are strongly correlated with positive geoid anomalies, with a peak amplitude of 120 m at Atla Regio. Shield volcanism is observed at Beta, Eistla, Bell, and Atla Regiones and in the Hathor Mons-Innini Mons-Ushas Mons region of the southern hemisphere. Volcanos have also been mapped in Phoebe Regio and flood volcanism is observed in Ovda and Thetis Regiones. Extensional tectonism is also observed in Ovda and Thetis Regiones. Extensional tectonism is also observed in many of these regions. It is now widely accepted that at least Beta, Atla, Eistla, and Bell Regiones are the surface expressions of hot, rising mantel plumes. Upwelling plumes are consistent with both the volcanism and the extensional tectonism observed in these regions. The geoid anomalies and topography of these four regions show considerable variation. Peak geoid anomalies exceed 90 m at Beta and Atla, but are only 40 m at Eistla and 24 m at Bell. Similarly, the peak topography is greater at Beta and Atla than at Eistla and Bell. Such a range of values is not surprising because terrestrial hotspot swells also have a side range of geoid anomalies and topographic uplifts. Kiefer and Hager used cylindrical axisymmetric, steady-state convection calculations to show that mantle plumes can quantitatively account for both the amplitude and the shape of the long-wavelength geoid and topography at Beta and Atla. In these models, most of the topography of these highlands is due to uplift by the vertical normal stress associated with the rising plume. Additional topography may also be present due to crustal thickening by volcanism and crustal thinning by rifting. Smrekar and Phillips have also considered the geoid and topography of plumes on Venus, but they restricted themselves to considering only the geoid-topography ratio and did not

  13. Large Igneous Provinces, Mantle Plumes, and Continental Break-up: An Overview.

    NASA Astrophysics Data System (ADS)

    Peate, D. W.

    2003-04-01

    Although mantle plumes are widely implicated in models for the generation of large igneous provinces (LIPs) and the break-up of supercontinents such as Gondwana, the exact role of the mantle plume in these processes, and even the very existence of mantle plumes, is controversial and hotly debated. The large volumes of magma produced within a LIP (> 10^6 km^3) in a relative short time interval (< few Myrs) require elevated mantle temperatures such as is inferred for a plume, but it is not easy to determine whether the melting occurred as a result of the arrival of a plume head in the shallow mantle or in response to lithospheric extension. Numerous questions remain unresolved: e.g. Can all LIPs be explained by plume-like mantle upwellings, or are non-plume models such as edge-driven convection a plausible alternative?; Are plumes wet-spots rather than hot-spots?; Do they originate from the core-mantle boundary?; How important is the influence of the overlying lithosphere (limiting the upwelling and extent of melting, modifying the composition of deeper melts, and possibly acting as a source for melts)? In this presentation, I will summarise key observations from three young LIP's (< 135 Ma), each associated with continental break-up. These case studies will be: (i) North Atlantic LIP - Iceland plume, (ii) Parana-Etendeka LIP - Tristan plume, and (iii) Ethiopia-Yemen LIP - Afar plume. Aspects that will be considered include: the areal extent, volume and eruption rates of magmatism; temporal relationship of flood basalt volcanism to lithospheric extension and continental break-up; compositional similarities and differences between the flood basalts and more recent lavas from the associated plume; spatial and temporal compositional variations as a means of assessing the location and length-scales of heterogeneities in the upwelling mantle, seismic tomographic images of mantle thermal structure today; crustal structure of the rifted margins from wide-angle and

  14. Linking Europa’s Plume Activity to Tides, Tectonics, and Liquid Water

    NASA Astrophysics Data System (ADS)

    Rhoden, Alyssa R.; Hurford, Terry; Roth, Lorenz; Retherford, Kurt

    2014-11-01

    Much of the geologic activity preserved on Europa’s icy surface has been attributed to tidal deformation, mainly due to Europa’s eccentric orbit. Although the surface is geologically young, evidence of ongoing tidally-driven processes has been lacking. However, a recent observation of water vapor near Europa’s south pole suggests that it may be geologically active. Non-detections in previous and follow-up observations indicate a temporal variation in plume visibility and suggests a relationship to Europa’s tidal cycle. Similarly, the Cassini spacecraft has observed plumes emanating from the south pole of Saturn’s moon, Enceladus, and variability in the intensity of eruptions has been linked to its tidal cycle. The inference that a similar mechanism controls plumes at both Europa and Enceladus motivates further analysis of Europa’s plume behavior and the relationship between plumes, tides, and liquid water on these two satellites.We determine the locations and orientations of hypothetical tidally-driven fractures that best match the temporal variability of the plumes observed at Europa. Specifically, we identify model faults that are in tension at the time in Europa’s orbit when a plume was detected and in compression at times when the plume was not detected. We find that tidal stress driven solely by eccentricity is incompatible with the observations unless additional mechanisms are controlling the eruption timing or restricting the longevity of the plumes. In contrast, the addition of obliquity tides, and corresponding precession of the spin pole, can generate a number of model faults that are consistent with the pattern of plume detections. The locations and orientations of the model faults are robust across a broad range of precession rates and spin pole directions. Analysis of the stress variations across model faults suggests that the plumes would be best observed earlier in Europa’s orbit. Our results indicate that Europa’s plumes, if

  15. Bio-Physical Coupling of Seabirds and Prey with a Dynamic River Plume

    NASA Astrophysics Data System (ADS)

    Phillips, E. M.; Horne, J. K.; Zamon, J. E.; Adams, J.

    2016-02-01

    Freshwater plumes and plume density fronts are important regions of bio-physical coupling. On the west coast of North America, discharge from the Columbia River into the northern California Current creates a large, dynamic plume and multiple plume fronts. These nutrient-rich, productive waters fuel primary and secondary production, supporting a wide variety of small pelagic prey fish, large populations of Pacific salmon, seabirds, and marine mammals. To determine the influence of the Columbia River plume on marine predators, we analyzed at-sea seabird counts, in situ environmental data, surface trawl densities of prey fish, and acoustic backscatter measurements collected from research vessels in May and June 2010-2012. Concurrent distribution patterns of satellite-tagged sooty shearwaters (Puffinus griseus) and common murres (Uria aalge) were compared with seabird counts from ship surveys. To evaluate plume use by satellite-tagged birds, daily surface salinity values from SELFE hindcast models were extracted at each tag location. Both seabird species occurred in plume waters disproportionate to the total surveyed area, concentrating in the river plume when river flow and plume volume decreased. Murres were consistently within 20 km of the geographic mean center of the river plume. In contrast, shearwaters consistently occurred 100 km to the north of the plume center, where high densities of prey fish occur. Although acoustically detected prey also occurred in greater densities within the plume when volume decreased, surface catches of prey in the plume did not vary with changing plume conditions. Geographic indices of colocation (GIC) were low between murres and prey species caught in surface trawls, whereas GICs were >0.5 between shearwaters and prey species including squid (Loligo opalescens), juvenile Chinook salmon (Oncorhynchus tshawytscha), and coho (O. kisutch) salmon. We conclude that the river plume and associated fronts are identifiable, predictable, and

  16. [Catheter ablation for paroxysmal atrial fibrillation: new generation cryoballoon or contact force sensing radiofrequency ablation?].

