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.

Analysis of bubble plume spacing produced by regular breaking waves

NASA Astrophysics Data System (ADS)

Phaksopa, J.; Haller, M. C.

2012-12-01

The breaking wave process in the ocean is a significant mechanism for energy dissipation, splash, and entrainment of air. The relationship between breaking waves and bubble plume characteristics is still a mystery because of the complexity of the breaking wave mechanism. This study takes a unique approach to quantitatively analyze bubble plumes produced by regular breaking waves. Various previous studies have investigated the formation and the characteristics of bubble plumes using either field observations, laboratory experiments, or numerical modeling However, in most observational work the plume characteristics have been studied from the underneath the water surface. In addition, though numerical simulations are able to include much of the important physics, the computational costs are high and bubble plume events are only simulated for short times. Hence, bubble plume evolution and generation throughout the surf zone is not yet computationally feasible. In the present work we take a unique approach to analyzing bubble plumes. These data may be of use for model/data comparisons as numerical simulations become more tractable. The remotely sensed video data from freshwater breaking waves in the OSU Large Wave Flume (Catalan and Haller, 2008) are analyzed. The data set contains six different regular wave conditions and the video intensity data are used to estimate the spacing of plume events (wavenumber spectrum), to calculate the spectral width (i.e. the range of plume spacing), and to relate these with the wave conditions. The video intensity data capture the evolution of the wave passage over a fixed bed arranged in a bar-trough morphology. Bright regions represent the moving path or trajectory coincident with bubble plume of each wave. It also shows the bubble foam were generated and released from wave crest shown in the form of bubble tails with almost regular spacing for each wave. The bubble tails show that most bubbles did not move along with wave. For the

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.

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.

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

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

SciTech Connect

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

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

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.

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.

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.

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.

Diagnostics of Carbon Nanotube Formation in a Laser Produced Plume

NASA Technical Reports Server (NTRS)

DeBoer, Gary

2000-01-01

This research has involved the analysis and interpretation of spectroscopic data taken over a two year period from 1998 to 1999 at the Johnson Space Center. The data was taken in an attempt to perform diagnostic studies of the formation of carbon nanotubes in a laser produced plume. Carbon nanotubes hold great promise for the development of new materials with exciting properties. Current production processes are not sufficient to meet research and development needs. A better understanding of the chemical processes involved in carbon nanotube formation will suggest better production processes that would be more able to meet the demands of research and development. Our work has focused on analysis of the emission spectra and laser induced fluorescent spectra of the carbon dimer, C2, and the laser induced fluorescence spectra of the nickel atom, which is a necessary reagent in th formation of carbon nanotubes.

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

SciTech Connect

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

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.

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

SciTech Connect

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

Appearance and water quality of turbidity plumes produced by dredging in Tampa Bay, Florida

USGS Publications Warehouse

Goodwin, Carl R.; Michaelis, D.M.

1984-01-01

Turbidity plumes in Tampa Bay, Florida, produced during ship-channel dredging operations from February 1977 to August 1978, were monitored in order to document plume appearance and water quality, evaluate plume influence on the characteristics of Tampa Bay water, and provide a data base for comparison with other areas that have similar sediment, dredge, placement, containment, and tide conditions. The plumes investigated originated from the operation of one hopper dredge and three cutterhead-pipeline dredges. Composition of bottom sediment was found to vary from 85 percent sand and shell fragments to 60 percent silt and clay. Placement methods for dredged sediment included beach nourishment, stationary submerged discharge, oscillating surface discharge, and construction of emergent dikes. Tidal currents ranged from slack water to flow velocities of 0.60 meter per second. Plumes were monitored simultaneously by (1) oblique and vertical 35-millimeter aerial photography and (2) water-quality sampling to determine water clarity and concentrations of nutrients, metals, pesticides, and industrial compounds. Forty-nine photographs depict plumes ranging in length from a few tens of meters to several kilometers and ranging in turbidity level from <10 to 200,000 nephelometric turbidity units. The most visible turbidity plumes were produced by surface discharge of material with high sand content into unconfined placement areas during times of strong tidal currents. The least visible turbidity plumes were produced by discharge of material with high silt and clay content into areas enclosed by floating turbidity barriers during times of weak tidal currents. Beach nourishment from hopper-dredge unloading operations also produced plumes of low visibility. Primary turbidity plumes were produced directly by dredging and placement operations; secondary plumes were produced indirectly by resuspension of previously deposited material. Secondary plumes were formed both by erosion, in

Diagnostics of Laser Produced Plume Under Carbon Nanotube Growth Conditions

NASA Technical Reports Server (NTRS)

Arepalli, Sivaram; Nikolaev, Pavel; Holmes, William; Scott, Carl D.

1999-01-01

This paper presents diagnostic data obtained from the plume of a graphite composite target during carbon nanotube production by the double-pulse laser oven method. The insitu emission spectrum (300 to 650 nm) is recorded at different locations upstream of the target and at different delay times from the lasers (IR and green). Spectral features are identified as emissions from C2 (Swan System: a (sup 3)pi(sub g) - delta (sup 3)pi(sub u) and C3 (Comet Head System: A (sup 1)pi(sub u) - chi (sup 1)sigma(sub u) (sup +). Experimental spectra are compared with computed spectra to estimate vibrational temperatures of excited state C2 in the range of 2500 to 4000 kappa The temporal evolution of the 510 nm band of C2 is monitored for two target positions in various locations which shows confinement of the plume in the inner tube and increase in plume velocity with temperature. The excitation spectra of C2 are obtained by using a dye laser to pump the (0,1) transition of the Swan System and collecting the Laser Induced Fluorescence signal from C2 These are used to obtain "ground-state" rotational and vibrational temperatures which are close to the oven temperature. Images of the plume are also collected and are compared with the spectral measurements.

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.

FOOTPRINT: A Screening Model for Estimating the Area of a Plume Produced From Gasoline Containing Ethanol

EPA Pesticide Factsheets

FOOTPRINT is a screening model used to estimate the length and surface area of benzene, toluene, ethylbenzene, and xylene (BTEX) plumes in groundwater, produced from a gasoline spill that contains ethanol.

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

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.

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.

Footprint (A Screening Model for Estimating the Area of a Plume Produced from Gasoline Containing Ethanol

EPA Science Inventory

FOOTPRINT is a simple and user-friendly screening model to estimate the length and surface area of BTEX plumes in ground water produced from a spill of gasoline that contains ethanol. Ethanol has a potential negative impact on the natural biodegradation of BTEX compounds in groun...

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.

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.

Moisture driven convection on Jupiter: A mechanism to produce the equatorial plumes

NASA Technical Reports Server (NTRS)

Stoker, C.

1986-01-01

Possible roles are explored for moist convection in the production of bright plume features in the Jupiter atmosphere. The features have been observed at least since 1881. A one-dimensional model is developed for a Jovian cloud and the conditions necessary for convection to occur on Jupiter are defined. The model is used to predict the vertical velocity and maximum altitude of moist clouds that are convected over a vertical extent of 100, 10 and 1 km. Convection within the ammonia layer would not produce sufficient buoyancy to sublime from the rising air parcel. Water rising from the 5 bar to 1 bar level could carry enough ammonia to the cooler region to form plume anvils in the stable layer above 700 mbar. If unpolluted during the convection, the water could be the source of high altitude haze above the entire equatorial zone.

Generation Of Functional Insulin-Producing Cells In The Gut By Foxo1 Ablation

PubMed Central

Talchai, Chutima; Xuan, Shouhong; Kitamura, Tadahiro; DePinho, Ronald A.; Accili, Domenico

2012-01-01

Restoration of regulated insulin secretion is the ultimate goal of type 1 diabetes therapy. Here we show that, surprisingly, somatic ablation of Foxo1 in Neurog3+ enteroendocrine progenitor cells gives rise to gut insulin-positive cells (Ins+) that express markers of mature β-cells, and secrete bioactive insulin as well as C-peptide in response to glucose and sulfonylureas. Lineage tracing experiments show that gut Ins+ cells arise cell-autonomously from Foxo1-deficient cells. Inducible Foxo1 ablation in adult mice also results in the generation of gut Ins+ cells. Following ablation by the β-cell toxin, streptozotocin, gut Ins+ cells regenerate and produce insulin, reversing hyperglycemia in mice. The data indicate that Neurog3+ enteroendocrine progenitors require active Foxo1 to prevent differentiation into Ins+ cells. Foxo1 ablation in gut epithelium may provide an approach to restore insulin production in type 1 diabetes. PMID:22406641

Targeted ablation of cholinergic interneurons in the dorsolateral striatum produces behavioral manifestations of Tourette syndrome

PubMed Central

Xu, Meiyu; Kobets, Andrew; Du, Jung-Chieh; Lennington, Jessica; Li, Lina; Banasr, Mounira; Duman, Ronald S.; Vaccarino, Flora M.; DiLeone, Ralph J.; Pittenger, Christopher

2015-01-01

Gilles de la Tourette syndrome (TS) is characterized by tics, which are transiently worsened by stress, acute administration of dopaminergic drugs, and by subtle deficits in motor coordination and sensorimotor gating. It represents the most severe end of a spectrum of tic disorders that, in aggregate, affect ∼5% of the population. Available treatments are frequently inadequate, and the pathophysiology is poorly understood. Postmortem studies have revealed a reduction in specific striatal interneurons, including the large cholinergic interneurons, in severe disease. We tested the hypothesis that this deficit is sufficient to produce aspects of the phenomenology of TS, using a strategy for targeted, specific cell ablation in mice. We achieved ∼50% ablation of the cholinergic interneurons of the striatum, recapitulating the deficit observed in patients postmortem, without any effect on GABAergic markers or on parvalbumin-expressing fast-spiking interneurons. Interneuron ablation in the dorsolateral striatum (DLS), corresponding roughly to the human putamen, led to tic-like stereotypies after either acute stress or d-amphetamine challenge; ablation in the dorsomedial striatum, in contrast, did not. DLS interneuron ablation also led to a deficit in coordination on the rotorod, but not to any abnormalities in prepulse inhibition, a measure of sensorimotor gating. These results support the causal sufficiency of cholinergic interneuron deficits in the DLS to produce some, but not all, of the characteristic symptoms of TS. PMID:25561540

Diagnostics of Carbon Nanotube Formation in a Laser Produced Plume: Spectroscopic in situ nanotube detection using spectral absorption and surface temperature measurements by black body emission

NASA Technical Reports Server (NTRS)

DeBoer, Gary D.

2005-01-01

Carbon nanotubes hold great promise for material advancements in the areas of composites and electronics. The advancement of research in these areas is dependent upon the availability of carbon nanotubes to a broad spectrum of academic and industrial researchers. Although there has been much progress made in reducing the costs of carbon nanotubes and increasing the quality and purity of the products, an increase in demand for still less expensive and specific nanotubes types has also grown. This summer's work has involved two experiments that have been designed to further the understanding of the dynamics and chemical mechanisms of carbon nanotube formation. It is expected that a better understanding of the process of formation of nanotubes will aid current production designs and stimulate ideas for future production designs increasing the quantity, quality, and production control of carbon nanotubes. The first experiment involved the measurement of surface temperature of the target as a function of time with respect to the ablation lasers. A peak surface temperature of 5000 K was determined from spectral analysis of black body emission from the target surface. The surface temperature as a function of various changes in operating parameters was also obtained. This data is expected to aid the modeling of ablation and plume dynamics. The second experiment involved a time and spatial measurement of the spectrally resolved absorbance of the laser produced plume. This experiment explored the possibility of developing absorbance and fluorescence to detect carbon nanotubes during production. To attain control over the production of nanotubes with specific properties and reduce costs, a real time in situ diagnostics method would be very beneficial. Results from this summer's work indicate that detection of nanotubes during production may possibly be used for production feed back control.

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.

Self-limiting and complete oxidation of silicon nanostructures produced by laser ablation in water

SciTech Connect

Vaccaro, L.; Messina, F.; Camarda, P.

2016-07-14

Oxidized Silicon nanomaterials produced by 1064 nm pulsed laser ablation in deionized water are investigated. High-resolution transmission electron microscopy coupled with energy dispersive X-ray spectroscopy allows to characterize the structural and chemical properties at a sub-nanometric scale. This analysis clarifies that laser ablation induces both self-limiting and complete oxidation processes which produce polycrystalline Si surrounded by a layer of SiO{sub 2} and amorphous fully oxidized SiO{sub 2}, respectively. These nanostructures exhibit a composite luminescence spectrum which is investigated by time-resolved spectroscopy with a tunable laser excitation. The origin of the observed luminescence bands agrees with the two structural typologies: Si nanocrystalsmore » emit a μs-decaying red band; defects of SiO{sub 2} give rise to a ns-decaying UV band and two overlapping blue bands with lifetime in the ns and ms timescale.« less

Nano-machining of biosensor electrodes through gold nanoparticles deposition produced by femtosecond laser ablation

NASA Astrophysics Data System (ADS)

Della Ventura, B.; Funari, R.; Anoop, K. K.; Amoruso, S.; Ausanio, G.; Gesuele, F.; Velotta, R.; Altucci, C.

2015-06-01

We report an application of femtosecond laser ablation to improve the sensitivity of biosensors based on a quartz crystal microbalance device. The nanoparticles produced by irradiating a gold target with 527-nm, 300-fs laser pulses, in high vacuum, are directly deposited on the quartz crystal microbalance electrode. Different gold electrodes are fabricated by varying the deposition time, thus addressing how the nanoparticles surface coverage influences the sensor response. The modified biosensor is tested by weighting immobilized IgG antibody from goat and its analyte (IgG from mouse), and the results are compared with a standard electrode. A substantial increase of biosensor sensitivity is achieved, thus demonstrating that femtosecond laser ablation and deposition is a viable physical method to improve the biosensor sensitivity by means of nanostructured electrodes.

Low work function surface layers produced by laser ablation using short-wavelength photons

DOEpatents

Balooch, Mehdi; Dinh, Long N.; Siekhaus, Wigbert J.

2000-01-01

Short-wavelength photons are used to ablate material from a low work function target onto a suitable substrate. The short-wavelength photons are at or below visible wavelength. The elemental composition of the deposit is controlled by the composition of the target and the gaseous environment in which the ablation process is performed. The process is carried out in a deposition chamber to which a short-wavelength laser is mounted and which includes a substrate holder which can be rotated, tilted, heated, or cooled. The target material is mounted onto a holder that spins the target during laser ablation. In addition, the deposition chamber is provided with a vacuum pump, an external gas supply with atomizer and radical generator, a gas generator for producing a flow of molecules on the substrate, and a substrate cleaning device, such as an ion gun. The substrate can be rotated and tilted, for example, whereby only the tip of an emitter can be coated with a low work function material.

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.

Alignments of volcanic features in the southern hemisphere of Mars produced by migrating mantle plumes

NASA Astrophysics Data System (ADS)

Leone, Giovanni

2016-01-01

Mars shows alignments of volcanic landforms in its southern hemisphere, starting from the equatorial regions and converging towards the South Pole, and visible at global scale. These composite alignments of volcanoes, calderas, shields, vents, heads of valley networks and massifs between the equatorial regions and the southern polar region define twelve different lines, fitted by rhumb lines (loxodromes), that I propose to be the traces of mantle plumes. The morphology of the volcanic centres changes along some of the alignments suggesting different processes of magma emplacement and eruptive style. The diameters of the volcanic centres and of the volcanic provinces are largest at Tharsis and Elysium, directly proportional to the number of alignments starting from them. A minor presence of unaligned volcanic features is observed on the northern lowlands and on the highlands outside the 12 major alignments. The heads of channels commonly interpreted as fluvial valleys are aligned with the other volcanic centres; unaltered olivine is present along their bed-floors, raising severe doubts as to their aqueous origin. Several hypotheses have tried to explain the formation of Tharsis with the migration of a single mantle plume under the Martian lithosphere, but the discovery of twelve alignments, six starting from Tharsis, favours the hypothesis of several mantle plumes as predicted by the model of the Southern Polar Giant Impact (SPGI) and provides a new view on the formation of the volcanic provinces of Mars.

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.

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.

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.

Analysis of Indium Tin Oxide Film Using Argon Fluroide (ArF) Laser-Excited Atomic Fluorescence of Ablated Plumes.

PubMed

Ho, Sut Kam; Garcia, Dario Machado

2017-04-01

A two-pulse laser-excited atomic fluorescence (LEAF) technique at 193 nm wavelength was applied to the analysis of indium tin oxide (ITO) layer on polyethylene terephthalate (PET) film. Fluorescence emissions from analytes were induced from plumes generated by first laser pulse. Using this approach, non-selective LEAF can be accomplished for simultaneous multi-element analysis and it overcomes the handicap of strict requirement for laser excitation wavelength. In this study, experimental conditions including laser fluences, times for gating and time delay between pulses were optimized to reveal high sensitivity with minimal sample destruction and penetration. With weak laser fluences of 100 and 125 mJ/cm 2 for 355 and 193 nm pulses, detection limits were estimated to be 0.10% and 0.43% for Sn and In, respectively. In addition, the relation between fluorescence emissions and number of laser shots was investigated; reproducible results were obtained for Sn and In. It shows the feasibility of depth profiling by this technique. Morphologies of samples were characterized at various laser fluences and number of shots to examine the accurate penetration. Images of craters were also investigated using scanning electron microscopy (SEM). The results demonstrate the imperceptible destructiveness of film after laser shot. With such weak laser fluences and minimal destructiveness, this LEAF technique is suitable for thin-film analysis.

Thermal Shock and Ablation Behavior of Tungsten Nozzle Produced by Plasma Spray Forming and Hot Isostatic Pressing

NASA Astrophysics Data System (ADS)

Wang, Y. M.; Xiong, X.; Zhao, Z. W.; Xie, L.; Min, X. B.; Yan, J. H.; Xia, G. M.; Zheng, F.

2015-08-01

Tungsten nozzle was produced by plasma spray forming (PSF, relative density of 86 ± 2%) followed by hot isostatic pressing (HIPing, 97 ± 2%) at 2000 °C and 180 MPa for 180 min. Scanning electron microscope, x-ray diffractometer, Archimedes method, Vickers hardness, and tensile tests have been employed to study microstructure, phase composition, density, micro-hardness, and mechanical properties of the parts. Resistance of thermal shock and ablation behavior of W nozzle were investigated by hot-firing test on solid rocket motor (SRM). Comparing with PSF nozzle, less damage was observed for HIPed sample after SRM test. Linear ablation rate of nozzle made by PSF was (0.120 ± 0.048) mm/s, while that after HIPing reduced to (0.0075 ± 0.0025) mm/s. Three types of ablation mechanisms including mechanical erosion, thermophysical erosion, and thermochemical ablation took place during hot-firing test. The order of degree of ablation was nozzle throat > convergence > dilation inside W nozzle.

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

Iron isotope composition of particles produced by UV-femtosecond laser ablation of natural oxides, sulfides, and carbonates.

PubMed

d'Abzac, Francois-Xavier; Beard, Brian L; Czaja, Andrew D; Konishi, Hiromi; Schauer, James J; Johnson, Clark M

2013-12-17

The need for femtosecond laser ablation (fs-LA) systems coupled to MC-ICP-MS to accurately perform in situ stable isotope analyses remains an open question, because of the lack of knowledge concerning ablation-related isotopic fractionation in this regime. We report the first iron isotope analysis of size-resolved, laser-induced particles of natural magnetite, siderite, pyrrhotite, and pyrite, collected through cascade impaction, followed by analysis by solution nebulization MC-ICP-MS, as well as imaging using electron microscopy. Iron mass distributions are independent of mineralogy, and particle morphology includes both spheres and agglomerates for all ablated phases. X-ray spectroscopy shows elemental fractionation in siderite (C-rich agglomerates) and pyrrhotite/pyrite (S-rich spheres). We find an increase in (56)Fe/(54)Fe ratios of +2‰, +1.2‰, and +0.8‰ with increasing particle size for magnetite, siderite, and pyrrhotite, respectively. Fe isotope differences in size-sorted aerosols from pyrite ablation are not analytically resolvable. Experimental data are discussed using models of particles generation by Hergenröder and elemental/isotopic fractionation by Richter. We interpret the isotopic fractionation to be related to the iron condensation time scale, dependent on its saturation in the gas phase, as a function of mineral composition. Despite the isotopic variations across aerosol size fractions, total aerosol composition, as calculated from mass balance, confirms that fs-LA produces a stoichiometric sampling in terms of isotopic composition. Specifically, both elemental and isotopic fractionation are produced by particle generation processes and not by femtosecond laser-matter interactions. These results provide critical insights into the analytical requirements for laser-ablation-based stable isotope measurements of high-precision and accuracy in geological samples, including the importance of quantitative aerosol transport to the ICP.

Effects of a static inhomogeneous magnetic field acting on a laser-produced carbon plasma plume

NASA Astrophysics Data System (ADS)

Favre, M.; Ruiz, H. M.; Bendixsen, L. S. Caballero; Reyes, S.; Veloso, F.; Wyndham, E.; Bhuyan, H.

2017-08-01

We present time- and space-resolved observations of the dynamics of a laser-produced carbon plasma, propagating in a sub-Tesla inhomogeneous magnetic field, with both, axial and radial field gradients. An Nd:YAG laser pulse, 340 mJ, 3.5 ns, at 1.06 μ m, with a fluence of 7 J/cm2, is used to generate the plasma from a solid graphite target, in vacuum. The magnetic field is produced using two coaxial sets of two NeFeB ring magnets, parallel to the laser target surface. The diagnostics include plasma imaging with 50 ns time resolution, spatially resolved optical emission spectroscopy and Faraday cup. Based on our observations, evidence of radial and axial plasma confinement due to magnetic field gradients is presented. Formation of C2 molecules, previously observed in the presence of a low pressure neutral gas background, and enhanced on-axis ion flux, are ascribed to finite Larmor radius effects and reduced radial transport due to the presence of the magnetic field.

High-speed observation of ZnO microspherical crystals produced by laser ablation (Conference Presentation)

NASA Astrophysics Data System (ADS)

Nakamura, Daisuke; Tasaki, Ryohei; Fujiwara, Yuki; Nagasaki, Fumiaki; Higashihata, Mitsuhiro; Ikenoue, Hiroshi; Okada, Tatsuo

2017-03-01

ZnO nano/microstructures have attracted much attention as building blocks for optoelectronic devices because of their high crystalline quality and unique structures. We have succeeded in synthesizing ZnO microspherical crystals by a simple atmospheric laser ablation method, and demonstrated ultraviolet whispering-gallery-mode lasing from the spheres. In the microsphere synthesis process, molten droplets formed into spherical shapes by surface tension, and crystalized during ejection from the ablation spot. In this study, we observed the generation of ZnO microspheres by high-speed camera. Now we are trying to control and manipulate the microspheres using a vortex beam.

Spectral diagnostics of a vapor-plasma plume produced during welding titanium with a high-power ytterbium fiber laser

NASA Astrophysics Data System (ADS)

Uspenskiy, S. A.; Petrovskiy, V. N.; Bykovskiy, D. P.; Mironov, V. D.; Prokopova, N. M.; Tret'yakov, E. V.

2015-03-01

This work is devoted to the research of welding plume during high power ytterbium fiber laser welding of a titanium alloy in the Ar shielding gas environment. High speed video observation of a vapor-plasma plume for visualization of processes occurring at laser welding was carried out. The coefficient of the inverse Bremsstrahlung absorption of laser radiation is calculated for a plasma welding plume by results of spectrometer researches. The conclusion deals with the impact of plasma on a high-power fiber laser radiation.

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.

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.

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.

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.

Influence of large intrahepatic blood vessels on the gross and histological characteristics of lesions produced by radiofrequency ablation in a pig liver model.

PubMed

Tamaki, Katsuyoshi; Shimizu, Ichiro; Oshio, Atsuo; Fukuno, Hiroshi; Inoue, Hiroshi; Tsutsui, Akemi; Shibata, Hiroshi; Sano, Nobuya; Ito, Susumu

2004-12-01

To determine whether the presence of large intrahepatic blood vessels (>/=3 mm) affect radiofrequency (RF)-induced coagulation necrosis, the gross and histological characteristics of RF-ablated areas proximal to or around vessels were examined in normal pig livers. An RF ablation treatment using a two-stepwise extension technique produced 12 lesions: six contained vessels (Group A), and the other six were localized around vessels (Group B). Gross examination revealed that the longest and shortest diameters of the ablated lesions were significantly larger in Group B than in Group A. In Group A, patent vessels contiguous to the lesion were present in a tongue-shaped area, whereas the lesions in Group B were spherical. Staining with nicotinamide adenine dinucleotide diaphorase was negative within the ablated area; but, if vessels were present in the ablated area, the cells around the vessels in an opposite direction to the ablation were stained blue. Roll-off can be achieved with 100% cellular destruction within a lesion that does not contain large vessels. The ablated area was decreased in lesions that contained large vessels, suggesting that the presence of large vessels in the ablated area further increases the cooling effect and may require repeated RF ablation treatment to achieve complete coagulation necrosis.

Low- and high-order harmonic generation in the extended plasmas produced by laser ablation of zinc and manganese targets

SciTech Connect

Ganeev, R. A., E-mail: rashid-ganeev@mail.ru; Physical Department, Voronezh State University, Voronezh 394006; Baba, M.

The systematic studies of the harmonic generation of ultrashort laser pulses in the 5-mm-long Zn and Mn plasmas (i.e., application of nanosecond, picosecond, and femtosecond pulses for ablation, comparison of harmonic generation from atomic, ionic, and cluster-contained species of plasma, variation of plasma length, two-color pump of plasmas, etc.) are presented. The conversion efficiency of the 11th–19th harmonics generated in the Zn plasma was ∼5 × 10{sup −5}. The role of the ionic resonances of Zn near the 9th and 10th harmonics on the enhancement of harmonics is discussed. The enhancement of harmonics was also analyzed using the two-color pump of extendedmore » plasmas, which showed similar intensities of the odd and even harmonics along the whole range of generation. The harmonics up to the 107th order were demonstrated in the case of manganese plasma. The comparison of harmonic generation in the 5-mm-long and commonly used short (≤0.5 mm) plasma plumes showed the advanced properties of extended media.« less

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.

Biocompatible inorganic fullerene-like molybdenum disulfide nanoparticles produced by pulsed laser ablation in water.

