Science.gov

Sample records for micron slab stability

  1. Stability of Alfven oscillations in a plane plasma slab

    SciTech Connect

    Patudin, V.M.; Sagalakov, A.M.

    1983-05-01

    The stability of the natural Alfven oscillations of a plane slab of a collisional, slightly nonequilibrium plasma in a uniform magnetic field is studied. An effective numerical method, a special version of the differential sweepout method, is proposed. A calculation procedure has been developed. The small-oscillation spectrum is analyzed for parabolic plasma density profiles, and neutral curves are plotted. The growth rates and critical parameters are determined. At a high plasma conductivity, both strongly and weakly localized perturbations near the axis can go unstable. For a density profile with an inflection point, weakly damped oscillations are observed near the inflection point. These oscillations can also be excited by an ion beam.

  2. SLAB symmetric dielectric micron scale structures for high gradient electron acceleration.

    SciTech Connect

    Rosenzweig, J. B.; Schoessow, P. V.

    1999-06-12

    A class of planar microstructure is proposed which provide high accelerating gradients when excited by an infrared laser pulse. These structures consist of parallel dielectric slabs separated by a vacuum gap; the dielectric or the outer surface coating are spatially modulated at the laser wavelength along the beam direction so as to support a standing wave accelerating field. We have developed numerical and analytic models of the accelerating mode fields in the structure. We show an optimized coupling scheme such that this mode is excited resonantly with a large quality factor. The status of planned experiments on fabricating and measuring these planar structures will be described.

  3. Micron: an Actively Stabilized Handheld Tool for Microsurgery

    PubMed Central

    MacLachlan, Robert A.; Becker, Brian C.; Tabarés, Jaime Cuevas; Podnar, Gregg W.; Lobes, Louis A.; Riviere, Cameron N.

    2011-01-01

    We describe the design and performance of a hand-held actively stabilized tool to increase accuracy in micro-surgery or other precision manipulation. It removes involuntary motion such as tremor by actuating the tip to counteract the effect of the undesired handle motion. The key components are a three-degree-of-freedom piezoelectric manipulator that has 400 μm range of motion, 1 N force capability, and bandwidth over 100 Hz, and an optical position measurement subsystem that acquires the tool pose with 4 μm resolution at 2000 samples/s. A control system using these components attenuates hand motion by at least 15 dB (a fivefold reduction). By considering the effect of the frequency response of Micron on the human visual feedback loop, we have developed a filter that reduces unintentional motion, yet preserves intuitive eye-hand coordination. We evaluated the effectiveness of Micron by measuring the accuracy of the human/machine system in three simple manipulation tasks. Handheld testing by three eye surgeons and three non-surgeons showed a reduction in position error of between 32% and 52%, depending on the error metric. PMID:23028266

  4. Spatial Stability of the Expanding Magnetized Slab Jet

    NASA Astrophysics Data System (ADS)

    Cooper, M. A.; Hardee, P. E.; Clarke, D. A.

    1993-12-01

    A spatial stability analysis of the Kelvin-Helmholtz instability in an expanding axially magnetized slab jet is presented. The results are then compared with numerical simulations to see if the perturbation theory correctly describes global instabilities. Provided the jet is highly super-Alfvenic and highly supersonic then the dispersion relation describing the propagation and growth of a perturbation admits the same type of solutions as those found for purely fluid jets. However, in the region where the jet is only slightly super-Alfvenic or slightly supersonic, the expansion of the jet causes the solution to split into a growing and damped pair. This splitting occurs for both sonic and Alfvenic disturbances which propagate along the flow direction. At high frequencies, the growing solutions of the fundamental sinusoidal mode correspond to sound waves and Alfven waves propagating in the flow direction, while the damped solutions correspond to sound waves and Alfven waves propagating against the flow. Those solutions which are damped at high frequencies become growing as the frequency is decreased. The opposite is true for growing solutions at high frequencies. When the jet is sub-Alfvenic, at least one solution of the fundamental mode is not stabilized. However, the simulations suggest that any instabilities that arise when the jet is sub- or trans-Alfvenic will be damped out as the jet becomes fully super-Alfvenic. Therefore, for sub-Alfvenic jets it may be necessary to consider the effects of expansion on the stability of the jet. This work was supported by NSF grant AST-8919180 and EPSCoR grant EHR-9108761.

  5. Ultra-Low Threshold Optical Bistability and Multi-Stability in Dielecrtric Slab Doped with Semiconductor Quantum Well

    NASA Astrophysics Data System (ADS)

    Nasehi, R.

    2016-07-01

    A scheme for switching of the optical bistability (OB) and multi-stability (OM) in a dielectric slab doped with a three-level ladder-configuration n-doped semiconductor quantum well is simulated. It is shown that the bistable behavior of the system in dielectric slab can be controlled via amplitude or relative phase of applied fields. This optical system may provide some new possibilities for test the switching process.

  6. The dynamics and stability of radiatively driven gas clouds. I - Plane-parallel slabs

    NASA Technical Reports Server (NTRS)

    Haas, M. R.

    1979-01-01

    A combination of numerical and analytical techniques has been used to investigate the dynamics and stability of optically thin plane-parallel radiatively driven slabs of gas confined by the thermal gas pressure of a high-temperature low-density medium. Scaling laws allow the individual model 'clouds' to be characterized by a single free parameter, chi, a normalized column density which measures the strength of the acceleration due to radiation pressure relative to that due to thermal gas pressure. It is found that these clouds are stable and coherently accelerated only when chi is small. In this regime a simple slab model is constructed which accurately reproduces the more complex gasdynamic results. The low-chi clouds are marginally able to reach the high velocities seen in the atmospheres of quasi-stellar objects, but only if their motion is subsonic with respect to the external confining medium. This implies either that the medium is extremely hot and tenuous or that it is moving outward with the clouds.

  7. Stability of Interfacial Phase Growth in a Slab with Convective Boundary Conditions

    NASA Astrophysics Data System (ADS)

    Basu, Rahul

    2016-06-01

    The mass transport and energy equations for a semi-infinite porous slab are solved using similarity variables and closed form functions to describe freezing with remelt at the interface. Heat and mass balance analyses give a transcendental equation for the unknown interfacial freezing velocity for solving on the computer. The solutions for the temperature and mass concentration are decoupled and solved analytically. The solution for convective boundary conditions is compared with that for Dirichlet boundary conditions. The progressive development of the solution with material thickness and change of functional time dependence and effect on the stability of nucleation is outlined. A discussion with biological adaptation to extreme cold and possible evolution of molecules in heat transfer regimes is included in light of the above.

  8. Block copolymer stabilized nonaqueous biocompatible sub-micron emulsions for topical applications.

    PubMed

    Atanase, Leonard Ionut; Riess, Gérard

    2013-05-20

    Polyethylene glycol (PEG) 400/Miglyol 812 non-aqueous sub-micron emulsions were developed due to the fact that they are of interest for the design of drug-loaded biocompatible topical formulations. These types of emulsions were favourably stabilized by poly (2-vinylpyridine)-b-poly (butadiene) (P2VP-b-PBut) copolymer with DPBut>DP2VP, each of these sequences being well-adapted to the solubility parameters of PEG 400 and Miglyol 812, respectively. This type of block copolymers, which might limit the Ostwald ripening, appeared to be more efficient stabilizers than low molecular weight non-ionic surfactants. The emulsion characteristics, such as particle size, stability and viscosity at different shear rates were determined as a function of the phase ratio, the copolymer concentration and storage time. It was further shown that Acyclovir, as a model drug of low water solubility, could be incorporated into the PEG 400 dispersed phase, with no significant modification of the initial emulsion characteristics. PMID:23566926

  9. Observation of Optical Bistability and Multi-Stability in the Dielecrtric Slab Doped with a Quantum well Waveguide

    NASA Astrophysics Data System (ADS)

    Nasehi, R.

    2016-08-01

    The optical bistability (OB) and multi-stability (OM) behavior in a dielectric slab medium doped with semiconductor quantum well nanostructure has been discussed by employing the spin coherence effect. It is shown that, by changing the relative phase of applied fields the bistable behavior switches from OB to OM or vice versa in a dielectric medium. The effect of the frequency detuning of laser fields on the OB and OM behavior are also discussed in this paper.

  10. Communication: Slab thickness dependence of the surface tension: toward a criterion of liquid sheets stability.

    PubMed

    Filippini, G; Bourasseau, E; Ghoufi, A; Goujon, F; Malfreyt, P

    2014-08-28

    Microscopic Monte Carlo simulations of liquid sheets of copper and tin have been performed in order to study the dependence of the surface tension on the thickness of the sheet. It results that the surface tension is constant with the thickness as long as the sheet remains in one piece. When the sheet is getting thinner, holes start to appear, and the calculated surface tension rapidly decreases with thickness until the sheet becomes totally unstable and forms a cylinder. We assume here that this decrease is not due to a confinement effect as proposed by Werth et al. [Physica A 392, 2359 (2013)] on Lennard-Jones systems, but to the appearance of holes that reduces the energy cost of the surface modification. We also show in this work that a link can be established between the stability of the sheet and the local fluctuations of the surface position, which directly depends on the value of the surface tension. Finally, we complete this study by investigating systems interacting through different forms of Lennard-Jones potentials to check if similar conclusions can be drawn.

  11. Communication: Slab thickness dependence of the surface tension: Toward a criterion of liquid sheets stability

    NASA Astrophysics Data System (ADS)

    Filippini, G.; Bourasseau, E.; Ghoufi, A.; Goujon, F.; Malfreyt, P.

    2014-08-01

    Microscopic Monte Carlo simulations of liquid sheets of copper and tin have been performed in order to study the dependence of the surface tension on the thickness of the sheet. It results that the surface tension is constant with the thickness as long as the sheet remains in one piece. When the sheet is getting thinner, holes start to appear, and the calculated surface tension rapidly decreases with thickness until the sheet becomes totally unstable and forms a cylinder. We assume here that this decrease is not due to a confinement effect as proposed by Werth et al. [Physica A 392, 2359 (2013)] on Lennard-Jones systems, but to the appearance of holes that reduces the energy cost of the surface modification. We also show in this work that a link can be established between the stability of the sheet and the local fluctuations of the surface position, which directly depends on the value of the surface tension. Finally, we complete this study by investigating systems interacting through different forms of Lennard-Jones potentials to check if similar conclusions can be drawn.

  12. Repetitively pulsed Nd-glass slab lasers

    NASA Astrophysics Data System (ADS)

    Denker, B. I.; Kir'ianov, A. V.; Maliutin, A. A.; Kertesz, I.; Kroo, N.

    1989-09-01

    The possibility of obtaining high laser output energies at 1.32 micron using thin LiNdLa phosphate glass slabs with a high Nd(3+) concentration is discussed. Comparison data for 1.054 micron are also given. In the experiments, 3 x 14 x 125-mm slabs were prepared from LiNdLa phosphate glass with Nd concentration 1.2 x 10 to the 21st/cu cm. The uncoated slab facets were tested in a silver-coated quartz tube reflector pumped by 450-microsec flash-lamp pulses. The light passing through the slab returns to it after reflection from the tube surface. Most of the radiation falls on the wider side of the slab at large angles of incidence, thus maximizing its path inside the slab. The 150-mm laser resonator was formed by two flat mirrors. At 1.32 microns an output mirror of reflectivity r = 95 percent was used (with r less than 10 percent at 1.054 micron), while at 1.054 micron, r(output) = 50 percent was chosen. The pump-energy dependence of the output energy was measured.

  13. Improving image quality and stability of two-dimensional photonic crystal slab by changing surface structure of the photonic crystal

    NASA Astrophysics Data System (ADS)

    Zhu, Zhao-Jie; Liu, Peng-Fang; Tong, Yuan-Wei

    2016-03-01

    The propagation of electromagnetic (EM) waves in two-dimensional hexagon-lattice photonic crystals (PCs) is investigated through dispersion characteristics analysis and numerical simulation of field pattern. The full width at half maximum (FWHM) of the image reach 0.37λ which is much smaller than 0.5λ by changing surface structure of the photonic crystal, and the variance of FWHM of image focused by the changed slab seems to be less than the variance of FWHM of image focused by the original slab with the changing of source position.

  14. Slab reformer

    NASA Technical Reports Server (NTRS)

    Spurrier, Francis R. (Inventor); DeZubay, Egon A. (Inventor); Murray, Alexander P. (Inventor); Vidt, Edward J. (Inventor)

    1984-01-01

    Slab-shaped high efficiency catalytic reformer configurations particularly useful for generation of fuels to be used in fuel cell based generation systems. A plurality of structures forming a generally rectangular peripheral envelope are spaced about one another to form annular regions, an interior annular region containing a catalytic bed and being regeneratively heated on one side by a hot comubstion gas and on the other side by the gaseous products of the reformation. An integrally mounted combustor is cooled by impingement of incoming oxidant.

  15. Slab reformer

    DOEpatents

    Spurrier, Francis R.; DeZubay, Egon A.; Murray, Alexander P.; Vidt, Edward J.

    1985-03-12

    Slab-shaped high efficiency catalytic reformer configurations particularly useful for generation of fuels to be used in fuel cell based generation systems. A plurality of structures forming a generally rectangular peripheral envelope are spaced about one another to form annular regions, an interior annular region containing a catalytic bed and being regeneratively heated on one side by a hot combustion gas and on the other side by the gaseous products of the reformation. An integrally mounted combustor is cooled by impingement of incoming oxidant.

  16. Slab reformer

    DOEpatents

    Spurrier, Francis R.; DeZubay, Egon A.; Murray, Alexander P.; Vidt, Edward J.

    1984-02-07

    Slab-shaped high efficiency catalytic reformer configurations particularly useful for generation of fuels to be used in fuel cell based generation systems. A plurality of structures forming a generally rectangular peripheral envelope are spaced about one another to form annular regions, an interior annular region containing a catalytic bed and being regeneratively heated on one side by a hot comubstion gas and on the other side by the gaseous products of the reformation. An integrally mounted combustor is cooled by impingement of incoming oxidant.

  17. Slab reformer

    DOEpatents

    Spurrier, F.R.; DeZubay, E.A.; Murray, A.P.; Vidt, E.J.

    1984-02-07

    Slab-shaped high efficiency catalytic reformer configurations are disclosed particularly useful for generation of fuels to be used in fuel cell based generation systems. A plurality of structures forming a generally rectangular peripheral envelope are spaced about one another to form annular regions, an interior annular region containing a catalytic bed and being regeneratively heated on one side by a hot combustion gas and on the other side by the gaseous products of the reformation. An integrally mounted combustor is cooled by impingement of incoming oxidant. 14 figs.

  18. Visualizing the Stability of Char: Molecular- to Micron-scale Observations of Char Incubated in a Tropical Soil

    NASA Astrophysics Data System (ADS)

    Heckman, K. A.; Ramon, C.; Weber, P. K.; Torn, M. S.; Pett-Ridge, J.; Nico, P. S.

    2014-12-01

    The persistence of pyrogenic materials (hereafter referred to as char) in terrestrial ecosystems is of interest both from a carbon cycle modelling perspective and a climate change mitigation standpoint. However, the fate of newly introduced char in soils remains unclear. Recent reviews attempting to summarize trends in char decomposition have come to differing conclusions, further stressing the complexity of factors dictating char stability in soils. The current dataset specifically addresses the stability of char additions to a tropical clay-rich soil, possible priming effects, and interactions among char, microbial communities and the mineral matrix. 13C- and 15N-labeled Acer rubrum(red maple) wood was combusted at 400°C and added to surface (0-10 cm) and subsurface (20-30 cm) soils from the Luquillo Experimental Forest, Puerto Rico. Soils were incubated for 13 and 345 days at 26°C. Following incubation, intact microaggregates were frozen and cryosectioned into thin sections of approximately 5 μm thickness and mounted on gold-coated quartz slides. Thin sections were examined by synchrotron-based Fourier transform infrared spectroscopy (SR-FTIR), scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS), and high resolution secondary ion mass spectrometry (nanoSIMS). The combination of these μm to nm scale techniques allowed us to create corresponding spatial maps of native organic matter, char, and mineral phase distribution, track spatial variability in organic matter molecular structure, and dispersion of 13C and 15N isotopic labels. We present preliminary results indicating a high degree of stability of char in these wet tropical soils throughout the incubation period, suggesting that applied char may persist for long periods of time in similar soils.

  19. Optimization of A 2-Micron Laser Frequency Stabilization System for a Double-Pulse CO2 Differential Absorption Lidar

    NASA Technical Reports Server (NTRS)

    Chen, Songsheng; Yu, Jirong; Bai, Yingsin; Koch, Grady; Petros, Mulugeta; Trieu, Bo; Petzar, Paul; Singh, Upendra N.; Kavaya, Michael J.; Beyon, Jeffrey

    2010-01-01

    A carbon dioxide (CO2) Differential Absorption Lidar (DIAL) for accurate CO2 concentration measurement requires a frequency locking system to achieve high frequency locking precision and stability. We describe the frequency locking system utilizing Frequency Modulation (FM), Phase Sensitive Detection (PSD), and Proportional Integration Derivative (PID) feedback servo loop, and report the optimization of the sensitivity of the system for the feed back loop based on the characteristics of a variable path-length CO2 gas cell. The CO2 gas cell is characterized with HITRAN database (2004). The method can be applied for any other frequency locking systems referring to gas absorption line.

  20. Causes for the Onset and Stability of Flat Slabs and Associated Overriding Plate Deformation Inferred from Numerical Thermo-Mechanical Models

    NASA Astrophysics Data System (ADS)

    Kanda, R. V. S.; Lowry, A. R.; Buiter, S. J.; Ellis, S. M.

    2015-12-01

    Flat slab subduction comprises only ~10% of the present-day subduction systems. We systematically explore flat-slab subduction and over-riding plate deformation due to previously recognized factors (including a weak mantle wedge, a buoyant oceanic plateau/ridge, slab-age, presence of thick cratonic upper plate), as well as additional factors not considered before (transient plate-velocity variations, and the presence of stagnant slabs at the mantle transition zone). We use a visco-elasto-plastic code, SULEC (Buiter & Ellis, 2012), restrict ourselves to 2D models, and ignore phase transformations. We model a 6000 km by 1500 km domain with 1-10 km variable grid spacing using up-to-date laboratory-derived constitutive laws, and explore the effects of: (a) lateral/vertical structure of the crust and lithosphere (e.g., continental lithosphere with/without a craton; oceanic lithosphere with thickness governed by plate cooling, and a harzburgite layer); (b) a true free upper-surface to predict surface topography; and (c) only far-field (boundary) velocities driving plates, with trench-velocity depending on over-riding plate deformation and slab pull. As in previous studies, we find that positive trench-retreat velocity and weak integrated slab-strength (as measured by differential stress) are necessary, but not sufficient, conditions for flat-slab subduction. While mantle-wedge suction associated with the presence of a craton does promote flat slab subduction, models without a craton also produce flat-slabs when (a) trench-retreat velocities are large and (b) either the slab is positively (structurally or thermally) buoyant or there is an underlying slab at the mantle transition zone. In our models, the duration of flat slab subduction depends on overall slab buoyancy. Younger oceanic lithosphere, esp. if it contains a plateau/ridge, provides a longer-lasting flat-slab (~ 10 Myr or longer, e.g., central Mexico), while older slabs with oceanic ridge/plateau (e.g., Peru

  1. Mesoporous silica sub-micron spheres as drug dissolution enhancers: Influence of drug and matrix chemistry on functionality and stability.

    PubMed

    Brigo, Laura; Scomparin, Elisa; Galuppo, Marco; Capurso, Giovanni; Ferlin, Maria Grazia; Bello, Valentina; Realdon, Nicola; Brusatin, Giovanna; Morpurgo, Margherita

    2016-02-01

    Mesoporous silica particles prepared through a simplified Stöber method and low temperature solvent promoted surfactant removal are evaluated as dissolution enhancers for poorly soluble compounds, using a powerful anticancer agent belonging to pyrroloquinolinones as a model for anticancer oral therapy, and anti-inflammatory ibuprofen as a reference compound. Mesoporous powders composed of either pure silica or silica modified with aminopropyl residues are produced. The influence of material composition and drug chemical properties on drug loading capability and dissolution enhancement are studied. The two types of particles display similar size, surface area, porosity, erodibility, drug loading capability and stability. An up to 50% w/w drug loading is reached, showing correlation between drug concentration in adsorption medium and content in the final powder. Upon immersion in simulating body fluids, immediate drug dissolution occurred, allowing acceptor solutions to reach concentrations equal to or greater than drug saturation limits. The matrix composition influenced drug solution maximal concentration, complementing the dissolution enhancement generated by a mesoporous structure. This effect was found to depend on both matrix and drug chemical properties allowing us to hypothesise general prediction behaviour rules. PMID:26652411

  2. Mesoporous silica sub-micron spheres as drug dissolution enhancers: Influence of drug and matrix chemistry on functionality and stability.

    PubMed

    Brigo, Laura; Scomparin, Elisa; Galuppo, Marco; Capurso, Giovanni; Ferlin, Maria Grazia; Bello, Valentina; Realdon, Nicola; Brusatin, Giovanna; Morpurgo, Margherita

    2016-02-01

    Mesoporous silica particles prepared through a simplified Stöber method and low temperature solvent promoted surfactant removal are evaluated as dissolution enhancers for poorly soluble compounds, using a powerful anticancer agent belonging to pyrroloquinolinones as a model for anticancer oral therapy, and anti-inflammatory ibuprofen as a reference compound. Mesoporous powders composed of either pure silica or silica modified with aminopropyl residues are produced. The influence of material composition and drug chemical properties on drug loading capability and dissolution enhancement are studied. The two types of particles display similar size, surface area, porosity, erodibility, drug loading capability and stability. An up to 50% w/w drug loading is reached, showing correlation between drug concentration in adsorption medium and content in the final powder. Upon immersion in simulating body fluids, immediate drug dissolution occurred, allowing acceptor solutions to reach concentrations equal to or greater than drug saturation limits. The matrix composition influenced drug solution maximal concentration, complementing the dissolution enhancement generated by a mesoporous structure. This effect was found to depend on both matrix and drug chemical properties allowing us to hypothesise general prediction behaviour rules.

  3. Influence of Turbulent Flows in the Nozzle on Melt Flow Within a Slab Mold and Stability of the Metal-Flux Interface

    NASA Astrophysics Data System (ADS)

    Calderon-Ramos, Ismael; Morales, R. D.

    2016-06-01

    The design of the ports of a casting nozzle has profound effects on the fluid flow patterns in slab molds. The influence of these outlets have also considerable effects on the turbulent flow and turbulence variables inside the nozzle itself. To understand the effects of nozzle design, three approaches were employed: a theoretical analysis based on the turbulent viscosity hypothesis, dimensional analysis (both analyses aided by computer fluid dynamics), and experiments using particle image velocimetry. The first approach yields a linear relation between calculated magnitudes of scalar fields of ɛ (dissipation rate of kinetic energy) and k 2 (square of the turbulent kinetic energy), which is derived from the wall and the logarithmic-wall laws in the boundary layers. The smaller the slope of this linear relation is, the better the performance of a given nozzle is for maintaining the stability of the melt-flux interface. The second approach yields also a linear relation between flow rate of liquid metal and the cubic root of the dissipation rate of kinetic energy. In this case, the larger the slope of the linear relation is, the better the performance of a given nozzle is for maintaining the stability of the melt-flux interface. Finally, PIV measurements in a mold water model, together with equations for estimation of critical melt velocities for slag entrainment, were used to quantify the effects of nozzle design on the dynamics of the metal-slag interface. The three approaches agree in the characterization of turbulent flows in continuous casting molds using different nozzles.

  4. Hierarchical micron-sized mesoporous/macroporous graphene with well-tuned surface oxygen chemistry for high capacity and cycling stability Li-O2 battery.

    PubMed

    Zhou, Wei; Zhang, Hongzhang; Nie, Hongjiao; Ma, Yiwen; Zhang, Yining; Zhang, Huamin

    2015-02-11

    Nonaqueous Li-O2 battery is recognized as one of the most promising energy storage devices for electric vehicles due to its super-high energy density. At present, carbon or catalyst-supporting carbon materials are widely used for cathode materials of Li-O2 battery. However, the unique electrode reaction and complex side reactions lead to numerous hurdles that have to be overcome. The pore blocking caused by the solid products and the byproducts generated from the side reactions severely limit the capacity performance and cycling stability. Thus, there is a great need to develop carbon materials with optimized pore structure and tunable surface chemistry to meet the special requirement of Li-O2 battery. Here, we propose a strategy of vacuum-promoted thermal expansion to fabricate one micron-sized graphene matrix with a hierarchical meso-/macroporous structure, combining with a following deoxygenation treatment to adjust the surface chemistry by reducing the amount of oxygen and selectively removing partial unstable groups. The as-made graphene demonstrates dramatically tailored pore characteristics and a well-tuned surface chemical environment. When applied in Li-O2 battery as cathode, it exhibits an outstanding capacity up to 19 800 mA h g(-1) and is capable of enduring over 50 cycles with a curtaining capacity of 1000 mA h g(-1) at a current density of 1000 mA g(-1). This will provide a novel pathway for the design of cathodes for Li-O2 battery.

  5. Micronized-Coal Burner Facility

    NASA Technical Reports Server (NTRS)

    Calfo, F. D.; Lupton, M. W.

    1986-01-01

    Micronized-coal (coal-in-oil mix) burner facility developed to fulfill need to generate erosion/corrosion data on series of superalloy specimens. In order to successfully operate gas turbine using COM, two primary conditions must be met. First, there must be adequate atomization of COM and second, minimization of coking of burner. Meeting these conditions will be achieved only by clean burning and flame stability.

  6. Turbulence in the cylindrical slab

    SciTech Connect

    Gentle, K. W.; Rowan, W. L.; Williams, C. B.; Brookman, M. W.

    2014-09-15

    The cylindrical slab was the first and simplest model of intrinsically unstable microturbulence. The Helimak is an experimental realization of this model. Although finite, it is sufficiently large to escape boundary effects, with dimensionless parameters similar to those of a tokamak edge or scrape off layer. The essential drive is interchange-like, a pressure gradient with unfavorable magnetic curvature, leading to a non-linearly saturated state of large-amplitude turbulence, Δn{sub rms}/n ∼ 0.5. The nonlinear processes governing this saturation are unique, unlike any of those posited for the much weaker turbulence typical of confined plasma, e.g., in a tokamak. Neither linear stability theory, quasi-linear theory, zonal flows, nor flow shear stabilization is consistent with the observations. The mechanisms determining the non-linearly saturated state constitute an important challenge to our understanding of strongly nonlinear systems.

  7. Active frequency stabilization of a 1.062-micron, Nd:GGG, diode-laser-pumped nonplanar ring oscillator to less than 3 Hz of relative linewidth

    NASA Technical Reports Server (NTRS)

    Day, T.; Gustafson, E. K.; Byer, R. L.

    1990-01-01

    Results are presented on the frequency stabilization of two diode-laser-pumped ring lasers that are independently locked to the same high-finesse interferometer. The relative frequency stability is measured by locking the lasers one free spectral range apart and observing the heterodyne beat note. The resultant beat note width of 2.9 Hz is consistent with the theoretical system noise-limited linewidth and is approximately 20 times that expected for shot-noise-limited performance.

  8. Slab Leaf Bowls

    ERIC Educational Resources Information Center

    Suitor, Cheryl

    2012-01-01

    In science class, fourth graders investigate the structure of plants and leaves from trees and how the process of photosynthesis turns sunlight into sugar proteins. In this article, the author fuses art and science for a creative and successful clay slab project in her elementary art classroom. (Contains 1 online resource.)

  9. Carbon dioxide slab laser

    SciTech Connect

    Tulip, J.

    1988-01-12

    A gas slab laser is described comprising: first and second elongated electrodes each including a planar light reflecting surface disposed so as to form a light guide only in a plane perpendicular to the planar surface and to define a gas discharge gap therebetween; a laser gas disposed in the gap; and means for applying a radio frequency current between the first and second electrodes to establish a laser-exciting discharge in the laser gas.

  10. Micronized grinding apparatus

    SciTech Connect

    Williams, R.M.

    1985-06-11

    Apparatus for grinding coal to micron fineness having a grinding chamber with a grinding surface supported by a circumferential wall in the grinding chamber, a plurality of grinding rolls orbiting in the grinding chamber for grinding the coal, air supply bustle surrounding the grinding chamber, air flow restrictor means opening from the air supply bustle to the grinding chamber to create a back pressure in the air supply bustle for substantially evenly distributing the air supplied to the grinding chamber around the circumference of the grinding chamber, and wherein the restrictor means directs the air flow tangentially relative to the circumferential wall of the grinding chamber so that the coal particles are caught up in a cyclonic movement having a large initial horizontally directed force to maintain a body of coal particles in the orbit of the grinding rolls, which horizontal force gradually diminishes as the vertical force component of the air flow lifts the ground coal particles out of the grinding chamber.

  11. Sub-micron filter

    DOEpatents

    Tepper, Frederick; Kaledin, Leonid

    2009-10-13

    Aluminum hydroxide fibers approximately 2 nanometers in diameter and with surface areas ranging from 200 to 650 m.sup.2/g have been found to be highly electropositive. When dispersed in water they are able to attach to and retain electronegative particles. When combined into a composite filter with other fibers or particles they can filter bacteria and nano size particulates such as viruses and colloidal particles at high flux through the filter. Such filters can be used for purification and sterilization of water, biological, medical and pharmaceutical fluids, and as a collector/concentrator for detection and assay of microbes and viruses. The alumina fibers are also capable of filtering sub-micron inorganic and metallic particles to produce ultra pure water. The fibers are suitable as a substrate for growth of cells. Macromolecules such as proteins may be separated from each other based on their electronegative charges.

  12. SUB-SLAB PROBE INSTALLATION

    EPA Science Inventory

    Sub-slab sampling has become an integral part of vapor intrusion investigations. It is now recommended in guidance documents developed by EPA and most states. A method for sub-slab probe installation was devised in 2002, presented at conferences through 2005, and finally docume...

  13. [Thermoluminescence Slab Dosimeter].

    PubMed

    Shinsho, Kiyomitsu; Koba, Yusuke; Tamatsu, Satoshi; Sakurai, Noboru; Wakabayashi, Genichiro; Fukuda, Kazusige

    2013-01-01

    In 1953 F. Daniels et al. used the property of thermoluminescence in dosimetry for the first time. Since then, numerous TLD have been developed. 2D TLD was investigated for the first time in 1972 by P Broadhead. However, due to excessive fading, difficulties with handling and the time required for measurements, development stalled. At the current time, the majority of TLD are used in small scale, localized dosimetry with a wide dynamic range and personal dosimeters for exposure management. Urushiyama et. al. have taken advantage of the commoditization of CCD cameras in recent years--making large area, high resolution imaging easier--to introduce and develop a 2D TLD. It is expected that these developments will give rise to a new generation of applications for 2D TL dosimetry. This paper introduces the "TL Slab Dosimeter" developed jointly by Urushiyama et. al. and our team, its measurement system and several typical usage scenarios.

  14. New Packaging for Amplifier Slabs

    SciTech Connect

    Riley, M.; Thorsness, C.; Suratwala, T.; Steele, R.; Rogowski, G.

    2015-03-18

    The following memo provides a discussion and detailed procedure for a new finished amplifier slab shipping and storage container. The new package is designed to maintain an environment of <5% RH to minimize weathering.

  15. Optimization of reinforced concrete slabs

    NASA Technical Reports Server (NTRS)

    Ferritto, J. M.

    1979-01-01

    Reinforced concrete cells composed of concrete slabs and used to limit the effects of accidental explosions during hazardous explosives operations are analyzed. An automated design procedure which considers the dynamic nonlinear behavior of the reinforced concrete of arbitrary geometrical and structural configuration subjected to dynamic pressure loading is discussed. The optimum design of the slab is examined using an interior penalty function. The optimization procedure is presented and the results are discussed and compared with finite element analysis.

  16. Extraordinary wavelength reduction in terahertz graphene-cladded photonic crystal slabs

    PubMed Central

    Williamson, Ian A. D.; Mousavi, S. Hossein; Wang, Zheng

    2016-01-01

    Photonic crystal slabs have been widely used in nanophotonics for light confinement, dispersion engineering, nonlinearity enhancement, and other unusual effects arising from their structural periodicity. Sub-micron device sizes and mode volumes are routine for silicon-based photonic crystal slabs, however spectrally they are limited to operate in the near infrared. Here, we show that two single-layer graphene sheets allow silicon photonic crystal slabs with submicron periodicity to operate in the terahertz regime, with an extreme 100× wavelength reduction from graphene’s large kinetic inductance. The atomically thin graphene further leads to excellent out-of-plane confinement, and consequently photonic-crystal-slab band structures that closely resemble those of ideal two-dimensional photonic crystals, with broad band gaps even when the slab thickness approaches zero. The overall photonic band structure not only scales with the graphene Fermi level, but more importantly scales to lower frequencies with reduced slab thickness. Just like ideal 2D photonic crystals, graphene-cladded photonic crystal slabs confine light along line defects, forming waveguides with the propagation lengths on the order of tens of lattice constants. The proposed structure opens up the possibility to dramatically reduce the size of terahertz photonic systems by orders of magnitude. PMID:27143314

  17. Laser damage tests on InSb photodiodes at 1.064 micron and 0.532 micron

    NASA Technical Reports Server (NTRS)

    Bearman, G. H.; Staller, C.; Mahoney, C.

    1992-01-01

    InSb photodiodes were examined for performance degradation after pulsed laser illumination at 0.532 micron and 1.064 micron. Incident laser powers ranged from 6 x 10 exp-18 micron-watts to 16 micron-watts in a 50 pm diameter spot. Dark current and spectral response were both measured before and after illumination. Dark current measurements were taken with the diode blanked off and viewing only 77 K surfaces. Long term stability tests demonstrated that the blackbody did not exhibit long term drifts. Other tests showed that room temperature variations did not affect the diode signal chain or the digitization electronics used in data acquisition. Results of the experiment show that the diodes did not exhibit changes in dark current or spectral response performance as a result of the laser illumination. A typical change in diode spectral response (before/after laser exposure) was about 0.2 percent +/- 0.2 percent.

  18. The 2-micron plasmid as a nonselectable, stable, high copy number yeast vector

    NASA Technical Reports Server (NTRS)

    Ludwig, D. L.; Bruschi, C. V.

    1991-01-01

    The endogenous 2-microns plasmid of Saccharomyces cerevisiae has been used extensively for the construction of yeast cloning and expression plasmids because it is a native yeast plasmid that is able to be maintained stably in cells at high copy number. Almost invariably, these plasmid constructs, containing some or all 2-microns sequences, exhibit copy number levels lower than 2-microns and are maintained stably only under selective conditions. We were interested in determining if there was a means by which 2-microns could be utilized for vector construction, without forfeiting either copy number or nonselective stability. We identified sites in the 2-microns plasmid that could be used for the insertion of genetic sequences without disrupting 2-microns coding elements and then assessed subsequent plasmid constructs for stability and copy number in vivo. We demonstrate the utility of a previously described 2-microns recombination chimera, pBH-2L, for the manipulation and transformation of 2-microns as a pure yeast plasmid vector. We show that the HpaI site near the STB element in the 2-microns plasmid can be utilized to clone yeast DNA of at least 3.9 kb with no loss of plasmid stability. Additionally, the copy number of these constructs is as high as levels reported for the endogenous 2-microns.

  19. How mantle slabs drive plate tectonics.

    PubMed

    Conrad, Clinton P; Lithgow-Bertelloni, Carolina

    2002-10-01

    The gravitational pull of subducted slabs is thought to drive the motions of Earth's tectonic plates, but the coupling between slabs and plates is not well established. If a slab is mechanically attached to a subducting plate, it can exert a direct pull on the plate. Alternatively, a detached slab may drive a plate by exciting flow in the mantle that exerts a shear traction on the base of the plate. From the geologic history of subduction, we estimated the relative importance of "pull" versus "suction" for the present-day plates. Observed plate motions are best predicted if slabs in the upper mantle are attached to plates and generate slab pull forces that account for about half of the total driving force on plates. Slabs in the lower mantle are supported by viscous mantle forces and drive plates through slab suction. PMID:12364804

  20. How mantle slabs drive plate tectonics.

    PubMed

    Conrad, Clinton P; Lithgow-Bertelloni, Carolina

    2002-10-01

    The gravitational pull of subducted slabs is thought to drive the motions of Earth's tectonic plates, but the coupling between slabs and plates is not well established. If a slab is mechanically attached to a subducting plate, it can exert a direct pull on the plate. Alternatively, a detached slab may drive a plate by exciting flow in the mantle that exerts a shear traction on the base of the plate. From the geologic history of subduction, we estimated the relative importance of "pull" versus "suction" for the present-day plates. Observed plate motions are best predicted if slabs in the upper mantle are attached to plates and generate slab pull forces that account for about half of the total driving force on plates. Slabs in the lower mantle are supported by viscous mantle forces and drive plates through slab suction.

  1. Rheologic Controls on the Dynamic Evolution of Slabs in the Upper Mantle

    NASA Astrophysics Data System (ADS)

    Billen, M.; Hirth, G.

    2004-12-01

    Subduction of tectonic plates is characterized by long-lived subduction zones, asymmetric subduction and slab dip angles of 25--80o in the upper mantle. Several mechanisms proposed to explain the variation in observed dip include large-scale mantle flow, trench roll-back, and interaction of the slab with the transition zone. Previous dynamic models of subduction that include only Newtonian viscosity and moderately strong slabs generally fail to predict subduction angles less than 60--90o at shallow depths (100--300 km). We find that the observed characteristics of subduction are reproduced by viscous flow models, in which the rheologic structure is consistent with experimentally determined flow laws for Newtonian and non-Newtonian visco-plastic deformation of olivine. The properties of the models required to match the observed characteristics of slabs are: non-Newtonian viscosity in the mantle producing a weak mantle wedge (1018--1019~Pa s), a stiff slab interior (1025~Pa s) limited by a plastic yield criterion and a weak plate boundary shear zone (1020--1021~Pa s). The shallow slab dip reaches a minimum of 25--30o for high convergence rates and a stiff slab, without trench roll-back or relative motion of the entire lithosphere with respect to the mantle, suggesting these other mechanisms are not the primary controls on slab geometry. The deep slab dip (350--650 km) decreases as the slab penetrates the stiffer (x10), Newtonian viscosity lower mantle, eventually stabilizing the upper mantle slab geometry.

  2. High Energy 2-micron Laser Developments

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Trieu, Bo C.; Petros, Mulugeta; Bai, Yingxin; Petzar, Paul J.; Koch, Grady J.; Singh, Upendra N.; Kavaya, Michael J.

    2007-01-01

    This viewgraph presentation shows the development of 2-micron solid state lasers. The topics covered include: 1) Overview 2-micron solid state lasers; 2) Modeling and population inversion measurement; 3) Side pump oscillator; and 4) One Joule 2-m Laser.

  3. Diffusive Propagation of Exciton-Polaritons through Thin Crystal Slabs.

    PubMed

    Zaitsev, D A; Il'ynskaya, N D; Koudinov, A V; Poletaev, N K; Nikitina, E V; Egorov, A Yu; Kavokin, A V; Seisyan, R P

    2015-01-01

    If light beam propagates through matter containing point impurity centers, the amount of energy absorbed by the media is expected to be either independent of the impurity concentration N or proportional to N, corresponding to the intrinsic absorption or impurity absorption, respectively. Comparative studies of the resonant transmission of light in the vicinity of exciton resonances measured for 15 few-micron GaAs crystal slabs with different values of N, reveal a surprising tendency. While N spans almost five decimal orders of magnitude, the normalized spectrally-integrated absorption of light scales with the impurity concentration as N(1/6). We show analytically that this dependence is a signature of the diffusive mechanism of propagation of exciton-polaritons in a semiconductor. PMID:26088555

  4. Diffusive Propagation of Exciton-Polaritons through Thin Crystal Slabs

    PubMed Central

    Zaitsev, D. A.; Il’ynskaya, N. D.; Koudinov, A. V.; Poletaev, N. K.; Nikitina, E. V.; Egorov, A. Yu.; Kavokin, A. V.; Seisyan, R. P.

    2015-01-01

    If light beam propagates through matter containing point impurity centers, the amount of energy absorbed by the media is expected to be either independent of the impurity concentration N or proportional to N, corresponding to the intrinsic absorption or impurity absorption, respectively. Comparative studies of the resonant transmission of light in the vicinity of exciton resonances measured for 15 few-micron GaAs crystal slabs with different values of N, reveal a surprising tendency. While N spans almost five decimal orders of magnitude, the normalized spectrally-integrated absorption of light scales with the impurity concentration as N1/6. We show analytically that this dependence is a signature of the diffusive mechanism of propagation of exciton-polaritons in a semiconductor. PMID:26088555

  5. Tethyan subducted slabs under India

    NASA Astrophysics Data System (ADS)

    Van der Voo, Rob; Spakman, Wim; Bijwaard, Harmen

    1999-08-01

    Tomographic imaging of the mantle under Tibet, India and the adjacent Indian Ocean reveals several zones of relatively high P-wave velocities at various depths. Under the Hindu Kush region in northeastern Afghanistan and southern Tajikistan, a regional northward-dipping slab is seen in the entire upper 600 km of the mantle and is apparently still attached to the lithosphere of the Indian plate. Under northern Pakistan this same slab shows a roll-over structure with the deeper portion overturned and dipping southward, as can also be seen in the distribution of earthquake hypocenters. Farther east-southeast (e.g., in the vicinity of Nepal), a well-resolved anomaly below 450 km depth is connected to the slab under the Hindu Kush, but seems to be separated from the lithosphere above 350 km. These upper-mantle anomalies are interpreted as the remnants of delaminated sub-continental lithosphere that went down when Greater India continued to converge northward with Asia after ˜45 Ma. The deeper high-velocity anomalies under the Indian sub-continent appear clearly separated from the shallower ones as well as from each other, and are inferred to represent remnants of oceanic lithospheric slabs that have sunk into the lower mantle and were subsequently overridden by the Indian plate. They occur at depths between 1000 and 2300 km and occasionally descend down to the core-mantle boundary. The anomalies form three parallel WNW-ESE striking zones. We interpret the two southern zones as remnants of oceanic lithosphere that was subducted when the Neo-Tethys Ocean closed between India and Tibet in the Cretaceous and earliest Tertiary. The northern deep-mantle zone under northern Afghanistan, the Himalayas and the Lhasa block in southern Tibet may represent the last-subducted remnant of the Paleo-Tethys Ocean, which is thought to have closed before the Hauterivian stage of the Early Cretaceous. The middle zone continues southeastward as a rather straight high-velocity zone towards

  6. Slab melting versus slab dehydration in subduction-zone magmatism

    PubMed Central

    Mibe, Kenji; Kawamoto, Tatsuhiko; Matsukage, Kyoko N.; Fei, Yingwei; Ono, Shigeaki

    2011-01-01

    The second critical endpoint in the basalt-H2O system was directly determined by a high-pressure and high-temperature X-ray radiography technique. We found that the second critical endpoint occurs at around 3.4 GPa and 770 °C (corresponding to a depth of approximately 100 km in a subducting slab), which is much shallower than the previously estimated conditions. Our results indicate that the melting temperature of the subducting oceanic crust can no longer be defined beyond this critical condition and that the fluid released from subducting oceanic crust at depths greater than 100 km under volcanic arcs is supercritical fluid rather than aqueous fluid and/or hydrous melts. The position of the second critical endpoint explains why there is a limitation to the slab depth at which adakitic magmas are produced, as well as the origin of across-arc geochemical variations of trace elements in volcanic rocks in subduction zones. PMID:21536910

  7. Perforation of thin unreinforced concrete slabs

    SciTech Connect

    Cargile, J.D.; Giltrud, M.E.; Luk, V.K.

    1993-10-01

    This report discusses fourteen tests which were conducted to investigate the perforation of thin unreinforced concrete slabs. The 4340-steel projectile used in the test series is 50.8 mm in diameter, 355.6 mm in length, has a mass of 2.34 kg. and an ogive nose with caliber radius head of 3. The slabs, contained within steel culverts, are 1.52 m in diameter and consist of concrete with a nominal unconfined compressive strength of 38.2 MPa and maxima aggregate size of 9.5 mm. Slab thicknesses are 284.4, 254.0, 215.9 and 127.0 mm. Tests were conducted at impact velocities of about 313 m/s on all slab thicknesses and about 379 and 471 m/s on the 254.0-mm-thick slab. All tests were conducted at normal incidence to the slab. All tests were conducted at normal incidence to the slab. Information obtained from the tests used to determine the loading (deceleration) on the projectile during the perforation process, the velocity-displacement of the projectile as it perforated the slab, and the projectile position as damage occurred on the backface of the slab. The test projectile behaved essentially as a rigid body for all of the tests.

  8. Subducting slabs: Jellyfishes in the Earth's mantle

    NASA Astrophysics Data System (ADS)

    Loiselet, Christelle; Braun, Jean; Husson, Laurent; Le Carlier de Veslud, Christian; Thieulot, Cedric; Yamato, Philippe; Grujic, Djordje

    2010-08-01

    The constantly improving resolution of geophysical data, seismic tomography and seismicity in particular, shows that the lithosphere does not subduct as a slab of uniform thickness but is rather thinned in the upper mantle and thickened around the transition zone between the upper and lower mantle. This observation has traditionally been interpreted as evidence for the buckling and piling of slabs at the boundary between the upper and lower mantle, where a strong contrast in viscosity may exist and cause resistance to the penetration of slabs into the lower mantle. The distribution and character of seismicity reveal, however, that slabs undergo vertical extension in the upper mantle and compression near the transition zone. In this paper, we demonstrate that during the subduction process, the shape of low viscosity slabs (1 to 100 times more viscous than the surrounding mantle) evolves toward an inverted plume shape that we coin jellyfish. Results of a 3D numerical model show that the leading tip of slabs deform toward a rounded head skirted by lateral tentacles that emerge from the sides of the jellyfish head. The head is linked to the body of the subducting slab by a thin tail. A complete parametric study reveals that subducting slabs may achieve a variety of shapes, in good agreement with the diversity of natural slab shapes evidenced by seismic tomography. Our work also suggests that the slab to mantle viscosity ratio in the Earth is most likely to be lower than 100. However, the sensitivity of slab shapes to upper and lower mantle viscosities and densities, which remain poorly constrained by independent evidence, precludes any systematic deciphering of the observations.

  9. Subducting Slabs: Jellyfishes in the Earth's Mantle

    NASA Astrophysics Data System (ADS)

    Loiselet, C.; Braun, J.; Husson, L.; Le Carlier de Veslud, C.; Thieulot, C.; Yamato, P.; Grujic, D.

    2010-12-01

    The constantly improving resolution of geophysical data, seismic tomography and seismicity in particular, shows that the lithosphere does not subduct as a slab of uniform thickness but is rather thinned in the upper mantle and thickened around the transition zone between the upper and lower mantle. This observation has traditionally been interpreted as evidence for the buckling and piling of slabs at the boundary between the upper and lower mantle, where a strong contrast in viscosity may exist and cause resistance to the penetration of slabs into the lower mantle. The distribution and character of seismicity reveal, however, that slabs undergo vertical extension in the upper mantle and compression near the transition zone. In this paper, we demonstrate that during the subduction process, the shape of low viscosity slabs (1 to 100 times more viscous than the surrounding mantle) evolves toward an inverted plume shape that we coin jellyfish. Results of a 3D numerical model show that the leading tip of slabs deform toward a rounded head skirted by lateral tentacles that emerge from the sides of the jellyfish head. The head is linked to the body of the subducting slab by a thin tail. A complete parametric study reveals that subducting slabs may achieve a variety of shapes, in good agreement with the diversity of natural slab shapes evidenced by seismic tomography. Our work also suggests that the slab to mantle viscosity ratio in the Earth is most likely to be lower than 100. However, the sensitivity of slab shapes to upper and lower mantle viscosities and densities, which remain poorly constrained by independent evidence, precludes any systematic deciphering of the observations.

  10. The slab geometry laser. I - Theory

    NASA Technical Reports Server (NTRS)

    Eggleston, J. M.; Kane, T. J.; Kuhn, K.; Byer, R. L.; Unternahrer, J.

    1984-01-01

    Slab geometry solid-state lasers offer significant performance improvements over conventional rod-geometry lasers. A detailed theoretical description of the thermal, stress, and beam-propagation characteristics of a slab laser is presented. The analysis includes consideration of the effects of the zig-zag optical path, which eliminates thermal and stress focusing and reduces residual birefringence.

  11. Slab Houses: Reflections of the Past.

    ERIC Educational Resources Information Center

    Cappetta, Ann

    1990-01-01

    Describes how students, influenced by Victorian architecture, created ceramic slab houses. Students devised a solution to depict the reflective nature of Victorian bay windows. Project incorporates art history, handbuilding, and surface ornamentation. Outlines and illustrates steps involved in making slab houses that can be adapted for use by…

  12. Micron-focused ion beamlets

    NASA Astrophysics Data System (ADS)

    Chowdhury, Abhishek; Bhattacharjee, Sudeep

    2010-05-01

    A multiple beam electrode system (MBES) is used to provide focused ion beamlets of elements from a compact microwave plasma. In this study, a honeycomb patterned plasma electrode with micron size apertures for extracting ion beamlets is investigated. The performance of the MBES is evaluated with the help of two widely adopted and commercially available beam simulation tools, AXCEL-INP and SIMION, where the input parameters are obtained from our experiments. A simple theoretical model based upon electrostatic ray optics is employed to compare the results of the simulations. It is found that the results for the beam focal length agree reasonably well. Different geometries are used to optimize the beam spot size and a beam spot ˜5-10 μm is obtained. The multiple ion beamlets will be used to produce microfunctional surfaces on soft matter like polymers. Additionally, the experimental set-up and plans are presented in the light of above applications.

  13. Fracture of solid state laser slabs

    SciTech Connect

    Marion, J.E.

    1986-07-01

    Fracture due to thermal stress limits the power output potential of modern, high average power slab lasers. Here the criteria for slab fracture and the nature of the surface flaws which constitute the strength-controlling defects are reviewed. Specific fracture data for gadolinium scandium gallium garnet and LHG-5 phosphate glass with different surface finishes are evaluated in the context of assigning appropriate slab operating parameters using Wiebull statistics. These examples illustrate both the danger of design using brittle components without adequate fracture testing, and the inadequacy of design methods which use a fixed safety factor, for this class of materials. Further consideration reveals that operation of slab lasers in contact with an aqueous coolant may lead to strength degradation with time. Finally, the evolution of the failure process in which a characteristic midplane crack forms is outlined, and the pertinent parameters for avoiding slab fracture are identified.

  14. Slab stagnation and detachment under northeast China

    NASA Astrophysics Data System (ADS)

    Honda, Satoru

    2016-03-01

    Results of tomography models around the Japanese Islands show the existence of a gap between the horizontally lying (stagnant) slab extending under northeastern China and the fast seismic velocity anomaly in the lower mantle. A simple conversion from the fast velocity anomaly to the low-temperature anomaly shows a similar feature. This feature appears to be inconsistent with the results of numerical simulations on the interaction between the slab and phase transitions with temperature-dependent viscosity. Such numerical models predict a continuous slab throughout the mantle. I extend previous analyses of the tomography model and model calculations to infer the origins of the gap beneath northeastern China. Results of numerical simulations that take the geologic history of the subduction zone into account suggest two possible origins for the gap: (1) the opening of the Japan Sea led to a breaking off of the otherwise continuous subducting slab, or (2) the western edge of the stagnant slab is the previous subducted ridge, which was the plate boundary between the extinct Izanagi and the Pacific plates. Origin (2) suggesting the present horizontally lying slab has accumulated since the ridge subduction, is preferable for explaining the present length of the horizontally lying slab in the upper mantle. Numerical models of origin (1) predict a stagnant slab in the upper mantle that is too short, and a narrow or non-existent gap. Preferred models require rather stronger flow resistance of the 660-km phase change than expected from current estimates of the phase transition property. Future detailed estimates of the amount of the subducted Izanagi plate and the present stagnant slab would be useful to constrain models. A systematic along-arc variation of the slab morphology from the northeast Japan to Kurile arcs is also recognized, and its understanding may constrain the 3D mantle flow there.

  15. Spectroscopy of the 3 micron emission features

    NASA Technical Reports Server (NTRS)

    Geballe, T. R.; Lacy, J. H.; Persson, S. E.; Mcgregor, P. J.; Soifer, B. T.

    1985-01-01

    High-spectral-resolution observations of the 3.3 and 3.4 microns features in the three planetary nebulae NGC 7027, IC 418, and BD +30 deg 3639, in the H II region S106, and in the 'red rectangle' HD 44179 are presented. The profile of the unidentified 3.3 microns emission feature is similar in all five sources. The unidentified feature previously referred to as the 3.4 microns feature actually consists of two components, a low-level emission from 3.35 to 3.60 microns and a narrow emission peak at 3.40 microns. The strength of the latter feature relative to that of the 3.3 microns feature varies by a a factor of three from source to source. The origin and properties of these features may be explained by further development of the small-grain models of Sellgren (1984) and Leger and Puget (1984).

  16. Sausage oscillations of coronal plasma slabs

    NASA Astrophysics Data System (ADS)

    Hornsey, C.; Nakariakov, V. M.; Fludra, A.

    2014-07-01

    Context. Sausage oscillations are observed in plasma non-uniformities of the solar corona as axisymmetric perturbations of the non-uniformity. Often, these non-uniformities can be modelled as field-aligned slabs of the density enhancement. Aims: We perform parametric studies of sausage oscillations of plasma slabs, aiming to determine the dependence of the oscillation period on its parameters, and the onset of leaky and trapped regimes of the oscillations. Methods: Slabs with smooth transverse profiles of the density of a zero-beta plasma are perturbed by an impulsive localised perturbation of the sausage symmetry. In particular, the slab can contain an infinitely thin current sheet in its centre. The initial value problem is then solved numerically. The numerical results are subject to spectral analysis. The results are compared with analytical solutions for a slab with a step-function profile and also with sausage oscillations of a plasma cylinder. Results: We established that sausage oscillations in slabs generally have the same properties as in plasma cylinders. In the trapped regime, the sausage oscillation period increases with the increase in the longitudinal wavelength. In the leaky regime, the dependence of the period on the wavelength experiences saturation, and the period becomes independent of the wavelength in the long-wavelength limit. In the leaky regime the period is always longer than in the trapped regime. The sausage oscillation period in a slab is always longer than in a cylinder with the same transverse profile. In slabs with steeper transverse profiles, sausage oscillations have longer periods. The leaky regime occurs at shorter wavelengths in slabs with smoother profiles.

  17. Modeling cloth at micron resolution

    NASA Astrophysics Data System (ADS)

    Bala, Kavita

    2014-02-01

    Fabric is one of the most common materials in our everyday lives, and accurately simulating the appearance of cloth is a critical problem in graphics, design, and virtual prototyping. But modeling and rendering fabric is very challenging because fabrics have a very complex structure, and this structure plays an important role in their visual appearance—cloth is made of fibers that are twisted into yarns which are woven into patterns. Light interacting with this complex structure produce the characteristic visual appearance that humans recognize as silk, cotton, or wool. In this paper we present an end-to-end pipeline to model and render fabrics: we introduce a novel modality to create volume models of fabric at micron resolution using CT technology coupled with photographs; a new technique to synthesize models of user-specified designs from such CT scans; and finally, an efficient algorithm to render these complex volumetric models for practical applications. This pipeline produces the most realistic images of virtual cloth to date, and opens the way to bridging the gap between real and virtual fabric appearance.

  18. High Energy 2-Micron Laser Developments

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Trieu, Bo C.; Petros, Mulugeta; Bai, Yingxin; Petzar, Paul J.; Koch, Grady J.; Singh, Upendra N.; Kavaya, Michael J.

    2007-01-01

    A master oscillator power amplifier, high energy Q-switched 2-micron laser system has been recently demonstrated. The laser and amplifiers are all designed in side-pumped rod configuration, pumped by back-cooled conductive packaged GaAlAs diode laser arrays. This 2-micron laser system provides nearly transform limited beam quality.

  19. One Micron Laser Technology Advancements at GSFC

    NASA Technical Reports Server (NTRS)

    Heaps, William S.

    2010-01-01

    This slide presentation reviews the advancements made in one micron laser technology at Goddard Space Flight Center. It includes information about risk factors that are being addressed by GSFC, and overviews of the various programs that GSFC is currently managing that are using 1 micron laser technology.

  20. Constraints of subducted slab geometries on trench migration and subduction velocities: flat slabs and slab curtains in the mantle under Asia

    NASA Astrophysics Data System (ADS)

    Wu, J. E.; Suppe, J.; Renqi, L.; Lin, C.; Kanda, R. V.

    2013-12-01

    The past locations, shapes and polarity of subduction trenches provide first-order constraints for plate tectonic reconstructions. Analogue and numerical models of subduction zones suggest that relative subducting (Vs) and overriding (Vor) plate velocities may strongly influence final subducted slab geometries. Here we have mapped the 3D geometries of subducted slabs in the upper and lower mantle of Asia from global seismic tomography. We have incorporated these slabs into plate tectonic models, which allows us to infer the subducting and overriding plate velocities. We describe two distinct slab geometry styles, ';flat slabs' and ';slab curtains', and show their implications for paleo-trench positions and subduction geometries in plate tectonic reconstructions. When compared to analogue and numerical models, the mapped slab styles show similarities to modeled slabs that occupy very different locations within Vs:Vor parameter space. ';Flat slabs' include large swaths of sub-horizontal slabs in the lower mantle that underlie the well-known northward paths of India and Australia from Eastern Gondwana, viewed in a moving hotspot reference. At India the flat slabs account for a significant proportion of the predicted lost Ceno-Tethys Ocean since ~100 Ma, whereas at Australia they record the existence of a major 8000km by 2500-3000km ocean that existed at ~43 Ma between East Asia, the Pacific and Australia. Plate reconstructions incorporating the slab constraints imply these flat slab geometries were generated when continent overran oceanic lithosphere to produce rapid trench retreat, or in other words, when subducting and overriding velocities were equal (i.e. Vs ~ Vor). ';Slab curtains' include subvertical Pacific slabs near the Izu-Bonin and Marianas trenches that extend from the surface down to 1500 km in the lower mantle and are 400 to 500 km thick. Reconstructed slab lengths were assessed from tomographic volumes calculated at serial cross-sections. The ';slab

  1. THUMPER: The 200 Micron Photometer

    NASA Astrophysics Data System (ADS)

    Rinehart, S. A.; Ade, P. A. R.; Griffin, M. J.; Unger, S. J.; Gear, W. K.; Ward-Thompson, D.