    PubMed

    Nagy, Zsófia; Kis, Zsuzsanna; Som, Zoltán; Földesi, Csaba; Kardos, Attila

    2016-05-29

    Contact force sensing radiofrequency ablation and the new generation cryoballoon ablation are prevalent techniques for the treatment of paroxysmal atrial fibrillation. The authors aimed to compare the procedural and 1-year outcome of patients after radiofrequency and cryoballoon ablation. 96 patients with paroxysmal atrial fibrillation (radiofrequency ablation: 58, cryoballoon: 38 patients; 65 men and 31 women aged 28-70 years) were enrolled. At postprocedural 1, 3, 6 and 12 months ECG, Holter monitoring and telephone interviews were performed. Procedure and fluorosocopy time were: radiofrequency ablation, 118.5 ± 15 min and 15.8 ± 6 min; cryoballoon, 73.5 ± 16 min (p<0.05) and 13.8 ± 4.,1 min (p = 0.09), respectively. One year later freedom from atrial fibrillation was achieved in 76.5% of patients who underwent radiofrequency ablation and in 81% of patients treated with cryoballoon. Temporary phrenic nerve palsy occurred in two patients and pericardial tamponade developed in one patient. In this single center study freedom from paroxysmal atrial fibrillation was similar in the two groups with significant shorter procedure time in the cryoballoon group.

  17. Percutaneous Microwave Ablation of Renal Angiomyolipomas.

    PubMed

    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

    2016-03-01

    To evaluate the safety and efficacy of US-guided percutaneous microwave (MW) ablation in the treatment of renal angiomyolipoma (AML). From 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. All 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(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(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. Our 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.

  18. Simple Models of SL-9 Impact Plumes

    NASA Astrophysics Data System (ADS)

    Harrington, J.; Deming, L. D.

    1996-09-01

    The impacts of the larger fragments of Comet Shomaker-Levy 9 on Jupiter left debris patterns of consistent appearance, likely caused by the landing of the observed impact plumes. Realistic fluid simulations of impact plume evolution may take months to years for even single computer runs. To provide guidance for these models and to elucidate the most basic aspects of the plumes, debris patterns, and their ultimate effect on the atmosphere, we have developed simple models that reproduce many of the key features. These Monte-Carlo models divide the plume into discrete mass elements, assign to them a velocity distribution based on numerical impact models, and follow their ballistic trajectories until they hit the planet. If particles go no higher than the observed ~ 3,000 km plume heights, they cannot reach the observed crescent pattern located ~ 10,000 km from the impact sites unless they slide horizontally after ballistic flight. By introducing parameterized sliding or higher trajectories, we can reproduce most of the observed impact features, including the central streak, the crescent, and the ephemeral ring located ~ 30,000 km from the impact sites. We also keep track of the amounts of energy and momentum delivered to the atmosphere as a function of time and location, for use in atmospheric models (D. Deming and J. Harrington, this meeting).

  19. Dynamic behavior of photoablation products of corneal tissue in the mid-IR: a study with FELIX

    NASA Astrophysics Data System (ADS)

    Auerhammer, J. M.; Walker, R.; van der Meer, A. F. G.; Jean, B.

    The properties of pulsed IR-laser ablation of biological soft tissue (porcine cornea) were studied in vitro systematically and quantitatively with a free-electron laser in the wavelength range 6<=λ<=20 μm at fluences ranging from 3.1 to 9.4 J/cm2. Dynamic parameters such as the extension of the ablation cloud, the initial velocity and momentum of the ablated particles as well as the ablation threshold, the ablated mass, and the particle size were investigated. The ablation plume was made visible with a stroboscopic technique. For a fluence of 3.1 J/cm2 the average initial velocity of the ejected particles was deduced from the extension of the plume to range from 120-400 m/s. Measurements of the recoil momentum using a sensitive pendulum led to values between 0.5 and 2.0 mmg/s. All measured properties were related to the spectroscopically determined absorption coefficient of cornea αcornea. Where absorption due to proteins is high (at λ=6.2 and 6.5 μm), ablated mass, velocity and recoil momentum behave according to αcornea. For the first time, variations of the ablation plume from pulse to pulse were observed. Those, as well as the particle size, not only depend on the absorption coefficient, but also on the predominant absorber.

  20. Loire and Gironde turbid plumes: Characterization and influence on thermohaline properties

    NASA Astrophysics Data System (ADS)

    Costoya, X.; Fernández-Nóvoa, D.; deCastro, M.; Gómez-Gesteira, M.

    2017-12-01

    Knowledge and predictability of turbid river plumes is of great importance because they modulate the properties of the seawater adjacent to river mouths. The Loire and Gironde Rivers form the most important plumes in the Bay of Biscay, as they provide > 75% of total runoff. The development of the turbid plume under the influence of its main drivers was analyzed using Moderate Resolution Imaging Spectroradiometer satellite data from the period 2003-2015. River discharge was found to be the main driver, followed by wind, which also had an important effect in modulating the turbid plume during periods of high river discharge. Seaward and upwelling favorable winds enhanced the dispersion of plumes on seawater, whereas landward and downwelling favorable winds limited mixing with the adjacent ocean water. The maximum extension of the turbid plume was reached under landward winds. In addition, the spatio-temporal evolution of the East Atlantic pattern and the North Atlantic Oscillation was observed to affect the dynamics of plumes: positive values of both indices favored a greater extension of the plume. Thermohaline properties differed inside and outside the area affected by both rivers. In particular, these rivers maintain winter stratification inside the turbid plume, which results in a different warming ratio when compared with the adjacent ocean.

  1. Simple models of SL-9 impact plumes in flight

    NASA Astrophysics Data System (ADS)

    Harrington, J.; Deming, D.

    1998-09-01

    We have extended our ballistic Monte-Carlo model of the Shoemaker-Levy 9 impact plumes (J. Harrington and D. Deming 1996. Simple models of SL9 impact plumes, Bull. Am. Astron. Soc. 28 1150--1151) to calculate the appearance of the plumes in flight. We compare these synthetic images to the data taken by the Hubble Space Telescope of plumes on the limb of Jupiter during impacts A, E, G, and W. The model uses a parameterized version of the final power-law velocity distribution from the impact models of Zahnle and Mac Low. The observed plume heights, lightcurve features, and debris patterns fix the values of model parameters. The parameters that best reproduce the debris patterns dictate an approximately conic plume geometry, with the apex of the cone initially near the impact site, the cone's axis pointed in the direction from which the impactor came, and an opening angle >45sp ° from the axis. Since material of a given velocity is, at any given time, a certain distance from the cone apex, the geometry spreads high-velocity material much thinner than low-velocity material. The power law exponent of -1.55 combines with this effect to make mass density fall off as the -3.55 power of the velocity (or distance from the plume base). However, the outer shell of highest-velocity material, corresponding to the atmospheric shock wave, carries considerably elevated mass density. We are currently studying the range of reasonable optical properties to determine whether the visible plume tops corresponded to the physical top of this shell, or to a lower density contour.

  2. Baby-Plumes beneath Central Europe - Indications from seismic studies

    NASA Astrophysics Data System (ADS)

    Achauer, U.; Granet, M.

    2011-12-01

    The most important result of the seismic investigations in the French Massif Central at the beginning of the 1990' (French-German co-operative project Limagne 91/92) was the proof of an ascending material stream from larger depth (250km), which due to its geochemical, petrological and temperature characteristics and its appearance was classified as a plume and which confirmed an already 20 years earlier expressed hypothesis. The really new of the results were that for the first time the exact size and shape of this plume at upper mantle depths was determined, as well as the fact that no plume head ("mushroom") could be found. This led to the expression of "baby plume" for this kind of material up-streaming in order to differentiate this feature to the classical idea of a plume (such as the model by Shilling). The results from the Massif Central triggered similar seismic experiments in other regions of Central Europe with variscan basement and recent volcanism, such as the Eifel plume project and BOHEMA and led to the proof of another such structure beneath the Eifel volcanic region. In contrast to that does the Bohemian massif anomaly more look like a classic asthenospheric upwarp. Recent investigations, in particularily based on additional data from a project across the southern Massif Central, let assume that the origin of these plume like structures lies in the mantle transition zone and that they might be connected to a fossil slab. In this lecture an overview will be given of the current state of affairs concerning the seismic research on baby plumes, as well as possible causes for their presence will be discussed.