PubMed

Wu, Haihua; Yang, Rong; Song, Baomin; Han, Qiusen; Li, Jingying; Zhang, Ying; Fang, Yan; Tenne, Reshef; Wang, Chen

2011-02-22

We report on the synthesis of inorganic fullerene-like molybdenum disulfide (MoS(2)) nanoparticles by pulsed laser ablation (PLA) in water. The final products were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and resonance Raman spectroscopy, etc. Cell viability studies show that the as-prepared MoS(2) nanoparticles have good solubility and biocompatibility, which may show a great potential in various biomedical applications. It is shown that the technique of PLA in water also provides a green and convenient method to synthesize novel nanomaterials, especially for biocompatible nanomaterials.

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.

B cell depletion therapy ameliorates autoimmune disease through ablation of IL-6–producing B cells

PubMed Central

Shen, Ping; Brown, Sheila; Lampropoulou, Vicky; Roch, Toralf; Lawrie, Sarah; Fan, Boli; O’Connor, Richard A.; Anderton, Stephen M.; Bar-Or, Amit; Fillatreau, Simon; Gray, David

2012-01-01

B cells have paradoxical roles in autoimmunity, exerting both pathogenic and protective effects. Pathogenesis may be antibody independent, as B cell depletion therapy (BCDT) leads to amelioration of disease irrespective of autoantibody ablation. However, the mechanisms of pathogenesis are poorly understood. We demonstrate that BCDT alleviates central nervous system autoimmunity through ablation of IL-6–secreting pathogenic B cells. B cells from mice with experimental autoimmune encephalomyelitis (EAE) secreted elevated levels of IL-6 compared with B cells from naive controls, and mice with a B cell–specific IL-6 deficiency showed less severe disease than mice with wild-type B cells. Moreover, BCDT ameliorated EAE only in mice with IL-6–sufficient B cells. This mechanism of pathogenesis may also operate in multiple sclerosis (MS) because B cells from MS patients produced more IL-6 than B cells from healthy controls, and this abnormality was normalized with B cell reconstitution after Rituximab treatment. This suggests that BCDT improved disease progression, at least partly, by eliminating IL-6–producing B cells in MS patients. Taking these data together, we conclude that IL-6 secretion is a major mechanism of B cell–driven pathogenesis in T cell–mediated autoimmune disease such as EAE and MS. PMID:22547654

Experimental investigation of the effects of different liquid environments on the graphene oxide produced by laser ablation method

NASA Astrophysics Data System (ADS)

Ghavidel, Elham; Sari, Amir Hossein; Dorranian, Davoud

2018-07-01

In this work, the effects of liquid environments on the characteristics and optical properties of carbon nanostructures - in particular, Graphene Oxide (GO) - prepared by pulsed laser ablation were studied experimentally. The second harmonic beam of a Q-switched Nd:YAG laser of 532 nm wavelength at 6 ns pulse width and 0.7 J/cm2 fluence was employed to irradiate the graphite target in liquid nitrogen, deionized water, and 0.01 M CTAB solution under the same initial experimental conditions. Produced nanostructures were characterized by Raman scattering spectrum, FE-SEM and TEM images, Photoluminescence, and UV-Vis-NIR spectrum. TEM and FE-SEM images show sheet-like morphology with few square micrometer area graphenes in all samples. Raman and UV-Vis-NIR analyses show that graphene is oxidized due to the presence of oxygen molecules in ablation environment. Results demonstrate that the graphene nanosheets produced in deionized water are multilayer, contains the largest sp2 domain size, the least defects and the lowest possibility of aggregation.

Ultra-pure, water-dispersed Au nanoparticles produced by femtosecond laser ablation and fragmentation

PubMed Central

Kubiliūtė, Reda; Maximova, Ksenia A; Lajevardipour, Alireza; Yong, Jiawey; Hartley, Jennifer S; Mohsin, Abu SM; Blandin, Pierre; Chon, James WM; Sentis, Marc; Stoddart, Paul R; Kabashin, Andrei; Rotomskis, Ričardas; Clayton, Andrew HA; Juodkazis, Saulius

2013-01-01

Aqueous solutions of ultra-pure gold nanoparticles have been prepared by methods of femtosecond laser ablation from a solid target and fragmentation from already formed colloids. Despite the absence of protecting ligands, the solutions could be (1) fairly stable and poly size-dispersed; or (2) very stable and monodispersed, for the two fabrication modalities, respectively. Fluorescence quenching behavior and its intricacies were revealed by fluorescence lifetime imaging microscopy in rhodamine 6G water solution. We show that surface-enhanced Raman scattering of rhodamine 6G on gold nanoparticles can be detected with high fidelity down to micromolar concentrations using the nanoparticles. Application potential of pure gold nanoparticles with polydispersed and nearly monodispersed size distributions are discussed. PMID:23888114

3D plasmonic transducer based on gold nanoparticles produced by laser ablation on silica nanowires

NASA Astrophysics Data System (ADS)

Gontad, F.; Caricato, A. P.; Manera, M. G.; Colombelli, A.; Resta, V.; Taurino, A.; Cesaria, M.; Leo, C.; Convertino, A.; Klini, A.; Perrone, A.; Rella, R.; Martino, M.

2016-05-01

Silica two-dimensional substrates and nanowires (NWs) forests have been successfully decorated with Au nanoparticles (NPs) through laser ablation by using a pulsed ArF excimer laser, for sensor applications. A uniform coverage of both substrate surfaces with NPs has been achieved controlling the number of laser pulses. The annealing of the as-deposited particles resulted in a uniform well-defined distribution of spherical NPs with an increased average diameter up to 25 nm. The deposited samples on silica NWs forest present a very good plasmonic resonance which resulted to be very sensitive to the changes of the environment (ethanol/water solutions with increasing concentration of ethanol) allowing the detection of changes on the second decimal digit of the refractive index, demonstrating its potentiality for further biosensing functionalities.

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.

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.

Langmuir probe measurements and mass spectrometry of plasma plumes generated by laser ablation of La0.4Ca0.6MnO3

NASA Astrophysics Data System (ADS)

Chen, Jikun; Lunney, James G.; Lippert, Thomas; Ojeda-G-P, Alejandro; Stender, Dieter; Schneider, Christof W.; Wokaun, Alexander

2014-08-01

The plasma formed in vacuum by UV nanosecond laser ablation of La0.4Ca0.6MnO3 in the fluence range of 0.8 to 1.9 J cm-2 using both Langmuir probe analysis and energy-resolved mass spectrometry has been studied. Mass spectrometry shows that the main positive ion species are Ca+, Mn+, La+, and LaO+. The Ca+ and Mn+ energy distributions are quite broad and lie in the 0-100 eV region, with the average energies increasing with laser fluence. In contrast, the La+ and LaO+ distributions are strongly peaked around 10 eV. The net time-of-arrival signal derived from the measured positive ion energy distributions is broadly consistent with the positive ion signal measured by the Langmuir probe. We also detected a significant number of O- ions with energies in the range of 0 to 10 eV. The Langmuir probe was also used to measure the temporal variation of the electron density and temperature at 6 cm from the ablation target. In the period when O- ions are found at this position, the plasma conditions are consistent with those required for significant negative oxygen ion formation, as revealed by studies on radio frequency excited oxygen plasma.

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

Silver and gold nanoparticles produced by pulsed laser ablation in liquid to investigate their interaction with Ubiquitin

NASA Astrophysics Data System (ADS)

Dell'Aglio, M.; Mangini, V.; Valenza, G.; De Pascale, O.; De Stradis, A.; Natile, G.; Arnesano, F.; De Giacomo, A.

2016-06-01

The interaction of nanoparticles (NPs) with proteins is widely investigated since it can be a key issue in addressing the problem of nanotoxicity, particularly in the case of biological and medical applications. In this work, silver and gold nanoparticles (AgNPs and AuNPs) were produced in water by Pulsed Laser Ablation in Liquid (PLAL) and allowed to react with Ubiquitin (Ub) (a small human protein essential for degradative processes in cells). NPs produced by PLAL are completely free of undesired contaminants and do not require the use of stabilizers. We found that the NPs + Ub system behaves differently if the NPs are or are not treated with a stabilizer before performing the interaction with Ub, since the presence of capping agents modifies the surface reactivity of the metal-NPs. The surface plasmon resonance (SPR) absorption spectroscopy was employed to monitor the fast changes occurring in the NP colloidal solutions upon interaction with Ub. The results obtained by SPR were confirmed by TEM analysis. Therefore, when Ub interacts with bare NPs a rapid aggregation occurs and, at the same time, Ub undergoes an amyloid transition. Notably, the aggregation of AuNPs occurs at a much greater rate than that of analogous AgNPs and the Ub fibrils that are formed can be imaged by thioflavin T fluorescence.

Growth and structure of fullerene-like CNx thin films produced by pulsed laser ablation of graphite in nitrogen

NASA Astrophysics Data System (ADS)

Voevodin, A. A.; Jones, J. G.; Zabinski, J. S.; Czigany, Zs.; Hultman, L.

2002-11-01

The growth and structure of fullerene-like CNx films produced by laser ablation of graphite in low pressure nitrogen were investigated. Deposition conditions were selected based on investigations of CN and C2 concentration at the condensation surface, vibrational temperature of CN radicals, and kinetic energies of atomic and molecular species. Films were characterized with x-ray photoelectron spectroscopy, Raman spectroscopy, high-resolution transmission electron microscopy, nanoindentation, and stress analyses. The nitrogen content in CNx films directly depended on the concentration of CN radicals at the condensation surface. Formation of fullerene-like structures required a high vibrational temperature of these radicals, which was maximized at about 4 eV for depositions at 10 mTorr N2 and laser fluences of approx7 J/cm2. The presence of C2 had only a minor effect on film composition and structure. Optimization of plasma characteristics and a substrate temperature of 300 degC helped to produce about 1-mum-thick solid films of CNx (N/C ratioapproximately0.2-0.3) and pure carbon consisting of fullerene-like fragments and packages. In contrast to carbon films, fullerene-like CNx films exhibited a high elastic recovery of about 80% in using a Berkovich tip at 5 mN load and indentation depths up to 150 nm. Their elastic modulus was about 160 GPa measured from the unloading portion of an indentation curve, and about 250 GPa measured with a 40 Hz tip oscillation during nanoindentation tests. The difference was related to time dependent processes of shape restoration of fullerene-like fragments, and an analogy was made to the behavior of elastomer polymers. However, unlike elastomers, CNx film hardness was as high as 30 GPa, which was twice that of fullerene-like carbon films. The unusual combination of high elasticity and hardness of CNx films was explained by crosslinking of fullerene fragments induced by the incorporated nitrogen and stored compressive stress. The

Partial ablation of adult Drosophila insulin-producing neurons modulates glucose homeostasis and extends life span without insulin resistance.

PubMed

Haselton, Aaron; Sharmin, Effat; Schrader, Janel; Sah, Megha; Poon, Peter; Fridell, Yih-Woei C

2010-08-01

In Drosophila melanogaster (D. melanogaster), neurosecretory insulin-like peptide-producing cells (IPCs), analogous to mammalian pancreatic beta cells are involved in glucose homeostasis. Extending those findings, we have developed in the adult fly an oral glucose tolerance test and demonstrated that IPCs indeed are responsible for executing an acute glucose clearance response. To further develop D. melanogaster as a relevant system for studying age-associated metabolic disorders, we set out to determine the impact of adult-specific partial ablation of IPCs (IPC knockdown) on insulin-like peptide (ILP) action, metabolic outcomes and longevity. Interestingly, while IPC knockdown flies are hyperglycemic and glucose intolerant, these flies remain insulin sensitive as measured by peripheral glucose disposal upon insulin injection and serine phosphorylation of a key insulin-signaling molecule, Akt. Significant increases in stored glycogen and triglyceride levels as well as an elevated level of circulating lipid measured in adult IPC knockdown flies suggest profound modulation in energy metabolism. Additional physiological outcomes measured in those flies include increased resistance to starvation and impaired female fecundity. Finally, increased life span and decreased mortality rates measured in IPC knockdown flies demonstrate that it is possible to modulate ILP action in adult flies to achieve life span extension without insulin resistance. Taken together, we have established and validated an invertebrate genetic system to further investigate insulin action, metabolic homeostasis and regulation of aging regulated by adult IPCs.

2D Time-lapse Resistivity Monitoring of an Organic Produced Gas Plume in a Landfill using ERT.

NASA Astrophysics Data System (ADS)

Amaral, N. D.; Mendonça, C. A.; Doherty, R.

2014-12-01

This project has the objective to study a landfill located on the margins of Tietê River, in São Paulo, Brazil, using the electroresistivity tomography method (ERT). Due to huge organic matter concentrations in the São Paulo Basin quaternary sediments, there is subsurface depth related biogas accumulation (CH4 and CO2), induced by anaerobic degradation of the organic matter. 2D resistivity sections were obtained from a test area since March 2012, a total of 7 databases, being the last one dated from October 2013. The studied line has the length of 56m, the electrode interval is of 2m. In addition, there are two boreholes along the line (one with 3 electrodes and the other one with 2) in order to improve data quality and precision. The boreholes also have a multi-level sampling system that indicates the fluid (gas or water) presence in relation to depth. With our results it was possible to map the gas plume position and its area of extension in the sections as it is a positive resistivity anomaly, with the gas level having approximately 5m depth. With the time-lapse analysis (Matlab script) between the obtained 2D resistivity sections from the site, it was possible to map how the biogas volume and position change in the landfill in relation to time. Our preliminary results show a preferential gas pathway through the subsurface studied area. A consistent relation between the gas depth and obtained microbiological data from archea and bacteria population was also observed.

Seismic images of the transition zone: is Hawaiian volcanism produced by a secondary plume from the top of the lower mantle?

NASA Astrophysics Data System (ADS)

Cao, Q.; van der Hilst, R. D.; Shim, S.; De Hoop, M. V.

2011-12-01

The Hawaiian hotspot is often attributed to hot material rising from depth in the mantle, but efforts to detect a thermal plume seismically have been inconclusive. Most tomographic models reveal anomalously low wavespeeds beneath Hawaii, but the depth extent of this structure is not well known. S or P data used in traveltime inversions are associated with steep rays to distant sources, which degrades depth resolution, and surface wave dispersion does not have sufficient sensitivity at the depths of interest. To investigate pertinent thermal anomalies we mapped depth variations of upper mantle discontinuities using precursors of the surface-reflected SS wave. Instead of stacking the data over geographical bins, which leads to averaging of topography and hence loss of spatial resolution, we used a generalized Radon transform (GRT) to detect and map localized elasticity contrasts in the transition zone (Cao et al., PEPI, 2010). We apply the GRT to produce 3D image volumes beneath a large area of the Pacific Ocean, including Hawaii and the Hawaii-Emperor seamount chain (Cao et al., Science, 2011). The 3D image volumes reveal laterally continuous interfaces near 410 and 660 km depths, that is, the traditional boundaries of the transition zone, but also suggest (perhaps intermittent) scatter horizons near 300-350, 520-550, and 800-1000 km depth. The upper mantle appears generally hot beneath Hawaii, but the most conspicuous topographic (and probably thermal) anomalies are found west of Hawaii. The GRT images reveal a 800 km wide uplift of the 660 discontinuity just west of Hawaii, but there is no evidence for a corresponding localized depression of the 410 discontinuity. This expression of the 410 and 660 km topographies is consistent with some existed geodynamical modeling results, in which a deep-rooted mantle plume impinging on the transition zone, creating a broad pond of hot material underneath endothermic phase change at 660 km depth, and with secondary plumes

Nanoparticle Over Mirror plasmonic structures prepared with use of Au colloid produced by laser ablation in water

NASA Astrophysics Data System (ADS)

Sawczak, Mirosław; Zyskowski, Marcin; Karczewski, Jakub; Atanasov, Petar A.; Nedyalkov, Nikolay N.; Nikov, Rumen G.; Stankova, Nadya A.; Śliwiński, Gerard

2016-01-01

Recently, an intensive research is carried out on plasmonic structures due to their potential application in many areas such as sensing, light harvesting and energy conversion and storage. In particular, a growing interest is observed in the Nanoparticle Over Mirror (NOM) structures for which the lithography and surface chemical functionalization represent the most popular production routes1. However, the application of those techniques is limited by the low efficacy, process complexity and chemical contamination of nanoparticles (NP). In this work, we report the contamination-free and low cost fabrication method of NOMs based on wet coating and ultrasonic-assisted nanocolloid drying process. The glass plates covered with magnetron sputtered 100 nm thick Au film and subsequently with Al2O3 layers (6 - 36 nm) by means of pulsed laser deposition are used as substrates. Au NPs are produced in the form of colloidal suspension by means of laser ablation in water using the 1064 nm, 6 ns Nd:YAG laser. The NOM synthesis is finalized by imposing of the Au NP suspension onto the as prepared Au-Al2O3/glass substrates and dried. To avoid NP agglomeration, the wet coated substrates are sonicated using 20W, 20 kHz ultrasound generator. SEM inspection of the obtained NOM structures confirms the positive sonication effect, i.e. the presence of agglomerate-free, homogenous layers. These consist of NPs (36 nm average diameter) which are characterized by the resonance absorption band at 528 nm. For NOM structures the UV-vis spectra reveal increased infrared activity and peak shift in agreement with theoretical modeling2. The NOM structure characterization is completed by analysis of the SEM and profilometry measurement results.

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.

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.

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.

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

SciTech Connect

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

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

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.

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.

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

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...

Nanotechnology combined therapy: tyrosine kinase-bound gold nanorod and laser thermal ablation produce a synergistic higher treatment response of renal cell carcinoma in a murine model.

PubMed

Liu, James; Abshire, Caleb; Carry, Connor; Sholl, Andrew B; Mandava, Sree Harsha; Datta, Amrita; Ranjan, Manish; Callaghan, Cameron; Peralta, Donna V; Williams, Kristen S; Lai, Weil R; Abdel-Mageed, Asim B; Tarr, Matthew; Lee, Benjamin R

2017-02-01

To investigate tyrosine kinase inhibitors (TKI) and gold nanorods (AuNRs) paired with photothermal ablation in a human metastatic clear cell renal cell carcinoma (RCC) mouse model. Nanoparticles have been successful as a platform for targeted drug delivery in the treatment of urological cancers. Likewise, the use of nanoparticles in photothermal tumour ablation, although early in its development, has provided promising results. Our previous in vitro studies of nanoparticles loaded with both TKI and AuNRs and activated with photothermal ablation have shown significant synergistic cell kill greater than each individual arm alone. This study is a translation of our initial findings to an in vivo model. Immunologically naïve nude mice (athymic nude-Foxn1 nu ) were injected subcutaneously bilaterally in both flanks (n = 36) with 2.5 × 10 6 cells of a human metastatic renal cell carcinoma cell line (RCC 786-O). Subcutaneous xenograft tumours developed into 1-cm palpable nodules. AuNRs encapsulated in human serum albumin protein (HSA) nanoparticles were synthesised with or without a TKI and injected directly into the tumour nodule. Irradiation was administered with an 808-nm light-emitting diode laser for 6 min. Mice were humanely killed 14 days after irradiation; tumours were excised, formalin fixed, paraffin embedded, and evaluated for size and the percentage of necrosis by a genitourinary pathologist. The untreated contralateral flank tumours were used as controls. In mice that did not receive irradiation, TKI alone yielded 4.2% tumour necrosis on the injected side and administration of HSA-AuNR-TKI alone yielded 11.1% necrosis. In the laser-ablation models, laser ablation alone yielded 62% necrosis and when paired with HSA-AuNR there was 63.4% necrosis. The combination of laser irradiation and HSA-AuNR-TKI had cell kill rate of 100%. In the absence of laser irradiation, TKI treatment alone or when delivered via nanoparticles produced moderate necrosis. Irradiation

Modeling of Interactions of Ablated Plumes

DTIC Science & Technology

2008-02-01

code was tested and verified using the Sedov-Taylor explosion problem 24. The grid 300 x 300 is used so as the single code run takes 30 minutes in a...still air and b) temperature contours along with the vector field for 20 km at t-10ps. 9 Final report AFOSR FA9550-07-1-0457 February 2008 0960014 09 C ow...ia Figue9FrainoIeodr shok wves a-)pesr otus0 )~22,bt4F,adetJ n d) het trnsferat te TPSw9PS 00 As 10 04 J. ’ Figure 9:Formation of secondary shock

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)

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.

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

SciTech Connect

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

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.

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.

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 ...

Optical spectroscopy of laser-produced plasmas for standoff isotopic analysis

SciTech Connect

Harilal, S. S.; Brumfield, B. E.; LaHaye, N. L.

This review article covers the present status of isotope detection through emission, absorption, and fluorescence spectroscopy of atoms and molecules in a laser-produced plasma formed from a solid sample. A description of the physics behind isotope shifts in atoms and molecules is presented, followed by the physics behind solid sampling of laser ablation plumes, optical methods for isotope measurements, the suitable physical conditions of laser-produced plasma plumes for isotopic analysis, and the current status. Lastly, concluding remarks will be made on the existing gaps between previous works in the literature and suggestions for future work.

Optical spectroscopy of laser-produced plasmas for standoff isotopic analysis

DOE PAGES

Harilal, S. S.; Brumfield, B. E.; LaHaye, N. L.; ...

2018-06-01

This review article covers the present status of isotope detection through emission, absorption, and fluorescence spectroscopy of atoms and molecules in a laser-produced plasma formed from a solid sample. A description of the physics behind isotope shifts in atoms and molecules is presented, followed by the physics behind solid sampling of laser ablation plumes, optical methods for isotope measurements, the suitable physical conditions of laser-produced plasma plumes for isotopic analysis, and the current status. Finally, concluding remarks will be made on the existing gaps between previous works in the literature and suggestions for future work.

Optical spectroscopy of laser-produced plasmas for standoff isotopic analysis

DOE PAGES

Harilal, S. S.; Brumfield, B. E.; LaHaye, N. L.; ...

2018-04-20

This review article covers the present status of isotope detection through emission, absorption, and fluorescence spectroscopy of atoms and molecules in a laser-produced plasma formed from a solid sample. A description of the physics behind isotope shifts in atoms and molecules is presented, followed by the physics behind solid sampling of laser ablation plumes, optical methods for isotope measurements, the suitable physical conditions of laser-produced plasma plumes for isotopic analysis, and the current status. Lastly, concluding remarks will be made on the existing gaps between previous works in the literature and suggestions for future work.

Optical spectroscopy of laser-produced plasmas for standoff isotopic analysis

SciTech Connect

Harilal, Sivanandan S.; Brumfield, Brian E.; LaHaye, Nicole L.

2018-04-20

This review article covers the present status of isotope detection through emission, absorption, and fluorescence spectroscopy of atoms and molecules in a laser-produced plasma formed from a solid sample. A description of the physics behind isotope shifts in atoms and molecules is presented, followed by the physics behind solid sampling of laser ablation plumes, optical methods for isotope measurements, the suitable physical conditions of laser-produced plasma plumes for isotopic analysis, and the current status. Finally, concluding remarks will be made on the existing gaps between previous works in the literature and suggestions for future work.

Optical spectroscopy of laser-produced plasmas for standoff isotopic analysis

SciTech Connect

Harilal, S. S.; Brumfield, B. E.; LaHaye, N. L.

This review article covers the present status of isotope detection through emission, absorption, and fluorescence spectroscopy of atoms and molecules in a laser-produced plasma formed from a solid sample. A description of the physics behind isotope shifts in atoms and molecules is presented, followed by the physics behind solid sampling of laser ablation plumes, optical methods for isotope measurements, the suitable physical conditions of laser-produced plasma plumes for isotopic analysis, and the current status. Finally, concluding remarks will be made on the existing gaps between previous works in the literature and suggestions for future work.

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.

Mobile Bay turbidity plume study

NASA Technical Reports Server (NTRS)

Crozier, G. F.

1976-01-01

Laboratory and field transmissometer studies on the effect of suspended particulate material upon the appearance of water are reported. Quantitative correlations were developed between remotely sensed image density, optical sea truth data, and actual sediment load. Evaluation of satellite image sea truth data for an offshore plume projects contours of transmissivity for two different tidal phases. Data clearly demonstrate the speed of change and movement of the optical plume for water patterns associated with the mouth of Mobile bay in which relatively clear Gulf of Mexico water enters the bay on the eastern side. Data show that wind stress in excess of 15 knots has a marked impact in producing suspended sediment loads.

Infrared spectra of M-η2-C2H2 and HMsbnd CCH produced in reactions of laser-ablated Fe and Os atoms with acetylene

NASA Astrophysics Data System (ADS)

Cho, Han-Gook; Andrews, Lester

2015-04-01

The π- and Csbnd H insertion products (M-η2-C2H2 and HMsbnd CCH) are identified in the matrix infrared spectra from reactions of laser-ablated Fe and Os atoms with acetylene isotopomers, but the vinylidene product (H2CCM) is not, in contrast to the recently studied Ru case. The π-complex is produced in deposition and annealing, and it converts to the insertion complex during photolysis. While the vinylidene product is energetically comparable with the two primary products, the energy barrier is considerably higher in contrast to the Ru case. The relatively short Csbnd C bonds of the π-complexes indicate weak back-donations from the group 8 metals to the acetylene π∗ orbitals. The highly bent structure of HOssbnd CCH evidently originates from the high d contributions to the Csbnd Os and Ossbnd H bonds. The C2v structures of the vinylidene products arise from the p-d π bonding between C and M.

Cytokine-induced killer cells co-cultured with dendritic cells loaded with the protein lysate produced by radiofrequency ablation induce a specific antitumor response

PubMed Central

SHAN, CHAN-CHAN; SHI, LIANG-RONG; DING, MEI-QIAN; ZHU, YI-BEI; LI, XIAO-DONG; XU, BIN; JIANG, JING-TING; WU, CHANG-PING

2015-01-01

Radiofrequency ablation (RFA) causes coagulative necrosis of tumor tissue and the production of local tumor protein debris. These fragments of tumor protein debris contain a large number of various antigens, which can stimulate a specific cellular immune response. In the present study, dendritic cells (DCs) were loaded with tumor protein lysate antigens that were produced in situ by RFA, and were used to treat murine colon carcinoma in combination with cytokine-induced killer (CIK) cells. Subsequent to the treatment of murine colon carcinoma by RFA, the in situ supernatant of tumor lysis was collected and the DCs were loaded with the lysate antigen to generate Ag-DCs. CIK cells induced from the spleen cells of mice were co-cultured with Ag-DCs to generate Ag-DC-CIK cells. The results revealed that the Ag-DC-CIK cells exhibited strong antitumor activity in vitro and in vivo. The morphology and immunophenotypes of these cells were determined using microscopy and flow cytometry, respectively. The cytotoxic activity of Ag-DC-CIK cells was determined using a CCK-8 assay. To establish a mouse model, mice were randomized into Ag-DC-CIK, DC-CIK, CIK and PBS control groups and monitored for tumor growth and survival time. ANOVA was used to compare the trends in the three groups for implanted tumor volumes. The log-rank test was used to compare the survival time. The present findings indicated that DCs loaded with the protein lysate antigens of tumors, produced in situ by RFA, combined with CIK cells may be a novel strategy for cancer treatment. PMID:25788999

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.