    2000-05-01

    THUMPER, the Two-Hundred Micron Photometer, will be a novel new instrument for use on the JCMT and other submillimetre telescopes. Under the best atmospheric conditions at Mauna Kea, a transmission window at 200μ m opens, with atmospheric transmission better than 25% during very dry weather. THUMPER will take advantage of these conditions to take FIR high-resolution (7'') observations with sensitivites comparable to that of instruments previously flown on the Kuiper Airborne Observatory. Further, because of the steep rise in flux towards short wavelengths of thermal sources (which includes most sources of interest), THUMPER will be able to achieve the same SNR as the 450μ m array of SCUBA in a similar amount of time, with similar angular resolution, a capability not provided by any other facility. This instrument will provide powerful new data for the study of many differnt types of astronomical sources, ranging from YSOs and pre-stellar cores to evolved stars to nearby galaxies. One of the primary difficulties in studying such sources is the fact that they have temperature and density distributions which vary across the source. The submillimetre measurements of SCUBA are a powerful tool to study these sources, but these observations are not able to differentiate between temperature and density variations across sources because they do not sample the peak of the Planck function. The FIR observations of ISO and other space-based missions are of value for examination of the global spectral energy distribution, but because of the poor angular resolution of such facilities, cannot be used to separate the effects of temperature and density variations. THUMPER will provide the high-resolution measurements which are needed to differentiate between these effects, opening a valuable new window for FIR astronomy.

  2. Sensitivity enhancement in photonic crystal slab biosensors.

    PubMed

    El Beheiry, Mohamed; Liu, Victor; Fan, Shanhui; Levi, Ofer

    2010-10-25

    Refractive index sensitivity of guided resonances in photonic crystal slabs is analyzed. We show that modal properties of guided resonances strongly affect spectral sensitivity and quality factors, resulting in substantial enhancement of refractive index sensitivity. A three-fold spectral sensitivity enhancement is demonstrated for suspended slab designs, in contrast to designs with a slab resting over a substrate. Spectral sensitivity values are additionally shown to be unaffected by quality factor reductions, which are common to fabricated photonic crystal nano-structures. Finally, we determine that proper selection of photonic crystal slab design parameters permits biosensing of a wide range of analytes, including proteins, antigens, and cells. These photonic crystals are compatible with large-area biosensor designs, permitting direct access to externally incident optical beams in a microfluidic device.

  3. Crust rheology, slab detachment and topography

    NASA Astrophysics Data System (ADS)

    Duretz, T.; Gerya, T. V.

    2012-04-01

    The collision between continents following the closure of an ocean can lead to the subduction of continental crust. The introduction of buoyant crust within subduction zones triggers the development of extensional stresses in slabs which eventually result in their detachment. The dynamic consequences of slab detachment affects the development of topography, the exhumation of high-pressure rocks and the geodynamic evolution of collision zones. We employ two-dimensional thermo-mechanical modelling in order to study the importance of crustal rheology on the evolution of spontaneous subduction-collision systems and the occurrence of slab detachment. The modelling results indicate that varying the rheological structure of the crust can results in a broad range of collisional evolutions involving slab detachment, delamination (associated to slab rollback), or the combination of both mechanisms. By enhancing mechanical coupling at the Moho, a strong crust leads to the deep subduction of the crust (180 km). These collisions are subjected to slab detachment and subsequent coherent exhumation of the crust accommodated by eduction (inversion of subduction sense) and thrusting. In these conditions, slab detachment promotes the development of a high (> 4.5 km) and narrow (< 200 km) topographic plateau located in the vicinity of the suture. A contrasting style of collision is obtained by employing a weak crustal rheology. The weak mechanical coupling at the Moho promotes the widespread delamination of the lithosphere, preventing slab detachment to occur. Further shortening leads to buckling and thickening of the crust resulting in the development of topographic bulging on the lower plate. Collisions involving rheologically layered crust are characterised by a decoupling level at mid-crustal depths. These initial condition favours the delamination of the upper crust as well as the deep subduction of the lower crust. These collisions are thus successively affected by delamination

  4. Photocatalytic, highly hydrophilic porcelain stoneware slabs

    NASA Astrophysics Data System (ADS)

    Raimondo, M.; Guarini, G.; Zanelli, C.; Marani, F.; Fossa, L.; Dondi, M.

    2011-10-01

    Photocatalytic, highly hydrophilic industrial porcelain stoneware large slabs were realized by deposition of nanostructured TiO2 coatings. Different surface finishing and experimental conditions were considered in order to assess the industrial feasibility. Photocatalytic and wetting behaviour of functionalized slabs mainly depends on surface phase composition in terms of anatase/rutile ratio, this involving - as a key issue - the deposition of TiO2 on industrially sintered products with an additional annealing step to strengthen coatings' performances and durability.

  5. Three-dimensional necking during viscous slab detachment

    NASA Astrophysics Data System (ADS)

    Tscharner, M.; Schmalholz, S. M.; Duretz, T.

    2014-06-01

    We study the three-dimensional (3-D) deformation during detachment of a lithospheric slab with simple numerical models using the finite element method. An initially vertical layer of power law viscous fluid mimics the slab and is surrounded by a linear or power law viscous fluid representing asthenospheric mantle. We quantify the impact of slab size and shape (symmetric/asymmetric) on slab detachment and identify two processes that control the lateral (i.e., along-trench) slab deformation: (1) the horizontal deflection of the lateral, vertical slab sides (> 100 km with velocities up to 16 mm/yr) and (2) the propagation of localized thinning (necking) inside the slab (with velocities >9 cm/yr). The lateral propagation velocity is approximately constant during slab detachment. Larger slabs (here wider than approximately 300 km) detach with rates similar to those predicted by 2-D models, whereas smaller slabs detach slower. Implications for geodynamic processes and interpretations of seismic tomography are discussed.

  6. Method for sampling sub-micron particles

    DOEpatents

    Gay, Don D.; McMillan, William G.

    1985-01-01

    Apparatus and method steps for collecting sub-micron sized particles include a collection chamber and cryogenic cooling. The cooling is accomplished by coil tubing carrying nitrogen in liquid form, with the liquid nitrogen changing to the gas phase before exiting from the collection chamber in the tubing. Standard filters are used to filter out particles of diameter greater than or equal to 0.3 microns; however the present invention is used to trap particles of less than 0.3 micron in diameter. A blower draws air to said collection chamber through a filter which filters particles with diameters greater than or equal to 0.3 micron. The air is then cryogenically cooled so that moisture and sub-micron sized particles in the air condense into ice on the coil. The coil is then heated so that the ice melts, and the liquid is then drawn off and passed through a Buchner funnel where the liquid is passed through a Nuclepore membrane. A vacuum draws the liquid through the Nuclepore membrane, with the Nuclepore membrane trapping sub-micron sized particles therein. The Nuclepore membrane is then covered on its top and bottom surfaces with sheets of Mylar.RTM. and the assembly is then crushed into a pellet. This effectively traps the sub-micron sized particles for later analysis.

  7. Sub-micron particle sampler apparatus

    DOEpatents

    Gay, Don D.; McMillan, William G.

    1987-01-01

    Apparatus and method steps for collecting sub-micron sized particles include a collection chamber and cryogenic cooling. The cooling is accomplished by coil tubing carrying nitrogen in liquid form, with the liquid nitrogen changing to the gas phase before exiting from the collection chamber in the tubing. Standard filters are used to filter out particles of diameter greater than or equal to 0.3 microns; however the present invention is used to trap particles of less than 0.3 micron in diameter. A blower draws air to said collection chamber through a filter which filters particles with diameters greater than or equal to 0.3 micron. The air is then cryogenically cooled so that moisture and sub-micron sized particles in the air condense into ice on the coil. The coil is then heated so that the ice melts, and the liquid is then drawn off and passed through a Buchner funnel where the liquid is passed through a Nuclepore membrane. A vacuum draws the liquid through the Nuclepore membrane, with the Nuclepore membrane trapping sub-micron sized particles therein. The Nuclepore membrane is then covered on its top and bottom surfaces with sheets of Mylar.RTM. and the assembly is then crushed into a pellet. This effectively traps the sub-micron sized particles for later analysis.

  8. Was there a Laramide "flat slab"?

    NASA Astrophysics Data System (ADS)

    Jones, C. H.

    2014-12-01

    Slab-continent interactions drive most non-collisional orogenies; this has led us to usually anticipate that temporal changes or spatial variations in orogenic style are related to changes in the slab, most especially in the slab's dip. This is most dramatically evident for orogenies in the foreland, well away from the trench, such as the Laramide orogeny. However, the physical means of connecting slab geometry to crustal deformation remain obscure. Dickinson and Snyder (1978) and Bird (1984) laid out a conceptually elegant means of creating foreland deformation from shear between a slab and overriding continental lithosphere, but such strong shear removed all of the continental lithosphere in the western U.S. when included in a numerical simulation of flat slab subduction (Bird, 1988), a removal in conflict with observations of volcanic rocks and xenoliths in many locations. Relying on an increase in edge normal stresses results, for the Laramide, in requiring the little-deformed Colorado Plateau to either be unusually strong or to have risen rapidly enough and high enough to balance edge stresses with body forces. Early deformation in the Plateau rules out unusual strength, and the accumulation and preservation of Late Cretaceous near-sea level sedimentary rocks makes profound uplift unlikely (though not impossible). Relying on comparisons with the Sierras Pampeanas is also fraught with problems: the Sierras are not separated from the Andean fold-and-thrust belt by several hundred kilometers of little-deformed crust, nor were they buried under kilometers of marine muds as were large parts of the Laramide foreland. We have instead suggested that some unusual interactions of an obliquely subducting plate with a thick Archean continental root might provide a better explanation than a truly flat slab (Jones et al., 2011). From this, and given that several flat-slab segments today are not associated with foreland orogenesis and noting that direct evidence for truly

  9. Cracking behavior of structural slab bridge decks

    NASA Astrophysics Data System (ADS)

    Baah, Prince

    Bridge deck cracking is a common problem throughout the United States, and it affects the durability and service life of concrete bridges. Several departments of transportation (DOTs) in the United States prefer using continuous three-span solid structural slab bridges without stringers over typical four-lane highways. Recent inspections of such bridges in Ohio revealed cracks as wide as 0.125 in. These measured crack widths are more than ten times the maximum limit recommended in ACI 224R-01 for bridge decks exposed to de-icing salts. Measurements using digital image correlation revealed that the cracks widened under truck loading, and in some cases, the cracks did not fully close after unloading. This dissertation includes details of an experimental investigation of the cracking behavior of structural concrete. Prism tests revealed that the concrete with epoxy-coated bars (ECB) develops the first crack at smaller loads, and develops larger crack widths compared to the corresponding specimens with uncoated (black) bars. Slab tests revealed that the slabs with longitudinal ECB developed first crack at smaller loads, exhibited wider cracks and a larger number of cracks, and failed at smaller ultimate loads compared to the corresponding test slabs with black bars. To develop a preventive measure, slabs with basalt and polypropylene fiber reinforced concrete were also included in the test program. These test slabs exhibited higher cracking loads, smaller crack widths, and higher ultimate loads at failure compared to the corresponding slab specimens without fibers. Merely satisfying the reinforcement spacing requirements given in AASHTO or ACI 318-11 is not adequate to limit cracking below the ACI 224R-01 recommended maximum limit, even though all the relevant design requirements are otherwise met. Addition of fiber to concrete without changing any steel reinforcing details is expected to reduce the severity and extent of cracking in reinforced concrete bridge decks.

  10. History vs. snapshot: how slab morphology relates to slab age evolution

    NASA Astrophysics Data System (ADS)

    Garel, Fanny; Goes, Saskia; Davies, Rhodri; Davies, Huw; Lallemand, Serge; Kramer, Stephan; Wilson, Cian

    2016-04-01

    The age of the subducting plate at the trench ("slab age") spans a wide range, from less than 10 Myr in Central and South America to 150 Myr in the Marianas. The morphology of subducting slab in the upper mantle is also very variable, from slabs stagnating at the top of the lower mantle to slabs penetrating well beyond 1000 km depth. People have looked rather unsucessfully for correlations between slab morphology and subduction parameters, including age at the trench, on the basic assumption that old (thick) plates are likely to generate a large slab pull force that would influence slab dip. Thermo-mechanical models reveal complex feedbacks between temperature, strain rate and rheology, and are able to reproduce the evolution of plate ages as a function of time, subducting plate velocity and trench velocity. In particular, we show how initially young subducting plates can rapidly age at the surface because of a slow sinking velocity. As a consequence, different slab morphologies can exhibit similar ages at the trench provided that subduction history is different. We illustrate how models provide insights into Earth subduction zones for which we have to consider their history (evolution of trench velocity, relative plate ages at time of initiation) in order to unravel their present-day geometry.

  11. The 10 micron spectral structure in comets

    NASA Technical Reports Server (NTRS)

    Lynch, David K.; Russell, Ray W.; Campins, Humberto

    1989-01-01

    The 10 micron spectra of comets Halley (1982i), Wilson (1986l), Kohoutek (1973f) and Bradfield (1987s) are presented and compared. The silicate emission profiles of Halley and Bradfield are seen to be remarkably similar in that both contain a sharp break in the spectrum at 11.3 microns. Comet Bradfield does not show the same double peak structure seen in olivine and reported in Comet Halley be Campins and Ryan (1988) and Bregman, et al. (1987). The authors interpret the 11.3 micron signature as being due to olivine-type dust grains with at least some degree of crystallinity. Olivine alone is not enough to reproduce the shape of the 10 micron structure. However, in view of the authors' past success in fitting interstellar dust features with the emissivity profile obtained from amorphous grains produced by laser-vaporizing olivine, this is a very appealing identification. They note that there are significant variations in olivine spectra due to compositional differences, grain size distribution and related grain temperature variations to make the olivine identification tentative. They further tentatively identify the 9.8 micron feature in Halley as being due to either amorphorous olivine or a phyllosilicate (layer lattice). Neither the spectra of Halley, Kohoutek, nor Bradfield exhibited the 12.2 micron feature seen in Comet Wilson, which may prove diagnostic of the composition or thermal history differences between these comets. IR spectra of various mineral samples are discussed in terms of their match to cometary spectra.

  12. Pulse propagation through a dielectric slab doped with a triple quantum dot nanostructure

    NASA Astrophysics Data System (ADS)

    Nasehi, R.; Mahmoudi, M.; Sahrai, M.

    2016-11-01

    The propagation of an electromagnetic pulse through a dielectric slab doped with a triple quantum dot (QD) nanostructure has been discussed in the presence of electron tunneling. We include the effect of an incoherent pump field in the transmission and reflection of a pulse in a triple QD. It is shown that the reflected and transmitted pulses can be switched from subluminal to superluminal light propagation by changing either the rate of the incoherent pump field or the inter-dot tunneling between QD1, QD2 and QD3 in a slab. Furthermore, it is demonstrated that the inter-dot tunnel coupling can significantly affect the behavior of optical bistability (OB) and optical multi-stability (OM) in a dielectric slab. The obtained results can be used for the development of new types of nanoelectronic devices for realizing the switching process.

  13. Slab tears and intermediate-depth seismicity

    USGS Publications Warehouse

    Meighan, Hallie E.; Ten Brink, Uri; Pulliam, Jay

    2013-01-01

    Active tectonic regions where plate boundaries transition from subduction to strike slip can take several forms, such as triple junctions, acute, and obtuse corners. Well-documented slab tears that are associated with high rates of intermediate-depth seismicity are considered here: Gibraltar arc, the southern and northern ends of the Lesser Antilles arc, and the northern end of Tonga trench. Seismicity at each of these locations occurs, at times, in the form of swarms or clusters, and various authors have proposed that each marks an active locus of tear propagation. The swarms and clusters start at the top of the slab below the asthenospheric wedge and extend 30–60 km vertically downward within the slab. We propose that these swarms and clusters are generated by fluid-related embrittlement of mantle rocks. Focal mechanisms of these swarms generally fit the shear motion that is thought to be associated with the tearing process.

  14. How to measure slab-off and reverse slab prism in spectacle lenses.

    PubMed

    Christoff, Alexander; Guyton, David L

    2007-08-01

    It is well known that new spectacle lenses for the correction of anisometropia can induce diplopia with reading. The difference in the powers of the lenses induces a net prismatic effect that can cause double vision through off-center areas of the lenses. This is particularly bothersome when patients try to read, often noting vertical double vision in attempted downgaze, especially through multifocal add segments. This induced prismatic effect can be compensated at one level of downgaze by the use of slab-off or reverse slab prism. Typically the slab-off correction is ground into the stronger minus, or weaker plus lens. Reverse slab is ground into the weaker minus, or stronger plus, lens. Unfortunately, determining the amount of slab-off prism already incorporated into spectacle lenses is nonintuitive and inconvenient. This usually requires the use of a lens clock, which is not widely accessible to many ophthalmology practices. A simple technique, described in the past but poorly known, is illustrated here for quickly measuring slab-off and reverse slab prism prescription lenses in the clinic with a common manual lens meter.

  15. Oceanic slab melting and mantle metasomatism.

    PubMed

    Scaillet, B; Prouteau, G

    2001-01-01

    Modern plate tectonic brings down oceanic crust along subduction zones where it either dehydrates or melts. Those hydrous fluids or melts migrate into the overlying mantle wedge trigerring its melting which produces arc magmas and thus additional continental crust. Nowadays, melting seems to be restricted to cases of young (< 50 Ma) subducted plates. Slab melts are silicic and strongly sodic (trondhjemitic). They are produced at low temperatures (< 1000 degrees C) and under water excess conditions. Their interaction with mantle peridotite produces hydrous metasomatic phases such as amphibole and phlogopite that can be more or less sodium rich. Upon interaction the slab melt becomes less silicic (dacitic to andesitic), and Mg, Ni and Cr richer. Virtually all exposed slab melts display geochemical evidence of ingestion of mantle material. Modern slab melts are thus unlike Archean Trondhjemite-Tonalite-Granodiorite rocks (TTG), which suggests that both types of magmas were generated via different petrogenetic pathways which may imply an Archean tectonic model of crust production different from that of the present-day, subduction-related, one. PMID:11838241

  16. A Simple Vertical Slab Gel Electrophoresis Apparatus.

    ERIC Educational Resources Information Center

    Carter, J. B.; And Others

    1983-01-01

    Describes an inexpensive, easily constructed, and safe vertical slab gel kit used routinely for sodium dodecyl sulphate-polyacrylamide gel electrophoresis research and student experiments. Five kits are run from a single transformer. Because toxic solutions are used, students are given plastic gloves and closely supervised during laboratory…

  17. Slab Ice Characterization on Martian Richardson Crater

    NASA Astrophysics Data System (ADS)

    Schmidt, F.; Andrieu, F.; Douté, S.

    2016-09-01

    We compare two models: granular and slab in order to study the ice properties in the Richardson crater using spectroscopy. Thanks to radiative transfer modeling, we determine compactness of CO2 ice, grain size, and abundances of water ice and dust.

  18. Oceanic slab melting and mantle metasomatism.

    PubMed

    Scaillet, B; Prouteau, G

    2001-01-01

    Modern plate tectonic brings down oceanic crust along subduction zones where it either dehydrates or melts. Those hydrous fluids or melts migrate into the overlying mantle wedge trigerring its melting which produces arc magmas and thus additional continental crust. Nowadays, melting seems to be restricted to cases of young (< 50 Ma) subducted plates. Slab melts are silicic and strongly sodic (trondhjemitic). They are produced at low temperatures (< 1000 degrees C) and under water excess conditions. Their interaction with mantle peridotite produces hydrous metasomatic phases such as amphibole and phlogopite that can be more or less sodium rich. Upon interaction the slab melt becomes less silicic (dacitic to andesitic), and Mg, Ni and Cr richer. Virtually all exposed slab melts display geochemical evidence of ingestion of mantle material. Modern slab melts are thus unlike Archean Trondhjemite-Tonalite-Granodiorite rocks (TTG), which suggests that both types of magmas were generated via different petrogenetic pathways which may imply an Archean tectonic model of crust production different from that of the present-day, subduction-related, one.

  19. Exploratory 5-micron spectrum of Uranus

    SciTech Connect

    Orton, G.S.; Kaminski, C.D.

    1989-01-01

    The intensity peak at 4.8 microns characterizing the spectrum observed for the disk of Uranus near 5 microns, in June 1987, exhibits steep declines at shorter and longer wavelength. An exploratory discussion is presented of various models in view of these data; it is noted that some component of the radiation must originate near the 140 K atmospheric irrespective of the radiation's origin in sunlight or thermal emission; physical considerations dictate that it be at least partly thermal in origin. One model consistent with the data requires the presence of a cloud top at the 8-bar level. 30 references.

  20. Mantle Response to a Slab Gap and Three-dimensional Slab Interaction in Central America

    NASA Astrophysics Data System (ADS)

    Jadamec, M. A.; Fischer, K. M.

    2013-12-01

    Seismically constrained global slab geometries suggest the Middle America-South American subduction system contains a gap on the order of 500 km separating the east-dipping Cocos and Nazca slabs at depth (Gudmundsson and Sambridge, 1998; Syracuse and Abers, 2006; Hayes et al., 2012). The location of the gap correlates with tectonic features impinging on the Pacific side of the Middle America trench, in particular the incoming young buoyant oceanic lithosphere and oceanic ridges associated with the Galapagos hotspot and Cocos-Nazca spreading center (Protti et al., 1994; Mann et al., 2007; Muller et al., 2008). Moreover, geochemical studies focusing on the arc chemistry in the Central American volcanic front argue for a slab window of some kind in this region (Johnston and Thorkelson, 1997; Abratis and Worner, 2001; Hoernle et al., 2008). We use high-resolution, three-dimensional (3D) geodynamic modeling of the Middle America-South American subduction system to investigate the role of the incoming young oceanic lithosphere and a gap between the Cocos and Nazca slabs in controlling mantle flow velocity and geochemical signatures beneath Central America. The geodynamic models are geographically referenced with the geometry and thermal structure for the overriding and subducting plates based on geological and geophysical observables and constructed with the multi-plate subduction generator code, SlabGenerator (Jadamec and Billen, 2010; Jadamec et al., 2012; Jadamec and Billen, 2012). The viscous flow simulations are solved using the mantle convection finite-element code, CitcomCU (Zhong, 2006), modified by Jadamec and Billen (2010) to take into account the experimentally derived flow law for olivine and allow for variable 3D plate interface geometries and magnitudes of inter-plate coupling. The 3D numerical models indicate the gap between the Cocos and Nazca slabs serves as a conduit for Pacific-Cocos mantle to pass into the Caribbean, with toroidal flow around the

  1. Sub-micron particle sampler apparatus and method for sampling sub-micron particles

    DOEpatents

    Gay, D.D.; McMillan, W.G.

    1984-04-12

    Apparatus and method steps for collecting sub-micron sized particles include a collection chamber and cryogenic cooling. The cooling is accomplished by coil tubing carrying nitrogen in liquid form, with the liquid nitrogen changing to the gas phase before exiting from the collection chamber in the tubing. Standard filters are used to filter out particles of diameter greater than or equal to 0.3 microns; however, the present invention is used to trap particles of less than 0.3 micron in diameter. A blower draws air to said collection chamber through a filter which filters particles with diameters greater than or equal to 0.3 micron. The air is then cryogenically cooled so that moisture and sub-micron sized particles in the air condense into ice on the coil. The coil is then heated so that the ice melts, and the liquid is then drawn off and passed through a Buchner funnel where the liquid is passed through a Nuclepore membrane. A vacuum draws the liquid through the Nuclepore membrane, with the Nuclepore membrane trapping sub-micron sized particles therein. The Nuclepore membrane is then covered on its top and bottom surfaces with sheets of Mylar and the assembly is then crushed into a pellet. This effectively traps the sub-micron sized particles for later analysis. 6 figures.

  2. Application of coherent 10 micron imaging lidar

    SciTech Connect

    Simpson, M.L.; Hutchinson, D.P.; Richards, R.K.; Bennett, C.A.

    1997-04-01

    With the continuing progress in mid-IR array detector technology and high bandwidth fan-outs, i.f. electronics, high speed digitizers, and processing capability, true coherent imaging lidar is becoming a reality. In this paper experimental results are described using a 10 micron coherent imaging lidar.

  3. Efavirenz Dissolution Enhancement I: Co-Micronization

    PubMed Central

    da Costa, Maíra Assis; Seiceira, Rafael Cardoso; Rodrigues, Carlos Rangel; Hoffmeister, Cristiane Rodrigues Drago; Cabral, Lucio Mendes; Rocha, Helvécio Vinícius Antunes

    2012-01-01

    AIDS constitutes one of the most serious infectious diseases, representing a major public health priority. Efavirenz (EFV), one of the most widely used drugs for this pathology, belongs to the Class II of the Biopharmaceutics Classification System for drugs with very poor water solubility. To improve EFV’s dissolution profile, changes can be made to the physical properties of the drug that do not lead to any accompanying molecular modifications. Therefore, the study objective was to develop and characterize systems with efavirenz able to improve its dissolution, which were co-processed with sodium lauryl sulfate (SLS) and polyvinylpyrrolidone (PVP). The technique used was co-micronization. Three different drug:excipient ratios were tested for each of the two carriers. The drug dispersion dissolution results showed significant improvement for all the co-processed samples in comparison to non-processed material and corresponding physical mixtures. The dissolution profiles obtained for dispersion with co-micronized SLS samples proved superior to those of co-micronized PVP, with the proportion (1:0.25) proving the optimal mixture. The improvements may be explained by the hypothesis that formation of a hydrophilic layer on the surface of the micronized drug increases the wettability of the system formed, corroborated by characterization results indicating no loss of crystallinity and an absence of interaction at the molecular level. PMID:24300394

  4. The 11 Micron Emissions of Carbon Stars

    NASA Technical Reports Server (NTRS)

    Goebel, J. H.; Cheeseman, P.; Gerbault, F.

    1995-01-01

    A new classification scheme of the IRAS LRS carbon stars is presented. It comprises the separation of 718 probable carbon stars into 12 distinct self-similar spectral groupings. Continuum temperatures are assigned and range from 470 to 5000 K. Three distinct dust species are identifiable: SiC, alpha:C-H, and MgS. In addition to the narrow 11 + micron emission feature that is commonly attributed to SiC, a broad 11 + micron emission feature, that is correlated with the 8.5 and 7.7 micron features, is found and attributed to alpha:C-H. SiC and alpha:C-H band strengths are found to correlate with the temperature progression among the Classes. We find a spectral sequence of Classes that reflects the carbon star evolutionary sequence of spectral types, or alternatively developmental sequences of grain condensation in carbon-rich circumstellar shells. If decreasing temperature corresponds to increasing evolution, then decreasing temperature corresponds to increasing C/O resulting in increasing amounts of carbon rich dust, namely alpha:C-H. If decreasing the temperature corresponds to a grain condensation sequence, then heterogeneous, or induced nucleation scenarios are supported. SiC grains precede alpha:C-H and form the nuclei for the condensation of the latter material. At still lower temperatures, MgS appears to be quite prevalent. No 11.3 micron PAH features are identified in any of the 718 carbon stars. However, one of the coldest objects, IRAS 15048-5702, and a few others, displays an 11.9 micron emission feature characteristic of laboratory samples of coronene. That feature corresponds to the C-H out of plane deformation mode of aromatic hydrocarbon. This band indicates the presence of unsaturated, sp(sup 3), hydrocarbon bonds that may subsequently evolve into saturated bonds, sp(sup 2), if, and when, the star enters the planetary nebulae phase of stellar evolution. The effusion of hydrogen from the hydrocarbon grain results in the evolution in wavelength of this

  5. The 11 Micron Emissions of Cabon Stars

    NASA Technical Reports Server (NTRS)

    Goebel, J. H.; Cheeseman, P.; Gerbault, F.

    1995-01-01

    A new classification scheme of the IRAS LRS carbon stars is presented. It comprises the separation of 718 probable carbon stars into 12 distinct self-similar spectral groupings. Continuum temperatures are assigned and range from 470 to 5000 K. Three distinct dust species are identifiable: SiC, alpha:C-H, and MgS. In addition to the narrow 11 + micron emission feature that is commonly attributed to SiC, a broad 11 + micron emission feature, that is correlated with the 8.5 and 7.7 micron features, is found and attributed to alpha:C-H. SiC and alpha:C-H band strengths are found to correlate with the temperature progression among the Classes. We find a spectral sequence of Classes that reflects the carbon star evolutionary sequence of spectral types, or alternatively developmental sequences of grain condensation in carbon-rich circumstellar shells. If decreasing temperature corresponds to increasing evolution, then decreasing temperature corresponds to increasing CIO resulting in increasing amounts of carbon rich dust, namely alpha:C-H. If decreasing the temperature corresponds to a grain condensation sequence, then heterogeneous, or induced nucleation scenarios are supported. SiC grains precede alpha:C-H and form the nuclei for the condensation of the latter material. At still lower temperatures, MgS appears to be quite prevalent. No 11.3 micron PAH features are identified in any of the 718 carbon stars. However, one of the coldest objects, IRAS 15048-5702, and a few others, displays an 11.9 micron emission feature characteristic of laboratory samples of coronene. That feature corresponds to the C-H out of plane deformation mode of aromatic hydrocarbon. This band indicates the presence of unsaturated, sp(sup 3), hydrocarbon bonds that may subsequently evolve into saturated bonds, sp(sup 2), if, and when, the star enters the planetary nebulae phase of stellar evolution. The effusion of hydrogen from the hydrocarbon grain results in the evolution in wavelength of this

  6. Subduction zone earthquakes and stress in slabs

    NASA Technical Reports Server (NTRS)

    Vassiliou, M. S.; Hager, B. H.

    1988-01-01

    Simple viscous fluid models of subducting slabs are used to explain observations of the distribution of earthquakes as a function of depth and the orientation of stress axes of deep (greater than 300 km) and intermediate (70-300 km) earthquakes. Results suggest the following features in the distribution of earthquakes with depth: (1) an exponential decrease from shallow depths down to 250 to 300 km, (2) a minimum near 250 to 300 km, and (3) a deep peak below 300 km. Many shallow subducting slabs show only the first characteristic, while deeper extending regions tend to show all three features, with the deep peak varying in position and intensity. These data, combined with the results on the stress orientations of various-depth earthquakes, are consistent with the existence of a barrier of some sort at 670-km depth and a uniform viscosity mantle above this barrier.

  7. Radiation characteristics of tapered slab waveguides

    NASA Astrophysics Data System (ADS)

    Scheggi, A. M.; Falciai, R.; Brenci, M.

    1983-01-01

    The application of ray optics to the evaluation of near- and far-field radiation patterns of a slab waveguide taper is discussed, noting the importance of calculating the power that can be extracted from the core at the end of the waveguide related to the near-field configurations. A multimode, tapered slab waveguide with a homogeneous core and unlimited cladding is considered. It is pointed out that as the ray proceeds on its zigzag path down the taper, its propagation angle increases from reflection to reflection and eventually surpasses the limit angle of total reflection. To obtain an overall idea of the range of ray angles accepted at the smaller end of the taper, the Williamson (1952) method is used; this makes it possible, through a simple geometrical construction, to trace the ray in a linear cone. It is found that the ray-tracing technique can constitute an adequate tool in the analysis and design of tapered multimode waveguides.

  8. Slab photonic crystals with dimer colloid bases

    SciTech Connect

    Riley, Erin K.; Liddell Watson, Chekesha M.

    2014-06-14

    The photonic band gap properties for centered rectangular monolayers of asymmetric dimers are reported. Colloids in suspension have been organized into the phase under confinement. The theoretical model is inspired by the range of asymmetric dimers synthesized via seeded emulsion polymerization and explores, in particular, the band structures as a function of degree of lobe symmetry and degree of lobe fusion. These parameters are varied incrementally from spheres to lobe-tangent dimers over morphologies yielding physically realizable particles. The work addresses the relative scarcity of theoretical studies on photonic crystal slabs with vertical variation that is consistent with colloidal self-assembly. Odd, even and polarization independent gaps in the guided modes are determined for direct slab structures. A wide range of lobe symmetry and degree of lobe fusion combinations having Brillouin zones with moderate to high isotropy support gaps between odd mode band indices 3-4 and even mode band indices 1-2 and 2-3.

  9. The effect of subducting slabs in global shear wave tomography

    NASA Astrophysics Data System (ADS)

    Lu, Chang; Grand, Stephen P.

    2016-05-01

    Subducting slabs create strong short wavelength seismic anomalies in the upper mantle where much of Earth's seismicity is located. As such, they have the potential to bias longer wavelength seismic tomography models. To evaluate the effect of subducting slabs in global tomography, we performed a series of inversions using a global synthetic shear wave traveltime data set for a theoretical slab model based on predicted thermal anomalies within slabs. The spectral element method was applied to predict the traveltime anomalies produced by the 3-D slab model for paths corresponding to our current data used in actual tomography models. Inversion tests have been conducted first using the raw traveltime anomalies to check how well the slabs can be imaged in global tomography without the effect of earthquake mislocation. Our results indicate that most of the slabs can be identified in the inversion result but with smoothed and reduced amplitude. The recovery of the total mass anomaly in slab regions is about 88 per cent. We then performed another inversion test to investigate the effect of mislocation caused by subducting slabs. We found that source mislocation largely removes slab signal and significantly degrades the imaging of subducting slabs-potentially reducing the recovery of mass anomalies in slab regions to only 41 per cent. We tested two source relocation procedures-an iterative relocation inversion and joint relocation inversion. Both methods partially recover the true source locations and improve the inversion results, but the joint inversion method worked significantly better than the iterative method. In all of our inversion tests, the amplitudes of artefact structures in the lower mantle caused by the incorrect imaging of slabs (up to ˜0.5 per cent S velocity anomalies) are comparable to some large-scale lower-mantle heterogeneities seen in global tomography studies. Based on our inversion tests, we suggest including a-priori subducting slabs in the

  10. Implementing slab solar water heating system

    NASA Astrophysics Data System (ADS)

    Raveendran, S. K.; Shen, C. Q.

    2015-08-01

    Water heating contributes a significant part of energy consumption in typical household. One of the most employed technologies today that helps in reducing the energy consumption of water heating would be conventional solar water heating system. However, this system is expensive and less affordable by most family. The main objective of this project is to design and implement an alternative type of solar water heating system that utilize only passive solar energy which is known as slab solar water heating system. Slab solar water heating system is a system that heat up cold water using the solar radiance from the sun. The unique part of this system is that it does not require any form of electricity in order to operate. Solar radiance is converted into heat energy through convection method and cold water will be heated up by using conduction method [1]. The design of this system is governed by the criteria of low implementation cost and energy saving. Selection of material in the construction of a slab solar water heating system is important as it will directly affect the efficiency and performance of the system. A prototype has been built to realize the idea and it had been proven that this system was able to provide sufficient hot water supply for typical household usage at any given time.

  11. Convection in Slab and Spheroidal Geometries

    NASA Technical Reports Server (NTRS)

    Porter, David H.; Woodward, Paul R.; Jacobs, Michael L.

    2000-01-01

    Three-dimensional numerical simulations of compressible turbulent thermally driven convection, in both slab and spheroidal geometries, are reviewed and analyzed in terms of velocity spectra and mixing-length theory. The same ideal gas model is used in both geometries, and resulting flows are compared. The piecewise-parabolic method (PPM), with either thermal conductivity or photospheric boundary conditions, is used to solve the fluid equations of motion. Fluid motions in both geometries exhibit a Kolmogorov-like k(sup -5/3) range in their velocity spectra. The longest wavelength modes are energetically dominant in both geometries, typically leading to one convection cell dominating the flow. In spheroidal geometry, a dipolar flow dominates the largest scale convective motions. Downflows are intensely turbulent and up drafts are relatively laminar in both geometries. In slab geometry, correlations between temperature and velocity fluctuations, which lead to the enthalpy flux, are fairly independent of depth. In spheroidal geometry this same correlation increases linearly with radius over the inner 70 percent by radius, in which the local pressure scale heights are a sizable fraction of the radius. The effects from the impenetrable boundary conditions in the slab geometry models are confused with the effects from non-local convection. In spheroidal geometry nonlocal effects, due to coherent plumes, are seen as far as several pressure scale heights from the lower boundary and are clearly distinguishable from boundary effects.

  12. Fast Waves in Smooth Coronal Slab

    NASA Astrophysics Data System (ADS)

    Lopin, I.; Nagorny, I.

    2015-03-01

    This work investigates the effect of transverse density structuring in coronal slab-like waveguides on the properties of fast waves. We generalized previous results obtained for the exponential and Epstein profiles to the case of an arbitrary transverse density distribution. The criteria are given to determine the possible (trapped or leaky) wave regime, depending on the type of density profile function. In particular, there are plasma slabs with transverse density structuring that support pure trapped fast waves for all wavelengths. Their phase speed is nearly equal to the external Alfvén speed for the typical parameters of coronal loops. Our findings are obtained on the basis of Kneser’s oscillation theorem. To confirm the results, we analytically solved the wave equation evaluated at the cutoff point and the original wave equation for particular cases of transverse density distribution. We also used the WKB method and obtained approximate solutions of the wave equation at the cutoff point for an arbitrary transverse density profile. The analytic results were supplemented by numerical solutions of the obtained dispersion relations. The observed high-quality quasi-periodic pulsations of flaring loops are interpreted in terms of the trapped fundamental fast-sausage mode in a slab-like coronal waveguide.

  13. Floating dielectric slab optical interconnection between metal-dielectric interface surface plasmon polariton waveguides.

    PubMed

    Kang, Minsu; Park, Junghyun; Lee, Il-Min; Lee, Byoungho

    2009-01-19

    A simple and effective optical interconnection which connects two distanced single metal-dielectric interface surface plasmon waveguides by a floating dielectric slab waveguide (slab bridge) is proposed. Transmission characteristics of the suggested structure are numerically studied using rigorous coupled wave analysis, and design rules based on the study are given. In the wave-guiding part, if the slab bridge can support more than the fundamental mode, then the transmission efficiency of the interconnection shows strong periodic dependency on the length of the bridge, due to the multi-mode interference (MMI) effect. Otherwise, only small fluctuation occurs due to the Fabry-Pérot effect. In addition, light beating happens when the slab bridge is relatively short. In the wave-coupling part, on the other hand, gap-assisted transmission occurs at each overlapping region as a consequence of mode hybridization. Periodic dependency on the length of the overlap region also appears due to the MMI effect. According to these results, we propose design principles for achieving both high transmission efficiency and stability with respect to the variation of the interconnection distance, and we show how to obtain the transmission efficiency of 68.3% for the 1mm-long interconnection.

  14. Experimental Testing of a Micron-Scale Laser-Powered Accelerator

    SciTech Connect

    Travish, G.; Arab, E.; Lacroix, U. H.; Rosenzweig, J. B.; Vartanian, N.; Yoder, R. B.

    2009-01-22

    An experimental program to develop, perfect, and demonstrate a micron-scale dielectric-based slab-symmetric accelerator is underway at UCLA. The effort includes parallel development of a particle source to be integrated with the accelerator, forming a monolithic radiation source. We present results from first-round cold tests of the structure resonance on a simplified metal-walled device, containing >100 structure periods in an area of 100x20 {mu}m. The resonance frequency and strength can be observed via reflection and transmission measurements on the drive laser. Initial measurements may be consistent with simulation. We also report on the status of the electron source development and on work toward an acceleration test in an all-dielectric structure.

  15. Micron Accurate Absolute Ranging System: Range Extension

    NASA Technical Reports Server (NTRS)

    Smalley, Larry L.; Smith, Kely L.

    1999-01-01

    The purpose of this research is to investigate Fresnel diffraction as a means of obtaining absolute distance measurements with micron or greater accuracy. It is believed that such a system would prove useful to the Next Generation Space Telescope (NGST) as a non-intrusive, non-contact measuring system for use with secondary concentrator station-keeping systems. The present research attempts to validate past experiments and develop ways to apply the phenomena of Fresnel diffraction to micron accurate measurement. This report discusses past research on the phenomena, and the basis of the use Fresnel diffraction distance metrology. The apparatus used in the recent investigations, experimental procedures used, preliminary results are discussed in detail. Continued research and equipment requirements on the extension of the effective range of the Fresnel diffraction systems is also described.

  16. Supersonic Flows in Micron-Sized Geometries

    NASA Astrophysics Data System (ADS)

    Bayt, Robert; Breuer, Kenneth

    1998-11-01

    The results of experiments and numerical simulations of flows in micromachined converging-diverging nozzles are presented. The nozzles are fabricated using deep Reactive Ion Etching (DRIE) and are typically 20-30 microns at the throat with expansion ratios ranging from 5 to 20. The flow channels are 300 microns deep, resulting in a 10:1 or better aspect ratio at the throat. Experimental measurements of mass flow and thrust vs. pressure ratio are presented demonstrating the presence of choked and supersonic flow in the micron-scale gemoetries. Mass flow and thrust efficiencies are also presented and compared with results from two-dimensional Navier-Stokes simulations. It is found that, while the efficiencies are reasonably large (much better than one might expect, considering the small dimension of the nozzles), the boundary layers have a considerable effect, particularly on the thrust efficiency of the device, due to the relatively large displacement thickness which reduces the effective expansion ratio. The boundary layers at the top and bottom of the nozzles also affect the performance, particularly at low Reynolds numbers. Additional experimental and numerical results are also discussed.

  17. Viscous Dissipation and Criticality of Subducting Slabs

    NASA Astrophysics Data System (ADS)

    Riedel, Mike; Karato, Shun; Yuen, Dave

    2016-04-01

    Rheology of subducting lithosphere appears to be complicated. In the shallow part, deformation is largely accomodated by brittle failure, whereas at greater depth, at higher confining pressures, ductile creep is expected to control slab strength. The amount of viscous dissipation ΔQ during subduction at greater depth, as constrained by experimental rock mechanics, can be estimated on the basis of a simple bending moment equation [1,2] 2ɛ˙0(z) ∫ +h/2 2 M (z) = h ṡ -h/2 4μ(y,z)y dy , (1) for a complex multi-phase rheology in the mantle transition zone, including the effects of a metastable phase transition as well as the pressure, temperature, grain-size and stress dependency of the relevant creep mechanisms; μ is here the effective viscosity and ɛ˙0(z) is a (reference) strain rate. Numerical analysis shows that the maximum bending moment, Mcrit, that can be sustained by a slab is of the order of 1019 Nm per m according to Mcrit˜=σp ∗h2/4, where σp is the Peierl's stress limit of slab materials and h is the slab thickness. Near Mcrit, the amount of viscous dissipation grows strongly as a consequence of a lattice instability of mantle minerals (dislocation glide in olivine), suggesting that thermo-mechanical instabilities become prone to occur at places where a critical shear-heating rate is exceeded, see figure. This implies that the lithosphere behaves in such cases like a perfectly plastic solid [3]. Recently available detailed data related to deep seismicity [4,5] seems to provide support to our conclusion. It shows, e.g., that thermal shear instabilities, and not transformational faulting, is likely the dominating mechanism for deep-focus earthquakes at the bottom of the transition zone, in accordance with this suggested "deep criticality" model. These new findings are therefore briefly outlined and possible implications are discussed. References [1] Riedel, M. R., Karato, S., Yuen, D. A. Criticality of Subducting Slabs. University of Minnesota

  18. Viscous Dissipation and Criticality of Subducting Slabs

    NASA Astrophysics Data System (ADS)

    Riedel, Mike; Karato, Shun; Yuen, Dave

    2016-04-01

    Rheology of subducting lithosphere appears to be complicated. In the shallow part, deformation is largely accomodated by brittle failure, whereas at greater depth, at higher confining pressures, ductile creep is expected to control slab strength. The amount of viscous dissipation ΔQ during subduction at greater depth, as constrained by experimental rock mechanics, can be estimated on the basis of a simple bending moment equation [1,2] 2ɛ˙0(z) ∫ +h/2 2 M (z) = h ṡ ‑h/2 4μ(y,z)y dy , (1) for a complex multi-phase rheology in the mantle transition zone, including the effects of a metastable phase transition as well as the pressure, temperature, grain-size and stress dependency of the relevant creep mechanisms; μ is here the effective viscosity and ɛ˙0(z) is a (reference) strain rate. Numerical analysis shows that the maximum bending moment, Mcrit, that can be sustained by a slab is of the order of 1019 Nm per m according to Mcrit˜=σp ∗h2/4, where σp is the Peierl's stress limit of slab materials and h is the slab thickness. Near Mcrit, the amount of viscous dissipation grows strongly as a consequence of a lattice instability of mantle minerals (dislocation glide in olivine), suggesting that thermo-mechanical instabilities become prone to occur at places where a critical shear-heating rate is exceeded, see figure. This implies that the lithosphere behaves in such cases like a perfectly plastic solid [3]. Recently available detailed data related to deep seismicity [4,5] seems to provide support to our conclusion. It shows, e.g., that thermal shear instabilities, and not transformational faulting, is likely the dominating mechanism for deep-focus earthquakes at the bottom of the transition zone, in accordance with this suggested "deep criticality" model. These new findings are therefore briefly outlined and possible implications are discussed. References [1] Riedel, M. R., Karato, S., Yuen, D. A. Criticality of Subducting Slabs. University of Minnesota

  19. The 1.083 micron tunable CW semiconductor laser

    NASA Technical Reports Server (NTRS)

    Wang, C. S.; Chen, Jan-Shin; Lu, Ken-Gen; Ouyang, Keng

    1991-01-01

    A tunable CW laser is desired to produce light equivalent to the helium spectral line at 1.08 microns. This laser will serve as an optical pumping source for He-3 and He-4 atoms used in space magnetometers. This light source can be fabricated either as a semiconductor laser diode or a pumped solid state laser. Continuous output power of greater than 10 mW is desired. Semiconductor lasers can be thermally tuned, but must be capable of locking onto the helium resonance lines. Solid state lasers must have efficient pumping sources suitable for space configuration. Additional requirements are as follows: space magnetometer applications will include low mass (less than 0.5 kg), low power consumption (less than 0.75 W), and high stability/reliability for long missions (5-10 years).

  20. Tectonic controls on earthquake size distribution and seismicity rate: slab buoyancy and slab bending

    NASA Astrophysics Data System (ADS)

    Nishikawa, T.; Ide, S.

    2014-12-01

    There are clear variations in maximum earthquake magnitude among Earth's subduction zones. These variations have been studied extensively and attributed to differences in tectonic properties in subduction zones, such as relative plate velocity and subducting plate age [Ruff and Kanamori, 1980]. In addition to maximum earthquake magnitude, the seismicity of medium to large earthquakes also differs among subduction zones, such as the b-value (i.e., the slope of the earthquake size distribution) and the frequency of seismic events. However, the casual relationship between the seismicity of medium to large earthquakes and subduction zone tectonics has been unclear. Here we divide Earth's subduction zones into over 100 study regions following Ide [2013] and estimate b-values and the background seismicity rate—the frequency of seismic events excluding aftershocks—for subduction zones worldwide using the maximum likelihood method [Utsu, 1965; Aki, 1965] and the epidemic type aftershock sequence (ETAS) model [Ogata, 1988]. We demonstrate that the b-value varies as a function of subducting plate age and trench depth, and that the background seismicity rate is related to the degree of slab bending at the trench. Large earthquakes tend to occur relatively frequently (lower b-values) in shallower subduction zones with younger slabs, and more earthquakes occur in subduction zones with deeper trench and steeper dip angle. These results suggest that slab buoyancy, which depends on subducting plate age, controls the earthquake size distribution, and that intra-slab faults due to slab bending, which increase with the steepness of the slab dip angle, have influence on the frequency of seismic events, because they produce heterogeneity in plate coupling and efficiently inject fluid to elevate pore fluid pressure on the plate interface. This study reveals tectonic factors that control earthquake size distribution and seismicity rate, and these relationships between seismicity and

  1. Effect of Subducting Slabs in Global Shear Wave Tomography

    NASA Astrophysics Data System (ADS)

    Lu, C.; Grand, S. P.

    2015-12-01

    Subducting slabs represent strong short wavelength seismic anomalies in the upper mantle where much of Earth's seismicity is located. As such, they have the potential to bias longer wavelength seismic tomography models. To evaluate the effect of subducting slabs in global tomography, we performed a series of inversion tests using a global synthetic shear wave travel time dataset for a theoretical slab model based on predicted thermal anomalies within slabs. The spectral element method (SEM) was applied to predict the travel time anomalies produced by the 3D slab model for paths corresponding to our current data used in actual tomography models. Inversion tests have been conducted first using the raw travel time anomalies to check how well the slabs can be imaged in global tomography without the effect of mislocation. Our results indicate that most of the slabs can be identified in the inversion result but with smoothed and reduced amplitude. The recovery of the total mass anomaly in slab regions is about 84%. We then performed another inversion test to investigate the effect of mislocation caused by subducting slabs. We found that source mislocation significantly degrades the imaging of subducting slabs - potentially reducimg the recovery of mass anomalies in slab regions to only 39%. We tested two source relocation procedures - an iterative relocation inversion and joint relocation inversion. Both methods partially recover the true source locations and improve the inversion results, but the joint inversion method worked significantly better than the iterative method. In all of our inversion tests, the amplitude of artifact structures in the lower mantle caused by the incorrect imaging of slabs (up to ~0.5% S velocity anomalies) are comparable to large scale lower mantle heterogeneities seen in global tomography studies.

  2. Mechanisms of deep slab hydration: numerical modeling and implications

    NASA Astrophysics Data System (ADS)

    Faccenda, M.; Gerya, T.; Burlini, L.

    2009-12-01

    Water is a fundamental component of the Earth, affecting its internal structures and dynamics. Sea-water enters the subduction factory via slab hydration that occurs mainly at the trench and is subsequently released in the upper mantle wedge because of slab warming and de-hydration. In the last decades, the scientific research has focused mainly on geophysical processes related to the de-hydration of the slab. However, not much is known on how and to which extent the subducting oceanic plate get hydrated. In order to investigate hydration of the slab, we performed 2D numerical models of a spontaneously bending oceanic plate using I2ELVIS code that account for visco-elasto-plastic rheologies and where fluid flow is regulated by Darci’s law. At the outer rise, bending-related slab faulting occurs, providing a pathway for water percolation in the slab. Faults generally deep trenchward, but antithetic faults are also common. Downward deep fluid flow establishes during brittle extensional deformation at the trench outer rise producing strong variation of the tectonic pressure and causing sub-hydrostatic or even negative pressure gradients along bending related normal faults through which fluids are pumped. The results of the numerical experiment indicate that water can be transported down and stored in the bending area via serpentinization of the normal faults. Deep slab hydration has important implications for the rheological structure, seismicity and seismic anisotropy of the upper mantle because: 1) more water can be stored in the slab producing more enhanced weakening of the mantle wedge, 2) intermediate and deep intra-slab earthquakes can be triggered by slab de-hydration, 3) DHMS phases, able to bring fluids down to the transition zone and lower mantle, could form in the cold core of the slab, 4) the slab could acquire a strong anisotropic fabric responsible for the anisotropic patterns observed at subduction zones.

  3. Hybrid slab-microchannel gel electrophoresis system

    DOEpatents

    Balch, Joseph W.; Carrano, Anthony V.; Davidson, James C.; Koo, Jackson C.

    1998-01-01

    A hybrid slab-microchannel gel electrophoresis system. The hybrid system permits the fabrication of isolated microchannels for biomolecule separations without imposing the constraint of a totally sealed system. The hybrid system is reusable and ultimately much simpler and less costly to manufacture than a closed channel plate system. The hybrid system incorporates a microslab portion of the separation medium above the microchannels, thus at least substantially reducing the possibility of non-uniform field distribution and breakdown due to uncontrollable leakage. A microslab of the sieving matrix is built into the system by using plastic spacer materials and is used to uniformly couple the top plate with the bottom microchannel plate.

  4. Photonic crystal slab quantum cascade detector

    NASA Astrophysics Data System (ADS)

    Reininger, Peter; Schwarz, Benedikt; Harrer, Andreas; Zederbauer, Tobias; Detz, Hermann; Maxwell Andrews, Aaron; Gansch, Roman; Schrenk, Werner; Strasser, Gottfried

    2013-12-01

    In this Letter, we demonstrate the design, fabrication, and characterization of a photonic crystal slab quantum cascade detector (PCS-QCD). By employing a specifically designed resonant cavity, the performance of the photodetector is improved in three distinct ways. The PCS makes the QCD sensitive to surface normal incident light. It resonantly enhances the photon lifetime inside the active zone, thus increasing the photocurrent significantly. And, the construction form of the device inherently decreases the noise. Finally, we compare the characteristics of the PCS-QCD to a PCS - quantum well infrared photodetector and outline the advantages for certain fields of applications.

  5. Numerical quadrature for slab geometry transport algorithms

    SciTech Connect

    Hennart, J.P.; Valle, E. del

    1995-12-31

    In recent papers, a generalized nodal finite element formalism has been presented for virtually all known linear finite difference approximations to the discrete ordinates equations in slab geometry. For a particular angular directions {mu}, the neutron flux {Phi} is approximated by a piecewise function Oh, which over each space interval can be polynomial or quasipolynomial. Here we shall restrict ourselves to the polynomial case. Over each space interval, {Phi} is a polynomial of degree k, interpolating parameters given by in the continuous and discontinuous cases, respectively. The angular flux at the left and right ends and the k`th Legendre moment of {Phi} over the cell considered are represented as.

  6. Automated inspection of hot steel slabs

    DOEpatents

    Martin, Ronald J.

    1985-01-01

    The disclosure relates to a real time digital image enhancement system for performing the image enhancement segmentation processing required for a real time automated system for detecting and classifying surface imperfections in hot steel slabs. The system provides for simultaneous execution of edge detection processing and intensity threshold processing in parallel on the same image data produced by a sensor device such as a scanning camera. The results of each process are utilized to validate the results of the other process and a resulting image is generated that contains only corresponding segmentation that is produced by both processes.

  7. Automated inspection of hot steel slabs

    DOEpatents

    Martin, R.J.

    1985-12-24

    The disclosure relates to a real time digital image enhancement system for performing the image enhancement segmentation processing required for a real time automated system for detecting and classifying surface imperfections in hot steel slabs. The system provides for simultaneous execution of edge detection processing and intensity threshold processing in parallel on the same image data produced by a sensor device such as a scanning camera. The results of each process are utilized to validate the results of the other process and a resulting image is generated that contains only corresponding segmentation that is produced by both processes. 5 figs.

  8. Photonic crystal slab quantum cascade detector

    SciTech Connect

    Reininger, Peter Schwarz, Benedikt; Harrer, Andreas; Zederbauer, Tobias; Detz, Hermann; Maxwell Andrews, Aaron; Gansch, Roman; Schrenk, Werner; Strasser, Gottfried

    2013-12-09

    In this Letter, we demonstrate the design, fabrication, and characterization of a photonic crystal slab quantum cascade detector (PCS-QCD). By employing a specifically designed resonant cavity, the performance of the photodetector is improved in three distinct ways. The PCS makes the QCD sensitive to surface normal incident light. It resonantly enhances the photon lifetime inside the active zone, thus increasing the photocurrent significantly. And, the construction form of the device inherently decreases the noise. Finally, we compare the characteristics of the PCS-QCD to a PCS - quantum well infrared photodetector and outline the advantages for certain fields of applications.

  9. MULTIPLE SETS OF TWIN SLABS ON THE RUN OUT. THE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    MULTIPLE SETS OF TWIN SLABS ON THE RUN OUT. THE RUN OUT INCLUDES THE TRAVELING TORCH WHICH CUTS SLABS TO DESIRED LENGTH, AN IDENTIFICATION SYSTEM TO INDICATE HEAT NUMBER AND TRACE IDENTITY OF EVERY SLAB, AND A DEBURRING DEVICE TO SMOOTH SLABS. AT LEFT OF ROLLS IS THE DUMMY BAR. DUMMY BAR IS INSERTED UP THROUGH CONTAINMENT SECTION INTO MOLD PRIOR TO START OF CAST. WHEN STEEL IS INTRODUCED INTO MOLD IT CONNECTS WITH BAR AS CAST BEGINS, AT RUN OUT DUMMY BAR DISCONNECTS AND IS STORED. - U.S. Steel, Fairfield Works, Continuous Caster, Fairfield, Jefferson County, AL

  10. MULTIPLE SETS OF TWIN SLABS ON THE RUN OUT. THE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    MULTIPLE SETS OF TWIN SLABS ON THE RUN OUT. THE RUN OUT INCLUDES THE TRAVELING TORCH WHICH CUTS SLABS TO DESIRED LENGTH, AN IDENTIFICATION SYSTEM TO INDICATE HEAT NUMBER AND TRACE IDENTITY OF EVERY SLAB, AND A DEBURRING DEVICE TO SMOOTH SLABS. AT LEFT OF ROLLS IS THE DUMMY BAR. DUMMY BAR IS INSERTED UP THROUGH CONTAINMENT SECTION INTO MOLD PRIOR TO START OF CAST. WHEN STEEL IS INTRODUCED INTO MOLD IT CONNECTS WITH BAR AS CAST BEGINS, AT RUN OUT DUMMY BAR DISCONNECTS AND IS STORED - U.S. Steel, Fairfield Works, Continuous Caster, Fairfield, Jefferson County, AL

  11. Thermally induced birefringence in Nd:YAG slab lasers

    SciTech Connect

    Ostermeyer, Martin; Mudge, Damien; Veitch, Peter J.; Munch, Jesper

    2006-07-20

    We study thermally induced birefringence in crystalline Nd:YAG zigzag slab lasers and the associated depolarization losses. The optimum crystallographic orientation of the zigzag slab within the Nd:YAG boule and photoelastic effects in crystalline Nd:YAG slabs are briefly discussed. The depolarization is evaluated using the temperature and stress distributions, calculated using a finite element model, for realistically pumped and cooled slabs of finite dimensions. Jones matrices are then used to calculate the depolarization of the zigzag laser mode. We compare the predictions with measurements of depolarization, and suggest useful criteria for the design of the gain media for such lasers.

  12. Pyrometer method for measuring slab temperature in a reheat furnace

    SciTech Connect

    Rudzki, E.M.; Jackson, R.W.; Martocci, A.P.

    1984-02-21

    A method and apparatus to measure the temperature of a slab in a reheat furnace with increased accuracy using either a single or dual pyrometer system through use of a multiplicity of temperature correction functions involving temperatures of slab and wall, distance between a pyrometer and the slab at which it is aimed, a ratio of air and fuel supplying the furnace heat and radiation interferences. The functions are chosen by a micro-processor in the system dependent on temperature differentials, emissivity setting of the pyrometer, target distance between pyrometer and slab, and air and fuel flow rates existing and fluctuating in the system.