  3. Two classes of volcanic plumes on Io

    USGS Publications Warehouse

    McEwen, A.S.; Soderblom, L.A.

    1983-01-01

    Comparison of Voyager 1 and Voyager 2 images of the south polar region of Io has revealed that a major volcanic eruption occured there during the period between the two spacecraft encounters. An annular deposit ???1400 km in diameter formed around the Aten Patera caldera (311??W, 48??S), the floor of which changed from orange to red-black. The characteristics of this eruption are remarkably similar to those described earlier for an eruption centered on Surt caldera (338??W, 45??N) that occured during the same period, also at high latitude, but in the north. Both volcanic centers were evidently inactive during the Voyager 1 and 2 encounters but were active sometime between the two. The geometric and colorimetric characteristics, as well as scale of the two annular deposits, are virtually identical; both resemble the surface features formed by the eruption of Pele (255??W, 18??S). These three very large plume eruptions suggest a class of eruption distinct from that of six smaller plumes observed to be continously active by both Voyagers 1 and 2. The smaller plumes, of which Prometheus is the type example, are longer-lived, deposit bright, whitish material, erupt at velocities of ???0.5 km sec-1, and are concentrated at low latitudes in an equatorial belt around the satellite. The very large Pele-type plumes, on the other hand, are relatively short-lived, deposit darker red materials, erupt at ???1.0 km sec-1, and (rather than restricted to a latitudinal band) are restricted in longitude from 240?? to 360??W. Both direct thermal infrared temperature measurements and the implied color temperatures for quenched liquid sulfur suggest that hot spot temperatures of ???650??K are associated with the large plumes and temperatures 650??K), sulfur is a low-viscosity fluid (orange and black, respectively); at other temperatures it is either solid or has a high viscosity. As a result, there will be two zones in Io's crust in which liquid sulfur will flow freely: a shallow zone

  4. The Green Propellant Infusion Mission Thruster Performance Testing for Plume Diagnostics

    NASA Technical Reports Server (NTRS)

    Deans, Matthew C.; Reed, Brian D.; Arrington, Lynn A.; Williams, George J.; Kojima, Jun J.; Kinzbach, McKenzie I.; McLean, Christopher H.

    2014-01-01

    The Green Propellant Infusion Mission (GPIM) is sponsored by NASA's Space Technology Mission Directorate (STMD) Technology Demonstration Mission (TDM) office. The goal of GPIM is to advance the technology readiness level of a green propulsion system, specifically, one using the monopropellant, AF-M315E, by demonstrating ground handling, spacecraft processing, and on-orbit operations. One of the risks identified for GPIM is potential contamination of sensitive spacecraft surfaces from the effluents in the plumes of AF-M315E thrusters. NASA Glenn Research Center (GRC) is conducting activities to characterize the effects of AF-M315E plume impingement and deposition. GRC has established individual plume models of the 22-N and 1-N thrusters that will be used on the GPIM spacecraft. The model simulations will be correlated with plume measurement data from Laboratory and Engineering Model 22-N, AF-M315E thrusters. The thrusters are currently being tested in a small rocket, altitude facility at NASA GRC. A suite of diagnostics, including Raman spectroscopy, Rayleigh spectroscopy, and Schlieren imaging are being used to acquire plume measurements of AF-M315E thrusters. Plume data will include temperature, velocity, relative density, and species concentration. The plume measurement data will be compared to the corresponding simulations of the plume model. The GRC effort will establish a data set of AF-M315E plume measurements and a plume model that can be used for future AF-M315E applications.

  5. [Radiofrequency ablation of hepatocellular carcinoma].

    PubMed

    Widmann, Gerlig; Schullian, Peter; Bale, Reto

    2013-03-01

    Percutaneous radiofrequency ablation (RFA) is well established in the treatment of hepatocellular carcinoma (HCC). Due to its curative potential, it is the method of choice for non resectable BCLC (Barcelona Liver Clinic) 0 and A. RFA challenges surgical resection for small HCC and is the method of choice in bridging for transplantation and recurrence after resection or transplantation. The technical feasibility of RFA depends on the size and location of the HCC and the availability of ablation techniques (one needle techniques, multi-needle techniques). More recently, stereotactic multi-needle techniques with 3D trajectory planning and guided needle placement substantially improve the spectrum of treatable lesions including large volume tumors. Treatment success depends on the realization of ablations with large intentional margins of tumor free tissue (A0 ablation in analogy to R0 resection), which has to be documented by fusion of post- with pre-ablation images, and confirmed during follow-up imaging.

  6. The adjustment of mantle plumes to changes in plate motion

    NASA Astrophysics Data System (ADS)

    Griffiths, Ross W.; Richards, Mark A.

    1989-05-01

    The relative motion of hotspots and lithospheric plates implies a velocity shear in the underlying mantle, causing horizontal advection of mantle plumes as they rise toward the lithosphere. Consequent tilting of plumes parallel to the direction of plate motion indicates that plumes must undergo a period of readjustment after the velocity vector for plate motion is altered. Thus the shape of bends in the surface tracks of hotspots, resulting from changes in plate motion, will reflect the plume adjustment. Laboratory experiments, as well as computations using a simple theory developed in Richards & Griffiths [1988] for the dynamics of continuous plume conduits, demonstrate that the bend in the surface track has a radius of curvature approximately equal to the maximum horizontal deflection of the conduit. Thus the sharpness of the bend at an age of 43Ma in the Hawaiian-Emperor volcanic chain implies that the deflection of the underlying plume in that case was small (<200 km). This small deflection is expected for plumes carrying large buoyancy fluxes, and it indicates that tilting of the conduit is unlikely to be sufficient to cause diapiric instability.

  7. Experimental and Computational Study of Sonic and Supersonic Jet Plumes

    NASA Technical Reports Server (NTRS)

    Venkatapathy, E.; Naughton, J. W.; Fletcher, D. G.; Edwards, Thomas A. (Technical Monitor)

    1994-01-01

    Study of sonic and supersonic jet plumes are relevant to understanding such phenomenon as jet-noise, plume signatures, and rocket base-heating and radiation. Jet plumes are simple to simulate and yet, have complex flow structures such as Mach disks, triple points, shear-layers, barrel shocks, shock-shear-layer interaction, etc. Experimental and computational simulation of sonic and supersonic jet plumes have been performed for under- and over-expanded, axisymmetric plume conditions. The computational simulation compare very well with the experimental observations of schlieren pictures. Experimental data such as temperature measurements with hot-wire probes are yet to be measured and will be compared with computed values. Extensive analysis of the computational simulations presents a clear picture of how the complex flow structure develops and the conditions under which self-similar flow structures evolve. From the computations, the plume structure can be further classified into many sub-groups. In the proposed paper, detail results from the experimental and computational simulations for single, axisymmetric, under- and over-expanded, sonic and supersonic plumes will be compared and the fluid dynamic aspects of flow structures will be discussed.

  8. The Bounce of SL-9 Impact Ejecta Plumes on Re-Entry

    NASA Astrophysics Data System (ADS)

    Deming, L. D.; Harrington, J.

    1996-09-01

    We have generated synthetic light curves of the re-entry of SL-9 ejecta plumes into Jupiter's atmosphere and have modeled the periodic oscillation of the observed R plume light curves (P. D. Nicholson et al. 1995, Geophys. Res. Lett. 22, 1613--1616) as a hydrodynamic bounce. Our model is separated into plume and atmospheric components. The plume portion of the model is a ballistic Monte Carlo calculation (Harrington and Deming, this meeting). In this paper we describe the atmospheric portion of the model. The infalling plume is divided over a spatial grid (in latitude/longitude). The plume is layered, and joined to a 1-D Lagrangian radiative-hydrodynamic model of the atmosphere, at each grid point. The radiative-hydrodynamic code solves the momentum, energy, and radiative transfer equations for both the infalling plume layers and the underlying atmosphere using an explicit finite difference scheme. It currently uses gray opacities for both the plume and the atmosphere, and the calculations indicate that a much greater opacity is needed for the plume than for the atmosphere. We compute the emergent infrared intensity at each grid point, and integrate spatially to yield a synthetic light curve. These curves exhibit many features in common with observed light curves, including a rapid rise to maximum light followed by a gradual decline due to radiative damping. Oscillatory behavior (the ``bounce'') is a persistent feature of the light curves, and is caused by the elastic nature of the plume impact. In addition to synthetic light curves, the model also calculates temperature profiles for the jovian atmosphere as heated by the plume infall.