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.

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.

Enhanced dechlorination of m-DCB using iron@graphite/palladium (Fe@C/Pd) nanoparticles produced by pulsed laser ablation in liquid.

PubMed

Yu, Yiseul; Jung, Hyeon Jin; Je, Mingyu; Choi, Hyun Chul; Choi, Myong Yong

2016-07-01

In this work, the zero valent Fe (ZVI) and graphite-encapsulated Fe (Fe@C) nanoparticles (NPs) were easily and selectively prepared by a pulsed laser ablation (PLA) method in an aqueous sodium borohydride solution and ascorbic acid dissolved in methanol, respectively. Here, the Fe@C NPs were uniquely synthesized by PLA in methanol, where the solvent is used as both a carbon source for the graphitic layers and solvent, which is very unique. Furthermore, Pd NPs were loaded onto the surface of the Fe@C NPs to prepare bimetallic (Fe@C/Pd) NPs for the enhancement of the degradation efficiency of m-dichlorobenzene (m-DCB). The morphology, crystallinity, and surface composition of the prepared NPs were carefully characterized by high-resolution transmission electron microscopy (HRTEM), energy dispersive x-ray spectrometer (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The degradation rate of m-DCB using single (Fe and Pd) or bimetallic (Fe/Pd and Fe@C/Pd) NPs were compared by using gas chromatography. Among these NPs produced in this work, the Fe@C/Pd NPs with 1.71 wt % of Pd showed an excellent dechlorination efficiency for m-DCB with 100% degradation within 75 min. The graphitic layer on the Fe NPs played as not only an oxidation resistant for the Fe NPs to surroundings, but also a supporter of the Pd NPs for the enhanced degradation efficiency of m-DCB. Copyright © 2016 Elsevier Ltd. All rights reserved.

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.

Time resolved optical diagnostics of ZnO plasma plumes in air

SciTech Connect

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

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.

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

SciTech Connect

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

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.

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.

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 ...

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

SciTech Connect

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

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

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.

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

The Saturn hydrogen plume

NASA Astrophysics Data System (ADS)

Shemansky, D. E.; Liu, X.; Melin, H.

2009-12-01

Images of the Saturn atmosphere and magnetosphere in H Lyα emission during the Cassini spacecraft pre and post Saturn orbit insertion (SOI) event obtained using the UVIS experiment FUV spectrograph have revealed definitive evidence for the escape of H I atoms from the top of the thermosphere. An image at 0.1×0.1 Saturn equatorial radii ( RS) pixel resolution with an edge-on-view of the rings shows a distinctive structure (plume) with full width at half maximum (FWHM) of 0.56RS at the exobase sub-solar limb at ˜-13.5∘ latitude as part of the distributed outflow of H I from the sunlit hemisphere, with a counterpart on the antisolar side peaking near the equator above the exobase limb. The structure of the image indicates that part of the outflowing population is sub-orbital and re-enters the thermosphere in an approximate 5 h time scale. An evident larger more broadly distributed component fills the magnetosphere to beyond 45RS in the orbital plane in an asymmetric distribution in local time, similar to an image obtained at Voyager 1 post encounter in a different observational geometry. It has been found that H2 singlet ungerade Rydberg EUV/FUV emission spectra collected with the H Lyα into the image mosaic show a distinctive resonance property correlated with the H Lyα plume. The inferred approximate globally averaged energy deposition at the top of the thermosphere from the production of the hot atomic hydrogen accounts for the measured atmospheric temperature. The only known process capable of producing the atoms at the required few eV/atom kinetic energy appears to be the direct electron excitation of non-LTE H2XΣg+1( v:J) into the repulsive H2bΣu+3, although details of the processes need to be examined under the constraints imposed by the observations to determine compatibility with the current knowledge of hydrogen rate processes.

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).

Seismically imaging the Afar plume

NASA Astrophysics Data System (ADS)

Hammond, J. O.; Kendall, J. M.; Bastow, I. D.; Stuart, G. W.; Keir, D.; Ayele, A.; Ogubazghi, G.; Ebinger, C. J.; Belachew, M.

2011-12-01

Plume related flood basalt volcanism in Ethiopia has long been cited to have instigated continental breakup in northeast Africa. However, to date seismic images of the mantle beneath the region have not produced conclusive evidence of a plume-like structure. As a result the nature and even existence of a plume in the region and its role in rift initiation and continental rupture are debated. Previous seismic studies using regional deployments of sensors in East-Africa show that low seismic velocities underlie northeast Africa, but their resolution is limited to the top 200-300km of the Earth. Thus, the connection between the low velocities in the uppermost mantle and those imaged in global studies in the lower mantle is unclear. We have combined new data from Afar, Ethiopia with 6 other regional experiments and global network stations across Ethiopia, Eritrea, Djibouti and Yemen, to produce high-resolution models of upper mantle P- and S- wave velocities to the base of the transition zone. Relative travel time tomographic inversions show that the top 100km is dominated by focussed low velocity zones, likely associated with melt in the lithosphere/uppermost asthenosphere. Below these depths a broad SW-NE oriented sheet like upwelling extends down to the top of the transition zone. Within the transition zone two focussed sharp-sided low velocity regions exist: one beneath the Western Ethiopian plateau outside the rift valley, and the other beneath the Afar depression. The nature of the transition zone anomalies suggests that small upwellings may rise from a broader low velocity plume-like feature in the lower mantle. This interpretation is supported by numerical and analogue experiments that suggest the 660km phase change and viscosity jump may impede flow from the lower to upper mantle creating a thermal boundary layer at the base of the transition zone. This allows smaller, secondary upwellings to initiate and rise to the surface. Our images of secondary upwellings

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.

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.

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.

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.

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

Prenatal Ablation of Nicotinic Receptor alpha7 Cell Lineages Produces Lumbosacral Spina Bifida the Severity of Which is Modified by Choline and Nicotine Exposure

PubMed Central

Rogers, Scott W; Tvrdik, Petr; Capecchi, Mario R; Gahring, Lorise C

2012-01-01

Lumbosacral spina bifida is a common debilitating birth defect whose multiple causes are poorly understood. Here, we provide the first genetic delineation of cholinergic nicotinic receptor alpha7 (Chrna7) expression and link the ablation of the Chrna7 cell lineage to this condition in the mouse. Using homologous recombination, an IRES-Cre bi-cistronic cassette was introduced into the 3′ noncoding region of Chrna7 (Chrna7:Cre) for identifying cell lineages expressing this gene. This lineage first appears at embryonic day E9.0 in rhombomeres 3 and 5 of the neural tube and extends to cell subsets in most tissues by E14.5. Ablation of the Chrna7:Cre cell lineage in embryos from crosses with conditionally expressed attenuated diphtheria toxin results in precise developmental defects including omphalocele (89%) and open spina bifida (SB; 80%). We hypothesized that like humans, this defect would be modified by environmental compounds not only folic acid or choline but also nicotine. Prenatal chronic oral nicotine administration substantially worsened the defect to often include the rostral neural tube. In contrast, supplementation of the maternal diet with 2% choline decreased SB prevalence to 38% and dramatically reduced the defect severity. Folic acid supplementation only trended towards a reduced SB frequency. The omphalocele was unaffected by these interventions. These studies identify the Chrna7 cell lineage as participating in posterior neuropore closure and present a novel model of lower SB that can be substantially modified by the prenatal environment. © 2012 Wiley Periodicals, Inc. PMID:22473653

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

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.

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.

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

Segmented electrode hall thruster with reduced plume

DOEpatents

Fisch, Nathaniel J.; Raitses, Yevgeny

2004-08-17

An apparatus and method for thrusting plasma, utilizing a Hall thruster with segmented electrodes along the channel, which make the acceleration region as localized as possible. Also disclosed are methods of arranging the electrodes so as to minimize erosion and arcing. Also disclosed are methods of arranging the electrodes so as to produce a substantial reduction in plume divergence. The use of electrodes made of emissive material will reduce the radial potential drop within the channel, further decreasing the plume divergence. Also disclosed is a method of arranging and powering these electrodes so as to provide variable mode operation.

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.

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.

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.

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.

Simulating Irregular Source Geometries for Ionian Plumes

NASA Astrophysics Data System (ADS)

McDoniel, W. J.; Goldstein, D. B.; Varghese, P. L.; Trafton, L. M.; Buchta, D. A.; Freund, J.; Kieffer, S. W.

2011-05-01

Volcanic plumes on Io respresent a complex rarefied flow into a near-vacuum in the presence of gravity. A 3D Direct Simulation Monte Carlo (DSMC) method is used to investigate the gas dynamics of such plumes, with a focus on the effects of source geometry on far-field deposition patterns. A rectangular slit and a semicircular half annulus are simulated to illustrate general principles, especially the effects of vent curvature on deposition ring structure. Then two possible models for the giant plume Pele are presented. One is a curved line source corresponding to an IR image of a particularly hot region in the volcano's caldera and the other is a large area source corresponding to the entire caldera. The former is seen to produce the features seen in observations of Pele's ring, but with an error in orientation. The latter corrects the error in orientation, but loses some structure. A hybrid simulation of 3D slit flow is also discussed.

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 ...

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.

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.

A new binder-free and conductive-additive-free TiO2/WO3-W integrative anode material produced by laser ablation

NASA Astrophysics Data System (ADS)

Su, Yibo; Zhang, Hongjun; Liang, Peng; Liu, Kai; Cai, Mingyong; Huang, Zeya; Wang, Chang-An; Zhong, Minlin

2018-02-01

Although transition metal oxides anodes have attracted lots of attention, there are still many problems to be resolved. Complicated fabrication process, high cost and poor electrochemical performances are the most important ones, together hindering transition metal oxides anodes for practical use. Herein, we provide a new approach to fabricate a binder-free and conductive-additive-free TiO2/WO3-W integrative anode material through the nanosecond laser ablation and dip-coating technology, which simplifies the entire anode preparation process with no need for a conventional tape-casting procedure. Using this method, great time cost, machine cost and labor cost related to mixing and tape-casting process can be saved on the basis of good electrochemical performances. The prepared TiO2/WO3-W integrative anode realizes a first Coulombic efficiency of 75.6% and attains to a stable capacity within the first five cycles. It can still maintain a capacity of 600 mAh g-1 in the range of 0.01-3 V vs. Li+/Li at a current rate of 0.2 C after 500 cycles. This work offers a new way to achieve a fast fabrication of the integrative anode for lithium ion battery, which is universal for other transition metals (such as Fe, Cu, Ni, Co, Mo, W etc.).

MICROWAVE SPECTRA OF Ar\\cdot\\cdot\\cdotAgI AND H_{2}O\\cdot\\cdot\\cdotAgI PRODUCED BY LASER ABLATION

NASA Astrophysics Data System (ADS)

Mullaney, John C.; Medcraft, Chris; Walker, Nick; Legon, Anthony

2017-06-01

Complexes of argon and water with silver iodide have been formed in the gas phase by laser ablation of a silver iodide rod and studied using a chirped-pulse Fourier transform microwave spectrometer. Ar\\cdot\\cdot\\cdotAgI was characterized by its rotational spectrum and ab initio calculations carried out at the CCSD(T)(F12c)/cc-pVTZ-F12 explicitly correlated level of theory. The molecule was shown to be linear in the ground state, with atoms in the order shown. The Ar\\cdot\\cdot\\cdotAg and Ag-I bond lengths, r_{0}(Ar\\cdot\\cdot\\cdotAg) = 2.6759 Å{} and r_{0}(Ag-I) = 2.5356 Å, were determined. Other factors such as the dissociation energy, the intermolecular quadratic stretching force constant and the change in ionicity of AgI upon forming the complex were also determined and will be discussed with comparison to the series Ar\\cdot\\cdot\\cdotAgX (X = F, Cl, Br and I). Data of the H_{2}O\\cdot\\cdot\\cdotAgI complex will also be presented with isotopic studies ongoing.

Enceladus' Water Vapour Plumes

NASA Technical Reports Server (NTRS)

Hansen, Candice J.; Esposito, L.; Colwell, J.; Hendrix, A.; Matson, Dennis; Parkinson, C.; Pryor, W.; Shemansky, D.; Stewart, I.; Tew, J.;

COLD WEATHER PLUME STUDY

EPA Science Inventory

While many studies of power plant plume transport and transformation have been performed during the summer, few studies of these processes during the winter have been carried out. Accordingly, the U.S. Environmental Protection Agency and the Electric Power Research Institute join...

Evaluation of Visible Plumes.

ERIC Educational Resources Information Center

Brennan, Thomas

Developed for presentation at the 12th Conference on Methods in Air Pollution and Industrial Hygiene Studies, University of Southern California, April, 1971, this outline discusses plumes with contaminants that are visible to the naked eye. Information covers: (1) history of air pollution control regulations, (2) need for methods of evaluating…

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

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.

Smoke Plume Dispersal from the World Trade Center Disaster

NASA Image and Video Library

2006-09-06

The collapse of the World Trade Center on September 11, 2001, and the fires that followed produced a noxious smoke plume, a complex mixture of tiny airborne particles and gases as seen by NASA Terra spacecraft.

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.

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

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.

Plasma ignition thresholds in UV laser ablation plumes

NASA Astrophysics Data System (ADS)

Clarke, P.; Dyer, P. E.; Key, P. H.; Snelling, H. V.

Ultraviolet (UV) laser thresholds for plasma ignition on solid targets predicted from electron-neutral collisional heating are generally much higher than those observed experimentally. This inconsistency was reconciled by Rosen, et al. [2], who showed that excited-state photoionization played a key role in long-pulse UV laser breakdown. Here we develop a related model but with emphasis on pulses of 10 ns duration. Experimental results are also reported for titanium, copper, silicon, and ferulic acid targets in vacuum, irradiated with combinations of the XeF, KrF, and ArF lasers for comparison with predictions.

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.

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

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

Ablative therapy for liver tumours

PubMed Central

Dick, E A; Taylor-Robinson, S D; Thomas, H C; Gedroyc, W M W

2002-01-01

Established ablative therapies for the treatment of primary and secondary liver tumours, including percutaneous ethanol injection, cryotherapy, and radiofrequency ablation, are discussed. Newer techniques such as magnetic resonance imaging guided laser interstitial thermal therapy of liver tumours has produced a median survival rate of 40.8 months after treatment. The merits of this newly emerging technique are discussed, together with future developments, such as focused ultrasound therapy, which holds the promise of non-invasive thermoablation treatment on an outpatient basis. PMID:11950826

A study of space shuttle plumes in the lower thermosphere

NASA Astrophysics Data System (ADS)

Meier, R. R.; Stevens, Michael H.; Plane, John M. C.; Emmert, J. T.; Crowley, G.; Azeem, I.; Paxton, L. J.; Christensen, A. B.

2011-12-01

During the space shuttle main engine burn, some 350 t of water vapor are deposited at between 100 and 115 km. Subsequent photodissociation of water produces large plumes of atomic hydrogen that can expand rapidly and extend for thousands of kilometers. From 2002 to 2007, the Global Ultraviolet Imager (GUVI) on NASA's Thermosphere Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite imaged many of these hydrogen plumes at Lyman α (121.567 nm) while viewing in the nadir. The images reveal rapid plume expansion and occasional very fast transport to both north and south polar regions. Some plumes persist for up to 6 d. Near-simultaneous direct detections of water vapor were made with the Sounding of the Atmosphere with Broadband Emission Radiometry (SABER) instrument, also on TIMED. We compare the spreading of the hydrogen plume with a two-dimensional model that includes photodissociation as well as both vertical and horizontal diffusion. Molecular diffusion appears to be sufficient to account for the horizontal expansion, although wind shears and turbulent mixing may also contribute. We compare the bulk motion of the observed plumes with wind climatologies derived from satellite observations. The plumes can move much faster than predictions of wind climatologies. But dynamical processes not contained in wind climatologies, such as the quasi-two-day wave, can account for at least some of the high speed observations. The plume phenomena raise a number of important questions about lower thermospheric and mesospheric processes, ranging from dynamics and chemistry to polar mesospheric cloud formation and climatology.

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

The impact of glacier geometry on meltwater plume structure and submarine melt in Greenland fjords

NASA Astrophysics Data System (ADS)

Carroll, D.; Sutherland, D. A.; Hudson, B.; Moon, T.; Catania, G. A.; Shroyer, E. L.; Nash, J. D.; Bartholomaus, T. C.; Felikson, D.; Stearns, L. A.; Noël, B. P. Y.; Broeke, M. R.

2016-09-01

Meltwater from the Greenland Ice Sheet often drains subglacially into fjords, driving upwelling plumes at glacier termini. Ocean models and observations of submarine termini suggest that plumes enhance melt and undercutting, leading to calving and potential glacier destabilization. Here we systematically evaluate how simulated plume structure and submarine melt during summer months depends on realistic ranges of subglacial discharge, glacier depth, and ocean stratification from 12 Greenland fjords. Our results show that grounding line depth is a strong control on plume-induced submarine melt: deep glaciers produce warm, salty subsurface plumes that undercut termini, and shallow glaciers produce cold, fresh surface-trapped plumes that can overcut termini. Due to sustained upwelling velocities, plumes in cold, shallow fjords can induce equivalent depth-averaged melt rates compared to warm, deep fjords. These results detail a direct ocean-ice feedback that can affect the Greenland Ice Sheet.

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.

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.

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.

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.

Representative Atmospheric Plume Development for Elevated Releases

SciTech Connect

Eslinger, Paul W.; Lowrey, Justin D.; McIntyre, Justin I.

2014-02-01

An atmospheric explosion of a low-yield nuclear device will produce a large number of radioactive isotopes, some of which can be measured with airborne detection systems. However, properly equipped aircraft may not arrive in the region where an explosion occurred for a number of hours after the event. Atmospheric conditions will have caused the radioactive plume to move and diffuse before the aircraft arrives. The science behind predicting atmospheric plume movement has advanced enough that the location of the maximum concentrations in the plume can be determined reasonably accurately in real time, or near real time. Given the assumption thatmore » an aircraft can follow a plume, this study addresses the amount of atmospheric dilution expected to occur in a representative plume as a function of time past the release event. The approach models atmospheric transport of hypothetical releases from a single location for every day in a year using the publically available HYSPLIT code. The effective dilution factors for the point of maximum concentration in an elevated plume based on a release of a non-decaying, non-depositing tracer can vary by orders of magnitude depending on the day of the release, even for the same number of hours after the release event. However, the median of the dilution factors based on releases for 365 consecutive days at one site follows a power law relationship in time, as shown in Figure S-1. The relationship is good enough to provide a general rule of thumb for estimating typical future dilution factors in a plume starting at the same point. However, the coefficients of the power law function may vary for different release point locations. Radioactive decay causes the effective dilution factors to decrease more quickly with the time past the release event than the dilution factors based on a non-decaying tracer. An analytical expression for the dilution factors of isotopes with different half-lives can be developed given the power law

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

through faster mantle and reduces the distance though the slower asthenosphere. With this interpretation, the inference of a radially symmetric ~40-70 km high-~250 km-radius ‘bump’ of uplift of the base of buoyant plume-fed asthenosphere (PFA) can be directly estimated from PLUME results and the measured ~6-10% reduction in shear velocity between the PFA and underlying mantle. The inferred dynamic relief at the base of the PFA due to buoyancy within the underlying plume conduit is strikingly similar to the relief we find in recent axisymmetric 2D and Cartesian 3-D numerical experiments that explore the dynamics of mantle convection with a PFA. The width and height of the bump scale directly with the total buoyancy anomaly in the upper ~500km of the plume conduit, we discuss numerical experiments that quantify this relationship, show that it is, to first order, independent of the viscosity of material in the plume conduit or asthenosphere, and which also quantify the ~400km-radius geoid anomaly produced by these subasthenospheric mantle density anomalies. This effect can only happen if the asthenosphere is more buoyant than underlying mantle — and is therefore direct evidence that a buoyant plume-fed asthenosphere exists around Hawaii.

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�

Direct His bundle pacing post AVN ablation.

PubMed

Lakshmanadoss, Umashankar; Aggarwal, Ashim; Huang, David T; Daubert, James P; Shah, Abrar

2009-08-01

Atrioventricular nodal (AVN) ablation with concomitant pacemaker implantation is one of the strategies that reduce symptoms in patients with atrial fibrillation (AF). However, the long-term adverse effects of right ventricular (RV) apical pacing have led to the search for alternating sites of pacing. Biventricular pacing produces a significant improvement in functional capacity over RV pacing in patients undergoing AVN ablation. Another alternative site for pacing is direct His bundle to reduce the adverse outcome of RV pacing. Here, we present a case of direct His bundle pacing using steerable lead delivery system in a patient with symptomatic paroxysmal AF with concurrent AVN ablation.

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.

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.

Resolving the Mass Production and Surface Structure of the Enceladus Dust Plume

NASA Astrophysics Data System (ADS)

Kempf, Sascha; Southworth, Benjamin; Spitale, Joseph; Srama, Ralf; Schmidt, Jürgen; Postberg, Frank

2017-04-01

There are ongoing arguments with regards to the Enceldaus plume, both on the total mass of ice particles produced by the plume in kg/s, as well as the structure of plume ejection along the tiger stripes. Herein, results from Cassini's Cosmic Dust Analyzer (CDA) and Imaging Science Subsystem (ISS) are used in conjunction with large-scale plume simulations to resolve each of these issues. Additional results are provided on the short-term variability of the plume, and the relation of specifc surface deposition features to emissions along given areas of the tiger stripes. By adjusting their plume model to the dust flux measured by the Cassini dust detector during the close Enceladus flyby in 2005, Schmidt et al. (2008) obtained a total dust production rate in the plumes of about

Microwave Tissue Ablation: Biophysics, Technology and Applications

PubMed Central

2010-01-01

Microwave ablation is an emerging treatment option for many cancers, cardiac arrhythmias and other medical conditions. During treatment, microwaves are applied directly to tissues to produce rapid temperature elevations sufficient to produce immediate coagulative necrosis. The engineering design criteria for each application differ, with individual consideration for factors such as desired ablation zone size, treatment duration, and procedural invasiveness. Recent technological developments in applicator cooling, power control and system optimization for specific applications promise to increase the utilization of microwave ablation in the future. This article will review the basic biophysics of microwave tissue heating, provide an overview of the design and operation of current equipment, and outline areas for future research for microwave ablation. PMID:21175404

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.

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.

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.

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

Influence of main forcing affecting the Tagus turbid plume under high river discharges using MODIS imagery

PubMed Central

Gómez-Gesteira, M.; Mendes, R.; deCastro, M.; Vaz, N.; Dias, J. M.

2017-01-01

The role of river discharge, wind and tide on the extension and variability of the Tagus River plume was analyzed from 2003 to 2015. This study was performed combining daily images obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor located onboard the Aqua and Terra satellites. Composites were generated by averaging pixels with the same forcing conditions. River discharge shows a strong relation with the extension of the Tagus plume. The plume grows with the increasing river discharge and express a two day lag caused by the long residence time of water within the estuary. The Tagus turbid plume was found to be smaller under northerly and easterly winds, than under southerly and westerly winds. It is suggested that upwelling favoring winds provoke the offshore movement of the plume material with a rapidly decrease in turbidity values whereas downwelling favoring winds retain plume material in the north coast close to the Tagus mouth. Eastern cross-shore (oceanward) winds spread the plume seaward and to the north following the coast geometry, whereas western cross-shore (landward) winds keep the plume material in both alongshore directions occupying a large part of the area enclosed by the bay. Low tides produce larger and more turbid plumes than high tides. In terms of fortnightly periodicity, the maximum plume extension corresponding to the highest turbidity is observed during and after spring tides. Minimum plume extension associated with the lowest turbidity occurs during and after neap tides. PMID:29073209

Influence of main forcing affecting the Tagus turbid plume under high river discharges using MODIS imagery.

PubMed

Fernández-Nóvoa, D; Gómez-Gesteira, M; Mendes, R; deCastro, M; Vaz, N; Dias, J M

2017-01-01

The role of river discharge, wind and tide on the extension and variability of the Tagus River plume was analyzed from 2003 to 2015. This study was performed combining daily images obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor located onboard the Aqua and Terra satellites. Composites were generated by averaging pixels with the same forcing conditions. River discharge shows a strong relation with the extension of the Tagus plume. The plume grows with the increasing river discharge and express a two day lag caused by the long residence time of water within the estuary. The Tagus turbid plume was found to be smaller under northerly and easterly winds, than under southerly and westerly winds. It is suggested that upwelling favoring winds provoke the offshore movement of the plume material with a rapidly decrease in turbidity values whereas downwelling favoring winds retain plume material in the north coast close to the Tagus mouth. Eastern cross-shore (oceanward) winds spread the plume seaward and to the north following the coast geometry, whereas western cross-shore (landward) winds keep the plume material in both alongshore directions occupying a large part of the area enclosed by the bay. Low tides produce larger and more turbid plumes than high tides. In terms of fortnightly periodicity, the maximum plume extension corresponding to the highest turbidity is observed during and after spring tides. Minimum plume extension associated with the lowest turbidity occurs during and after neap tides.

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.

Can molecular diffusion explain Space Shuttle plume spreading?

NASA Astrophysics Data System (ADS)

Meier, R. R.; Plane, John M. C.; Stevens, Michael H.; Paxton, L. J.; Christensen, A. B.; Crowley, G.

2010-04-01

The satellite-borne Global Ultraviolet Imager (GUVI) has produced more than 20 images of NASA Space Shuttle main engine plumes in the lower thermosphere. These reveal atomic hydrogen and, by inference, water vapor transport over hemispherical-scale distances with speeds much faster than expected from models of thermospheric wind motions. Furthermore, the hydrogen plumes expand rapidly. We find rates that exceed the horizontal diffusion speed at nominal plume altitudes of 104-112 km. Kelley et al. (2009) have proposed a 2-D turbulence mechanism to explain the observed spreading rates (and rapid advection) of the plumes. But upon further investigation, we conclude that H atom diffusion can indeed account for the observed expansion rates by recognizing that vertical diffusion quickly conveys atoms to higher altitudes where horizontal diffusion is much more rapid. We also find evidence for H atom production directly during the Shuttle's main engine burn.