  13. Searching for New Physics from 20 microns to a micron and below

    NASA Astrophysics Data System (ADS)

    Geraci, Andrew; Smullin, Sylvia; Weld, David; Kapitulnik, Aharon; Dimopoulos, Savas

    2004-05-01

    Several recent theoretical ideas suggest that new physics related to gravity may appear at short length scales. For example, light moduli or particles in "large" extra dimensions could mediate macroscopic forces of (super)gravitational strength at length scales below a millimeter. At the 20 microns level, I will discuss the Stanford cantilever experiment (J. Chiaverini, S. J. Smullin, A. A. Geraci, D. M. Weld, A. Kapitulnik, Phys.Rev.Lett. 90, 151101 (2003).), including an improvement involving a magnetic analog which allows force calibration and precision alignment to reduce systematics. I will also discuss some experimental challenges at length scales below a few microns including the Casimir/Van der Waals background, and will describe an experimental prospect to search for new (sub)-micron forces using arrays of trapped Bose-Einstein condensed atoms (Savas Dimopoulos and Andrew A. Geraci, Phys. Rev. D 68, 124021 (2003). ).

  14. Sub-slab vs. Near-slab Soil Vapor Profiles at a Chlorinated Solvent Site (1)

    EPA Science Inventory

    A critical issue in assessing the vapor intrusion pathway is the distribution and migration of VOCs from the subsurface source to the near surface environment. Of particular importance is the influence of a slab. Therefore, EPA/ORD is funding a research program with the primary...

  15. Novel Tests of Gravity Below Fifty Microns

    NASA Astrophysics Data System (ADS)

    Martinez, Gabriela; Johnson, Jeremy; Guerrero, Ian; Hoyle, C. D.

    2016-03-01

    Due to inconsistencies between General Relativity and the Standard Model, tests of gravity remain at the forefront of experimental physics. At Humboldt State University, undergraduates and faculty are designing an experiment sensitive enough to detect gravitational interactions below the 50 micron scale. The experiment measures the twist of a torsion pendulum as an attractor mass is oscillated nearby in a parallel plate configuration, providing time varying gravitational torque on the pendulum. The size and distance dependence of the torque variation will provide a means to determine any deviation from current models of gravity on untested scales. Supported by NSF Grants 1065697 and 1306783.

  16. Influence of weak layer heterogeneity and slab properties on slab tensile failure propensity and avalanche release area

    NASA Astrophysics Data System (ADS)

    Gaume, J.; Chambon, G.; Eckert, N.; Naaim, M.; Schweizer, J.

    2015-04-01

    Dry-snow slab avalanches are generally caused by a sequence of fracture processes, including failure initiation in a weak snow layer underlying a cohesive slab followed by crack propagation within the weak layer (WL) and tensile fracture through the slab. During past decades, theoretical and experimental work has gradually increased our knowledge of the fracture process in snow. However, our limited understanding of crack propagation and fracture arrest propensity prevents the evaluation of avalanche release sizes and thus impedes hazard assessment. To address this issue, slab tensile failure propensity is examined using a mechanically based statistical model of the slab-WL system based on the finite element method. This model accounts for WL heterogeneity, stress redistribution by slab elasticity and possible tensile failure of the slab. Two types of avalanche release are distinguished in the simulations: (1) full-slope release if the heterogeneity is not sufficient to stop crack propagation and trigger a tensile failure within the slab; (2) partial-slope release if fracture arrest and slab tensile failure occur due to the WL heterogeneity. The probability of these two release types is presented as a function of the characteristics of WL heterogeneity and the slab. One of the main outcomes is that, for realistic values of the parameters, the tensile failure propensity is mainly influenced by slab properties. Hard and thick snow slabs are more prone to wide-scale crack propagation and thus lead to larger avalanches (full-slope release). In this case, the avalanche size is mainly influenced by topographical and morphological features such as rocks, trees, slope curvature and the spatial variability of the snow depth as often claimed in the literature.

  17. Plate deformation at depth under northern California: Slab gap or stretched slab?

    USGS Publications Warehouse

    ten Brink, U.S.; Shimizu, N.; Molzer, P.C.

    1999-01-01

    Plate kinematic interpretations for northern California predict a gap in the underlying subducted slab caused by the northward migration of the Pacific-North America-Juan de Fuca triple junction. However, large-scale decompression melting and asthenospheric upwelling to the base of the overlying plate within the postulated gap are not supported by geophysical and geochemical observations. We suggest a model for the interaction between the three plates which is compatible with the observations. In this 'slab stretch' model the Juan de Fuca plate under coastal northern California deforms by stretching and thinning to fill the geometrical gap formed in the wake of the northward migrating Mendocino triple junction. The stretching is in response to boundary forces acting on the plate. The thinning results in an elevated geothermal gradient, which may be roughly equivalent to a 4 Ma oceanic lithosphere, still much cooler than that inferred by the slab gap model. We show that reequilibration of this geothermal gradient under 20-30 km thick overlying plate can explain the minor Neogene volcanic activity, its chemical composition, and the heat flow. In contrast to northern California, geochemical and geophysical consequences of a 'true' slab gap can be observed in the California Inner Continental Borderland offshore Los Angeles, where local asthenospheric upwelling probably took place during the Miocene as a result of horizontal extension and rotation of the overlying plate. The elevated heat flow in central California can be explained by thermal reequilibration of the stalled Monterey microplate under the Coast Ranges, rather than by a slab gap or viscous shear heating in the mantle.

  18. Seeing lumps, sticks, and slabs in silhouettes.

    PubMed

    Willats, J

    1992-01-01

    Marr has suggested that we see three-dimensional (3-D) shapes in silhouettes because we make the implicit assumption that the viewed shapes are generalized cones. One difficulty with this suggestion is that it cannot deal with silhouettes of irregular 3-D shapes like clouds and trees; another is that it only applies to generalized cones with a relatively high length:width ratio. An alternative explanation, suggested by evidence from cross-cultural studies of language, from children's early speech, and from children's early drawings, is that the scene primitives actually used by humans are not generalized cones but 'lumps', 'sticks', and 'slabs', that is, primitives whose only shape properties are their relative extensions in 3-D space. In this paper it is proposed that the implicit assumption we make in interpreting silhouettes is that the extendedness of the silhouette reflects the extendedness of the viewed shape, so that a round region is seen as a lump and a long region is seen as a stick; and that such views seem "natural" because they are the views most likely to be encountered in normal environments. This account is more general than that of Marr because it explains how we interpret silhouettes of all kinds of 3-D shapes, even very irregular ones. Unlike Marr's account, it also deals with flat shapes like slabs and discs, and shows why it is difficult to see these shapes in silhouettes.

  19. Subduction in eastern Indonesia: how many slabs?

    NASA Astrophysics Data System (ADS)

    Milsom, John

    2001-08-01

    Seismicity associated with arc-continent collision in eastern Indonesia testifies to past north-directed subduction of Indian Ocean lithosphere beneath the Banda Sea. The complex patterns of deep seismicity have been cited as evidence for simultaneous south-directed subduction at the northern margin of the sea but this interpretation has not been universally accepted. Recently available recomputations of hypocentre locations have provided increased resolution of eastern Indonesian Wadati-Benioff Zones (WBZs). Shallow to intermediate depth seismic activity around the Banda Arc appears to support models involving subduction of two separate and distinct lithospheric slabs, but between 150 and 500 km the WBZ has a continuous 'shoehorn' shape. This shape confirms the presence of subducted lithosphere beneath Seram, in the north, as well as beneath Timor, in the south, is incompatible with independent subduction of two unconnected plates and implies rapid eastwards retreat of the subduction trace across a now vanished northern spur of the Indian Ocean. This 'roll-back' is unlikely to have been driven by local gravitational forces alone and may have been sustained by injection behind the Banda slab of asthenospheric material escaping from the Molucca Sea arc-arc collision.

  20. Radiative transfer model for contaminated rough slabs.

    PubMed

    Andrieu, François; Douté, Sylvain; Schmidt, Frédéric; Schmitt, Bernard

    2015-11-01

    We present a semi-analytical model to simulate the bidirectional reflectance distribution function (BRDF) of a rough slab layer containing impurities. This model has been optimized for fast computation in order to analyze massive hyperspectral data by a Bayesian approach. We designed it for planetary surface ice studies but it could be used for other purposes. It estimates the bidirectional reflectance of a rough slab of material containing inclusions, overlaying an optically thick media (semi-infinite media or stratified media, for instance granular material). The inclusions are assumed to be close to spherical and constituted of any type of material other than the ice matrix. It can be any other type of ice, mineral, or even bubbles defined by their optical constants. We assume a low roughness and we consider the geometrical optics conditions. This model is thus applicable for inclusions larger than the considered wavelength. The scattering on the inclusions is assumed to be isotropic. This model has a fast computation implementation and thus is suitable for high-resolution hyperspectral data analysis. PMID:26560577

  1. Digital mammography: tradeoffs between 50- and 100-micron pixel size

    NASA Astrophysics Data System (ADS)

    Freedman, Matthew T.; Steller Artz, Dorothy E.; Jafroudi, Hamid; Lo, Shih-Chung B.; Zuurbier, Rebecca A.; Katial, Raj; Hayes, Wendelin S.; Wu, Chris Y.; Lin, Jyh-Shyan; Steinman, Richard M.; Tohme, Walid G.; Mun, Seong K.

    1995-05-01

    Improvements in mammography equipment related to a decrease in pixel size of digital mammography detectors raise questions of the possible effects of these new detectors. Mathematical modeling suggested that the benefits of moving from 100 to 50 micron detectors were slight and might not justify the cost of these new units. Experiments comparing screen film mammography, a storage phosphor 100 micron digital detector, a 50 micron digital breast spot device, 100 micron film digitization and 50 micron film digitization suggests that object conspicuity should be better for digital compared to conventional systems, but that there seemed to be minimal advantage to going from 100 to 50 microns. The 50 micron pixel system appears to provide a slight advantage in object contrast and perhaps in shape definition, but did not allow smaller objects to be detected.

  2. The interstellar 4.62 micron band.

    PubMed

    Pendleton, Y J; Tielens, A G; Tokunaga, A T; Bernstein, M P

    1999-03-01

    We present new 4.5-5.1 micron (2210-1970 cm-1) spectra of embedded protostars, W33 A, AFGL 961 E, AFGL 2136, NGC 7538 IRS 9, and Mon R2 IRS 2, which contain a broad absorption feature located near 4.62 micron (2165 cm-1), commonly referred to in the literature as the "X-C triple bond N" band. The observed peak positions and widths of the interstellar band agree to within 2.5 cm-1 and 5 cm-1, respectively. The strengths of the interstellar 4.62 micrometers band and the ice absorption features in these spectra are not correlated, which suggests a diversity of environmental conditions for the ices we are observing. We explore several possible carriers of the interstellar band and review possible production pathways through far-ultraviolet photolysis (FUV), ion bombardment of interstellar ice analog mixtures, and acid-base reactions. Good fits to the interstellar spectra are obtained with an organic residue produced through ion bombardment of nitrogen-containing ices or with the OCN- ion produced either through acid-base reactions or FUV photolysis of NH3-containing ices.

  3. The 1.2 micron CMOS technology

    NASA Technical Reports Server (NTRS)

    Pina, C. A.

    1985-01-01

    A set of test structures was designed using the Jet Propulsion Laboratory (JPL) test chip assembler and was used to evaluate the first CMOS-bulk foundry runs with feature sizes of 1.2 microns. In addition to the problems associated with the physical scaling of the structures, this geometry provided an additional set of problems, since the design files had to be generated in such a way as to be capable of being processed through p-well, n-well, and twin-well processing lines. This requirement meant that the files containing the geometric design rules as well as the structure design files had to produce process-insensitive designs, a requirement that does not apply to the more mature 3.0-micron CMOS feature size technology. Because of the photolithographic steps required with this feature size, the maximum allowable chip size was 10 x 10 mm, and this chip was divided into 24 project areas, with each area being 1.6 x 1.6 mm in size. The JPL-designed structures occupied 13 out of the 21 allowable project sizes and provided the only test information obtained from these three preliminary runs. The structures were used to successfully evaluate three different manufacturing runs through two separate foundries.

  4. The Two Micron All Sky Survey

    NASA Technical Reports Server (NTRS)

    Kleinmann, S. G.; Lysaght, M. G.; Pughe, W. L.; Schneider, S. E.; Skrutskie, M. F.; Weinberg, M. D.; Price, S. D.; Matthews, K.; Soifer, B. T.; Huchra, J. P.

    1994-01-01

    The Two Micron All Sky Survey (2MASS) will provide a uniform survey of the entire sky at three near-infrared wavebands: J(lambda(sub eff) = 1.25 micrometers), H(lambda(sub eff) = 1.65 micrometers), and K(sub s)(lambda(sub eff) = 2.16 micrometers). A major goal of the survey is to probe large scale structures in the Milky Way and in the Local Universe, exploiting the relatively high transparency of the interstellar medium in the near-infrared, and the high near-infrared luminosities of evolved low- and intermediate-mass stars. A sensitive overview of the near-infrared sky is also an essential next step to maximize the gains achievable with infrared array technology. Our assessment of the astrophysical questions that might be addressed with these new arrays is currently limited by the very bright flux limit of the only preceding large scale near-infrared sky survey, the Two Micron Sky Survey carried out at Caltech in the late 1960's. Near-infrared instruments based on the new array technology have already obtained spectra of objects 1 million times fainter than the limit of the TMSS! This paper summarizes the essential parameters of the 2MASS project and the rationale behind those choices, and gives an overview of results obtained with a prototype camera that has been in operation since May 1992. We conclude with a list of expected data products and a statement of the data release policy.

  5. Scattering of electromagnetic waves from a turbulent plasma slab.

    NASA Technical Reports Server (NTRS)

    Liu, C. H.

    1972-01-01

    Scattering of electromagnetic waves from a turbulent plasma slab is studied. Part of the effects of the multiple scattering is taken into account. The reflection coefficient is found to be increased and its variation with respect to the slab thickness is smoothed out by the random scattering.

  6. 42. PRESSING A SLAB OF CLAY ONTO A MOSAIC MOLD. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    42. PRESSING A SLAB OF CLAY ONTO A MOSAIC MOLD. THE MOLD, WHICH HAS A RAISED DESIGN, LEAVES AND OUTLINE IN THE SLAB, THE PIECES THUS DEFINED, ARE THEN CUT APART TO BE FIRED SEPARATELY AND REASSEMBLED. - Moravian Pottery & Tile Works, Southwest side of State Route 313 (Swamp Road), Northwest of East Court Street, Doylestown, Bucks County, PA

  7. Advanced parameter retrievals for metamaterial slabs using an inhomogeneous model

    NASA Astrophysics Data System (ADS)

    Li Hou, Ling; Chin, Jessie Yao; Yang, Xin Mi; Lin, Xian Qi; Liu, Ruopeng; Xu, Fu Yong; Cui, Tie Jun

    2008-03-01

    The S-parameter retrieval has proved to be an efficient approach to obtain electromagnetic parameters of metamaterials from reflection and transmission coefficients, where a slab of metamaterial with finite thickness is regarded as a homogeneous medium slab with the same thickness [D. R. Smith and S. Schultz, Phys. Rev. B 65, 195104 (2002)]. However, metamaterial structures composed of subwavelength unit cells are different from homogeneous materials, and the conventional retrieval method is, under certain circumstances, not accurate enough. In this paper, we propose an advanced parameter retrieval method for metamaterial slabs using an inhomogeneous model. Due to the coupling effects of unit cells in a metamaterial slab, the roles of edge and inner cells in the slab are different. Hence, the corresponding equivalent medium parameters are different, which results in the inhomogeneous property of the metamaterial slab. We propose the retrievals of medium parameters for edge and inner cells from S parameters by considering two- and three-cell metamaterial slabs, respectively. Then we set up an inhomogeneous three-layer model for arbitrary metamaterial slabs, which is much more accurate than the conventional homogeneous model. Numerical simulations verify the above conclusions.

  8. New MBE buffer for micron- and quarter-micron-gateGaAs MESFETs

    NASA Technical Reports Server (NTRS)

    1988-01-01

    A new buffer layer has been developed that eliminates backgating in GaAs MESFETs and substantially reduces short-channel effects in GaAs MESFETs with 0.27-micron-long gates. The new buffer is grown by molecular beam epitaxy (MBE) at a substrate temperature of 200 C using Ga and As sub 4 beam fluxes. The buffer is crystalline, highly resistive, optically inactive, and can be overgrown with high quality GaAs. GaAs MESFETs with a gate length of 0.27 microns that incorporate the new buffer show improved dc and RF properties in comparison with a similar MESFET with a thin undoped GaAs buffer. To demonstrate the backgating performance improvement afforded by the new buffer, MESFETs were fabricated using a number of different buffer layers and structures. A schematic cross section of the MESFET structure used in this study is shown. The measured gate length, gate width, and source-drain spacing of this device are 2,98, and 5.5 microns, respectively. An ohmic contact, isolated from the MESFET by mesa etching, served as the sidegate. The MESFETs were fabricated in MBE n-GaAs layers grown on the new buffer and also in MBE n-GaAs layers grown on buffer layers of undoped GaAs, AlGaAs, and GaAs/AlGaAs superlattices. All the buffer layers were grown by MBE and are 2 microns thick. The active layer is doped to approximately 2 x 10 to the 17th/cu cm with silicon and is 0.3 microns thick.

  9. Spatial variations of the 3 micron emission features within nebulae

    NASA Technical Reports Server (NTRS)

    Moorhouse, Alan; Geballe, T. R.; Allamandola, Louis J.

    1989-01-01

    The 3 micron spectra is presented for the Orion bar region and the Red Rectangle. In both objects spectra were obtained at more than one location, corresponding to different distances from the excitation source. The well known 3.3 and 3.4 micron emission bands are seen in both objects as well as the recently discovered features at 3.46, 3.51, and 3.57 microns in the Orion bar spectra. The spectra show that the relative strengths of the 3 micron emission features vary within the Orion bar. As distance from the exciting star increases, the 3.4 and 3.51 micron features increase, and the 3.46 micron feature decreases in strength, relative to the strong 3.3 micron feature. These are two possible interpretations which are postulated, each of which involves the breaking of bonds by UV radiation, which removes the modes responsible for the 3.4 micron emission near the star. The two possible bond ruptures are the CH bond in small polycyclic aromatic hydrocarbons (PAHs), or the bond to an aliphatic subgroup. It has to be pointed out that neither interpretation appears entirely satisfactory. The vibrational overtone interpretation cannot explain the presence or behavior of the 3.46 micron feature, whereas the laboratory spectra of aliphatic sidegroups contain many more features in the 3 micron region than are observed in the astronomical sources.

  10. Flat slab deformation caused by interplate suction force

    NASA Astrophysics Data System (ADS)

    Ma, Yiran; Clayton, Robert W.

    2015-09-01

    We image the structure at the southern end of the Peruvian flat subduction zone, using receiver function and surface wave methods. The Nazca slab subducts to ~100 km depth and then remains flat for ~300 km distance before it resumes the dipping subduction. The flat slab closely follows the topography of the continental Moho above, indicating a strong suction force between the slab and the overriding plate. A high-velocity mantle wedge exists above the initial half of the flat slab, and the velocity resumes to normal values before the slab steepens again, indicating the resumption of dehydration and ecologitization. Two prominent midcrust structures are revealed in the 70 km thick crust under the Central Andes: molten rocks beneath the Western Cordillera and the underthrusting Brazilian Shield beneath the Eastern Cordillera.

  11. The Role of Subducting Ridges in the Formation of Flat Slabs: Insights from the Peruvian Flat Slab

    NASA Astrophysics Data System (ADS)

    Knezevic Antonijevic, Sanja; Wagner, Lara; Kumar, Abhash; Beck, Susan; Long, Maureen; Zandt, George; Eakin, Caroline M.

    2015-04-01

    Flattening of the subducting plate is often used to explain various geological features removed far from the subducting margins, including basement-cored uplifts, the cessation of arc volcanism, ignimbrite flare-ups, and the formation of high plateaus and ore deposits [Humphreys et al., 2003; Gutscher et al., 2000; Rosenbaum et al., 2005, Kay and Mpodozis, 2001]. Today, flat slab subduction is observed in central Chile and Peru, representing the modern analogues to the immense paleo-flat slab that subducted beneath the North American continent during the Laramide orogeny (80-55 Ma) [English et al., 2003]. However, how flat slabs form and what controls their inboard and along-strike extent is still poorly understood. To better understand modern and paleo-flat slabs, we focus on the Peruvian flat slab, where the Nazca plate starts to bend at ~90 km depth and travels horizontally for several hundred kilometers beneath the South American plate. Earlier studies propose a correlation between the flat slab and the subducting Nazca Ridge that has been migrating to the south over the past 11 ~Ma [Hampel et al., 2004, Gutscher et al., 2003]. Combining 3D shear wave velocity structure and Rayleigh wave phase anisotropy between ~10° and 18° S, we find that the flat slab has the greatest inboard extent along the track of the subducting Nazca Ridge. North of the ridge track, where the flat slab was initially formed, the flat slab starts to sag, tear and re-initiate steep slab subduction, allowing inflow of warm asthenosphere. Based on our new constraints on the geometry of the subducted plate, we find that the subduction of buoyant oceanic features with overthickened oceanic crust plays a vital role in the formation of flat slabs. We further develop a model of temporal evolution of the Peruvian flab slab that forms as a result of the combined effects of the subducting ridge, trench retreat, and suction forces. Once the buoyant ridge subducts to ~90 km depth, it will fail to

  12. Lithosphere-Mantle Interactions Associated with Flat-Slab Subduction

    NASA Astrophysics Data System (ADS)

    Gerault, M.; Becker, T. W.; Husson, L.; Humphreys, E.

    2014-12-01

    Episodes of flat-slab subduction along the western margin of the Americas may have lead to the formation of intra-continental basins and seas, as well as mountain belts and continental plateaux. Here, we explore some of the consequences of a flat slab morphology, linking dynamic topography and stress patterns in continents to slab and mantle dynamics. Using a 2-D cylindrical code, we develop general models and apply them to the North and South America plates. The results are primarily controlled by the coupling along the slab-continent interface (due to geometry and viscosity), the viscosity of the mantle wedge, and the buoyancy of the subducted lithosphere. All models predict broad subsidence, large deviatoric stresses, and horizontal compression above the tip of the flat slab and the deep slab hinge. In models where the slab lays horizontally for hundreds of kilometers, overriding plate compression focuses on both ends of the flat segment, where normal-dip subduction exerts a direct downward pull. In between, a broad low-stress region gets uplifted proportionally to the amount of coupling between the slab and the continent. Anomalously buoyant seafloor enhances this effect but is not required. The downward bending of the flat slab extremities causes its upper part to undergo extension and the lower part to compress. These results have potential for explaining the existence of relatively undeformed, uplifted regions surrounded by mountain belts, such as in the western U.S. and parts of the Andes. Adequately modeling topography and stress in the unusual setting of southwestern Mexico requires a low-viscosity subduction interface and mantle wedge. Our results are only partially controlled by the buoyancy of the subducting plate, suggesting that the viscosity and the morphology of the slab are important, and that the often-used low resolution and "Stokeslet" models may be missing substantial effects.

  13. Hybrid slab-microchannel gel electrophoresis system

    DOEpatents

    Balch, J.W.; Carrano, A.V.; Davidson, J.C.; Koo, J.C.

    1998-05-05

    A hybrid slab-microchannel gel electrophoresis system is described. The hybrid system permits the fabrication of isolated microchannels for biomolecule separations without imposing the constraint of a totally sealed system. The hybrid system is reusable and ultimately much simpler and less costly to manufacture than a closed channel plate system. The hybrid system incorporates a microslab portion of the separation medium above the microchannels, thus at least substantially reducing the possibility of non-uniform field distribution and breakdown due to uncontrollable leakage. A microslab of the sieving matrix is built into the system by using plastic spacer materials and is used to uniformly couple the top plate with the bottom microchannel plate. 4 figs.

  14. All-polymer photonic crystal slab sensor.

    PubMed

    Hermannsson, Pétur G; Sørensen, Kristian T; Vannahme, Christoph; Smith, Cameron L C; Klein, Jan J; Russew, Maria-Melanie; Grützner, Gabi; Kristensen, Anders

    2015-06-29

    An all-polymer photonic crystal slab sensor is presented, and shown to exhibit narrow resonant reflection with a FWHM of less than 1 nm and a sensitivity of 31 nm/RIU when sensing media with refractive indices around that of water. This results in a detection limit of 4.5 × 10(-6) RIU when measured in conjunction with a spectrometer of 12 pm/pixel resolution. The device is a two-layer structure, composed of a low refractive index polymer with a periodically modulated surface height, covered with a smooth upper-surface high refractive index inorganic-organic hybrid polymer modified with ZrO2based nanoparticles. Furthermore, it is fabricated using inexpensive vacuum-less techniques involving only UV nanoreplication and polymer spin-casting, and is thus well suited for single-use biological and refractive index sensing applications. PMID:26191664

  15. Laser applications in machining slab materials

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoping

    1990-10-01

    Since the invention of the laser back in 1960, laser technology has been extensively applied in many fields of science and technology. These has been a history of nearly two decades of using lasers as an energy source in machining materials, such as cutting, welding, ruling and boring, among other operations. With the development of flexible automation in production, the advantages of laser machining have has grown more and more obvious. The combination of laser technology and computer science further promotes the enhancement and upgrading of laser machining and related equipment. At present, many countries are building high quality laser equipment for machining slab materials, such as the Coherent and Spectra Physics corporations in the United States, the Trumpf Corporation in West Germany, the Amada Corporation in Japan, and the Bystronic Corporation in Switzerland, among other companies.

  16. Assembly of jammed colloidal shells onto micron-sized bubbles by ultrasound.

    PubMed

    Buchcic, C; Tromp, R H; Meinders, M B J; Cohen Stuart, M A

    2015-02-01

    Stabilization of gas bubbles in water by applying solid particles is a promising technique to ensure long-term stability of the dispersion against coarsening. However, the production of large quantities of particle stabilized bubbles is challenging. The delivery of particles to the interface must occur rapidly compared to the typical time scale of coarsening during production. Furthermore, the production route must be able to overcome the energy barriers for interfacial adsorption of particles. Here we demonstrate that ultrasound can be applied to agitate a colloidal dispersion and supply sufficient energy to ensure particle adsorption onto the air-water interface. With this technique we are able to produce micron-sized bubbles, solely stabilized by particles. The interface of these bubbles is characterized by a colloidal shell, a monolayer of particles which adopt a hexagonal packing. The particles are anchored to the interface owing to partial wetting and experience lateral compression due to bubble shrinkage. The combination of both effects stops coarsening once the interface is jammed with particles. As a result, stable bubbles are formed. Individual particles can desorb from the interface upon surfactant addition, though. The latter fact confirms that the particle shell is not covalently linked due to thermal sintering, but is solely held together by capillary interaction. In summary, we show that our ultrasound approach allows for the straightforward creation of micron-sized particle stabilized bubbles with high stability towards coarsening.

  17. 3 micron spectrophotometry of Comet Halley - Evidence for water ice

    NASA Technical Reports Server (NTRS)

    Bregman, Jesse D.; Tielens, A. G. G. M.; Witteborn, Fred C.; Rank, David M.; Wooden, Diane

    1988-01-01

    Structure has been observed in the 3-3.6 micron preperihelion spectrum of Comet Halley consistent with either an absorption band near 3.1 microns or emission near 3.3 microns. The results suggest that a large fraction of the water molecules lost by the comet are initially ejected in the form of small ice particles rather than in the gas phase.

  18. Characteristics of the surface plasma wave in a self-gravitating magnetized dusty plasma slab

    SciTech Connect

    Lee, Myoung-Jae; Jung, Young-Dae

    2015-11-15

    The dispersion properties of surface dust ion-acoustic waves in a self-gravitating magnetized dusty plasma slab are investigated. The dispersion relation is derived by using the low-frequency magnetized dusty dielectric function and the surface wave dispersion integral for the slab geometry. We find that the self-gravitating effect suppresses the frequency of surface dust ion-acoustic wave for the symmetric mode in the long wavelength regime, whereas it hardly changes the frequency for the anti-symmetric mode. As the slab thickness and the wave number increase, the surface wave frequency slowly decreases for the symmetric mode but increases significantly for the anti-symmetric mode. The influence of external magnetic field is also investigated in the case of symmetric mode. We find that the strength of the magnetic field enhances the frequency of the symmetric-mode of the surface plasma wave. The increase of magnetic field reduces the self-gravitational effect and thus the self-gravitating collapse may be suppressed and the stability of dusty objects in space is enhanced.

  19. Near 16 micron CO.sub.2 laser system

    DOEpatents

    Krupke, William F.

    1977-01-01

    Method and apparatus for inducing laser action in CO.sub.2 at a wavelength of 16 microns involving the transition between the 02.sup.0 0 and 01.sup.1 0 states. The population inversion between these two states is achieved by pumping to the 00.sup.0 1 level, suppressing the usual 10.6 micron transition to the 10.sup.0 0 level and encouraging the 9.6 micron transition, thereby populating the 02.sup.0 0 level, as the principal prerequisite for 16 micron laser action between the 02.sup.0 0 and 01.sup.1 0 levels.

  20. Structure of turbulent flow in a slab mold

    NASA Astrophysics Data System (ADS)

    Ramírez-López, Pável; Demedices, L. G.; Dávila, O.; Sánchez-Pérez, R.; Morales, R. D.

    2005-12-01

    The structure of the turbulent flow in a slab mold is studied using a water model, various experimental techniques, and mathematical simulations. The meniscus stability depends on the turbulence structure of the flow in the mold; mathematical simulations using the k-ɛ model and the Reynolds-stress model (RSM) indicate that the latter is better at predicting the meniscus profile for a given casting speed. Reynolds stresses and flow vorticity measured through the particle-image velocimetry (PIV) technique are very close to those predicted by the RSM model, and maximum and minimum values across the jet diameter are reported. The backflow in the upper side of the submerged entry nozzle (SEN) port (for a fixed SEN design) depends on the casting speed and disappears, increasing this process parameter. At low casting speeds, the jet does not report enough dissipation of energy, so the upper flow roll is able to reach the SEN port. At high casting speeds, the jet energy is strongly dissipated inside the SEN port, the narrow wall, and in the mold corner, weakening the momentum transfer of the upper flow roll, which is unable to reach the SEN port. At low casting speeds, meniscus instability is observed very close to the SEN, while at high casting speeds, this instability is observed in the mold corner. An optimum casting speed is reported where complete meniscus stability was observed. The flow structure at the free surface indicates a composite structure of islands with large gradients of velocity at high casting speeds. These velocity gradients are responsible for the meniscus instability.

  1. A modularized pulse forming line using glass-ceramic slabs.

    PubMed

    Wang, Songsong; Shu, Ting; Yang, Hanwu

    2012-08-01

    In our lab, a kind of glass-ceramic slab has been chosen to study the issues of applying solid-state dielectrics to pulse forming lines (PFLs). Limited by the manufacture of the glass-ceramic bulk with large sizes, a single ceramic slab is hard to store sufficient power for the PFL. Therefore, a modularized PFL design concept is proposed in this paper. We regard a single ceramic slab as a module to form each single Blumlein PFL. We connect ceramic slabs in series to enlarge pulse width, and stack the ceramic Blumlein PFLs in parallel to increase the output voltage amplitude. Testing results of a single Blumlein PFL indicate that one ceramic slab contributes about 11 ns to the total pulse width which has a linear relation to the number of the ceramic slabs. We have developed a prototype facility of the 2-stage stacked Blumlein PFL with a length of 2 ceramic slabs. The PFL is dc charged up to 5 kV, and the output voltage pulse of 10 kV, 22 ns is measured across an 8 Ω load. Simulation and experiment results in good agreement demonstrate that the modularized design is reasonable. PMID:22938320

  2. Impact Resistance Behaviour of Banana Fiber Reinforced Slabs

    NASA Astrophysics Data System (ADS)

    Che Muda, Zakaria; Syamsir, Agusril; Nasharuddin Mustapha, Kamal; Rifdy Samsudin, Muhamad; Thiruchelvam, Sivadass; Usman, Fathoni; Beddu, Salmia; Liyana Mohd Kamal, Nur; Ashraful Alam, Md; Birima, Ahmed H.; Zaroog, O. S.

    2016-03-01

    This paper investigate the performance of banana fibre reinforced slabs 300mm × 300mm size with varied thickness subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.25 kg drop at 1 m height has been used in this research work. The main variables for the study is to find the relationship of the impact resistance against the BF contents and slab thickness. A linear relationship has been established between first and ultimate crack resistance against BF contents and slab thickness by the experiment. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the BF contents for a constant spacing for various banana fibre reinforced slab thickness. The increment in BF content has more effect on the first crack resistance than the ultimate crack resistance. The linear relationship has also been established between the service (first) crack and ultimate crack resistance against the various slab thickness. Overall 1.5% BF content with slab thickness of 40 mm exhibit better first and ultimate crack resistance up to 16 times and up to 17 times respectively against control slab (without BF)

  3. Seismic constraints on the morphology of deep slabs

    NASA Astrophysics Data System (ADS)

    Fischer, Karen M.; Jordan, Thomas H.; Creager, Kenneth C.

    1988-05-01

    Residual sphere images from deep earthquakes not only detect the presence of slab-associated velocity anomalies but also lend insight into the flow and deformation of lithosphere subducted into the lower mantle. We have compared travel times from deep events in the Kuril and Mariana arcs with the seismic velocity anomalies implied by kinematical models that thicken the slab perpendicular to its plane by reducing the vertical velocity of the flow with depth. We assume that the details of the deformation (whether the slab buckles, imbricates, fragments, etc.) are averaged out along the ray paths, and hence our models constrain the scale, not the mode, of slab thickening. The deep event travel times are best fit by undeformed models, but the ability of the residual sphere method to resolve slab thickness is limited by ray bending effects. Although the Mariana times are consistent with advective thickening factors of 5 or more, factors larger than 3 are ruled out by the Kuril data. For all models examined, the data require that slab material extends to depths of 900-1000 km. Global tomographic models and regional studies which delineate high-velocity anomalies in the lower mantle beneath zones of Cenozoic subduction are consistent with our results, as is recent work on pulse distortion by slab gradients. Comparison of observed and predicted rates of seismic moment release suggests that if substantial advective thickening does occur, it is largely aseismic.

  4. A modularized pulse forming line using glass-ceramic slabs.

    PubMed

    Wang, Songsong; Shu, Ting; Yang, Hanwu

    2012-08-01

    In our lab, a kind of glass-ceramic slab has been chosen to study the issues of applying solid-state dielectrics to pulse forming lines (PFLs). Limited by the manufacture of the glass-ceramic bulk with large sizes, a single ceramic slab is hard to store sufficient power for the PFL. Therefore, a modularized PFL design concept is proposed in this paper. We regard a single ceramic slab as a module to form each single Blumlein PFL. We connect ceramic slabs in series to enlarge pulse width, and stack the ceramic Blumlein PFLs in parallel to increase the output voltage amplitude. Testing results of a single Blumlein PFL indicate that one ceramic slab contributes about 11 ns to the total pulse width which has a linear relation to the number of the ceramic slabs. We have developed a prototype facility of the 2-stage stacked Blumlein PFL with a length of 2 ceramic slabs. The PFL is dc charged up to 5 kV, and the output voltage pulse of 10 kV, 22 ns is measured across an 8 Ω load. Simulation and experiment results in good agreement demonstrate that the modularized design is reasonable.

  5. Roles of the 2 microns gene products in stable maintenance of the 2 microns plasmid of Saccharomyces cerevisiae.

    PubMed Central

    Reynolds, A E; Murray, A W; Szostak, J W

    1987-01-01

    We have examined the replication and segregation of the Saccharomyces cerevisiae 2 microns circle. The amplification of the plasmid at low copy numbers requires site-specific recombination between the 2 microns inverted repeat sequences catalyzed by the plasmid-encoded FLP gene. No other 2 microns gene products are required. The overexpression of FLP in a strain carrying endogenous 2 microns leads to uncontrolled plasmid replication, longer cell cycles, and cell death. Two different assays show that the level of Flp activity decreases with increasing 2 microns copy number. This regulation requires the products of the REP1 and REP2 genes. These gene products also act together to ensure that 2 microns molecules are randomly segregated between mother and daughter cells at cell division. Images PMID:3316982

  6. NMR Microscopy - Micron-Level Resolution.

    NASA Astrophysics Data System (ADS)

    Kwok, Wing-Chi Edmund

    1990-01-01

    Nuclear Magnetic Resonance Imaging (MRI) has been developed into a powerful and widely used diagnostic tool since the invention of techniques using linear magnetic field gradients in 1973. The variety of imaging contrasts obtainable in MRI, such as spin density, relaxation times and flow rate, gives MRI a significant advantage over other imaging techniques. For common diagnostic applications, image resolutions have been in the order of millimeters with slice thicknesses in centimeters. For many research applications, however, resolutions in the order of tens of microns or smaller are needed. NMR Imaging in these high resolution disciplines is known as NMR microscopy. Compared with conventional microscopy, NMR microscopy has the advantage of being non-invasive and non-destructive. The major obstacles of NMR microscopy are low signal-to-noise ratio and effects due to spin diffusion. To overcome these difficulties, more sensitive RF probes and very high magnetic field gradients have to be used. The most effective way to increase sensitivity is to build smaller probes. Microscope probes of different designs have been built and evaluated. Magnetic field gradient coils that can produce linear field gradients up to 450 Gauss/cm were also assembled. In addition, since microscope probes often employ remote capacitors for RF tuning, the associated signal loss in the transmission line was studied. Imaging experiments have been carried out in a 2.1 Tesla small bore superconducting magnet using the typical two-dimensional spin warp imaging technique. Images have been acquired for both biological and non-biological samples. The highest resolution was obtained in an image of a nerve bundle from the spinal cord of a racoon and has an in-plane resolution of 4 microns. These experiments have demonstrated the potential application of NMR microscopy to pathological research, nervous system study and non -destructive testings of materials. One way to further improve NMR microscopy is

  7. Linear stability of tearing modes

    SciTech Connect

    Cowley, S.C.; Kulsrud, R.M.; Hahm, T.S.

    1986-05-01

    This paper examines the stability of tearing modes in a sheared slab when the width of the tearing layer is much smaller than the ion Larmor radius. The ion response is nonlocal, and the quasineutrality retains its full integal form. An expansion procedure is introduced to solve the quasineutrality equation in powers of the width of the tearing layer over the ion Larmor radius. The expansion procedure is applied to the collisionless and semi-collisional tearing modes. The first order terms in the expansion we find to be strongly stabilizing. The physics of the mode and of the stabilization is discussed. Tearing modes are observed in experiments even though the slab theory predicts stability. It is proposed that these modes grow from an equilibrium with islands at the rational surfaces. If the equilibrium islands are wider than the ion Larmor radius, the mode is unstable when ..delta..' is positive.

  8. May eclogite dehydration cause slab fracturation ?

    NASA Astrophysics Data System (ADS)

    Loury, Chloé; Lanari, Pierre; Rolland, Yann; Guillot, Stéphane; Ganino, Clément

    2015-04-01

    Petrological and geophysical evidences strongly indicate that fluids releases play a fundamental role in subduction zones as in subduction-related seismicity and arc magmatism. It is thus important to assess quantitatively their origin and to try to quantify the amount of such fluids. In HP metamorphism, it is well known that pressure-dependent dehydration reactions occur during the prograde path. Many geophysical models show that the variations in slab physical properties along depth could be linked to these fluid occurrences. However it remains tricky to test such models on natural sample, as it is difficult to assess or model the water content evolution in HP metamorphic rocks. This difficulty is bound to the fact that these rocks are generally heterogeneous, with zoned minerals and preservation of different paragenesis reflecting changing P-T conditions. To decipher the P-T-X(H2O) path of such heterogeneous rocks the concept of local effective bulk (LEB) composition is essential. Here we show how standardized X-ray maps can be used to constrain the scale of the equilibration volume of a garnet porphyroblast and to measure its composition. The composition of this equilibrium volume may be seen as the proportion of the rock likely to react at a given time to reach a thermodynamic equilibrium with the growing garnet. The studied sample is an eclogite coming from the carboniferous South-Tianshan suture (Central Asia) (Loury et al. in press). Compositional maps of a garnet and its surrounding matrix were obtained from standardized X-ray maps processed with the program XMapTools (Lanari et al, 2014). The initial equilibration volume was modeled using LEB compositions combined together with Gibbs free energy minimization. P-T sections were calculated for the next stages of garnet growth taking into account the fractionation of the composition at each stage of garnet growth. The modeled P-T-X(H2O) path indicates that the rock progressively dehydrates during the

  9. Deformation Behavior of Sub-micron and Micron Sized Alumina Particles in Compression.

    SciTech Connect

    Sarobol, Pylin; Chandross, Michael E.; Carroll, Jay; Mook, William; Boyce, Brad; Kotula, Paul Gabriel; McKenzie, Bonnie Beth; Bufford, Daniel Charles; Hall, Aaron Christopher.

    2014-09-01

    The ability to integrate ceramics with other materials has been limited due to high temperature (>800degC) ceramic processing. Recently, researchers demonstrated a novel process , aerosol deposition (AD), to fabricate ceramic films at room temperature (RT). In this process, sub - micro n sized ceramic particles are accelerated by pressurized gas, impacted on the substrate, plastically deformed, and form a dense film under vacuum. This AD process eliminates high temperature processing thereby enabling new coatings and device integration, in which ceramics can be deposited on metals, plastics, and glass. However, k nowledge in fundamental mechanisms for ceramic particle s to deform and form a dense ceramic film is still needed and is essential in advancing this novel RT technology. In this wo rk, a combination of experimentation and atomistic simulation was used to determine the deformation behavior of sub - micron sized ceramic particle s ; this is the first fundamental step needed to explain coating formation in the AD process . High purity, singl e crystal, alpha alumina particles with nominal size s of 0.3 um and 3.0 um were examined. Particle characterization, using transmission electron microscopy (TEM ), showed that the 0.3 u m particles were relatively defect - free single crystals whereas 3.0 u m p articles were highly defective single crystals or particles contained low angle grain boundaries. Sub - micron sized Al 2 O 3 particles exhibited ductile failure in compression. In situ compression experiments showed 0.3um particles deformed plastically, fractured, and became polycrystalline. Moreover, dislocation activit y was observed within the se particles during compression . These sub - micron sized Al 2 O 3 particles exhibited large accum ulated strain (2 - 3 times those of micron - sized particles) before first fracture. I n agreement with the findings from experimentation , a tomistic simulation s of nano - Al 2 O 3 particles showed dislocation slip and

  10. Hybrid stable-unstable resonators for diffusion-cooled CO(2) slab lasers.

    PubMed

    Lapucci, A; Labate, A; Rossetti, F; Mascalchi, S

    1996-06-20

    We present the numerical and experimental study that we carried out to compare the performances of two hybrid stable-unstable resonators for diffusion-cooled CO(2) slab lasers. The two resonators are designed to fit a 320 mm × 60 mm ×2 mm rf-discharge channel and are both guided in the narrow transverse direction. They differ in the other transverse direction, consisting of a positive- or a negative-branch unstable resonator scheme. The two solutions have been characterized in terms of modal structure, power extraction, stability, and quality of the extracted beam. PMID:21102698

  11. Lower mantle seismic scatterers below the subducting Tonga slab: Evidence for slab entrainment of transition zone materials

    NASA Astrophysics Data System (ADS)

    Kaneshima, Satoshi

    2013-09-01

    We show evidence that materials with significantly different elastic properties are juxtaposed in the lower mantle immediately below the subducting Tonga slab (depths ⩽1000 km), like the anomalies preferentially located beneath the lower mantle slabs at other Pacific subduction zones (Kaneshima, 2009). Array analyses of wave form data of short period seismic networks at western United States and Japan for deep earthquakes at the Tonga slab reveal S-to-P scatterers with a size less than the wavelengths (˜10 km). The scatterers are located mostly outside of the slab by several tens of kilometers. Assuming a locally planar interface for the geometry of the scatterers, the amplitudes and polarities of the S-to-P waves are modeled to constrain the properties of the scatterers. We find that the scatterers are steeply dipping, the Vs increases oceanward across the interface, and the Vs contrasts are at least comparable to that associated with the post-spinel transformation (⩾6%). It is unclear at this stage what these subslab scatterers represent, so we discuss about three mechanisms which seem plausible from mantle dynamics viewpoints: (1) they may represent basaltic rocks which were emplaced by partial melting immediately beneath the former oceanic lithosphere-asthenosphere boundary (LAB) before the slab started subducting; (2) alternatively the elastic anomalies of the scatterers may be caused by localized presence of dehydrated water; or (3) the scatterers may correspond to a sharp boundary between fine-grained isotropic rocks in the immediate vicinity of the slab and coarse grained anisotropic rocks more distant from the slab. The presence of pronounced and localized elastic anomalies preferentially beneath the slabs in the shallow lower mantle, whatever its mechanism is, implies that a geophysically observable amount of transition zone material is entrained by the subducting slabs into the lower mantle.

  12. Hybrid Heat Capacity - Moving Slab Laser Concept

    SciTech Connect

    Stappaerts, E A

    2002-04-01

    A hybrid configuration of a heat capacity laser (HCL) and a moving slab laser (MSL) has been studied. Multiple volumes of solid-state laser material are sequentially diode-pumped and their energy extracted. When a volume reaches a maximum temperature after a ''sub-magazine depth'', it is moved out of the pumping region into a cooling region, and a new volume is introduced. The total magazine depth equals the submagazine depth times the number of volumes. The design parameters are chosen to provide high duty factor operation, resulting in effective use of the diode arrays. The concept significantly reduces diode array cost over conventional heat capacity lasers, and it is considered enabling for many potential applications. A conceptual design study of the hybrid configuration has been carried out. Three concepts were evaluated using CAD tools. The concepts are described and their relative merits discussed. Because of reduced disk size and diode cost, the hybrid concept may allow scaling to average powers on the order of 0.5 MW/module.

  13. Rotational flow in tapered slab rocket motors

    NASA Astrophysics Data System (ADS)

    Saad, Tony; Sams, Oliver C.; Majdalani, Joseph

    2006-10-01

    Internal flow modeling is a requisite for obtaining critical parameters in the design and fabrication of modern solid rocket motors. In this work, the analytical formulation of internal flows particular to motors with tapered sidewalls is pursued. The analysis employs the vorticity-streamfunction approach to treat this problem assuming steady, incompressible, inviscid, and nonreactive flow conditions. The resulting solution is rotational following the analyses presented by Culick for a cylindrical motor. In an extension to Culick's work, Clayton has recently managed to incorporate the effect of tapered walls. Here, an approach similar to that of Clayton is applied to a slab motor in which the chamber is modeled as a rectangular channel with tapered sidewalls. The solutions are shown to be reducible, at leading order, to Taylor's inviscid profile in a porous channel. The analysis also captures the generation of vorticity at the surface of the propellant and its transport along the streamlines. It is from the axial pressure gradient that the proper form of the vorticity is ascertained. Regular perturbations are then used to solve the vorticity equation that prescribes the mean flow motion. Subsequently, numerical simulations via a finite volume solver are carried out to gain further confidence in the analytical approximations. In illustrating the effects of the taper on flow conditions, comparisons of total pressure and velocity profiles in tapered and nontapered chambers are entertained. Finally, a comparison with the axisymmetric flow analog is presented.

  14. Magnetoelectric sensor excitations in hexaferrite slabs

    NASA Astrophysics Data System (ADS)

    Zare, Saba; Izadkhah, Hessam; Somu, Sivasubramanian; Vittoria, Carmine

    2015-06-01

    We developed techniques for H- and E-field sensors utilizing single phase magnetoelectric (ME) hexaferrite slabs in the frequency range of 100 Hz to 10 MHz. Novel circuit designs incorporating both spiral and solenoid coils and single and multi-capacitor banks were developed to probe the physics and properties of ME hexaferrites and explore ME effects for sensor detections. Fundamental measurements of the anisotropic tensor elements of the magneto-electric coupling parameter were performed using these novel techniques. In addition, for H-field sensing experiments we measured sensitivity of about 3000 Vm-1/G using solenoid coils and 8000 Vm-1/G using spiral coils. For E-field, sensing the sensitivity was 10-4 G/Vm-1 and using single capacitor detector. Sensitivity for multi-capacitor detectors was measured to be in the order of 10-3 G/Vm-1 and frequency dependent exhibiting a maximum value at ˜1 MHz. Tunability of 0.1%-90% was achieved for tunable inductor applications using both single and multi-capacitors excitation. We believe that significant (˜106) improvements in sensitivity and tunability are feasible with simple modifications of the fabrication process.

  15. 23. Surrender interview site, showing Pemberton Avenue concrete slab road ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    23. Surrender interview site, showing Pemberton Avenue concrete slab road type with gutter (asphalt construction typical on Union and Confederate Avenues), view to the sw. - Vicksburg National Military Park Roads & Bridges, Vicksburg, Warren County, MS

  16. 2. FLAME DEFLECTOR FROM THE REINFORCED CONCRETE SLAB ROOF, VIEW ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. FLAME DEFLECTOR FROM THE REINFORCED CONCRETE SLAB ROOF, VIEW TOWARDS SOUTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-2, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  17. 9. FLAME DEFLECTOR FROM REINFORCED CONCRETE SLAB ROOF, VIEW TOWARDS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. FLAME DEFLECTOR FROM REINFORCED CONCRETE SLAB ROOF, VIEW TOWARDS NORTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-1, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  18. Segmented Hellenic slab rollback driving Aegean deformation and seismicity

    NASA Astrophysics Data System (ADS)

    Sachpazi, M.; Laigle, M.; Charalampakis, M.; Diaz, J.; Kissling, E.; Gesret, A.; Becel, A.; Flueh, E.; Miles, P.; Hirn, A.

    2016-01-01

    The NE dipping slab of the Hellenic subduction is imaged in unprecedented detail using teleseismic receiver function analysis on a dense 2-D seismic array. Mapping of slab geometry for over 300 km along strike and down to 100 km depth reveals a segmentation into dipping panels by along-dip faults. Resolved intermediate-depth seismicity commonly attributed to dehydration embrittlement is shown to be clustered along these faults. Large earthquakes occurrence within the upper and lower plate and at the interplate megathrust boundary show a striking correlation with the slab faults suggesting high mechanical coupling between the two plates. Our results imply that the general slab rollback occurs here in a differential piecewise manner imposing its specific stress and deformation pattern onto the overriding Aegean plate.

  19. DETAIL OF NORTH GUARDRAIL AND EXPANSION JOINT IN CONCRETE SLAB, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF NORTH GUARDRAIL AND EXPANSION JOINT IN CONCRETE SLAB, SHOWING DAMAGED SECTION OF GUARDRAIL AND ALUMINUM REPLACEMENT. VIEW TO NORTHWEST. - Hassayampa Bridge, Spanning Hassayampa River at old U.S. Highway 80, Arlington, Maricopa County, AZ

  20. Radiative Transfer Model for Translucent Slab Ice on Mars

    NASA Astrophysics Data System (ADS)

    Andrieu, F.; Schmidt, F.; Douté, S.; Schmitt, B.; Brissaud, O.

    2016-09-01

    We developed a radiative transfer model that simulates in VIS/NIR the bidirectional reflectance of a contaminated slab layer of ice overlaying a granular medium, under geometrical optics conditions to study martian ices.

  1. Waveform effects of a metastable olivine tongue in subducting slabs

    NASA Technical Reports Server (NTRS)

    Vidale, John E.; Williams, Quentin; Houston, Heidi

    1991-01-01

    Velocity models of subducting slabs with a kinetically-depressed olivine to beta- and gamma-spinel transition are constructed, and the effect that such structures would have on teleseismic P waveforms are examined using a full-wave finite-difference method. These 2D calculations yielded waveforms at a range of distances in the downdip direction. The slab models included a wedge-shaped, low-velocity metastable olivine tongue (MOTO) to a depth of 670 km, as well as a plausible thermal anomaly; one model further included a 10-km-thick fast layer on the surface of the slab. The principal effect of MOTO is to produce grazing reflections at wide angles off the phase boundary, generating a secondary arrival 0 to 4 seconds after the initial arrival depending on the take-off angle. The amplitude and timing of this feature vary with the lateral location of the seismic source within the slab cross-section.

  2. Benchmark study for total enery electrons in thick slabs

    NASA Technical Reports Server (NTRS)

    Jun, I.

    2002-01-01

    The total energy deposition profiles when highenergy electrons impinge on a thick slab of elemental aluminum, copper, and tungsten have been computed using representative Monte Carlo codes (NOVICE, TIGER, MCNP), and compared in this paper.

  3. Analytical and Numerical Solution for a Solidifying Liquid Alloy Slab

    NASA Technical Reports Server (NTRS)

    Antar, B. N.

    1983-01-01

    Numerical and analytical solutions are presented for the temperature and concentration distributions during the solidification of a binary liquid alloy slab. The slab is taken to be of a finite depth but infinite in the horizontal direction. The solidification process is started by withdrawing a fixed amount of heat from the lower surface of the slab. The upper surface of the slab is subjected to both radiation and convective conditions. The solution gives the concentration and temperature profiles and the interface position as a function of time. Due to the smallness of the mass diffusion coefficient in the solid, the numerical solution method breaks down whenever the ratio of the diffusivities in the solid and the liquid falls below a certain value. An analytical method is developed which gives accurate solution for any value of the diffusivity ratio.

  4. 7. REINFORCED CONCRETE SLAB ROOF FROM NORTHWEST EDGE, FLAME DEFLECTOR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    7. REINFORCED CONCRETE SLAB ROOF FROM NORTHWEST EDGE, FLAME DEFLECTOR AT RIGHT, VIEW TOWARDS SOUTHEAST. - Glenn L. Martin Company, Titan Missile Test Facilities, CaptiveTest Stand D-3, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  5. 11. REINFORCED CONCRETE SLAB ROOF, FLAME DEFLECTOR AT RIGHT, CONTROL ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. REINFORCED CONCRETE SLAB ROOF, FLAME DEFLECTOR AT RIGHT, CONTROL BUILDING B AT FAR CENTER RIGHT. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-4, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  6. 9. STONE SLAB CULVERT UNDER CARRIAGE ROAD AT HORSESHOE CURVE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    9. STONE SLAB CULVERT UNDER CARRIAGE ROAD AT HORSESHOE CURVE NEAR GIANT SLIDE TRAIL MARKER ON AROUND-THE-MOUNTAIN LOOP. - Rockefeller Carriage Roads, Mount Desert Island, Bar Harbor, Hancock County, ME

  7. Interior view of groundfloor porch showing exposed concrete floor slab ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Interior view of ground-floor porch showing exposed concrete floor slab system, facing west. - Albrook Air Force Station, Field Officer's Quarters, West side of Dargue Avenue Circle, Balboa, Former Panama Canal Zone, CZ

  8. OVERVIEW LOOKING SOUTH OF CONTAINMENT SYSTEM (TOP), SLAB CASTING MACHINE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    OVERVIEW LOOKING SOUTH OF CONTAINMENT SYSTEM (TOP), SLAB CASTING MACHINE AND RUN OUT WITH TRAVELING TORCH. MACHINE IS CASTING IN TWIN MOLD. - U.S. Steel, Fairfield Works, Continuous Caster, Fairfield, Jefferson County, AL

  9. 31. VIEW OF CONCRETE SLAB AT WEST ENTRANCE OF WALKWAY. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    31. VIEW OF CONCRETE SLAB AT WEST ENTRANCE OF WALKWAY. '1944 JOE LANDETA' SCRATCHED INTO FRESH CONCRETE. March 1987 - Verde River Sheep Bridge, Spanning Verde River (Tonto National Forest), Cave Creek, Maricopa County, AZ

  10. 27. VAL, DETAIL OF LAUNCHER SLAB AND LAUNCHER RAIL WITH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    27. VAL, DETAIL OF LAUNCHER SLAB AND LAUNCHER RAIL WITH 7 INCH DIAMETER HOLE FOR SUPPORT CARRIAGE LOCKING PIN. - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  11. 34. VAL, DETAIL OF STAIRS ON COUNTERWEIGHT SLAB WITH COUNTERWEIGHT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    34. VAL, DETAIL OF STAIRS ON COUNTERWEIGHT SLAB WITH COUNTERWEIGHT CAR RAILS ON RIGHT AND PERSONNEL CAR RAILS ON LEFT. - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  12. 5. VAL LAUNCHER BRIDGE OVER LAUNCHER SLAB TAKEN FROM RESERVOIR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    5. VAL LAUNCHER BRIDGE OVER LAUNCHER SLAB TAKEN FROM RESERVOIR LOOKING NORTH. - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  13. 49. DETAIL VIEW OF SLOPE PREPARATION FOR VARIABLEANGLE LAUNCHER SLAB ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    49. DETAIL VIEW OF SLOPE PREPARATION FOR VARIABLE-ANGLE LAUNCHER SLAB LOOKING NORTH, November 6, 1946. - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  14. 8. VAL COUNTERWEIGHT CAR ON COUNTERWEIGHT SLAB AND CAMERA TOWER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. VAL COUNTERWEIGHT CAR ON COUNTERWEIGHT SLAB AND CAMERA TOWER TAKEN FROM RESERVOIR LOOKING SOUTHWEST. - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  15. Casimir effect for two lossy dispersive dielectric slabs

    NASA Astrophysics Data System (ADS)

    Matloob, R.; Keshavarz, A.; Sedighi, D.

    1999-11-01

    The electromagnetic field is quantized using the Green's-function method for the geometry of a Fabry-Perot cavity, made up of two identical lossy dispersive slabs of finite thickness. The dielectric functions of the slabs are assumed to be an arbitrary complex function of frequency obeying causality requirements. The attractive Casimir force between the two slabs is calculated by the help of the latter field operators, via evaluating the difference between the vacuum pressures on both sides of each slab. Special attention is paid to the limiting case of the Casimir effect for two conducting plates. The Lorentz model of the dielectric function is used to demonstrate the variation of the force in terms of plasma frequency. The Casimir force expression is also related to the imaginary part of the response function. The latter expression is used to introduce the repulsive Casimir force between two conducting plates located inside a Fabry-Perot cavity.

  16. An enhanced HOWFARLESS option for DOSXYZnrc simulations of slab geometries

    SciTech Connect

    Babcock, Kerry; Cranmer-Sargison, Gavin; Sidhu, Narinder

    2008-09-15

    The Monte Carlo code DOSXYZnrc is a valuable instrument for calculating absorbed dose within a three-dimensional Cartesian geometry. DOSXYZnrc includes several variance reduction techniques used to increase the efficiency of the Monte Carlo calculation. One such technique is HOWFARLESS which is used to increase the efficiency of beam commissioning calculations in homogeneous phantoms. The authors present an enhanced version of HOWFARLESS which extends the application to include phantoms inhomogeneous in one dimension. When the enhanced HOWFARLESS was used, efficiency increases as high as 14 times were observed without any loss in dose accuracy. The efficiency gains of an enhanced HOWFARLESS simulation was found to be dependent on both slab geometry and slab density. As the number of two-dimensional voxel layers per slab increases, so does the efficiency gain. Also, as the mass density of a slab is decreased, the efficiency gains increase.