  9. 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.

  10. Emerging needle ablation technology in urology.

    PubMed

    Leveillee, Raymond J; Pease, Karli; Salas, Nelson

    2014-01-01

    Thermal ablation of urologic tumors in the form of freezing (cryoablation) and heating (radiofrequency ablation) have been utilized successfully to treat and ablate soft tissue tumors for over 15 years. Multiple studies have demonstrated efficacy nearing that of extirpative surgery for certain urologic conditions. There are technical limitations to their speed and safety profile because of the physical limits of thermal diffusion. Recently, there has been a desire to investigate other forms of energy in an effort to circumvent the limitations of cryoblation and radiofrequency ablation. This review will focus on three relatively new energy applications as they pertain to tissue ablation: microwave, irreversible electroporation, and water vapor. High-intensity-focused ultrasound nor interstitial lasers are discussed, as there have been no recently published updates. Needle and probe-based ablative treatments will continue to play an important role. As three-dimensional imaging workstations move from the advanced radiologic interventional suite to the operating room, surgeons will likely still play a pivotal role in the +-application of these probe ablative devices. It is essential that the surgeon understands the fundamentals of these devices in order to optimize their application.

  11. Sphere-Enhanced Microwave Ablation (sMWA) Versus Bland Microwave Ablation (bMWA): Technical Parameters, Specific CT 3D Rendering and Histopathology

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

    Gockner, T. L., E-mail: theresa.gockner@med.uni-heidelberg.de; Zelzer, S., E-mail: s.zelzer@dkfz-heidelberg.de; Mokry, T., E-mail: theresa.mokry@med.uni-heidelberg.de

    PurposeThis study was designed to compare technical parameters during ablation as well as CT 3D rendering and histopathology of the ablation zone between sphere-enhanced microwave ablation (sMWA) and bland microwave ablation (bMWA).MethodsIn six sheep-livers, 18 microwave ablations were performed with identical system presets (power output: 80 W, ablation time: 120 s). In three sheep, transarterial embolisation (TAE) was performed immediately before microwave ablation using spheres (diameter: 40 ± 10 μm) (sMWA). In the other three sheep, microwave ablation was performed without spheres embolisation (bMWA). Contrast-enhanced CT, sacrifice, and liver harvest followed immediately after microwave ablation. Study goals included technical parameters during ablation (resulting power output,more » ablation time), geometry of the ablation zone applying specific CT 3D rendering with a software prototype (short axis of the ablation zone, volume of the largest aligned ablation sphere within the ablation zone), and histopathology (hematoxylin-eosin, Masson Goldner and TUNEL).ResultsResulting power output/ablation times were 78.7 ± 1.0 W/120 ± 0.0 s for bMWA and 78.4 ± 1.0 W/120 ± 0.0 s for sMWA (n.s., respectively). Short axis/volume were 23.7 ± 3.7 mm/7.0 ± 2.4 cm{sup 3} for bMWA and 29.1 ± 3.4 mm/11.5 ± 3.9 cm{sup 3} for sMWA (P < 0.01, respectively). Histopathology confirmed the signs of coagulation necrosis as well as early and irreversible cell death for bMWA and sMWA. For sMWA, spheres were detected within, at the rim, and outside of the ablation zone without conspicuous features.ConclusionsSpecific CT 3D rendering identifies a larger ablation zone for sMWA compared with bMWA. The histopathological signs and the detectable amount of cell death are comparable for both groups. When comparing sMWA with bMWA, TAE has no effect on the technical parameters during ablation.« less

  12. Microbial populations in contaminant plumes

    USGS Publications Warehouse

    Haack, S.K.; Bekins, B.A.

    2000-01-01

    Efficient biodegradation of subsurface contaminants requires two elements: (1) microbial populations with the necessary degradative capabilities, and (2) favorable subsurface geochemical and hydrological conditions. Practical constraints on experimental design and interpretation in both the hydrogeological and microbiological sciences have resulted in limited knowledge of the interaction between hydrogeological and microbiological features of subsurface environments. These practical constraints include: (1) inconsistencies between the scales of investigation in the hydrogeological and microbiological sciences, and (2) practical limitations on the ability to accurately define microbial populations in environmental samples. However, advances in application of small-scale sampling methods and interdisciplinary approaches to site investigations are beginning to significantly improve understanding of hydrogeological and microbiological interactions. Likewise, culture-based and molecular analyses of microbial populations in subsurface contaminant plumes have revealed significant adaptation of microbial populations to plume environmental conditions. Results of recent studies suggest that variability in subsurface geochemical and hydrological conditions significantly influences subsurface microbial-community structure. Combined investigations of site conditions and microbial-community structure provide the knowledge needed to understand interactions between subsurface microbial populations, plume geochemistry, and contaminant biodegradation.

  13. Biodegradation at Dynamic Plume Fringes: Mixing Versus Reaction Control

    NASA Astrophysics Data System (ADS)

    Cirpka, O. A.; Eckert, D.; Griebler, C.; Haberer, C.; Kürzinger, P.; Bauer, R.; Mellage, A.

    2014-12-01

    Biodegradation of continuously emitted plumes is known to be most pronounced at the plume fringe, where mixing of contaminated water and ambient groundwater, containing dissolved electron acceptors, stimulates microbial activity. Under steady-state conditions, physical mixing of contaminant and electron acceptor by transverse dispersion was shown to be the major bottleneck for biodegradation, with plume lengths scaling inversely with the bulk transverse dispersivity in quasi two-dimensional settings. Under these conditions, the presence of suitable microbes is essential but the biokinetic parameters do not play an important role. When the location of the plume shifts (caused, e.g., by a fluctuating groundwater table), however, the bacteria are no more situated at the plume fringe and biomass growth, decay, activation and deactivation determine the time lag until the fringe-controlled steady state is approached again. During this time lag, degradation is incomplete. The objective of the presented study was to analyze to which extent flow and transport dynamics diminish effectiveness of fringe-controlled biodegradation and which microbial processes and related biokinetic parameters determine the system response in overall degradation to hydraulic fluctuations. We performed experiments in quasi-two-dimensional flow through microcosms on aerobic toluene degradation by Pseudomonas putida F1. Plume dynamics were simulated by vertical alteration of the toluene plume position and experimental results were analyzed by reactive-transport modeling. We found that, even after disappearance of the toluene plume for two weeks, the majority of microorganisms stayed attached to the sediment and regained their full biodegradation potential within two days after reappearance of the toluene plume. Our results underline that besides microbial growth and maintenance (often subsumed as "biomass decay") microbial dormancy (that is, change into a metabolically inactive state) and

  14. The Entrainment Rate for Buoyant Plumes in a Crossflow

    NASA Astrophysics Data System (ADS)

    Devenish, B. J.; Rooney, G. G.; Webster, H. N.; Thomson, D. J.