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.

The planet beyond the plume hypothesis

NASA Astrophysics Data System (ADS)

Smith, Alan D.; Lewis, Charles

1999-12-01

Acceptance of the theory of plate tectonics was accompanied by the rise of the mantle plume/hotspot concept which has come to dominate geodynamics from its use both as an explanation for the origin of intraplate volcanism and as a reference frame for plate motions. However, even with a large degree of flexibility permitted in plume composition, temperature, size, and depth of origin, adoption of any limited number of hotspots means the plume model cannot account for all occurrences of the type of volcanism it was devised to explain. While scientific protocol would normally demand that an alternative explanation be sought, there have been few challenges to "plume theory" on account of a series of intricate controls set up by the plume model which makes plumes seem to be an essential feature of the Earth. The hotspot frame acts not only as a reference but also controls plate tectonics. Accommodating plumes relegates mantle convection to a weak, sluggish effect such that basal drag appears as a minor, resisting force, with plates having to move themselves by boundary forces and continents having to be rifted by plumes. Correspondingly, the geochemical evolution of the mantle is controlled by the requirement to isolate subducted crust into plume sources which limits potential buffers on the composition of the MORB-source to plume- or lower mantle material. Crustal growth and Precambrian tectonics are controlled by interpretations of greenstone belts as oceanic plateaus generated by plumes. Challenges to any aspect of the plume model are thus liable to be dismissed unless a counter explanation is offered across the geodynamic spectrum influenced by "plume theory". Nonetheless, an alternative synthesis can be made based on longstanding petrological evidence for derivation of intraplate volcanism from volatile-bearing sources (wetspots) in conjunction with concepts dismissed for being incompatible or superfluous to "plume theory". In the alternative Earth, the sources for

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

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

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.

Influence of the Liquid on Femtosecond Laser Ablation of Iron

NASA Astrophysics Data System (ADS)

Kanitz, A.; Hoppius, J. S.; Gurevich, E. L.; Ostendorf, A.

Ultrashort pulse laser ablation has become a very important industrial method for highly precise material removal ranging from sensitive thin film processing to drilling and cutting of metals. Over the last decade, a new method to produce pure nanoparticles emerged from this technique: Pulsed Laser Ablation in Liquids (PLAL). By this method, the ablation of material by a laser beam is used to generate a metal vapor within the liquid in order to obtain nanoparticles from its recondensation process. It is well known that the liquid significantly alters the ablation properties of the substrate, in our case iron. For example, the ablation rate and crater morphology differ depending on the used liquid. We present our studies on the efficiency and quality of ablated grooves in water, methanol, acetone, ethanol and toluene. The produced grooves are investigated by means of white-light interferometry, EDX and SEM.

Io Plume Monitoring (frames 1-36)

NASA Technical Reports Server (NTRS)

1997-01-01

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 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

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

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.

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.

Design of Ablation Test Device for Brick Coating of Gun

NASA Astrophysics Data System (ADS)

shirui, YAO; yongcai, CHEN; fei, WANG; jianxin, ZHAO

2018-03-01

As a result of the live ammunition test conditions, the barrel resistance of the barrel coating has high cost, time consuming, low efficiency and high test site requirements. This article designed a simple, convenient and efficient test device. Through the internal trajectory calculation by Matlab, the ablation environment produced by the ablation test device has achieved the expected effect, which is consistent with the working condition of the tube in the launching state, which can better reflect the ablation of the coating.

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.

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

SciTech Connect

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

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

SciTech Connect

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

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...

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.

The magnetic particle plume solar sail concept

NASA Astrophysics Data System (ADS)

Knuth, William H.

2000-01-01

A magnetic particle space radiator was proposed in the late 1950s as a means to dissipate waste heat from space nuclear systems. The concept was a plume of hot magnetic particles confined to and traversing a magnetic field produced by super conducting magnets in the space vehicle. The large surface area of the hot particles was expected to effectively radiate away the heat. The cooling particles followed along the lines of the magnetic field and eventually returned to the vehicle where they again picked up a fresh charge of waste heat for return out to the plume. This paper presents a new concept for consideration. The same basic magnetic particle plume idea is proposed in this paper, except the purpose of the plume would be to receive momentum (and possibly electric power) from the solar wind in the manner of a solar sail. Recent nano-technologies allow the magnetic particles to be 2-3 orders of magnitude smaller than envisioned for the heat radiator, and the magnetic field would be stronger than we envisioned in the '50s. The application of the magnetic solar sail would be for propelling space-faring vehicles on long duration exploration of the solar system and possibly beyond. A first look is provided at the elements of the system, together with an estimate of the thrust potential and the approximate weights of the system. The system appears to have the potential to develop on the order of 50lb and 100lb of thrust and weight on the order of 15,000lb .

Quantitative Chemical Analysis of Enceladus' Plume Composition.

NASA Astrophysics Data System (ADS)

Peter, J.; Nordheim, T.; Hofmann, A.; Hand, K. P.

2017-12-01

Analyses of data from Cassini's Ion and Neutral Mass Spectrometer (INMS) taken during several close flybys of Enceladus suggest the presence of a potentially habitable ocean underneath the ice shell [1,2]. Proper identification of the molecular species sampled from Enceladus' plumes by INMS is of utmost importance for characterizing the ocean's chemical composition. Data from Cassini's Cosmic Dust Analyzer (CDA) and Visible and Infrared Mapping Spectrometer (VIMS) have provided clues for possible plume chemistry, but further analysis of the INMS data is necessary [3,4]. Here we present a novel automated algorithm for comparing INMS spectra and analogue laboratory spectra to a vast library of sample spectra provided by the National Institute of Standards and Technology (NIST). The algorithm implements a Monte Carlo simulation that computes the angular similarity between the spectrum of interest and a random sample of synthetic spectra generated at arbitrary mixing ratios of molecular species. The synthetic spectra with the highest similarity scores are then averaged to produce a convergent estimate of the mixing ratio of the spectrum of interest. Here we will discuss the application of this technique to INMS and laboratory data and the implication of our preliminary results for the ocean chemistry and habitability of Enceladus. 1. Waite, J., et al., 2009. Liquid Water on Enceladus From Observations of Ammonia and 40Ar in the Plume. Nature 460, 487-498. 2. Waite, J., et al. 2017. Cassini Finds Molecular Hydrogen in the Enceladus Plume: Evidence for Hydrothermal Processes. Science 356, 155-159. 3. Postberg, F., et al., 2008. The E Ring in the Vicinity of Enceladus II: Signatures of Enceladus in the Elemental Composition of E-Ring Particles. Icarus 193(2), 438-454. 4. Brown, R., et al., 2006. Composition and Physical Properties of Enceladus' Surface. Science 311, 1425-1428.

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.

Geochronology and geochemistry of basaltic rocks from the Sartuohai ophiolitic mélange, NW China: Implications for a Devonian mantle plume within the Junggar Ocean

NASA Astrophysics Data System (ADS)

Yang, Gaoxue; Li, Yongjun; Santosh, M.; Yang, Baokai; Yan, Jing; Zhang, Bing; Tong, Lili

2012-10-01

The West Junggar domain in NW China is a distinct tectonic unit of the Central Asian Orogenic Belt (CAOB). It is composed of Paleozoic ophiolitic mélanges, arcs and accretionary complexes. The Sartuohai ophiolitic mélange in the eastern West Junggar forms the northeastern part of the Darbut ophiolitic mélange, which contains serpentinized harzburgite, pyroxenite, dunite, cumulate, pillow lava, abyssal radiolarian chert and podiform chromite, overlain by the Early Carboniferous volcano-sedimentary rocks. In this paper we report new geochronological and geochemical data from basaltic and gabbroic blocks embedded within the Sartuohai ophiolitic mélange, to assess the possible presence of a Devonian mantle plume in the West Junggar, and evaluate the petrogenesis and implications for understanding of the Paleozoic continental accretion of CAOB. Zircon U-Pb analyses from the alkali basalt and gabbro by laser ablation inductively coupled plasma mass spectrometry yielded weighted mean ages of 375 ± 2 Ma and 368 ± 11 Ma. Geochemically, the Sartuohai ophiolitic mélange includes at least two distinct magmatic units: (1) a Late Devonian fragmented ophiolite, which were produced by ca. 2-10% spinel lherzolite partial melting in arc-related setting, and (2) contemporary alkali lavas, which were derived from 5% to 10% garnet + minor spinel lherzolite partial melting in an oceanic plateau or a seamount. Based on detailed zircon U-Pb dating and geochemical data for basalts and gabbros from the Sartuohai ophiolitic mélange, in combination with previous work, indicate a complex evolution by subduction-accretion processes from the Devonian to the Carboniferous. Furthermore, the alkali basalts from the Sartuohai ophiolitic mélange might be correlated to a Devonian mantle plume-related magmatism within the Junggar Ocean. If the plume model as proposed here is correct, it would suggest that mantle plume activity significantly contributed to the crustal growth in the CAOB.

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.

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...

Algorithms for Autonomous Plume Detection on Outer Planet Satellites

NASA Astrophysics Data System (ADS)

Lin, Y.; Bunte, M. K.; Saripalli, S.; Greeley, R.

2011-12-01

We investigate techniques for automated detection of geophysical events (i.e., volcanic plumes) from spacecraft images. The algorithms presented here have not been previously applied to detection of transient events on outer planet satellites. We apply Scale Invariant Feature Transform (SIFT) to raw images of Io and Enceladus from the Voyager, Galileo, Cassini, and New Horizons missions. SIFT produces distinct interest points in every image; feature descriptors are reasonably invariant to changes in illumination, image noise, rotation, scaling, and small changes in viewpoint. We classified these descriptors as plumes using the k-nearest neighbor (KNN) algorithm. In KNN, an object is classified by its similarity to examples in a training set of images based on user defined thresholds. Using the complete database of Io images and a selection of Enceladus images where 1-3 plumes were manually detected in each image, we successfully detected 74% of plumes in Galileo and New Horizons images, 95% in Voyager images, and 93% in Cassini images. Preliminary tests yielded some false positive detections; further iterations will improve performance. In images where detections fail, plumes are less than 9 pixels in size or are lost in image glare. We compared the appearance of plumes and illuminated mountain slopes to determine the potential for feature classification. We successfully differentiated features. An advantage over other methods is the ability to detect plumes in non-limb views where they appear in the shadowed part of the surface; improvements will enable detection against the illuminated background surface where gradient changes would otherwise preclude detection. This detection method has potential applications to future outer planet missions for sustained plume monitoring campaigns and onboard automated prioritization of all spacecraft data. The complementary nature of this method is such that it could be used in conjunction with edge detection algorithms to

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

SciTech Connect

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

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.

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

Glue septal ablation: A promising alternative to alcohol septal ablation

PubMed Central

Aytemir, Kudret; Oto, Ali

2016-01-01

Hypertrophic cardiomyopathy (HCM) is defined as myocardial hypertrophy in the absence of another cardiac or systemic disease capable of producing the magnitude of present hypertrophy. In about 70% of patients with HCM, there is left ventricular outflow tract (LVOT) obstruction (LVOTO) and this is known as obstructive type of hypertrophic cardiomyopathy (HOCM). Cases refractory to medical treatment have had two options either surgical septal myectomy or alcohol septal ablation (ASA) to alleviate LVOT gradient. ASA may cause some life-threatening complications including conduction disturbances and complete heart block, hemodynamic compromise, ventricular arrhythmias, distant and massive myocardial necrosis. Glue septal ablation (GSA) is a promising technique for the treatment of HOCM. Glue seems to be superior to alcohol due to some intrinsic advantageous properties of glue such as immediate polymerization which prevents the leak into the left anterior descending coronary artery and it is particularly useful in patients with collaterals to the right coronary artery in whom alcohol ablation is contraindicated. In our experience, GSA is effective and also a safe technique without significant complications. GSA decreases LVOT gradient immediately after the procedure and this reduction persists during 12 months of follow-up. It improves New York Heart Association functional capacity and decrease interventricular septal wall thickness. Further studies are needed in order to assess the long-term efficacy and safety of this technique. PMID:27011786

Femtosecond laser lithotripsy: feasibility and ablation mechanism.

PubMed

Qiu, Jinze; Teichman, Joel M H; Wang, Tianyi; Neev, Joseph; Glickman, Randolph D; Chan, Kin Foong; Milner, Thomas E

2010-01-01

Light emitted from a femtosecond laser is capable of plasma-induced ablation of various materials. We tested the feasibility of utilizing femtosecond-pulsed laser radiation (lambda=800 nm, 140 fs, 0.9 mJ/pulse) for ablation of urinary calculi. Ablation craters were observed in human calculi of greater than 90% calcium oxalate monohydrate (COM), cystine (CYST), or magnesium ammonium phosphate hexahydrate (MAPH). Largest crater volumes were achieved on CYST stones, among the most difficult stones to fragment using Holmium:YAG (Ho:YAG) lithotripsy. Diameter of debris was characterized using optical microscopy and found to be less than 20 microm, substantially smaller than that produced by long-pulsed Ho:YAG ablation. Stone retropulsion, monitored by a high-speed camera system with a spatial resolution of 15 microm, was negligible for stones with mass as small as 0.06 g. Peak shock wave pressures were less than 2 bars, measured by a polyvinylidene fluoride (PVDF) needle hydrophone. Ablation dynamics were visualized and characterized with pump-probe imaging and fast flash photography and correlated to shock wave pressures. Because femtosecond-pulsed laser ablates urinary calculi of soft and hard compositions, with micron-sized debris, negligible stone retropulsion, and small shock wave pressures, we conclude that the approach is a promising candidate technique for lithotripsy.

FOOTPRINT: A New Tool to Predict the Potential Impact of Biofuels on BTEX Plumes

EPA Science Inventory

Ahsanuzzaman et al. (2008) used the Deeb et al. (2002) conceptual model to construct a simple screening model to estimate the area of a plume of benzene produced from a release of gasoline containing ethanol. The screening model estimates the plume area, or footprint of the plum...

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.

Thermal distribution of microwave antenna for atrial fibrillation catheter ablation.

PubMed

Zhang, Huijuan; Nan, Qun; Liu, Youjun

2013-09-01

The aim of this study is to investigate the effects of ablation parameters on thermal distribution during microwave atrial fibrillation catheter ablation, such as ablation time, ablation power, blood condition and antenna placement, and give proper ablative parameters to realise transmural ablation. In this paper, simplified 3D antenna-myocardium-blood finite element method models were built to simulate the endocardial ablation operation. Thermal distribution was obtained based on the coupled electromagnetic-thermal analysis. Under different antenna placement conditions and different microwave power inputs within 60 s, the lesion dimensions (maximum depth, maximum width) of the ablation zones were analysed. The ablation width and depth increased with the ablation time. The increase rate significantly slowed down after 10 s. The maximum temperature was located in 1 mm under the antenna tip when perpendicular to the endocardium, while 1.5 mm away from the antenna axis and 26 mm along the antenna (with antenna length about 30 mm) in the myocardium when parallel to the endocardium. The maximum temperature in the ablated area decreased and the effective ablation area (with the temperature raised to 50°C) shifted deeper into the myocardium due to the blood cooling. The research validated that the microwave antenna can provide continuous long and linear lesions for the treatment of atrial fibrillation. The dimensions of the created lesion widths were all larger than those of the depths. It is easy for the microwave antenna to produce transmural lesions for an atrial wall thickness of 2-6 mm by adjusting the applied power and ablation time.

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.

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

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

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

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.

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.

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

lesser contribution. Moreover, our best-fit solutions for the plume are sensitive to the vent conditions chosen. The spreading angle of the jet produced is the main difference among the vent conditions and thus it appears to be an important parameter in fitting to these INMS data sets. In general, we find that narrow jets produce better fits, suggesting high Mach numbers (> 5) at the vents. This is supported by certain narrow features believed to be jets in both the INMS and UVIS data sets. This tends to rule out sublimation from the surface but points to a deep underground source for the plume. However, the underground source can be either sublimation from an icy reservoir or evaporation from a liquid reservoir. A high Mach number at the vent also suggests subsurface channels with large variations in width and not fairly straight channels so that the gas can undergo sufficient expansion. Additionally, the broad spreading angles inferred for the μm-sized grains (Ingersoll, A.P. and Ewald, S.P. [2011] Icarus, 216, 492-506; Postberg, F., et al. [2011] Nature, 474, 620-622) cannot be due to spreading by the gas above the surface alone. Some other mechanism(s) must also be responsible, perhaps occurring below the surface, which further points to an underground source for the plume.

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

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.

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).

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.

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.

Moldable cork ablation material

NASA Technical Reports Server (NTRS)

1977-01-01

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

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.

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.

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.

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

Tracking aerosol plumes: lidar, modeling, and in situ measurement

NASA Astrophysics Data System (ADS)

Calhoun, Ron J.; Heap, Robert; Sommer, Jeffrey; Princevac, Marko; Peccia, Jordan; Fernando, H.

2004-09-01

The authors report on recent progress of on-going research at Arizona State University for tracking aerosol plumes using remote sensing and modeling approaches. ASU participated in a large field experiment, Joint Urban 2003, focused on urban and suburban flows and dispersion phenomena which took place in Oklahoma City during summer 2003. A variety of instruments were deployed, including two Doppler-lidars. ASU deployed one lidar and the Army Research deployed the other. Close communication and collaboration has produced datasets which will be available for dual Doppler analysis. The lidars were situated in a way to provide insight into dynamical flow structures caused by the urban core. Complementary scanning by the two lidars during the July 4 firework display in Oklahoma City demonstrated that smoke plumes could be tracked through the atmosphere above the urban area. Horizontal advection and dispersion of the smoke plumes were tracked on two horizontal planes by the ASU lidar and in two vertical planes with a similar lidar operated by the Army Research Laboratory. A number of plume dispersion modeling systems are being used at ASU for the modeling of plumes in catastrophic release scenarios. Progress using feature tracking techniques and data fusion approaches is presented for utilizing single and dual radial velocity fields from coherent Doppler lidar to improve dispersion modeling. The possibility of producing sensor/computational tools for civil and military defense applications appears worth further investigation. An experiment attempting to characterize bioaerosol plumes (using both lidar and in situ biological measurements) associated with the application of biosolids on agricultural fields is in progress at the time of writing.

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 (...

The growth and decay of equatorial backscatter plumes

NASA Astrophysics Data System (ADS)

Tsunoda, R. T.

1980-02-01

During the past three years, a series of rocket experiments from the Kwajalein Atoll, Marshall Islands, were conducted to investigate the character of intense, scintillation-producing irregularities that occur in the nighttime equatorial ionosphere. Because the source mechanism of equatorial irregularities, believed to be the Rayleigh-Taylor instability, is analogous to that which generates plasma-density striations in a nuclear-induced environment, there is considerable interest in the underlying physics that controls the characteristics of these irregularities. A primary objective of ALTAIR investigations of equatorial irregularities is to seek an understanding of the underlying physics by establishing the relationship between meter-scale irregularities (detected by ALTAIR), and the large-scale plasma-density depletions (or 'bubbles') that contain the kilometer-scale, scintillation-producing irregularities. We describe the time evolution of backscatter 'plumes' produced by one meter equatorial field-aligned irregularities. Using ALTAIR, a fully steerable backscatter radar, to repeatedly map selected plumes, we characterize the dynamic behavior of plumes in terms of growth and a decay phase. Most of the observed characteristics are found to be consistent with equatorial-irregularity generation predicted by current theories of Rayleigh-Taylor and gradient-drift instabilities. However, other characteristics have been found that suggest key roles played by the eastward neutral wind and by altitude-modulation of the bottomside F layer in establishing the initial conditions for plume growth.

Vortex Ring Formation in a Starting Buoyant Plume

NASA Astrophysics Data System (ADS)

Pottebaum, Tait; Shusser, Michael; Gharib, Morteza

1999-11-01

Vortex ring formation in starting buoyant plumes is studied experimentally. Buoyant plumes are produced using a heating element at the base of a water tank. Digital particle image velocimetry and thermometry (DPIVT) is used to obtain the velocity and temperature fields, from which the vorticity and density fields are determined. The results indicate that the circulation of the vortex ring initially grows and saturates at later times. This saturation process is associated with the disconnection of the vorticity field of the vortex ring from that of the trailing plume. This is analogous to the pinch off of a vortex ring produced by a piston as reported by Gharib et al (1998 JFM 360, 121-140). Similar to the definition used by Gharib et al, a 'formation number' can be defined as the normalized time at which the circulation produced by the buoyancy source is equal to the peak circulation achieved by the vortex ring. This formation number is examined for a variety of plume density ratios. The results are compared to predictions of a model based on the Kelvin-Benjamin variational principle for steady axis-touching vortex rings.

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.

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.

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

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.

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

Laser ablated hard coating for microtools

DOEpatents

McLean, II, William; Balooch, Mehdi; Siekhaus, Wigbert J.

1998-05-05

Wear-resistant coatings composed of laser ablated hard carbon films, are deposited by pulsed laser ablation using visible light, on instruments such as microscope tips and micro-surgical tools. Hard carbon, known as diamond-like carbon (DLC), films produced by pulsed laser ablation using visible light enhances the abrasion resistance, wear characteristics, and lifetimes of small tools or instruments, such as small, sharp silicon tips used in atomic probe microscopy without significantly affecting the sharpness or size of these devices. For example, a 10-20 nm layer of diamond-like carbon on a standard silicon atomic force microscope (AFM) tip, enables the useful operating life of the tip to be increased by at least twofold. Moreover, the low inherent friction coefficient of the DLC coating leads to higher resolution for AFM tips operating in the contact mode.

Specific Impulse Definition for Ablative Laser Propulsion

NASA Technical Reports Server (NTRS)

Herren, Kenneth A.; Gregory, Don A.

2004-01-01

The term "specific impulse" is so ingrained in the field of rocket propulsion that it is unlikely that any fundamental argument would be taken seriously for its removal. It is not an ideal measure but it does give an indication of the amount of mass flow (mass loss/time), as in fuel rate, required to produce a measured thrust over some time period This investigation explores the implications of being able to accurately measure the ablation rate and how the language used to describe the specific impulse results may have to change slightly, and recasts the specific impulse as something that is not a time average. It is not currently possible to measure the ablation rate accurately in real time so it is generally just assumed that a constant amount of material will be removed for each laser pulse delivered The specific impulse dependence on the ablation rate is determined here as a correction to the classical textbook definition.

Laser ablated hard coating for microtools

DOEpatents

McLean, W. II; Balooch, M.; Siekhaus, W.J.

1998-05-05

Wear-resistant coatings composed of laser ablated hard carbon films, are deposited by pulsed laser ablation using visible light, on instruments such as microscope tips and micro-surgical tools. Hard carbon, known as diamond-like carbon (DLC), films produced by pulsed laser ablation using visible light enhances the abrasion resistance, wear characteristics, and lifetimes of small tools or instruments, such as small, sharp silicon tips used in atomic probe microscopy without significantly affecting the sharpness or size of these devices. For example, a 10--20 nm layer of diamond-like carbon on a standard silicon atomic force microscope (AFM) tip, enables the useful operating life of the tip to be increased by at least twofold. Moreover, the low inherent friction coefficient of the DLC coating leads to higher resolution for AFM tips operating in the contact mode. 12 figs.

Standoff analysis of laser-produced plasmas using laser-induced fluorescence

SciTech Connect

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

We report the use of laser-induced fluorescence (LIF) of laser ablation plumes for standoff applications. The standoff analysis of Al species, as major and minor species in samples, is performed in a nanosecond laser-produced plasma created at a distance ~10 m. The LIF analysis is performed by resonantly exciting an Al transition at 394.4 nm using a continuous wave (cw) tunable laser and by collecting the direct-line fluorescence signal at 396.15 nm. The spectral resolution of LIF is obtained by scanning the cw tunable LIF laser across the selected Al transition. Our results highlight that LIF provides enhanced signal intensity,more » emission persistence, and spectral resolution when compared to thermally-excited emission, and these are crucial considerations for using laser-produced plasma for standoff isotopic analysis.« less

Combining Electrolysis and Electroporation for Tissue Ablation.

PubMed

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

2015-08-01

Electrolytic ablation is a method that operates by delivering low magnitude direct current to the target region over long periods of time, generating electrolytic products that destroy cells. This study was designed to explore the hypothesis stating that electrolytic ablation can be made more effective when the electrolysis-producing electric charges are delivered using electric pulses with field strength typical in reversible electroporation protocols. (For brevity we will refer to tissue ablation protocols that combine electroporation and electrolysis as E(2).) The mechanistic explanation of this hypothesis is related to the idea that products of electrolysis generated by E(2) protocols can gain access to the interior of the cell through the electroporation permeabilized cell membrane and therefore cause more effective cell death than from the exterior of an intact cell. The goal of this study is to provide a first-order examination of this hypothesis by comparing the charge dosage required to cause a comparable level of damage to a rat liver, in vivo, when using either conventional electrolysis or E(2) approaches. Our results show that E(2) protocols produce tissue damage that is consistent with electrolytic ablation. Furthermore, E(2) protocols cause damage comparable to that produced by conventional electrolytic protocols while delivering orders of magnitude less charge to the target tissue over much shorter periods of time. © The Author(s) 2014.

Delta 2 Explosion Plume Analysis Report

NASA Technical Reports Server (NTRS)

Evans, Randolph J.

2000-01-01

A Delta II rocket exploded seconds after liftoff from Cape Canaveral Air Force Station (CCAFS) on 17 January 1997. The cloud produced by the explosion provided an opportunity to evaluate the models which are used to track potentially toxic dispersing plumes and clouds at CCAFS. The primary goal of this project was to conduct a case study of the dispersing cloud and the models used to predict the dispersion resulting from the explosion. The case study was conducted by comparing mesoscale and dispersion model results with available meteorological and plume observations. This study was funded by KSC under Applied Meteorology Unit (AMU) option hours. The models used in the study are part of the Eastern Range Dispersion Assessment System (ERDAS) and include the Regional Atmospheric Modeling System (RAMS), HYbrid Particle And Concentration Transport (HYPACT), and Rocket Exhaust Effluent Dispersion Model (REEDM). The primary observations used for explosion cloud verification of the study were from the National Weather Service's Weather Surveillance Radar 1988-Doppler (WSR-88D). Radar reflectivity measurements of the resulting cloud provided good estimates of the location and dimensions of the cloud over a four-hour period after the explosion. The results indicated that RAMS and HYPACT models performed reasonably well. Future upgrades to ERDAS are recommended.