  17. Improved properties of micronized genetically modified flax fibers.

    PubMed

    Dymińska, Lucyna; Szatkowski, Michał; Wróbel-Kwiatkowska, Magdalena; Zuk, Magdalena; Kurzawa, Adam; Syska, Wojciech; Gągor, Anna; Zawadzki, Mirosław; Ptak, Maciej; Mączka, Mirosław; Hanuza, Jerzy; Szopa, Jan

    2012-12-15

    The aim of this study was to investigate the effect of micronization on the compound content, crystalline structure and physicochemical properties of fiber from genetically modified (GM) flax. The GM flax was transformed with three bacterial (Ralstonia eutropha) genes coding for enzymes of polyhydroxybutyrate (PHB) synthesis and under the control of the vascular bundle promoter. The modification resulted in fibers containing the 3-hydroxybutyrate polymer bound to cellulose via hydrogen and ester bonds and antioxidant compounds (phenolic acids, vanillin, vitexin, etc.). The fibers appeared to have a significantly decreased particle size after 20h of ball-milling treatment. Micronized fibers showed reduced phenolic contents and antioxidant capacity compared to the results for untreated fibers. An increased level of PHB was also detected. Micronization introduces structural changes in fiber constituents (cellulose, hemicellulose, pectin, lignin, PHB) and micronized fibers exhibit more functional groups (hydroxyl, carboxyl) derived from those constituents. It is thus concluded that micronization treatments improve the functional properties of the fiber components.

  18. High frequency seismic waves and slab structures beneath Italy

    NASA Astrophysics Data System (ADS)

    Sun, Daoyuan; Miller, Meghan S.; Piana Agostinetti, Nicola; Asimow, Paul D.; Li, Dunzhu

    2014-04-01

    Tomographic images indicate a complicated subducted slab structure beneath the central Mediterranean where gaps in fast velocity anomalies in the upper mantle are interpreted as slab tears. The detailed shape and location of these tears are important for kinematic reconstructions and understanding the evolution of the subduction system. However, tomographic images, which are produced by smoothed, damped inversions, will underestimate the sharpness of the structures. Here, we use the records from the Italian National Seismic Network (IV) to study the detailed slab structure. The waveform records for stations in Calabria show large amplitude, high frequency (f>5 Hz) late arrivals with long coda after a relatively low-frequency onset for both P and S waves. In contrast, the stations in the southern and central Apennines lack such high frequency arrivals, which correlate spatially with the central Apennines slab window inferred from tomography and receiver function studies. Thus, studying the high frequency arrivals provides an effective way to investigate the structure of slab and detect possible slab tears. The observed high frequency arrivals in the southern Italy are the strongest for events from 300 km depth and greater whose hypocenters are located within the slab inferred from fast P-wave velocity perturbations. This characteristic behavior agrees with previous studies from other tectonic regions, suggesting the high frequency energy is generated by small scale heterogeneities within the slab which act as scatterers. Furthermore, using a 2-D finite difference (FD) code, we calculate synthetic seismograms to search for the scale, shape and velocity perturbations of the heterogeneities that may explain features observed in the data. Our preferred model of the slab heterogeneities beneath the Tyrrhenian Sea has laminar structure parallel to the slab dip and can be described by a von Kármán function with a down-dip correlation length of 10 km and 0.5 km in

  19. The fundamental constants of orthotropic affine plate/slab equations

    NASA Technical Reports Server (NTRS)

    Brunelle, E. J.

    1984-01-01

    The global constants associated with orthotropic slab/plate equations are discussed, and the rotational behavior of the modulus/compliance components associated with orthotropic slabs/plates are addressed. It is concluded that one cluster constant is less than or equal to unity for all physically possible materials. Rotationally anomalous behavior is found in two materials, and a simple inequality which can be used to identify regular or anomalous behavior is presented and discussed in detail.

  20. Numerical modeling on the temperature fluctuation and thermo-stress development of the continuously cast steel thin-slab

    SciTech Connect

    Yang, B.J.; Liu, W.T.; Su, J.Y.

    1995-12-31

    The present paper is aimed on modeling the fluctuation of surface temperature and thermo-stress development of the continuously cast steel thin-slab in the secondary cooling system. In the heat transfer model, the spray cooling feature, roll contact and so on are considered to reveal the temperature fluctuation on the solidified surface of thin slab during passing through the secondary cooling zones. The slice-traveling method was used for solidification process to calculate the temperature distribution. The thermo-stress in the solidified shell has simulated by using 2-dimensional thermo-elastic and viscoplastic model incorporating the temperature dependent material properties. The effects of the ferropressure, roll constraint, temperature fluctuation of slab surface on stress development are considered according to the practical operating variables, and a comparison of the stress development at the different temperature distributions has been performed. The computed results have shown that the stress development and surface crack tendency under the conditions of the smooth temperature distribution and real fluctuation distribution are significantly different. In addition, the time-step automatically controlling method for the simulation of the thermo-stress fluctuation development has developed, and it works well to guarantee the computational stability and convergence in modeling the stress development of continuously cast thin-slab at a high casting speed when loading the big fluctuation of temperature.

  1. Characterizing Seismic Anisotropy across the Peruvian Flat-Slab Subduction Zone: Implications for the Dynamics of Flat-Slabs

    NASA Astrophysics Data System (ADS)

    Eakin, Caroline; Long, Maureen; Beck, Susan; Wagner, Lara; Tavera, Hernando

    2014-05-01

    Although 10% of subduction zones worldwide today exhibit shallow or flat subduction, we are yet to fully understand how and why these slabs go flat. An excellent study location for such a problem is in Peru, where the largest region of flat-subduction currently exists, extending ~1500 km in length (from 3 °S to 15 °S) and ~300 km in width. Across this region we investigate the pattern of seismic anisotropy, an indicator for past and/or ongoing deformation in the upper mantle. To achieve this we conduct shear wave splitting analyzes at 40 broadband stations from the PULSE project (PerU Lithosphere and Slab Experiment). These stations were deployed for 2+ years across the southern half of the Peruvian flat-slab region. We present detailed shear wave splitting results for both teleseismic events (such as SKS, SKKS, PKS, sSKS) that sample the upper mantle column beneath the stations as well as direct S from local events that constrain anisotropy in the upper portion of the subduction zone. We analyze the variability of our results with respect to initial polarizations, ray paths, and frequency content as well as spatial variability between stations as the underlying slab morphology changes. Teleseismic results show predominately NW-SE fast polarizations (trench oblique to sub-parallel) over the flat-slab region east of Lima. These results are consistent with observations of more complex multi-layered anisotropy beneath a nearby permanent station (NNA) that suggests a trench-perpendicular fast direction in the lowest layer in the sub-slab mantle. Further south, towards the transition to steeper subduction, the splitting pattern becomes increasingly dominated by null measurements. Over to the east however, beyond Cuzco, where the mantle wedge might begin to play a role, we record fast polarizations quasi-parallel to the local slab contours. Local S results indicate the presence of weak (delay times typically less than 0.5 seconds) and heterogeneous supra-slab

  2. Scaling of Electron Thermal Conductivity during the Transition between Slab and Mixed Slab-Toroidal ETG Mode

    NASA Astrophysics Data System (ADS)

    Sokolov, Vladimir; Balbaky, Abed; Sen, Amiya K.

    2015-11-01

    Transition from the slab to the toroidal branch of the electron temperature gradient (ETG) mode has been successfully achieved in a basic experiment in Columbia Linear Machine CLM. We found a modest increase in saturated ETG potential fluctuations (~ 2 ×) and a substantial increase in the power density of individual mode peaks (~ 4 - 5 ×) with increased levels of curvature. We have obtained a set of experimental scalings for electron thermal conductivity χ⊥e as a function of the inverse radius of curvature Rc-1 for different fluctuation levels of the initial slab ETG mode. We found that thermal conductivity for pure slab modes is larger than it is for mixed slab-toroidal ETG modes with the same level of mode fluctuation. This effective reduction in diffusive transport can be partly explained by the flute nature of the toroidal ETG mode. This research was supported by the Department of Electrical Engineering of Columbia University.

  3. Standing sausage modes in curved coronal slabs

    NASA Astrophysics Data System (ADS)

    Pascoe, D. J.; Nakariakov, V. M.

    2016-09-01

    Context. Magnetohydrodynamic waveguides such as dense coronal loops can support standing modes. The ratios of the periods of oscillations for different longitudinal harmonics depend on the dispersive nature of the waveguide and so may be used as a seismological tool to determine coronal parameters. Aims: We extend models of standing sausage modes in low β coronal loops to include the effects of loop curvature. The behaviour of standing sausage modes in this geometry is used to explain the properties of observed oscillations that cannot be accounted for using straight loop models. Methods: We perform 2D numerical simulations of an oscillating coronal loop, modelled as a dense slab embedded in a potential magnetic field. The loop is field-aligned and so experiences expansion with height in addition to being curved. Standing sausage modes are excited by compressive perturbations of the loop and their properties are studied. Results: The spatial profiles of standing sausage modes are found to be modified by the expanding loop geometry typical for flaring loops and modelled by a potential magnetic field in our simulations. Longitudinal harmonics of order n > 1 have anti-nodes that are shifted towards the loop apex and the amplitude of anti-nodes near the loop apex is smaller than those near the loop footpoints. Conclusions: We find that the observation of standing sausage modes by the Nobeyama Radioheliograph in a flaring coronal loop on 12 January 2000 is consistent with interpretation in terms of the global mode (n = 1) and third harmonic (n = 3). This interpretation accounts for the period ratio and spatial structure of the observed oscillations.

  4. Influence of overriding plate velocity changes on slab dip and deformation: insights from laboratory models

    NASA Astrophysics Data System (ADS)

    Guillaume, Benjamin; Hertgen, Solenn; Martinod, Joseph

    2016-04-01

    Over geological times, plate reorganization associated with mantle convection led to changes in absolute plate velocities, which may in turn have impacted the geometry of the subducting plate as well as the overriding plate regime of deformation. Indeed, previous studies have shown a very good correlation between the absolute motion of the overriding plate on one hand and slab dip and overriding plate deformation on the other hand: extension and steep slab are associated with an overriding plate moving away from the trench while shortening and shallow slab occur if the upper plate goes the other way. However, these correlations are established when subduction has reached a steady-state regime and for a constant motion of the overriding plate over the subducting plate, which may not always be the case on Earth. The response of the subduction system to changes in absolute overriding plate velocity still remain an open question. In this study, we conducted a set of 3-D mantle-scale laboratory models of subduction in which we incrementally changed the velocity of the overriding plate to reproduce changes of velocities that may arise from variations of far-field boundary conditions in Nature. We first show that strain rates in the overriding plate are correlated with overriding plate absolute velocity but also that the regime of deformation adjusts rapidly to changes of velocity. This may explain for instance why despite the subduction has been continuous beneath South America since at least the middle Jurassic, shortening along its active margin is only recorded episodically, the main phases of Andean orogeny roughly corresponding to periods of South American plate westward acceleration. We also show that slab dip adjusts to changes of overriding plate velocity but it requires several Myr before it stabilizes. It may explain why the correlation between absolute overriding plate motion and slab dip from the analysis of present-day subduction zones is only moderate, part

  5. Investigation of dislocation behavior in micron and sub-micron thin films

    NASA Astrophysics Data System (ADS)

    Hunter, Abigail

    Plastic deformation in crystalline materials is mediated by dislocation motion and their interaction with defects, such as second phase particles, dislocations, grain boundaries and voids. In addition, grain boundaries, free and passivated surfaces have a significant impact on the evolution of dislocations and their intricate structures. In polycrystalline materials, the influence of dislocation motion and interactions results in unique mechanical properties, such as high yield stress and fracture strength and a dependency on grain size. It is observed that for an average grain size in the micron and sub-micron regime, the yield stress increases as the grain size decreases following a power law. This size effect is known as Hall Petch effect. A reliable computational model that describes the mechanical response and failure mechanisms of micron and sub-micron scale devices should incorporate these size effects. A three-dimensional phase field dislocation dynamics model (3D PFDD) is developed. This is a dislocation based plasticity model that accounts for the motion and interactions of individual dislocations with material defects and interfaces, such as obstacles, and grain boundaries. This model is a valuable and efficient research tool that will help to understand plastic deformation on the mesoscopic level, bridging the gap between microscopic and macroscopic studies. For the research presented here, this model is used specifically to understand and simulate dislocation behavior in fcc (face-centered cubic) metal thin films, similar to those used in micro-electro-mechanical systems (MEMS). Incorporating microstructure, such as grain boundaries, is key to accurately predicting deformation behavior in any system. Plastic deformation is affected by both the thickness of the film layers and by the resolution of the film's internal microstructure. In MEMS devices and components that are generally on the micron scale (hundreds of microns in size), the internal

  6. Three-micron spectroscopy of highly reddened field stars

    NASA Technical Reports Server (NTRS)

    Tapia, Mauricio; Persi, P.; Roth, M.; Ferrari-Toniolo, M.

    1989-01-01

    Broad absorption features centered at 3.45 microns and at 3.0-3.0 microns towards a number of late-type supergiants in the vicinity of the galactic center were repeatedly reported. Here, 2.0 to 2.5 and 3.0 to 4.0 micron spectra are presented for field late-type highly reddened (A sub V is approximately 17-27) stars located in different regions of the galactic plane more than 20 deg away from the galactic center direction. The observations, made with the 3.6, 2.2, and 1.0 m ESO telescopes at La Silla, Chile, consists of CVF spectra with resolution lambda/delta lambda is approximately or equal to 100 and IRSPEC spectra with resolution lambda/delta lambda is approximately or equal to 700. In the direction of the most highly reddened stars, definitive detections of the 3.45 and the 3.0 to 3.1 micron absorption features are reported. The 3.45 micron feature was attributed to absorption arising in a vibrational transition resulting from the C-H stretching in organic compounds, while the 3.0 to 3.1 micron broader feature are tentatively attributed to O-H bonds. The observations strongly support that the agent producing the 3.45 micron feature, presumably organic molecules, is an important component of the diffuse interstellar medium and is not characteristic only of the galactic center environment.

  7. Cloud properties inferred from 8-12 micron data

    NASA Technical Reports Server (NTRS)

    Strabala, Kathleen I.; Ackerman, Steven A.; Menzel, W. Paul

    1994-01-01

    A trispectral combination of observations at 8-, 11-, and 12-micron bands is suggested for detecting cloud and cloud properties in the infrared. Atmospheric ice and water vapor absorption peak in opposite halves of the window region so that positive 8-minus-11-micron brightness temperature differences indicate cloud, while near-zero or negative differences indicate clear regions. The absorption coefficient for water increases more between 11 and 12 microns than between 8 and 11 microns, while for ice, the reverse is true. Cloud phases is determined by a scatter diagram of 8-minus-11-micron versus 11-minus-12-micron brightness temperature differences; ice cloud shows a slope greater than 1 and water cloud less than 1. The trispectral brightness temperature method was tested upon high-resolution interferometer data resulting in clear-cloud and cloud-phase delineation. Simulations using differing 8-micron bandwidths revealed no significant degradation of cloud property detection. Thus, the 8-micron bandwidth for future satellites can be selected based on the requirements of other applications, such as surface characterization studies. Application of the technique to current polar-orbiting High-Resolution Infrared Sounder (HIRS)-Advanced Very High Resolution Radiometer (AVHRR) datasets is constrained by the nonuniformity of the cloud scenes sensed within the large HIRS field of view. Analysis of MAS (MODIS Airborne Simulator) high-spatial resolution (500 m) data with all three 8-, 11-, and 12-micron bands revealed sharp delineation of differing cloud and background scenes, from which a simple automated threshold technique was developed. Cloud phase, clear-sky, and qualitative differences in cloud emissivity and cloud height were identified on a case study segment from 24 November 1991, consistent with the scene. More rigorous techniques would allow further cloud parameter clarification. The opportunities for global cloud delineation with the Moderate-Resolution Imaging

  8. Modeling the thin-slab continuous-casting mold

    SciTech Connect

    O'Connor, T.G. . Applied Superconductivity Group); Dantzig, J.A. . Dept. of Mechanical and Industrial Engineering)

    1994-06-01

    A three-dimensional mathematical model has been developed to compute the thermomechanical state in the mold of thin-slab continuous casters. The thin-slab mold differs from those used in conventional slab casters in that the upper portion of the broad side walls defines a funnel-shaped chamber which allows the nozzle to be submerged into the liquid metal. The chamber converges with distance down the mold, reducing to the rectangular cross section of the finished casting near the mold exit. The new mold, along with casting speeds up to 6 m/min, allows slabs to be cast 50--60 mm thick, compared with 150 to 350 mm in conventional continuous slab casting. However, the mold shape and high casting speed lead to higher mold temperatures and shorter mold life than are found in conventional slab casters. In this article, the author develop mathematical models of the process to determine the role of various process parameters in determining the mold life. Finite-element analysis is used to determine the temperatures in the mold and cast slab, and these data are then used in an elastic-viscoplastic analysis to investigate the deformation of the mold wall in service. Cyclic inelastic strains up to 1.75 pct are found in a region below the meniscus along the funnel edge. These large strains result from the combination of locally high temperatures coupled with geometric restraint of the mold. The deformation leads to short mold life because of thermal fatigue cracking of the mold. The computed locations and time to failure of the mold in fatigue agree very well with observations of the appearance of mold surface cracks in an operating caster. The models are also used to develop an improved mold design.

  9. Modeling the thin-slab continuous-casting mold

    NASA Astrophysics Data System (ADS)

    Oconnor, Thomas G.; Dantzig, Jonathan A.

    1994-06-01

    A three-dimensional mathematical model has been developed to compute the thermomechanical state in the mold of thin-slab continuous casters. The thin-slab mold differs from those used in conventional slab casters in that the upper portion of the broad side walls defines a funnel-shaped chamber which allows the nozzle to be submerged into the liquid metal. The chamber converges with distance down the mold, reducing to the rectangular cross section of the finished casting near the mold exit. The new mold, along with casting speeds up to 6 m/min, allows slabs to be cast 50 60 mm thick, compared with 150 to 350 mm in conventional continuous slab casting. However, the mold shape and high casting speed lead to higher mold temperatures and shorter mold life than are found in conventional slab casters. In this article, we develop mathematical models of the process to determine the role of various process parameters in determining the mold life. Finite-element analysis is used to determine the temperatures in the mold and cast slab, and these data are then used in an elastic-viscoplastic analysis to investigate the deformation of the mold wall in service. Cyclic inelastic strains up to 1.75 Pct are found in a region below the meniscus along the funnel edge. These large strains result from the combination of locally high temperatures coupled with geometric restraint of the mold. The deformation leads to short mold life because of thermal fatigue cracking of the mold. The computed locations and time to failure of the mold in fatigue agree very well with observations of the appearance of mold surface cracks in an operating caster. The models are also used to develop an improved mold design.

  10. Can slabs melt beneath forearcs in hot subduction zones?

    NASA Astrophysics Data System (ADS)

    Ribeiro, J.; Maury, R.; Gregoire, M.

    2015-12-01

    At subduction zones, thermal modeling predict that the shallow part of the downgoing oceanic crust (< 80 - 100 km depth to the slab) is usually too cold to cross the water-rich solidus and melts beneath the forearc. Yet, the occasional occurrence of adakites, commonly considered as slab melts, in the forearc region challenges our understanding of the shallow subduction processes. Adakites are unusual felsic rocks commonly associated with asthenospheric slab window opening or fast subduction of young (< 25 Ma) oceanic plate that enable slab melting at shallow depths; but their genesis has remained controversial. Here, we present a new approach that provides new constraints on adakite petrogenesis in hot subduction zones (the Philippines) and above an asthenospheric window (Baja California, Mexico). We use amphibole compositions to estimate the magma storage depths and the composition of the parental melts to test the hypothesis that adakites are pristine slab melts. We find that adakites from Baja California and Philippines formed by two distinct petrogenetic scenarios. In Baja California, hydrous mantle melts mixed/mingled with high-pressure (HP) adakite-type, slab melts within a lower crustal (~30 km depth) magma storage region before stalling into the upper arc crust (~7-15 km depth). In contrast, in the Philippines, primitive mantle melts stalled and crystallized within lower and upper crustal magma storage regions to produce silica-rich melts with an adakitic signature. Thereby, slab melting is not required to produce an adakitic geochemical fingerprint in hot subduction zones. However, our results also suggest that the downgoing crust potentially melted beneath Baja California.

  11. Mantle flow and dynamic topography associated with slab window opening

    NASA Astrophysics Data System (ADS)

    Guillaume, Benjamin; Moroni, Monica; Funiciello, Francesca; Martinod, Joseph; Faccenna, Claudio

    2010-05-01

    A slab window is defined as an 'hole' in the subducting lithosphere. In the classical view, slab windows develop where a spreading ridge intersects a subduction zone. The main consequences of this phenomenon are the modifications of the physical, chemical and thermal conditions in the backarc mantle that in turn affect the tectonic and magmatic evolution of the overriding plate. In this work, we perform dynamically self-consistent mantle-scale laboratory models, to evaluate how the opening of a window in the subducting panel influences the geometry and the kinematics of the slab, the mantle circulation pattern and, finally, the overriding plate dynamic topography. The adopted setup consists in a two-layer linearly viscous system simulating the roll-back of a fixed subducting plate (simulated using silicone putty) into the upper mantle (simulated using glucose syrup). Our experimental setting is also characterized by a constant-width rectangular window located at the center of a laterally confined slab, modeling the case of the interaction of a trench-parallel spreading ridge with a wide subduction zone. We find that the geometry and the kinematics of the slab are only minorly affected by the opening of a slab window. On the contrary, slab induced mantle circulation, quantified using Feature Tracking image analysis technique, is strongly modified and produces a peculiar non-isostatic topographic signal on the overriding plate. Assuming that our modeling results can be representative of the natural behavior of subduction zones, we compare them to the Patagonian subduction zone finding that anomalous backarc volcanism that developed since middle Miocene could result from the lateral flowage of subslab mantle, and that part of the Patagonian uplift could be dynamically supported.

  12. Modeling the surface photovoltage of silicon slabs with varying thickness.

    PubMed

    Vazhappilly, Tijo; Kilin, Dmitri S; Micha, David A

    2015-04-10

    The variation with thickness of the energy band gap and photovoltage at the surface of a thin semiconductor film are of great interest in connection with their surface electronic structure and optical properties. In this work, the change of a surface photovoltage (SPV) with the number of layers of a crystalline silicon slab is extracted from models based on their atomic structure. Electronic properties of photoexcited slabs are investigated using generalized gradient and hybrid density functionals, and plane wave basis sets. Si(1 1 1) surfaces have been terminated by hydrogen atoms to compensate for dangling bonds and have been described by large supercells with periodic boundary conditions. Calculations of the SPV of the Si slabs have been done in terms of the reduced density matrix of the photoactive electrons including dissipative effects due to their interaction with medium phonons and excitons. Surface photovoltages have been calculated for model Si slabs with 4-12, and 16 layers, to determine convergence trends versus slab thickness. Band gaps and the inverse of the SPVs have been found to scale nearly linearly with the inverse thickness of the slab, while the electronic density of states increases quadratically with thickness. Our calculations show the same trends as experimental values indicating band gap reduction and absorption enhancement for Si films of increasing thickness. Simple arguments on confined electronic structures have been used to explain the main effects of changes with slab thickness. A procedure involving shifted electron excitation energies is described to improve results from generalized gradient functionals so they can be in better agreement with the more accurate but also more computer intensive values from screened exchange hybrid functionals.

  13. Continental collision and slab break-off: A comparison of 3-D numerical models with observations

    NASA Astrophysics Data System (ADS)

    van Hunen, Jeroen; Allen, Mark B.

    2011-02-01

    Conditions and dynamics of subduction-collision and subsequent 3-D slab break-off and slab tear propagation are quantified, for the first time, using fully dynamic numerical models. Model results indicate that collision after the subduction of old, strong subducting oceanic slab leads to slab break-off at 20-25 Myr after the onset of continental collision, and subsequently a slab tear migrates more or less horizontally through the slab with a propagation speed of 100-150 mm/yr. In contrast, young, weak oceanic slabs show the first break-off already 10 Myr after continental collision, and can experience tear migration rates up to 800 mm/yr. Slab strength plays a more important role in the timing of slab break-off and the speed of a propagating slab tear than (negative) slab buoyancy does. Slab break-off is viable even for slabs that are supported by the viscosity jump and phase change between the upper and lower mantle. The density of the oceanic slab and the subducting continental block is important for the amount of continental subduction and the depth of slab break-off. A 40-km thick continental crust can be buried to depths greater than 200 km, although this maximum depth is significantly less for younger or very weak slabs, or thicker continental crust. Slab break-off typically starts at a depth of 300 km, mostly independent of mantle rheology, but, like continental crustal burial, can be shallower for young or buoyant plates. Our 3-D models illustrate how, due to the difference in necking in 2-D and 3-D, break-off has an intrinsic small preference to start as a slab window within the slab's interior, rather than as a slab tear at the slab edge. However, any significant asymmetry in the collision setting, e.g. earlier collision at one end of the subduction zone, would override this, and leads to slab tearing starting near one edge of the slab. These results put important new constraints on the dynamics of the collision and subsequent slab break-off for modern

  14. Effects of Crustal Densification in Warm Slabs on In-slab Earthquakes and Episodic Tremors and Slips

    NASA Astrophysics Data System (ADS)

    Wang, K.

    2003-12-01

    During subduction, dehydration may facilitate earthquake rupture in both the slab crust and slab mantle. The up to 15% rock densification that accompanies the metabasalt-eclogite transformation is expected to have several mechanical consequences. In warm slabs such as Cascadia and Nankai, this transformation and mantle serpentine breakdown begin at rather shallow depths (30 - 50 km). The pervasively hydrated upper crust transforms to eclogite under equilibrium conditions, but the transformation of the anhydrous parts of the lower crust is kinetically delayed to greater depths. Therefore, densification begins in a thin layer along the top of the slab. Volume reduction gives rise to an equivalent stretching force in the thin layer in all slab-parallel directions, activating existing faults and developing new fractures. Analogous to a weak layer sandwiched between, and bonded to, two strong layers under stretching, fracture spacing in the weak layer scales with the layer thickness. The theory predicts that the densified thin layer must be ~{!0~}shattered~{!1~}. The shattered upper crust may have numerous small earthquakes but does not favor large ruptures. In contrast, the much more uniform lower crust and mantle can host larger ruptures, although seismic ruptures occur only in the limited hydrated parts. This explains the observation that relatively few earthquakes deeper inside the slab tend to have larger magnitudes than those just below the slab surface. For example, three recent damaging events (1999 Oaxaca, Mexico; 2001 Geiyo, Nankai; 2001 Nisqually, Cascadia) in warm slabs all occurred in the lower crust or mantle. The densification is generally a steady state process: An increasingly thinner slab moves into an increasingly thinner subduction "slot" continuously, with the downdip width of transition from normal to thinned crust scaling linearly with the subduction rate. However, at the fracture scale, the process is highly nonlinear, and there must be small

  15. Tomographic imaging of the effects of Peruvian flat slab subduction on the Nazca slab and surrounding mantle under central and southern Peru

    NASA Astrophysics Data System (ADS)

    Scire, A. C.; Zandt, G.; Beck, S. L.; Bishop, B.; Biryol, C. B.; Wagner, L. S.; Long, M. D.; Minaya, E.; Tavera, H.

    2014-12-01

    The modern central Peruvian Andes are dominated by a laterally extensive region of flat slab subduction. The Peruvian flat slab extends for ~1500 km along the strike of the Andes, correlating with the subduction of the Nazca Ridge in the south and the theorized Inca Plateau in the north. We have used data from the CAUGHT and PULSE experiments for finite frequency teleseismic P- and S-wave tomography to image the Nazca slab in the upper mantle below 95 km depth under central Peru between 10°S and 18°S as well as the surrounding mantle. Since the slab inboard of the subducting Nazca Ridge is mostly aseismic, our results provide important constraints on the geometry of the subducting Nazca slab in this region. Our images of the Nazca slab suggest that steepening of the slab inboard of the subducting Nazca Ridge locally occurs ~100 km further inland than was indicated in previous studies. The region where we have imaged the steepening of the Nazca slab inboard of the Nazca Ridge correlates with the location of the Fitzcarrald Arch, a long wavelength upper plate topographic feature which has been suggested to be a consequence of ridge subduction. When the slab steepens inboard of the flat slab region, it does so at a very steep (~70°) angle. The transition from the Peruvian flat slab to the more normally dipping slab south of 16°S below Bolivia is characterized by an abrupt bending of the slab anomaly in the mantle in response to the shift from flat to normal subduction. The slab anomaly appears to be intact south of the Nazca Ridge with no evidence for tearing of the slab in response to the abrupt change in slab dip. A potential tear in the slab is inferred from an observed offset in the slab anomaly north of the Nazca Ridge extending subparallel to the ridge axis between 130 and 300 km depth. A high amplitude (-5-6%) slow S-wave velocity anomaly is observed below the projection of the Nazca Ridge. This anomaly appears to be laterally confined to the mantle

  16. Apparatus for handling micron size range particulate material

    NASA Technical Reports Server (NTRS)

    Friichtenicht, J. F.; Roy, N. L. (Inventor)

    1968-01-01

    An apparatus for handling, transporting, or size classifying comminuted material was described in detail. Electrostatic acceleration techniques for classifying particles as to size in the particle range from 0.1 to about 100 microns diameter were employed.

  17. Release of Micronized Copper Particles from Pressure Treated Wood Products.

    EPA Science Inventory

    Micronized copper pressure treated lumber (PTL) has recently been introduced to the consumer market as a replacement for ionized copper PTL. The presence of particulate rather than aqueous copper raises concerns about possible human or environmental exposure. Two common pathways ...

  18. Injection Seeded/Phase-Conjugated 2-micron Laser System

    NASA Technical Reports Server (NTRS)

    Bai, Yingxin; Yu, Jirong; Petros,M.; Petzar, Paul; Trieu, Bo; Lee, Hyung; Singh, U.; Leyva, V.; Shkunov, V.; Rockwell, D.; Betin, A.; Wang, J.

    2007-01-01

    For the first time, beam quality improvement of 2 micron laser using a fiber based phase conjugation mirror has been demonstrated. Single frequency operation is necessary to lower threshold. The reflectivity of PCM is approx. 50%.

  19. Airborne spectrophotometry of Comet Halley from 5 to 9 microns

    NASA Technical Reports Server (NTRS)

    Campins, H.; Bregman, J. D.; Witteborn, F. C.; Wooden, D. H.; Rank, D. M.; Cohen, M.; Allamandola, Louis J.; Tielens, Alexander G. G. M.

    1986-01-01

    Spectrophotometry from 5 to 9 microns (resolution = 0.02) of comet Halley was obtained from the Kuiper Airborne Observatory on 1985 Dec. 12.1 and 1986 April 8.6 and 10.5 UT. Two spectral features are apparent in all the observations, one from 5.24 to 5.6 microns, and the silicate emission feature which has an onset between 7 and 8 microns. There is no evidence for the 7.5 microns feature observed by the Vega 1 spacecraft; the large difference between the areal coverage viewed from the spacecraft and the airplane may explain the discrepancy. Color temperatures significantly higher than a blackbody indicate that small particles are abundant in the coma. Significant spatial and temporal variations in the spectrum show trends similar to those observed from the ground.

  20. Laser materials for the 0.67-microns to 2.5-microns range

    NASA Technical Reports Server (NTRS)

    Toda, Minoru; Zamerowski, Thomas J.; Ladany, Ivan; Martinelli, Ramon U.

    1987-01-01

    Basic requirements for obtaining injection laser action in III-V semiconductors are discussed briefly. A detailed review is presented of materials suitable for lasers emitting at 0.67, 1.44, 1.93, and 2.5 microns. A general approach to the problem is presented, based on curves of materials properties published by Sasaki et al. It is also shown that these curves, although useful, may need correction in certain ranges. It is deduced that certain materials combinations, either proposed in the literature or actually tried, are not appropriate for double heterostructure lasers, because the refractive index of the cladding material is higher than the index of the active material, thus resulting in no waveguiding, and high threshold currents. Recommendations are made about the most promising approach to the achievement of laser action in the four wavelengths mentioned above.

  1. Fossil slabs attached to unsubducted fragments of the Farallon plate

    PubMed Central

    Wang, Yun; Forsyth, Donald W.; Rau, Christina J.; Carriero, Nina; Schmandt, Brandon; Gaherty, James B.; Savage, Brian

    2013-01-01

    As the Pacific–Farallon spreading center approached North America, the Farallon plate fragmented into a number of small plates. Some of the microplate fragments ceased subducting before the spreading center reached the trench. Most tectonic models have assumed that the subducting oceanic slab detached from these microplates close to the trench, but recent seismic tomography studies have revealed a high-velocity anomaly beneath Baja California that appears to be a fossil slab still attached to the Guadalupe and Magdalena microplates. Here, using surface wave tomography, we establish the lateral extent of this fossil slab and show that it is correlated with the distribution of high-Mg andesites thought to derive from partial melting of the subducted oceanic crust. We also reinterpret the high seismic velocity anomaly beneath the southern central valley of California as another fossil slab extending to a depth of 200 km or more that is attached to the former Monterey microplate. The existence of these fossil slabs may force a reexamination of models of the tectonic evolution of western North America over the last 30 My. PMID:23509274

  2. Fossil slabs attached to unsubducted fragments of the Farallon plate.

    PubMed

    Wang, Yun; Forsyth, Donald W; Rau, Christina J; Carriero, Nina; Schmandt, Brandon; Gaherty, James B; Savage, Brian

    2013-04-01

    As the Pacific-Farallon spreading center approached North America, the Farallon plate fragmented into a number of small plates. Some of the microplate fragments ceased subducting before the spreading center reached the trench. Most tectonic models have assumed that the subducting oceanic slab detached from these microplates close to the trench, but recent seismic tomography studies have revealed a high-velocity anomaly beneath Baja California that appears to be a fossil slab still attached to the Guadalupe and Magdalena microplates. Here, using surface wave tomography, we establish the lateral extent of this fossil slab and show that it is correlated with the distribution of high-Mg andesites thought to derive from partial melting of the subducted oceanic crust. We also reinterpret the high seismic velocity anomaly beneath the southern central valley of California as another fossil slab extending to a depth of 200 km or more that is attached to the former Monterey microplate. The existence of these fossil slabs may force a reexamination of models of the tectonic evolution of western North America over the last 30 My.

  3. Systematic variation in the depths of slabs beneath arc volcanoes

    USGS Publications Warehouse

    England, P.; Engdahl, R.; Thatcher, W.

    2004-01-01

    The depths to the tops of the zones of intermediate-depth seismicity beneath arc volcanoes are determined using the hypocentral locations of Engdahl et al. These depths are constant, to within a few kilometres, within individual arc segments, but differ by tens of kilometres from one arc segment to another. The range in depths is from 65 km to 130 km, inconsistent with the common belief that the volcanoes directly overlie the places where the slabs reach a critical depth that is roughly constant for all arcs. The depth to the top of the intermediate-depth seismicity beneath volcanoes correlates neither with age of the descending ocean floor nor with the thermal parameter of the slab. This depth does, however, exhibit an inverse correlation with the descent speed of the subducting plate, which is the controlling factor both for the thermal structure of the wedge of mantle above the slab and for the temperature at the top of the slab. We interpret this result as indicating that the location of arc volcanoes is controlled by a process that depends critically upon the temperature at the top of the slab, or in the wedge of mantle, immediately below the volcanic arc.

  4. Fossil slabs attached to unsubducted fragments of the Farallon plate.

    PubMed

    Wang, Yun; Forsyth, Donald W; Rau, Christina J; Carriero, Nina; Schmandt, Brandon; Gaherty, James B; Savage, Brian

    2013-04-01

    As the Pacific-Farallon spreading center approached North America, the Farallon plate fragmented into a number of small plates. Some of the microplate fragments ceased subducting before the spreading center reached the trench. Most tectonic models have assumed that the subducting oceanic slab detached from these microplates close to the trench, but recent seismic tomography studies have revealed a high-velocity anomaly beneath Baja California that appears to be a fossil slab still attached to the Guadalupe and Magdalena microplates. Here, using surface wave tomography, we establish the lateral extent of this fossil slab and show that it is correlated with the distribution of high-Mg andesites thought to derive from partial melting of the subducted oceanic crust. We also reinterpret the high seismic velocity anomaly beneath the southern central valley of California as another fossil slab extending to a depth of 200 km or more that is attached to the former Monterey microplate. The existence of these fossil slabs may force a reexamination of models of the tectonic evolution of western North America over the last 30 My. PMID:23509274

  5. Optical distortions in end-pumped zigzag slab lasers.

    PubMed

    Tang, Bing; Zhou, Tangjian; Wang, Dan; Li, Mi

    2015-04-01

    Ray tracing is performed to investigate the optical distortions in the end-pumped, zigzag slab. Optical path differences caused by temperature, slab deformation, and stress birefringence are calculated under uniform pumping; the results show a steep edge in the width dimension and a thermal lens with an effective focal length as short as several meters in the thickness dimension. Dependence of depolarization on total internal reflection phase retardance as well as the slab's cut angle is studied by the Jones matrix technique; results show that although at the pumping power of 10 kW, the mean depolarization of the 2.5  mm×30  mm×150.2  mm Nd:YAG slab is generally below 3%, and it increases rapidly with pumping power. Besides, for the 0°- or 60°-cut slab, an optimal phase retardance range of 5° to 13° exists, in which the depolarization loss can be lower than 0.5%. Finally, experiments on temperature and depolarization measurements verify the numerical results. PMID:25967178

  6. Cenozoic Plume-Slab Interaction Beneath the Pacific Northwest

    NASA Astrophysics Data System (ADS)

    Obrebski, M. J.; Allen, R. M.; Hung, S.; Pollitz, F. F.

    2009-12-01

    Here we present new images of the structure beneath the Pacific Northwest obtained by inverting both compressional and shear teleseismic body waves and using finite-frequency sensitivity kernels. The models use all available seismic data from the Earthscope Transportable Array, regional seismic networks and two Flexible Array experiments (Mendocino and FACES experiments) deployed on the west coast. By picking P, S and SKS arrivals manually and estimating station-to-station relative arrival times through cross correlation of the waveforms, we select only the highest quality data. East from the Juan de Fuca slab and north from the Mendocino Triple Junction, the mantle structure is dominated by high velocity blocks that are likely to be fragments of the Farallon slab. In the middle of the slab fragments, both our compressional (DNA09-P) and shear (DNA09-S) velocity models show a continuous low velocity anomaly that extends from the Yellowstone Caldera down into the lower mantle. We interpret this feature as a deep-seated mantle plume. The striking contrast between the slab-dominated mantle north from the MTJ and the continuous deep-seated Yellowstone mantle plume suggests the plume disrupted the Farallon slab during its ascent to the surface.

  7. The size of NGC 1068 at 10 microns

    NASA Technical Reports Server (NTRS)

    Becklin, E. E.; Neugebauer, G.; Matthews, K.; Wynn-Williams, C. G.

    1973-01-01

    The data presented show that a majority of the 10-micron emission from NGC 1068 comes from an area with a diameter of about 60 pc. The measurements described were made at 10 microns on two nights at the 200-inch Hale telescope. The data obtained agree with the results obtained by Stein et al. (1973). An approach to reconcile the new data with the variability observed by Rieke and Low (1972) is also discussed.

  8. High-resolution maps of Jupiter at five microns.

    NASA Technical Reports Server (NTRS)

    Keay, C. S. L.; Low, F. J.; Rieke, G. H.; Minton, R. B.

    1973-01-01

    The distribution of 5-micron radiation, emitted from a large number of discrete sources from Jupiter, was observed during the 1972 apparition. These sources are less bright than those observed by Westphal (1969). At least 50 discrete sources having brightness temperatures exceeding 227 K were revealed which were mainly located within three narrow-latitude bands. Strong correlation exists between the 5-micron brightness temperatures of Jovian features and their colors as recorded photographically.

  9. Micron Accuracy Deployment Experiment (MADE), phase A. Volume 1

    NASA Technical Reports Server (NTRS)

    Peterson, Lee D.; Lake, Mark S.

    1995-01-01

    This report documents a Phase A In-STEP flight experiment development effort. The objective of the experiment is to deploy a portion of a segmented reflector on the Shuttle and study its micron-level mechanics. Ground test data are presented which projects that the on-orbit precision of the test article should be approximately 5 microns. Extensive hardware configuration development information is also provided.

  10. Micronized Organic Magnesium Salts Enhance Opioid Analgesia in Rats

    PubMed Central

    Bujalska-Zadrożny, Magdalena; Kulik, Kamila; Ordak, Michał; Sasinowska-Motyl, Małgorzata; Gąsińska, Emilia; de Corde, Anna; Kowalczyk, Agnieszka; Sacharczuk, Mariusz; Naruszewicz, Marek

    2016-01-01

    Purpose As previously reported, magnesium sulphate administered parenterally significantly increased an opioid antinociception in different kinds of pain. Since the typical form of magnesium salts are poorly and slowly absorbed from the gastrointestinal tract we examined whether their micronized form could increase opioids induced antinociception. Methods In behavioural studies on rats morphine, tramadol and oxycodone together with magnesium (lactate dihydrate, hydroaspartate, chloride) in micronized (particles of size D90 < 50 μm) and conventional forms were used. Changes in pain thresholds were determined using mechanical stimuli. The intestinal absorption of two forms of magnesium lactate dihydrate (at the doses of 7.5 or 15 mg ions) in the porcine gut sac model were also compared. Results Micronized form of magnesium lactate dihydrate or hydroaspartate but not chloride (15 mg of magnesium ions kg-1) enhanced the analgesic activity of orally administered opioids, significantly faster and more effective in comparison to the conventional form of magnesium salts (about 40% for oxycodone administered together with a micronized form of magnesium hydroaspartate). Moreover, in vitro studies of transport across porcine intestines of magnesium ions showed that magnesium salts administered in micronized form were absorbed from the intestines to a greater extent than the normal form of magnesium salts. Conclusions The co-administration of micronized magnesium organic salts with opioids increased their synergetic analgesic effect. This may suggest an innovative approach to the treatment of pain in clinical practice. PMID:27792736

  11. Effects of edge restraint on slab behavior. Final report

    SciTech Connect

    Guice, L.K.

    1986-02-01

    This study was performed in conjunction with a Federal Emergency Management Agency program to plan, design, and construct keyworker blast shelters which would be used in high-risk areas of the country during and after a nuclear attack. The shelters considered in this study were box-type structures in which damage is much more likely to occur in the roof slab than in the walls or floor. In this part of the program, the effect of edge restraint on slab behavior was investigated. The primary objective was to determine the effects of partial rotational restraint on slab strength, ductility, and mechanism of failure. Sixteen one-way, reinforced concrete plate elements were tested in a reaction structure under uniform static water pressure.

  12. Abrupt tectonics and rapid slab detachment with grain damage.

    PubMed

    Bercovici, David; Schubert, Gerald; Ricard, Yanick

    2015-02-01

    A simple model for necking and detachment of subducting slabs is developed to include the coupling between grain-sensitive rheology and grain-size evolution with damage. Necking is triggered by thickened buoyant crust entrained into a subduction zone, in which case grain damage accelerates necking and allows for relatively rapid slab detachment, i.e., within 1 My, depending on the size of the crustal plug. Thick continental crustal plugs can cause rapid necking while smaller plugs characteristic of ocean plateaux cause slower necking; oceanic lithosphere with normal or slightly thickened crust subducts without necking. The model potentially explains how large plateaux or continental crust drawn into subduction zones can cause slab loss and rapid changes in plate motion and/or induce abrupt continental rebound. PMID:25605890

  13. Role of Hydrogen in stagnant slabs and big mantle wedge

    NASA Astrophysics Data System (ADS)

    Ohtani, E.; Zhao, D.

    2008-12-01

    Recent seismic tomography data imply that subducting slabs are stagnant at some regions such as beneath Japan and Northeast China [1, 2]. The stagnant slab can have an important effect on the overlying transition zone and upper mantle. A big mantle wedge (BMW) model has been proposed by Zhao [2], in which the stagnant slab in the transition zone could play an essential role in the intra-plate volcanic activities overlying the slab. Water released by the stagnant slab could be important for such igneous activities, such as Mt. Changbai in Northeast China. In cold subducting slabs, several hydrous minerals together with nominally anhydrous minerals accommodate OH and transport water into the transition zone [3]. The effect of dehydration of the stagnant slab has been analyzed by Richard et al. [4]. They argued that warming of the stagnant slab due to heat conduction could play an important role for the slab dehydration, and local oversaturation could be achieved due to decrease of the water solubility in minerals with temperature, and fluid can be formed in the overlying transition zone. We determined the hydrogen diffusion in wadsleyite and ringwoodite under the transition zone conditions in order to clarify the deep processes of the stagnant slabs, and found that diffusion rates of hydrogen are comparable with that of olivine [5]. We also determined the dihedral angle of aqueous fluid between wadsleyite grains and majorite grains under the transition zone conditions. The dihedral angles are very small, around 20-40 degrees, indicating that the oversaturated fluids can move rapidly by the percolation mechanism in the transition zone. The fluids moved to the top of the 410 km discontinuity can generate heavy hydrous melts due to a larger depression of the wet solidus at the base of the upper mantle [6]. Gravitationally stable hydrous melts can be formed at the base of the upper mantle, which is consistent with seismological observations of the low velocity beneath

  14. Abrupt tectonics and rapid slab detachment with grain damage.

    PubMed

    Bercovici, David; Schubert, Gerald; Ricard, Yanick

    2015-02-01

    A simple model for necking and detachment of subducting slabs is developed to include the coupling between grain-sensitive rheology and grain-size evolution with damage. Necking is triggered by thickened buoyant crust entrained into a subduction zone, in which case grain damage accelerates necking and allows for relatively rapid slab detachment, i.e., within 1 My, depending on the size of the crustal plug. Thick continental crustal plugs can cause rapid necking while smaller plugs characteristic of ocean plateaux cause slower necking; oceanic lithosphere with normal or slightly thickened crust subducts without necking. The model potentially explains how large plateaux or continental crust drawn into subduction zones can cause slab loss and rapid changes in plate motion and/or induce abrupt continental rebound.

  15. Requalification analysis of a circular composite slab for seismic load

    SciTech Connect

    Srinivasan, M.G.; Kot, C.A.

    1992-11-01

    The circular roof slab of an existing facility was analyzed to requalify the structure for supporting a significant seismic load that it was not originally designed for. The slab has a clear span of 66 ft and consists of a 48 in thick reinforced concrete member and a steel liner plate. Besides a number of smaller penetrations, the slab contains two significant cutouts: a 9 ft square opening and a 3 ft dia hole. The issues that complicated the analysis of this non-typical structure, i.e., composite action and nonlinear stiffness of reinforced concrete (R. C.) sections, are discussed. It was possible to circumvent the difficulties by making conservative and simplifying assumptions. If codes incorporate guidelines on practical methods for dynamic analysis of R. C. structures, some of the unneeded conservatism could be eliminated in future designs.

  16. Dynamic triggering of deep earthquakes within a fossil slab

    NASA Astrophysics Data System (ADS)

    Cai, Chen; Wiens, Douglas A.

    2016-09-01

    The 9 November 2009 Mw 7.3 Fiji deep earthquake is the largest event in a region west of the Tonga slab defined by scattered seismicity and velocity anomalies. The main shock rupture was compact, but the aftershocks were distributed along a linear feature at distances of up to 126 km. The aftershocks and some background seismicity define a sharp northern boundary to the zone of outboard earthquakes, extending westward toward the Vitiaz deep earthquake cluster. The northern earthquake lineament is geometrically similar to tectonic reconstructions of the relict Vitiaz subduction zone at 8-10 Ma, suggesting the earthquakes are occurring in the final portion of the slab subducted at the now inactive Vitiaz trench. A Coulomb stress change calculation suggests many of the aftershocks were dynamically triggered. We propose that fossil slabs contain material that is too warm for earthquake nucleation but may be near the critical stress susceptible to dynamic triggering.

  17. Abrupt tectonics and rapid slab detachment with grain damage

    PubMed Central

    Bercovici, David; Schubert, Gerald; Ricard, Yanick

    2015-01-01

    A simple model for necking and detachment of subducting slabs is developed to include the coupling between grain-sensitive rheology and grain-size evolution with damage. Necking is triggered by thickened buoyant crust entrained into a subduction zone, in which case grain damage accelerates necking and allows for relatively rapid slab detachment, i.e., within 1 My, depending on the size of the crustal plug. Thick continental crustal plugs can cause rapid necking while smaller plugs characteristic of ocean plateaux cause slower necking; oceanic lithosphere with normal or slightly thickened crust subducts without necking. The model potentially explains how large plateaux or continental crust drawn into subduction zones can cause slab loss and rapid changes in plate motion and/or induce abrupt continental rebound. PMID:25605890

  18. Systematic effects induced by a flat isotropic dielectric slab.

    PubMed

    Macculi, Claudio; Zannoni, Mario; Peverini, Oscar Antonio; Carretti, Ettore; Tascone, Riccardo; Cortiglioni, Stefano

    2006-07-20

    The instrumental polarization induced by a flat isotropic dielectric slab in microwave frequencies is discussed. We find that, in spite of its isotropic nature, such a dielectric can produce spurious polarization either by transmitting incoming anisotropic diffuse radiation or emitting when it is thermally inhomogeneous. We present evaluations of instrumental polarization generated by materials usually adopted in radio astronomy, by using the Mueller matrix formalism. As an application, results for different slabs in front of a 32 GHz receiver are discussed. Such results are based on measurements of their complex dielectric constants. We evaluate that a 0.33 cm thick Teflon slab introduces negligible spurious polarization (<2.6 x 10(-5) in transmission and <6 x 10(-7) in emission), even minimizing the leakage (<10(-8) from Q to U Stokes parameters, and vice versa) and the depolarization (approximately 1.3 x 10(-3)).

  19. Slab detachment of subducted Indo-Australian plate beneath Sunda arc, Indonesia

    NASA Astrophysics Data System (ADS)

    Kundu, Bhaskar; Gahalaut, V. K.

    2011-04-01

    Necking, tearing, slab detachment and subsequently slab loss complicate the subduction zone processes and slab architecture. Based on evidences which include patterns of seismicity, seismic tomography and geochemistry of arc volcanoes, we have identified a horizontal slab tear in the subducted Indo-Australian slab beneath the Sunda arc. It strongly reflects on trench migration, and causes along-strike variations in vertical motion and geochemically distinct subduction-related arc magmatism. We also propose a model for the geodynamic evolution of slab detachment.

  20. Waveform modeling the deep slab beneath northernmost Nevada

    NASA Astrophysics Data System (ADS)

    Helmberger, D. V.; Sun, D.

    2011-12-01

    The interactions between subducted slab and transition zone are crucial issues in dynamic modeling. Previous mantle convection studies have shown that various viscosity structures can result in various slab shape, width, and edge sharpness. Recent tomographic images based on USArray data reveals strong multi-scale heterogeneous upper mantle beneath western US. Among those features, a slab-like fast anomaly extends from 300 to 600 km depth below Nevada and western Utah, which was suggested as a segmented chunk of the Farallon slab. But we still missing key information about the details of this structure and whether this structure flatten outs in the transition zone, where various tomographic models display inconsistent images. The study of multipathing and waveform broadening around sharp features have been proved a efficient way to study such features. Here, we use both P and S waveform data from High Lava Plains seismic experiments and USArray to produce a detailed image. If we amplify the Schmandt and Humphreys [2010] 's S-wave tomography model by 1.5, we can produce excellent travel-time fits. But the waveform distortions are not as strong as those observed in data for events coming from the southeast, which suggest a much sharper anomaly. The waveform broadening features are not observed for events arriving from northwestern. By fitting the SH waveform data, we suggest that this slab-like structure dips ~35° to the southeast, extending to a depth near 660 km with a velocity increase of about 5 per cent. To generate corresponding P model, we adapt the SH wave model and scale the model using a suite of R (=dlnVs/dlnVp) values. We find that synthetics from the model with R ≈ 2 can fit the observed data, which confirms the segmented slab interpretation of this high velocity anomaly.

  1. Prescribed 3-D Direct Writing of Suspended Micron/Sub-micron Scale Fiber Structures via a Robotic Dispensing System

    PubMed Central

    Yuan, Hanwen; Cambron, Scott D.; Keynton, Robert S.

    2015-01-01

    A 3-axis dispensing system is utilized to control the initiating and terminating fiber positions and trajectory via the dispensing software. The polymer fiber length and orientation is defined by the spatial positioning of the dispensing system 3-axis stages. The fiber diameter is defined by the prescribed dispense time of the dispensing system valve, the feed rate (the speed at which the stage traverses from an initiating to a terminating position), the gauge diameter of the dispensing tip, the viscosity and surface tension of the polymer solution, and the programmed drawing length. The stage feed rate affects the polymer solution’s evaporation rate and capillary breakup of the filaments. The dispensing system consists of a pneumatic valve controller, a droplet-dispensing valve and a dispensing tip. Characterization of the direct write process to determine the optimum combination of factors leads to repeatedly acquiring the desired range of fiber diameters. The advantage of this robotic dispensing system is the ease of obtaining a precise range of micron/sub-micron fibers onto a desired, programmed location via automated process control. Here, the discussed self-assembled micron/sub-micron scale 3D structures have been employed to fabricate suspended structures to create micron/sub-micron fluidic devices and bioengineered scaffolds. PMID:26132732

  2. Expansion of a cold non-neutral plasma slab

    SciTech Connect

    Karimov, A. R.; Yu, M. Y.; Stenflo, L.

    2014-12-15

    Expansion of the ion and electron fronts of a cold non-neutral plasma slab with a quasi-neutral core bounded by layers containing only ions is investigated analytically and exact solutions are obtained. It is found that on average, the plasma expansion time scales linearly with the initial inverse ion plasma frequency as well as the degree of charge imbalance, and no expansion occurs if the cold plasma slab is stationary and overall neutral. However, in both cases, there can exist prominent oscillations on the electron front.

  3. Seismic Behaviour of Masonry Vault-Slab Structures

    SciTech Connect

    Chesi, Claudio; Butti, Ferdinando; Ferrari, Marco

    2008-07-08

    Spandrel walls typically play a structural role in masonry buildings, transferring load from a slab to the supporting vault. Some indications are given in the literature on the behaviour of spandrels under the effect of vertical loads, but little attention is given to the effect coming from lateral forces acting on the building. An opportunity to investigate this problem has come from the need of analyzing a monumental building which was damaged by the Nov. 24, 2004 Val Sabbia earthquake in the north of Italy. The finite element model set up for the analysis of the vault-spandrel-slab system is presented and the structural role resulting for the spandrels is discussed.

  4. Investigating the Farallon Slab with Probabilistic Traveltime Tomography

    NASA Astrophysics Data System (ADS)

    Burdick, S.; Lekic, V.

    2015-12-01

    Subduction of the Farallon Plate beneath North America played a key role in its tectonic development. Seismic constraints on the subducted remnants of the Farallon slab provide evidence needed to better understand the polarity and timing of subduction, the structure of the plate, and its relation to tectonic events like the uplift of the Rocky Mountains. Over the course of its deployment, the USArray Transportable Array (TA) has offered ideal data coverage for investigating the Farallon and related slabs in the upper mantle using seismic tomography and converted wave imaging. With its arrival in the east, data from the TA provides the crossing paths necessary to image the upper reaches of the oldest parts of the plate at mid-mantle depths. We perform a global tomographic inversion using the latest P-wave traveltime picks from TA combined with global catalogue data. While the new velocity model resolves upper mantle slab structure at unprecedented detail in the east, a quantitative grasp of model uncertainty is needed to reliably relate velocity variations to the thermal and mechanical properties of the slabs. In order to quantify the uncertainty of our tomographic model, we employ Transdimensional Hierarchical Bayesian (THB) inversion. THB tomography uses Markov chain Monte Carlo to create an ensemble of velocity models that can be analyzed to statistically infer the best-fit velocities, their uncertainties, and tradeoffs. We present and discuss various representations of uncertainty quantified by THB tomography—error bars, model covariance, multimodal distributions of velocity values—and demonstrate its importance for furthering our understanding of the slab fragments beneath North America. We illustrate how we are able to distinguish between spurious slab fragments from those required by the data. By examining bimodal velocity distributions, we put error bars on the spatial extent of the slabs that can then be analyzed using thermal diffusion modeling. By

  5. Links between fluid circulation, temperature, and metamorphism in subducting slabs

    USGS Publications Warehouse

    Spinelli, G.A.; Wang, K.

    2009-01-01

    The location and timing of metamorphic reactions in subducting lithosph??re are influenced by thermal effects of fluid circulation in the ocean crust aquifer. Fluid circulation in subducting crust extracts heat from the Nankai subduction zone, causing the crust to pass through cooler metamorphic faci??s than if no fluid circulation occurs. This fluid circulation shifts the basalt-to-eclogite transition and the associated slab dehydration 14 km deeper (35 km farther landward) than would be predicted with no fluid flow. For most subduction zones, hydrothermal cooling of the subducting slab will delay eclogitization relative to estimates made without considering fluid circulation. Copyright 2009 by the American Geophysical Union.

  6. Slab Driven Mantle Deformation and Plate-Mantle Decoupling

    NASA Astrophysics Data System (ADS)

    Jadamec, M. A.; MacDougall, J.; Fischer, K. M.

    2015-12-01

    Observations of shear wave splitting derived from local sources in subduction zones suggest viscous flow in the mantle wedge is commonly non-parallel to both the subducting plate velocity vector and the motion of the overriding plate. However, far from the subduction zone trench, observations indicate the fast axis of shear wave splitting tends to align with the velocity vector of the surface plates. Similarly, previous 3D geodynamic models show the slab can drive local decoupling of the mantle and surface plates, in both direction and speed. This suggests that there is some distance from the trench over which there is significant decoupling of the mantle flow from surface plate motion, and that this decoupling zone then decays with continued distance from the trench, resulting in far-field plate-mantle coupling. Here we present results from geodynamic models of subduction coupled with calculations of olivine fabric deformation and synthetic splitting to 1) examine the influence of slab strength, slab dip, and non-Newtonian viscosity on the deformation fabric in the mantle wedge and subslab mantle and 2) quantify the spatial extent and intensity of this slab driven decoupling zone. We compare the deformation fabric in a 2D corner flow solution with varying dip to that of a 2D free subduction model with varying initial dip and slab strength. The results show that using an experimentally derived flow law to define viscosity (both diffusion creep and dislocation creep deformation mechanisms) has a first order effect on the viscosity structure and flow velocity in the upper mantle. The free subduction models using the composite viscosity formulation produce a zone of subduction induced mantle weakening that results in reduced viscous support of the slab and lateral variability in coupling of the mantle to the base of the surface plates. The maximum yield stress, which places an upper bound on the slab strength, can also have a significant impact on the viscosity

  7. Slab fluid release: localized in space and time

    NASA Astrophysics Data System (ADS)

    John, T.; Gussone, N. C.; Podladchikov, Y. Y.