    2010-03-01

    We consider large-eddy simulations (LES) of buoyant plumes from a circular source with initial buoyancy flux F 0 released into a stratified environment with constant buoyancy frequency N and a uniform crossflow with velocity U. We make a systematic comparison of the LES results with the mathematical theory of plumes in a crossflow. We pay particular attention to the limits {tilde{U}≪1} and {tilde{U}≫ 1}, where {tilde{U}=U/(F_0 N)^{1/4}}, for which analytical results are possible. For {tilde{U}≫ 1}, the LES results show good agreement with the well-known two-thirds law for the rise in height of the plume. Sufficiently far above the source, the centreline vertical velocity of the LES plumes is consistent with the analytical z -1/3 and z -1/2 scalings for respectively {tilde{U}≪ 1} and {tilde{U}≫ 1}. In the general case, where the entrainment is assumed to be the sum of the contributions from the horizontal and vertical velocity components, we find that the discrepancy between the LES data and numerical solutions of the plume equations is largest for {tilde{U}=O(1)}. We propose a modified additive entrainment assumption in which the contributions from the horizontal and vertical velocity components are not equally weighted. We test this against observations of the plume generated by the Buncefield fire in the U.K. in December 2005 and find that the results compare favourably. We also show that the oscillations of the plume as it settles down to its final rise height may be attenuated by the radiation of gravity waves. For {tilde{U}≪ 1} the oscillations decay rapidly due to the transport of energy away from the plume by gravity waves. For {tilde{U}>rsim 1} the gravity waves travel in the same direction and at the same speed as the flow. In this case, the oscillations of the plume do not decay greatly by radiation of gravity waves.

  15. Processing of aerosol particles within the Habshan pollution plume

    NASA Astrophysics Data System (ADS)

    Semeniuk, T. A.; Bruintjes, R.; Salazar, V.; Breed, D.; Jensen, T.; Buseck, P. R.

    2015-03-01

    The Habshan industrial site in the United Arab Emirates produces a regional-scale pollution plume associated with oil and gas processing, discharging high loadings of sulfates and chlorides into the atmosphere, which interact with the ambient aerosol population. Aerosol particles and trace gas chemistry at this site were studied on two flights in the summer of 2002. Measurements were collected along vertical plume profiles to show changes associated with atmospheric processing of particle and gas components. Close to the outlet stack, particle concentrations were over 10,000 cm-3, dropping to <2000 cm-3 in more dilute plume around 1500 m above the stack. Particles collected close to the stack and within the dilute plume were individually measured for size, morphology, composition, and mixing state using transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy. Close to the stack, most coarse particles consisted of mineral dust and NaCl crystals from burning oil brines, while sulfate droplets dominated the fine mode. In more dilute plume, at least 1500 m above the stack, the particle spectrum was more diverse, with a significant increase in internally mixed particle types. Dilute plume samples consisted of coarse NaCl/silicate aggregates or NaCl-rich droplets, often with a sulfate component, while fine-fraction particles were of mixed cation sulfates, also internally mixed with nanospherical soot or silicates. Thus, both chloride and sulfate components of the pollution plume rapidly reacted with ambient mineral dust to form coated and aggregate particles, enhancing particle size, hygroscopicity, and reactivity of the coarse mode. The fine-fraction sulfate-bearing particles formed in the plume contribute to regional transport of sulfates, while coarse sulfate-bearing fractions locally reduced the SO2 loading through sedimentation. The chloride- and sulfate-bearing internally mixed particles formed in the plume markedly changed the

  16. Mantle Plumes and Geologically Recent Volcanism on Mars

    NASA Astrophysics Data System (ADS)

    Kiefer, W. S.

    2013-12-01

    Despite its small size, Mars has remained volcanically active until the geologically recent past. Crater retention ages on the volcanos Arsia Mon, Olympus Mons, and Pavonis Mons indicate significant volcanic activity in the last 100-200 million years. The radiometric ages of many shergottites, a type of igneous martian meteorite, indicate igneous activity at about 180 million years ago. These ages correspond to the most recent 2-4% of the age of the Solar System. The most likely explanation for this young martian volcanism is adiabatic decompression melting in upwelling mantle plumes. Multiple plumes may be active at any time, with each of the major volcanos in the Tharsis region being formed by a separate plume. Like at least some terrestrial mantle plumes, mantle plumes on Mars likely form via an instability of the thermal boundary layer at the base of the mantle. Because Mars operates in the stagnant lid convection regime, the temperature difference between mantle and core is lower than on Earth. This reduces the temperature contrast between mantle and core, resulting in mantle plumes on Mars that are about 100 K hotter than the average mantle. The chemical composition of the martian meteorites indicates that the martian mantle is enriched in both iron and sodium relative to Earth's mantle. This lowers the dry solidus on early Mars by 30-40 K relative to Earth. Migration of sodium to the crust over time decreases this difference in solidus temperature to about 15 K at present, but that is sufficient to increase the current plume magma production rate by a factor of about 2. Hydrous phases in the martian meteorites indicate the presence of a few hundred ppm water in the mantle source region, roughly the same as Earth. Finite element simulations of martian plumes using temperature-dependent viscosity and realistic Rayleigh numbers can reproduce the geologically recent magma production rate that is inferred from geologic mapping and the melt fraction inferred from

  17. Velocity variations of an Equatorial plume throughout a Jovian year

    NASA Technical Reports Server (NTRS)

    Reese, E.; Beebe, R. F.

    1975-01-01

    Features in the equatorial zone of Jupiter show that the equatorial plume reported by Pioneer 10 has existed for an 11-year interval. During this interval the plume has shown an acceleration which can be interpreted as a constant component of 3 x 10 to minus 8th power m/sq cm and a sinusoidal component which anticorrelates with the planetocentric declination of the sun, D sub s, and has an amplitude of -0.96 meters per second per degree change of D sub s. The sinusoidal component has been interpreted in terms of solar heating. Throughout this interval of time the equatorial zone has appeared abnormally dark and has contained many dark projections along the northern edge. When the plume approaches to within 25 to 30 deg of these features they are deflected in the direction of motion of the plume and then dissipate or become obscured as the plume passes. After passage of the plume normal features are again observed.

  18. Infrared Signature Modeling and Analysis of Aircraft Plume

    NASA Astrophysics Data System (ADS)

    Rao, Arvind G.

    2011-09-01

    In recent years, the survivability of an aircraft has been put to task more than ever before. One of the main reasons is the increase in the usage of Infrared (IR) guided Anti-Aircraft Missiles, especially due to the availability of Man Portable Air Defence System (MANPADS) with some terrorist groups. Thus, aircraft IR signatures are gaining more importance as compared to their radar, visual, acoustic, or any other signatures. The exhaust plume ejected from the aircraft is one of the important sources of IR signature in military aircraft that use low bypass turbofan engines for propulsion. The focus of the present work is modelling of spectral IR radiation emission from the exhaust jet of a typical military aircraft and to evaluate the aircraft susceptibility in terms of the aircraft lock-on range due to its plume emission, for a simple case against a typical Surface to Air Missile (SAM). The IR signature due to the aircraft plume is examined in a holistic manner. A comprehensive methodology of computing IR signatures and its affect on aircraft lock-on range is elaborated. Commercial CFD software has been used to predict the plume thermo-physical properties and subsequently an in-house developed code was used for evaluating the IR radiation emitted by the plume. The LOWTRAN code has been used for modeling the atmospheric IR characteristics. The results obtained from these models are in reasonable agreement with some available experimental data. The analysis carried out in this paper succinctly brings out the intricacy of the radiation emitted by various gaseous species in the plume and the role of atmospheric IR transmissivity in dictating the plume IR signature as perceived by an IR guided SAM.

  19. Bio-Inspired Navigation of Chemical Plumes

    DTIC Science & Technology

    2006-07-01

    Bio-Inspired Navigation of Chemical Plumes Maynard J. Porter III, Captain, USAF Department of Electrical and Computer Engineering Air Force Institute...Li. " Chemical plume tracing via an autonomous underwater vehicle". IEEE Journal of Ocean Engineering , 30(2):428— 442, 2005. [6] G. A. Nevitt...Electrical and Computer Engineering Air Force Institute of Technology Dayton, OH 45433-7765, U.S.A. juan.vasquez@afit.edu May 31, 2006 Abstract - The

  20. Comparison of FDNS liquid rocket engine plume computations with SPF/2

    NASA Technical Reports Server (NTRS)

    Kumar, G. N.; Griffith, D. O., II; Warsi, S. A.; Seaford, C. M.