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.

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

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.

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.

Investigation of the vapour-plasma plume in the welding of titanium by high-power ytterbium fibre laser radiation

NASA Astrophysics Data System (ADS)

Bykovskiy, D. P.; Petrovskii, V. N.; Uspenskiy, S. A.

2015-03-01

The vapour-plasma plume produced in the welding of 6-mm thick VT-23 titanium alloy plates by ytterbium fibre laser radiation of up to 10 kW power is studied in the protective Ar gas medium. High-speed video filming of the vapour-plasma plume is used to visualise the processes occurring during laser welding. The coefficient of inverse bremsstrahlung by the welding plasma plume is calculated from the data of the spectrometric study.

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.

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.

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

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

Self-consistent modeling of laminar electrohydrodynamic plumes from ultra-sharp needles in cyclohexane

NASA Astrophysics Data System (ADS)

Becerra, Marley; Frid, Henrik; Vázquez, Pedro A.

2017-12-01

This paper presents a self-consistent model of electrohydrodynamic (EHD) laminar plumes produced by electron injection from ultra-sharp needle tips in cyclohexane. Since the density of electrons injected into the liquid is well described by the Fowler-Nordheim field emission theory, the injection law is not assumed. Furthermore, the generation of electrons in cyclohexane and their conversion into negative ions is included in the analysis. Detailed steady-state characteristics of EHD plumes under weak injection and space-charge limited injection are studied. It is found that the plume characteristics far from both electrodes and under weak injection can be accurately described with an asymptotic simplified solution proposed by Vazquez et al. ["Dynamics of electrohydrodynamic laminar plumes: Scaling analysis and integral model," Phys. Fluids 12, 2809 (2000)] when the correct longitudinal electric field distribution and liquid velocity radial profile are used as input. However, this asymptotic solution deviates from the self-consistently calculated plume parameters under space-charge limited injection since it neglects the radial variations of the electric field produced by a high-density charged core. In addition, no significant differences in the model estimates of the plume are found when the simulations are obtained either with the finite element method or with a diffusion-free particle method. It is shown that the model also enables the calculation of the current-voltage characteristic of EHD laminar plumes produced by electron field emission, with good agreement with measured values reported in the literature.

Optical ridge waveguides in Er3+/Yb3+ co-doped phosphate glass produced by ion irradiation combined with femtosecond laser ablation for guided-wave green and red upconversion emissions

NASA Astrophysics Data System (ADS)

Chen, Chen; He, Ruiyun; Tan, Yang; Wang, Biao; Akhmadaliev, Shavkat; Zhou, Shengqiang; de Aldana, Javier R. Vázquez; Hu, Lili; Chen, Feng

2016-01-01

This work reports on the fabrication of ridge waveguides in Er3+/Yb3+ co-doped phosphate glass by the combination of femtosecond laser ablation and following swift carbon ion irradiation. The guiding properties of waveguides have been investigated at 633 and 1064 nm through end face coupling arrangement. The refractive index profile on the cross section of the waveguide has been constructed. The propagation losses can be reduced considerably after annealing treatment. Under the optical pump laser at 980 nm, the upconversion emission of both green and red fluorescence has been realized through the ridge waveguide structures.

Difficulties in deciding whether to ablate patients with putatively "low-intermediate-risk" differentiated thyroid carcinoma: do guidelines mainly apply in the centres that produce them? Results of a retrospective, two-centre quality assurance study.

PubMed

Frangos, Savvas; Iakovou, Ioannis P; Marlowe, Robert J; Eftychiou, Nicolaos; Patsali, Loukia; Vanezi, Anna; Savva, Androulla; Mpalaris, Vassilis; Giannoula, Evanthia I

2015-12-01

We determined the reasons for radioiodine thyroid remnant ablation, and the procedure's necessity based on postsurgical remnant size, in patients with putatively "low-intermediate-risk" differentiated thyroid carcinoma (DTC). We identified key clinicopathological, treatment and remnant characteristics, and factors associated with remnant size in 336 patients with pT1/2, M0 DTC ablated during the period September 2010 to October 2013 at one Cypriot or one Greek referral centre. Clinicopathological/treatment characteristics were compiled from charts. Experienced nuclear medicine physicians rated the numbers/intensities of uptake foci in the thyroid bed on postablation planar scintigrams using scales of 0-4 points and 0-3 points, respectively. The product of these scores was taken as the "remnant score" that ranged from 0 (no remnant) to 12 (multiple remnants, intense uptake). DTC was predominantly papillary. The median [25th-75th percentile] longest primary tumour diameter was 1.0 cm [0.7-1.5 cm]. Despite favourable histotypes and primary tumour classifications, patients often had preablation characteristics suggesting elevated or uncertain risk: 31.0% of patients (104 of 336) had primary tumour multifocality, 22.0% (74) had confirmed cervical lymph node metastases, 37.2% (125) had unknown nodal status, and 38.1% (128) had antithyroglobulin antibody seropositivity. The median [25th-75th percentile] remnant score was 4 [2-6]; 39.9% of patients (134 of 336) had scores ≥6. For the entire cohort, T or N stages (r ≤ 0.174, P ≤ 0.05) correlated positively with the remnant score in a univariate Spearman analysis. The numbers of patients referred by the surgeon, cervical lymph nodes excised and metastatic nodes excised correlated negatively (r ≤ 0.243, P ≤ 0.038) with the remnant score, and the first two factors independently predicted the remnant score (P ≤ 0.037) in a multivariate analysis. Patients with putatively "low

When Boundary Layers Collide: Plumes v. Subduction Zones

NASA Astrophysics Data System (ADS)

Moresi, L. N.; Betts, P. G.; Miller, M. S.; Willis, D.; O'Driscoll, L.

2014-12-01

Many subduction zones retreat while hotspots remain sufficiently stable in the mantle to provide an approximate reference frame. As a consequence, the mantle can be thought of as an unusual convecting system which self-organises to promote frequent collisions of downgoing material with upwellings. We present three 3D numerical models of subduction where buoyant material from a plume head and an associated ocean-island chain or plateau produce flat slab subduction and deformation of the over-riding plate. We observe transient instabilities of the convergent margin including: contorted trench geometry; trench migration parallel with the plate margin; folding of the subducting slab and orocline development at the convergent margin; and transfer of the plateau to the overriding plate. The presence of plume material beneath the oceanic plateau causes flat subduction above the plume, resulting in a "bowed" shaped subducting slab. In the absence of a plateau at the surface, the slab can remain uncoupled from the over-riding plate during very shallow subduction and hence there is very little shortening at the surface or advance of the plate boundary. In plateau-only models, plateau accretion at the edge of the overriding plate results in trench migration around the edge of the plateau before subduction re-establishes directly behind the trailing edge of the plateau. The plateau shortens during accretion and some plateau material subducts. In a plateau-plus-plume model, accretion is associated with rapid trench advance as the flat slab drives the plateau into the margin. This indentation stops once a new convergent boundary forms close to the original trench location. A slab window formed beneath the accreted plateau allows plume material to flow from beneath the subducting plate to the underside of the overriding plate. In all of these models the subduction zone maintains a relatively stable configuration away from the buoyancy anomalies within the downgoing plate. The

Investigations on laser hard tissue ablation under various environments

NASA Astrophysics Data System (ADS)

Kang, H. W.; Oh, J.; Welch, A. J.

2008-06-01

The purpose of this study was to investigate the effect of liquid environments upon laser bone ablation. A long-pulsed Er,Cr:YSGG laser was employed to ablate bovine bone tibia at various radiant exposures under dry, wet (using water or perfluorocarbon) and spray environmental conditions. Energy loss by the application of liquid during laser irradiation was evaluated, and ablation performance for all conditions was quantitatively measured by optical coherence tomography (OCT). Microscope images were also used to estimate thermal side effects in tissue after multiple-pulse ablation. Wet using water and spray conditions equally attenuated the 2.79 µm wavelength laser beam. Higher transmission efficiency was obtained utilizing a layer of perfluorocarbon. Dry ablation exhibited severe carbonization due to excessive heat accumulation. Wet condition using water resulted in similar ablation volume to the dry case without carbonization. The perfluorocarbon layer produced the largest ablation volume but some carbonization due to the poor thermal conductivity. Spray induced clean cutting with slightly reduced efficiency. Liquid-assisted ablation provided significant beneficial effects such as augmented material removal and cooling/cleaning effects during laser osteotomy.

Ablative Thermal Protection Systems Fundamentals

NASA Technical Reports Server (NTRS)

Beck, Robin A. S.

2017-01-01

This is a presentation of the fundamentals of ablative TPS materials for a short course at TFAWS 2017. It gives an overall description of what an ablator is, the equations that define it, and how to model it.

An algorithm for the detection and characterisation of volcanic plumes using thermal camera imagery

NASA Astrophysics Data System (ADS)

Bombrun, Maxime; Jessop, David; Harris, Andrew; Barra, Vincent

2018-02-01

Volcanic plumes are turbulent mixtures of particles and gas which are injected into the atmosphere during a volcanic eruption. Depending on the intensity of the eruption, plumes can rise from a few tens of metres up to many tens of kilometres above the vent and thus, present a major hazard for the surrounding population. Currently, however, few if any algorithms are available for automated plume tracking and assessment. Here, we present a new image processing algorithm for segmentation, tracking and parameters extraction of convective plume recorded with thermal cameras. We used thermal video of two volcanic eruptions and two plumes simulated in laboratory to develop and test an efficient technique for analysis of volcanic plumes. We validated our method by two different approaches. First, we compare our segmentation method to previously published algorithms. Next, we computed plume parameters, such as height, width and spreading angle at regular intervals of time. These parameters allowed us to calculate an entrainment coefficient and obtain information about the entrainment efficiency in Strombolian eruptions. Our proposed algorithm is rapid, automated while producing better visual outlines compared to the other segmentation algorithms, and provides output that is at least as accurate as manual measurements of plumes.

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.

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.

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.

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.

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

SciTech Connect

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

SSME Condition Monitoring Using Neural Networks and Plume Spectral Signatures

NASA Technical Reports Server (NTRS)

Hopkins, Randall; Benzing, Daniel

1996-01-01

code called SPECTRA, developed at the USAF Arnold Engineering Development Center. Ostensibly, the code produces intensity versus wavelength plots (i.e., spectra) when inputs such as element concentrations, reaction temperature, and reaction pressure are provided. However, in order to provide a higher-level analysis, element concentration is not specified explicitly as an input. Instead, two quantum variables, number density and broadening parameter, are used. Past experience with OPAD data analysis has revealed that the region of primary interest in any SSME plume spectrum lies in the wavelength band of 3300 A to 4330 A. Experience has also revealed that some elements, such as iron, cobalt and nickel, cause multiple peaks over the chosen wavelength range whereas other elements (magnesium, for example) have a few, relatively isolated peaks in the chosen wavelength range. Iteration with SPECTRA as a part of OPAD data analysis is an incredibly labor intensive task and not one to be performed by hand. What is really needed is the "inverse" of the computer code but the mathematical model for the inverse mapping is tenuous at best. However, building generalized models based upon known input/output mappings while ignoring details of the governing physical model is possible using neural networks. Thus the objective of the research project described herein was to quickly and accurately predict combustion temperature and element concentrations (i.e., number density and broadening parameter) from a given spectrum using a neural network. In other words, a neural network had to be developed that would provide a generalized "inverse" of the computer code SPECTRA.

[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.

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

Diagnosis and ablation of multiform fascicular tachycardia.

PubMed

Sung, Raphael K; Kim, Albert M; Tseng, Zian H; Han, Frederick; Inada, Keiichi; Tedrow, Usha B; Viswanathan, Mohan N; Badhwar, Nitish; Varosy, Paul D; Tanel, Ronn; Olgin, Jeffrey E; Stephenson, William G; Scheinman, Melvin

2013-03-01

Fascicular tachycardia (FT) is an uncommon cause of monomorphic sustained ventricular tachycardia (VT). We describe 6 cases of FT with multiform QRS morphologies. Six of 823 consecutive VT cases were retrospectively analyzed and found attributable to FT with multiform QRS patterns, with 3 cases exhibiting narrow QRS VT as well. All underwent electrophysiology study including fascicular potential mapping, entrainment pacing, and electroanatomic mapping. The first 3 cases describe similar multiform VT patterns with successful ablation in the upper mid septum. Initially, a right bundle branch block (RBBB) VT with superior axis was induced. Radiofrequency catheter ablation (RFCA) targeting the left posterior fascicle (LPF) resulted in a second VT with RBBB inferior axis. RFCA in the upper septum just apical to the LBB potential abolished VT in all cases. Cases 4 and 5 showed RBBB VT with alternating fascicular block compatible with upper septal dependent VT, resulting in bundle branch reentrant VT (BBRT) after ablation of LPF and left anterior fascicle (LAF). Finally, Cases 5 and 6 demonstrated spontaneous shift in QRS morphology during VT, implicating participation of a third fascicle. In Case 6, successful ablation was achieved over the proximal LAF, likely representing insertion of the auxiliary fascicle near the proximal LAF. Multiform FTs show a reentrant mechanism using multiple fascicular branches. We hypothesize that retrograde conduction over the septal fascicle produces alternate fascicular patterns as well as narrow VT forms. Ablation of the respective fascicle was successful in abolishing FT but does not preclude development of BBRT unless septal fascicle is targeted and ablated. © 2012 Wiley Periodicals, Inc.

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.

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

On the origin of extraterrestrial stratospheric particles: Interplanetary dust or meteor ablation debris?. M.S. Thesis

NASA Technical Reports Server (NTRS)

Kyte, F. T.

1977-01-01

Meteor ablation debris was distinguished from unablated interplanetary dust in a collection of extraterrestrial particles collected in the stratosphere using NASA U-2 aircraft. A 62 g sample of the Murchison (C2) meteorite was artificially ablated to characterize ablation debris for comparison with the stratospheric particles. By using proper experimental conditions, artificial ablation debris can be produced that is similar to natural ablation debris. Analyses of natural fusion crusts, artificial fusion crust, and artificial ablation debris of the Murchison meteorite produced criteria for recognizing debris ablated by a primitive meteoroid. Ninety-five percent of the stratospheric particles can be described as either ablation debris from a primitive meteoroid, or as very primitive interplanetary dust.

Advanced Rigid Ablative TPS

NASA Technical Reports Server (NTRS)

Gasch, Matthew J.

2011-01-01

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

Modelling ultrafast laser ablation

NASA Astrophysics Data System (ADS)

Rethfeld, Baerbel; Ivanov, Dmitriy S.; E Garcia, Martin; Anisimov, Sergei I.

2017-05-01

This review is devoted to the study of ultrafast laser ablation of solids and liquids. The ablation of condensed matter under exposure to subpicosecond laser pulses has a number of peculiar properties which distinguish this process from ablation induced by nanosecond and longer laser pulses. The process of ultrafast ablation includes light absorption by electrons in the skin layer, energy transfer from the skin layer to target interior by nonlinear electronic heat conduction, relaxation of the electron and ion temperatures, ultrafast melting, hydrodynamic expansion of heated matter accompanied by the formation of metastable states and subsequent formation of breaks in condensed matter. In case of ultrashort laser excitation, these processes are temporally separated and can thus be studied separately. As for energy absorption, we consider peculiarities of the case of metal irradiation in contrast to dielectrics and semiconductors. We discuss the energy dissipation processes of electronic thermal wave and lattice heating. Different types of phase transitions after ultrashort laser pulse irradiation as melting, vaporization or transitions to warm dense matter are discussed. Also nonthermal phase transitions, directly caused by the electronic excitation before considerable lattice heating, are considered. The final material removal occurs from the physical point of view as expansion of heated matter; here we discuss approaches of hydrodynamics, as well as molecular dynamic simulations directly following the atomic movements. Hybrid approaches tracing the dynamics of excited electrons, energy dissipation and structural dynamics in a combined simulation are reviewed as well.

Plume-induced roll back subduction around Venus large coronae

NASA Astrophysics Data System (ADS)

Davaille, A.; Smrekar, S. E.; Tomlinson, S. M.

2016-12-01

On Venus, possible subduction trenches are mainly associated with large coronae, eventhough the latter are thought to be produced by hot mantle plumes. The mechanism of assocation between subduction and plume has long remained elusive. However, we recently observe the same association in laboratory experiments on thermal convection in colloidal aqueous dispersions of silica nanoparticles, which deform in the Newtonian regime at low solid particle fraction φp, and transition to strain-rate weakening, plasticity, elasticity, and brittle properties as φp increases. Hence, a dense skin akin to a planetary lithosphere grows on the surface when the system is dried from above. When a hot plume rises under the skin, the latter undergoes a flexural deformation which puts it under tension. Cracks then develop, sometimes using pre-existing weaknesses. Plume material (being more buoyant that the laboratory lithosphere) upwells through the cracks and spreads as a axisymmetric gravity current above the broken denser skin. The latter bends and sinks under the conjugate action of its own weight and the plume gravity current. The brittle character of the top experimental lithosphere forbids it to deform viscously to accomodate the sinking motions. Instead, the plate continues to tear as a sheet of paper would do upon intrusion. Several slabs are therefore produced, associated with trenches localized along partial circles on the plume, and strong roll-back is always observed. Depending on the lithospheric strength, roll-back can continue and triggers a complete resurfacing, or it stops when the plume stops spreading. Scalings derived from the experiments suggest that a weaker lithosphere than that present on Earth today is required for such a convective regime. We identified two candidates on Venus. At Artemis and Quetzelpetlatl Coronae, the radar image observations and subsurface density variations inferred from modeling the gravity and topography agree with the predictions from

Improvements in Modeling Thruster Plume Erosion Damage to Spacecraft Surfaces

NASA Technical Reports Server (NTRS)

Soares, Carlos; Olsen, Randy; Steagall, Courtney; Huang, Alvin; Mikatarian, Ron; Myers, Brandon; Koontz, Steven; Worthy, Erica

2015-01-01

Spacecraft bipropellant thrusters impact spacecraft surfaces with high speed droplets of unburned and partially burned propellant. These impacts can produce erosion damage to optically sensitive hardware and systems (e.g., windows, camera lenses, solar cells and protective coatings). On the International Space Station (ISS), operational constraints are levied on the position and orientation of the solar arrays to mitigate erosion effects during thruster operations. In 2007, the ISS Program requested evaluation of erosion constraint relief to alleviate operational impacts due to an impaired Solar Alpha Rotary Joint (SARJ). Boeing Space Environments initiated an activity to identify and remove sources of conservatism in the plume induced erosion model to support an expanded range of acceptable solar array positions ? The original plume erosion model over-predicted plume erosion and was adjusted to better correlate with flight experiment results. This paper discusses findings from flight experiments and the methodology employed in modifying the original plume erosion model for better correlation of predictions with flight experiment data. The updated model has been successful employed in reducing conservatism and allowing for enhanced flexibility in ISS solar array operations.

Development of a Random Field Model for Gas Plume Detection in Multiple LWIR Images.

SciTech Connect

Heasler, Patrick G.

This report develops a random field model that describes gas plumes in LWIR remote sensing images. The random field model serves as a prior distribution that can be combined with LWIR data to produce a posterior that determines the probability that a gas plume exists in the scene and also maps the most probable location of any plume. The random field model is intended to work with a single pixel regression estimator--a regression model that estimates gas concentration on an individual pixel basis.

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.

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.

Volcanic tremor and plume height hysteresis from Pavlof Volcano, Alaska.

PubMed

Fee, David; Haney, Matthew M; Matoza, Robin S; Van Eaton, Alexa R; Cervelli, Peter; Schneider, David J; Iezzi, Alexandra M

2017-01-06

The March 2016 eruption of Pavlof Volcano, Alaska, produced an ash plume that caused the cancellation of more than 100 flights in North America. The eruption generated strong tremor that was recorded by seismic and remote low-frequency acoustic (infrasound) stations, including the EarthScope Transportable Array. The relationship between the tremor amplitudes and plume height changes considerably between the waxing and waning portions of the eruption. Similar hysteresis has been observed between seismic river noise and discharge during storms, suggesting that flow and erosional processes in both rivers and volcanoes can produce irreversible structural changes that are detectable in geophysical data. We propose that the time-varying relationship at Pavlof arose from changes in the tremor source related to volcanic vent erosion. This relationship may improve estimates of volcanic emissions and characterization of eruption size and intensity. Copyright © 2017, American Association for the Advancement of Science.

Volcanic tremor and plume height hysteresis from Pavlof Volcano, Alaska

NASA Astrophysics Data System (ADS)

Fee, David; Haney, Matthew M.; Matoza, Robin S.; Van Eaton, Alexa R.; Cervelli, Peter; Schneider, David J.; Iezzi, Alexandra M.

2017-01-01

The March 2016 eruption of Pavlof Volcano, Alaska, produced an ash plume that caused the cancellation of more than 100 flights in North America. The eruption generated strong tremor that was recorded by seismic and remote low-frequency acoustic (infrasound) stations, including the EarthScope Transportable Array. The relationship between the tremor amplitudes and plume height changes considerably between the waxing and waning portions of the eruption. Similar hysteresis has been observed between seismic river noise and discharge during storms, suggesting that flow and erosional processes in both rivers and volcanoes can produce irreversible structural changes that are detectable in geophysical data. We propose that the time-varying relationship at Pavlof arose from changes in the tremor source related to volcanic vent erosion. This relationship may improve estimates of volcanic emissions and characterization of eruption size and intensity.

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.

Impact of the Fraser River Geometry on Tides and the River Plumes in a Model of the Fraser River Plume

NASA Astrophysics Data System (ADS)

Liu, J.; Allen, S. E.; Soontiens, N. K.

2016-02-01

Fraser River is the largest river on the west coast of Canada. It empties into the Strait of Georgia, which is a large, semi-enclosed body of water between Vancouver Island and the mainland of British Columbia. We have developed a three-dimensional model of the Strait of Georgia, including the Fraser River plume, using the NEMO model in its regional configuration. This operational model produces daily nowcasts and forecasts for salinity, temperature, currents and sea surface heights. Observational data available for evaluation of the model includes daily British Columbia ferry salinity data, profile data and surface drifter data. The salinity of the modelled Fraser River plume agrees well with ferry based measurements of salinity. However, large discrepencies exist between the modelled and observed position of the plume. Modelled surface currents compared to drifter observations show that the model has too strong along-strait velocities and too weak cross-strait velocities. We investigated the impact of river geometry. A sensitivity experiment was performed comparing the original, short, shallow river channel to an extended and deepened river channel. With the latter bathymetry, tidal amplitudes within Fraser River correspond well with observations. Comparisons to drifter tracks show that the surface currents have been improved with the new bathymetry. However, substantial discrepencies remain. We will discuss how reducing vertical eddy viscosity and other changes further improve the modelled position of the plume.

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.

Microwave ablation devices for interventional oncology.

PubMed

Ward, Robert C; Healey, Terrance T; Dupuy, Damian E

2013-03-01

Microwave ablation is one of the several options in the ablation armamentarium for the treatment of malignancy, offering several potential benefits when compared with other ablation, radiation, surgical and medical treatment modalities. The basic microwave system consists of the generator, power distribution system and antennas. Often under image (computed tomography or ultrasound) guidance, a needle-like antenna is inserted percutaneously into the tumor, where local microwave electromagnetic radiation is emitted from the probe's active tip, producing frictional tissue heating, capable of causing cell death by coagulation necrosis. Half of the microwave ablation systems use a 915 MHz generator and the other half use a 2450 MHz generator. To date, there are no completed clinical trials comparing microwave devices head-to-head. Prospective comparisons of microwave technology with other treatment alternatives, as well as head-to-head comparison with each microwave device, is needed if this promising field will garner more widespread support and use in the oncology community.

An Inversion Method for Reconstructing Hall Thruster Plume Parameters from the Line Integrated Measurements (Postprint)

DTIC Science & Technology

2007-07-01

Technical Paper 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER An Inversion Method for Reconstructing Hall Thruster Plume...298 (Rev. 8-98) Prescribed by ANSI Std. 239.18 An Inversion Method for Reconstructing Hall Thruster Plume Parameters from Line Integrated Measurements... Hall thruster is a high specific impulse electric thruster that produces a highly ionized plasma inside an annular chamber through the use of high

Hyper-spectral imaging of aircraft exhaust plumes

NASA Astrophysics Data System (ADS)

Bowen, Spencer; Bradley, Kenneth; Gross, Kevin; Perram, Glen; Marciniak, Michael

2008-10-01

An imaging Fourier-transform spectrometer has been used to determine low spatial resolution temperature and chemical species concentration distributions of aircraft jet engine exhaust plumes. An overview of the imaging Fourier transform spectrometer and the methodology of the project is presented. Results to date are shared and future work is discussed. Exhaust plume data from a Turbine Technologies, LTD, SR-30 turbojet engine at three engine settings was collected using a Telops Field-portable Imaging Radiometric Spectrometer Technology Mid-Wave Extended (FIRST-MWE). Although the plume exhibited high temporal frequency fluctuations, temporal averaging of hyper-spectral data-cubes produced steady-state distributions, which, when co-added and Fourier transformed, produced workable spectra. These spectra were then reduced using a simplified gaseous effluent model to fit forward-modeled spectra obtained from the Line-By-Line Radiative Transfer Model (LBLRTM) and the high-resolution transmission (HITRAN) molecular absorption database to determine approximate temperature and concentration distributions. It is theorized that further development of the physical model will produce better agreement between measured and modeled data.

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.

Interferometric analysis of the ablation profile in refractive surgery

NASA Astrophysics Data System (ADS)

Rodríguez-Rodríguez, M. I.; López-Olazagasti, E.; Rosales, M. A.; Ramírez-Zavaleta, G.; Cantú, R.; Tepichín, E.

2008-08-01

In ophthalmology, the laser excimer corneal surface ablation used to correct the refractive eye defects, such as myopia, astigmatism and hyperopia and, more recently, presbyopia is known as refractive surgery. Typically, the characterization of the corresponding technique, as well as the laser accuracy, is performed by analyzing standard ablation profiles made on PMMA (polymethylmethacrylate) plates. A drawback of this technique is that those plates do not necessarily represent the dimensions of the cornea during the ablation. On the other hand, due to the time varying process of the eye aberrations, the direct eye refractometric measurements can produce some errors. We report in this work the interferometric analysis of the ablation profile obtained with refractive surgery, applied directly on a contact lens. In this case, the resultant ablation profile might be closer to the real profile as well as time invariant. We use, as a reference, a similar contact lens without ablation. The preliminary results of the characterization of the corresponding ablation profile are also presented.