    2012-12-01

    As subducting oceanic plates descend into the Earth's mantle, increasing pressures and temperatures lead to the progressive destabilization of hydrous mineral phases and the release of H2O-rich fluids. Some fraction of these fluids ascend into the overlying mantle wedge, inducing partial melting, and their "chemical freight" is thought to contribute to the distinctive chemical signature of the resulting arc magmas. Field evidences suggest that channelized fluid flow may be the dominant mechanism for intra-slab fluid flow. Along their pathways within slabs, these fluids can trigger mineral reactions and produce chemical changes in rocks with which they interact. However, the spatial and temporal scales of this fluid flow remain largely unknown. We employed the Ca and Li isotope systems on a fossil high-pressure fluid pathway and its associated reaction halo (Chinese Tianshan), formed at ~70 km depth during subduction of a coherent oceanic slab, allowing us to constrain the fluid flux, fluid source and the duration of the fluid-rock interaction. In the reaction halo, the degree of eclogitization along with Ca concentration increases towards the vein. A high fluid flux is required to obtain the observed Ca increase and changes in δ44/40Ca. The Ca isotope composition indicate mixing of two distinct Ca sources, the wall-rock blueschist and an external fluid source, the latter of which is enriched in heavy Ca isotopes. The relatively high δ44/40Ca (>1.3‰) of the infiltrating fluid is suggestive of partially hydrated slab mantle as the fluid source. Alternatively, Ca derived from MORB, (0.7 to 0.9‰) and AOC (0.6 to 1.0‰) might evolve towards heavier Ca isotope values while it is ascending through the slab and reacting with wall-rocks and forming carbonates, which are usually associated with the flow structures. This is because calcium carbonate precipitation preferentially removes light Ca from the fluid while the residual fluid will get heavier proportional to

  8. Visibility related to backscatter at 1.54 micron

    NASA Technical Reports Server (NTRS)

    Barber, T. L.; Larson, D. R.

    1986-01-01

    The lidar process was shown to have the necessary potential to fulfill the need for a remote measurement of visibility. Visibility can be inferred from a lidar return optical extinction. The wavelength 1.54 micron was chosen, being near the visible wavelength region and having a high eye safety threshol, 200,000 times higher than 1.06 micron; 1.54 is the erbium laser wavelength. This research utilized 105 measured height profiles of natural droplet size distributions data, taken in clouds, fog, and haze. These profiles were examined to determine the completeness of the droplet counting data. It was found that the particle spectrometer data were incomplete in the very light ford and haze so this portion of the data was eliminated. Utilizing the Mie theory, these droplet size distribution profiles were converted to backscatter at 1.54 micron and extinction in the visible region, 0.55 micron. Using Koschmeider's relationship, the extinction profiles were converted to visibility. The visibility and backscatter profiles were compared to develop a relationship between visibility and backscatter at 1.54 micron.

  9. RAW COPPER SLABS USED IN CASTING OPERATIONS AT BUFFALO PLANT ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    RAW COPPER SLABS USED IN CASTING OPERATIONS AT BUFFALO PLANT OF AMERICAN BRASS COMPANY. MATERIALS STORAGE FOR THE CAST SHOP NOW OCCUPIES A PORTION OF THE ORIGINAL BRASS MILL BUILT BY THE BUFFALO COPPER AND BRASS ROLLING MILL IN 1906-07 AND EXPANDED IN 1911. - American Brass Foundry, 70 Sayre Street, Buffalo, Erie County, NY

  10. Topological optical Bloch oscillations in a deformed slab waveguide.

    PubMed

    Longhi, Stefano

    2007-09-15

    Spatial Bloch oscillations of light waves of purely topological origin are theoretically shown to exist in weakly deformed slab waveguides. As the optical rays trapped in the deformed waveguide can roll freely, wave diffraction is strongly affected by the topology of the deformed surface, which can be tailored to simulate the effect of a tilted periodic refractive index.

  11. 8. WEST FLAME DEFLECTOR FROM REINFORCED CONCRETE SLAB ROOF, FORMER ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    8. WEST FLAME DEFLECTOR FROM REINFORCED CONCRETE SLAB ROOF, FORMER DRAINAGE AREA IN THE DISTANCE, VIEW TOWARDS NORTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-1, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  12. 6. NO. 2 CONTINUOUS SLAB REHEATING FURNACE OF THE 160' ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    6. NO. 2 CONTINUOUS SLAB REHEATING FURNACE OF THE 160' PLATE MILL. FURNACE SHOWING DURING DEMOLITION. C HOOK USED TO CHANGE ROLLS IS VISIBLE IN FRONT OF FURNACE. - U.S. Steel Homestead Works, 160" Plate Mill, Along Monongahela River, Homestead, Allegheny County, PA

  13. 52. SLABBING AND BLOOMING MILLS AND FOUNDRY (IN FOREGROUND), AS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    52. SLABBING AND BLOOMING MILLS AND FOUNDRY (IN FOREGROUND), AS SEEN FROM THE CLARK AVENUE BRIDGE. AT RIGHT, REAR, IS THE BASIC OXYGEN FURNACE. VIEW LOOKING NORTH. - Corrigan, McKinney Steel Company, 3100 East Forty-fifth Street, Cleveland, Cuyahoga County, OH

  14. Workmen and Crawler Crane pouring roof slab and parapet wall ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Workmen and Crawler Crane pouring roof slab and parapet wall of building - looking northwest. Taken Nov. 15, 1929. 14th Naval District Photo Collection Item No. 7165 - U.S. Naval Base, Pearl Harbor, Exterior Cranes, Waterfront Crane Track System, Pearl City, Honolulu County, HI

  15. Subduction of the Indian Lithospheric Slab Beneath Tibet

    NASA Astrophysics Data System (ADS)

    Zhou, H.; Murphy, M. A.

    2001-12-01

    In order to characterize the dynamics of continent-continent collisions, it is essential to define its present geometry and physical state. We report the results of a seismic tomography study of the Tibet-Himalayan collision zone, using a global data set, which indicates that the Indian lithospheric slab has been subducted subhorizontally beneath nearly the entire Tibetan plateau to depths of 165-260 km. Tibetan velocity structure is low in the crust and high in mantle lithosphere at depths between 75-120 km. An asthenospheric layer overlies the subducted Indian slab at depths between 120-165 km beneath the Tibetan plateau. There is a large low-velocity anomaly north of the Indus-Yalu suture zone between 85ºE and 93ºE that extends from the crust down to at least 310 km depth beneath the plateau. This low-velocity anomaly is indicative of mantle upwelling through a weakened zone of the subducted slab. The extent to which India has subducted beneath Tibet, as revealed by these seismic images, is comparable to estimates of crustal shortening across the Himalaya. Moreover, we hypothesize that the buoyancy due to heating of the subducted Indian slab and the existence of the asthenospheric layer contribute to the elevation and flatness of the Tibetan plateau.

  16. 18. FOURTH FLOOR BLDG. 28, RAISED CONCRETE SLAB FLOOR WITH ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    18. FOURTH FLOOR BLDG. 28, RAISED CONCRETE SLAB FLOOR WITH BLOCKS AND PULLEYS OVERHEAD LOOKING NORTHEAST. - Fafnir Bearing Plant, Bounded on North side by Myrtle Street, on South side by Orange Street, on East side by Booth Street & on West side by Grove Street, New Britain, Hartford County, CT

  17. Photonic-crystal slab for terahertz-wave technology platform

    NASA Astrophysics Data System (ADS)

    Fujita, Masayuki

    2016-03-01

    Photonic crystals manipulate photons in a manner analogous to solid-state crystals, and are composed of a dielectric material with a periodic refractive index distribution. In particular, two-dimensional photonic-crystal slabs with high index contrasts (semiconductor/air) are promising for practical applications, owing to the strong optical confinement in simple, thin planar structures. This paper presents the recent progress on a silicon photonic-crystal slab as a technology platform in the terahertz-wave region, which is located between the radio and light wave regions (0.1-10 THz). Extremely low-loss (<0.1 dB/cm) terahertz waveguides based on the photonic-bandgap effect as well as dynamic control and modulation of a terahertz-wave transmission in a photonic-crystal slab by the effective interaction between photoexcited carriers and the terahertz-wave trapping due to the photonic band-edge effect are demonstrated. Terahertz photonic-crystal slabs hold the potential for developing ultralow-loss, compact terahertz components and integrated devices used in applications including wireless communication, spectroscopic sensing, and imaging.

  18. Tensor-guided fitting of subduction slab depths

    USGS Publications Warehouse

    Bazargani, Farhad; Hayes, Gavin P.

    2013-01-01

    Geophysical measurements are often acquired at scattered locations in space. Therefore, interpolating or fitting the sparsely sampled data as a uniform function of space (a procedure commonly known as gridding) is a ubiquitous problem in geophysics. Most gridding methods require a model of spatial correlation for data. This spatial correlation model can often be inferred from some sort of secondary information, which may also be sparsely sampled in space. In this paper, we present a new method to model the geometry of a subducting slab in which we use a data‐fitting approach to address the problem. Earthquakes and active‐source seismic surveys provide estimates of depths of subducting slabs but only at scattered locations. In addition to estimates of depths from earthquake locations, focal mechanisms of subduction zone earthquakes also provide estimates of the strikes of the subducting slab on which they occur. We use these spatially sparse strike samples and the Earth’s curved surface geometry to infer a model for spatial correlation that guides a blended neighbor interpolation of slab depths. We then modify the interpolation method to account for the uncertainties associated with the depth estimates.

  19. 62. SUPPORT CARRIAGE ASSEMBLY AT BASE OF VAL LAUNCHING SLAB ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    62. SUPPORT CARRIAGE ASSEMBLY AT BASE OF VAL LAUNCHING SLAB AFTER TRANSFER FROM BARGE IN FOREGROUND, February, 11, 1948. (Original photograph in possession of Dave Willis, San Diego, California.) - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  20. 30. VAL LOOKING DOWN THE LAUNCHER SLAB STAIRS AT THE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    30. VAL LOOKING DOWN THE LAUNCHER SLAB STAIRS AT THE PROJECTILE LOADING CAR AND LOADING PLATFORM ADJACENT TO THE PROJECTILE LOADING DECK AND LAUNCHER BRIDGE. - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  1. 63. VIEW LOOKING DOWN VAL LAUNCHING SLAB SHOWING DRIVE GEARS, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    63. VIEW LOOKING DOWN VAL LAUNCHING SLAB SHOWING DRIVE GEARS, CABLES, LAUNCHER RAILS, PROJECTILE CAR AND SUPPORT CARRIAGE, April 8, 1948. (Original photograph in possession of Dave Willis, San Diego, California.) - Variable Angle Launcher Complex, Variable Angle Launcher, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA

  2. Enhancement of polarizabilities of cylinders with cylinder-slab resonances

    PubMed Central

    Xiao, Meng; Huang, Xueqin; Liu, H.; Chan, C. T.

    2015-01-01

    If an object is very small in size compared with the wavelength of light, it does not scatter light efficiently. It is hence difficult to detect a very small object with light. We show using analytic theory as well as full wave numerical calculation that the effective polarizability of a small cylinder can be greatly enhanced by coupling it with a superlens type metamaterial slab. This kind of enhancement is not due to the individual resonance effect of the metamaterial slab, nor due to that of the object, but is caused by a collective resonant mode between the cylinder and the slab. We show that this type of particle-slab resonance which makes a small two-dimensional object much “brighter” is actually closely related to the reverse effect known in the literature as “cloaking by anomalous resonance” which can make a small cylinder undetectable. We also show that the enhancement of polarizability can lead to strongly enhanced electromagnetic forces that can be attractive or repulsive, depending on the material properties of the cylinder. PMID:25641391

  3. Applications of acoustics in the measurement of coal slab thickness

    NASA Technical Reports Server (NTRS)

    Hadden, W. J., Jr.; Mills, J. M.; Pierce, A. D.

    1980-01-01

    The determination of the possibility of employing acoustic waves at ultrasonic frequencies for measurements of thicknesses of slabs of coal backed by shale is investigated. Fundamental information concerning the acoustical properties of coal, and the relationship between these properties and the structural and compositional parameters used to characterize coal samples was also sought. The testing device, which utilizes two matched transducers, is described.

  4. Emplacement of the Kodiak batholith and slab-window migration

    USGS Publications Warehouse

    Farris, David W.; Haeussler, P.; Friedman, R.; Paterson, S.R.; Saltus, R.W.; Ayuso, R.

    2006-01-01

    The Kodiak batholith is one of the largest, most elongate intrusive bodies in the forearc Sanak-Baranof plutonic belt located in southern Alaska. This belt is interpreted to have formed during the subduction of an oceanic spreading center and the associated migration of a slab window. Individual plutons of the Kodiak batholith track the location and evolution of the underlying slab window. Six U/Pb zircon ages from the axis of the batholith exhibit a northeastward-decreasing age progression of 59.2 ± 0.2 Ma at the southwest end to 58.4 ± 0.2 Ma at the northeast tip. The trench-parallel rate of age progression is within error of the average slab-window migration rate for the entire Sanak-Baranof belt (~19 cm/yr). Structural relationships, U/Pb ages, and a model of new gravity data indicate that magma from the Kodiak batholith ascended 5-10 km as a northeastward-younging series of 1-8-km-diameter viscoelastic diapirs. Individual plutons ascended by multiple emplacement mechanisms including downward flow, collapse of wall rock, stoping, and diking. Stokes flow xenolith calculations suggest ascent rates of 5-100 m/yr and an effective magmatic viscosity of 107-108 Pa s. Pre-existing structural or lithologic heterogeneities did not dominantly control the location of the main batholith. Instead, its location was determined by migration of the slab window at depth. 

  5. 11. VIEW OF PLACING STEEL FOR POURING OF FIRST SLABS ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    11. VIEW OF PLACING STEEL FOR POURING OF FIRST SLABS OF SPILLWAY CHUTE FROM VICINITY OF WESTERN SIDE OF SPILLWAY APRON, FACING SOUTH. September 1928 - Cushman No. 1 Hydroelectric Power Plant, Spillway, North Fork of Skokomish River, 5 miles West of Hood Canal, Hoodsport, Mason County, WA

  6. DETAIL OF THE IMPRESSION IN THE CONCRETE SLAB OF THE ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF THE IMPRESSION IN THE CONCRETE SLAB OF THE SOUTH END OF THE ABOVE-GROUND PORTION. NOTE STEP DOWN TO THE STEEL PLATE IN BACKGROUND. VIEW FACING NORTH - U.S. Naval Base, Pearl Harbor, Ford Island 5-Inch Antiaircraft Battery, Battery Command Center, Ford Island, Pearl City, Honolulu County, HI

  7. DETAIL OF STEEL PLATE SET INTO THE CONCRETE SLAB OF ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    DETAIL OF STEEL PLATE SET INTO THE CONCRETE SLAB OF THE NORTH END OF THE ABOVE-GROUND PORTION. VIEW FACING NORTH - U.S. Naval Base, Pearl Harbor, Ford Island 5-Inch Antiaircraft Battery, Battery Command Center, Ford Island, Pearl City, Honolulu County, HI

  8. Slab melting and magma formation beneath the southern Cascade arc

    NASA Astrophysics Data System (ADS)

    Walowski, K. J.; Wallace, P. J.; Clynne, M. A.; Rasmussen, D. J.; Weis, D.

    2016-07-01

    The processes that drive magma formation beneath the Cascade arc and other warm-slab subduction zones have been debated because young oceanic crust is predicted to largely dehydrate beneath the forearc during subduction. In addition, geochemical variability along strike in the Cascades has led to contrasting interpretations about the role of volatiles in magma generation. Here, we focus on the Lassen segment of the Cascade arc, where previous work has demonstrated across-arc geochemical variations related to subduction enrichment, and H-isotope data suggest that H2O in basaltic magmas is derived from the final breakdown of chlorite in the mantle portion of the slab. We use naturally glassy, olivine-hosted melt inclusions (MI) from the tephra deposits of eight primitive (MgO > 7 wt%) basaltic cinder cones to quantify the pre-eruptive volatile contents of mantle-derived melts in this region. The melt inclusions have B concentrations and isotope ratios that are similar to mid-ocean ridge basalt (MORB), suggesting extensive dehydration of the downgoing plate prior to reaching sub-arc depths and little input of slab-derived B into the mantle wedge. However, correlations of volatile and trace element ratios (H2O/Ce, Cl/Nb, Sr/Nd) in the melt inclusions demonstrate that geochemical variability is the result of variable addition of a hydrous subduction component to the mantle wedge. Furthermore, correlations between subduction component tracers and radiogenic isotope ratios show that the subduction component has less radiogenic Sr and Pb than the Lassen sub-arc mantle, which can be explained by melting of subducted Gorda MORB beneath the arc. Agreement between pMELTS melting models and melt inclusion volatile, major, and trace element data suggests that hydrous slab melt addition to the mantle wedge can produce the range in primitive compositions erupted in the Lassen region. Our results provide further evidence that chlorite-derived fluids from the mantle portion of the

  9. Structure in the nucleus of NGC 1068 at 10 microns

    NASA Technical Reports Server (NTRS)

    Tresch-Fienberg, R.; Fazio, G. G.; Gezari, D. Y.; Lamb, G. M.; Shu, P. K.; Hoffmann, W. F.; Mccreight, C. R.

    1987-01-01

    New 8-13 micron array camera images of the central kiloparsec of Seyfert 2 galaxy NGC 1068 resolve structure that is similar to that observed at visible and radio wavelengths. The images reveal an infrared source which is extended and asymmetric, with its long axis oriented at P.A. 33 deg. Maps of the spatial distribution of 8-13 micron color temperature and warm dust opacity are derived from the multiwavelength infrared images. The results suggest that there exist two pointlike luminosity sources in the central region of NGC 1068, with the brighter source at the nucleus and the fainter one some 100 pc to the northeast. This geometry strengthens the possibility that the 10 micron emission observed from grains in the nucleus is powered by a nonthermal source. In the context of earlier visible and radio studies, these results considerably strengthen the case for jet-induced star formation in NGC 1068.

  10. Structure in the nucleus of NGC 1068 at 10 microns

    NASA Technical Reports Server (NTRS)

    Tresch-Fienberg, R.; Fazio, G. G.; Gezari, D. Y.; Hoffmann, W. F.; Lamb, G. M.; Shu, P. K.; Mccreight, C. R.

    1987-01-01

    New 8 to 13 micron array camera images of the central kiloparsec of Seyfert 2 galaxy NGC 1068 resolve structure that is similar to that observed at visible and radio wavelengths. The images reveal an infrared source which is extended and asymmetric, with its long axis oriented at P.A. 33 deg. Maps of the spatial distribution of 8 to 13 micron color temperature and warm dust opacity are derived from the multiwavelength infrared images. The results suggest that there exist two pointlike luminosity sources in the central regions of NGC 1068, with the brighter source at the nucleus and the fainter one some 100 pc to the northeast. This geometry strengthens the possibility that the 10 micron emission observed from grains in the nucleus is powered by a nonthermal source. In the context of earlier visible and radio studies, these results considerably strengthen the case for jet induced star formation in NGC 1068.

  11. MSX Observations of the Eclipsed Moon at 4 Microns

    NASA Astrophysics Data System (ADS)

    Howard, J. W.; Little, S. J.; Murdock, T. L.

    1997-07-01

    The lunar eclipse of September 27, 1996 presented the opportunity to observe the 4 micron emission from the moon during totality. The Midcourse Space Experiment (MSX) satellite made observations three times during the totality phase of the eclipse. These observations in Bands B1 (4.22 - 4.36 microns) and B2 (4.24 - 4.45 microns) were used to construct images of the eclipsed moon. The images have been analyzed for temperature and location of thermal anomalies on the moon as well as for temperatures of extended maria and highland areas. Maps of the moon to illustrate the location and brightness of thermal anomalies first seen by Saari and Shorthill (1965) and temperature comparisons with microwave measurements of selected regions on the moon (Sandor and Clancy, 1995) will be made. References: Saari, J. M., and R. W. Shorthill, 1965, Nature, 205, p. 964. Sandor, Brad J., and R. Todd Clancy, 1995, Icarus, 115, p. 387.

  12. The Beauty and Limitations of 10 Micron Heterodyne Interferometry (ISI)

    NASA Technical Reports Server (NTRS)

    Danchi, William C.

    2003-01-01

    Until recently, heterodyne interferometry at 10 microns has been the only successful technique for stellar interferometry in the very difficult atmospheric window from 9-12 microns. For most of its operational lifetime the U.C. Berkeley Infrared Spatial Interferometer was a single-baseline two telescope (1.65 m aperture) system using CO2 lasers as local oscillators. This instrument was designed and constructed from 1983-1988, and first fringes were obtained at Mt. Wilson in June 1988. During the past few years, a third telescope was constructed and just recently the first closure phases were obtained at 11.15 microns. We discuss the history, physics and technology of heterodyne interferometry in the mid-infrared, and some key astronomical results that have come from this unique instrument.

  13. Equilibrium Slab Models of Lyman-Alpha Clouds

    NASA Technical Reports Server (NTRS)

    Charlton, Jane C.; Salpeter, Edwin E.; Hogan, Craig J.

    1993-01-01

    We model the L(sub y(alpha)) clouds as slabs of hydrogen with an ionizing extragalactic radiation field incident from both sides. In general, the equilibrium configuration of a slab at redshift z approx. less than 5 is determined by a balance of the gas pressure, gravity (including the effects of a dark matter halo), and the pressure exerted by the inter-galactic medium, P(sub ext). These models have been used to make predictions of the number of slabs as a function of the neutral hydrogen column density, N(sub H). A break in the curve is predicted at the transition between regimes where gravity and pressure are the dominant confining forces, with a less rapid decrease at larger N(sub H). The transition from optically thin to optically thick slabs leads to a gap in the distribution, whose location is governed largely by the spectrum of ionizing radiation. There are certain parallels between lines of sight through the outer HI disk of spiral galaxy with increasing radius, and the progression from damped, to Lyman limit, to forest clouds. We discuss briefly the possibility that at least some of the observed low z forest clouds may be a separate population, associated with galaxies, as suggested by the observations of Bahcall et al. This population could dominate the forest at present if the dark matter attached to galaxies should lead to gravity confinement for this disk population, while the isolated clouds remain pressure confined. The formalism developed in this paper will allow a more detailed study. We also discuss a more general parameter study of the equilibrium configuration of slabs, including mock gravity and L(sub y(alpha)) photon trapping.

  14. Assimilating lithosphere and slab history in 4-D Earth models

    NASA Astrophysics Data System (ADS)

    Bower, Dan J.; Gurnis, Michael; Flament, Nicolas

    2015-01-01

    We develop methods to incorporate paleogeographical constraints into numerical models of mantle convection. Through the solution of the convection equations, the models honor geophysical and geological data near the surface while predicting mantle flow and structure at depth and associated surface deformation. The methods consist of four constraints determined a priori from a plate history model: (1) plate velocities, (2) thermal structure of the lithosphere, (3) thermal structure of slabs in the upper mantle, and (4) velocity of slabs in the upper mantle. These constraints are implemented as temporally- and spatially-dependent conditions that are blended with the solution of the convection equations at each time step. We construct Earth-like regional models with oceanic and continental lithosphere, trench migration, oblique subduction, and asymmetric subduction to test the robustness of the methods by computing the temperature, velocity, and buoyancy flux of the lithosphere and slab. Full sphere convection models demonstrate how the methods can determine the flow associated with specific tectonic environments (e.g., back-arc basins, intraoceanic subduction zones) to address geological questions and compare with independent data, both at present-day and in the geological past (e.g., seismology, residual topography, stratigraphy). Using global models with paleogeographical constraints we demonstrate (1) subduction initiation at the Izu-Bonin-Mariana convergent margin and flat slab subduction beneath North America, (2) enhanced correlation of model slabs and fast anomalies in seismic tomography beneath North and South America, and (3) comparable amplitude of dynamic and residual topography in addition to improved spatial correlation of dynamic and residual topography lows.

  15. Slab melting and magma generation beneath the southern Cascade Arc

    NASA Astrophysics Data System (ADS)

    Walowski, K. J.; Wallace, P. J.; Clynne, M. A.

    2014-12-01

    Magma formation in subduction zones is interpreted to be caused by flux melting of the mantle wedge by fluids derived from dehydration of the downgoing oceanic lithosphere. In the Cascade Arc and other hot-slab subduction zones, however, most dehydration reactions occur beneath the forearc, necessitating a closer investigation of magma generation processes in this setting. Recent work combining 2-D steady state thermal models and the hydrogen isotope composition of olivine-hosted melt inclusions from the Lassen segment of the Cascades (Walowski et al., 2014; in review) has shown that partial melting of the subducted basaltic crust may be a key part of the subduction component in hot arcs. In this model, fluids from the slab interior (hydrated upper mantle) rise through the slab and cause flux-melting of the already dehydrated MORB volcanics in the upper oceanic crust. In the Shasta and Lassen segments of the southern Cascades, support for this interpretation comes from primitive magmas that have MORB-like Sr isotope compositions that correlate with subduction component tracers (H2O/Ce, Sr/P) (Grove et al. 2002, Borg et al. 2002). In addition, mass balance calculations of the composition of subduction components show ratios of trace elements to H2O that are at the high end of the global arc array (Ruscitto et al. 2012), consistent with the role of a slab-derived melt. Melting of the subducted basaltic crust should contribute a hydrous dacitic or rhyolitic melt (e.g. Jego and Dasgupta, 2013) to the mantle wedge rather than an H2O-rich aqueous fluid. We are using pHMELTS and pMELTS to model the reaction of hydrous slab melts with mantle peridotite as the melts rise through the inverted thermal gradient in the mantle wedge. The results of the modeling will be useful for understanding magma generation processes in arcs that are associated with subduction of relatively young oceanic lithosphere.

  16. Thermal emission from Saturn's rings at 380 microns

    SciTech Connect

    Roellig, T.L.; Werner, M.W.; Becklin, E.E.

    1988-03-01

    Two different techniques have been used to derive the Saturn disk's ring brightness temperatures from 380-micron observations: (1) comparisons of these wide-beam observation disk-ring system results with those obtained for an earlier epoch, when the rings were edge-on, then differencing the two measurements to obtain a value for the rings' contribution; and (2) ring contribution resolution during scanning along the disk-ring plane, to yield a B-ring brightness temperature of 39 + or - 8 K at 380 microns. The results obtained indicate a gradual decrease of observed ring brightness temperature from the IR to the radio wavelength range. 24 references.

  17. Planetary observations at a wavelength of 355 microns

    SciTech Connect

    De pater, I.; Ulich, B.L.; Kreysa, E.; Chini, R.; Kaman Aerospace Corp., Tucson, AZ; Max-Planck-Institut fuer Radioastronomie, Bonn )

    1989-05-01

    Brightness temperature measurements have been conducted for Jupiter, Saturn, Uranus, and Neptune, as well as the Galilean satellites Europa, Ganymede, and Callisto, and the asteroid Ceres, at 355 microns. The precise shape of the spectra of these bodies can be used to obtain information on their composition and the state of compactness of their surface/subsurface layers. The temperatures obtained for the giant planets agree with both previous measurements and model atmosphere calculations; the present result for Jupiter is noted to be consistent with a model atmosphere spectrum lacking a CH3-ice cloud, or perhaps with one having small (10-micron) particles. 12 refs.

  18. Discovery of new 2 micron sources in Rho Ophiuchi

    NASA Technical Reports Server (NTRS)

    Barsony, M.; Carlstrom, J. E.; Burton, Michael G.; Russell, A. P. G.; Garden, R.

    1989-01-01

    A 144-sq-arcmin region of the Rho Oph star-forming cloud core was surveyed at 2.2 microns, complete to mK = 14. A total of 61 sources are detected, 26 of which have been previously reported, accounting for a total of 35 new sources with mK = 12-14. There is no turnover in the 2-micron luminosity function of the Rho Oph cloud core to a limiting sensitivity of mK = 14. Two of the newly discovered sources are binary companions to previously cataloged objects.

  19. 2.15 Micron Laser Welding Of Gallbladder Tissue

    NASA Astrophysics Data System (ADS)

    Treat, Michael R.; Oz, Mehmet C.; Popp, Howard W.

    1989-09-01

    Laser welding of biliary tissues would be a valuable technique in conventional and endoscopic surgery. Laser welding would allow the avoidance of potentially lithogenic suture material as a sequela to biliary tract surgery. Laser welding would be compatable from the surgical technical standpoint with fiberoptic endoscopic intrumentation. The 2.15 micron thulium-holmium-chromium laser offers tissue penetration on the order of a few hundred microns. We have hypothesized that this laser might be well suited to performing biliary tissue welding. We evaluated this laser in vitro using canine gallbladder tissue and we were able to achieve histologically satisfactory tissue fusion and immediate bursting strengths above physiologically encountered biliary pressures.

  20. Water Interactions with Micronized Lunar Analogs and Application to the Behavior of Water on the Moon

    NASA Astrophysics Data System (ADS)

    Poston, M.; Grieves, G. A.; Aleksandrov, A.; Hibbitts, C.; Dyar, M. D.; McLain, J.; Johnson, M. A.; Orlando, T. M.

    2011-12-01

    Temperature Program Desorption (TPD) experiments were performed to measure the thermal desorption activation energies of water on lunar regolith analogs. These data provide constraints for modeling water transport and possible formation on/in the lunar regolith, with likely application to other rocky airless solar system bodies as well. Mechanically micronized JSC-1A was chosen to simulate lunar mare regions, micronized albite was used to represent feldspars in the lunar highlands, and synthetic basaltic glass similar to Apollo glasses were examined to constrain the importance of amorphous vs. crystalline phase1 of the lunar surface materials. Water desorption was observed during the initial heating of both mineral samples to 750 K under ultra-high vacuum, with Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) spectra indicating probable recombinative desorption of hydroxyls above ~450 - 500 K. After then intentionally dosing extrinsic water, no dissociative chemisorption of water (i.e. formation of surface hydroxyl sites) was observed on these samples over laboratory timescales. However, JSC-1A and albite were found to have a distribution of molecular chemisorption sites for water with albite samples having at least twice as many as the JSC-1A by mass. The glass slab only exhibited physisorption of water as ice2. Assuming diffusion to be negligible on the experimental timescale, fitting the TPD profile required a distribution function with desorption activation energies ranging from ~0.45 eV (multilayer water ice) up to 1.3 eV3. This distribution function was then used to estimate the concentration of water that could survive the lunar diurnal heating cycle following a saturating pulse of water (such as from a wet impactor). The estimate showed water concentrations would decrease with decreasing latitude (i.e. with increasing maximum surface temperature). Making the assumption that the water exposure had sampled the entire powder film during our

  1. Driving forces: Slab subduction and mantle convection

    NASA Technical Reports Server (NTRS)

    Hager, Bradford H.

    1988-01-01

    Mantle convection is the mechanism ultimately responsible for most geological activity at Earth's surface. To zeroth order, the lithosphere is the cold outer thermal boundary layer of the convecting mantle. Subduction of cold dense lithosphere provides tha major source of negative buoyancy driving mantle convection and, hence, surface tectonics. There are, however, importnat differences between plate tectonics and the more familiar convecting systems observed in the laboratory. Most important, the temperature dependence of the effective viscosity of mantle rocks makes the thermal boundary layer mechanically strong, leading to nearly rigid plates. This strength stabilizes the cold boundary layer against small amplitude perturbations and allows it to store substantial gravitational potential energy. Paradoxically, through going faults at subduction zones make the lithosphere there locally weak, allowing rapid convergence, unlike what is observed in laboratory experiments using fluids with temperature dependent viscosities. This bimodal strength distribution of the lithosphere distinguishes plate tectonics from simple convection experiments. In addition, Earth has a buoyant, relatively weak layer (the crust) occupying the upper part of the thermal boundary layer. Phase changes lead to extra sources of heat and bouyancy. These phenomena lead to observed richness of behavior of the plate tectonic style of mantle convection.

  2. Azimuthally averaged radial S(sub 100 microns)/S(sub 60 microns) dust color temperatures in spiral galaxies

    NASA Technical Reports Server (NTRS)

    Devereux, Nick A.

    1994-01-01

    The IRAS S(sub 100 micron)/S(sub 60 micron) dust color temperature profiles are presented for two nearby spiral galaxies M 101 and M 81. The radial dust temperature profiles provided an important constraint on the origin of the far-infrared luminosity. The observed dust temperature is compared with that expected for diffuse interstellar dust heated by the general interstellar radiation field within each galaxy. The implications for the contribution of cirrus to the far-infrared luminosity of M 101 and M 81 are discussed.

  3. DISPERSION POLYMERIZATION OF STYRENE IN SUPERCRITICAL CARBON DIOXIDE UTILIZING RANDOM COPOLYMERS INCLUDING FLUORINATED ACRYLATE FOR PREPARING MICRON-SIZE POLYSTYRENE PARTICLES. (R826115)

    EPA Science Inventory

    The dispersion polymerization of styrene in supercritical CO2 utilizing CO2-philic random copolymers was investigated. The resulting high yield of polystyrene particles in the micron-size range was formed using various random copolymers as stabilizers. The p...

  4. Micron-gap thermophotovoltaic systems enhanced by nanowires

    NASA Astrophysics Data System (ADS)

    Mirmoosa, Mohammad Sajjad; Simovski, Constantin

    2015-01-01

    We introduce new micron-gap thermophotovoltaic systems enhanced by tungsten nanowires. We theoretically show that these systems allow the frequency-selective super-Planckian spectrum of radiative heat transfer that promises a very efficient generation of electricity. Our system analysis covers practical aspects such as output power per unit area and efficiency of the tap water cooling.

  5. Release of Micronized Copper Particles from Pressure Treated Wood Products

    EPA Science Inventory

    Micronized copper pressure treated lumber (PTL) has recently been introduced to the consumer market as a replacement for ionized copper PTL. The presence of particulate rather than aqueous copper raises concerns about the exposure of humans as well as the environment to the parti...

  6. Biogeography of a human oral microbiome at the micron scale.

    PubMed

    Mark Welch, Jessica L; Rossetti, Blair J; Rieken, Christopher W; Dewhirst, Floyd E; Borisy, Gary G

    2016-02-01

    The spatial organization of complex natural microbiomes is critical to understanding the interactions of the individual taxa that comprise a community. Although the revolution in DNA sequencing has provided an abundance of genomic-level information, the biogeography of microbiomes is almost entirely uncharted at the micron scale. Using spectral imaging fluorescence in situ hybridization as guided by metagenomic sequence analysis, we have discovered a distinctive, multigenus consortium in the microbiome of supragingival dental plaque. The consortium consists of a radially arranged, nine-taxon structure organized around cells of filamentous corynebacteria. The consortium ranges in size from a few tens to a few hundreds of microns in radius and is spatially differentiated. Within the structure, individual taxa are localized at the micron scale in ways suggestive of their functional niche in the consortium. For example, anaerobic taxa tend to be in the interior, whereas facultative or obligate aerobes tend to be at the periphery of the consortium. Consumers and producers of certain metabolites, such as lactate, tend to be near each other. Based on our observations and the literature, we propose a model for plaque microbiome development and maintenance consistent with known metabolic, adherence, and environmental considerations. The consortium illustrates how complex structural organization can emerge from the micron-scale interactions of its constituent organisms. The understanding that plaque community organization is an emergent phenomenon offers a perspective that is general in nature and applicable to other microbiomes. PMID:26811460

  7. Biogeography of a human oral microbiome at the micron scale

    PubMed Central

    Mark Welch, Jessica L.; Rossetti, Blair J.; Rieken, Christopher W.; Dewhirst, Floyd E.; Borisy, Gary G.

    2016-01-01

    The spatial organization of complex natural microbiomes is critical to understanding the interactions of the individual taxa that comprise a community. Although the revolution in DNA sequencing has provided an abundance of genomic-level information, the biogeography of microbiomes is almost entirely uncharted at the micron scale. Using spectral imaging fluorescence in situ hybridization as guided by metagenomic sequence analysis, we have discovered a distinctive, multigenus consortium in the microbiome of supragingival dental plaque. The consortium consists of a radially arranged, nine-taxon structure organized around cells of filamentous corynebacteria. The consortium ranges in size from a few tens to a few hundreds of microns in radius and is spatially differentiated. Within the structure, individual taxa are localized at the micron scale in ways suggestive of their functional niche in the consortium. For example, anaerobic taxa tend to be in the interior, whereas facultative or obligate aerobes tend to be at the periphery of the consortium. Consumers and producers of certain metabolites, such as lactate, tend to be near each other. Based on our observations and the literature, we propose a model for plaque microbiome development and maintenance consistent with known metabolic, adherence, and environmental considerations. The consortium illustrates how complex structural organization can emerge from the micron-scale interactions of its constituent organisms. The understanding that plaque community organization is an emergent phenomenon offers a perspective that is general in nature and applicable to other microbiomes. PMID:26811460

  8. The 100 micron detector development program. [gallium doped germanium photoconductors

    NASA Technical Reports Server (NTRS)

    Moore, W. J.

    1976-01-01

    An effort to optimize gallium-doped germanium photoconductors (Ge:Ga) for use in space for sensitive detection of far infrared radiation in the 100 micron region is described as well as the development of cryogenic apparatus capable of calibrating detectors under low background conditions.

  9. Validar: A Testbed for Advanced 2-Micron Doppler Lidar

    NASA Technical Reports Server (NTRS)

    Koch, Grady J.; Petros, Mulugeta; Barnes, Bruce W.; Beyon, Jeffrey Y.; Amzajerdian, Farzin; Yu, Jirong; Kavaya, Michael J.; Singh, Upendra N.

    2004-01-01

    High-energy 2-microns lasers have been incorporated in a breadboard coherent Doppler lidar to test component technologies and explore applications for remote sensing of the atmosphere. Design of the lidar is presented including aspects in the laser transmitter, receiver, photodetector, and signal processing. Sample data is presented on wind profiling and CO2 concentration measurements.

  10. Five-micron pictures of Jupiter. [infrared and color photography

    NASA Technical Reports Server (NTRS)

    Westphal, J. A.; Matthews, K.; Terrile, R. J.

    1974-01-01

    Several hundred five-micron 'video' pictures of Jupiter, with 1-sec resolution, made during September, October, and December 1973 and compared with color photographs, are shown to exhibit direct, detailed correlations with the darker 'purple' features. Forty-four of these pictures were made just before the Pioneer-10 encounter.

  11. The NASA - Arc 10/20 micron camera

    NASA Technical Reports Server (NTRS)

    Roellig, T. L.; Cooper, R.; Deutsch, L. K.; Mccreight, C.; Mckelvey, M.; Pendleton, Y. J.; Witteborn, F. C.; Yuen, L.; Mcmahon, T.; Werner, M. W.

    1994-01-01

    A new infrared camera (AIR Camera) has been developed at NASA - Ames Research Center for observations from ground-based telescopes. The heart of the camera is a Hughes 58 x 62 pixel Arsenic-doped Silicon detector array that has the spectral sensitivity range to allow observations in both the 10 and 20 micron atmospheric windows.

  12. Enhanced output of soft X-ray lasers using double slab targets

    SciTech Connect

    Moreno, J.C.; Nilsen, J.; Chandler, E.

    1994-06-01

    Double slab neon-like niobium soft x-ray laser experiments have been performed using the Nova laser. The two slabs have their front surfaces facing in opposite directions with either a 300 {mu}m planar separation between them. Separate laser beams irradiate each slab with an intensity on target of 1.3 {times} 10{sup 14} W/cm{sup 2}. Best coupling was observed using a 300 {mu}m separation. The angular divergence of the laser is measured for single slab and double slab configurations. Comparisons to numerical models are discussed.

  13. Slab pull, mantle convection, and Pangaean assembly and dispersal

    NASA Astrophysics Data System (ADS)

    Collins, W. J.

    2003-01-01

    Two global-scale mantle convection cells presently exist on Earth, centred on upwelling zones in the South Pacific Ocean and northeast Africa: one cell (Panthalassan) contains only oceanic plates, the other (Pangaean) contains all the continental plates. They have remained fixed relative to one another for >400 Ma. A transverse (Rheic-Tethyian) subduction system splits the Pangaean cell. Poloidal plate motion in the oceanic cell reflects circumferential pull of Panthalassan slabs, but toroidal flow in the Pangaean cell, reflected by vortex-type motion of continents toward the Altaids of central-east Asia throughout the Phanerozoic, has resulted from the competing slab-pull forces of both cells. The combined slab-pull effects from both cells also controlled Pangaean assembly and dispersal. Assembly occurred during Palaeozoic clockwise toroidal motion in the Pangaean cell, when Gondwana was pulled into Pangaea by the NE-trending Rheic subduction zone, forming the Appalachian-Variscide-Altaid chain. Pangaean dispersal occurred when the Rheic trench re-aligned in the Jurassic to form the NW-trending Tethyside subduction system, which pulled east Gondwanan fragments in the opposite direction to form the Cimmerian-Himalayan-Alpine chain. This re-alignment also generated a new set of (Indian) mid-ocean ridge systems which dissected east Gondwana and facilitated breakup. 100-200-Myr-long Phanerozoic Wilson cycles reflect rifting and northerly migration of Gondwanan fragments across the Pangaean cell into the Rheic-Tethyian trench. Pangaean dispersal was amplified by retreat of the Panthalassan slab away from Europe and Africa, which generated mantle counterflow currents capable of pulling the Americas westward to create the Atlantic Ocean. Thermal blanketing beneath Pangaea and related hotspot activity were part of a complex feedback mechanism that established the breakup pattern, but slab retreat is considered to have been the main driving force. The size and longevity of

  14. Variability of Jupiter's Five-Micron Hot Spot Inventory

    NASA Technical Reports Server (NTRS)

    Yanamandra-Fisher, Padma A.; Orton, G. S.; Wakefield, L.; Rogers, J. H.; Simon-Miller, A. A.; Boydstun, K.

    2012-01-01

    Global upheavals on Jupiter involve changes in the albedo of entire axisymmetric regions, lasting several years, with the last two occurring in 1989 and 2006. Against this backdrop of planetary-scale changes, discrete features such as the Great Red Spot (GRS), and other vortices exhibit changes on shorter spatial- and time-scales. We track the variability of the discrete equatorial 5-micron hot spots, semi-evenly spaced in longitude and confined to a narrow latitude band centered at 6.5degN (southern edge of the North Equatorial Belt, NEB), abundant in Voyager images. Tantalizingly similar patterns were observed in the visible (bright plumes and blue-gray regions), where reflectivity in the red is anti-correlated with 5-microns thermal radiance. Ortiz et al. (1998, GRL, 103) characterized the latitude and drift rates of the hot spots, including the descent of the Galileo probe at the southern edge of a 5-micron hot spot, as the superposition of equatorial Rossby waves, with phase speeds between 99 - 103m/s, relative to System III. We note that the high 5-micron radiances correlate well but not perfectly with high 8.57-micron radiances. Because the latter are modulated primarily by changes in the upper ammonia (NH3) ice cloud opacity, this correlation implies that changes in the ammonia ice cloud field may be responsible for the variability seen in the 5-m maps. During the NEB fade (2011 - early 2012), however, these otherwise ubiquitous features were absent, an atmospheric state not seen in decades. The ongoing NEB revival indicates nascent 5-m hot spots as early as April 2012, with corresponding visible dark spots. Their continuing growth through July 2012 indicates the possit.le re-establishment of Rossby waves. The South Equatorial Belt (SEB) and NEB revivals began similarly with an instability that developed into a major outbreak, and many similarities in the observed propagation of clear regions.

  15. Mantle-slab interaction and redox mechanism of diamond formation.

    PubMed

    Palyanov, Yuri N; Bataleva, Yuliya V; Sokol, Alexander G; Borzdov, Yuri M; Kupriyanov, Igor N; Reutsky, Vadim N; Sobolev, Nikolai V

    2013-12-17

    Subduction tectonics imposes an important role in the evolution of the interior of the Earth and its global carbon cycle; however, the mechanism of the mantle-slab interaction remains unclear. Here, we demonstrate the results of high-pressure redox-gradient experiments on the interactions between Mg-Ca-carbonate and metallic iron, modeling the processes at the mantle-slab boundary; thereby, we present mechanisms of diamond formation both ahead of and behind the redox front. It is determined that, at oxidized conditions, a low-temperature Ca-rich carbonate melt is generated. This melt acts as both the carbon source and crystallization medium for diamond, whereas at reduced conditions, diamond crystallizes only from the Fe-C melt. The redox mechanism revealed in this study is used to explain the contrasting heterogeneity of natural diamonds, as seen in the composition of inclusions, carbon isotopic composition, and nitrogen impurity content. PMID:24297876

  16. Equilibrium slab models of Lyman-alpha clouds

    NASA Technical Reports Server (NTRS)

    Charlton, Jane C.; Salpeter, Edwin E.; Hogan, Craig J.

    1993-01-01

    Solutions for the equilibrium configuration of a slab with ionizing radiation incident equally from both sides are explored. Radiation effects (photoionization, Ly-alpha photon trapping, and mock gravity) as well as external pressure and self gravity (with and without dark matter) are included. The general formalism is applied to structure growth on small scales at very high z due to mock gravity on dust. Emphasis is placed on the application of slab models at z of less than 5, particularly those that may correspond to Ly-alpha forest, Lyman limit, and damped Ly-alpha systems. The regime with a dominant outward force contributed by trapping of Ly-alpha photons is discussed. General expressions are given for the equilibrium, including dark matter, assuming various relationships between the density of the dark matter halo and the total gas column density.

  17. Microwave and THz sensing using slab-pair-based metamaterials

    SciTech Connect

    Kenanakis, G.; Shen, Nianhai; Mavidis, Ch.; Katsarakis, N.; Kafesaki, M.; Soukoulis, Costas M.; Economou, E.N.

    2012-10-15

    In this work the sensing capability of an artificial magnetic metamaterial based on pairs of metal slabs is demonstrated, both theoretically and experimentally, in the microwave regime. The demonstration is based on transmission measurements and simulations monitoring the shift of the magnetic resonance frequency as one changes a thin dielectric layer placed between the slabs of the pairs. Strong dependence of the magnetic resonance frequency on both the permittivity and the thickness of the dielectric layer under detection was observed. The sensitivity to the dielectrics′ permittivity (ε) is larger for dielectrics of low ε values, which makes the approach suitable for sensing organic materials also in the THz regime. The capability of our approach for THz sensing is also demonstrated through simulations.

  18. Non-Fourier heat conduction in an exponentially graded slab

    NASA Astrophysics Data System (ADS)

    Raveshi, M. R.

    2016-03-01

    The present article investigates one-dimensional non-Fourier heat conduction in a functionally graded material by using the differential transformation method. The studied geometry is a finite functionally graded slab, which is initially at a uniform temperature and suddenly experiences a temperature rise at one side, while the other side is kept insulated. A general non-Fourier heat transfer equation related to the functionally graded slab is derived. The problem is solved in the Laplace domain analytically, and the final results in the time domain are obtained by using numerical inversion of the Laplace transform. The obtained results are compared with the exact solution to verify the accuracy of the proposed method, which shows excellent agreement.

  19. Mantle–slab interaction and redox mechanism of diamond formation

    PubMed Central

    Palyanov, Yuri N.; Bataleva, Yuliya V.; Sokol, Alexander G.; Borzdov, Yuri M.; Kupriyanov, Igor N.; Reutsky, Vadim N.; Sobolev, Nikolai V.

    2013-01-01

    Subduction tectonics imposes an important role in the evolution of the interior of the Earth and its global carbon cycle; however, the mechanism of the mantle–slab interaction remains unclear. Here, we demonstrate the results of high-pressure redox-gradient experiments on the interactions between Mg-Ca-carbonate and metallic iron, modeling the processes at the mantle–slab boundary; thereby, we present mechanisms of diamond formation both ahead of and behind the redox front. It is determined that, at oxidized conditions, a low-temperature Ca-rich carbonate melt is generated. This melt acts as both the carbon source and crystallization medium for diamond, whereas at reduced conditions, diamond crystallizes only from the Fe-C melt. The redox mechanism revealed in this study is used to explain the contrasting heterogeneity of natural diamonds, as seen in the composition of inclusions, carbon isotopic composition, and nitrogen impurity content. PMID:24297876

  20. Nonlocal microscopic theory of quantum friction between parallel metallic slabs

    SciTech Connect

    Despoja, Vito

    2011-05-15

    We present a new derivation of the friction force between two metallic slabs moving with constant relative parallel velocity, based on T=0 quantum-field theory formalism. By including a fully nonlocal description of dynamically screened electron fluctuations in the slab, and avoiding the usual matching-condition procedure, we generalize previous expressions for the friction force, to which our results reduce in the local limit. Analyzing the friction force calculated in the two local models and in the nonlocal theory, we show that for physically relevant velocities local theories using the plasmon and Drude models of dielectric response are inappropriate to describe friction, which is due to excitation of low-energy electron-hole pairs, which are properly included in nonlocal theory. We also show that inclusion of dissipation in the nonlocal electronic response has negligible influence on friction.

  1. Scattering by dielectric circular cylinders in a dielectric slab.

    PubMed

    Frezza, Fabrizio; Pajewski, Lara; Ponti, Cristina; Schettini, Giuseppe

    2010-04-01

    An analytical-numerical technique for the solution of the plane-wave scattering problem by a set of dielectric cylinders embedded in a dielectric slab is presented. Scattered fields are expressed by means of expansions into cylindrical functions, and the concept of plane-wave spectrum of a cylindrical function is employed to define reflection and transmission through the planar interfaces. Multiple reflection phenomena due to the presence of a layered geometry are taken into account. Solutions can be obtained for both TM and TE polarizations and for near- and far-field regions. The numerical approach is described and the method is validated by comparison with examples given in the literature, with very good agreement. Results are presented for the scattering by a finite grid of three cylinders embedded in a slab.

  2. Negotiating Multicollinearity with Spike-and-Slab Priors.

    PubMed

    Ročková, Veronika; George, Edward I

    2014-08-01

    In multiple regression under the normal linear model, the presence of multicollinearity is well known to lead to unreliable and unstable maximum likelihood estimates. This can be particularly troublesome for the problem of variable selection where it becomes more difficult to distinguish between subset models. Here we show how adding a spike-and-slab prior mitigates this difficulty by filtering the likelihood surface into a posterior distribution that allocates the relevant likelihood information to each of the subset model modes. For identification of promising high posterior models in this setting, we consider three EM algorithms, the fast closed form EMVS version of Rockova and George (2014) and two new versions designed for variants of the spike-and-slab formulation. For a multimodal posterior under multicollinearity, we compare the regions of convergence of these three algorithms. Deterministic annealing versions of the EMVS algorithm are seen to substantially mitigate this multimodality. A single simple running example is used for illustration throughout.

  3. Slab2 - Providing updated subduction zone geometries and modeling tools to the community

    NASA Astrophysics Data System (ADS)

    Hayes, G. P.; Hearne, M. G.; Portner, D. E.; Borjas, C.; Moore, G.; Flamme, H.

    2015-12-01

    The U.S. Geological Survey database of global subduction zone geometries (Slab1.0) combines a variety of geophysical data sets (earthquake hypocenters, moment tensors, active source seismic survey images of the shallow subduction zone, bathymetry, trench locations, and sediment thickness information) to image the shape of subducting slabs in three dimensions, at approximately 85% of the world's convergent margins. The database is used extensively for a variety of purposes, from earthquake source imaging, to magnetotelluric modeling. Gaps in Slab1.0 exist where input data are sparse and/or where slabs are geometrically complex (and difficult to image with an automated approach). Slab1.0 also does not include information on the uncertainty in the modeled geometrical parameters, or the input data used to image them, and provides no means to reproduce the models it described. Currently underway, Slab2 will update and replace Slab1.0 by: (1) extending modeled slab geometries to all global subduction zones; (2) incorporating regional data sets that may describe slab geometry in finer detail than do previously used teleseismic data; (3) providing information on the uncertainties in each modeled slab surface; (4) modifying our modeling approach to a fully-three dimensional data interpolation, rather than following the 2-D to 3-D steps of Slab1.0; (5) migrating the slab modeling code base to a more universally distributable language, Python; and (6) providing the code base and input data we use to create our models, such that the community can both reproduce the slab geometries, and add their own data sets to ours to further improve upon those models in the future. In this presentation we describe our vision for Slab2, and the first results of this modeling process.

  4. Density Structures of Oceanic Slabs and Surrounding Mantle Around the 660 km Discontinuity: Implications for the Fate of Old and Young Slabs

    NASA Astrophysics Data System (ADS)

    Ganguly, J.; Saxena, S. K.; Freed, A. M.

    2007-05-01

    We calculated density variations as a function of temperature around the 660 km deep seismic discontinuity in the Earth's mantle in different types of compositional units associated with a subducting slab and the ambient mantle. The calculations are based on computational thermodynamic approach of minimization of Gibbs free energy at a specified P-T condition, subject to the bulk compositional constraints of the system, that simultaneously yield stable mineral assemblage, mineral compositions and modal abundances. These results are converted to density profiles using appropriate data for physical properties and equations of state that are applicable to high P-T conditions. In addition, we also calculated thermal structures of several slabs, with the extremes being given by Tonga (140 Myr at trench, vertical velocity: 14 cm/yr; average dip: 60 degrees) and Peru (41 Myr, 4.4 cm/yr, 35 degrees). A slab was assumed to be lithologically stratified with a top basaltic crust, followed downwards by residual harzburgite and slightly depleted pyrolite. The surrounding mantle is taken to be undepleted pyrolite. Integration of the results of thermal and density calculations show that that all components of the Tonga slab are heavier than both ambient and thermally perturbed adjacent mantle, which has been cooled due to contact with the slab. Thus, old slabs with thermal minimum below 750 C, as in Tonga, should easily penetrate into the lower mantle unless resisted by slab roll back and/or a viscosity jump at the top of the lower mantle. In contrast, the harzburgite layer in warmer slabs, such as Peru, Marianas and Izu-Bonin, is slightly lighter than ambient mantle, causing near neutral or marginally negative net buoyancy of the slab. In this case, other factors, such as rollback and slab dip angle, may explain why some slabs in the northwest Pacific appear to penetrate into the lower mantle while others do not. In Peru-type warm slabs, buoyancy of the harzburgite layer may

  5. Dynamics of Mantle Circulation Associated with Slab Window Formation: Insights from 3D Laboratory Models

    NASA Astrophysics Data System (ADS)

    Guillaume, B.; Funiciello, F.; Moroni, M.; Faccenna, C.; Martinod, J.

    2009-12-01

    Slab window can form either by the intersection of a spreading ridge with a subduction zone or because of internal deformation of the slab that leads to its disruption. The main consequences of this phenomenon are the modifications of the physical, chemical and thermal conditions in the backarc mantle that in turn affect the tectonic and magmatic evolution of the overriding plate. We performed laboratory models of a two-layer linear viscous slab (silicone putty)-upper mantle (glucose syrup) system to quantitatively investigate the pattern of mantle circulation within the slab window (using Feature Tracking image analysis technique) and its influence on the kinematics of the system. Two different geometries have been tested considering a window located (a) at slab edges or (b) within the slab. Kinematic consequences of slab window have been explored to understand the dynamics of the mantle-slab interaction. Configuration (a) implies a reduction of the slab width (W) during subduction and is characterized by toroidal fluxes around the slab edges. The abrupt opening of lateral slab windows produces an acceleration of the trench retreat and subduction velocity, such as 40% for a three-fold width reduction. We interpret this behavior as mostly due to the decrease in the toroidal flow inside subduction windows, scaling with W2. Configuration (b) has been designed to explore the pattern of mantle flow within the window in the case of a laterally constrained subduction system. Slab window, which had a width (Ww) fixed to 15 % of the slab width, opened in the trench-perpendicular direction. It produced the formation of two toroidal mantle cells, centered on the slab midpoint and laterally growing as the slab window enlarged. Particles extruded through the slab window did not mix with particles located in the mantle wedge, the boundary between both reaching distances from the trench up to 3×Ww in the trench-perpendicular direction, and up to 1.5×Ww from the window edge in

  6. Slab detachment under the Eastern Alps seen by seismic anisotropy

    PubMed Central

    Qorbani, Ehsan; Bianchi, Irene; Bokelmann, Götz

    2015-01-01

    We analyze seismic anisotropy for the Eastern Alpine region by inspecting shear-wave splitting from SKS and SKKS phases. The Eastern Alpine region is characterized by a breakdown of the clear mountain-chain-parallel fast orientation pattern that has been previously documented for the Western Alps and for the western part of the Eastern Alps. The main interest of this paper is a more detailed analysis of the anisotropic character of the Eastern Alps, and the transition to the Carpathian–Pannonian region. SK(K)S splitting measurements reveal a rather remarkable lateral change in the anisotropy pattern from the west to the east of the Eastern Alps with a transition area at about 12°E. We also model the backazimuthal variation of the measurements by a vertical change of anisotropy. We find that the eastern part of the study area is characterized by the presence of two layers of anisotropy, where the deeper layer has characteristics similar to those of the Central Alps, in particular SW–NE fast orientations of anisotropic axes. We attribute the deeper layer to a detached slab from the European plate. Comparison with tomographic studies of the area indicates that the detached slab might possibly connect with the lithosphere that is still in place to the west of our study area, and may also connect with the slab graveyard to the East, at the depth of the upper mantle transition zone. On the other hand, the upper layer has NW–SE fast orientations coinciding with a low-velocity layer which is found above a more-or-less eastward dipping high-velocity body. The anisotropy of the upper layer shows large-scale NW–SE fast orientation, which is consistent with the presence of asthenospheric flow above the detached slab foundering into the deeper mantle. PMID:25843968

  7. Slab pull and the seismotectonics of subducting lithosphere.

    USGS Publications Warehouse

    Spence, W.

    1987-01-01

    This synthesis links many seismic and tectonic processes at subduction zones, including great subduction earthquakes, to the sinking of subducted plate. Earthquake data and tectonic modeling for subduction zones indicate that the slab pull force is much larger than the ridge push force. Interactions between the forces that drive and resist plate motions cause spatially and temporally localized stress that lead to characteristic earthquake activity, providing details on how subduction occurs.-from Author

  8. Project B: Improved Liquid Steel Feed For Slab Casters

    SciTech Connect

    Brent S. Isaacson; Mike Slepian; Thomas Richter

    1998-10-01

    This report describes the completion of the development of an electromagnetic valve to control liquid steel flow for improved liquid steel feeding for slab casters. Achievements result from a joint research effort between Westinghouse Science and Technology Center, North American Refractories and U.S. Steel. This effort is part of the American Iron and Steel Institute's (AISI) Advanced Process Control Program, a collaboration between the U.S. Department of Energy (DOE) and fifteen North American steel makers.

  9. Block-slider model for ductile instabilities in subducting slabs

    NASA Astrophysics Data System (ADS)

    Riedel, M. R.