    1993-01-01

    Prediction of a plume's shape and structure is essential to the evaluation of base region environments. The JANNAF standard plume flowfield analysis code SPF/2 predicts plumes well, but cannot analyze base regions. Full Navier-Stokes CFD codes can calculate both zones; however, before they can be used, they must be validated. The CFD code FDNS3D (Finite Difference Navier-Stokes Solver) was used to analyze the single plume of a Space Transportation Main Engine (STME) and comparisons were made with SPF/2 computations. Both frozen and finite rate chemistry models were employed as well as two turbulence models in SPF/2. The results indicate that FDNS3D plume computations agree well with SPF/2 predictions for liquid rocket engine plumes.

  1. A Model for Temperature Fluctuations in a Buoyant Plume

    NASA Astrophysics Data System (ADS)

    Bisignano, A.; Devenish, B. J.

    2015-11-01

    We present a hybrid Lagrangian stochastic model for buoyant plume rise from an isolated source that includes the effects of temperature fluctuations. The model is based on that of Webster and Thomson (Atmos Environ 36:5031-5042, 2002) in that it is a coupling of a classical plume model in a crossflow with stochastic differential equations for the vertical velocity and temperature (which are themselves coupled). The novelty lies in the addition of the latter stochastic differential equation. Parametrizations of the plume turbulence are presented that are used as inputs to the model. The root-mean-square temperature is assumed to be proportional to the difference between the centreline temperature of the plume and the ambient temperature. The constant of proportionality is tuned by comparison with equivalent statistics from large-eddy simulations (LES) of buoyant plumes in a uniform crossflow and linear stratification. We compare plume trajectories for a wide range of crossflow velocities and find that the model generally compares well with the equivalent LES results particularly when added mass is included in the model. The exception occurs when the crossflow velocity component becomes very small. Comparison of the scalar concentration, both in terms of the height of the maximum concentration and its vertical spread, shows similar behaviour. The model is extended to allow for realistic profiles of ambient wind and temperature and the results are compared with LES of the plume that emanated from the explosion and fire at the Buncefield oil depot in 2005.

  2. Electron Scattering by Plasmaspheric Hiss in a Nightside Plume

    NASA Astrophysics Data System (ADS)

    Zhang, Wenxun; Fu, Song; Gu, Xudong; Ni, Binbin; Xiang, Zheng; Summers, Danny; Zou, Zhengyang; Cao, Xing; Lou, Yuequn; Hua, Man

    2018-05-01

    Plasmaspheric hiss is known to play an important role in radiation belt electron dynamics in high plasma density regions. We present observations of two crossings of a plasmaspheric plume by the Van Allen Probes on 26 December 2012, which occurred unusually at the post-midnight-to-dawn sector between L 4-6 during a geomagnetically quiet period. This plume exhibited pronounced electron densities higher than those of the average plume level. Moderate hiss emissions accompanied the two plume crossings with the peak power at about 100 Hz. Quantification of quasi-linear bounce-averaged electron scattering rates by hiss in the plume demonstrates that the waves are efficient to pitch angle scatter 10-100 keV electrons at rates up to 10-4 s-1 near the loss cone but become gradually insignificant to scatter the higher energy electron population. The resultant timescales of electron loss due to hiss in the nightside plume vary largely with electron kinetic energy over 3 orders of magnitude, that is, from several hours for tens of keV electrons to a few days for hundreds of keV electrons to well above 100 days for >1 MeV electrons. Changing slightly with L-shell and the multiquartile profile of hiss spectral intensity, these electron loss timescales suggest that hiss emissions in the nightside plume act as a viable candidate for the fast loss of the ≲100 keV electrons and the slow decay of higher energy electrons.

  3. [Thoracoscopic, epicardial ablation of atrial fibrillation using the COBRA Fusion system as the first part of hybrid ablation].

    PubMed

    Budera, P; Osmančík, P; Talavera, D; Fojt, R; Kraupnerová, A; Žďárská, J; Vaněk, T; Straka, Z

    2017-01-01

    Treatment of persistent and long-standing persistent atrial fibrillation is not successfully managed by methods of catheter ablation or pharmacotherapy. Hybrid ablation (i.e. combination of minimally invasive surgical ablation, followed by electrophysiological assessment and subsequent endocardial catheter ablation to complete the entire intended procedure) presents an ever more used and very promising treatment method. Patients underwent thoracoscopic ablation of pulmonary veins and posterior wall of the left atrium (the box-lesion) with use of the COBRA Fusion catheter; thoracoscopic occlusion of the left atrial appendage using the AtriClip system was also done in later patients. After 23 months, electrophysiological assessment and catheter ablation followed. In this article we summarize a strategy of the surgical part of the hybrid procedure performed in our centre. We describe the surgery itself (including possible periprocedural complications) and we also present our short-term results, especially with respect to subsequent electrophysiological findings. Data of the first 51 patients were analyzed. The first 25 patients underwent unilateral ablation; the mean time of surgery was 102 min. Subsequent 26 patients underwent the bilateral procedure with the mean surgery time of 160 min. Serious complications included 1 stroke, 1 phrenic nerve palsy and 2 surgical re-explorations for bleeding. After 1 month, 65% of patients showed sinus rhythm. The box-lesion was found complete during electrophysiological assessment in 38% of patients and after catheter ablation, 96% of patients were discharged in sinus rhythm. The surgical part of the hybrid procedure with use of the minimally invasive approach and the COBRA Fusion catheter is a well-feasible method with a low number of periprocedural complications. For electrophysiologists, it provides a very good basis for successful completion of the hybrid ablation.Key words: atrial fibrillation hybrid ablation - thoracoscopy

  4. Key factors controlling ozone production in wildfire plumes

    NASA Astrophysics Data System (ADS)

    Jaffe, D. A.

    2017-12-01

    Production of ozone in wildfire plumes is complex and highly variable. As a wildfire plume mixes into an urban area, ozone is often, but not always, produced. We have examined multiple factors that can help explain some of this variability. This includes CO/NOy enhancement ratios, photolysis rates, PAN/NOy fraction and degree of NOx oxidation. While fast ozone production is well known, on average, ozone production increases downwind in a plume for several days. Peroxyacetyl nitrate (PAN) is likely a key cause for delayed ozone formation. Recent observations at the Mt. Bachelor Observatory a mountain top observatory relatively remote from nearby anthropogenic influence and in Boise Idaho, an urban setting, show the importance of PAN in wildfire plumes. From these observations we can devise a conceptual model that considers four factors in ozone production: NOx/VOC emission ratio; degree of NOx oxidation; transport time and pathway; and mixing with urban pollutants. Using this conceptual model, we can then devise a lagrangian modeling strategy that can be used to improve our understanding of ozone production in wildfire plumes, both in remote and urban settings.

  5. CHLORINATED SOLVENT PLUME CONTROL

    EPA Science Inventory

    This lecture will cover recent success in controlling and assessing the treatment of shallow ground water plumes of chlorinated solvents, other halogenated organic compounds, and methyl tert-butyl ether (MTBE).

  6. Pleural Puncture that Excludes the Ablation Zone Decreases the Risk of Pneumothorax after Percutaneous Microwave Ablation in Porcine Lung

    PubMed Central

    Lee, Kyungmouk Steve; Takaki, Haruyuki; Yarmohammadi, Hooman; Srimathveeravalli, Govindarajan; Luchins, Kerith; Monette, Sébastien; Nair, Sreejit; Kishore, Sirish; Erinjeri, Joseph P.