DSMC Simulations of Irregular Source Geometries for Io's Pele Plume

NASA Astrophysics Data System (ADS)

McDoniel, William; Goldstein, D. B.; Varghese, P. L.; Trafton, L. M.; Buchta, D. A.; Freund, J.; Kieffer, S. W.

2010-10-01

Volcanic plumes on Io represent a complex rarefied flow into a near-vacuum in the presence of gravity. A 3D rarefied gas dynamics method (DSMC) is used to investigate the gas dynamics of such plumes, with a focus on the effects of source geometry on far-field deposition patterns. These deposition patterns, such as the deposition ring's shape and orientation, as well as the presence and shape of ash deposits around the vent, are linked to the shape of the vent from which the plume material arises. We will present three-dimensional simulations for a variety of possible vent geometries for Pele based on observations of the volcano's caldera. One is a curved line source corresponding to a Galileo IR image of a particularly hot region in the volcano's caldera and the other is a large area source corresponding to the entire lava lake at the center of the plume. The curvature of the former is seen to be sufficient to produce the features seen in observations of Pele's deposition pattern, but the particular orientation of the source is found to be such that it cannot match the orientation of these features on Io's surface. The latter corrects the error in orientation while losing some of the structure, suggesting that the actual source may correspond well with part of the shore of the lava lake. In addition, we are collaborating with a group at the University of Illinois at Urbana-Champaign to develop a hybrid method to link the continuum flow beneath Io's surface and very close to the vent to the more rarefied flow in the large volcanic plumes. This work was funded by NASA-PATM grant NNX08AE72G.

Comparison of microbubble presence in the right heart during mechanochemical and radiofrequency ablation for varicose veins.

PubMed

Moon, K H; Dharmarajah, B; Bootun, R; Lim, C S; Lane, Tra; Moore, H M; Sritharan, K; Davies, A H

2017-07-01

Objective Mechanochemical ablation is a novel technique for ablation of varicose veins utilising a rotating catheter and liquid sclerosant. Mechanochemical ablation and radiofrequency ablation have no reported neurological side-effect but the rotating mechanism of mechanochemical ablation may produce microbubbles. Air emboli have been implicated as a cause of cerebrovascular events during ultrasound-guided foam sclerotherapy and microbubbles in the heart during ultrasound-guided foam sclerotherapy have been demonstrated. This study investigated the presence of microbubbles in the right heart during varicose vein ablation by mechanochemical abaltion and radiofrequency abaltion. Methods Patients undergoing great saphenous vein ablation by mechanochemical abaltion or radiofrequency ablation were recruited. During the ablative procedure, the presence of microbubbles was assessed using transthoracic echocardiogram. Offline blinded image quantification was performed using International Consensus Criteria grading guidelines. Results From 32 recruited patients, 28 data sets were analysed. Eleven underwent mechanochemical abaltion and 17 underwent radiofrequency abaltion. There were no neurological complications. In total, 39% (11/28) of patients had grade 1 or 2 microbubbles detected. Thirty-six percent (4/11) of mechanochemical abaltion patients and 29% (5/17) of radiofrequency ablation patients had microbubbles with no significant difference between the groups ( p=0.8065). Conclusion A comparable prevalence of microbubbles between mechanochemical abaltion and radiofrequency ablation both of which are lower than that previously reported for ultrasound-guided foam sclerotherapy suggests that mechanochemical abaltion may not confer the same risk of neurological events as ultrasound-guided foam sclerotherapy for treatment of varicose veins.

Anchoring Atmospheric Density Models Using Observed Shuttle Plume Emissions

NASA Astrophysics Data System (ADS)

Dimpfl, W. L.; Bernstien, L. S.

2010-12-01

Atmospheric number densities at a given low-earth orbit (LEO) altitude can vary by more than an order of magnitude, depending on such parameters as diurnal variations and solar activity. The MSIS atmospheric model, which includes these dependent variables as input, is reported as being accurate to ±15%. Improvement to such models requires accurate direct atmospheric measurement. Here, a means of anchoring atmospheric models is offered through measuring the size and shape of atomic line or molecular band radiance resulting from the atmospheric interaction from rocket engine plumes or gas releases in LEO. Many discrete line or band emissions, ranging from the infrared to the ultraviolet may be suitable. For this purpose we are focusing on NH(A→X), centered at 316 nm. This emission is seen in the plumes of the Shuttle Orbiter PRCS engines, is expected in the plume of any amine fueled engine, and can be observed from remote sensors in space or on the ground. The atmospheric interaction of gas releases or plumes from spacecraft in LEO are understood by comparison of observed radiance with that predicted by Direct Simulation Monte Carlo (DSMC) models. The recent Extended Variable Hard Sphere (EVHS) improvements in treating hyperthermal collisions has produced exceptional agreement between measured and modeled steady-state Space Shuttle OMS and PRCS 190-250 nm Cameron band plume radiance from CO(a→X), which is understood to result from a combination of two- and three-step mechanisms. Radiance from NH(A→X) in far field plumes is understood to result from a simpler single-step process of the reaction of a minor plume species with atomic oxygen, making it more suitable for use in determining atmospheric density. It is recommended that direct retrofire burns of amine fueled engines be imaged in a narrow band from remote sensors to reveal atmospheric number density. In principal the simple measurement of the distance between the engine exit and the peak in the steady

Gaseous and Particulate Content of Laser Hair Removal Plume.

PubMed

Chuang, Gary S; Farinelli, William; Christiani, David C; Herrick, Robert F; Lee, Norman C Y; Avram, Mathew M

2016-12-01

Potentially harmful chemicals are released when tissues are vaporized. Laser hair removal (LHR) causes heating and often vaporization of hairs, producing both a signature malodorous plume and visible particulates. To characterize the chemical composition and quantify the ultrafine particle content of the plume generated during LHR. In the laser center of a large academic hospital, discarded terminal hairs from the trunk and extremities were collected from 2 adult volunteers. The hair samples were sealed in glass gas chromatography chambers and treated with a laser. The laser plume was analyzed by gas chromatography-mass spectrometry (GC-MS). During LHR treatment, two 6-L negative pressure canisters were used to capture 30 seconds of laser plume, and a portable condensation particle counter was used to measure ultrafine particulates (<1 µm). Ultrafine particle concentrations were measured within the treatment room, within the waiting room, and outside the building. The chemical content of the laser plume was analyzed with GC-MS and screened for aerosolized toxins using Environmental Protection Agency-certified methods. The ambient concentration of ultrafine particles during LHR was measured by condensation particle counters. Analysis with GC-MS identified 377 chemical compounds. Sixty-two of these compounds, of which 13 are known or suspected carcinogens and more than 20 are known environmental toxins, exhibited strong absorption peaks. During LHR, the portable condensation particle counters documented an 8-fold increase compared with the ambient room baseline level of ultrafine particle concentrations (ambient room baseline, 15 300 particles per cubic centimeter [ppc]; LHR with smoke evacuator, 129 376 ppc), even when a smoke evacuator was in close proximity (5.0 cm) to the procedure site. When the smoke evacuator was turned off for 30 seconds, there was a more than 26-fold increase in particulate count compared with ambient baseline levels (ambient baseline

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.

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.

Skylon Aerodynamics and SABRE Plumes

NASA Technical Reports Server (NTRS)

Mehta, Unmeel; Afosmis, Michael; Bowles, Jeffrey; Pandya, Shishir

2015-01-01

An independent partial assessment is provided of the technical viability of the Skylon aerospace plane concept, developed by Reaction Engines Limited (REL). The objectives are to verify REL's engineering estimates of airframe aerodynamics during powered flight and to assess the impact of Synergetic Air-Breathing Rocket Engine (SABRE) plumes on the aft fuselage. Pressure lift and drag coefficients derived from simulations conducted with Euler equations for unpowered flight compare very well with those REL computed with engineering methods. The REL coefficients for powered flight are increasingly less acceptable as the freestream Mach number is increased beyond 8.5, because the engineering estimates did not account for the increasing favorable (in terms of drag and lift coefficients) effect of underexpanded rocket engine plumes on the aft fuselage. At Mach numbers greater than 8.5, the thermal environment around the aft fuselage is a known unknown-a potential design and/or performance risk issue. The adverse effects of shock waves on the aft fuselage and plumeinduced flow separation are other potential risks. The development of an operational reusable launcher from the Skylon concept necessitates the judicious use of a combination of engineering methods, advanced methods based on required physics or analytical fidelity, test data, and independent assessments.

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

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

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

SciTech Connect

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

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

Bimodal electric tissue ablation (BETA) - in-vivo evaluation of the effect of applying direct current before and during radiofrequency ablation of porcine liver.

PubMed

Cockburn, J F; Maddern, G J; Wemyss-Holden, S A

2007-03-01

To examine the effect of applying increasing amounts of direct current (DC) before and during alternating current radiofrequency ablation of porcine liver. Using a Radiotherapeutics RF3000 generator, a 9 V AC/DC transformer and a 16 G plain aluminium tube as an electrode, a control group of 24 porcine hepatic radiofrequency ablation zones was compared with 24 zones created using a bimodal electric tissue ablation (BETA) technique in three pigs. All ablations were terminated when tissue impedance rose to greater than 999 Omega or radiofrequency energy input fell below 5 W on three successive measurements taken at 1 min intervals. BETA ablations were performed in two phases: an initial phase of variable duration DC followed by a second phase during which standard radiofrequency ablation was applied simultaneously with DC. During this second phase, radiofrequency power input was regulated by the feedback circuitry of the RF3000 generator according to changes in tissue impedance. The diameters (mm) of each ablation zone were measured by two observers in two planes perpendicular to the plane of needle insertion. The mean short axis diameter of each ablation zone was subjected to statistical analysis. With increased duration of prior application of DC, there was a progressive increase in the diameter of the ablation zone (p<0.001). This effect increased sharply up to 300 s of pre-treatment after which a further increase in diameter occurred, but at a much lesser rate. A maximum ablation zone diameter of 32 mm was produced (control diameters 10-13 mm). Applying a 9 V DC to porcine liver in vivo, and continuing this DC application during subsequent radiofrequency ablation, results in larger ablation zone diameters compared with radiofrequency ablation alone.

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.

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...

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.

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...

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...

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.

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

A complex Ar⋯Agsbnd I produced by laser ablation and characterised by rotational spectroscopy and ab initio calculations: Variation of properties along the series Ar⋯Agsbnd X (X = F, Cl, Br and I)

NASA Astrophysics Data System (ADS)

Medcraft, Chris; Mullaney, John C.; Walker, Nicholas R.; Legon, Anthony C.

2017-05-01

A complex of argon with silver iodide (Ar⋯Agsbnd I) has been formed in the gas phase by laser ablation of a silver iodide rod in the presence of a pulse of argon gas and its ground-state rotational spectrum has been detected by means of a chirped-pulse, F-T microwave instrument. Ar⋯Agsbnd I was characterised both by experimental properties determined from its rotational spectrum and by ab initio calculations carried out at the CCSD(T)(F12c)/cc-pVTZ-F12 explicitly correlated level of theory. The molecule was shown to be linear in the ground state, with atoms in the order shown. The Ar⋯Ag and Agsbnd I bond lengths r0(Ar⋯Ag) = 2.6759 Å and r0(Agsbnd I) = 2.5356 Å, the dissociation energy De = 16.7 kJ mol-1 for the process Ar⋯Agsbnd I = Ar + Agsbnd I, the intermolecular quadratic stretching force constant FAr⋯Ag = F22 = 20.2(8) N m-1 and the increase 0.033 in the ionicity ic of Agsbnd I when it enters the complex are reported. The opportunity has been taken to compare the way in which these properties vary along the series Ar⋯Agsbnd X (X = F, Cl, Br and I).

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.

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

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

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.

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

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.

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.

Tracked 3D ultrasound in radio-frequency liver ablation

NASA Astrophysics Data System (ADS)

Boctor, Emad M.; Fichtinger, Gabor; Taylor, Russell H.; Choti, Michael A.

2003-05-01

Recent studies have shown that radio frequency (RF) ablation is a simple, safe and potentially effective treatment for selected patients with liver metastases. Despite all recent therapeutic advancements, however, intra-procedural target localization and precise and consistent placement of the tissue ablator device are still unsolved problems. Various imaging modalities, including ultrasound (US) and computed tomography (CT) have been tried as guidance modalities. Transcutaneous US imaging, due to its real-time nature, may be beneficial in many cases, but unfortunately, fails to adequately visualize the tumor in many cases. Intraoperative or laparoscopic US, on the other hand, provides improved visualization and target imaging. This paper describes a system for computer-assisted RF ablation of liver tumors, combining navigational tracking of a conventional imaging ultrasound probe to produce 3D ultrasound imaging with a tracked RF ablation device supported by a passive mechanical arm and spatially registered to the ultrasound volume.

Multiple target laser ablation system

DOEpatents

Mashburn, D.N.

1996-01-09

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

Multiple target laser ablation system

DOEpatents

Mashburn, Douglas N.

1996-01-01

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

Optics of the Offshore Columbia River Plume from Glider Observations and Satellite Imagery

NASA Astrophysics Data System (ADS)

Saldias, G.; Shearman, R. K.; Barth, J. A.; Tufillaro, N.

2016-02-01

The Columbia River (CR) is the largest source of freshwater along the U.S. Pacific coast. The resultant plume is often transported southward and offshore forming a large buoyant feature off Oregon and northern California in spring-summer - the offshore CR plume. Observations from autonomous underwater gliders and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite imagery are used to characterize the optics of the offshore CR plume off Newport, Oregon. Vertical sections, under contrasting river flow conditions, reveal a low-salinity and warm surface layer of 20-25 m (fresher in spring and warmer in summer), high Colored Dissolved Organic Matter (CDOM) concentration and backscatter, and associated with the base of the plume high chlorophyll fluorescence. Plume characteristics vary in the offshore direction as the warm and fresh surface layer thickens progressively to an average 30-40 m of depth 270-310 km offshore; CDOM, backscatter, and chlorophyll fluorescence decrease in the upper 20 m and increase at subsurface levels (30-50 m depth). MODIS normalized water-leaving radiance (nLw(λ)) spectra for CR plume cases show enhanced water-leaving radiance at green bands (as compared to no-CR plume cases) up to 154 km from shore. Farther offshore, the spectral shapes for both cases are very similar, and consequently, a contrasting color signature of low-salinity plume water is practically imperceptible from ocean color remote sensing. Empirical algorithms based on multivariate regression analyses of nLw(λ) plus Sea Surface Temperature (SST) data produce more accurate results detecting offshore plume waters than previous studies using single visible bands (e.g. adg(412) or nLw(555)).

An expert system for spectroscopic analysis of rocket engine plumes

NASA Technical Reports Server (NTRS)

Reese, Greg; Valenti, Elizabeth; Alphonso, Keith; Holladay, Wendy

1991-01-01

The expert system described in this paper analyzes spectral emissions of rocket engine exhaust plumes and shows major promise for use in engine health diagnostics. Plume emission spectroscopy is an important tool for diagnosing engine anomalies, but it is time-consuming and requires highly skilled personnel. The expert system was created to alleviate such problems. The system accepts a spectral plot in the form of wavelength vs intensity pairs and finds the emission peaks in the spectrum, lists the elemental emitters present in the data and deduces the emitter that produced each peak. The system consists of a conventional language component and a commercially available inference engine that runs on an Apple Macintosh computer. The expert system has undergone limited preliminary testing. It detects elements well and significantly decreases analysis time.

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

SciTech Connect

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

Pulsing of a focused mantle plume: Evidence from the distribution of foundation chain hotspot volcanism

NASA Astrophysics Data System (ADS)

O'Connor, John M.; Stoffers, Peter; Wijbrans, Jan R.

2002-05-01

Using the rare case of a hotspot chain crossing a fossil microplate, we reveal fundamental mantle plume characteristics by comparing hotspot volcanism in a sequence of contrasting tectonic settings. Key new 40Ar/39Ar ages show that the Foundation mantle plume pulses hot masses from depth with an apparent periodicity of one Myr. Synchronous magmatism over large distances indicates that masses associated with individual pulses are focused initially into similarly sized zones under the Pacific plate. Since the plume, spreading on impact with the lithosphere, influences a very wide area, apparently unconnected hotspot volcanism can be produced simultaneously across wide swaths, often crosscutting seamount chains. Our model might explain in part much of the midplate volcanism scattered across the Pacific seafloor indicating the episodic addition of significantly greater masses of plume material into the upper mantle than suggested by the narrowness of major seamount chains.

Models and observations of plume-ridge interaction in the South Atlantic and their implications for crustal thickness variations

NASA Astrophysics Data System (ADS)

Gassmöller, Rene; Steinberger, Bernhard; Dannberg, Juliane; Bredow, Eva; Torsvik, Trond

2015-04-01

Mantle plumes are thought to originate at thermal or thermo-chemical boundary layers, and since their origin is relatively fixed compared to plate motion they produce hotspot tracks at the position of their impingement. When plumes reach the surface close to mid-ocean ridges, they generate thicker oceanic crust due to their increased temperature and hence higher degree of melting. Observations of these thickness variations allow estimates about the buoyancy flux and excess temperature of the plume. One example is the interaction of the Tristan plume with the South Atlantic Mid-Ocean Ridge, however, conclusions about the plume properties are complicated by the fact that the Tristan plume track has both on- and off-ridge segments. In these cases, where a plume is overridden by a ridge, it is assumed that the plume flux has a lateral component towards the ridge (the plume is "captured" by the ridge). Additionally, sea floor spreading north of the Florianopolis Fracture Zone did not start until ~112 Ma - at least 15 Ma after the plume head arrival - while the Atlantic had already opened south of it. Therefore, the plume is influenced by the jump in lithosphere thickness across the Florianopolis Fracture zone. We present crustal thickness and plume tracks of a three-dimensional regional convection model of the upper mantle for the Tristan-South Atlantic ridge interaction. The model is created with the convection code ASPECT, which allows for adaptive finite-element meshes to resolve the fine-scale structures within a rising plume head in the presence of large viscosity variations. The boundary conditions of the model are prescribed from a coarser global mantle convection model and the results are compared against recently published models of crustal thickness in the South Atlantic and hotspot tracks in global moving hotspot reference frames. In particular, we investigate the influence of the overriding ridge on the plume head. Thus, our comparison between models of

Modeling surface trapped river plumes: A sensitivity study

USGS Publications Warehouse

Hyatt, Jason; Signell, Richard P.

2000-01-01

To better understand the requirements for realistic regional simulation of river plumes in the Gulf of Maine, we test the sensitivity of the Blumberg-Mellor hydrodynamic model to choice of advection scheme, grid resolution, and wind, using idealized geometry and forcing. The test case discharges 1500 m3/s of fresh water into a uniform 32 psu ocean along a straight shelf at 43?? north. The water depth is 15 m at the coast and increases linearly to 190 m at a distance 100 km offshore. Constant discharge runs are conducted in the presence of ambient alongshore current and with and without periodic alongshore wind forcing. Advection methods tested are CENTRAL, UPWIND, the standard Smolarkiewicz MPDATA and a recursive MPDATA scheme. For the no-wind runs, the UPWIND advection scheme performs poorly for grid resolutions typically used in regional simulations (grid spacing of 1-2 km, comparable to or slightly less than the internal Rossby radius, and vertical resolution of 10% of the water column), damping out much of the plume structure. The CENTRAL difference scheme also has problems when wind forcing is neglected, and generates too much structure, shedding eddies of numerical origin. When a weak 5 cm/s ambient current is present in the no-wind case, both the CENTRAL and standard MPDATA schemes produce a false fresh- and dense-water source just upstream of the river inflow due to a standing two-grid length oscillation in the salinity field. The recursive MPDATA scheme completely eliminates the false dense water source, and produces results closest to the grid-converged solution. The results are shown to be very sensitive to vertical grid resolution, and the presence of wind forcing dramatically changes the nature of the plume simulations. The implication of these idealized tests for realistic simulations is discussed, as well as ramifications on previous studies of idealized plume models.

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

Coastal pollution hazards in southern California observed by SAR imagery: stormwater plumes, wastewater plumes, and natural hydrocarbon seeps

NASA Technical Reports Server (NTRS)

Digiacomo, Paul M.; Washburn, Libe; Holt, Benjamin; Jones, Burton H.

2004-01-01

Stormwater runoff plumes, municipal wastewater plumes, and natural hydrocarbon seeps are important pollution hazards for the heavily populated Southern California Bight (SCB). Due to their small size, dynamic and episodic nature, these hazards are difficult to sample adequately using traditional in situ oceanographic methods. Complex coastal circulation and persistent cloud cover can further complicate detection and monitoring of these hazards. We use imagery from space-borne synthetic aperture radar (SAR), complemented by field measurements, to examine these hazards in the SCB. The hazards are detectable in SAR imagery because they deposit surfactants on the sea surface, smoothing capillary and small gravity waves to produce areas of reduced backscatter compared with the surrounding ocean. We suggest that high-resolution SAR, which obtains useful data regardless of darkness or cloud cover, could be an important observational tool for assessment and monitoring of coastal marine pollution hazards in the SCB and other urbanized coastal regions.

A Review of Laser Ablation Propulsion

SciTech Connect

Phipps, Claude; Bohn, Willy; Lippert, Thomas

Laser Ablation Propulsion is a broad field with a wide range of applications. We review the 30-year history of laser ablation propulsion from the transition from earlier pure photon propulsion concepts of Oberth and Saenger through Kantrowitz's original laser ablation propulsion idea to the development of air-breathing 'Lightcraft' and advanced spacecraft propulsion engines. The polymers POM and GAP have played an important role in experiments and liquid ablation fuels show great promise. Some applications use a laser system which is distant from the propelled object, for example, on another spacecraft, the Earth or a planet. Others use a laser thatmore » is part of the spacecraft propulsion system on the spacecraft. Propulsion is produced when an intense laser beam strikes a condensed matter surface and produces a vapor or plasma jet. The advantages of this idea are that exhaust velocity of the propulsion engine covers a broader range than is available from chemistry, that it can be varied to meet the instantaneous demands of the particular mission, and that practical realizations give lower mass and greater simplicity for a payload delivery system. We review the underlying theory, buttressed by extensive experimental data. The primary problem in laser space propulsion theory has been the absence of a way to predict thrust and specific impulse over the transition from the vapor to the plasma regimes. We briefly discuss a method for combining two new vapor regime treatments with plasma regime theory, giving a smooth transition from one regime to the other. We conclude with a section on future directions.« less

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.

Improved Ablative Materials

DTIC Science & Technology

1967-12-01

Equipment 62 2. Gas Analysis 62 3. Chemical Analysis for Titanium and Boron 63 4. Tensile Strength Determinations 64 5. Density Determinations 64 6. X-ray...mils, and its density was about 4. 45 g/cm 3. Elastic modulus values averaged about 71 x 106 psi for the filament. -X- I. INTRODUCTION Ablative liner...20 4 /50 percent N 2H 4 -50 percent UDMH or L0 2 /LH. The more-energetic propellant systems, using fluorine or FLOX, demand more-effective abla- tive

High temperature ablative foam

NASA Technical Reports Server (NTRS)

Liu, Matthew T. (Inventor)

1992-01-01

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

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

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.

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.

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

[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.

Analysis of ablation debris from natural and artificial iron meteorites

NASA Technical Reports Server (NTRS)

Blanchard, M. B.; Davis, A. S.

1977-01-01

Artificial ablation studies were performed on iron and nickel-iron samples using an arc-heated plasma of ionized air. Experiment conditions simulated a meteoroid traveling about 12 km/sec at an altitude of 70 km. The artificially produced fusion crusts and ablation debris show features very similar to natural fusion crusts of the iron meteorites Boguslavka, Norfork, and N'Kandhla and to magnetic spherules recovered from Mn nodules. X-ray diffraction, electron microprobe, optical, and scanning electron microscope analyses reveal that important mineralogical, elemental, and textural changes occur during ablation. Some metal is melted and ablated. The outer margin of the melted rind is oxidized and recrystallizes as a discontinuous crust of magnetite and wustite. Adjacent to the oxidized metallic ablation zone is an unoxidized metallic ablation zone in which structures such as Widmannstatten bands are obliterated as the metal is transformed to unequilibrated alpha 2 nickel-iron. Volatile elements are vaporized and less volatile elements undergo fractionation.

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

NASA Astrophysics Data System (ADS)

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

2015-03-01

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

Simulation of Pellet Ablation

NASA Astrophysics Data System (ADS)

Parks, P. B.; Ishizaki, Ryuichi

2000-10-01

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

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.

Computational Plume Modeling of COnceptual ARES Vehicle Stage Tests

NASA Technical Reports Server (NTRS)

Allgood, Daniel C.; Ahuja, Vineet

2007-01-01

The plume-induced environment of a conceptual ARES V vehicle stage test at the NASA Stennis Space Center (NASA-SSC) was modeled using computational fluid dynamics (CFD). A full-scale multi-element grid was generated for the NASA-SSC B-2 test stand with the ARES V stage being located in a proposed off-center forward position. The plume produced by the ARES V main power plant (cluster of five RS-68 LOX/LH2 engines) was simulated using a multi-element flow solver - CRUNCH. The primary objective of this work was to obtain a fundamental understanding of the ARES V plume and its impingement characteristics on the B-2 flame-deflector. The location, size and shape of the impingement region were quantified along with the un-cooled deflector wall pressures, temperatures and incident heating rates. Issues with the proposed tests were identified and several of these addressed using the CFD methodology. The final results of this modeling effort will provide useful data and boundary conditions in upcoming engineering studies that are directed towards determining the required facility modifications for ensuring safe and reliable stage testing in support of the Constellation Program.

Models and Observations of Plume-Ridge Interaction in the South Atlantic and their Implications for Crustal Thickness Variations

NASA Astrophysics Data System (ADS)

Gassmoeller, R.; Dannberg, J.; Steinberger, B. M.; Bredow, E.; Torsvik, T. H.