    2003-04-01

    It has been suggested that the occurence of ductile (or plastic) instabilities in the deeper portion of subducting slabs is the dominating mechanism for the generation of intermediate-depth and deep-focus earthquakes. Heat generated during viscous deformation provides a positive feedback to creep and eventually faulting under high pressure. Recent detailed receiver function images of the structure of the Japan subduction zone seem to provide support for this notion. First, there is no indication of an existing metastable olivine wedge. Second, the intermediate-depth seismicity seems to be located in the strong and colder portions of the downgoing slab, about 30 km below the oceanic Moho. This suggests that instead of dehydration or phase transformation triggered events, ductile faulting is its predominating cause. In a recent paper, we have discussed the necessary conditions for ductile instabilities to develop in the bended subducting mantle lithosphere, based on the available experimental data on viscous creep of olivine resp. spinel (*). The present paper aims at a numerical study of the time evolution of a nucleated instability. For this purpose, we develop a cellular block-slider model for ductile instabilities in the mantle lithosphere, in analogy to the frequently used and highly successful block-slider models for brittle fracture of the crust. The block-slider approach is numerically much less demanding than solutions based on the corresponding, thermal-mechanically coupled continuum equations. Furthermore, it allows a straightforward inclusion of possible non-equilibrium effects associated with mineral phase transformations in a subducting slab (kinetic overshoot, grainsize reduction). The obtained numerical results are compared with seismological observation. It is shown, e.g., that the existence of metastable olivine in the deeper portion of a slab (below 500 km) is not a necessary condition for the generation of deep-focus earthquakes. (*) S. Karato, M

  10. Oscillation modes and transmission into a Fibonacci slab

    NASA Astrophysics Data System (ADS)

    Castro-Arce, Lamberto; Molinar-Tabares, Martin; Campos-Garcia, Julio; Figueroa-Navarro, Carlos; Isasi-Siqueiros, Leonardo; Manzanares-Martinez, Betsabe

    In our contribution we developed a study on the behavior of the transmission modes and a Pt / Zn slab of a Fibonacci array of longitudinal and transverse acoustic waves. We have worked with arrangements from n = 1 to10 and has managed to find the energy bands and transmission, filling factor 0.4 observing the appearance of Pseudo-Gaps in the evolution of the study when the arrangement Fibonacci increases. We acknowledge the support of SNI CONACYT.

  11. Deep subduction of hot young oceanic slab required by the Syros eclogites

    NASA Astrophysics Data System (ADS)

    Flemetakis, Stamatis; Moulas, Evangelos; Kostopoulos, Dimitrios; Chatzitheodoridis, Elias

    2014-05-01

    The Cycladic islands of Syros and Siphnos, Aegean Sea, Greece, represent subducted IAT and BABB remnants of the Neotethyan Pindos Ocean. Garnet porphyroblasts (Ø=1mm) in a glaucophane-zoisite eclogite from Kini locality on Syros are compositionally zoned and display a unique prograde heating path from a high-pressure greenschist-facies core with high XSps and low Mg# via a blueschist-facies mantle with moderate XSps and Mg# to an eclogite-facies rim with low XSps and high Mg#. The outermost 35 μm of the garnet rims show flat XSps with rapidly increasing outwards Mg#. Na-Act-Chl-Ph rimmed by Gln mark the greenschist-blueschist facies transition, whereas Pg rimmed by Omp and the incoming of Rt at the expense of Ttn signify the blueschist-eclogite facies transition. Raman barometry of quartz inclusions in the eclogitic garnet rims coupled with elastic modelling of the garnet host [1], and Zr-in-Rt and Grt-Cpx-Ph thermobarometry revealed near-UHP P-T conditions of the order of 2.6 GPa/660°C (maximum residual pressure was 0.8-0.9GPa). By contrast, the greenschist-blueschist transition lies at ~0.75 GPa/355°C. This pressure is in excellent agreement with the position of the albite = jadeite + quartz boundary calculated at 350°C using the observed omphacite composition corrected for jadeite activity (Koons & Thompson, 1985) [2]. As a result, Cpx inclusions in garnet core signify the early entrance of garnet in the subduction zone history of the slab. Furthermore, the early growth of garnet (in lower pressures) observed in eclogites from Syros lies in great agreement with published slab-geotherms that indicate hot subduction and show a precocious garnet growth (Baxter and Caddick, 2013) [3]. The complete absence of lawsonite and the great abundance of zoisite crystals, based on the stability fields of both minerals (Poli et al., 2009) [4], further constrain the P-T trajectory of the slab. Our new P-T estimates match published T distributions on the slab surface

  12. Percutaneous external fixator pins with bactericidal micron-thin sol-gel films for the prevention of pin tract infection.

    PubMed

    Qu, Haibo; Knabe, Christine; Radin, Shula; Garino, Jonathan; Ducheyne, Paul

    2015-09-01

    Risk of infection is considerable in open fractures, especially when fracture fixation devices are used to stabilize the fractured bones. Overall deep infection rates of 16.2% have been reported. The infection rate is even greater, up to 32.2%, with external fixation of femoral fractures. The use of percutaneous implants for certain clinical applications, such as percutaneous implants for external fracture fixation, still represents a challenge today. Currently, bone infections are very difficult to treat. Very potent antibiotics are needed, which creates the risk of irreversible damage to other organs, when the antibiotics are administered systemically. As such, controlled, local release is being pursued, but no such treatments are in clinical use. Herein, the use of bactericidal micron-thin sol-gel films on metallic fracture fixation pins is reported. The data demonstrates that triclosan (2,4,4'-trichloro-2'-hydroxydiphenylether), an antimicrobial agent, can be successfully incorporated into micron-thin sol-gel films deposited on percutaneous pins. The sol-gel films continuously release triclosan in vitro for durations exceeding 8 weeks (longest measured time point). The bactericidal effect of the micron-thin sol-gel films follows from both in vitro and in vivo studies. Inserting percutaneous pins in distal rabbit tibiae, there were no signs of infection around implants coated with a micron-thin sol-gel/triclosan film. Healing had progressed normally, bone tissue growth was normal and there was no epithelial downgrowth. This result was in contrast with the results in rabbits that received control, uncoated percutaneous pins, in which abundant signs of infection and epithelial downgrowth were observed. Thus, well-adherent, micron-thin sol-gel films laden with a bactericidal molecule successfully prevented pin tract infection.

  13. Water-Moderated and -Reflected Slabs of Uranium Oxyfluoride

    SciTech Connect

    Margaret A. Marshall; John D. Bess; J. Blair Briggs; Clinton Gross

    2010-09-01

    A series of ten experiments were conducted at the Oak Ridge National Laboratory Critical Experiment Facility in December 1955, and January 1956, in an attempt to determine critical conditions for a slab of aqueous uranium oxyfluoride (UO2F2). These experiments were recorded in an Oak Ridge Critical Experiments Logbook and results were published in a journal of the American Nuclear Society, Nuclear Science and Engineering, by J. K. Fox, L. W. Gilley, and J. H. Marable (Reference 1). The purpose of these experiments was to obtain the minimum critical thickness of an effectively infinite slab of UO2F2 solution by extrapolation of experimental data. To do this the slab thickness was varied and critical solution and water-reflector heights were measured using two different fuel solutions. Of the ten conducted experiments eight of the experiments reached critical conditions but the results of only six of the experiments were published in Reference 1. All ten experiments were evaluated from which five critical configurations were judged as acceptable criticality safety benchmarks. The total uncertainty in the acceptable benchmarks is between 0.25 and 0.33 % ?k/keff. UO2F2 fuel is also evaluated in HEU-SOL-THERM-043, HEU-SOL-THERM-011, and HEU-SOL-THERM-012, but these those evaluation reports are for large reflected and unreflected spheres. Aluminum cylinders of UO2F2 are evaluated in HEU-SOL-THERM-050.

  14. Time domain evolution of diffuse fields in heterogeneous slabs

    NASA Astrophysics Data System (ADS)

    Turner, Joseph A.

    2005-09-01

    Fundamental studies of elastic wave scattering in heterogeneous media are applicable for problems at several length scales from ultrasonic to seismic waves. The intermediate scattering regime that lies between the single scattering and the diffusion limits is perhaps the least understood. Experiments of elastic wave scattering through a heterogeneous slab have been studied in the time domain using diffusion theory to fit the data. However, numerical solutions of the elastic wave radiative transfer equation (RTE) in the steady state have shown that the conditions for validity of the diffusion limit are only satisfied in the interior of the slab, many mean free paths away from the boundaries. Thus, an examination of the time domain multiple scattering in heterogeneous slabs is important to this class of experiments. The spatial distribution, temporal evolution, and partitioning of the diffuse longitudinal and shear energies are studied as a function of direction and frequency for several types of microstructure including polycrystalline metals and two-phase media using numerical solutions of the RTE. Finally, the ability of a diffusion-type solution to fit RTE solutions is also discussed with applications to inversion of experimental results. [Work supported by DOE.

  15. Ionospheric slab thickness in middle and low latitudes

    SciTech Connect

    Davies, K.; Liu, X.M. )

    1991-08-01

    The equivalent slab thickness of the ionosphere at 15 stations in middle and low latitudes was studied to determine its dependence on solar cycle and location. The data were grouped by season. The following are the major conclusions. There appears to be little or no geographical, or geomagnetic, dependence. The slab thickness varies approximately linearly with the 12-month smoothed values of the 10.7-cm solar radio flux. In middle latitudes the winter midnight thickness is essentially independent of the flux, whereas in summer and equinox the midnight thickness increases with increase of solar flux. The noon thickness increases with increase of solar flux in all seasons. The zero-order Fourier coeffficients for the diurnal curves at all 15 stations were expressed as linear functions of the 10.7-cm flux. The higher harmonic coefficients showed no appreciable dependence on solar flux. The pronounced predawn increase in slab thickness is caused by low values of the maximum electron density, not by increase of total electron content. 10 refs.

  16. Electromagnetic and ultrasonic investigations on a roman marble slab

    NASA Astrophysics Data System (ADS)

    Capizzi, Patrizia; Cosentino, Pietro L.

    2010-05-01

    The archaeological Museum of Rome (Museo delle Terme di Diocleziano) asked our group about the physical consistency of a marble slab (II - III century AD) that has recently fallen down during the transportation for an exhibition. In fact, due to insurance conflict, it was necessary to control the new fractures due to the recent accident and distinguish them from the ancient ones. The sculptured slab (today's size is 1280 x 70 x 9 cm), cut at the ends for a re-use as an inscription in the rear face, was restored (assemblage of different broken parts and cleaning) in contemporary times. We used different methodologies to investigate the slab: namely a pacometer (Protovale Elcometer) to individuate internal coupling pins, GPR (2000 MHz) and Ultrasonic (55 kHz) tomographic high-density surveys to investigate the internal extension of all the visible fractures and to search for the unknown internal ones. For every methodology used the quality of the acquired data was relatively high. They have been processed and compared to give a set of information useful for the bureaucratic problems of the Museum. Later on, the data have been processed in depth, for studying how to improve the data processing and for extracting all the information contained in the whole set of experimental data. Finally, the results of such a study in depth are exposed in detail.

  17. System for loading slab-gel holders for electrophoresis separation

    DOEpatents

    Anderson, Norman G.; Anderson, Norman L.

    1979-01-01

    A slab-gel loading system includes a prismatic chamber for filling a plurality of slab-gel holders simultaneously. Each slab-gel holder comprises a pair of spaced apart plates defining an intermediate volume for gel containment. The holders are vertically positioned in the chamber with their major surfaces parallel to the chamber end walls. A liquid inlet is provided at the corner between the bottom and a side wall of the chamber for distributing a polymerizable monomer solution or a coagulable colloidal solution into each of the holders. The chamber is rotatably supported so that filling can begin with the corner having the liquid inlet directed downwardly such that the solution is gently funneled upwardly, without mixing, along the diverging side and bottom surfaces. As filling proceeds, the chamber is gradually rotated to position the bottom wall in a horizontal mode. The liquid filling means includes a plastic envelope with a septum dividing it into two compartments for intermixing two solutions of different density and thereby providing a liquid flow having a density gradient. The resulting gels have a density gradient between opposite edges for subsequent use in electrophoresis separations.

  18. High Performance Slab-on-Grade Foundation Insulation Retrofits

    SciTech Connect

    Goldberg, Louise F.; Mosiman, Garrett E.

    2015-09-01

    ?A more accurate assessment of SOG foundation insulation energy savings than traditionally possible is now feasible. This has been enabled by advances in whole building energy simulation with 3-dimensional foundation modelling integration at each time step together with an experimental measurement of the site energy savings of SOG foundation insulation. Ten SOG insulation strategies were evaluated on a test building to identify an optimum retrofit insulation strategy in a zone 6 climate (Minneapolis, MN). The optimum insulation strategy in terms of energy savings and cost effectiveness consisted of two components: (a) R-20 XPS insulation above grade, and, (b) R-20 insulation at grade (comprising an outer layer of R-10 insulation and an interior layer of R-12 poured polyurethane insulation) tapering to R-10 XPS insulation at half the below-grade wall height (the lower half of the stem wall was uninsulated). The optimum insulation strategy was applied to single and multi-family residential buildings in climate zone 4 - 7. The highest site energy savings of 5% was realized for a single family home in Duluth, MN, and the lowest savings of 1.4 % for a 4-unit townhouse in Richmond, VA. SOG foundation insulation retrofit simple paybacks ranged from 18 to 47 years. There are other benefits of SOG foundation insulation resulting from the increase in the slab surface temperatures. These include increased occupant thermal comfort, and a decrease in slab surface condensation particularly around the slab perimeter.

  19. Ionospheric slab thickness and its seasonal variations observed by GPS

    NASA Astrophysics Data System (ADS)

    Jin, Shuanggen; Cho, Jung-Ho; Park, Jung-Uk

    2007-11-01

    The ionospheric slab thickness, the ratio of the total electron content (TEC) to the F2-layer peak electron density (NmF2), is closely related to the shape of the ionospheric electron density profile Ne (h) and the TEC. Therefore, the ionospheric slab thickness is a significant parameter representative of the ionosphere. In this paper, the continuous GPS observations in South Korea are firstly used to study the equivalent slab thickness (EST) and its seasonal variability. The averaged diurnal medians of December January February (DJF), March April May (MAM), June July August (JJA) and September October November (SON) in 2003 have been considered to represent the winter, spring, summer and autumn seasons, respectively. The results show that the systematic diurnal changes of TEC, NmF2 and EST significantly appeared in each season and the higher values of TEC and NmF2 are observed during the equinoxes (semiannual anomaly) as well as in the mid-daytime of each season. The EST is significantly smaller in winter than in summer, but with a consistent variation pattern. During 14 16 LT in daytime, the larger EST values are observed in spring and autumn, while the smaller ones are in summer and winter. The peaks of EST diurnal variation are around 10 18 LT which are probably caused by the action of the thermospheric wind and the plasmapheric flow into the F2-region.

  20. Prediction of temperature distribution in the hot rolling of slabs

    NASA Astrophysics Data System (ADS)

    Serajzadeh, S.; Karimi Taheri, A.; Mucciardi, F.

    2002-03-01

    In the process of continuous hot slab rolling, it is vital to know the temperature distribution within the slab along the length of the rolling mill because temperature is the dominant parameter controlling the kinetics of metallurgical transformations and the flow stress of the rolled metal. In other words, the microstructural changes, the mechanical properties as well as the final dimensions of the product and roll-force depend on the temperature distribution within the metal being rolled. In this paper, a mathematical model based on the finite element method is utilized to predict the temperature distribution and microstructural changes during the continuous hot slab rolling process. The effects of various parameters such as the heat of deformation, the work-roll temperature, the rolling speed, and the heat transfer coefficient between the work-roll and the metal are all taken into account in the analyses. To verify the validity of the model and the generated computer code, a comparison is carried out between the theoretical and plant-recorded results.

  1. Electromagnetic and ultrasonic investigations on a Roman marble slab

    NASA Astrophysics Data System (ADS)

    Capizzi, P.; Cosentino, P. L.

    2011-09-01

    The archaeological museum of Rome asked our group about the physical consistency of a marble slab (second to third century AD) that recently fell during its travel as part of an exhibition. We decided to use different methodologies to investigate the slab: namely a pacometer (Protovale Elcometer) to individuate the internal coupling pins, and ground-penetrating radar (GPR) (2000 MHz) and ultrasonic (55 kHz) tomographic high-density surveys to investigate the internal extension of all the visible fractures and to search for the hidden ones. For the ultrasonic data, tests were carried out to optimize the inversion parameters, in particular the cell dimensions. Surely, the choice of cell size for the inversion process must take into account the size of the acquisition grid and the ray number acquired. We proposed to calculate a minimum Fresnel's radius using the sampling frequency instead of that of the probes. For every methodology used, the quality of the acquired data was relatively high. This was then processed and compared to provide information that was useful for some of the insurance problems of the museum. Later on, the data was processed in depth to see how to improve the data processing and interpretation. Finally, the results of this in-depth study were exposed in detail. Ultrasonic and GPR tomographies show a strong correlation, and in particular, the inhomogeneous areas are located in correspondence to the slab injuries.

  2. Application Improvements of Slab-Coupled Optical Fiber Sensors

    NASA Astrophysics Data System (ADS)

    Chadderdon, Spencer Lee

    This dissertation explores techniques for improving slab-coupled optical fiber sensor (SCOS) technology for use in specific applications and sensing configurations. SCOS are advantageous for their small size and all-dielectric composition which permit non-intrusive measurement of electric fields within compact environments; however, their small size also limits their sensitivity. This work performs a thorough analysis of the factors contributing to the performance of SCOS and demonstrates methods which improve SCOS, while maintaining its small dimensions and high level of directional sensitivity. These improvements include increasing the sensitivity by 9x, improving the frequency response to include sub 300 kHz frequencies, and developing a method to tune the resonances. The analysis shows that the best material for the slab waveguide is an electro-optic polymer because of its low RF permittivity combined with high electro-optic coefficient. Additional improvements are based on changing the crystal orientation to a transverse configuration, which enhances the sensitivity due to a combined increase in the effective electro-optic coefficient and electric field penetration into the slab. The transverse SCOS configuration not only improves the overall sensitivity but increases the directional sensitivity of the SCOS. Lithium niobate and electro-optic polymer are both experimentally shown to exhibit minimal frequency dependent sensitivity making them suitable for broad frequency applications. Simultaneous interrogation of multiple SCOS with a single tunable laser is achieved by tuning the resonant wavelengths of KTP SCOS so their resonances overlap.

  3. Infrared spectroscopy over the 2.9-3.9 microns waveband in biochemistry and astronomy

    NASA Astrophysics Data System (ADS)

    Hoyle, F.; Wickramasinghe, N. C.; Al-Mufti, S.; Olavesen, A. H.; Wickramasinghe, D. T.

    1982-04-01

    Astronomical data for the source GC-IRS 7 are compared with infrared spectra of microorganisms sealed within KBr disks heated in an inert atmosphere up to temperatures of at least 380 C. A remarkably close correspondence is shown between the astronomical spectrum and biology, implying the possibility of a firm spectroscopic identification. Transmittance curves over the wavelength range 2.6-3.9 microns were obtained for E. coli at room temperature and at 350 C and for dehydrated vegetative yeast cells. Thermal stability of the biological materials was found up to about 400 C, and the transmittance curves show a surprising invariance of shape between 3.3 and 3.5 microns for both E. coli and the eukaryote. One spectrum could be explicable on the basis of a single grain model subject to irradiation by hard ultraviolet and X-ray quanta. A search for cosmically relevant organic polymers to produce an even tolerable fit to the data led to negative results.

  4. Stabilizing low frequency beam motion in the Tevatron

    SciTech Connect

    Ranjbar, V.H.; /Fermilab

    2005-05-01

    A feed back orbit stabilization system is being developed using a set of BPMS and existing Tevatron corrector magnets to stabilize beam motion up to 50 microns below 25 Hz. The construction of this system is described and the stability limits and magnitude of beam motion reduction is explored.

  5. Detecting lower-mantle slabs beneath Asia and the Aleutians

    NASA Astrophysics Data System (ADS)

    Schumacher, L.; Thomas, C.

    2016-06-01

    To investigate the descend of subducted slabs we search for and analyse seismic arrivals that reflected off the surface of the slab. In order to distinguish between such arrivals and other seismic phases, we search for waves that reach a seismic array with a backazimuth deviating from the theoretical backazimuth of the earthquake. Source-receiver combinations are chosen in a way that their great circle paths do not intersect the slab region, hence the direct arrivals can serve as reference. We focus on the North and Northwest Pacific region by using earthquakes from Japan, the Philippines and the Hindu Kush area recorded at North American networks (e.g. USArray, Alaska and Canada). Using seismic array techniques for analysing the data and record information on slowness, backazimuth and traveltime of the observed out-of-plane arrivals we use these measurements to trace the wave back through a 1-D velocity model to its scattering/reflection location. We find a number of out-of-plane reflections. Assuming only single scattering, most out-of-plane signals have to travel as P-to-P phases and only a few as S-to-P phases, due to the length of the seismograms we processed. The located reflection points present a view of the 3-D structures within the mantle. In the upper mantle and the transition zone they correlate well with the edges of fast velocity regions in tomographic images. We also find reflection points in the mid- and lower mantle and their locations generally agree with fast velocities mapped by seismic tomography models suggesting that in the subduction regions we map, slabs enter the lower mantle. To validate our approach, we calculate and process synthetic seismograms for 3-D wave field propagation through a model containing a slab-like heterogeneity. We show, that depending on the source-receiver geometry relative to the reflection plane, it is indeed possible to observe and back-trace out-of-plane signals.

  6. Opening and closing slab windows in congested subduction zones

    NASA Astrophysics Data System (ADS)

    Moresi, Louis

    2013-04-01

    Subduction zones often try to swallow buoyant material which is embedded in the oceanic lithosphere: plume material or hotspot residues, oceanic plateaux, and fragments of continental material. This often results in the formation of a slab window and it has been shown (Mason et al, 2010; Betts et al, 2012) that this window strongly influences the subsequent evolution of the slab and the advance/retreat rate of the trench. The buoyant material typically pushes the trench into a local state of advance, and the creation of the slab window allows the rest of the trench to retreat as the mantle behind the slab flows in through the window. This situation is inherently unstable: if the buoyancy anomaly is finite in size, then the retreating trench will soon move behind the anomaly and juxtapose negatively buoyant oceanic lithosphere with active subduction. This creates the potential to close the slab window and, in doing so, transfer the buoyant material to the over-riding plate. Models show that this closure of the window initially occurs through a lateral rollback process followed by a catastrophic re-initiation of subduction behind the colliding buoyant anomaly. This rollback leaves a characteristic, tightly rolled remnant in the mantle and significant rotation in the over-riding plate and the newly-docked block. The over-riding plate is thrown into extension perpendicular to the original orientation of the trench. This same situation applies at the late-stages of a closing ocean due to the passive margin geometry and the presence of debris collected from the closing ocean floor and it seems likely that these models can also be applied to the complicated geometry of subduction in such environments. Mason, W. G.; Moresi, L.; Betts, P. G. & Miller, M. S. Three-dimensional numerical models of the influence of a buoyant oceanic plateau on subduction zones Tectonophysics, 2010, 483, 71-79 P. Betts, W. Mason, L. Moresi, The influence of mantle plumes on subduction zone

  7. Design of energy efficient building with radiant slab cooling

    NASA Astrophysics Data System (ADS)

    Tian, Zhen

    2007-12-01

    Air-conditioning comprises a substantial fraction of commercial building energy use because of compressor-driven refrigeration and fan-driven air circulation. Core regions of large buildings require year-round cooling due to heat gains from people, lights and equipment. Negative environmental impacts include CO2 emissions from electric generation and leakage of ozone-depleting refrigerants. Some argue that radiant cooling simultaneously improves building efficiency and occupant thermal comfort, and that current thermal comfort models fail to reflect occupant experience with radiant thermal control systems. There is little field evidence to test these claims. The University of Calgary's Information and Communications Technology (ICT) Building, is a pioneering radiant slab cooling installation in North America. Thermal comfort and energy performance were evaluated. Measurements included: (1) heating and cooling energy use, (2) electrical energy use for lighting and equipment, and (3) indoor temperatures. Accuracy of a whole building energy simulation model was evaluated with these data. Simulation was then used to compare the radiant slab design with a conventional (variable air volume) system. The radiant system energy performance was found to be poorer mainly due to: (1) simultaneous cooling by the slab and heating by other systems, (2) omission of low-exergy (e.g., groundwater) cooling possible with the high cooling water temperatures possible with radiant slabs and (3) excessive solar gain and conductive heat loss due to the wall and fenestration design. Occupant thermal comfort was evaluated through questionnaires and concurrent measurement of workstation comfort parameters. Analysis of 116 sets of data from 82 occupants showed that occupant assessment was consistent with estimates based on current thermal comfort models. The main thermal comfort improvements were reductions in (1) local discomfort from draft and (2) vertical air temperature stratification. The

  8. 60 micron luminosity evolution of rich clusters of galaxies

    SciTech Connect

    Kelly, D.M.; Rieke, G.H. )

    1990-10-01

    The average 60-micron flux has been determined for a collection of optically selected galaxy clusters at redshifts ranging from 0.30 to 0.92. The result, 26 mJy per cluster, represents the faintest flux determination known of using the IRAS data base. The flux from this set of clusters has been compared to the 60-micron flux from a sample of nearby galaxy clusters. It is found that the far-infrared luminosity evolution in cluster galaxies can be no more than a factor of 1.7 from z = 0.4 to the present epoch. This upper limit is close to the evolution predicted for simple aging of the stellar populations. Additional processes such as mergers, cannibalism, or enhanced rates of starbursts appear to occur at a low enough level that they have little influence on the far-infrared emission from clusters over this redshift range. 38 refs.

  9. 60 micron luminosity evolution of rich clusters of galaxies

    NASA Technical Reports Server (NTRS)

    Kelly, Douglas M.; Rieke, George H.

    1990-01-01

    The average 60-micron flux has been determined for a collection of optically selected galaxy clusters at redshifts ranging from 0.30 to 0.92. The result, 26 mJy per cluster, represents the faintest flux determination known of using the IRAS data base. The flux from this set of clusters has been compared to the 60-micron flux from a sample of nearby galaxy clusters. It is found that the far-infrared luminosity evolution in cluster galaxies can be no more than a factor of 1.7 from z = 0.4 to the present epoch. This upper limit is close to the evolution predicted for simple aging of the stellar populations. Additional processes such as mergers, cannibalism, or enhanced rates of starbursts appear to occur at a low enough level that they have little influence on the far-infrared emission from clusters over this redshift range.

  10. FIRBACK: A Large Area 175 micron Survey with ISO

    NASA Astrophysics Data System (ADS)

    Lagache, Guilaine

    We have conducted a deep cosmological large area survey at 175 microns with the ISOPHOT instrument in several high latitude regions relatively free of cirrus contamination. The main, but striking, result of this survey is that number counts of sources above 100 mJy is larger by about an order of magnitude than the extrapolation of the nearby IRAS 60 microns population of infrared galaxies. Nevertheless, these counts are consistent with predictions of the source population responsible for the Cosmic Far InfraRed Background detected with COBE. The FIRBACK collaboration involves J. L. Puget, D. L. Clements, H. Dole, R. Gispert, W. T. Reach, F. R. Bouchet, C. Cesarsky, F. X. Desert, D. Elbaz, A. Franceschini, B. Guiderdoni, M. Harwit, D. Lemke, R. Laureijs and A. F. M Moorwood.

  11. Photometric variability of Charon at 2.2 microns

    NASA Technical Reports Server (NTRS)

    Bosh, A. S.; Young, L. A.; Elliot, J. L.; Hammel, H. B.; Baron, R. L.

    1992-01-01

    Pluto-Charon images obtained on each of four nights at 2.2, 1.2, and 1.7 microns are presently fitted by a two-source image model in which the position of Charon and the ratio of its signal to that of Pluto are free parameters. At 2.2 microns, Charon is fainter than Pluto by magnitudes which, when combined with Pluto-Charon system photometry, yield apparent magnitudes of 15.01 + or - 0.08 for Charon at 0.06 lightcurve phase and 15.46 + or - 0.05 at lightcurve phase 0.42. In view of these results, Charon is variable in this filter bypass due to geometric albedo changes as a function of longitude.

  12. Correlation of infrared reflectance ratios at 2.3 microns/1.6 micron and 1.1 micron/1.6 micron with delta O-18 values delineating fossil hydrothermal systems in the Idaho batholith

    NASA Technical Reports Server (NTRS)

    Gillespie, A. R.; Criss, R. E.

    1983-01-01

    Reflectance ratios from laboratory spectra and airborne multispectral images are found to be strongly correlated with delta O-18 values of granite rocks in the Idaho batholith. The correlation is largely a result of interactions between hot water and rock, which lowered the delta O-18 values of the rocks and produced secondary hydrous material. Maps of the ratio of reflectivities at 2.3 and 1.6 microns should delineate fossil hydrothermal systems and provide estimates of alteration intensity. However, hydrous minerals produced during deuteric alteration or weathering cannot be unambiguously distinguished in remotely sensed images from the products of propylitic alteration without the use of narrow-band scanners. The reflectivity at 1.6 micron is strongly correlated with rock density and may be useful in distinguishing rock types in granitic terranes.

  13. Infrared spectrum of Io, 2.8-5.2 microns

    NASA Astrophysics Data System (ADS)

    Cruikshank, D. P.

    1980-02-01

    The reflectance spectrum of Io is presented from 2.8 to 5.2 microns demonstrating the full extent of the broad and deep spectral absorption between 3.5 and 4.8 microns. Laboratory spectra of nitrates and carbonates diluted with sulfur do not satisfactorily reproduce the Io spectrum, but new information based on recently discovered volcanic activity on the satellite lead to consideration of other classes of compounds reported by Fanale et al. (1979). It is concluded that the variability of the supply of condensible SO2 gas to the surface of Io, its removal by sublimination, and the temporal variations in the strength of the SO2 band may provide an index of volcanic activity on Io that can be monitored from the earth.

  14. Sub-Micron Velocity Measurements near a Moving Contact Line

    NASA Astrophysics Data System (ADS)

    Zimmerman, Jeremiah; Weislogel, Mark M.; Tretheway, Derek C.

    2010-03-01

    The displacement of one fluid by an immiscible second fluid (i.e. dynamic wetting), governs many natural and technological processes. Despite extensive studies, understanding and modeling the displacement process remains one of the outstanding problems in fluid mechanics. In this work, we explore the physics of the moving contact line (the idealized line of intersection between two fluids and a solid) with micron resolution particle image velocimetry (μPIV), which enables sub-micron two-dimensional velocity measurements. The measured flow is generated by dynamic wetting in a glass microchannel. The microchannel is mounted on an automated microscope stage with precise velocity control allowing for the static placement of the contact line within the field of view. Full-field velocity measurements within 1 μm of the contact line were made in water/glycerol and fructose/glucose/water solutions. Preliminary results appear to show remarkable similarity to controversial theoretical predictions.

  15. Visualization study on sedimentation of micron iron oxide particles.

    PubMed

    Chen, Jin-Fang; Luo, Ye; Xu, Jun-Hui; Chen, Qi-Ming; Guo, Jia

    2006-09-15

    In this paper, a novel technique combined light-electronic microscopy and computer imaging trace was used for visualization of the sedimentation of micron iron oxide particles in a customized micro-reactor. Micron iron oxide particles were recovered from the cinder of sulfuric acid production by sedimentation separating and hydraulic rating. Effects of particle size, shape and surface roughness on the sedimentation velocity were investigated. For irregular-shape particles, the sedimentation velocity and the geometric parameters of the particles were measured by the imaging trace technique. A correction coefficient (c) was used to modify the Stokes equation. In this study, the relationship between the correction coefficient and the equivalent diameter (d(p)) was found to be linear: c=0.6272-0.0298d(p), for iron oxide particles with equivalent diameter 4-22 microm.

  16. Radiation Pressure Measurements on Micron-Size Individual Dust Grains

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Craven, P. D.; Spann, J. F.; Witherow, W. K.; West, E. A.; Gallagher, D. L.; Adrian, M. L.; Fishman, G. J.; Tankosic, D.; LeClair, A.

    2003-01-01

    Measurements of electromagnetic radiation pressure have been made on individual silica (SiO2) particles levitated in an electrodynamic balance. These measurements were made by inserting single charged particles of known diameter in the 0.2- to 6.82-micron range and irradiating them from above with laser radiation focused to beam widths of approximately 175- 400 microns at ambient pressures particle due to the radiation force is balanced by the electrostatic force indicated by the compensating dc potential applied to the balance electrodes, providing a direct measure of the radiation force on the levitated particle. Theoretical calculations of the radiation pressure with a least-squares fit to the measured data yield the radiation pressure efficiencies of the particles, and comparisons with Mie scattering theory calculations provide the imaginary part of the refractive index of SiO2 and the corresponding extinction and scattering efficiencies.

  17. Tomographic imaging of the Cascadia subduction zone: Constraints on the Juan de Fuca slab

    NASA Astrophysics Data System (ADS)

    Chen, Chuanxu; Zhao, Dapeng; Wu, Shiguo

    2015-04-01

    We used 40,343 P-wave arrival times from 1883 local earthquakes and 105,455 P-wave arrivals from 6361 teleseismic events to study the detailed structure of the Cascadia subduction zone. We conducted tomographic inversions using a starting velocity model which includes the high-velocity subducting Juan de Fuca slab as a priori information. A number of such slab-constrained inversions are conducted by changing the slab thickness and the velocity contrast between the slab and the surrounding mantle. Our optimal 3-D velocity model fits the data much better than that determined by an inversion with a 1-D homogeneous starting model. Our results show that the subducting Juan de Fuca slab has a thickness of 30-50 km and a P-wave velocity of 1-3% higher than that of the surrounding mantle. Beneath the northern and southern parts of the Cascadia, P-wave velocity is lower in the slab and along the slab interface, which may reflect a more hydrated slab and more active slab dehydration there. The lateral velocity variations may indicate different degrees of slab dehydration and forearc mantle serpentinization. The segmentation in episodic tremor and slip (ETS) is also spatially coincident with the velocity heterogeneities, indicating that the ETS occurrence and recurrence interval are controlled by fluid activity in and around the mantle wedge corner.

  18. Mix-and-match lithography for half-micron technology

    NASA Astrophysics Data System (ADS)

    Flack, Warren W.; Dameron, David H.

    1991-08-01

    Half-micron lithography for a production environment is not considered realistic with currently available lithography tools. While optical steppers have high wafer throughputs, they do not have sufficient process latitude at half-micron geometries. In contrast, advanced technologies with sufficient capabilities for half-micron processing such as direct-write e-beam and x-ray lithography are extremely expensive and have low effective throughputs. A mix-and- match lithography approach can take advantage of the best features of both types of systems by sing an optical stepper for noncritical levels and an advanced lithography system for critical levels. In order to facilitate processing of a triple level metal half-micron CMOS technology, a mix-and-match scheme has been developed between a Hitachi HL-700 D e-beam direct write system and an Ultratech 1500 wide-field 1x stepper. The Hitachi is used to pattern an accurate zero or registration level. All critical levels are exposed on the Hitachi and aligned back to this zero level. The Ultratech is used to align all other process levels which do not have critical targets that are placed on subsequent process levels. The mix-and-match approach is discussed, and optical to e-beam as well as e-beam to optical alignment results from seven production lots are presented. The linear alignment error components X translation, Y translation, rotation and magnification are extracted and analyzed to determine their source. It was found that a simple adjustment improved the registration capabilities of these two lithography tools by reducing the X translation, Y translation and rotation standard deviations by a factor of two or more, while greatly reducing the magnification errors between the two tools.

  19. Two micron pore size MCP-based image intensifiers

    NASA Astrophysics Data System (ADS)

    Glesener, John; Estrera, Joseph

    2010-02-01

    Image intensifiers (I2) have many advantages as detectors. They offer single photon sensitivity in an imaging format, they're light in weight and analog I2 systems can operate for hours on a single AA battery. Their light output is such as to exploit the peak in color sensitivity of the human eye. Until recent developments in CMOS sensors, they also were one of the highest resolution sensors available. The closest all solid state solution, the Texas Instruments Impactron chip, comes in a 1 megapixel format. Depending on the level of integration, an Impactron based system can consume 20 to 40 watts in a system configuration. In further investing in I2 technology, L-3 EOS determined that increasing I2 resolution merited a high priority. Increased I2 resolution offers the system user two desirable options: 1) increased detection and identification ranges while maintaining field-of-view (FOV) or 2) increasing FOV while maintaining the original system resolution. One of the areas where an investment in resolution is being made is in the microchannel plate (MCP). Incorporation of a 2 micron MCP into an image tube has the potential of increasing the system resolution of currently fielded systems. Both inverting and non-inverting configurations are being evaluated. Inverting tubes are being characterized in night vision goggle (NVG) and sights. The non-inverting 2 micron tube is being characterized for high resolution I2CMOS camera applications. Preliminary measurements show an increase in the MTF over a standard 5 micron pore size, 6 micron pitch plate. Current results will be presented.

  20. Electromagnetic Emission at Micron Wavelengths from Active Nerves

    PubMed Central

    Fraser, Allan; Frey, Allan H.

    1968-01-01

    In recent years there has been experimental work and speculation bearing upon the significance in neural functioning of electromagnetic energy in the region of the spectrum between 0.3 and 10 μ. We demonstrate, in this experiment, micron wavelength electromagnetic emission from active live crab nerves as compared to inactive live and dead nerves. Further, the data indicate that the active nerve emission is caused by specific biophysical reactions rather than being simply black-body radiation. PMID:5699805

  1. Scanning SQUID susceptometers with sub-micron spatial resolution

    NASA Astrophysics Data System (ADS)

    Kirtley, John R.; Paulius, Lisa; Rosenberg, Aaron J.; Palmstrom, Johanna C.; Holland, Connor M.; Spanton, Eric M.; Schiessl, Daniel; Jermain, Colin L.; Gibbons, Jonathan; Fung, Y.-K.-K.; Huber, Martin E.; Ralph, Daniel C.; Ketchen, Mark B.; Gibson, Gerald W.; Moler, Kathryn A.

    2016-09-01

    Superconducting QUantum Interference Device (SQUID) microscopy has excellent magnetic field sensitivity, but suffers from modest spatial resolution when compared with other scanning probes. This spatial resolution is determined by both the size of the field sensitive area and the spacing between this area and the sample surface. In this paper we describe scanning SQUID susceptometers that achieve sub-micron spatial resolution while retaining a white noise floor flux sensitivity of ≈2μΦ0/Hz1/2. This high spatial resolution is accomplished by deep sub-micron feature sizes, well shielded pickup loops fabricated using a planarized process, and a deep etch step that minimizes the spacing between the sample surface and the SQUID pickup loop. We describe the design, modeling, fabrication, and testing of these sensors. Although sub-micron spatial resolution has been achieved previously in scanning SQUID sensors, our sensors not only achieve high spatial resolution but also have integrated modulation coils for flux feedback, integrated field coils for susceptibility measurements, and batch processing. They are therefore a generally applicable tool for imaging sample magnetization, currents, and susceptibilities with higher spatial resolution than previous susceptometers.

  2. A model for the CI (609 micron) emission of Orion

    NASA Technical Reports Server (NTRS)

    Tielens, A. G. G. M.; Hollenbach, D.

    1985-01-01

    A numerical model energy balance and chemical equilibrium in the photodissociation regions at the edge of molecular clouds is presented. The model is used to calculate the emergent intensities of the following fine-structure lines: OI (at 63, 145 microns); CI (at 609, 370 microns); C II (at 158 microns); and the low-lying rotational transitions of CO. It is shown that column densities in the range 2 x 10 to the 17th to 2 x 10 to the 18th per sq cm can be obtained for the C(+)/C/CO transition region at the edges of molecular clouds. The difference in the column densities is attributed to changes in the charge exchange reactions of C(+) with SiO and S, and to the process of carbon self-healing. It is found that the calculations are in good agreement with the observed conditions in the photodissociation regions behind Orion (1) C Ori, and near the surface of OMC 1.

  3. Dissolution and pharmacokinetics of a novel micronized aspirin formulation.

    PubMed

    Voelker, M; Hammer, M

    2012-08-01

    Aspirin (acetylsalicylic acid, ASA) has been used as an analgesic, antipyretic and antiinflammatory drug for many years. A new 500 mg aspirin tablet formulation containing micronized active ingredient and an effervescent component has been developed for potential improvement in the onset of action for acute pain treatment. This paper describes the dissolution and the pharmacokinetics of the new formulation in comparison with regular aspirin tablets, aspirin granules and aspirin effervescent tablets. Micronized aspirin tablets dissolve significantly faster over a pH range from 1.2 to 6.8 compared to regular 500 mg aspirin tablets. Plasma concentration time curve comparison to regular 500 mg aspirin tablets showed a substantial improvement in the time to maximum plasma concentrations (T(max)) (ASA 17.5 min vs. 45 min) and an increase in maximum plasma concentration (C(max)) (ASA 13.8 μg/ml vs. 4.4 μg/ml) while the overall extent of exposure (AUC) remains almost unchanged. The data suggest a potential improvement for onset of action in treating acute pain with the new micronized aspirin formulation.

  4. Dissolution and pharmacokinetics of a novel micronized aspirin formulation.

    PubMed

    Voelker, M; Hammer, M

    2012-08-01

    Aspirin (acetylsalicylic acid, ASA) has been used as an analgesic, antipyretic and antiinflammatory drug for many years. A new 500 mg aspirin tablet formulation containing micronized active ingredient and an effervescent component has been developed for potential improvement in the onset of action for acute pain treatment. This paper describes the dissolution and the pharmacokinetics of the new formulation in comparison with regular aspirin tablets, aspirin granules and aspirin effervescent tablets. Micronized aspirin tablets dissolve significantly faster over a pH range from 1.2 to 6.8 compared to regular 500 mg aspirin tablets. Plasma concentration time curve comparison to regular 500 mg aspirin tablets showed a substantial improvement in the time to maximum plasma concentrations (T(max)) (ASA 17.5 min vs. 45 min) and an increase in maximum plasma concentration (C(max)) (ASA 13.8 μg/ml vs. 4.4 μg/ml) while the overall extent of exposure (AUC) remains almost unchanged. The data suggest a potential improvement for onset of action in treating acute pain with the new micronized aspirin formulation. PMID:22057729

  5. Measuring micron size beams in the SLC final focus

    SciTech Connect

    McCormick, D.; Ross, M.; DeBarger, S.

    1994-10-01

    A pair of high resolution wire scanners have been built and installed in the SLC final focus. The final focus optics uses a set of de-magnifying telescopes, and an ideal location for a beam size monitor is at one of the magnified image points of the interaction point. The image point chosen for these scanners is in the middle of a large bend magnet. The design beam spots here are about 2 microns in the vertical and 20 microns in the horizontal plane. The scanners presented a number of design challenges. In this paper we discuss the mechanical design of the scanner, and fabrication techniques of its ceramic wire support card which holds many 4 and 7 um carbon wires. Accurate motion of the wire during a scan is critical. In this paper we describe tests of stepper motors, gear combinations, and radiation hardened encoders needed to produce the required motion with a step resolution of 80 nanometers. Also presented here are the results of scattered radiation detector placement studies carried out to optimize the signal from the 4 micron wires. Finally, we present measurements from the scanner.

  6. Radiation Pressure Measurements on Micron Size Individual Dust Grains

    NASA Technical Reports Server (NTRS)

    Abbas, M. M.; Craven, P.D.; Spann, J. F.; Tankosic, D.; Witherow, W. K.; LeClair, A.; West, E.; Sheldon, R.; Gallagher, D. L.; Adrian, M. L.

    2003-01-01

    Measurements of electromagnetic radiation pressure have been made on individual silica (SiO2) particles levitated in an electrodynamic balance. These measurements were made by inserting single charged particles of known diameter in the 0.2 micron to 6.82 micron range and irradiating them from above with laser radiation focused to beam-widths of approx. 175-400 micron, at ambient pressures approx. 10(exp -3) to 10(exp -4) torr. The downward displacement of the particle due to the radiation force is balanced by the electrostatic force indicated by the compensating dc potential applied to the balance electrodes, providing a direct measure of the radiation force on the levitated particle. Theoretical calculations of the radiation pressure with a least-squares fit to the measured data yield the radiation pressure efficiencies of the particles, and comparisons with Mie scattering theory calculations provide the imaginary part of the refractive index of silica and the corresponding extinction and scattering efficiencies.

  7. Stable 1.25 watts CW far infrared laser radiation at the 119 micron methanol line

    NASA Technical Reports Server (NTRS)

    Farhoomand, Jam; Pickett, Herbert M.

    1987-01-01

    Far-infrared CW radiation of 1.25 watts has been obtained at the 119 micron methanol line with a CO2 pump power of 125 watts, and the maximum frequency fluctuation of the free running laser is measured to be less than + or - 100 kHz per hour. Reflecting optics have been used, when possible, to minimize CO2 degradation, and the frequency stability is ensured by cooling the input and output couplers. The input and output assemblies within the lasing medium are enclosed to minimize the external effects on the cavity length and to eliminate the mechanical instabilities associated with the use of bellows. The vibrational bottle-neck is broken by cooling the resonator wall to 5 deg and adding He as the buffer gas.

  8. Evaluation of AIRS, MODIS, and HIRS 11 Micron Brightness Temperature Difference Changes from 2002 through 2006

    NASA Technical Reports Server (NTRS)

    Broberg, Steven E.; Aumann, Hartmut H.; Gregorich, David T.; Xiong, X.

    2006-01-01

    In an effort to validate the accuracy and stability of AIRS data at low scene temperatures (200-250 K range), we evaluated brightness temperatures at 11 microns with Aqua MODIS band 31 and HIRS/3 channel 8 for Antarctic granules between September 2002 and May 2006. We found excellent agreement with MODIS (at the 0.2 K level) over the full emperature range in data from early in the Aqua mission. However, in more recent data, starting in April 2005, we found a scene temperature dependence in MODIS-AIRS brightness temperature differences, with a discrepancy of 1- 1.5 K at 200 K. The comparison between AIRS and HIRS/3 (channel 8) on NOAA 16 for the same time period yields excellent agreement. The cause and time dependence of the disagreement with MODIS is under evaluation, but the change was coincident with a change in the MODIS production software from collection 4 to 5.

  9. Sub-micron scale patterning of fluorescent silver nanoclusters using low-power laser

    PubMed Central

    Kunwar, Puskal; Hassinen, Jukka; Bautista, Godofredo; Ras, Robin H. A.; Toivonen, Juha

    2016-01-01

    Noble metal nanoclusters are ultrasmall nanomaterials with tunable properties and huge application potential; however, retaining their enhanced functionality is difficult as they readily lose their properties without stabilization. Here, we demonstrate a facile synthesis of highly photostable silver nanoclusters in a polymer thin film using visible light photoreduction. Furthermore, the different stages of the nanocluster formation are investigated in detail using absorption and fluorescence spectroscopy, fluorescence microscopy, and atomic force microscopy. A cost-effective fabrication of photostable micron-sized fluorescent silver nanocluster barcode is demonstrated in silver-impregnated polymer films using a low-power continuous-wave laser diode. It is shown that a laser power of as low as 0.75 mW is enough to write fluorescent structures, corresponding to the specifications of a commercially available laser pointer. The as-formed nanocluster-containing microstructures can be useful in direct labeling applications such as authenticity marking and fluorescent labeling. PMID:27045598

  10. Sub-micron scale patterning of fluorescent silver nanoclusters using low-power laser

    NASA Astrophysics Data System (ADS)

    Kunwar, Puskal; Hassinen, Jukka; Bautista, Godofredo; Ras, Robin H. A.; Toivonen, Juha

    2016-04-01

    Noble metal nanoclusters are ultrasmall nanomaterials with tunable properties and huge application potential; however, retaining their enhanced functionality is difficult as they readily lose their properties without stabilization. Here, we demonstrate a facile synthesis of highly photostable silver nanoclusters in a polymer thin film using visible light photoreduction. Furthermore, the different stages of the nanocluster formation are investigated in detail using absorption and fluorescence spectroscopy, fluorescence microscopy, and atomic force microscopy. A cost-effective fabrication of photostable micron-sized fluorescent silver nanocluster barcode is demonstrated in silver-impregnated polymer films using a low-power continuous-wave laser diode. It is shown that a laser power of as low as 0.75 mW is enough to write fluorescent structures, corresponding to the specifications of a commercially available laser pointer. The as-formed nanocluster-containing microstructures can be useful in direct labeling applications such as authenticity marking and fluorescent labeling.

  11. Sub-micron scale patterning of fluorescent silver nanoclusters using low-power laser.

    PubMed

    Kunwar, Puskal; Hassinen, Jukka; Bautista, Godofredo; Ras, Robin H A; Toivonen, Juha

    2016-01-01

    Noble metal nanoclusters are ultrasmall nanomaterials with tunable properties and huge application potential; however, retaining their enhanced functionality is difficult as they readily lose their properties without stabilization. Here, we demonstrate a facile synthesis of highly photostable silver nanoclusters in a polymer thin film using visible light photoreduction. Furthermore, the different stages of the nanocluster formation are investigated in detail using absorption and fluorescence spectroscopy, fluorescence microscopy, and atomic force microscopy. A cost-effective fabrication of photostable micron-sized fluorescent silver nanocluster barcode is demonstrated in silver-impregnated polymer films using a low-power continuous-wave laser diode. It is shown that a laser power of as low as 0.75 mW is enough to write fluorescent structures, corresponding to the specifications of a commercially available laser pointer. The as-formed nanocluster-containing microstructures can be useful in direct labeling applications such as authenticity marking and fluorescent labeling. PMID:27045598

  12. Self-similar micron-size and nanosize drops of liquid generated by surface acoustic waves.

    PubMed

    Taller, Daniel; Go, David B; Chang, Hsueh-Chia

    2012-11-30

    A planar surface acoustic wave on a solid substrate and its radiated sound into a static liquid drop produce time-averaged, exponentially decaying acoustic and electric Maxwell pressures near the contact line. These localized contact-line pressures are shown to generate two sequences of hemispherical satellite droplets at the tens of microns and submicron scales, both obeying self-similar exponential scaling but with distinct exponents that correspond to viscous dissipation and field leakage length scales, respectively. The acoustic pressure becomes dominant when the film thickness exceeds (1/4π) of the surface acoustic wave wavelength and it affects the shape and stability of the mother drop. The Maxwell pressure of the nanodrops, which exceeds ten atmospheres, is sensitive to the contact angle. PMID:23368125

  13. Global Subducting Slab Entrainment of Oceanic Asthenosphere: Re-examination of Sub-Slab Shear-Wave Splitting Patterns

    NASA Astrophysics Data System (ADS)

    Song, T.; Liu, L.; Kawakatsu, H.

    2011-12-01

    Oceanic asthenosphere is characterized as a low seismic velocity, low viscosity, and strongly anisotropic channel separating from the oceanic lithosphere through a sharp shear wave velocity contrast. It has been a great challenge to reconcile all these observations and ultimately illuminate the fate of oceanic asthenosphere near convergent plate margins. Sub-slab shear wave splitting patterns are particularly useful to address the fate of oceanic asthenosphere since they are directly linked to deformation induced by the mantle flow beneath the subducting slab. To address slab entrainment of oceanic asthenosphere through shear wave splitting, it is important to recognize that oceanic asthenosphere is characterized by azimuthal anisotropy (1-3%) as well as strong P wave and S wave radial anisotropy (3-7%) for horizontally travelling P wave (VPH > VPV) and S wave (VSH > VSV), making it effectively an orthorhombic medium. Here we show that entrained asthenosphere predicts sub-slab SKS splitting pattern, where the fast splitting direction changes from predominantly trench-normal under shallow subduction zones to predominantly trench-parallel under relatively steep subduction zones. This result can be recognized by the 90 degrees shift in the polarization of the fast wave at about 20 degrees incident angle, where VSH equals to VSV forming a classical point singularity (Crampin, 1991). The thickness of the entrained asthenosphere is estimated to be on the order of 100 km, which predicts SKS splitting time varying from 0.5 seconds to 2 seconds. After briefly discussing improvement of the millefeuille model (Kawakatsu et al. 2009) of the asthenosphere upon this new constraint and long wave Backus averaging of orthorhombic solid and melt, we will illustrate that, in the range of observed trench migration speed, dynamic models of 2-D mantle convection with temperature-dependent viscosity do support thick subducting slab entrainment of asthenosphere under ranges of

  14. A scanning tunneling microscope capable of imaging specified micron-scale small samples

    NASA Astrophysics Data System (ADS)

    Tao, Wei; Cao, Yufei; Wang, Huafeng; Wang, Kaiyou; Lu, Qingyou

    2012-12-01

    We present a home-built scanning tunneling microscope (STM) which allows us to precisely position the tip on any specified small sample or sample feature of micron scale. The core structure is a stand-alone soft junction mechanical loop (SJML), in which a small piezoelectric tube scanner is mounted on a sliding piece and a "U"-like soft spring strip has its one end fixed to the sliding piece and its opposite end holding the tip pointing to the sample on the scanner. Here, the tip can be precisely aligned to a specified small sample of micron scale by adjusting the position of the spring-clamped sample on the scanner in the field of view of an optical microscope. The aligned SJML can be transferred to a piezoelectric inertial motor for coarse approach, during which the U-spring is pushed towards the sample, causing the tip to approach the pre-aligned small sample. We have successfully approached a hand cut tip that was made from 0.1 mm thin Pt/Ir wire to an isolated individual 32.5 × 32.5 μm2 graphite flake. Good atomic resolution images and high quality tunneling current spectra for that specified tiny flake are obtained in ambient conditions with high repeatability within one month showing high and long term stability of the new STM structure. In addition, frequency spectra of the tunneling current signals do not show outstanding tip mount related resonant frequency (low frequency), which further confirms the stability of the STM structure.

  15. Transition from slab stagnation to penetration beneath the northwestern Pacific and South America (Invited)

    NASA Astrophysics Data System (ADS)

    Fukao, Y.; Obayashi, M.

    2010-12-01

    Subducting slabs tend to once deflect horizontally in the transition zone as stagnant slabs and then to penetrate into the lower mantle across the 660-km discontinuity. Here we present the detailed tomographic images of transition from stagnant-slab mode to penetrating-slab mode, based on the global ISC travel time data to which regional network data and long-term array observation data including ocean bottom data are added. The targets are the subducted slabs beneath South America and the northwestern Pacific. In South America the transition occurs across the northeastward extension of the sharp bend of the Peru-Chili trench. The slab to the south of this extension is stagnant above the 660, and to the north it plunges into the lower mantle across the 660. The transition is sharp as if the originally flat slab in the northern part was rotated into the present configuration by hinge faulting along the extension. We suspect that this hinge faulting either triggered the northward propagation of or truncated the southward propagation of the plunging motion of the slab into the lower mantle. Along the Kurile arc, the slab is flattened above the 660 in the southwest, penetrating in the northeast, with a transitional feature in between. In southern Kurile the flattened part has a deepest bottom near the junction with the dipping part. Such an along-arc change of slab configuration is indicative of a process of transition from stagnant-slab mode to penetrating-slab mode: the flattened part and dipping part of the slab begin to sink into the lower mantle at their junction so that the horizontal part is progressively dragged to and is eventually united to the dipping part as a penetrating slab. Along the Izu-Bonin-Mariana (IBM) arc, the slab is flattened above the 660 in the north (Izu-Bonin) and is penetrating the 660 in the south (Mariana) leaving the horizontal part in the transition zone. In the Izu-Bonin the flattened part has a deepest bottom near the junction with

  16. A Systematic Study on the Formation of South American Flat-Slab Subduction

    NASA Astrophysics Data System (ADS)

    Hu, J.; Liu, L.

    2015-12-01

    The South American subduction zone is characterized by its along-strike variation from flat to steeply dipping slabs. Both formation mechanisms and geometry of flat slabs in South America remain unclear. To evaluate the relative contribution of different mechanisms to flat slab formation, we simulate the post-100 Ma subduction history below South America using 3-D geodynamic models by progressively incorporating key tectonic features including seafloor ages, buoyant oceanic crusts, thickened oceanic plateaus (i.e. the Inca plateau, Nazca Ridge and Juan Fernandez Ridge), continental cratons, as well as deformable trench profiles according to recent geological reconstructions. With a uniform seafloor age of 30 Ma (i.e., the spatial average of the Nazca Plate since 20 Ma), we get steep (>30°, measured at 200 km depth) subduction everywhere except at 25°S -35°S, where the slab dip is affected by earlier subduction at depth. With the actual reconstructed seafloor ages, the slab dip angle is systematically reduced with an average of ~25°; the long-wavelength lateral variation of slab dip angle that resembles the observation results from the spatial variation of slab buoyancy and strength. The addition of a uniformly thick overriding plate, with enhanced dynamic suction in the mantle wedge, further reduces the slab dip angle (<23°) along the entire trench, where the young slab portions are affected more than the old one. Realization of the 3D geometry of cratonic roots enhances along-trench variation of suction force, which results in an additional reduction of slab dip (<20°), especially next to the cratons. While dynamic suction from the overriding plate reduces the long-wavelength slab dip angle, subducting oceanic plateau and aseismic ridges lead to more localized flat-slabs (as low as 15°) as observed. The subduction of aseismic ridges also generates tears within the flat slabs, due to the accumulation of strain at the down-dip end of the ridge. These slab

  17. Bench-Scale Testing of the Micronized Magnetite Process

    SciTech Connect

    Edward R. Torak; Peter J. Suardini

    1997-11-01

    A recent emphasis of the Department of Energy's (DOE's), Coal Preparation Program has been the development of high-efficiency technologies that offer near-term, low-cost improvements in the ability of coal preparation plants to address problems associated with coal fines. In 1992, three cost-shared contracts were awarded to industry, under the first High-Efficiency Preparation (HEP I) solicitation. All three projects involved bench-scale testing of various emerging technologies, at the Federal Energy Technology Center*s (FETC*s), Process Research Facility (PRF). The first HEP I project, completed in mid-1993, was conducted by Process Technology, Inc., with the objective of developing a computerized, on-line system for monitoring and controlling the operation of a column flotation circuit. The second HEP I project, completed in mid-1994, was conducted by a team led by Virginia Polytechnic Institute to test the Mozely Multi-Gravity Separator in combination with the Microcel Flotation Column, for improved removal of mineral matter and pyritic sulfur from fine coal. The last HEP I project, of which the findings are contained in this report, was conducted by Custom Coals Corporation to evaluate and advance a micronized-magnetite-based, fine-coal cycloning technology. The micronized-magnetite coal cleaning technology, also know as the Micro-Mag process, is based on widely used conventional dense-medium cyclone applications, in that it utilizes a finely ground magnetite/water suspension as a separating medium for cleaning fine coal, by density, in a cyclone. However, the micronized-magnetite cleaning technology differs from conventional systems in several ways: ! It utilizes significantly finer magnetite (about 5 to 10 micron mean particle size), as compared to normal mean particle sizes of 20 microns. ! It can effectively beneficiate coal particles down to 500M in size, as compared to the most advanced, existing conventional systems that are limited to a particle bottom

  18. Too much slab waving in South America? Wet plumes as an alternative to flat slab steepening as the cause of back arc large volcanic provinces

    NASA Astrophysics Data System (ADS)

    Booker, J. R.; Burd, A. I.