    2017-01-01

    Purpose To test the hypothesis that the geometry of probe placement with respect to the pleural puncture site affects the risk of pneumothorax after microwave (MW) ablation in the lung. Materials and Methods Computed tomography–guided MW ablation of the lung was performed in 8 swine under general anesthesia and mechanical ventilation. The orientation of the 17-gauge probe was either perpendicular (90°) or parallel (< 30°) with respect to the pleural puncture site, and the ablation power was 30 W or 65 W for 5 minutes. After MW ablation, swine were euthanized, and histopathologic changes were assessed. Frequency and factors affecting pneumothorax were evaluated by multivariate analysis. Results Among 62 lung MW ablations, 13 (21%) pneumothoraces occurred. No statistically significant difference was noted in the rate of pneumothorax between the perpendicular and the parallel orientations of the probe (31% vs 14%; odds ratio [OR], 2.8; P = .11). The pneumothorax rate was equal for 65-W and 30-W ablation powers (21% and 21%; OR, 1.0; P = .94). Under multivariate analysis, 2 factors were independent positive predictors of pneumothorax: ablation zone inclusive of pleural insertion point (OR, 7.7; P = .02) and time since intubation (hours) (OR, 2.7; P = .02). Conclusions Geometries where the pleural puncture site excluded the ablation zone decreased pneumothorax in swine undergoing MW ablation in the lung. Treatment planning to ensure that the pleural puncture site excludes the subsequent ablation zone may reduce the rate of pneumothorax in patients undergoing MW ablation in the lung. PMID:25753501

  7. Development of a reactive-dispersive plume model

    NASA Astrophysics Data System (ADS)

    Kim, Hyun S.; Kim, Yong H.; Song, Chul H.

    2017-04-01

    A reactive-dispersive plume model (RDPM) was developed in this study. The RDPM can consider two main components of large-scale point source plume: i) turbulent dispersion and ii) photochemical reactions. In order to evaluate the simulation performance of newly developed RDPM, the comparisons between the model-predicted and observed mixing ratios were made using the TexAQS II 2006 (Texas Air Quality Study II 2006) power-plant experiment data. Statistical analyses show good correlation (0.61≤R≤0.92), and good agreement with the Index of Agreement (0.70≤R≤0.95). The chemical NOx lifetimes for two power-plant plumes (Monticello and Welsh power plants) were also estimated.

  8. RAPID REMOVAL OF A GROUNDWATER CONTAMINANT PLUME.

    USGS Publications Warehouse

    Lefkoff, L. Jeff; Gorelick, Steven M.; ,

    1985-01-01

    A groundwater management model is used to design an aquifer restoration system that removes a contaminant plume from a hypothetical aquifer in four years. The design model utilizes groundwater flow simulation and mathematical optimization. Optimal pumping and injection strategies achieve rapid restoration for a minimum total pumping cost. Rapid restoration is accomplished by maintaining specified groundwater velocities around the plume perimeter towards a group of pumping wells located near the plume center. The model does not account for hydrodynamic dispersion. Results show that pumping costs are particularly sensitive to injection capacity. An 8 percent decrease in the maximum allowable injection rate may lead to a 29 percent increase in total pumping costs.

  9. Photogrammetric and photometric investigation of a smoke plume viewed from space.

    NASA Technical Reports Server (NTRS)

    Randerson, D.; Garcia, J. G.; Whitehead, V. S.

    1971-01-01

    Use of detailed analyses of an Apollo 6 stereographic photograph of a smoke plume which originated in southern Arizona and crossed over into Mexico to illustrate how high-resolution photography can aid meteorologists in evaluating specific air pollution events. Photogrammetric analysis of the visible smoke plume revealed that the plume was 8.06 miles long and attained a maximum width of 4000 ft, 3.0 miles from the 570-ft chimney emitting the effluent. Stereometric analysis showed that the visible top of the plume rose nearly 2400 ft above stack top, attaining 90% of this total rise 1.75 miles downwind from the source. Photometric analysis of the plume revealed a field of plume optical density that portrayed leptokurtic and bimodal distributions rather than a true Gaussian distribution. A horizontal eddy diffusivity of about 650,000 sq cm/sec and a vertical eddy diffusivity of 230,000 sq cm/sec were determined from the plume dimensions. Neutron activation analysis of plume samples revealed the elemental composition of the smoke to be copper, arsenic, selenium, indium and antimony, with trace amounts of vanadium and scandium.

  10. Efficacy and Safety of Radiofrequency Ablation for Focal Hepatic Lesions Adjacent to Gallbladder: Reconfiguration of the Ablation Zone through Probe Relocation and Ablation Time Reduction.

    PubMed

    Choi, In Young; Kim, Pyo Nyun; Lee, Sung Gu; Won, Hyung Jin; Shin, Yong Moon

    2017-10-01

    To evaluate the safety and efficacy of radiofrequency (RF) ablation for treatment of focal hepatic lesions adjacent to the gallbladder with electrode relocation and ablation time reduction. Thirty-nine patients who underwent RF ablation for focal hepatic lesions adjacent to the gallbladder (≤ 10 mm) were evaluated retrospectively from January 2011 to December 2014 (30 men and 9 women; age range, 51-85 y; mean age, 65 y). Of 36 patients with hepatocellular carcinoma, 3 had a second treatment for recurrence (mean tumor size, 15 mm ± 6). Patients were divided into 2 subgroups based on lesion distance from the gallbladder: nonabutting (> 5 mm; n = 19) and abutting (≤ 5 mm; n = 20). Electrodes were inserted parallel to the gallbladder through the center of a tumor in the nonabutting group and through the center of the expected ablation zone between a 5-mm safety zone on the liver side and the gallbladder in the abutting group. Ablation time was decreased in proportion to the transverse diameter of the expected ablation zone. Technical success and technical effectiveness rates were 89.7% and 97.4%, respectively, with no significant differences between groups (P = 1.00). Local tumor progression was observed in 3 patients (1 in the nonabutting group and 2 in the abutting group; P = 1.00). There were no major complications. The gallbladder was thickened in 10 patients, with no significant difference between groups (P = .72). Biloma occurred in 1 patient in the nonabutting group. RF ablation with electrode relocation and reduction of ablation time can be a safe and effective treatment for focal hepatic lesions adjacent to the gallbladder. Copyright © 2017 SIR. Published by Elsevier Inc. All rights reserved.

  11. Bifurcation of the Yellowstone plume driven by subduction-induced mantle flow

    NASA Astrophysics Data System (ADS)

    Kincaid, C.; Druken, K. A.; Griffiths, R. W.; Stegman, D. R.

    2013-05-01

    The causes of volcanism in the northwestern United States over the past 20 million years are strongly contested. Three drivers have been proposed: melting associated with plate subduction; tectonic extension and magmatism resulting from rollback of a subducting slab; or the Yellowstone mantle plume. Observations of the opposing age progression of two neighbouring volcanic chains--the Snake River Plain and High Lava Plains--are often used to argue against a plume origin for the volcanism. Plumes are likely to occur near subduction zones, yet the influence of subduction on the surface expression of mantle plumes is poorly understood. Here we use experiments with a laboratory model to show that the patterns of volcanism in the northwestern United States can be explained by a plume upwelling through mantle that circulates in the wedge beneath a subduction zone. We find that the buoyant plume may be stalled, deformed and partially torn apart by mantle flow induced by the subducting plate. Using plausible model parameters, bifurcation of the plume can reproduce the primary volcanic features observed in the northwestern United States, in particular the opposite progression of two volcanic chains. Our results support the presence of the Yellowstone plume in the northwestern United States, and also highlight the power of plume-subduction interactions to modify surface geology at convergent plate margins.