2015-12-01

Mantle plumes are thought to originate at thermal or thermo-chemical boundary layers, and since their origin is relatively fixed compared to plate motion they produce hotspot tracks at the position of their impingement. When plumes reach the surface close to mid-ocean ridges, they generate thicker oceanic crust due to their increased temperature and hence higher degree of melting. Observations of these thickness variations allow estimates about the buoyancy flux and excess temperature of the plume. One example is the interaction of the Tristan plume with the South Atlantic Mid-Ocean Ridge, however, conclusions about the plume properties are complicated by the fact that the Tristan plume track has both on- and off-ridge segments. In these cases, where a plume is overridden by a ridge, it is assumed that the plume flux has a lateral component towards the ridge (the plume is "captured" by the ridge). Additionally, sea floor spreading north of the Florianopolis Fracture Zone did not start until 112 Ma -- at least 15 Ma after the plume head arrival -- while the Atlantic had already opened south of it. Therefore, the plume is influenced by the jump in lithosphere thickness across the Florianopolis Fracture zone.We present crustal thickness and plume tracks of a three-dimensional regional convection model of the upper mantle for the Tristan-South Atlantic ridge interaction. The model is created with the convection code ASPECT, which allows for adaptive finite-element meshes to resolve the fine-scale structures within a rising plume head in the presence of large viscosity variations. The boundary conditions of the model are prescribed from a coarser global mantle convection model and the results are compared against recently published models of crustal thickness in the South Atlantic and hotspot tracks in global moving hotspot reference frames. In particular, we investigate the influence of the overriding ridge on the plume head.Thus, our comparison between models of plume

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.

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...

Optimum Laser Beam Characteristics for Achieving Smoother Ablations in Laser Vision Correction.

PubMed

Verma, Shwetabh; Hesser, Juergen; Arba-Mosquera, Samuel

2017-04-01

Controversial opinions exist regarding optimum laser beam characteristics for achieving smoother ablations in laser-based vision correction. The purpose of the study was to outline a rigorous simulation model for simulating shot-by-shot ablation process. The impact of laser beam characteristics like super Gaussian order, truncation radius, spot geometry, spot overlap, and lattice geometry were tested on ablation smoothness. Given the super Gaussian order, the theoretical beam profile was determined following Lambert-Beer model. The intensity beam profile originating from an excimer laser was measured with a beam profiler camera. For both, the measured and theoretical beam profiles, two spot geometries (round and square spots) were considered, and two types of lattices (reticular and triangular) were simulated with varying spot overlaps and ablated material (cornea or polymethylmethacrylate [PMMA]). The roughness in ablation was determined by the root-mean-square per square root of layer depth. Truncating the beam profile increases the roughness in ablation, Gaussian profiles theoretically result in smoother ablations, round spot geometries produce lower roughness in ablation compared to square geometry, triangular lattices theoretically produce lower roughness in ablation compared to the reticular lattice, theoretically modeled beam profiles show lower roughness in ablation compared to the measured beam profile, and the simulated roughness in ablation on PMMA tends to be lower than on human cornea. For given input parameters, proper optimum parameters for minimizing the roughness have been found. Theoretically, the proposed model can be used for achieving smoothness with laser systems used for ablation processes at relatively low cost. This model may improve the quality of results and could be directly applied for improving postoperative surface quality.

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.

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

Interactive Volumetry Of Liver Ablation Zones.

PubMed

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

2015-10-20

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

Interactive Volumetry Of Liver Ablation Zones

PubMed Central

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

2015-01-01

Percutaneous radiofrequency ablation (RFA) is a minimally invasive technique that destroys cancer cells by heat. The heat results from focusing energy in the radiofrequency spectrum through a needle. Amongst others, this can enable the treatment of patients who are not eligible for an open surgery. However, the possibility of recurrent liver cancer due to incomplete ablation of the tumor makes post-interventional monitoring via regular follow-up scans mandatory. These scans have to be carefully inspected for any conspicuousness. Within this study, the RF ablation zones from twelve post-interventional CT acquisitions have been segmented semi-automatically to support the visual inspection. An interactive, graph-based contouring approach, which prefers spherically shaped regions, has been applied. For the quantitative and qualitative analysis of the algorithm’s results, manual slice-by-slice segmentations produced by clinical experts have been used as the gold standard (which have also been compared among each other). As evaluation metric for the statistical validation, the Dice Similarity Coefficient (DSC) has been calculated. The results show that the proposed tool provides lesion segmentation with sufficient accuracy much faster than manual segmentation. The visual feedback and interactivity make the proposed tool well suitable for the clinical workflow. PMID:26482818

Interactive Volumetry Of Liver Ablation Zones

NASA Astrophysics Data System (ADS)

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

2015-10-01

Percutaneous radiofrequency ablation (RFA) is a minimally invasive technique that destroys cancer cells by heat. The heat results from focusing energy in the radiofrequency spectrum through a needle. Amongst others, this can enable the treatment of patients who are not eligible for an open surgery. However, the possibility of recurrent liver cancer due to incomplete ablation of the tumor makes post-interventional monitoring via regular follow-up scans mandatory. These scans have to be carefully inspected for any conspicuousness. Within this study, the RF ablation zones from twelve post-interventional CT acquisitions have been segmented semi-automatically to support the visual inspection. An interactive, graph-based contouring approach, which prefers spherically shaped regions, has been applied. For the quantitative and qualitative analysis of the algorithm’s results, manual slice-by-slice segmentations produced by clinical experts have been used as the gold standard (which have also been compared among each other). As evaluation metric for the statistical validation, the Dice Similarity Coefficient (DSC) has been calculated. The results show that the proposed tool provides lesion segmentation with sufficient accuracy much faster than manual segmentation. The visual feedback and interactivity make the proposed tool well suitable for the clinical workflow.

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

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

Small explosive volcanic plume dynamics: insights from feature tracking velocimetry at Santiaguito lava dome

NASA Astrophysics Data System (ADS)

Benage, M. C.; Andrews, B. J.

2016-12-01

Volcanic explosions eject turbulent, transient jets of hot volcanic gas and particles into the atmosphere. Though the jet of hot material is initially negatively buoyant, the jet can become buoyant through entrainment and subsequent thermal expansion of entrained air that allows the eruptive plume to rise several kilometers. Although basic plume structure is qualitatively well known, the velocity field and dynamic structure of volcanic plumes are not well quantified. An accurate and quantitative description of volcanic plumes is essential for hazard assessments, such as if the eruption will form a buoyant plume that will affect aviation or produce dangerous pyroclastic density currents. Santa Maria volcano, in Guatemala, provides the rare opportunity to safely capture video of Santiaguito lava dome explosions and small eruptive plumes. In January 2016, two small explosions (< 2 km) that lasted several minutes and with little cloud obstruction were recorded for image analysis. The volcanic plume structure is analyzed through sequential image frames from the video where specific features are tracked using a feature tracking velocimetry (FTV) algorithm. The FTV algorithm quantifies the 2D apparent velocity fields along the surface of the plume throughout the duration of the explosion. Image analysis of small volcanic explosions allows us to examine the maximum apparent velocities at two heights above the dome surface, 0-25 meters, where the explosions first appear, and 100-125 meters. Explosions begin with maximum apparent velocities of <15 m/s. We find at heights near the dome surface and 10 seconds after explosion initiation, the maximum apparent velocities transition to sustained velocities of 5-15 m/s. At heights 100-125 meters above the dome surface, the apparent velocities transition to sustained velocities of 5-15 m/s after 25 seconds. Throughout the explosion, transient velocity maximums can exceed 40 m/s at both heights. Here, we provide novel quantification

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

RELATIVE ABUNDANCE MEASUREMENTS IN PLUMES AND INTERPLUMES

SciTech Connect

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

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.

Ablation of steel by microsecond pulse trains

NASA Astrophysics Data System (ADS)

Windeler, Matthew Karl Ross

Laser micromachining is an important material processing technique used in industry and medicine to produce parts with high precision. Control of the material removal process is imperative to obtain the desired part with minimal thermal damage to the surrounding material. Longer pulsed lasers, with pulse durations of milli- and microseconds, are used primarily for laser through-cutting and welding. In this work, a two-pulse sequence using microsecond pulse durations is demonstrated to achieve consistent material removal during percussion drilling when the delay between the pulses is properly defined. The light-matter interaction moves from a regime of surface morphology changes to melt and vapour ejection. Inline coherent imaging (ICI), a broadband, spatially-coherent imaging technique, is used to monitor the ablation process. The pulse parameter space is explored and the key regimes are determined. Material removal is observed when the pulse delay is on the order of the pulse duration. ICI is also used to directly observe the ablation process. Melt dynamics are characterized by monitoring surface changes during and after laser processing at several positions in and around the interaction region. Ablation is enhanced when the melt has time to flow back into the hole before the interaction with the second pulse begins. A phenomenological model is developed to understand the relationship between material removal and pulse delay. Based on melt refilling the interaction region, described by logistic growth, and heat loss, described by exponential decay, the model is fit to several datasets. The fit parameters reflect the pulse energies and durations used in the ablation experiments. For pulse durations of 50 us with pulse energies of 7.32 mJ +/- 0.09 mJ, the logisitic growth component of the model reaches half maximum after 8.3 mus +/- 1.1 us and the exponential decays with a rate of 64 mus +/- 15 us. The phenomenological model offers an interpretation of the material

Magnetotelluric Detection Thresholds as a Function of Leakage Plume Depth, TDS and Volume

SciTech Connect

Yang, X.; Buscheck, T. A.; Mansoor, K.

We conducted a synthetic magnetotelluric (MT) data analysis to establish a set of specific thresholds of plume depth, TDS concentration and volume for detection of brine and CO 2 leakage from legacy wells into shallow aquifers in support of Strategic Monitoring Subtask 4.1 of the US DOE National Risk Assessment Partnership (NRAP Phase II), which is to develop geophysical forward modeling tools. 900 synthetic MT data sets span 9 plume depths, 10 TDS concentrations and 10 plume volumes. The monitoring protocol consisted of 10 MT stations in a 2×5 grid laid out along the flow direction. We model the MTmore » response in the audio frequency range of 1 Hz to 10 kHz with a 50 Ωm baseline resistivity and the maximum depth up to 2000 m. Scatter plots show the MT detection thresholds for a trio of plume depth, TDS concentration and volume. Plumes with a large volume and high TDS located at a shallow depth produce a strong MT signal. We demonstrate that the MT method with surface based sensors can detect a brine and CO 2 plume so long as the plume depth, TDS concentration and volume are above the thresholds. However, it is unlikely to detect a plume at a depth larger than 1000 m with the change of TDS concentration smaller than 10%. Simulated aquifer impact data based on the Kimberlina site provides a more realistic view of the leakage plume distribution than rectangular synthetic plumes in this sensitivity study, and it will be used to estimate MT responses over simulated brine and CO 2 plumes and to evaluate the leakage detectability. Integration of the simulated aquifer impact data and the MT method into the NRAP DREAM tool may provide an optimized MT survey configuration for MT data collection. This study presents a viable approach for sensitivity study of geophysical monitoring methods for leakage detection. The results come in handy for rapid assessment of leakage detectability.« less

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

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.

Dust ablation in Pluto's atmosphere

NASA Astrophysics Data System (ADS)

Horanyi, Mihaly; Poppe, Andrew; Sternovsky, Zoltan

2016-04-01

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

Accuracy of entrainment coefficients in one-dimensional volcanic plume models

NASA Astrophysics Data System (ADS)

McNeal, J. S.; Freedland, G.; Cal, R. B.; Mastin, L. G.; Solovitz, S.

2017-12-01

During and after volcanic eruptions, ash clouds can present a danger to human activities, notably to air travel. Ash dispersal models can forecast the location and downwind path of the ash cloud, which are critical for mitigating potential threats. The accuracy of the ash dispersal model depends on the reliability of input parameters, one of which is the mass eruption rate (MER). Uncertainties in MER translate to uncertainties in forecasts of ash-cloud concentration. One-dimensional plume models can quickly estimate the MER from plume height, relying on empirical entrainment coefficients, α and β, which describe air inflow perpendicular and parallel to the centerline of the plume, respectively. While much work has been done to quantify α for strong plumes (0.06-0.09 in most cases), consensus has not been reached for α and β in moderate to weak plumes (i.e. plumes bent over by the wind). We conducted high precision jet entrainment measurements in a wind tunnel using particle image velocimetry (PIV). Observed centerline trajectories were compared to modeled ones using the one-dimensional plume model Plumeria. Test conditions produced Reynolds numbers (Re) on the order of 103 to 105 and jet-to-cross flow velocity ratios (Vr) from 6 to 34. Over this range, α and β were adjusted to match the modeled trajectories with measured ones. Additionally, we compared historical observations of plume height and MER during volcanic eruptions against Plumeria predictions. Uncertainties in MER were considered with additional model simulations to quantify their impact on the optimal entrainment coefficients. Our comparisons reveal a clear linear α-β relationship, where multiple α and β values could be found that produced accurate plume height predictions. For example, similar accuracy was found using both (α,β) = (0.07,0.35) and (α,β) = (0.04,0.95) for the test case based on the 2002 eruption of Reventador volcano in Ecuador. However, in some cases that we studied, the

Pele Plume Deposit on Io

NASA Technical Reports Server (NTRS)

1997-01-01

The varied effects of Ionian volcanism can be seen in this false color infrared composite image of Io's trailing hemisphere. Low resolution color data from Galileo's first orbit (June, 1996) have been combined with a higher resolution clear filter picture taken on the third orbit (November, 1996) of the spacecraft around Jupiter.

A diffuse ring of bright red material encircles Pele, the site of an ongoing, high velocity volcanic eruption. Pele's plume is nearly invisible, except in back-lit photographs, but its deposits indicate energetic ejection of sulfurous materials out to distances more than 600 kilometers from the central vent. Another bright red deposit lies adjacent to Marduk, also a currently active ediface. High temperature hot spots have been detected at both these locations, due to the eruption of molten material in lava flows or lava lakes. Bright red deposits on Io darken and disappear within years or decades of deposition, so the presence of bright red materials marks the sites of recent volcanism.

This composite was created from data obtained by the Solid State Imaging (CCD) system aboard NASA's Galileo spacecraft. The region imaged is centered on 15 degrees South, 224 degrees West, and is almost 2400 kilometers across. The finest details that can be discerned in this picture are about 3 kilometers across. North is towards the top of the picture and the sun illuminates the surface from the west.

The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

Plume Image Profiling of UV Laser Desorbed Biomolecules

NASA Astrophysics Data System (ADS)

Merrigan, T. L.; Hunniford, C. A.; Timson, D. J.; Catney, M.; McCullough, R. W.

2008-12-01

An experimental system, based upon the techniques of UV and IR laser desorption with time of flight mass spectrometry, has been constructed to enable the production and characterization of neutral biomolecular targets. The feasibility of the laser desorption technique for the purpose of radiation interaction experiments is investigated here. Fluorescent dye tagging and laser induced fluorescence imaging has been used to help characterize the laser produced plumes of biomolecules revealing their spatial density profiles and temporal evolution. Peak target thicknesses of 2×1012 molecules cm-2 were obtained 30 μs after laser desorption.

Microbial populations in contaminant plumes

NASA Astrophysics Data System (ADS)

Haack, Sheridan K.; Bekins, Barbara A.

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. La biodégradation efficace des polluants souterrains requiert deux éléments: des populations microbiennes possédant les aptitudes nécessaires à la dégradation, et des conditions géochimiques et hydrologiques souterraines favorables. Des contraintes pratiques sur la conception et l'interprétation des expériences à la fois en microbiologie et en hydrogéologie ont conduit à une connaissance limitée des interactions entre les

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.

Ion acceleration enhanced by target ablation

SciTech Connect

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.

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

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.

Investigation of the vapour-plasma plume in the welding of titanium by high-power ytterbium fibre laser radiation

SciTech Connect

Bykovskiy, D P; Petrovskii, V N; Uspenskiy, S A

2015-03-31

The vapour-plasma plume produced in the welding of 6-mm thick VT-23 titanium alloy plates by ytterbium fibre laser radiation of up to 10 kW power is studied in the protective Ar gas medium. High-speed video filming of the vapour-plasma plume is used to visualise the processes occurring during laser welding. The coefficient of inverse bremsstrahlung by the welding plasma plume is calculated from the data of the spectrometric study. (interaction of laser radiation with matter)

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.

Ablation of aluminum nitride films by nanosecond and femtosecond laser pulses

NASA Astrophysics Data System (ADS)

Gruzdev, Vitaly; Tzou, Robert; Salakhutdinov, Ildar; Danylyuk, Yuriy; McCullen, Erik; Auner, Gregory

2009-02-01

We present results of comparative study of laser-induced ablation of AlN films with variable content of oxygen as a surface-doping element. The films deposited on sapphire substrate were ablated by a single nanosecond pulse at wavelength 248 nm, and by a single femtosecond pulse at wavelength 775 nm in air at normal pressure. Ablation craters were inspected by AFM and Nomarski high-resolution microscope. Irradiation by nanosecond pulses leads to a significant removal of material accompanied by extensive thermal effects, chemical modification of the films around the ablation craters and formation of specific defect structures next to the craters. Remarkable feature of the nanosecond experiments was total absence of thermo-mechanical fracturing near the edges of ablation craters. The femtosecond pulses produced very gentle ablation removing sub-micrometer layers of the films. No remarkable signs of thermal, thermo-mechanical or chemical effects were found on the films after the femtosecond ablation. We discuss mechanisms responsible for the specific ablation effects and morphology of the ablation craters.

Persistence of a Groundwater Contaminant Plume after Hydraulic Source Containment at a Chlorinated-Solvent Contaminated Site

PubMed Central

Matthieu, D.E.; Brusseau, M.L.; Guo, Z.; Plaschke, M.; Carroll, K.C.; Brinker, F.

2015-01-01

The objective of this study was to characterize the behavior of a groundwater contaminant (trichloroethene) plume after implementation of a source-containment operation at a site in Arizona. The plume resides in a quasi three-layer system comprising a sand/gravel unit bounded on the top and bottom by relatively thick silty clayey layers. The system was monitored for 60 months beginning at start-up in 2007 to measure the change in contaminant concentrations within the plume, the change in plume area, the mass of contaminant removed, and the integrated contaminant mass discharge. Concentrations of trichloroethene in groundwater pumped from the plume extraction wells have declined significantly over the course of operation, as have concentrations for groundwater sampled from 40 monitoring wells located within the plume. The total contaminant mass discharge associated with operation of the plume extraction wells peaked at 0.23 kg/d, decreased significantly within one year, and thereafter began an asymptotic decline to a current value of approximately 0.03 kg/d. Despite an 87% reduction in contaminant mass and a comparable 87% reduction in contaminant mass discharge for the plume, the spatial area encompassed by the plume has decreased by only approximately 50%. This is much less than would be anticipated based on ideal flushing and mass-removal behavior. Simulations produced with a simplified 3-D numerical model matched reasonably well to the measured data. The results of the study suggest that permeability heterogeneity, back diffusion, hydraulic factors associated with the specific well field system, and residual discharge from the source zone are all contributing to the observed persistence of the plume, as well as the asymptotic behavior currently observed for mass removal and for the reduction in contaminant mass discharge. PMID:26069436

GPS Signal Feature Analysis to Detect Volcanic Plume on Mount Etna

NASA Astrophysics Data System (ADS)

Cannavo', Flavio; Aranzulla, Massimo; Scollo, Simona; Puglisi, Giuseppe; Imme', Giuseppina

2014-05-01

Volcanic ash produced during explosive eruptions can cause disruptions to aviation operations and to population living around active volcanoes. Thus, detection of volcanic plume becomes a crucial issue to reduce troubles connected to its presence. Nowadays, the volcanic plume detection is carried out by using different approaches such as satellites, radars and lidars. Recently, the capability of GPS to retrieve volcanic plumes has been also investigated and some tests applied to explosive activity of Etna have demonstrated that also the GPS may give useful information. In this work, we use the permanent and continuous GPS network of the Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo (Italy) that consists of 35 stations located all around volcano flanks. Data are processed by the GAMIT package developed by Massachusetts Institute of Technology. Here we investigate the possibility to quantify the volcanic plume through the GPS signal features and to estimate its spatial distribution by means of a tomographic inversion algorithm. The method is tested on volcanic plumes produced during the lava fountain of 4-5 September 2007, already used to confirm if weak explosive activity may or may not affect the GPS signals.

CO2 plume management in saline reservoir sequestration

USGS Publications Warehouse

Frailey, S.M.; Finley, R.J.

2011-01-01

A significant difference between injecting CO2 into saline aquifers for sequestration and injecting fluids into oil reservoirs or natural gas into aquifer storage reservoirs is the availability and use of other production and injection wells surrounding the primary injection well(s). Of major concern for CO2 sequestration using a single well is the distribution of pressure and CO2 saturation within the injection zone. Pressure is of concern with regards to caprock integrity and potential migration of brine or CO2 outside of the injection zone, while CO2 saturation is of interest for storage rights and displacement efficiency. For oil reservoirs, the presence of additional wells is intended to maximize oil recovery by injecting CO2 into the same hydraulic flow units from which the producing wells are withdrawing fluids. Completing injectors and producers in the same flow unit increases CO2 throughput, maximizes oil displacement efficiency, and controls pressure buildup. Additional injectors may surround the CO2 injection well and oil production wells in order to provide external pressure to these wells to prevent the injected CO2 from migrating from the pattern between two of the producing wells. Natural gas storage practices are similar in that to reduce the amount of "cushion" gas and increase the amount of cycled or working gas, edge wells may be used for withdrawal of gas and center wells used for gas injection. This reduces loss of gas to the formation via residual trapping far from the injection well. Moreover, this maximizes the natural gas storage efficiency between the injection and production wells and reduces the areal extent of the natural gas plume. Proposed U.S. EPA regulations include monitoring pressure and suggest the "plume" may be defined by pressure in addition to the CO2 saturated area. For pressure monitoring, it seems that this can only be accomplished by injection zone monitoring wells. For pressure, these wells would not need to be very

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.

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.

Magnetic Resonance Mediated Radiofrequency Ablation.

PubMed

Hue, Yik-Kiong; Guimaraes, Alexander R; Cohen, Ouri; Nevo, Erez; Roth, Abraham; Ackerman, Jerome L

2018-02-01

To introduce magnetic resonance mediated radiofrequency ablation (MR-RFA), in which the MRI scanner uniquely serves both diagnostic and therapeutic roles. In MR-RFA scanner-induced RF heating is channeled to the ablation site via a Larmor frequency RF pickup device and needle system, and controlled via the pulse sequence. MR-RFA was evaluated with simulation of electric and magnetic fields to predict the increase in local specific-absorption-rate (SAR). Temperature-time profiles were measured for different configurations of the device in agar phantoms and ex vivo bovine liver in a 1.5 T scanner. Temperature rise in MR-RFA was imaged using the proton resonance frequency method validated with fiber-optic thermometry. MR-RFA was performed on the livers of two healthy live pigs. Simulations indicated a near tenfold increase in SAR at the RFA needle tip. Temperature-time profiles depended significantly on the physical parameters of the device although both configurations tested yielded temperature increases sufficient for ablation. Resected livers from live ablations exhibited clear thermal lesions. MR-RFA holds potential for integrating RF ablation tumor therapy with MRI scanning. MR-RFA may add value to MRI with the addition of a potentially disposable ablation device, while retaining MRI's ability to provide real time procedure guidance and measurement of tissue temperature, perfusion, and coagulation.

CT thermometry for cone-beam CT guided ablation

NASA Astrophysics Data System (ADS)

DeStefano, Zachary; Abi-Jaoudeh, Nadine; Li, Ming; Wood, Bradford J.; Summers, Ronald M.; Yao, Jianhua

2016-03-01

Monitoring temperature during a cone-beam CT (CBCT) guided ablation procedure is important for prevention of over-treatment and under-treatment. In order to accomplish ideal temperature monitoring, a thermometry map must be generated. Previously, this was attempted using CBCT scans of a pig shoulder undergoing ablation.1 We are extending this work by using CBCT scans of real patients and incorporating more processing steps. We register the scans before comparing them due to the movement and deformation of organs. We then automatically locate the needle tip and the ablation zone. We employ a robust change metric due to image noise and artifacts. This change metric takes windows around each pixel and uses an equation inspired by Time Delay Analysis to calculate the error between windows with the assumption that there is an ideal spatial offset. Once the change map is generated, we correlate change data with measured temperature data at the key points in the region. This allows us to transform our change map into a thermal map. This thermal map is then able to provide an estimate as to the size and temperature of the ablation zone. We evaluated our procedure on a data set of 12 patients who had a total of 24 ablation procedures performed. We were able to generate reasonable thermal maps with varying degrees of accuracy. The average error ranged from 2.7 to 16.2 degrees Celsius. In addition to providing estimates of the size of the ablation zone for surgical guidance, 3D visualizations of the ablation zone and needle are also produced.

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).

Crater Formation Due to Lunar Plume Impingement

NASA Technical Reports Server (NTRS)

Marsell, Brandon

2011-01-01

Thruster plume impingement on a surface comprised of small, loose particles may cause blast ejecta to be spread over a large area and possibly cause damage to the vehicle. For this reason it is important to study the effects of plume impingement and crater formation on surfaces like those found on the moon. Lunar soil, also known as regolith, is made up of fine granular particles on the order of 100 microns.i Whenever a vehicle lifts-off from such a surface, the exhaust plume from the main engine will cause the formation of a crater. This crater formation may cause laterally ejected mass to be deflected and possibly damage the vehicle. This study is a first attempt at analyzing the dynamics of crater formation due to thruster exhaust plume impingement during liftoff from the moon. Though soil erosion on the lunar surface is not considered, this study aims at examining the evolution of the shear stress along the lunar surface as the engine fires. The location of the regions of high shear stress will determine where the crater begins to form and will lend insight into how big the crater will be. This information will help determine the probability that something will strike the vehicle. The final sections of this report discuss a novel method for studying this problem that uses a volume of fluid (VOF)ii method to track the movement of both the exhaust plume and the eroding surface.

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.

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.

Plume and Pyroclast Dynamics Observed During a Submarine Explosive Eruption at NW Rota-1, Mariana arc

NASA Astrophysics Data System (ADS)

Deardorff, N.; Cashman, K. V.; Chadwick, W. W.; Embley, R. W.