    2013-12-01

    A widely held view is that the Nazca Slab under western S. America acts like a tattered flag waving in the wind: It is segmented and the dip angle of segments flap up and down with time. There are presently two flat segments - one under Peru and the other, the "Pampean" flat slab (centered around 31S) under central Chile and Argentina. Both are correlated with subduction of buoyant crust of oceanic aseismic ridges, complete cessation of Andean arc volcanism and very thick crust. It has been argued that the waxing and waning of flat subduction is responsible for much of the time variations in tectonics and volcanism up to 800 km east of the S. American coast for at least 100 MA. For instance, the back arc Payenia igneous plateau (35-38S) and the Somuncura igneous plateau (40.5-43S) are both thought to follow from the steepening of flat slabs at about 2 and 27 MA. Each flat slab existed for more than 5 MA. However, the case for the existence of these flat slabs rests heavily on volcanism with "arc signature" hundreds of km east of the modern volcanic arc at a time when an asthenospheric wedge would be in its final stages of being squeezed out of the space between the slab and the lithosphere. Arc signature can be summarized as the geochemical consequence of mantle melting in the presence of water. If there is a source of water in the mantle other than a shallow slab, the strongest argument for a flat slab dissolves. We have found two electrically conductive plumes rising from below 350 km near the top of the Mantle Transition Zone (MTZ). One passes through a window in the Pampean flat slab but does not penetrate the lithosphere. The other rises under Payenia. The maximum resistivity at the core of these plumes is less than 10 Ohm-m. Partial melt can explain such low resistivity, but will not be buoyant and rise from below 350 km. We propose that the low resistivity is more likely due to water and that we are seeing "wet plumes" that have been proposed to explain

  19. Pressure drop and heat transfer characteristics of boiling water in sub-hundred micron channel

    SciTech Connect

    Bhide, R.R.; Singh, S.G.; Sridharan, Arunkumar; Duttagupta, S.P.; Agrawal, Amit

    2009-09-15

    The current work focuses on the pressure drop, heat transfer and stability in two phase flow in microchannels with hydraulic diameter of less than one hundred microns. Experiments were conducted in smooth microchannels of hydraulic diameter of 45, 65 {mu}m, and a rough microchannel of hydraulic diameter of 70 {mu}m, with deionised water as the working fluid. The local saturation pressure and temperature vary substantially over the length of the channel. In order to correctly predict the local saturation temperature and subsequently the heat transfer characteristics, numerical techniques have been used in conjunction with the conventional two phase pressure drop models. The Lockhart-Martinelli (liquid-laminar, vapour-laminar) model is found to predict the two phase pressure drop data within 20%. The instability in two phase flow is quantified; it is found that microchannels of smaller hydraulic diameter have lesser instabilities as compared to their larger counterparts. The experiments also suggest that surface characteristics strongly affect flow stability in the two phase flow regime. The effect of hydraulic diameter and surface characteristics on the flow characteristics and stability in two phase flow is seldom reported, and is of considerable practical relevance. (author)

  20. Cenozoic tectonics of western North America controlled by evolving width of Farallon slab.

    PubMed

    Schellart, W P; Stegman, D R; Farrington, R J; Freeman, J; Moresi, L

    2010-07-16

    Subduction of oceanic lithosphere occurs through two modes: subducting plate motion and trench migration. Using a global subduction zone data set and three-dimensional numerical subduction models, we show that slab width (W) controls these modes and the partitioning of subduction between them. Subducting plate velocity scales with W(2/3), whereas trench velocity scales with 1/W. These findings explain the Cenozoic slowdown of the Farallon plate and the decrease in subduction partitioning by its decreasing slab width. The change from Sevier-Laramide orogenesis to Basin and Range extension in North America is also explained by slab width; shortening occurred during wide-slab subduction and overriding-plate-driven trench retreat, whereas extension occurred during intermediate to narrow-slab subduction and slab-driven trench retreat. PMID:20647465

  1. Cenozoic tectonics of western North America controlled by evolving width of Farallon slab.

    PubMed

    Schellart, W P; Stegman, D R; Farrington, R J; Freeman, J; Moresi, L

    2010-07-16

    Subduction of oceanic lithosphere occurs through two modes: subducting plate motion and trench migration. Using a global subduction zone data set and three-dimensional numerical subduction models, we show that slab width (W) controls these modes and the partitioning of subduction between them. Subducting plate velocity scales with W(2/3), whereas trench velocity scales with 1/W. These findings explain the Cenozoic slowdown of the Farallon plate and the decrease in subduction partitioning by its decreasing slab width. The change from Sevier-Laramide orogenesis to Basin and Range extension in North America is also explained by slab width; shortening occurred during wide-slab subduction and overriding-plate-driven trench retreat, whereas extension occurred during intermediate to narrow-slab subduction and slab-driven trench retreat.

  2. Slab Deformation in the Mantle Transition Zone: The Effect of Plate Age and Strength Evolution

    NASA Astrophysics Data System (ADS)

    Goes, S. D. B.; Garel, F.; Davies, R.; Davies, J. H.; Kramer, S. C.; Wilson, C. R.

    2014-12-01

    The deformation encountered by subducted tectonic plates at the base of the upper mantle influences Earth's thermal, chemical, and tectonic evolution. Yet the mechanisms responsible for the wide range of imaged slab morphologies, either stagnating in the transition zone or penetrating into the lower mantle, remain debated. We use 2-D thermo-mechanical models of a two-plate subduction system, modeled with the finite-element, adaptive-mesh code Fluidity. We implement a temperature- and stress-dependent rheology, and viscosity increases 30-fold from upper to lower mantle. Trench position evolves freely in response to plate dynamics. Such an approach self-consistently captures feedbacks between temperature, density, flow, strength and deformation. Our results indicate that key controls on subduction dynamics and slab morphology are: (i) the evolution of slab strength; and (ii) the slab's ability to induce trench motion. We build a regime diagram that distinguishes four subduction styles: (1) a "vertical folding" mode with stationary trench; (2) young slabs that are "horizontally deflected" along the 660-km deep viscosity jump ; (3) an inclined slab morphology, resulting from strong trench retreat (old slabs and thinner overriding plates); and (4) a two-stage mode, displaying bent (rolled-over) slabs at the end of upper-mantle descent, that subsequently unbend and achieve inclined morphologies, with late trench retreat (strong overriding plates). We find that the interplay between trench motion and slab deformation at depth dictates the subduction style, both being controlled by slab strength. We show that all seismically observed slab morphologies in the transition zone can arise just by changing the subducting-plate ages. However, to understand present-day slab morphologies, we have to analyse subduction history rather than just current age at the trench.

  3. Arc Interrupted: The birth, life, and death of the Peruvian flat slab

    NASA Astrophysics Data System (ADS)

    Wagner, Lara; Knezevic Antonijevic, Sanja; Kumar, Abhash; Beck, Susan; Long, Maureen; Zandt, George; Tavera, Hernando; Minaya, Estela

    2016-04-01

    The Peruvian flat slab is a unique natural laboratory for investigating the temporal evolution of flat slab subduction and its associated thermal, tectonic, and seismic implications. This is because the flat slab has been hypothesized to have first formed further north (at approximately the latitude of Lima, Peru), but broadened to the south over the past 11 Ma. This means that areas further to the north represent an older, more evolved flat slab setting, whereas the southernmost edge of the modern flat slab reflects conditions experienced by a newly formed flat slab. Here we present findings from a suite of recent temporary broadband seismic deployments that spanned this entire region. Results from intermediate depth earthquake locations, surface wave tomography (ballistic and ambient Rayleigh wave), and Rayleigh wave anisotropy all indicate that the flat slab did indeed first form further to the north and broadened to the south, along with the southward migration of the Nazca ridge. Subsequently, a trench-parallel tear developed in the older portions of the flat slab north of the ridge, resulting in a resumption of normal subduction geometry where once a flat slab had existed. This tear allows for an interchange of mantle material from beneath the slab to the south to above the slab to the north. This mantle flow has significant thermal implications, both beneath the flat slab and in the lower continental crust located above the relatively newly formed tear. Our results provide unique constraints on the thermal and tectonic evolution of this unusual subduction geometry that may help us to understand better subduction zone processes everywhere.

  4. Surface waves on a grounded dielectric slab covered by a resistive sheet

    NASA Technical Reports Server (NTRS)

    Shively, David

    1993-01-01

    This paper examines surface wave propagation in a grounded dielectric slab covered with a resistive sheet. Transcendental equations are derived for each polarization and are solved using iterative techniques. Attention and phase velocity are shown for a representative geometry. The results are applicable to both a grounded slab covered with a resistive sheet and an ungrounded slab covered on each side with a resistive sheet.

  5. The dynamics of double slab subduction from numerical and semi-analytic models

    NASA Astrophysics Data System (ADS)

    Holt, A.; Royden, L.; Becker, T. W.

    2015-12-01

    Regional interactions between multiple subducting slabs have been proposed to explain enigmatic slab kinematics in a number of subduction zones, a pertinent example being the rapid pre-collisional plate convergence of India and Eurasia. However, dynamically consistent 3-D numerical models of double subduction have yet to be explored, and so the physics of such double slab systems remain poorly understood. Here we build on the comparison of a fully numerical finite element model (CitcomCU) and a time-dependent semi-analytic subduction models (FAST) presented for single subduction systems (Royden et. al., 2015 AGU Fall Abstract) to explore how subducting slab kinematics, particularly trench and plate motions, can be affected by the presence of an additional slab, with all of the possible slab dip direction permutations. A second subducting slab gives rise to a more complex dynamic pressure and mantle flow fields, and an additional slab pull force that is transmitted across the subduction zone interface. While the general relationships among plate velocity, trench velocity, asthenospheric pressure drop, and plate coupling modes are similar to those observed for the single slab case, we find that multiple subducting slabs can interact with each other and indeed induce slab kinematics that deviate significantly from those observed for the equivalent single slab models. References Jagoutz, O., Royden, L. H., Holt, A. F. & Becker, T. W., 2015, Nature Geo., 8, 10.1038/NGEO2418. Moresi, L. N. & Gurnis, M., 1996, Earth Planet. Sci. Lett., 138, 15-28. Royden, L. H. & Husson, L., 2006, Geophys. J. Int. 167, 881-905. Zhong, S., 2006, J. Geophys. Res., 111, doi: 10.1029/2005JB003972.

  6. Slab dehydration recorded in subducted serpentine sea-mount

    NASA Astrophysics Data System (ADS)

    Okamoto, K.; Fukumura, S.; Ishimori, C.; Jung, H.

    2014-12-01

    It has been considered that there is a correlation between the double seismic zones and metamorphic dehydration reaction in deep slab. The lower seismic plane of the double seismic zone is considered to be located on the 600 oC isotherm in the subducting lithosphere. Antigorite terminal reaction is highly temperature sensitive around 600 oC. Therefore it has been proposed that the oceanic lithosphere was hydrated forming serpentine prior to subduction, then serpentine was decomposed to release fluid causing dehydration embrittlement in the slab. In order to unravel relation between dehydration and seismic deformation, we have investigated dehydration process of natural metamorphic rocks recording very cold geothermal history in the crust and lithosphere in the slab. Metamorphic olivine after antigorite has been described in Italian Alps and also from the Mt. Shiraga, Japan [1]. However, the olivine was formed with talc and fluid by antigorite breakdown reaction in pressures lower than 1.5 GPa. Spinifex olivine with opx in the Cerro del Almirez [2], is the product at pressures (P > 1.5 GPa) relevant to the lower seismic plane beneath Northeast Japan. It clearly indicates the presence of large amount of water facilitate crystallization of elongated olivine with opx. It is also supported by LPO pattern of olivines determined by EBSD. Fine-grained olivine-rich samples shows that Type-C fabric pattern is dominant, suggesting deformation under water-rich condition [3]. With metamorphic olivines, chlorite was also recrystallized, suggesting that water would be transported farther down to deep. The estimated dehydration reaction has a negative P-T slope at pressures higher than 1.5 GPa. The reaction is volume reducing reaction and the olivine-opx spinifex texture was formed under volume reducing reaction. In the warm slab beneath SW Japan, the reaction has a positive slope in P-T space and forms olivine+talc+fluid. From microstrucral and petrological analysis of the

  7. Wave propagation through a random medium - The random slab problem

    NASA Technical Reports Server (NTRS)

    Acquista, C.

    1978-01-01

    The first-order smoothing approximation yields integral equations for the mean and the two-point correlation function of a wave in a random medium. A method is presented for the approximate solution of these equations that combines features of the eiconal approximation and of the Born expansion. This method is applied to the problem of reflection and transmission of a plane wave by a slab of a random medium. Both the mean wave and the covariance are calculated to determine the reflected and transmitted amplitudes and intensities.

  8. Diffraction and electron energy loss to plasmons in silicon slabs

    NASA Astrophysics Data System (ADS)

    Levine, Zachary H.

    2008-03-01

    Dynamical diffraction patterns were calculated for 25nm slabs of silicon with [001], [111], and [110] faces for a 120keV electron beam. The calculation used the mixed dynamical form factor in the dielectric formulation. Dielectric matrices with wave vector and frequency dependence were calculated within the local density approximation using the random phase approximation. The energy losses, 10-25eV , span the plasmon peak. Near the zone axes, the results show the preservation of elastic contrast and both excess and deficit Kikuchi lines.

  9. WORKERS FABRICATE ROOF SLABS FOR MTR BUILDING AT THE CONSTRUCTION ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    WORKERS FABRICATE ROOF SLABS FOR MTR BUILDING AT THE CONSTRUCTION SITE. FORMS WERE MADE OF STEEL. AFTER AN INCH OF CONCRETE HAD BEEN POURED IN THE FORM, A MAT OF REINFORCING STEEL WAS PLACED ON IT. THE REMAINDER OF THE FORM WAS FILLED, AND THE CONCRETE WAS VIBRATED, STRUCK, AND TROWELED. GROOVES AT CORNER WILL HAVE 1/4 INCH RODS WELDED INTO THE EYE OF THE STEEL MAT FOR GROUNDING. INL NEGATIVE NO. 578. Unknown Photographer, 9/1/1950 - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

  10. Radiative flux emitted by a burning PMMA slab

    NASA Astrophysics Data System (ADS)

    Parent, G.; Acem, Z.; Collin, A.; Berfroi, R.; Boulet, P.; Pizzo, Y.; Mindykowski, P.; Kaiss, A.; Porterie, B.

    2012-11-01

    The degradation of a PMMA sample has been studied based on experimental results obtained for the radiation emission by a burning slab. Observations of the infrared emission perpendicular to the plate, in the range where the optically thin flame is weakly emitting, indicate a plate temperature close to 680 K which is an indication on the surface temperature during the degradation process. Observations from the side allow a flame characterization without the plate emission superimposition. This is a promising way for evaluating data regarding the flame characteristics: temperature, gaz concentration and soot volumetric fraction.

  11. Surface polaritons of a metal-insulator-metal curved slab

    NASA Astrophysics Data System (ADS)

    Moradi, Afshin

    2016-09-01

    The properties of s- and p-polarized surface polariton modes propagating circumferentially around a portion of a cylindrical metal-insulator-metal structure are studied, theoretically. By using the Maxwell equations in conjunction with the Drude model for the dielectric function of the metals and applying the appropriate boundary conditions, the dispersion relations of surface waves for two types of modes, are derived and numerically solved. The effects of the slab curvature and insulator thickness on the propagation of electromagnetic modes are investigated. The differences of the s- and p-polarized surface modes are also shown.

  12. Photon Counting Detectors for the 1.0 - 2.0 Micron Wavelength Range

    NASA Technical Reports Server (NTRS)

    Krainak, Michael A.

    2004-01-01

    We describe results on the development of greater than 200 micron diameter, single-element photon-counting detectors for the 1-2 micron wavelength range. The technical goals include quantum efficiency in the range 10-70%; detector diameter greater than 200 microns; dark count rate below 100 kilo counts-per-second (cps), and maximum count rate above 10 Mcps.

  13. Evaluation of the possibility to use thick slabs of reconstructed outer breast tomosynthesis slice images

    NASA Astrophysics Data System (ADS)

    Petersson, Hannie; Dustler, Magnus; Tingberg, Anders; Timberg, Pontus

    2016-03-01

    The large image volumes in breast tomosynthesis (BT) have led to large amounts of data and a heavy workload for breast radiologists. The number of slice images can be decreased by combining adjacent image planes (slabbing) but the decrease in depth resolution can considerably affect the detection of lesions. The aim of this work was to assess if thicker slabbing of the outer slice images (where lesions seldom are present) could be a viable alternative in order to reduce the number of slice images in BT image volumes. The suggested slabbing (an image volume with thick outer slabs and thin slices between) were evaluated in two steps. Firstly, a survey of the depth of 65 cancer lesions within the breast was performed to estimate how many lesions would be affected by outer slabs of different thicknesses. Secondly, a selection of 24 lesions was reconstructed with 2, 6 and 10 mm slab thickness to evaluate how the appearance of lesions located in the thicker slabs would be affected. The results show that few malignant breast lesions are located at a depth less than 10 mm from the surface (especially for breast thicknesses of 50 mm and above). Reconstruction of BT volumes with 6 mm slab thickness yields an image quality that is sufficient for lesion detection for a majority of the investigated cases. Together, this indicates that thicker slabbing of the outer slice images is a promising option in order to reduce the number of slice images in BT image volumes.

  14. Free subduction dynamics of a thermo-mechanical slab with non-linear rheology

    NASA Astrophysics Data System (ADS)

    Holt, A. F.; Becker, T. W.; Buffett, B. A.

    2012-12-01

    We investigate the dynamic controls on single plate subduction in a visco-plastic rheology using a 2D set up of the finite element code, CitcomCU. In contrast to previous studies, which focus largely on compositional slabs (e.g. Enns et al., 2005), we focus on thermal slabs (i.e. include effects of thermal diffusion). We analyse slabs that develop from plates both with uniform initial thicknesses and half-space cooling plates with thicknesses that vary with sqrt(x). A pseudo-plastic rheology facilitates the decoupling of the slab from the free slip upper surface. It is found that thermal slabs have lower strain rates in the bending region, due to the cooling upper boundary temperature condition, and so lower yield stresses are required to decouple thermal slabs than compositional slabs. As in previous work, it is found that stronger, thicker slabs promote trench advance (after the initial advancing phase). Both boundary conditions (basal and side) and incorporating a plate with half-space cooling thickness variations are shown to have a significant effect on slab dynamics, particularly on the maximum amount of trench retreat. Subsequently, models with non-Newtonian, stress-dependent rheologies are compared to Newtonian models with equivalent slab-mantle viscosity contrasts. Models with power law exponents of both 3, corresponding to dislocation creep, and a large exponent of 14, corresponding to near-pure plasticity (see Buffett and Becker, 2012), are analysed. It is found that, particularly for the n=14 case, the inclusion of a stress dependent rheology dramatically reduces the timescales of both trench migration and slab descent, while modifying slab morphology to a much lesser degree. Using a temperature threshold to confine the non-Newtonian rheology to within the slab prevents weakening in the surrounding mantle and so increases the subduction timescales to values that lie between the equivalent Newtonian and non-Newtonian (non-confined) timescales. While all

  15. Abnormal seismological and magmatic processes controlled by the tearing South American flat slabs

    NASA Astrophysics Data System (ADS)

    Hu, Jiashun; Liu, Lijun

    2016-09-01

    The influence of flat slab subduction on the formation of intra-slab earthquakes, volcanic activities and mantle seismic velocity anomalies remains unclear. We attempt to better understand these processes by simulating the two flat slabs in Peru and Chile using data-orientated geodynamic models. Our results successfully reproduce the observed flat slabs as mainly due to two subducting aseismic ridges. In contrast to the traditional view of flat-slab subduction, we find that these slabs are internally torn, as is due to the 3D nature of the subducting buoyancy features. This broken slab configuration, confirmed by regional tomography, naturally explains the abnormal distribution of and stress regimes associated with the intermediate-depth earthquakes. We further show that the slab tearing process could also better explain the formation of adakitic and ore-forming magmatism, the evolution of the magmatic arc, and the enigmatic mantle seismic structures beneath these regions. We propose that slab tearing may represent a common result of buoyancy feature subduction and that the resulting mantle processes could affect the long-term geodynamic evolution of continents.

  16. Analysis of surface wave propagation in a grounded dielectric slab covered by a resistive sheet

    NASA Technical Reports Server (NTRS)

    Shively, David G.

    1992-01-01

    Both parallel and perpendicular polarized surface waves are known to propagate on lossless and lossy grounded dielectric slabs. Surface wave propagation on a grounded dielectric slab covered with a resistive sheet is considered. Both parallel and perpendicular polarizations are examined. Transcendental equations are derived for each polarization and are solved using iterative techniques. Attenuation and phase velocity are shown for representative geometries. The results are applicable to both a grounded slab with a resistive sheet and an ungrounded slab covered on each side with a resistive sheet.

  17. Meteorological variables to aid forecasting deep slab avalanches on persistent weak layers

    USGS Publications Warehouse

    Marienthal, Alex; Hendrikx, Jordy; Birkeland, Karl; Irvine, Kathryn M.

    2015-01-01

    Deep slab avalanches are particularly challenging to forecast. These avalanches are difficult to trigger, yet when they release they tend to propagate far and can result in large and destructive avalanches. We utilized a 44-year record of avalanche control and meteorological data from Bridger Bowl ski area in southwest Montana to test the usefulness of meteorological variables for predicting seasons and days with deep slab avalanches. We defined deep slab avalanches as those that failed on persistent weak layers deeper than 0.9 m, and that occurred after February 1st. Previous studies often used meteorological variables from days prior to avalanches, but we also considered meteorological variables over the early months of the season. We used classification trees and random forests for our analyses. Our results showed seasons with either dry or wet deep slabs on persistent weak layers typically had less precipitation from November through January than seasons without deep slabs on persistent weak layers. Days with deep slab avalanches on persistent weak layers often had warmer minimum 24-hour air temperatures, and more precipitation over the prior seven days, than days without deep slabs on persistent weak layers. Days with deep wet slab avalanches on persistent weak layers were typically preceded by three days of above freezing air temperatures. Seasonal and daily meteorological variables were found useful to aid forecasting dry and wet deep slab avalanches on persistent weak layers, and should be used in combination with continuous observation of the snowpack and avalanche activity.

  18. Leaky unstable modes and electromagnetic radiation amplification by an anisotropic plasma slab

    SciTech Connect

    Vagin, K. Yu. Uryupin, S. A.

    2015-09-15

    The interaction between electromagnetic radiation and a photoionized plasma slab with an anisotropic electron velocity distribution is studied. It is shown that the fields of leaky modes are amplified due to the development of aperiodic instability in the slab, which leads to an increase in both the reflected and transmitted fields. The transmitted field can significantly increase only if the slab thickness does not exceed the ratio of the speed of light to the electron plasma frequency, whereas there is no upper bound on the slab thickness for the reflected signal to be amplified.

  19. High energy efficient solid state laser sources. [slab geometry laser sources

    NASA Technical Reports Server (NTRS)

    Byer, R. L.

    1983-01-01

    Slab glass performance studies demonstate 18 J of output at 2 Hz with 2.3% wall plug efficiency. The goal is to achieve 10 J per pulse at 10 Hz and 3% wall plug efficiency during the next annual period. The slab concept was extended to Nd:YAG and to Nd:GGG. To date over 80 W of CW output power at 2% efficiency was generated in slab Nd:YAG. A multiplexed slab Nd:YAG pre-amplifier was invented and a Nd:YAG oscillator was demonstrated with 100kHz linewidth for eventual use in wind velocity measurements.

  20. Structured mass density slab as a waveguide of fast magnetoacoustic waves

    NASA Astrophysics Data System (ADS)

    Jelínek, P.; Karlický, M.

    Coronal loops are waveguides for magnetohydrodynamic (MHD) waves. These loops are expected to be structured. Therefore, in the present paper, we numerically studied the propagation of the fast MHD waves in the structured density slab (composed from a broad density slab with one axisymmetric narrow sub-slab superposed), and analysed the wave signals. Then, this structured slab was divided into its components, i.e., to simple broad and narrow slabs and the same analysis was made. We compared results of both these cases. For the calculations we adopted a two-dimensional (2D) magnetohydrodynamic (MHD) model, in which we solved a full set of ideal time-dependent MHD equations using the FLASH code, applying the adaptive mesh refinement (AMR) method. To initiate the fast sausage magnetoacoustic waves, we used axisymmetric Gaussian velocity perturbation. Wave signals were detected in different locations along the slab and as a diagnostic tool of these waves, the wavelet analysis method has been used. We found that for the structured density slab with sufficiently sharp boundaries, i.e., for good quality waveguides (without an energy leakage), the guided waves in the structured slab behave similarly as in its separated (simple slab) components.

  1. A Comparative Study of Strength of Two-Way Rectangular Slabs with and without Openings

    NASA Astrophysics Data System (ADS)

    Ravindra, M.; Rakesh, V.; Rambabu, K.

    2016-09-01

    The present work uses yield-line theory to find the strength of uniformly loaded rectangular reinforced concrete slabs with and without rectangular openings. Five positions of openings are considered, i.e. the slab centre, the slab corner, the centre of a short side, the centre of a long side and the opening eccentric to the slab centre. All possible admissible yield line patterns are considered for all given configurations of the slab subjected to uniformly distributed load keeping in view the basic principles of yield line theory. The ratios of the corresponding lengths of the sides of the opening and the slab are different and sizes of opening up to 0.4× the length of the slab sides are considered. Symmetric edge conditions like continuous slab, simply supported, two long sides continuous and two short sides continuous are considered for various sizes of openings in order to plot the design charts for isotropic reinforcement coefficients only. Affine transformation is also performed for slab with openings.

  2. Displacement-based seismic design of flat slab-shear wall buildings

    NASA Astrophysics Data System (ADS)

    Sen, Subhajit; Singh, Yogendra

    2016-06-01

    Flat slab system is becoming widely popular for multistory buildings due to its several advantages. However, the performance of flat slab buildings under earthquake loading is unsatisfactory due to their vulnerability to punching shear failure. Several national design codes provide guidelines for designing flat slab system under gravity load only. Nevertheless, flat slab buildings are also being constructed in high seismicity regions. In this paper, performance of flat slab buildings of various heights, designed for gravity load alone according to code, is evaluated under earthquake loading as per ASCE/SEI 41 methodology. Continuity of slab bottom reinforcement through column cage improves the performance of flat slab buildings to some extent, but it is observed that these flat slab systems are not adequate in high seismicity areas and need additional primary lateral load resisting systems such as shear walls. A displacement-based method is proposed to proportion shear walls as primary lateral load resisting elements to ensure satisfactory performance. The methodology is validated using design examples of flat slab buildings with various heights.

  3. Optical pulling force on a particle near the surface of a dielectric slab waveguide

    NASA Astrophysics Data System (ADS)

    Paul, Nayan Kumar; Kemp, Brandon A.

    2016-01-01

    Optical forces on a Rayleigh particle near the surface of a dielectric slab waveguide are considered. A light wave of the lowest-order TE0 mode is used to excite the particle. The transverse and longitudinal forces acting on the particle are studied. The particle is always trapped near the surface of the slab, where the electric field intensity is high. The particle can be pushed away from or pulled toward the light source along the surface of the slab by tuning the frequency around a switching frequency. This phenomenon switches between scattering and gradient forces near the switching frequency of the dielectric slab waveguide.

  4. Calculation and comparison of thermal effect in laser diode pumped slab lasers with different pumping structures

    NASA Astrophysics Data System (ADS)

    Huang, Feng; Jiang, Nan; Wang, Yuefeng; Dong, Wei; Niu, Yanxiong

    2008-03-01

    Laser diode (LD) pumped slab laser, as an important high average power solid-state laser, is a promising laser source in military and industrial fields. The different laser diode pumping structures lead to different thermal effect in the slab gain medium. The thermal and stress analysis of slab laser with different pumping structure are performed by finite element analysis (FEA) with the software program ANSYS. The calculation results show that the face pumped and cooled laser results in a near one-dimension temperature distribution and eliminates thermal stress induced depolarization. But the structure is low pump efficiency due to the small thickness of slabs and the requirement to cool and pump through the same faces. End-pumped slab laser is high pump efficiency and excellent mode match, but its pumping arrangement is fairly complicated. The edge-pumped face-cooling slab laser's pump efficiency is better than face-pumping, and its pumping structure is simpler than end-pumped laser, but the tensile stress on surfaces may initiate failure of the gain medium so it is important to design so that the stress is well below the stress fracture limit. The comparison of the thermal effects with different pumping structure shows that, the edge-pumped slab laser has engineering advantages in high power slab laser's application. Furthermore, the end-pumped slab laser tends to get the best beam quality, so it is fit for the application which has a special requirement on laser beam quality.

  5. The micron stroke hypothesis of Alzheimer's disease and dementia.

    PubMed

    Orehek, Allen J

    2012-05-01

    Alzheimer's disease as currently described in the medical literature is often more a description of dementia rather than a specific disease. In over a century of scientific work there has been no proven theory as to the precise pathogenesis of Alzheimer's disease and dementia. As there is no efficient treatment for patients with Alzheimer's disease, prevention or attenuation of the disease is of substantial value. An intricate collection of hypotheses, studies, research, and experience has made it complicated for one to completely understand this disease. The purpose of this hypothesis is to illustrate new concepts and work to link those concepts to the present understanding of an obscure disease. The search for a single unifying hypothesis on the etiology of Alzheimer's disease has been elusive. Many hypotheses associated to Alzheimer's disease have not survived their testing to become theory. Suggested here is that the elusive nature of etiology of dementia is not from one cause, but rather the causes are numerous. Medical terminology used freely for decades is rarely evaluated in the light of a new hypothesis. At the foundation of this work is the suggestion of a new medical term: Micron Strokes. The Micron Stroke Hypothesis of Alzheimer's Disease and Dementia include primary and secondary factors. The primary factors can be briefly described as baseline brain tissue, atrial fibrillation, hypercoaguable state, LDL, carotid artery stenosis, tobacco exposure, hypertension diabetes mellitus, and the presence of systemic inflammation. Dozens of secondary factors contribute to the development of dementia. Most dementia is caused by nine primary categories of factors as they interact to cause micron strokes to the brain.

  6. A High Energy 2-microns Laser for Multiple Lidar Applications

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Singh, Upendra N.; Barnes, James C.; Barnes, Norman P.; Petros, Mulugeta

    2000-01-01

    Solid-state 2-microns laser has been receiving considerable interest because of its eye-safe property and efficient diode pump operation, It has potential for multiple lidar applications to detect water vapor. carbon dioxide and winds. In this paper, we describe a 2-microns double pulsed Ho:Tm:YLF laser and end-pumped amplifier system. A comprehensive theoretical model has been developed to aid the design and optimization of the laser performance. In a single Q-switched pulse operation the residual energy stored in the Tm atoms will be wasted. However, in a double pulses operation mode, the residual energy stored in the Tm atoms will repopulate the Ho atoms that were depleted by the extraction of the first Q-switched pulse. Thus. the Tin sensitized Ho:YLF laser provides a unique advantage in applications that require double pulse operation, such as Differential Absorption Lidar (DIAL). A total output energy of 146 mJ per pulse pair under Q-switch operation is achieved with as high as 4.8% optical to optical efficiency. Compared to a single pulse laser, 70% higher laser efficiency is realized. To obtain high energy while maintaining the high beam quality, a master-oscillator-power-amplifier 2-microns system is designed. We developed an end-pumped Ho:Tm:YLF disk amplifier. This amplifier uses two diode arrays as pump source. A non-imaging lens duct is used to couple the radiation from the laser diode arrays to the laser disk. Preliminary result shows that the efficiency of this laser can be as high as 3%, a factor of three increases over side-pump configuration. This high energy, highly efficient and high beam quality laser is a promising candidate for use in an efficient, multiple lidar applications.

  7. The brightest high-latitude 12-micron IRAS sources

    NASA Technical Reports Server (NTRS)

    Hacking, P.; Beichman, C.; Chester, T.; Neugebauer, G.; Emerson, J.

    1985-01-01

    The Infrared Astronomical Satellite (IRAS) Point Source catalog was searched for sources brighter than 28 Jy (0 mag) at 12 microns with absolute galactic latitude greater than 30 deg excluding the Large Magellanic Cloud. The search resulted in 269 sources, two of which are the galaxies NGC 1068 and M82. The remaining 267 sources are identified with, or have infrared color indices consistent with late-type stars some of which show evidence of circumstellar dust shells. Seven sources are previously uncataloged stars. K and M stars without circumstellar dust shells, M stars with circumstellar dust shells, and carbon stars occupy well-defined regions of infrared color-color diagrams.

  8. A Two Micron Coherent Differential Absorption Lidar Development

    NASA Technical Reports Server (NTRS)

    Yu, Jirong; Petros, Mulugeta; Chen, Songsheng; Bai, Yingxin; Petzar, Paul J.; Trieu, Bo C.; Koch, Grady J.; Beyon, Jeffrey Y.; VanValkenburg, Randal L.; Kavaya, Michael J.; Singh, Upendra N.

    2010-01-01

    A pulsed, 2-micron coherent Differential Absorption Lidar (DIAL)/Integrated Path Differential Absorption (IPDA) transceiver, developed under the Laser Risk Reduction Program (LRRP) at NASA, is integrated into a fully functional lidar instrument. This instrument measures atmospheric CO2 profiles (by DIAL) from a ground platform. It allows the investigators to pursue subsequent in science-driven deployments, and provides a unique tool for Active Sensing of CO2 Emissions over Night, Days, and Seasons (ASCENDS) validation that was strongly advocated in the recent ASCENDS Workshop. Keywords: Differential Absorption Lidar, Near Infrared Laser,

  9. Extended 20 micron emission from the center of NGC 1068

    NASA Technical Reports Server (NTRS)

    Telesco, C. M.; Becklin, E. E.; Wynn-Williams, C. G.

    1980-01-01

    Multiaperture photometry of the Seyfert galaxy NGC 1068 is reported which demonstrates that significant 20 micron emission originates at positions located more than 3 arcsec, or 260 pc, from the nucleus. These observations strongly support arguments that most of the infrared flux is thermal emission from dust. It is argued that the dust giving rise to this extended emission cannot be heated solely by a compact nuclear object. It is suggested that there is a powerful energy-generation mechanism, possibly an enormous burst of star formation, operating on a scale much larger than that identified with the visible nucleus.

  10. Micron-scale lens array having diffracting structures

    DOEpatents

    Goldberg, Kenneth A

    2013-10-29

    A novel micron-scale lens, a microlens, is engineered to concentrate light efficiently onto an area of interest, such as a small, light-sensitive detector element in an integrated electronic device. Existing microlens designs imitate the form of large-scale lenses and are less effective at small sizes. The microlenses described herein have been designed to accommodate diffraction effects, which dominate the behavior of light at small length scales. Thus a new class of light-concentrating optical elements with much higher relative performance has been created. Furthermore, the new designs are much easier to fabricate than previous designs.

  11. Advanced composite applications for sub-micron biologically derived microstructures

    NASA Technical Reports Server (NTRS)

    Schnur, J. M.; Price, R. R.; Schoen, P. E.; Bonanventura, Joseph; Kirkpatrick, Douglas

    1991-01-01

    A major thrust of advanced material development is in the area of self-assembled ultra-fine particulate based composites (micro-composites). The application of biologically derived, self-assembled microstructures to form advanced composite materials is discussed. Hollow 0.5 micron diameter cylindrical shaped microcylinders self-assemble from diacetylenic lipids. These microstructures have a multiplicity of potential applications in the material sciences. Exploratory development is proceeding in application areas such as controlled release for drug delivery, wound repair, and biofouling as well as composites for electronic and magnetic applications, and high power microwave cathodes.

  12. Fabrication of Micron Scale Retroreflectors for Novel Biosensors

    NASA Astrophysics Data System (ADS)

    Sherlock, Tim

    Many bioanalytical and diagnostic methods detect the presence of secondary labels, such as colored particles, fluorescent molecules, nanoparticles, and enzyme reaction product, when they accumulate in the presence of the target biomolecules (i.e., bacteria, viruses, etc.) at predetermined locations. In this dissertation, we describe the development of a new class of labels consisting of micro-fabricated retroreflectors that are easy to image, compatible with machine vision automation, and can be detected in solution or within microfluidic channels. The retroreflecting structures are designed to return incident light directly back to its source over a large range of angles, making them extremely detectable using low cost, low numerical aperture objectives, as is evidenced by their common use as lane markers and in safety signs. This work describes two different biosensing systems using these labels. In the first, retroreflectors are fabricated at fixed locations at the base of microfluidic channels and their brightness is attenuated by the biologically-driven accumulation of magnetic particles, thus forming a readout strategy that well-suited for automation and multiplexing. The work demonstrates that single, micron-scale magnetic beads can be rapidly detected over very large areas (square millimeters). The second approach uses suspended corner cube retroreflectors, five microns on a side, as ultra bright labels that are bound to magnetic sample preparation beads in the presence of an analyte. The magnetic particles can then be moved to an imaging site within the sample where the cubes are readily detected. The fabrication of these micron-scale retroreflectors required the development of new lithography, thin film disposition, and reactive ion etching tools and the integration of chip-based structures with microfluidic systems. The dissertation also describes the experimental validation of a Fourier optics model that accounts for diffraction inherent to the micron

  13. WISE 3.4 micron Detection of PTF10acbp

    NASA Astrophysics Data System (ADS)

    Cutri, R. M.; Hoffman, D.; Masci, F.; Conrow, T.; Kasliwal, M. M.; Helou, G.; Ofek, E. O.; Kulkarni, S. R.; Surace, J.

    2011-01-01

    The Wide-field Infrared Survey Explorer (WISE; Wright et al. 2010 AJ 140, 1868) scanned the position of PTF10acbp (ATEL #3094), the luminous red nova in the spiral galaxy UGC 11973, 23 times between 2010 June 17 and June 23, and again 30 times between 2010 December 12 and December 16, just five days after the transient's discovery. The June observations were made during the WISE cryogenic survey yielding images at 3.4, 4.6, 12 and 22 microns.

  14. Spectrophotometry at 10 microns of T Tauri stars

    NASA Technical Reports Server (NTRS)

    Cohen, M.; Witteborn, F. C.

    1985-01-01

    New 8-13 micron spectra of 32 T Tau, or related young, stars are presented. Silicate emission features are commonly seen. Absorptions occur less frequently but also match the properties of silicate materials. The shape of the emission feature suggests that a more crystalline grain is responsible in the T Tau stars than those of the Trapezium region. The evolution of the silicate component of the circumstellar shell around T Tau stars, and its dependence upon stellar wind activity, visual linear polarization, and extinction are investigated. Several correlations suggest that the shells are likely to be flattened, disklike structures rather than spherical.

  15. The variable role of slab-derived fluids in the generation of a suite of primitive calc-alkaline lavas from the Southernmost Cascades, California

    USGS Publications Warehouse

    Borg, L.E.; Clynne, M.A.; Bullen, T.D.

    1997-01-01

    The compositional continuum observed in primitive calc-alkaline lavas erupted from small volcanoes across the southernmost Cascade arc is produced by the introduction of a variable proportion of slab-derived fluid into the superjacent peridotite layer of the mantle wedge. Magmas derived from fluid-rich sources are erupted primarily in the forearc and are characterized by Sr and Pb enrichment (primitive mantle-normalized Sr/P > 5.5), depletions of Ta and Nb, low incompatible-element abundances, and MORB-like Sr and Pb isotopic ratios. Magmas derived from fluid-poor sources are erupted primarily in the arc axis and behind the arc, and are characterized by weak enrichment in Sr [1.0 < (Sr/P)N < 1.3], weak depletions in Ta and Nb, higher incompatible-element abundances, and OIB-like Sr, Nd, and Pb isotopic ratios. Fluxing the mantle wedge above the subducting slab with H2O-rich fluid stabilizes amphibole and enriches the wedge peridotites in incompatible elements, particularly unradiogenic Sr and Pb. The hydrated amphibole-bearing portion of the mantle wedge is downdragged beneath the forearc, where its solidus is exceeded, yielding melts that are enriched in Sr and Pb, and depleted in Ta and Nb (reflecting both high Sr and Pb relative to Ta and Nb in the fluid, and the greater compatibility of Ta and Nb in amphibole compared to other silicate phases in the wedge). A steady decrease of the fluid-contributed geochemical signature away from the trench is produced by the progressive dehydration of the downdragged portion of the mantle wedge with depth, resulting from melt extraction and increased temperature at the slab-wedge interface. Inverse correlation between incompatible-element abundances and the size of the fluid-contributed geochemical signature is generated by melting of more depleted peridotites, rather than by significant differences in the degree of melting. High-(Sr/P)N lavas of the forearc are generated by melting of a MORB-source-like peridotite that has

  16. Ray tracing calculations of the output from germanium slab lasers

    SciTech Connect

    Plowes, J. A.; Holden, P. B.; Pert, G. J.; Healy, S. B.; Kingston, A. E.; Roberts, E.

    1995-05-01

    A 3D Raytracing code is used, as a post processor, to simulate experimental observables, such as divergences, deflected angle, and output intensity, from a 1 1/2 D fluid code. The latter self consistently treats the plasma expansion with the atomic physics of the Ne-like ion. The results presented relate to two separate experiments. First, an experiment carried out at R. A. L. where Ge slab targets, of varying lengths, were irradiated at driving laser intensities in the range 0.8{yields}2.3x10{sup 13} W cm{sup -2}. Results presented here are for the 236 A line and good agreement is found with experiment. Also presented, are simulations which relate to an experiment carried out at Osaka University, where a 4 cm Ge slab target, with a curvature from 0 to 20 mrad, along the lasing axis, was irradiated. General agreement with experiment is obtained. Tightening in the output beam, with increasing curvature, can clearly be seen.

  17. Trench migration, net rotation and slab mantle coupling

    NASA Astrophysics Data System (ADS)

    Funiciello, F.; Faccenna, C.; Heuret, A.; Lallemand, S.; Di Giuseppe, E.; Becker, T. W.

    2008-07-01

    Laboratory models have been conducted to improve our understanding of the role that the resistance of the slab to bending and its coupling to the ambient mantle play in subduction dynamics over geological time scales. Our models are set up with a viscous plate of silicone (lithosphere) subducting under negative buoyancy in a viscous layer of glucose syrup (mantle). For our study, the lithosphere/upper mantle viscosity contrast has been systematically varied, from ~ 10 to ~ 10 5 in order to explore the parameter space between weak and strong slab dynamics. We found that subduction is characterized by a retreating mode for viscosity ratios > 10 4, by the coexistence of a retreating mode and an advancing mode for viscosity ratios between ~ 10 4 and ~ 10 2, and quasi-stationary, Rayleigh-Taylor like behaviour for ratios < 10 2. By combining our experimental results and kinematic data from current subduction zones in four reference frames which differ in the amount of net rotation, we infer that a lithosphere/upper mantle viscosity contrast of 150-500 is necessary to obtain realistic trench/subducting plate velocity ratios as well as the variability of subduction styles observed in nature.

  18. The role of ridges in the formation and longevity of flat slabs.

    PubMed

    Antonijevic, Sanja Knezevic; Wagner, Lara S; Kumar, Abhash; Beck, Susan L; Long, Maureen D; Zandt, George; Tavera, Hernando; Condori, Cristobal

    2015-08-13

    Flat-slab subduction occurs when the descending plate becomes horizontal at some depth before resuming its descent into the mantle. It is often proposed as a mechanism for the uplifting of deep crustal rocks ('thick-skinned' deformation) far from plate boundaries, and for causing unusual patterns of volcanism, as far back as the Proterozoic eon. For example, the formation of the expansive Rocky Mountains and the subsequent voluminous volcanism across much of the western USA has been attributed to a broad region of flat-slab subduction beneath North America that occurred during the Laramide orogeny (80-55 million years ago). Here we study the largest modern flat slab, located in Peru, to better understand the processes controlling the formation and extent of flat slabs. We present new data that indicate that the subducting Nazca Ridge is necessary for the development and continued support of the horizontal plate at a depth of about 90 kilometres. By combining constraints from Rayleigh wave phase velocities with improved earthquake locations, we find that the flat slab is shallowest along the ridge, while to the northwest of the ridge, the slab is sagging, tearing, and re-initiating normal subduction. On the basis of our observations, we propose a conceptual model for the temporal evolution of the Peruvian flat slab in which the flat slab forms because of the combined effects of trench retreat along the Peruvian plate boundary, suction, and ridge subduction. We find that while the ridge is necessary but not sufficient for the formation of the flat slab, its removal is sufficient for the flat slab to fail. This provides new constraints on our understanding of the processes controlling the beginning and end of the Laramide orogeny and other putative episodes of flat-slab subduction. PMID:26268192

  19. Two-way interaction between plume and slab: The Hainan-Manila example

    NASA Astrophysics Data System (ADS)

    Mériaux, Catherine; Duarte, João; Schellart, Wouter

    2015-04-01

    Three-dimensional upper-mantle laboratory models consisting of a compositional plume that is initiated underneath an entirely dynamically driven dense plate fixed at the surface along its trailing edge exhibit a two-way interaction between plume and slab. The slab influence on the plume is driven by the induced mantle flow generated by the plate motion, which includes a sinking and a retreating phase. Slab/Plume buoyancy flux ratios ranged between 7 and 18. In all models, the plume is being swept away from the slab during its rise, and once it has reached the surface, its head spreads towards the trench as a gravity current while its conduit keeps being deflected away. The plume influence on the slab is seen later, when the slab in its retreat gets closer to the plume. The plume buoyancy spreading under the slab then weakens the subduction rate. The degree to which the subduction rate is lessened is conditioned by the level of asymmetry, which the slab may develop along its free edge during its impact at the bottom surface. A lasting symmetric plate causes maximum disturbance of the plume to the slab retreat rate, while plate asymmetry alleviates the plume influence as the plume buoyancy is no longer trapped underneath the plate in its centreline but can escape sideways. Our laboratory model configuration applies to the Hainan plume and Manila subduction system. The geophysical and seismic observations showing the existence of a NW-SE tilting plume-like mantle low-velocity structure in the crust and in the mantle beneath the north Hainan Island-Leizhou Peninsula basalt province are explained by slab rollback induced toroidal mantle flow from the Manila subduction zone. On the basis of our models, it can be foreseen that the Hainan plume is to spread out under the Manila slab towards the mantle wedge in the future, which could lessen the Manila subduction rate.

  20. The role of ridges in the formation and longevity of flat slabs

    NASA Astrophysics Data System (ADS)

    Antonijevic, Sanja Knezevic; Wagner, Lara S.; Kumar, Abhash; Beck, Susan L.; Long, Maureen D.; Zandt, George; Tavera, Hernando; Condori, Cristobal

    2015-08-01

    Flat-slab subduction occurs when the descending plate becomes horizontal at some depth before resuming its descent into the mantle. It is often proposed as a mechanism for the uplifting of deep crustal rocks (`thick-skinned' deformation) far from plate boundaries, and for causing unusual patterns of volcanism, as far back as the Proterozoic eon. For example, the formation of the expansive Rocky Mountains and the subsequent voluminous volcanism across much of the western USA has been attributed to a broad region of flat-slab subduction beneath North America that occurred during the Laramide orogeny (80-55 million years ago). Here we study the largest modern flat slab, located in Peru, to better understand the processes controlling the formation and extent of flat slabs. We present new data that indicate that the subducting Nazca Ridge is necessary for the development and continued support of the horizontal plate at a depth of about 90 kilometres. By combining constraints from Rayleigh wave phase velocities with improved earthquake locations, we find that the flat slab is shallowest along the ridge, while to the northwest of the ridge, the slab is sagging, tearing, and re-initiating normal subduction. On the basis of our observations, we propose a conceptual model for the temporal evolution of the Peruvian flat slab in which the flat slab forms because of the combined effects of trench retreat along the Peruvian plate boundary, suction, and ridge subduction. We find that while the ridge is necessary but not sufficient for the formation of the flat slab, its removal is sufficient for the flat slab to fail. This provides new constraints on our understanding of the processes controlling the beginning and end of the Laramide orogeny and other putative episodes of flat-slab subduction.

  1. Mantle flow and dynamic topography associated with slab window opening: Insights from laboratory models

    NASA Astrophysics Data System (ADS)

    Guillaume, Benjamin; Moroni, Monica; Funiciello, Francesca; Martinod, Joseph; Faccenna, Claudio

    2010-12-01

    We present dynamically self-consistent mantle-scale laboratory models that have been conducted to improve our understanding of the influence of slab window opening on subduction dynamics, mantle flow and associated dynamic topography over geological time scales. The adopted setup consists of a two-layer linearly viscous system simulating the subduction of a fixed plate of silicone (lithosphere) under negative buoyancy in a viscous layer of glucose syrup (mantle). Our experimental setting is also characterized by a constant-width rectangular window located at the center of a laterally confined slab, modeling the case of the interaction of a trench-parallel spreading ridge with a wide subduction zone. We found that the opening of a slab window does not produce consistent changes of the geometry and the kinematics of the slab. On the contrary, slab-induced mantle circulation, quantified both in the vertical and horizontal sections using the Feature Tracking image analysis technique, is strongly modified. In particular, rollback subduction and the opening of the slab window generate a complex mantle circulation pattern characterized by the presence of poloidal and toroidal components, with the importance of each evolving according to kinematic stages. Mantle coming from the oceanic domain floods through the slab window, indenting the supra-slab mantle zone and producing its deformation without any mixing between mantle portions. The opening of the slab window and the upwelling of sub-slab mantle produce a regional-scale non-isostatic topographic uplift of the overriding plate that would correspond to values ranging between ca. 1 and 5 km in nature. Assuming that our modeling results can be representative of the natural behavior of subduction zones, we compared them to the tectonics and volcanism of the Patagonian subduction zone. We found that the anomalous backarc volcanism that has been developing since the middle Miocene could result from the lateral flow of sub-slab

  2. Search for Vega-like nearby stars with 12 micron excess

    NASA Technical Reports Server (NTRS)

    Aumann, Hartmut H.; Probst, Ronald G.

    1991-01-01

    The identification of Vega-like main-sequence stars with 10-micron excess would permit important measurements of the spatial extent of the radiating material with ground-based telescopes. In fact, 55 of the 548 nearby A, F, G, and K dwarfs with IRAS catalog magnitudes at 12 microns appear to have excess 12-micron flux. However, for only two of these stars, Beta Pic and Zeta Lep, was it possible, using small-aperture photometry at 2.2 and 10 microns, to verify that the 12-micron excess is with high likelihood associated with the star. For the remaining stars the apparent 12-micron color of the 106 A, F, G, and K stars in the observing program is only 0.02 mag. Excess flux due to a Vega-like cloud which may surround some of the sources in the observing program, like Alpha Lyrae, is thus typically not detectable at 10 microns.

  3. VTT's micron-scale silicon rib+strip waveguide platform

    NASA Astrophysics Data System (ADS)

    Aalto, Timo; Harjanne, Mikko; Cherchi, Matteo

    2016-05-01

    Silicon rib waveguides enable single-mode (SM) operation even with the combination of multi-micron core dimensions and high refractive index contrast. In such large waveguides the optical mode field is almost completely confined inside the Si core, which leads to small propagation losses and small polarization dependency. The unique SM condition of the rib waveguide also enables the use of an ultra-wide wavelength range, for example from 1.2 to <1.7 μm, without sacrificing either SM operation or low propagation loss. This makes micron-scale Si waveguides particularly well-suited for spectroscopy and extensive wavelength division multiplexing. However, rib waveguides require large bending radii, which lead to large circuit sizes. There are two solutions for this. So-called Euler bends in Si strip waveguides enable low-loss bends down to 1 μm bending radius with less than 0.1 dB/90° loss for both polarizations. Another alternative is a total-internal reflection mirror that can have loss as low as 0.1 dB for both polarizations in either strip or rib waveguides. The excitation of higher order modes in large strip waveguides is avoided by using adiabatic rib-strip converters and low-loss components. With rib and strip waveguides it is possible to reach a unique combination of low loss, extremely small footprint, small polarization dependency, ultra-wide bandwidth and tolerance to high optical powers.

  4. Chemically generated convective transport of micron sized particles

    NASA Astrophysics Data System (ADS)

    Shklyaev, Oleg; Das, Sambeeta; Altemose, Alicia; Shum, Henry; Balazs, Anna; Sen, Ayusman

    2015-11-01

    A variety of chemical and biological applications require manipulation of micron sized objects like cells, viruses, and large molecules. Increasing the size of particles up to a micron reduces performance of techniques based on diffusive transport. Directional transport of cargo toward detecting elements reduces the delivery time and improves performance of sensing devices. We demonstrate how chemical reactions can be used to organize fluid flows carrying particles toward the assigned destinations. Convection is driven by density variations caused by a chemical reaction occurring at a catalyst or enzyme-covered target site. If the reaction causes a reduction in fluid density, as in the case of catalytic decomposition of hydrogen peroxide, then fluid and suspended cargo is drawn toward the target along the bottom surface. The intensity of the fluid flow and the time of cargo delivery are controlled by the amount of reagent in the system. After the reagent has been consumed, the fluid pump stops and particles are found aggregated on and around the enzyme-coated patch. The pumps are reusable, being reactivated upon injection of additional reagent. The developed technique can be implemented in lab-on-a-chip devices for transportation of micro-scale object immersed in solution.

  5. Chip-on-flex with 5-micron features

    NASA Astrophysics Data System (ADS)

    Salmon, Peter C.

    2003-01-01

    A new module packaging method is proposed for electronic systems comprising a motherboard and integrated circuit (IC) chips. Pitches of 10 microns for conductive traces, and 100 microns for bonding pads are achievable. The enabling technology is glass panel manufacture, using equipment and techniques similar to those employed for fabricating liquid crystal display (LCD) panels. Flexible circuits are produced on a glass carrier using a release layer, and the carrier is removed after most of the processing is complete. IC chips are stud bumped and flip chip bonded to wells filled with solder, provided on the flexible circuit. The fabrication density achievable with wafer level packaging (WLP) using silicon wafers is substantially more than is needed for module packaging, as described herein. It is possible to provide WLP performance on glass at a much lower cost. The conductor features on glass are fine enough for the most demanding packaging and assembly techniques. The lowered cost of glass applies to the interconnection circuit plus assembly, test and rework. A test method called Tester-On-Board (TOB) is proposed, employing special-purpose test chips that are directly mounted in the system and mimic the capabilities of external testers. Methods for hermetic sealing, electromagnetic screening, and high-density off-board connections are also proposed.

  6. The micro fabrication using selective laser sintering micron metal powder

    NASA Astrophysics Data System (ADS)

    Chen, Jimin; Wang, Xubao; Zuo, Tiechuan

    2003-04-01

    Selective laser sintering (SLS) is a process that uses a rastering laser to sinter powder particles into a computer defined shape. In order to fabricate micro part with laser sintering the laser beam spot should be focused smaller, on the other hand the size of sintered powder particles should be smaller too. Therefore Nd:YAG laser doubling frequency is used to obtain mini-focus. Based on theories of nonlinear and resonant cavity, an equipment which perform frequency doubling on YAG laser(1.06μm) by the external resonant ring cavity has been designed. With the equipment the wave length of 0.532μm green light was output. The focused laser spot of 15μm diameter was obtained with 10W power. Meanwhile the micron metal powder was used in selective laser micro sintering (SLMS). The behavior of laser sintering different metal powder was investigated. Finally the micro Chinese characters which is small as a tip of match made with laser selective micro sintering micron metal powder are shown.

  7. The impact of slab dip variations, gaps and rollback on mantle wedge flow: insights from fluids experiments

    NASA Astrophysics Data System (ADS)

    MacDougall, Julia G.; Kincaid, Chris; Szwaja, Sara; Fischer, Karen M.

    2014-05-01

    Observed seismic anisotropy and geochemical anomalies indicate the presence of 3-D flow around and above subducting slabs. To investigate how slab geometry and velocity affect mantle flow, we conducted a set of experiments using a subduction apparatus in a fluid-filled tank. Our models comprise two independently adjustable, continuous belts to represent discrete sections of subducting slabs that kinematically drive flow in the surrounding glucose syrup that represents the upper mantle. We analyse how slab dip (ranging from 30° to 80°), slab dip difference between slab segments (ranging from 20° to 50°), rates of subduction (4-8 cm yr-1) and slab/trench rollback (0-3 cm yr-1) affect mantle flow. Whiskers were used to approximate mineral alignment induced by the flow, as well as to predict directions of seismic anisotropy. We find that dip variations between slab segments generate 3-D flow in the mantle wedge, where the path lines of trenchward moving mantle material above the slab are deflected towards the slab segment with the shallower dip. The degree of path line deflection increases as the difference in slab dip between the segments increases, and, for a fixed dip difference, as slab dip decreases. In cases of slab rollback and large slab dip differences, we observe intrusion of subslab material through the gap and into the wedge. Flow through the gap remains largely horizontal before eventual downward entrainment. Whisker alignment in the wedge flow is largely trench-normal, except near the lateral edges of the slab where toroidal flow dominates. In addition, whisker azimuths located above the slab gap deviate most strongly from trench-normal orientations when slab rollback does not occur. Such flow field complexities are likely sufficient to affect deep melt production and shallow melt delivery. However, none of the experiments produced flow fields that explain the trench-parallel shear wave splitting fast directions observed over broad arc and backarc

  8. Conformational transitions of cytochrome c in sub-micron-sized capsules at air/buffer interface.

    PubMed

    Jaganathan, Maheshkumar; Dhathathreyan, Aruna

    2014-09-30

    This work presents the design of sub-micron-sized capsules of Cytochrome c (cyt c) in the range 300-350 nm and the conformational transitions of the protein that occur when the films of these capsules spread at the air/buffer interface are subjected to repeated compression-expansion cycles. Steady state fluorescence, time-resolved fluorescence, and circular dichroic (CD) spectra have been used to study the highly compact native conformation (70% helicity) of the protein in the capsules and its stability has been analyzed using cyclic voltammetry. The capsules have been characterized using zeta sizer and high resolution transmission electron microscopy (HRTEM). Surface concentration-surface pressure (Γ-π) isotherms of the films of the capsules spread at air/buffer interface following compression-expansion show destabilizing effect on cyt c. FTIR and CD spectra of these films skimmed from the surface show that the protein transitions gradually from its native helical to an anomalous beta sheet aggregated state. This results from a competition between stabilizing hydrated polar segments of the protein in the capsule and destabilizing nonspecific hydrophobic interactions arising at the air/buffer interface. This 2D model could further our understanding of the spatial and temporal roles of proteins in confined spaces and also in the design of new drug delivery vehicles using proteins.