  12. Optimal approach for complete liver tumor ablation using radiofrequency ablation: a simulation study.

    PubMed

    Givehchi, Sogol; Wong, Yin How; Yeong, Chai Hong; Abdullah, Basri Johan Jeet

    2018-04-01

    To investigate the effect of radiofrequency ablation (RFA) electrode trajectory on complete tumor ablation using computational simulation. The RFA of a spherical tumor of 2.0 cm diameter along with 0.5 cm clinical safety margin was simulated using Finite Element Analysis software. A total of 86 points inside one-eighth of the tumor volume along the axial, sagittal and coronal planes were selected as the target sites for electrode-tip placement. The angle of the electrode insertion in both craniocaudal and orbital planes ranged from -90° to +90° with 30° increment. The RFA electrode was simulated to pass through the target site at different angles in combination of both craniocaudal and orbital planes before being advanced to the edge of the tumor. Complete tumor ablation was observed whenever the electrode-tip penetrated through the epicenter of the tumor regardless of the angles of electrode insertion in both craniocaudal and orbital planes. Complete tumor ablation can also be achieved by placing the electrode-tip at several optimal sites and angles. Identification of the tumor epicenter on the central slice of the axial images is essential to enhance the success rate of complete tumor ablation during RFA procedures.

  13. An analytic model of axisymmetric mantle plume due to thermal and chemical diffusion

    NASA Technical Reports Server (NTRS)

    Liu, Mian; Chase, Clement G.

    1990-01-01

    An analytic model of axisymmetric mantle plumes driven by either thermal diffusion or combined diffusion of both heat and chemical species from a point source is presented. The governing equations are solved numerically in cylindrical coordinates for a Newtonian fluid with constant viscosity. Instead of starting from an assumed plume source, constraints on the source parameters, such as the depth of the source regions and the total heat input from the plume sources, are deduced using the geophysical characteristics of mantle plumes inferred from modelling of hotspot swells. The Hawaiian hotspot and the Bermuda hotspot are used as examples. Narrow mantle plumes are expected for likely mantle viscosities. The temperature anomaly and the size of thermal plumes underneath the lithosphere can be sensitive indicators of plume depth. The Hawaiian plume is likely to originate at a much greater depth than the Bermuda plume. One suggestive result puts the Hawaiian plume source at a depth near the core-mantle boundary and the source of the Bermuda plume in the upper mantle, close to the 700 km discontinuity. The total thermal energy input by the source region to the Hawaiian plume is about 5 x 10(10) watts. The corresponding diameter of the source region is about 100 to 150 km. Chemical diffusion from the same source does not affect the thermal structure of the plume.

  14. Lightning in Colorado forest fire smoke plumes during summer 2012

    NASA Astrophysics Data System (ADS)

    Lang, T. J.; Krehbiel, P. R.; Dolan, B.; Lindsey, D.; Rutledge, S. A.; Rison, W.

    2012-12-01

    May and June 2012 were unusually hot and dry in Colorado, which was suffering from a strong drought. A major consequence of this climatic regime was one of the most destructive forest fire seasons in state history, with hundreds of thousands of acres of forest and grassland consumed by flames, hundreds of homes burned, and several lives lost. Many of these fires occurred within range of the newly installed Colorado Lightning Mapping Array (COLMA), which provides high-resolution observations of discharges over a large portion of the state. The COLMA was installed in advance of the Deep Convective Clouds and Chemistry (DC3) project. High-altitude lightning was observed to occur sporadically in the smoke plumes over three major fires that occurred during early summer: Hewlett Gulch, High Park, and Waldo Canyon. Additionally, the Colorado State University CHILL (CSU-CHILL) and Pawnee radars observed the Hewlett Gulch plume electrify with detailed polarimetric and dual-Doppler measurements, and also provided these same measurements for the High Park plume when it was not producing lightning. Meanwhile, local Next Generation Radars (NEXRADs) provided observations of the electrified High Park and Waldo Canyon plumes. All of these plumes also were observed by geostationary meteorological satellites. These observations provide an unprecedented dataset with which to study smoke plume and pyrocumulus electrification. The polarimetric data - low reflectivity, high differential reflectivity, low correlation coefficient, and noisy differential phase - were consistent with the smoke plumes and associated pyrocumulus being filled primarily with irregularly shaped ash particles. Lightning was not observed in the plumes until they reached over 10 km above mean sea level, which was an uncommon occurrence requiring explosive fire growth combined with increased meteorological instability and reduced wind shear. Plume updraft intensification and echo-top growth led the occurrence of

  15. Dynamics of fire plumes in verticle shear

    Treesearch

    Philip Cunningham; Scott L. Goodrick; Hussaini M. Yousuff; Rodman R. Linn; Chunmei Xia

    2003-01-01

    Plumes from wildfires and prescribed fires represent a critical aspect of smoke mangement and aire quality assessment, as as such it is important to understand the structure and dynamics of these plumes, both with respect to a basic understanding of the phenomena and with respect to an assessment of the validity of plumerise parameterizations over a wide variety of...

  16. Io with Loki Plume on Bright Limb

    NASA Image and Video Library

    1996-06-03

    NASA's Voyager 1 image of Io showing active plume of Loki on limb. Heart-shaped feature southeast of Loki consists of fallout deposits from active plume Pele. The images that make up this mosaic were taken from an average distance of approximately 490,000 kilometers (340,000 miles). http://photojournal.jpl.nasa.gov/catalog/PIA00010

  17. PLUME-SCALER-EVALUATING LONG-TERM MONITORING WELL NETWORKS

    EPA Science Inventory

    EPA's Subsurface Protection and Remediation Division is developing a new computer application called PLUME-SCALER to evaluate long term monitoring well networks using typically available historical site water level data. PLUME-SCALER can be used to determine if there are enough ...

  18. 40 CFR Appendix Vi to Part 266 - Stack Plume Rise

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 27 2011-07-01 2011-07-01 false Stack Plume Rise VI Appendix VI to Part 266 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED... FACILITIES Pt. 266, App. VI Appendix VI to Part 266—Stack Plume Rise [Estimated Plume Rise (in Meters) Based...

  19. 40 CFR Appendix Vi to Part 266 - Stack Plume Rise

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 26 2010-07-01 2010-07-01 false Stack Plume Rise VI Appendix VI to Part 266 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED... FACILITIES Pt. 266, App. VI Appendix VI to Part 266—Stack Plume Rise [Estimated Plume Rise (in Meters) Based...

  20. Observations of currents and density structure across a buoyant plume front

    USGS Publications Warehouse

    Gelfenbaum, G.; Stumpf, R.P.

    1993-01-01

    Observations of the Mobile Bay, Alabama, plume during a flood event in April 1991 reveal significant differences in the current field on either side of a front associated with the buoyant plume. During a strong southeasterly wind, turbid, low salinity water from Mobile Bay was pushed through an opening in the west side of the ebb-tidal delta and moved parallel to the coast. A stable front developed between the low salinity water of the buoyant plume (11‰) and the high salinity coastal water (>23‰) that was being forced landward by the prevailing winds. Despite the shallow water depth of 6 m, measurements of currents, temperature, and salinity show large shears and density gradients in both the vertical and the horizontal directions. At a station outside of the buoyant plume, currents at 0.5 m and 1.5 m below the surface were in the same direction as the wind. Inside the plume, however, currents at 0.5 m below the surface were parallel to the coast, 45°, off the direction of the wind and the magnitude was 45% larger than the magnitude of the surface currents outside the plume. Beneath the level of the plume, the currents were identical to the wind-driven currents in the ambient water south of the front. Our observations suggest that the wind-driven surface currents of the ambient water converged with the buoyant plume at the front and were subducted beneath the plume. The motion of the ambient coastal surface water was in the direction of the local wind stress, however, the motion of the plume had no northerly component of motion. The plume also did not show any flow toward the front, suggesting a balance between the northerly component of wind stress and the southerly component of buoyant spreading. In addition, the motion of the plume did not appear to affect the motion of the underlying ambient water, suggesting a lack of mixing between the two waters.