2007-12-01

Strombolian submarine eruptions at 550-560 m water depth were observed in April, 2006 at NW Rota-1 volcano, Mariana arc. During six dives with the Jason II remotely operated vehicle observations made at close range documented a diverse and increasingly energetic range of activity. The initial dives observed lava extrusion followed by small, explosive bursts. Activity steadily increased to produce gas thrust jets, discrete thermals and eventually a sustained plume. Eruption video allowed analysis of submarine plume dynamics and depositional characteristics. Sustained plumes were white, billowy and coherent, measuring ~0.5-0.75m wide at their base and quickly spreading to >2m in diameter within ~2-3m above vent due to rapid seawater entrainment. Sustained, coherent plumes were observed rising >20-30m above the seafloor; the top of the plume was observed at ~490m b.s.l giving a total plume height of ~60-70m above the active vent. The initial ascent (<3-4 m) of plumes generated from explosive bursts was analyzed for ejection velocities (<4m/s), clast settling velocities (~0.38-0.72m/s), and changes in plume height and width. Gas thrust jets were determined to transition from momentum-driven plume rise to buoyancy-driven plumes, both visually and using rise velocities, at ~ 0.5-1 m above the vent. These data contrast with the dynamics of plumes generated in subaerial Strombolian eruptions, which maintain momentum-driven rise to ~ 100 meters (Patrick, 2007) above the vent, and illustrate the strong dampening effect of the overlying seawater. Ash and lapilli were observed falling out of the plume at heights >3-4m after being transported by the convecting plume and are assumed to have wider range of travel, vertically and laterally, and deposition. Most bomb-sized ejecta were carried vertically with the plume for 1-3m before falling out around the vent, indicating that the dense (~1700-2350 kg/m3) clasts were transported primarily within the momentum-driven part of the

Development of moldable carbonaceous materials for ablative rocket nozzles.

NASA Technical Reports Server (NTRS)

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

1972-01-01

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

Bioavailable nanoparticles obtained in laser ablation of a selenium target in water

SciTech Connect

Kuzmin, P G; Shafeev, Georgii A; Voronov, Valerii V

The process of producing colloidal solutions of selenium nanoparticles in water using the laser ablation method is described. The prospects of using nanoparticles of elementary selenium as a nutrition source of this microelement are discussed. (nanoparticles)

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

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.

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

NASA Technical Reports Server (NTRS)

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

2017-01-01

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

Laser ablation system, and method of decontaminating surfaces

DOEpatents

Ferguson, Russell L.; Edelson, Martin C.; Pang, Ho-ming

1998-07-14

A laser ablation system comprising a laser head providing a laser output; a flexible fiber optic cable optically coupled to the laser output and transmitting laser light; an output optics assembly including a nozzle through which laser light passes; an exhaust tube in communication with the nozzle; and a blower generating a vacuum on the exhaust tube. A method of decontaminating a surface comprising the following steps: providing an acousto-optic, Q-switched Nd:YAG laser light ablation system having a fiber optically coupled output optics assembly; and operating the laser light ablation system to produce an irradiance greater than 1.times.10.sup.7 W/cm.sup.2, and a pulse width between 80 and 170 ns.

Ablative Laser Propulsion Using Multi-Layered Material Systems

NASA Technical Reports Server (NTRS)

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

2002-01-01

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

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.

Ablating Atrial Fibrillation: Customizing Lesion Sets Guided by Rotor Mapping

PubMed Central

Zaman, Junaid A. B.; Narayan, Sanjiv M.

2015-01-01

Ablation occupies an increasing role in the contemporary management of atrial fibrillation (AF), but results are suboptimal, particularly for persistent AF. While an anatomic approach to ablation is a highly efficacious and safe method to isolate pulmonary vein (PV) triggers, recurrence of AF is not always associated with PV reconnection, and there is compelling evidence that non-PV sites sustain AF after it is triggered. Recent developments in wide-area mapping and signal processing now identify rotors in the vast majority of AF patients that sustain AF and whose elimination improves long-term freedom from AF in multicenter studies. Investigators have now demonstrated rotor and focal sources for AF that show many analogous properties between approaches: they lie in spatially reproducible regions temporally over hours to days, and they are amenable to targeted ablation. This review outlines the rationale and technical developments supporting this mechanistic paradigm for human AF, and discusses how rotor mapping may be implemented for individual patient customization of lesion sets. Mechanistic studies are required to explain why rotor elimination (or other ablation approaches) producing long-term elimination of AF may not always terminate AF acutely, how AF correlates with structural changes on magnetic resonance imaging, and how these findings can be integrated clinically with current ablation strategies to improve patient outcomes. PMID:26306123

Ablating Atrial Fibrillation: Customizing Lesion Sets Guided by Rotor Mapping.

PubMed

Zaman, Junaid A B; Narayan, Sanjiv M

2015-01-01

Ablation occupies an increasing role in the contemporary management of atrial fibrillation (AF), but results are suboptimal, particularly for persistent AF. While an anatomic approach to ablation is a highly efficacious and safe method to isolate pulmonary vein (PV) triggers, recurrence of AF is not always associated with PV reconnection, and there is compelling evidence that non-PV sites sustain AF after it is triggered. Recent developments in wide-area mapping and signal processing now identify rotors in the vast majority of AF patients that sustain AF and whose elimination improves long-term freedom from AF in multicenter studies. Investigators have now demonstrated rotor and focal sources for AF that show many analogous properties between approaches: they lie in spatially reproducible regions temporally over hours to days, and they are amenable to targeted ablation. This review outlines the rationale and technical developments supporting this mechanistic paradigm for human AF, and discusses how rotor mapping may be implemented for individual patient customization of lesion sets. Mechanistic studies are required to explain why rotor elimination (or other ablation approaches) producing long-term elimination of AF may not always terminate AF acutely, how AF correlates with structural changes on magnetic resonance imaging, and how these findings can be integrated clinically with current ablation strategies to improve patient outcomes.

Passive acoustic records of two vigorous bubble-plume methane seeps on the Oregon continental margin

NASA Astrophysics Data System (ADS)

Dziak, R. P.; Matsumoto, H.; Merle, S. G.; Embley, R. W.; Baumberger, T.; Hammond, S. R.

2016-12-01

We present preliminary analysis of the acoustic records of two bubble-plume methane seeps recorded by an autonomous hydrophone deployed during the E/V Nautilus expedition (NA072) in June 2016. The goal of the NA072 expedition was to use the Simrad 302 as a survey tool to map bubble plumes at a regional scale along the Oregon and northern California margins, followed by in situ investigation of bubble-plume sites using the ROV Hercules. The exploration carried out during NA072 resulted in the discovery of hundreds of new individual methane seep sites in water depths ranging from 125 to 1725 m depth. A Greenridge Acousonde 3B™ hydrophone was deployed via ROV within two vigorous bubble-plume sites. Despite persistent ship and ROV propeller noise, the acoustic signature of the bubble-plume can be seen in the hydrophone record as a broadband (0.5 - 4.5 kHz) series of short duration ( 0.2-0.5 msec) pulses that occur in clusters of dozens of pulses lasting 2-3 secs. Previous studies of the passive acoustics of seep bubble-plumes indicate sound is generated during bubble formation, where detachment of the gas bubble from the end of a tube or conduit causes the bubble to oscillate, producing sound. The peak frequency f (the zeroth oscillatory mode) and the bubble equivalent spherical radius r for a given pressure P are: f = (2πr)-1 [(3γP/ρ)]1/2 where γ is the ratio of gas specific heat at constant pressure to constant volume and ρ is the water density (Leifer and Tang, 2006). Thus the frequency of a bubble's oscillation is proportional to the bubble's volume, and therefore it may be possible to use our acoustic data to obtain an estimate of the volume of methane being released at these seafloor plume sites.

Three-dimensional simulation of gas and dust in Io's Pele plume

NASA Astrophysics Data System (ADS)

McDoniel, William J.; Goldstein, David B.; Varghese, Philip L.; Trafton, Laurence M.

2015-09-01

Io's giant Pele plume rises high above the moon's surface and produces a complex deposition pattern. We use the direct simulation Monte Carlo (DSMC) method to model the flow of SO2 gas and silicate ash from the surface of the lava lake, into the umbrella-shaped canopy of the plume, and eventually onto the surface where the flow leaves black "butterfly wings" surrounded by a large red ring. We show how the geometry of the lava lake, from which the gas is emitted, is responsible for significant asymmetry in the plume and for the shape of the red deposition ring by way of complicated gas-dynamic interactions between parts of the gas flow arising from different areas in the lava lake. We develop a model for gas flow in the immediate vicinity of the lava lake and use it to show that the behavior of ash particles of less than about 2 μm in diameter in the plume is insensitive to the details of how they are introduced into the flow because they are coupled to the gas at low altitudes. We simulate dust particles in the plume to show how particle size determines the distance from the lava lake at which particles deposit on the surface, and we use this dependence to find a size distribution of black dust particles in the plume that provides the best explanation for the observed black fans to the east and west of the lava lake. This best-fit particle size distribution suggests that there may be two distinct mechanisms of black dust creation at Pele, and when two log-normal distributions are fit to our results we obtain a mean particle diameter of 88 nm. We also propose a mechanism by which the condensible plume gas might overlay black dust in areas where black coloration is not observed and compare this to the observed overlaying of Pillanian dust by Pele's red ring.

Wildland fire emissions, carbon, and climate: Plume rise, atmospheric transport, and chemistry processes

Treesearch

Warren Heilman; Yongqiang Liu; Shawn Urbanski; Vladimir Kovalev; Robert Mickler

2014-01-01

This paper provides an overview and summary of the current state of knowledge regarding critical atmospheric processes that affect the distribution and concentrations of greenhouse gases and aerosols emitted from wildland fires or produced through subsequent chemical reactions in the atmosphere. These critical atmospheric processes include the dynamics of plume rise,...

Development and Validation of a Computational Model for Predicting the Behavior of Plumes from Large Solid Rocket Motors

NASA Technical Reports Server (NTRS)

Wells, Jason E.; Black, David L.; Taylor, Casey L.

2013-01-01

Exhaust plumes from large solid rocket motors fired at ATK's Promontory test site carry particulates to high altitudes and typically produce deposits that fall on regions downwind of the test area. As populations and communities near the test facility grow, ATK has become increasingly concerned about the impact of motor testing on those surrounding communities. To assess the potential impact of motor testing on the community and to identify feasible mitigation strategies, it is essential to have a tool capable of predicting plume behavior downrange of the test stand. A software package, called PlumeTracker, has been developed and validated at ATK for this purpose. The code is a point model that offers a time-dependent, physics-based description of plume transport and precipitation. The code can utilize either measured or forecasted weather data to generate plume predictions. Next-Generation Radar (NEXRAD) data and field observations from twenty-three historical motor test fires at Promontory were collected to test the predictive capability of PlumeTracker. Model predictions for plume trajectories and deposition fields were found to correlate well with the collected dataset.

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.

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.

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.

Optical emission spectroscopic study of plasma plumes generated by IR CO2 pulsed laser on carbon targets

NASA Astrophysics Data System (ADS)

Camacho, J. J.; Díaz, L.; Santos, M.; Reyman, D.; Poyato, J. M. L.

2008-05-01

Optical emission spectroscopy studies, in the spectral range ultraviolet-visible-near infrared (UV-Vis-NIR), were performed to investigate thermal and dynamical properties of a plume produced by laser ablation of a graphite target. Ablation is carried out using a high-power IR CO2 pulsed laser at λ = 9.621 µm, power density ranging from 0.22 to 5.36 GW cm-2 and air pressures around 4 Pa. The strong emission observed in the plasma region is mainly due to electronic relaxation of excited C, ionic fragments C+, C2+ and C3+ and molecular features of C2(d 3Πg-a 3Πu Swan band system). The medium-weak emission is mainly due to excited atomic N, H, O, ionic fragment C4+ and molecular features of C2( E\\,^1\\Sigma _g^+\\--A\\,^{1}\\Pi _u ; Freymark system), C2( D\\,^1\\Sigma _u^+\\--X\\,^1\\Sigma _g^+ ; Mulliken system), CN(D 2Π-A 2Π), C2(e 3Πg-a 3Πu Fox-Herzberg system), C2(C 1Πg-A 1Πu Deslandres-d'Azambuja system), OH(A 2Σ+-X 2Π), CH(C 2Σ+-X 2Π), NH(A 3Π-X 3Σ-), CN(B 2Σ+-X 2Σ+ violet system), CH(B 2Σ+-X 2Π), CH(A 2Δ-X 2Π), C2( A\\,^{1}\\Pi_u\\--X\\,^{1}\\Sigma ^{+}_g ; Phillips system) and CN(A 2Π-X 2Σ+ red system). An excitation temperature Texc = 23 000 ± 1900 K and electron densities in the range (0.6-5.6) × 1016 cm-3 were estimated by means of C+ ionic lines. The characteristics of the spectral emission intensities from different species have been investigated as functions of the ambient pressure and laser irradiance. Estimates of vibrational temperatures of C2 and CN electronically excited species under various laser irradiance conditions are made.

Analysis of Wien filter spectra from Hall thruster plumes.

PubMed

Huang, Wensheng; Shastry, Rohit

2015-07-01

A method for analyzing the Wien filter spectra obtained from the plumes of Hall thrusters is derived and presented. The new method extends upon prior work by deriving the integration equations for the current and species fractions. Wien filter spectra from the plume of the NASA-300M Hall thruster are analyzed with the presented method and the results are used to examine key trends. The new integration method is found to produce results slightly different from the traditional area-under-the-curve method. The use of different velocity distribution forms when performing curve-fits to the peaks in the spectra is compared. Additional comparison is made with the scenario where the current fractions are assumed to be proportional to the heights of peaks. The comparison suggests that the calculated current fractions are not sensitive to the choice of form as long as both the height and width of the peaks are accounted for. Conversely, forms that only account for the height of the peaks produce inaccurate results. Also presented are the equations for estimating the uncertainty associated with applying curve fits and charge-exchange corrections. These uncertainty equations can be used to plan the geometry of the experimental setup.

Constraints on Thermochemical Convection of the Mantle from Plume-related Observations

NASA Astrophysics Data System (ADS)

Zhong, S.

2005-05-01

Although geochemical observations have long suggested a layered mantle with more enriched mantle material in the bottom layer to provide a significant amount of heat to the top layer, the nature of such a layering remains unclear. An important observation that has been used to argue against the conventional layered mantle model (i.e., the layering at the 670 km depth) was the plume heat flux [Davies, 1999]. Plume heat flux is estimated as ~ 3.5 TW, or 10% of the surface heat flux [Davies, 1988; Sleep, 1990]. In this study, we demonstrate with 3-D spherical models of mantle convection with depth- and temperature-dependent viscosity that observed plume heat flux, plume excess temperature (<350°C), and upper mantle temperature (~ 1300°C) can pose important constraints on the layered mantle convection. We show that for a purely thermal convection model (i.e., a whole mantle convection), the observations of plume heat flux, plume excess temperature, and upper mantle temperature can be simultaneously explained only when internal heating rate is about 65%. For smaller internal heating rate, plume heat flux and plume excess temperature would be too large, and upper mantle temperature would be too small, compared with the observed. This suggests that for a whole mantle convection the CMB heat flux needs to be > 10 TW. For a core with no significant heat producing elements, such large CMB heat flux may lead to too rapid cooling of the core or a too young inner core. A layered mantle convection may help reduce the CMB heat flux. For layered convection models, we found that the top layer needs to be ~70% internally heated to explain the upper mantle temperature and plume-related observations, and this required internal heating ratio is insensitive to the layer thickness for the bottom layer (we used ~600 km and 1100 km thicknesses). This result suggests that heat generation rate for the bottom layer cannot be significantly larger (< a factor of 2) than that for the top layer

Spatial and temporal migration of a landfill leachate plume in alluvium

USGS Publications Warehouse

Masoner, Jason R.; Cozzarelli, Isabelle M.

2015-01-01

Leachate from unlined or leaky landfills can create groundwater contaminant plumes that last decades to centuries. Understanding the dynamics of leachate movement in space and time is essential for monitoring, planning and management, and assessment of risk to groundwater and surface-water resources. Over a 23.4-year period (1986–2010), the spatial extent of the Norman Landfill leachate plume increased at a rate of 7800 m2/year and expanded by 878 %, from an area of 20,800 m2 in 1986 to 203,400 m2 in 2010. A linear plume velocity of 40.2 m/year was calculated that compared favorably to a groundwater-seepage velocity of 55.2 m/year. Plume-scale hydraulic conductivity values representative of actual hydrogeological conditions in the alluvium ranged from 7.0 × 10−5 to 7.5 × 10−4 m/s, with a median of 2.0 × 10−4 m/s. Analyses of field-measured and calculated plume-scale hydraulic conductivity distributions indicate that the upper percentiles of field-measured values should be considered to assess rates of plume-scale migration, spreading, and biodegradation. A pattern of increasing Cl− concentrations during dry periods and decreasing Cl− concentrations during wet periods was observed in groundwater beneath the landfill. The opposite occurred in groundwater downgradient from the landfill; that is, Cl− concentrations in groundwater downgradient from the landfill decreased during dry periods and increased during wet periods. This pattern of changing Cl−concentrations in response to wet and dry periods indicates that the landfill retains or absorbs leachate during dry periods and produces lower concentrated leachate downgradient. During wet periods, the landfill receives more recharge which dilutes leachate in the landfill but increases leachate migration from the landfill and produces a more concentrated contaminant plume. This approach of quantifying plume expansion, migration, and concentration during variable hydrologic

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.

Kinetic electron model for plasma thruster plumes

NASA Astrophysics Data System (ADS)

Merino, Mario; Mauriño, Javier; Ahedo, Eduardo

2018-03-01

A paraxial model of an unmagnetized, collisionless plasma plume expanding into vacuum is presented. Electrons are treated kinetically, relying on the adiabatic invariance of their radial action integral for the integration of Vlasov's equation, whereas ions are treated as a cold species. The quasi-2D plasma density, self-consistent electric potential, and electron pressure, temperature, and heat fluxes are analyzed. In particular, the model yields the collisionless cooling of electrons, which differs from the Boltzmann relation and the simple polytropic laws usually employed in fluid and hybrid PIC/fluid plume codes.

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.

DSMC simulations of the Shuttle Plume Impingement Flight EXperiment(SPIFEX)

NASA Technical Reports Server (NTRS)

Stewart, Benedicte; Lumpkin, Forrest

2017-01-01

During orbital maneuvers and proximity operations, a spacecraft fires its thrusters inducing plume impingement loads, heating and contamination to itself and to any other nearby spacecraft. These thruster firings are generally modeled using a combination of Computational Fluid Dynamics (CFD) and DSMC simulations. The Shuttle Plume Impingement Flight EXperiment(SPIFEX) produced data that can be compared to a high fidelity simulation. Due to the size of the Shuttle thrusters this problem was too resource intensive to be solved with DSMC when the experiment flew in 1994.

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

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.

Electronic State Distributions of YBa2Cu3O7-x Laser Ablated Plumes

DTIC Science & Technology

2008-09-01

deposited on buffered metal substrates using gas phase techniques such as pulsed laser deposition (PLD) or metal -oxide chem- ical vapor deposition...along the desired current direction. This grain orientation has been successfully achieved by depositing YBCO on a metal tape substrate coated with a...Reeves, K. Lenseth, and V. Selvamanickam. “Texture Development and Superconducting Properties of YBCO Thick Films Deposited on Buffered Metal Substrates

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.

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

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.

Near-IR imaging of erbium laser ablation with a water spray

NASA Astrophysics Data System (ADS)

Darling, Cynthia L.; Maffei, Marie E.; Fried, William A.; Fried, Daniel

2008-02-01

Near-IR (NIR) imaging can be used to view the formation of ablation craters during laser ablation since the enamel of the tooth is almost completely transparent near 1310-nm1. Laser ablation craters can be monitored under varying irradiation conditions to assess peripheral thermal and transient-stress induced damage, measure the rate and efficiency of ablation and provide insight into the ablation mechanism. There are fundamental differences in the mechanism of enamel ablation using erbium lasers versus carbon dioxide laser systems due to the nature of the primary absorber and it is necessary to have water present on the tooth surface for efficient ablation at erbium laser wavelengths. In this study, sound human tooth sections of approximately 2-3-mm thickness were irradiated by free running and Q-switched Er:YAG & Er:YSGG lasers under varying conditions with and without a water spray. The incision area in the interior of each sample was imaged using a tungsten-halogen lamp with a band-pass filter centered at 1310-nm combined with an InGaAs area camera with a NIR zoom microscope. Obvious differences in the crater evolution were observed between CO2 and erbium lasers. Ablation stalled after a few laser pulses without a water spray as anticipated. Efficient ablation was re-initiated by resuming the water spray. Micro-fractures were continuously produced apparently driven along prism lines during multi-pulse ablation. These fractures or fissures appeared to merge together as the crater evolved to form the leading edge of the ablation crater. These observations support the proposed thermo-mechanical mechanisms of erbium laser involving the strong mechanical forces generated by selective absorption by water.

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.

LANDSAT observations of ocean dump plume movement and dispersion. [Cape Henlopen, Delaware

NASA Technical Reports Server (NTRS)

Klemas, V. (Principal Investigator); Davis, G. R.; Henry, R.

1976-01-01

The author has identified the following significant results. Eighteen LANDSAT images were analyzed to study the dispersion and movement of ocean dump plumes thirty-eight miles southeast of Cape Henlopen, Delaware, at the disposal site for waste discharged from a plant producing titanium dioxide. Long visual persistence was explained by the formation of a suspended ferric floc. Spectrometric measurements indicate that upon combining with sea water the acid waste develops a strong reflectance peak in the band 0.55 to 0.60 micron region, resulting in a stronger contrast in the MSS band 4 than the other bands. Predominant direction of movement of the waste plumes was to the southeast. Average drift velocity for surface drogues and the waste plumes was about 0.5 knots. The water at the test site was highly stratified and stable in the summer and nearly homogenous in the winter.

Onboard Image Processing for Autonomous Spacecraft Detection of Volcanic Plumes

NASA Astrophysics Data System (ADS)

Thompson, D. R.; Bunte, M.; Castaño, R.; Chien, S.; Greeley, R.

2011-03-01

Onboard spacecraft image processing could enable long-term monitoring for volcanic plume activity in the outer planets. A new plume detection technique shows strong performance on images of Enceladus and Io taken by Cassini, Voyager, and Galileo.

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.

Femtosecond laser ablation of enamel

NASA Astrophysics Data System (ADS)

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

2016-06-01

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

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

The plume head-continental lithosphere interaction using a tectonically realistic formulation for the lithosphere

NASA Astrophysics Data System (ADS)

Burov, E.; Guillou-Frottier, L.

2005-05-01

Current debates on the existence of mantle plumes largely originate from interpretations of supposed signatures of plume-induced surface topography that are compared with predictions of geodynamic models of plume-lithosphere interactions. These models often inaccurately predict surface evolution: in general, they assume a fixed upper surface and consider the lithosphere as a single viscous layer. In nature, the surface evolution is affected by the elastic-brittle-ductile deformation, by a free upper surface and by the layered structure of the lithosphere. We make a step towards reconciling mantle- and tectonic-scale studies by introducing a tectonically realistic continental plate model in large-scale plume-lithosphere interaction. This model includes (i) a natural free surface boundary condition, (ii) an explicit elastic-viscous(ductile)-plastic(brittle) rheology and (iii) a stratified structure of continental lithosphere. The numerical experiments demonstrate a number of important differences from predictions of conventional models. In particular, this relates to plate bending, mechanical decoupling of crustal and mantle layers and tension-compression instabilities, which produce transient topographic signatures such as uplift and subsidence at large (>500 km) and small scale (300-400, 200-300 and 50-100 km). The mantle plumes do not necessarily produce detectable large-scale topographic highs but often generate only alternating small-scale surface features that could otherwise be attributed to regional tectonics. A single large-wavelength deformation, predicted by conventional models, develops only for a very cold and thick lithosphere. Distinct topographic wavelengths or temporarily spaced events observed in the East African rift system, as well as over French Massif Central, can be explained by a single plume impinging at the base of the continental lithosphere, without evoking complex asthenospheric upwelling.

A distribution-based parametrization for improved tomographic imaging of solute plumes

USGS Publications Warehouse

Pidlisecky, Adam; Singha, K.; Day-Lewis, F. D.

2011-01-01

Difference geophysical tomography (e.g. radar, resistivity and seismic) is used increasingly for imaging fluid flow and mass transport associated with natural and engineered hydrologic phenomena, including tracer experiments, in situ remediation and aquifer storage and recovery. Tomographic data are collected over time, inverted and differenced against a background image to produce 'snapshots' revealing changes to the system; these snapshots readily provide qualitative information on the location and morphology of plumes of injected tracer, remedial amendment or stored water. In principle, geometric moments (i.e. total mass, centres of mass, spread, etc.) calculated from difference tomograms can provide further quantitative insight into the rates of advection, dispersion and mass transfer; however, recent work has shown that moments calculated from tomograms are commonly biased, as they are strongly affected by the subjective choice of regularization criteria. Conventional approaches to regularization (Tikhonov) and parametrization (image pixels) result in tomograms which are subject to artefacts such as smearing or pixel estimates taking on the sign opposite to that expected for the plume under study. Here, we demonstrate a novel parametrization for imaging plumes associated with hydrologic phenomena. Capitalizing on the mathematical analogy between moment-based descriptors of plumes and the moment-based parameters of probability distributions, we design an inverse problem that (1) is overdetermined and computationally efficient because the image is described by only a few parameters, (2) produces tomograms consistent with expected plume behaviour (e.g. changes of one sign relative to the background image), (3) yields parameter estimates that are readily interpreted for plume morphology and offer direct insight into hydrologic processes and (4) requires comparatively few data to achieve reasonable model estimates. We demonstrate the approach in a series of

Reed Watkins: A Passion for Plume Moths

USDA-ARS?s Scientific Manuscript database

Reed Watkins has curated the nationl Pterophordiae or plume moth collection at the National Museum of Natural History, Smithsonian Institution, for the past 13 years. He has decreased the number of specimens of unsorted and unidentified material and has expanded the collection from 3 to 6 cabinets....

Study of high altitude plume impingement

NASA Technical Reports Server (NTRS)

Wojciechowski, C. J.; Penny, M. M.; Prozan, R. J.; Seymour, D.; Greenwood, T. F.

1972-01-01

Computer program has been developed as analytical tool to predict severity of effects of exhaust of rocket engines on adjacent spacecraft surfaces. Program computes forces, moments, pressures, and heating rates on surfaces immersed in or subjected to exhaust plume environments. Predictions will be useful in design of systems where such problems are anticipated.

Smoke plume behavior - what the data say

Treesearch

Gary L. Achtemeier; Luke Naeher

2005-01-01

a comprehensive smoke project, now ongoing for four years, is designed in part to investigate plume behavior from southern prescribed burns with respect to atmospheric stability and to document ground-level smoke concentrations with PM2.5 data from a network of samplers specially constructed for the project. Project management goals are to find ways to increase the...

Irreversible electroporation ablation area enhanced by synergistic high- and low-voltage pulses.

PubMed

Yao, Chenguo; Lv, Yanpeng; Dong, Shoulong; Zhao, Yajun; Liu, Hongmei

2017-01-01