  9. Flute-interchange stability in a hot electron plasma

    SciTech Connect

    Dominguez, R.R.

    1980-01-01

    Several topics in the kinetic stability theory of flute-interchange modes in a hot electron plasma are discussed. The stability analysis of the hot-electron, curvature-driven flute-interchange mode, previously performed in a slab geometry, is extended to a cylindrical plasma. The cold electron concentration necessary for stability differs substantially from previous criteria. The inclusion of a finite temperature background plasma in the stability analysis results in an ion curvature-driven flute-interchange mode which may be stabilized by either hot-electron diamagnetic effects, hot-electron plasma density, or finite (ion) Larmor radius effects.

  10. Two-Pass, Diode-Pumped Nd:YAG Slab Laser Head

    NASA Technical Reports Server (NTRS)

    Coyle, D. Barry

    1992-01-01

    Neodymium/yttrium aluminum garnet (Nd:YAG) ring-laser head designed for compactness, simplicity, and increased efficiency for side pumping by diode lasers. Laser head includes two linear arrays of diode lasers, two fused-silica collimating rods, and Nd:YAG slab. Slab mounted on finned copper block, providing good thermal dissipation.

  11. Convective instability rising out of the underbelly of stagnant slabs in the Mantle Transition Zone

    NASA Astrophysics Data System (ADS)

    Ballmer, Maxim D.; Motoki, Matthew H.

    2016-04-01

    The study of volcanism can further our understanding of Earth's mantle processes and composition. Continental intraplate volcanism commonly occurs above subducted slabs that stagnate in the Mantle Transition Zone (MTZ), such as in Europe, eastern China, and western North America. Here, we use two-dimensional numerical models to explore the evolution of stagnant slabs in the MTZ and their potential to sustain mantle upwellings that can support volcanism. We find [1] that weak slabs may go convectively unstable within tens of Myr. Upwellings rise out of the relatively warm underbelly of the slab, are entrained by ambient-mantle flow and reach the base of the lithosphere. The first and most vigorous upwellings rise adjacent to lateral heterogeneity within the slab. Ultimately, convective instability also acts to separate the compositional components of the slab, harzburgite and eclogite, from each other with harzburgite rising into the upper mantle and eclogite sinking toward the base of the MTZ, and potentially into the lower mantle. Such a physical filtering process may sustain a long-term compositional stratification across the mantle [2]. [1] Motoki, M. H. and M. D. Ballmer (2015): Convective instability of Stagnant Slabs in the Mantle Transition Zone, Geochem. Geophys. Geosys., doi:10.1002/2014GC005608. [2] Ballmer, M. D., N. C. Schmerr, T. Nakagawa, and J. Ritsema (2015): Compositional mantle layering revealed by slab stagnation at ~1,000 km depth, Science Advances, doi:10.1126/sciadv.1500815

  12. Degradation and mechanism of the mechanics and durability of reinforced concrete slab in a marine environment

    NASA Astrophysics Data System (ADS)

    Wu, Sheng-xing; Liu, Guan-guo; Bian, Han-bing; Lv, Wei-bo; Jiang, Jian-hua

    2016-04-01

    An experimental research was conducted to determine the corrosion and bearing capacity of a reinforced concrete (RC) slab at different ages in a marine environment. Results show that the development of corrosion-induced cracks on a slab in a marine environment can be divided into three stages according to crack morphology at the bottom of the slab. In the first stage, cracks appear. In the second stage, cracks develop from the edges to the middle of the slab. In the third stage, longitudinal and transverse corrosion-induced cracks coexist. The corrosion ratio of reinforcements nonlinearly increases with the age, and the relationship between the corrosion ratio of the reinforcements and the corrosion-induced crack width of the concrete is established. The flexural capacity of the corroded RC slab nonlinearly decreases with the age, and the model for the bearing capacity factor of the corroded RC slab is established. The mid-span deflection of the corroded RC slab that corresponds to the yield of the reinforcements linearly increases with the increase in corrosion ratio. Finally, the mechanisms of corrosion morphology and the degradation of the mechanical properties of an RC slab in a marine environment are discussed on the basis of the basic theories of steel corrosion in concrete and concrete structure design.

  13. Juan de Fuca slab geometry and its relation to Wadati-Benioff zone seismicity

    USGS Publications Warehouse

    McCrory, Patricia A.; Blair, J. Luke; Waldhause, Felix; Oppenheimer, David H.

    2012-01-01

    A new model of the subducted Juan de Fuca plate beneath western North America allows first-order correlations between the occurrence of Wadati-Benioff zone earthquakes and slab geometry, temperature, and hydration state. The geo-referenced 3D model, constructed from weighted control points, integrates depth information from earthquake locations and regional seismic velocity studies. We use the model to separate earthquakes that occur in the Cascadia forearc from those that occur within the underlying Juan de Fuca plate and thereby reveal previously obscured details regarding the spatial distribution of earthquakes. Seismicity within the slab is most prevalent where the slab is warped beneath northwestern California and western Washington suggesting that slab flexure, in addition to expected metamorphic dehydration processes, promotes earthquake occurrence within the subducted oceanic plate. Earthquake patterns beneath western Vancouver Island are consistent with slab dehydration processes. Conversely, the lack of slab earthquakes beneath western Oregon is consistent with an anhydrous slab. Double-differenced relocated seismicity resolves a double seismic zone within the slab beneath northwestern California that strongly constrains the location of the plate interface and delineates a cluster of seismicity 10 km above the surface that includes the 1992 M7.1 Mendocino earthquake. We infer that this earthquake ruptured a surface within the Cascadia accretionary margin above the Juan de Fuca plate. We further speculate that this earthquake is associated with a detached fragment of former Farallon plate. Other subsurface tectonic elements within the forearc may have the potential to generate similar damaging earthquakes.

  14. ENGINEERING DESIGN CRITERIA FOR SUB-SLAB DEPRESSURIZATION SYSTEMS IN LOW-PERMEABILTY SOLIDS

    EPA Science Inventory

    The report describes the development of engineering design criteria for the successful design, installation, and operation of sub-slab depressurization systems, based on radon (Rn) mitigation experience on 14 slab-on-grade houses in South Central Florida. The Florida houses are c...

  15. A numerical model for calculating vibration due to a harmonic moving load on a floating-slab track with discontinuous slabs in an underground railway tunnel

    NASA Astrophysics Data System (ADS)

    Hussein, M. F. M.; Hunt, H. E. M.

    2009-03-01

    This paper presents a new method for modelling floating-slab tracks with discontinuous slabs in underground railway tunnels. The track is subjected to a harmonic load moving with a constant velocity. The model consists of two sub-models. The first is an infinite track with periodic double-beam unit formulated as a periodic infinite structure. The second is modelled with a new version of the Pipe-in-Pipe (PiP) model that accounts for a tunnel wall embedded in a half-space. The two sub-models are coupled by writing the force transmitted from the track to the tunnel as a continuous function using Fourier series representation and satisfying the compatibility condition. The displacements at the free surface are calculated for a track with discontinuous slab and compared with those of a track with continuous slab. The results show that the far-field vibration can be significantly increased due to resonance frequencies of slabs for tracks with discontinuous slabs.

  16. The study of the transition regime between slab and mixed slab-toroidal electron temperature gradient modes in a basic experiment

    NASA Astrophysics Data System (ADS)

    Balbaky, Abed; Sokolov, Vladimir; Sen, Amiya K.

    2015-05-01

    Electron temperature gradient (ETG) modes are suspected sources of anomalous electron thermal transport in magnetically confined plasmas as in tokamaks. Prior work in the Columbia Linear Machine (CLM) has been able to produce and identify slab ETG modes in a slab geometry [Wei et al., Phys. Plasmas 17, 042108 (2010)]. Now by modifying CLM to introduce curvature to the confining axial magnetic field, we have excited mixed slab-toroidal modes. Linear theory predicts a transition between slab and toroidal ETG modes when /k ∥ R c k y ρ ˜ 1 [J. Kim and W. Horton, Phys. Fluids B 3, 1167 (1991)]. We observe changes in the mode amplitude for levels of curvature Rc - 1 ≪ /k ∥ , s l a b k ⊥ ρ , which may be explained by reductions in k ∥ in the transition from slab to mixed slab-toroidal modes, as also predicted by theory. We present mode amplitude scaling as a function of magnetic field curvature. Over the range of curvature available in CLM experimentally we find a modest increase in saturated ETG potential fluctuations (˜1.5×), and a substantial increase in the power density of individual mode peaks (˜4-5×).

  17. Overriding plate thickness control on subducting slab curvature

    NASA Astrophysics Data System (ADS)

    Holt, A.; Buffett, B. A.; Becker, T. W.

    2014-12-01

    The curvature of subducting lithosphere controls deformation due to bending at the trench, which results in a force that dissipates gravitational potential energy and may affect seismic coupling. We use 2-D, thermo-mechanical subduction models to explore the dependence of the radius of curvature on the thickness of the subducting and overriding plates for models with both viscous and effectively plastic lithospheric rheologies. Such a plastic rheology has been shown to reproduce the bending stresses/moment computed using a kinematic strain rate description and a laboratory derived composite rheology. Laboratory and numerical models show that the bending geometry of subducting slabs with a viscous rheology is strongly dependent on slab thickness; thicker plates have a larger radius of curvature. However, the curvature of subducting plates on Earth, illuminated by the distribution of earthquake hypocenters, shows little to no dependence on the plate thickness or age. Such an observation is instead compatible with plates that have a plastic rheology. Indeed, our numerical models show that the radius of curvature of viscous plates has a stronger dependence on subducting plate thickness than in equivalent plastic models. In viscous plates, the bending moment produces a torque, which balances the torque exerted by buoyancy. However, for the plastic plate case the bending moment saturates at a maximum value and so cannot balance the gravitational torque. The saturation of bending moment means that, (a) the radius of curvature of the bending region is not constrained by this torque balance, and, (b) other forces are required to balance the gravitational torque. We explore the role that the overriding plate could play in controlling the subducting plate curvature in plastic plate models where the bending stresses have saturated. For such plates, we find that increasing the thickness of the overriding plate causes the radius of curvature to increase. The same correlation is

  18. Seismic imaging of the stagnant Pacific slab in the mantle transition zone under East Asia

    NASA Astrophysics Data System (ADS)

    Zhao, D.

    2008-12-01

    We used regional and global seismic tomography to determine high-resolution 3-D P-wave velocity structure of the crust and mantle down to 1200 km depth under Western Pacific to East Asia (Zhao, 2004, 2007; Huang and Zhao, 2006). A large number of arrival times of P, pP, PP and PcP waves recorded by many seismic stations in East Asia are used in the tomographic inversions. The subducting Pacific slab is imaged clearly as a high-velocity zone from the oceanic trenches down to 670-km depth, and intermediate-depth and deep earthquakes are located within the slab. The Pacific slab becomes stagnant in the mantle transition zone under eastern China. The western edge of the stagnant slab is generally parallel with the Japan trench and the Ryukyu trench and roughly coincides with a prominent surface topographic boundary in East China. Although there are some discrepancies between the topographic boundary and the western edge of the stagnant slab, both of them are located approximately 1800 km west of the trenches. The entire Pacific slab is stagnant in the mantle transition zone under Northeast China (53-37 degree north latitude). Under 37-28 degree north latitude, however, some of the slab materials are visible below the 670-km discontinuity, though most of the slab materials are still in the transition zone, suggesting that part of the slab materials have started to drop down to the lower mantle. Under the Mariana arc, the Pacific slab penetrates directly down to the lower mantle. It is also visible that the Philippine Sea slab has subducted down to the mantle transition zone depth under western Japan and the Ryukyu back-arc region (Abdelwahed and Zhao, 2007). There are three active intraplate volcanoes in China. The Changbai and Wudalianchi volcanoes in Northeast China are underlain by significant slow anomalies in the upper mantle, above the stagnant Pacific slab, suggesting that the two active volcanoes are not hot spots but a kind of back-arc volcanoes associated with

  19. Phase stability of zirconia at nanoscale.

    NASA Astrophysics Data System (ADS)

    Sabiryanov, Renat; Mei, W. N.

    2004-03-01

    There are three phases of ZrO2, namely cubic, tetragonal and monoclinic. Cubic phase of zirconia is usually stabilized by various dopants such as yttria and magnesia. However, it has been observed that these stablizers are indeed the source failure of doped ZrO2 in both orthopaedics and in ZrO2 used in high temperature applications. Recently, the cubic zirconia was fabricated as granular media with the grain sizes less than 17nm. We examine the phase stability in zirconia nanoparticles using first principle electronic structure method. We observe considerable relaxation of lattice in the monoclinic phase near the surface. This effect combined with surface tension and possibly vacancies in nanostructures are sources of stability of cubic zirconia at nanoscale. We performed calculation of the surface tension calculations for the pure (001) surface. The uniform compressive strain is applied in the plane of the slab to find the elastic response of the system. The slab is allowed to relax in the perpendicular direction. Uniform compressive strain in the plane of the slab causes increase in the distance between Zr and O layers for (001) surface (as a solid tends to preserve the volume). For cubic it gives -0.65N/m, while for monoclinic -0.48N/m. Furthermore, the solid-gas surface tension is a fundamental physical/chemical property of a solid, which affects its wetting properties. Therefore, cubic zirconia is more suitable to design the material combining wettability, ductility and hardness.

  20. Farallon slab detachment and deformation of the Magdalena Shelf, southern Baja California

    USGS Publications Warehouse

    Brothers, Daniel S.; Harding, Alistair J.; Gonzalez-Fernandez, Antonio; Holbrook, W.S. Steven; Kent, Graham M.; Driscoll, Neal W.; Fletcher, John M.; Lizarralde, Daniel; Umhoefer, Paul J.; Axen, Gary

    2012-01-01

    Subduction of the Farallon plate beneath northwestern Mexico stalled by ~12 Ma when the Pacific-Farallon spreading-ridge approached the subduction zone. Coupling between remnant slab and the overriding North American plate played an important role in the capture of the Baja California (BC) microplate by the Pacific Plate. Active-source seismic reflection and wide-angle seismic refraction profiles across southwestern BC (~24.5°N) are used to image the extent of remnant slab and study its impact on the overriding plate. We infer that the hot, buoyant slab detached ~40 km landward of the fossil trench. Isostatic rebound following slab detachment uplifted the margin and exposed the Magdalena Shelf to wave-base erosion. Subsequent cooling, subsidence and transtensional opening along the shelf (starting ~8 Ma) starved the fossil trench of terrigenous sediment input. Slab detachment and the resultant rebound of the margin provide a mechanism for rapid uplift and exhumation of forearc subduction complexes.

  1. Experimental validation of systematically designed acoustic hyperbolic meta material slab exhibiting negative refraction

    NASA Astrophysics Data System (ADS)

    Christiansen, Rasmus E.; Sigmund, Ole

    2016-09-01

    This Letter reports on the experimental validation of a two-dimensional acoustic hyperbolic metamaterial slab optimized to exhibit negative refractive behavior. The slab was designed using a topology optimization based systematic design method allowing for tailoring the refractive behavior. The experimental results confirm the predicted refractive capability as well as the predicted transmission at an interface. The study simultaneously provides an estimate of the attenuation inside the slab stemming from the boundary layer effects—insight which can be utilized in the further design of the metamaterial slabs. The capability of tailoring the refractive behavior opens possibilities for different applications. For instance, a slab exhibiting zero refraction across a wide angular range is capable of funneling acoustic energy through it, while a material exhibiting the negative refractive behavior across a wide angular range provides lensing and collimating capabilities.

  2. The output beam quality of a Q-switched Nd:glass slab laser

    NASA Technical Reports Server (NTRS)

    Reed, Murray K.; Byer, Robert L.

    1990-01-01

    The authors have constructed and tested a flashlamp pumped, Q-switched, Nd:glass zigzag slab laser. The thermally induced optical distortion through the slab is minimized by uniform pumping and cooling and the use of corrective pump shields at the slab ends. The laser spatial output for Q-switched resonators has been measured and modeled. It is shown that a larger aperture planar oscillator has an output divergence many times above the diffraction limit. Operation as a one-dimensional unstable resonator in the wide direction of the slab allows the efficient extraction of energy in a high-quality beam. Near-diffraction-limited laser output of 5 J at 4 Hz is achieved with a resonator that includes an intracavity telescope to correct for residual defocusing in the thin direction of the slab.

  3. Series solution to coupled nonlinear heat and moisture transfer in slabs with temperature-dependent diffusivities

    NASA Astrophysics Data System (ADS)

    Chiba, Ryoichi

    2014-12-01

    The two-dimensional differential transform method (DTM) is applied to solve the one-dimensional coupled heat and moisture diffusion problem for a slab with temperature-dependent thermal and moisture diffusivities, which are expressed by a linear function and an exponential function of temperature, respectively. One surface of the slab is subjected to convective hygrothermal loading and the other has constant prescribed temperature and moisture. Approximate analytical (series) solutions for the temperature and moisture profiles in the slab are derived. The transformed functions included in the solutions are obtained through a simple recursive procedure. Numerical results for a slab subjected to a sudden change in surface temperature illustrate the effects of temperature-dependent diffusivities on the transient temperature and moisture profiles of the slab. The results indicate that the nonlinear effect originating from the varying moisture diffusivity is not negligible for resin composites. The DTMis a useful new analytical method for solving nonlinear coupled transient problems.

  4. Discovering sub-micron ice particles across Dione' surface

    NASA Astrophysics Data System (ADS)

    Scipioni, Francesca; Schenk, Pual; Tosi, Federico; Clark, Roger; Dalle Ore, Cristina; Combe, Jean-Philippe

    2015-11-01

    Water ice is the most abundant component of Saturn’s mid-sized moons. However, these moons show an albedo asymmetry - their leading sides are bright while their trailing side exhibits dark terrains. Such differences arise from two surface alteration processes: (i) the bombardment of charged particles from the interplanetary medium and driven by Saturn’s magnetosphere on the trailing side, and (ii) the impact of E-ring water ice particles on the satellites’ leading side. As a result, the trailing hemisphere appears to be darker than the leading side. This effect is particularly evident on Dione's surface. A consequence of these surface alteration processes is the formation or the implantation of sub-micron sized ice particles.The presence of such particles influences and modifies the surfaces' spectrum because of Rayleigh scattering by the particles. In the near infrared range of the spectrum, the main sub-micron ice grains spectral indicators are: (i) asymmetry and (ii) long ward minimum shift of the absorption band at 2.02 μm (iii) a decrease in the ratio between the band depths at 1.50 and 2.02 μm (iv) a decrease in the height of the spectral peak at 2.6 μm (v) the suppression of the Fresnel reflection peak at 3.1 μm and (vi) the decrease of the reflection peak at 5 μm relative to those at 3.6 μm.We present results from our ongoing work mapping the variation of sub-micron ice grains spectral indicators across Dione' surface using Cassini-VIMS cubes acquired in the IR range (0.8-5.1 μm). To characterize the global variations of spectral indicators across Dione' surface, we divided it into a 1°x1° grid and then averaged the band depths and peak values inside each square cell.We will investigate if there exist a correspondence with water ice abundance variations by producing water ice' absorption band depths at 1.25, 1.52 and 2.02 μm, and with surface morphology by comparing the results with ISS color maps in the ultraviolet, visible and infrared

  5. Insights on slab-driven mantle flow from advances in three-dimensional modelling

    NASA Astrophysics Data System (ADS)

    Jadamec, Margarete A.

    2016-10-01

    The wealth of seismic observations collected over the past 20 years has raised intriguing questions about the three-dimensional (3D) nature of the mantle flow field close to subduction zones and provided a valuable constraint for how the plate geometry may influence mantle flow proximal to the slab. In geodynamics, there has been a new direction of subduction zone modelling that has explored the 3D nature of slab-driven mantle flow, motivated in part by the observations from shear wave splitting, but also by the observed variations in slab geometries worldwide. Advances in high-performance computing are now allowing for an unprecedented level of detail to be incorporated into numerical models of subduction. This paper summarizes recent advances from 3D geodynamic models that reveal the complex nature of slab-driven mantle flow, including trench parallel flow, toroidal flow around slab edges, mantle upwelling at lateral slab edges, and small scale convection within the mantle wedge. This implies slab-driven mantle deformation zones occur in the asthenosphere proximal to the slab, wherein the mantle may commonly flow in a different direction and rate than the surface plates, implying laterally variable plate-mantle coupling. The 3D slab-driven mantle flow can explain, in part, the lateral transport of geochemical signatures in subduction zones. In addition, high-resolution geographically referenced models can inform the interpretation of slab structure, where seismic data are lacking. The incorporation of complex plate boundaries into high-resolution, 3D numerical models opens the door to a new avenue of research in model construction, data assimilation, and modelling workflows, and gives 3D immersive visualization a new role in scientific discovery.

  6. Slab detachment during continental collision: Influence of crustal rheology and interaction with lithospheric delamination

    NASA Astrophysics Data System (ADS)

    Duretz, T.; Gerya, T. V.

    2013-08-01

    Collision between continents can lead to the subduction of continental material. If the crust remains coupled to the downgoing slab, a large buoyancy force is generated. This force slows down convergence and promotes slab detachment. If the crust resists to subduction, it may decouple from the downgoing slab and be subjected to buoyant extrusion. We employ two-dimensional thermo-mechanical modelling to study the importance of crustal rheology on the evolution of subduction-collision systems. We propose simple quantifications of the mechanical decoupling between lithospheric levels (σ*) and the potential for buoyant extrusion of the crust (ξ*). The modelling results indicate that a variable crustal rheological structure results in slab detachment, delamination, or the combination of both mechanisms. A strong crust provides coupling at the Moho (low σ*) and remains coherent during subduction (low ξ). It promotes deep subduction of the crust (180 km) and slab detachment. Exhumation occurs in coherent manners via eduction and thrusting. Slab detachment triggers the development of topography (> 4.5 km) close to the suture. A contrasting style of collision occurs using a weak crustal rheology. Mechanical decoupling at the Moho (high σ*) promotes the extrusion of the crust (high ξ), disabling slab detachment. Ongoing shortening leads to buckling of the crust and development of topography on the lower plate. Collisions involving rheologically layered crust allow decoupling at mid-crustal depths. This structure favours both the extrusion of upper crust and the subduction of the lower crust. Such collisions are successively affected by delamination and slab detachment. Topography develops together with the buoyant extrusion of crust onto the foreland and is further amplified by slab detachment. Our results suggest that the occurrence of both delamination (Apennines) and slab detachment (Himalayas) in orogens may indicate differences in the initial crustal structure of

  7. Mechanisms controlling the modes of the sinking slab into the transition zone

    NASA Astrophysics Data System (ADS)

    Agrusta, Roberto; Goes, Saskia; van Hunen, Jeroen

    2016-04-01

    It is generally accepted that subducting slabs can either sink into the lower mantle, lie down in the mantle transition zone, or even stagnate beneath it. Several studies have looked at correlations between subduction zone parameters and the ability of the slabs to penetrate into the lower mantle. These studies have suggested that the key parameters to control whether slabs stagnate or penetrate are trench motions, slab strength, buoyant features and/or the overriding plate. For example, there is evidence that older lithospheres show significant trench retreat, and tend to lie down flat above the transition zone (northwest Pacific), whereas younger lithospheres, less able to drive trench retreat, tend to sink into the lower mantle (central America). Moreover, numerical modelling studies have shown further correlations with parameters that cannot be directly observed. For example, slab penetration is inhibited by density and viscosity increases associated with post-spinel phase transition. Numerical modelling has been one of the key tools to investigate slab penetration, and a lot of insight has been gained from these studies. But most of these studies assume (statistical) steady ­state scenarios, in which slab stagnation or slab penetration is more or less a permanent feature. However, on Earth different modes of slab - transition zone interaction probably need to be able to change in time from penetrating to stagnant and also vice versa. In this study, using 2D self-consistent numerical subduction models, we test plausible mechanisms which may trigger different modes of slab deformation in the transition zone and may explain both spatial and temporal variability.

  8. Planar prism spectrometer based on adiabatically connected waveguiding slabs

    NASA Astrophysics Data System (ADS)

    Civitci, F.; Hammer, M.; Hoekstra, H. J. W. M.

    2016-04-01

    The device principle of a prism-based on-chip spectrometer for TE polarization is introduced. The spectrometer exploits the modal dispersion in planar waveguides in a layout with slab regions having two different thicknesses of the guiding layer. The set-up uses parabolic mirrors, for the collimation of light of the input waveguide and focusing of the light to the receiver waveguides, which relies on total internal reflection at the interface between two such regions. These regions are connected adiabatically to prevent unwanted mode conversion and loss at the edges of the prism. The structure can be fabricated with two wet etching steps. The paper presents basic theory and a general approach for device optimization. The latter is illustrated with a numerical example assuming SiON technology.

  9. High-Performance Slab-on-Grade Foundation Insulation Retrofits

    SciTech Connect

    Goldberg, Louise F.; Mosiman, Garrett E.

    2015-09-01

    A more accurate assessment of slab-on-grade foundation insulation energy savings than traditionally possible is now feasible. This has been enabled by advances in whole building energy simulation with 3-dimensional foundation modelling integration at each time step together with an experimental measurement of the site energy savings of SOG foundation insulation. Ten SOG insulation strategies were evaluated on a test building to identify an optimum retrofit insulation strategy in a zone 6 climate (Minneapolis, MN). The optimum insulation strategy in terms of energy savings and cost effectiveness consisted of two components: (a) R-20 XPS insulation above grade, and, (b) R-20 insulation at grade (comprising an outer layer of R-10 insulation and an interior layer of R-12 poured polyurethane insulation) tapering to R-10 XPS insulation at half the below-grade wall height (the lower half of the stem wall was uninsulated).

  10. Slab waveguide theory for general multi-slot waveguide

    NASA Astrophysics Data System (ADS)

    Le, ZiChun; Yin, LiXiang; Zou, Yu; Wu, Xiang

    2016-07-01

    Optical devices based on slot waveguide are of considerable interest in numerous applications due to the distinct feature of strong electric field confinement in a low-refractive index region. A theoretical model based on multi-slab waveguide theory is used to reveal the physical mechanism of the slot waveguide. The calculation results derived from the basic Helmholtz equation for the conventional single-slot waveguide with a ~2% validation of the effective refractive index are compared to the former experiment results by the Cornell University group. Moreover, we extend the theoretical model to a general multi-slot waveguide. Its electric field distribution and key properties such as optical power confinement factor and enhancement factor in slot are deduced theoretically and fully discussed.

  11. Where has the Flat-Fattened-Farallon Slab gone?

    NASA Astrophysics Data System (ADS)

    Helmberger, D. V.; Sun, D.; Bai, K.; Gurnis, M.

    2014-12-01

    It has been hypothesized that much of the Laramide orogeny producing the Rock Mountain Front was caused by dynamic effects induced by flat-slabs during a period of subducting plateaus. It has further been hypothesized that a particularly flat block containing the Shatsky Rise conjugate left a foot print from Southern California to Colorado with dimensions of about 500 km in width and 1000km in length. Here we rediscovered this block beneath the Midwest at a depth of about 660km and dipping northeastward at about 35°. This resolution was accomplished by exploiting the USArray seismic observations where detailed waveform modeling allowed both the shape and sharpness of a candidate tomographic image as box-like. This structure when migrated back in time to California (using G-plate mapping) fits the above hypothesized block quite well lending strong support for the above hypothesis.

  12. Two Micron Laser Technology Advancements at NASA Langley Research Center

    NASA Technical Reports Server (NTRS)

    Singh, Upendra N.

    2010-01-01

    An Independent Laser Review Panel set up to examine NASA s space-based lidar missions and the technology readiness of lasers appropriate for space-based lidars indicated a critical need for an integrated research and development strategy to move laser transmitter technology from low technical readiness levels to the higher levels required for space missions. Based on the review, a multiyear Laser Risk Reduction Program (LRRP) was initiated by NASA in 2002 to develop technologies that ensure the successful development of the broad range of lidar missions envisioned by NASA. This presentation will provide an overview of the development of pulsed 2-micron solid-state laser technologies at NASA Langley Research Center for enabling space-based measurement of wind and carbon dioxide.

  13. Nature of the 1100 Micron AzTEC-COSMOS Sources

    NASA Astrophysics Data System (ADS)

    Yun, Min Su; Aguirre, J.; Aretxaga, I.; Austermann, J.; Bock, J.; Fazio, G.; Huang, J.; Hughes, D.; Kang, Y.; Kim, S.; Lowenthal, J.; Ma, C.; Mauskopf, P.; Perera, T.; Sanders, D.; Scott, K.; Scoville, N.; Wilson, G.; Yoon, I.

    2006-12-01

    The Cosmic Evolution Survey (COSMOS) is a 2 square degree HST/ACS survey specifically designed to probe galaxy evolution as a function of time and environment (PI: N. Scoville). To take advantage of the extensive complementary databases already available through the COSMOS collaboration, we have undertaken a 1100 micron imaging survey of a 30' x 30' field centered just north of the earlier mm/submm surveys by the Bolocam on CSO and MAMBO on the IRAM 30-m telescope. In this poster paper, we will compare the results of the AzTEC and Bolocam surveys and discuss the nature of the AzTEC sources based on the existing multi-wavelength data in hand.

  14. The 4 micron spectra of compact infrared sources

    NASA Technical Reports Server (NTRS)

    Hofmann, R.; Larson, H. P.; Fink, U.

    1986-01-01

    High resolution 5 arcsec spectra in the 4 micron region are presented of the central 5 arcsec of the compact near infrared sources K3-50, W51-IRS2 East, and G333.6-0.2. From measured Br-alpha/Pf-beta line ratios and previously published infrared and radio maps, it is concluded that standard recombination theory fails to explain our observations in at least two cases. It is demonstrated that the data are consistent with thermal excitation of the hydrogen lines in strong stellar winds. The Pf-beta Hu-epsilon line ratio, which is completely insensitive to differential extinction, confirms the need for the stellar wind model for the core of G333.6-0.2. From the (K III) line it is estimated that the potassium abundance in G333.6-0.2 is at least equal to the solar value, and possibly enhanced by a factor up to 10.

  15. EUV mask reflectivity measurements with micron-scale spatial resolution

    SciTech Connect

    Goldberg, Kenneth A.; Rekawa, S.B.; Kemp, C.D.; Barty, A.; Anderson, E.H.; Kearney, Patrick; Han, Hakseung

    2008-05-26

    The effort to produce defect-free mask blanks for EUV lithography relies on increasing the detection sensitivity of advanced mask inspection tools, operating at several wavelengths. We describe the unique measurement capabilities of a prototype actinic (EUV wavelength) microscope that is capable of detecting small defects and reflectivity changes that occur on the scale of microns to nanometers. Types of defects: (a) Buried Substrate Defects: particles & pits (causes amplitude and/or phase variations); (b) Surface Contamination (reduces reflectivity and (possibly) contrast); (c) Damage from Inspection and Use (reduces the reflectivity of the multilayer coating). This paper presents an overview of several topics where scanning actinic inspection makes a unique contribution to EUVL research. We describe the role of actinic scanning inspection in four cases: defect repair studies; observations of laser damage; after scanning electron microscopy; and native and programmed defects.

  16. Predicting fracture in micron-scale polycrystalline silicon MEMS structures.

    SciTech Connect

    Hazra, Siddharth S.; de Boer, Maarten Pieter; Boyce, Brad Lee; Ohlhausen, James Anthony; Foulk, James W., III; Reedy, Earl David, Jr.

    2010-09-01

    Designing reliable MEMS structures presents numerous challenges. Polycrystalline silicon fractures in a brittle manner with considerable variability in measured strength. Furthermore, it is not clear how to use a measured tensile strength distribution to predict the strength of a complex MEMS structure. To address such issues, two recently developed high throughput MEMS tensile test techniques have been used to measure strength distribution tails. The measured tensile strength distributions enable the definition of a threshold strength as well as an inferred maximum flaw size. The nature of strength-controlling flaws has been identified and sources of the observed variation in strength investigated. A double edge-notched specimen geometry was also tested to study the effect of a severe, micron-scale stress concentration on the measured strength distribution. Strength-based, Weibull-based, and fracture mechanics-based failure analyses were performed and compared with the experimental results.

  17. 8- to 13-micron spectroscopy of Comet Levy 1990 XX

    NASA Technical Reports Server (NTRS)

    Lynch, David K.; Russell, Ray W.; Hackwell, John A.; Hanner, Martha S.; Hammel, Heidi B.

    1992-01-01

    The results are reported of IR spectroscopy of Comet Levy 1990 XX over a three-day period when the comet was about 1.54 AU from the sun roughly 70 days before perihelion. Comet Levy 1990 XX was bright, and for at least part of its inbound journey toward perihelion, active. At a distance of 1.54 AU from the sun it showed strong structured silicate emission with peaks or shoulders at 9.8 and 11.2 microns. These features resemble those of Comets P/Halley and Bradfield 1987 XXIX. The comet was variable in brightness. Specifically, the contrast of the silicate features changed by a factor of two relative to the continuum level and showed some evidence for a shape change as well.

  18. High spatial resolution 10 micron imaging of IRC + 10216

    NASA Technical Reports Server (NTRS)

    Bloemhof, E. E.; Danchi, W. C.; Townes, C. H.; Mclaren, R. A.

    1988-01-01

    Precise high-resolution 10-micron images of the carbon star IRC + 10216 have been obtained with a scanned linear array. The low noise and high dynamic range of these images permit deconvolution of the telescope point-spread function, revealing the radial brightness distribution of the circumstellar dust shell: approximate reflection symmetry is found in west-east scans, with a distinct division into two components of diameter about 0.40 and 2.2 arcsec. It is shown that this morphology is consistent with published interferometric data that had cast doubt upon an earlier, idealized two-component model. The observed brightness distribution implies that the circumstellar dust density may deviate substantially from the 1/r squared radial dependence expected for spherically symmetric outflow with constant velocity and constant rate of mass loss.

  19. Mars Atmospheric Characterization Using Advanced 2-Micron Orbiting Lidar

    NASA Technical Reports Server (NTRS)

    Singh, U.; Engelund, W.; Refaat, T.; Kavaya, M.; Yu, J.; Petros, M.

    2015-01-01

    Mars atmospheric characterization is critical for exploring the planet. Future Mars missions require landing massive payloads to the surface with high accuracy. The accuracy of entry, descent and landing (EDL) of a payload is a major technical challenge for future Mars missions. Mars EDL depends on atmospheric conditions such as density, wind and dust as well as surface topography. A Mars orbiting 2-micron lidar system is presented in this paper. This advanced lidar is capable of measuring atmospheric pressure and temperature profiles using the most abundant atmospheric carbon dioxide (CO2) on Mars. In addition Martian winds and surface altimetry can be mapped, independent of background radiation or geographical location. This orbiting lidar is a valuable tool for developing EDL models for future Mars missions.

  20. Multiple-Instrument Analyses of Single Micron-Size Particles

    NASA Astrophysics Data System (ADS)

    Admon, Uri; Donohue, David; Aigner, Helmut; Tamborini, Gabriele; Bildstein, Olivier; Betti, Maria

    2005-08-01

    Physical, chemical, and isotopic analyses of individual radioactive and other particles in the micron-size range, key tools in environmental research and in nuclear forensics, require the ability to precisely relocate particles of interest (POIs) in the secondary ion mass spectrometer (SIMS) or in another instrument, after having been located, identified, and characterized in the scanning electron microscope (SEM). This article describes the implementation, testing, and evaluation of the triangulation POIs re-location method, based on microscopic reference marks imprinted on or attached to the sample holder, serving as an inherent coordinate system. In SEM-to-SEM and SEM-to-SIMS experiments re-location precision better than 10 [mu]m and 20 [mu]m, respectively, is readily attainable for instruments using standard specimen stages. The method is fast, easy to apply, and facilitates repeated analyses of individual particles in different instruments and laboratories.

  1. A doublet microlens array for imaging micron-sized objects

    PubMed Central

    Tripathi, A; Chronis, N

    2011-01-01

    We present a high-numerical aperture, doublet microlens array for imaging micron-sized objects. The proposed doublet architecture consists of glass microspheres trapped on a predefined array of silicon microholes and covered with a thin polymer layer. A standard silicon microfabrication process and a novel fluidic assembly technique were combined to obtain an array of 56 μm diameter microlenses with a numerical aperture of ~0.5. Using such an array, we demonstrated brightfield and fluorescent image formation of objects directly on a CCD sensor without the use of intermediate lenses. The proposed technology is a significant advancement toward the unmet need of inexpensive, miniaturized optical modules which can be further integrated with lab-on-chip microfluidic devices and photonic chips for a variety of high-end imaging/detection applications. PMID:22003271

  2. Nanoscale patterns on micron-sized bubbles in foams

    NASA Astrophysics Data System (ADS)

    Dressaire, Emilie; Bell, David; Bee, Rodney; Lips, Alex; Stone, Howard

    2006-11-01

    The rheology and coarsening of foams is closely related to the microstructural characteristics of the small gas bubbles and their surface properties. We present experimental results of a foam formed upon shearing a mixture composed of glucose syrup and sucrose ester. Transmission Electron Microscopy reveals micron-size bubbles whose surfaces are fully covered with regular nanodimension, generally hexagonal, patterns. The influence of the shear rate during foam generation and the setting time on the development of the nanoscale patterns on the gas microcells are described. Plausible routes, driven by disproportionation of the gas from the small bubbles, for the formation of the nanoscale patterns are considered including a nucleation/crystallization pathway (Kim et al. 2003 Langmuir 19, p. 8455) and the buckling of an elastic insoluble surface film.

  3. TIMMI, ESO's new 10 micron Camera/Spectrometer

    NASA Astrophysics Data System (ADS)

    Kaeufl, H. U.; Jouan, R.; Lagage, P. O.; Masse, P.; Mestreau, P.; Tarrius, A.

    TIMMI stands for Thermal Infrared Multi Mode Instrument. TIMMI allows for imaging (at present 16 filters available) with variable magnifications as well as limited long-slit spectroscopy in the 10micron atmospheric window. The instrument was built by the Service d'Astrophysique (SAP) according to ESO's specification in a period of two years. At the telescope the instrument is using the f35 chopping configuration in conjunction with the special adaptor unit. TIMMI control and primary data-acquisition is performed by an VME-based computer (under OS9) while final data storage and online data processing with ESO's image processing system MIDAS is done using an UNIX workstation. While TIMMI will provide new observational possibilities for the ESO users community it is also supposed to become a test-bed to gain experience for similar instrumentation at the VLT.

  4. Passive athermalization of doublets in 8-13 micron waveband

    NASA Astrophysics Data System (ADS)

    Schuster, Norbert

    2014-10-01

    Passive athermalization of lenses has become a key-technology for automotive and other outdoor applications using modern uncooled 25, 17 and 12 micron pixel pitch bolometer arrays. Typical pixel counts for thermal imaging are 384x288 (qVGA), 640x480 (VGA), and 1024x768 (XGA). Two lens arrangements (called Doublets) represent a cost effective way to satisfy resolution requirements of these detectors with F-numbers 1.4 or faster. Thermal drift of index of refraction and the geometrical changes (in lenses and housing) versus temperature defocus the initial image plane from the detector plane. The passive athermalization restricts this drop of spatial resolution in a wide temperature range (typically -40°C…+80°C) to an acceptable value without any additional external refocus. In particular, lenses with long focal lengths and high apertures claim athermalization. A careful choice of lens and housing materials and a sophistical dimensioning lead to three different principles of passivation: The Passive Mechanical Athermalization (PMA) shifts the complete lens cell, the Passive Optical and Mechanical Athermalization (POMA) shifts only one lens inside the housing, the Passive Optical Athermalization (POA) works without any mechanism. All three principles will be demonstrated for a typical narrow-field lens (HFOV about 12°) with high aperture (aperture based F-number 1.3) for the actual uncooled reference detector (17micron VGA). Six design examples using different combinations of lens materials show the impact on spatial lens resolution, on overall length, and on weight. First order relations are discussed. They give some hints for optimization solutions. Pros and cons of different passive athermalization principles are evaluated in regards of housing design, availability of materials and costing. Examples with a convergent GASIR®1-lens in front distinguish by best resolution, short overall length, and lowest weight.

  5. The 11 micron Silicon Carbide Feature in Carbon Star Shells

    NASA Technical Reports Server (NTRS)

    Speck, A. K.; Barlow, M. J.; Skinner, C. J.

    1996-01-01

    Silicon carbide (SiC) is known to form in circumstellar shells around carbon stars. SiC can come in two basic types - hexagonal alpha-SiC or cubic beta-SiC. Laboratory studies have shown that both types of SiC exhibit an emission feature in the 11-11.5 micron region, the size and shape of the feature varying with type, size and shape of the SiC grains. Such a feature can be seen in the spectra of carbon stars. Silicon carbide grains have also been found in meteorites. The aim of the current work is to identity the type(s) of SiC found in circumstellar shells and how they might relate to meteoritic SiC samples. We have used the CGS3 spectrometer at the 3.8 m UKIRT to obtain 7.5-13.5 micron spectra of 31 definite or proposed carbon stars. After flux-calibration, each spectrum was fitted using a chi(exp 2)-minimisation routine equipped with the published laboratory optical constants of six different samples of small SiC particles, together with the ability to fit the underlying continuum using a range of grain emissivity laws. It was found that the majority of observed SiC emission features could only be fitted by alpha-SiC grains. The lack of beta-SiC is surprising, as this is the form most commonly found in meteorites. Included in the sample were four sources, all of which have been proposed to be carbon stars, that appear to show the SiC feature in absorption.

  6. Mass Spectrometry of Atmospheric Aerosol: 1 nanometer to 1 micron

    NASA Astrophysics Data System (ADS)

    Worsnop, D. R.; Ehn, M.; Junninen, H.; Kulmala, M. T.

    2010-12-01

    The role of aerosol particles remains the largest uncertainty in quantitatively assessing past, current and future climate change. The principal reason for that uncertainty arises from the need to characterize and model composition and size dependent aerosol processes, ranging from nanometer to micron scales. Aerosol mass spectrometry results have shown that about half the sub-micron aerosol composition is composed of highly oxygenated organics that are not well understood in terms of photochemical reaction mechanisms (Jimenez et al, 2009). This work has included application of high resolution time-of-flight mass spectrometry (ToFMS) in order to determine elemental and functional group composition of complex organic components. Recently, we have applied similar ToFMS to determine the composition of ambient ions, molecules and clusters, potentially involved in formation and growth of nano-particles (Junninen et al, 2010). Observed organic anions (molecular weight range 200-500 Th) have similar chemical composition as the least volatile secondary organics observed in fine particles; while organic cations are dominated by amines and pyridines. During nucleation events, anions are dominated by sulphuric acid cluster ions (Ehn et al, 2010). In both nanometer and micrometer size ranges, the goal to elucidate the roles of inorganic and organic species, particularly how particle evolution and physical properties depend on mixed compositions. Recent results will be discussed, including ambient and experimental chamber observations. Ehn et al, Atmos. Chem. Phys. Discuss., 10, 14897-14946, 2010 Jimenez et al, Science, 326, 1525-1529, 2009 Junninen et al, Atmos. Meas. Tech., 3, 1039-1053, 2010

  7. Imaging variations in the central Andean mantle and the subducting Nazca slab with teleseismic tomography

    NASA Astrophysics Data System (ADS)

    Scire, Alissa

    The Nazca-South America convergent margin is marked by the presence of the Andean mountain belt, which stretches along the 8000-km long western margin of the South American plate. The subduction zone is characterized by significant along-strike changes in both upper plate structure and slab geometry that make it an ideal region to study the relationship between the subducting slab, the surrounding mantle, and the overriding plate. This dissertation summarizes the results of three finite frequency teleseismic tomography studies of the central Nazca-South America subduction zone which improve our understanding of how along-strike variations in the Andean mountain belt and the subducting Nazca plate interact with each other and with the surrounding mantle. This is accomplished by first focusing on two smaller adjacent regions of the central Andes to explore upper mantle variations and then by using a combined dataset, which covers a larger region, to image the deeply subducted Nazca slab to investigate the fate of the slab. The first study focuses on the central Andean upper mantle under the Altiplano-Puna Plateau where normally dipping subduction of the Nazca plate is occurring (18° to 28°S). The shallow mantle under the Eastern Cordillera is generally fast, consistent with either underthrusting of the Brazilian cratonic lithosphere from the east or a localized "curtain" of delaminating material. Additional evidence for delamination is seen in the form of high amplitude low velocities under the Puna Plateau, consistent with proposed asthenospheric influx following lithospheric removal. In the second study, we explore the transition between normal and flat subduction along the north edge of the Altiplano Plateau (8° to 21°S). We find that the Peruvian flat slab extends further inland along the projection of the Nazca Ridge than was previously proposed and that when re-steepening of the slab occurs, the slab dips very steeply (˜70°) down through the mantle

  8. Efficient exhumation of (ultra) high-pressure rocks by slab extraction

    NASA Astrophysics Data System (ADS)

    Zhao, Zhongbao; Bons, Paul; Gomez-Rivas, Enrique; Soesoo, Alvar; Evgueni, Burov

    2015-04-01

    A range of mechanisms has been proposed for the enigmatic exhumation of (ultra) high-pressure (UHP) rocks from great depths. These include channel flow, wedge extrusion, diapiric rise, metamorphic core complexes and eduction. Most current models envisage exhumation to occur in a subduction setting, where exhumation of UHP rocks takes place in the context of the downward movement of the subducting slab. In addition, removal of the downward pull on the subducting slab (by slab break-off and slab retreat) may lead to buoyant rise of the UHP material, especially in case of subduction of continental crust. Here we consider the alternative scenario of slab extraction, where subduction is reversed and the slab is pulled up and away from the overriding plate, instead of sliding down into the mantle. UHP rocks are then exhumed together with the ascending plate. Slab extraction occurs when the downward pull of the subducted slab is exceeded by an opposite force, for example in case of plate divergence. Another case is a divergent double subduction zone (DDSZ), where the two hinges inevitably converge by rollback. At some point the pull of one slab can exceed that of the other one if it is short enough, leading to the extraction of the shorter slab and concomitant exhumation of UHP rocks. The evolution of a DDSZ with one short slab was modelled with the thermo-mechanical code FLAMAR, varying the relative movement of the two overriding plates. If the two overriding plates do not converge too fast, the short slab is pulled up and away from its suture and is eventually pulled down at the opposite suture. UHP rocks are exhumed at rates exceeding cms/yr in what is effectively a lithospheric-scale core complex. This mechanism may explain the exhumation of UHP rocks in the Tibetan Qiangtang Metamorphic Belt and the d'Entercasteaux Islands. If the sutures converge slower than the long slab slides down, an oceanic basin forms, which we suggest is the cause for the rapid opening of the

  9. Investigation of compressive membrane action in ultra high performance concrete slab strips

    NASA Astrophysics Data System (ADS)

    Foust, Bradley Wade

    Reinforced concrete slabs are found in very common structural systems in both civilian and military applications. The boundary conditions that support the slab play an important role in the response to a particular load. Specifically, the amount of lateral and rotational restraint dictates how a slab responds to a particular load. Compressive membrane (i.e., in-plane) forces are present in slabs when the boundaries are sufficiently stiff, therefore restricting the slab from both lateral translations and rotations. Advancements have been made to account for the additional capacity due to compressive membrane forces in conventional strength concrete. In today's world, concrete performance is improving because of increasing compressive strengths and additional ductility present in concrete members. As a result of this current improvement, there is an urgent need to investigate compressive membrane theory in ultra-high-performance concrete (UHPC) slabs to better understand their behavior. Existing compressive membrane theory should be revisited to determine if current theory is applicable, or if it is not, what modifications should be made. This study will provide insight into the validity of existing theory that is currently used to predict the ultimate capacity in conventional-strength concrete slabs and attempt to modify the existing equations to account for high-strength concrete materials. A matrix of 14 normal-strength concrete (NSC) and 13 UHPC slabs was tested both statically and dynamically to better understand the behavior of each material set and the effects that boundary conditions have on slab response. The results from these experiments were then compared to response calculations made from existing theory as well as finite element analyses. Valuable data sets on rigidly restrained UHPC slab response were obtained through an experimental research program. The experiments helped to validate the associated numerical analysis that was performed. It was

  10. Bidirectional reflectance measurement of zinc oxide in 0.25 to 2.5 microns spectrum

    NASA Technical Reports Server (NTRS)

    Scott, R. L., Jr.

    1974-01-01

    An experimental apparatus was designed and used to measure the bidirectional reflectance of zinc oxide in the spectrum 0.25 to 2.5 microns. The nonspecular reflectance is essentially Lambert for wavelengths above 0.40 microns with the most deviation occuring for large source zenith angles. Below 0.400 microns the nonspecular reflectance is greater than Lambert in all directions and is greatest in the forward and backscatter directions. The ratio of the specular component to the nonspecular component at a zenith of 0 degrees was found to increase with source zenith and wavelength for wavelengths above 0.400 microns. Below 0.400 microns this ratio increases as wavelengths decrease. The variation of bidirectional reflectance with wavelength was found to have the characteristics absorption for Zn0 for wavelength below 0.400 microns.

  11. Elasticity of superhydrous phase B, seismic anomalies in cold slabs and implications for deep water transport

    NASA Astrophysics Data System (ADS)

    Rosa, Angelika D.; Sanchez-Valle, Carmen; Wang, Jingyun; Saikia, Ashima

    2015-06-01

    Seismic anomalies in the vicinity of cold slabs, including low velocity zones and enhanced seismic shear wave splitting have been commonly attributed to the presence of hydrated slab material. The dense hydrous magnesium silicate (DHMS) superhydrous phase B (ShyB, Mg10Si3H4O18) is considered an important water carrier to transition zone depth due to its large pressure stability and abundance (up to 20 vol.%) in hydrous peridotites. To interpret the observed seismic anomalies in terms of hydration and to assess the role of ShyB in deep water recycling, we have investigated the sound velocities and single-crystal elasticity of ShyB to pressures of 17.5 GPa at ambient temperature by Brillouin scattering spectroscopy in diamond anvil cells. The Voigt-Reuss-Hill averages for the adiabatic bulk moduli KS, shear moduli μ and their pressure derivatives yield KS = 150(2) GPa, μ = 99(1) GPa, (∂KS/∂P) = 4.7(2) and (∂μ/∂P) = 1.44(5). The aggregate compressional and shear wave velocities of ShyB at transition zone pressures are comparable to those of hydrous iron-bearing ringwoodite but are significantly lower than anhydrous phases in peridotites. The calculated velocity contrast between dry and ShyB-bearing hydrous peridotite (containing 1.2 wt.% of water) indicate that 17 vol.% of ShyB decreases both compressional VP and shear VS wave velocities by at most 2.5% at transition zone depths. Our results, combined with data for the deformation mechanisms of ShyB, indicate that ShyB aggregates develop strong textures under down-dip compression regime and yield a maximum shear wave splitting of 1.1% in the plane perpendicular to the compression axis at 17.5 GPa. Although ShyB in hydrous subducted peridotite would reduce its seismic velocities, the splitting geometry VSV > VSH generated by ShyB fabrics in peridotite is incompatible with the pattern observed in Tonga and Sangihe, and would require the contribution of other phases to be explained. Textured phase D is a

  12. Coherent laser radar at 2 microns using solid-state lasers

    NASA Technical Reports Server (NTRS)

    Henderson, Sammy W.; Suni, Paul J. M.; Hale, Charley P.; Hannon, Stephen M.; Magee, James R.; Bruns, Dale L.; Yuen, Eric H.

    1993-01-01

    Coherent laser radar systems using 2-micron Tm- and Tm, Ho-doped solid-state lasers are useful for the remote range-resolved measurement of atmospheric winds, aerosol backscatter, and DIAL measurements of atmospheric water vapor and CO2 concentrations. Recent measurements made with a 2-micron coherent laser radar system, advances in the laser technology, and atmospheric propagation effects on 2-micron coherent lidar performance are described.

  13. Tears in subducting slabs: Examples from central Mexico and southern Peru

    NASA Astrophysics Data System (ADS)

    Dougherty, S. L.; Clayton, R. W.

    2013-12-01

    Slab tears are tectonically important morphological features of subducted plates that have been proposed to occur in numerous subduction zones. We examine the transitions from flat to normal subduction that occur in central Mexico and southern Peru for seismic evidence of such proposed tearing. The fine-scale seismic structure of these subduction zones is studied using moderate-sized (M4-6) intraslab earthquakes. Regional waveforms from temporary and permanent seismic arrays are complicated and contain detailed information about the subduction zone structure, including evidence of lateral heterogeneity, which is used to model the structure of the subducted plates. The lateral extent of a thin ultra-slow velocity layer (USL) imaged atop the Cocos slab in central Mexico in recent studies and evident atop the Nazca slab in southern Peru is mapped and examined for its relationship to the possible slab tears in each region. In central Mexico, there are two transitions from flat to normal subduction located in the west and east, respectively. In the west, recent tectonic studies have shown evidence for possible slab tearing along the projection of the Orozco Fracture Zone (OFZ), while in the east, observations of a sudden change in slab dip coupled with the abrupt end of the Trans Mexican Volcanic Belt (TMVB) suggest a second possible slab tear. In the west, we find an edge to the USL which is coincident with the western boundary of the projected OFZ region. Forward modeling of the 2D structure of the subducted Rivera and Cocos plates using a finite-difference algorithm provides constraints on the velocity and geometry of each slab's seismic structure in this region and confirms the location of the USL edge. Coupled with the results of recent plate motion studies showing that the Cocos plate moves differently on either side of the OFZ, we propose that the Cocos slab is currently fragmenting into a North Cocos plate and a South Cocos plate along the projection of the OFZ

  14. Analysis of Distribution of Nonmetallic Inclusions in Aluminum DC-Cast Billets and Slabs

    NASA Astrophysics Data System (ADS)

    Jaradeh, Majed M.; Carlberg, Torbjorn

    2012-02-01

    Inclusion distribution was studied in commercial aluminum DC-cast billets and slabs using a newly developed deep-etching method. Analyses revealed a nonuniform distribution of nonmetallic inclusions across billet diameters and lengths, and also across slab thicknesses and widths. In as-cast billets, more inclusions were found at the beginning and end of the billet length; more were present near the cross-section center than near the surface. In slabs, inclusions were located mostly within 13 mm of the surface and in a band between the centerline and the surface. Few inclusions were found 60 to 100 mm from the slab surface or at the centerline. In addition, comparing slab quality after casting using three types of ceramic foam filters (CFFs; i.e., 30 ppi, 50 ppi, and 50 ppi + HF) revealed significant differences in inclusion size, number, and distribution. Casting slabs using a finer pore-size filter (50 ppi) reduced the number of non-metallic inclusions greatly. The inclusion distribution patterns observed in the solidified slabs are discussed in terms of melt flow during casting.

  15. Exploring the connection between intermediate-depth seismicity, slab hydration, and dehydration

    NASA Astrophysics Data System (ADS)

    Syracuse, E. M.; Pesicek, J. D.; Zhang, H.; Thurber, C. H.

    2013-12-01

    The dehydration of hydrous minerals has commonly been cited as the cause of intermediate-depth seismicity in subducted crust and mantle, through the process known as dehydration embrittlement. However, recent laboratory and empirical studies have called both the mechanism and seismological observation of this phenomenon into question. In order to assess the global relationship between seismicity, the presence of hydrous and dehydrating minerals, and the thermal state of slabs, we perform double-difference earthquake relocation of earthquakes at the majority of Earth's subduction zones, which reduces the scatter and improves the accuracy of the distributions of slab seismicity. The double-difference relocations are systematically calculated for each subduction zone in a version of the algorithm tomoDD that has been modified to include absolute and differential catalog P, S, and depth phase arrival times from local and teleseismic stations, as well as a three-dimensional global velocity model. Preliminary relocations demonstrate shifts of up to 15 km due to the use of a three-dimensional global velocity model. These relocations also illuminate various types of slab structures, including a range of slab morphologies, potential double seismic zones, and evidence of fault zones within slabs. At each subduction zone, these distributions are compared to previously published two-dimensional thermal and mineralogical models that have been calculated for that particular slab. The findings of these comparisons will be used to develop a set of slab conditions that describe where intermediate-depth seismicity is possible (and observed) at subduction zones.

  16. Seismic response to slab rupture and variation in lithospheric structure beneath the Savu Sea, Indonesia

    NASA Astrophysics Data System (ADS)

    Ely, Kim S.; Sandiford, Mike

    2010-03-01

    Variations in seismic moment release and stress state across the transition from subduction of oceanic crust to arc-continent collision in the Banda Arc are constrained by focal mechanism solutions from the CMT earthquake catalogue. In particular the slab under the western Savu Sea is unusual in that intermediate depth (70-300 km) events indicate that at this depth range the slab is largely in down-dip compression. This contrasts with the intermediate depth, down-dip tension that typifies the Sunda slab to the west and the far eastern Banda slab to the east. Down-dip compression beneath the Savu Sea reflects subduction of transitional crust of the Scott Plateau, more buoyant than the Indian Ocean crust subducting further west. In this region, enhanced magma flux is indicated by unusually narrow volcano spacing in the overlying arc, and suggests that down-dip compression reflects not only more buoyant transitional crust but also a reduction in slab-wedge coupling induced by enhanced magma flux. East of the Savu Sea, the near complete absence of intermediate depth seismicity is attributed to a slab window that has opened where Australian continental crust has collided with the arc. Differences in seismic moment release around this slab window indicate asymmetric rupture, propagating to the east at a much faster rate than to the west.

  17. Surface deformation and slab-mantle interaction during Banda arc subduction rollback

    NASA Astrophysics Data System (ADS)

    Spakman, Wim; Hall, Robert

    2010-08-01

    The spectacularly curved Banda arc comprises young oceanic crust enclosed by a volcanic inner arc, outer arc islands and a trough parallel to the Australian continental margin. Strong seismic activity in the upper mantle defines a folded surface, for which there are two contrasting explanations: deformation of a single slab or two separate slabs subducting from the north and south. Here we combine seismic tomography with the plate tectonic evolution of the region to infer that the Banda arc results from subduction of a single slab. Our palaeogeographic reconstruction shows that a Jurassic embayment, which consisted of dense oceanic lithosphere enclosed by continental crust, once existed within the Australian plate. Banda subduction began about 15million years ago when active Java subduction tore eastwards into the embayment. The present morphology of the subducting slab is only partially controlled by the shape of the embayment. As the Australian plate moved northward at a high speed of about 7cmyr-1, the Banda oceanic slab rolled back towards the south-southeast accompanied by active delamination separating the crust from the denser mantle. Increasing resistance of the mantle to plate motion progressively folded the slab and caused strong deformation of the crust. The Banda arc represents an outstanding example of large-scale deformation of the Earth's crust in response to coupling between the crust, slab and surrounding mantle.

  18. The Effect of Mortar Grade and Thickness on the Impact Resistance of Ferrocement Slab

    NASA Astrophysics Data System (ADS)

    Che Muda, Zakaria; Syamsir, Agusril; Nasharuddin Mustapha, Kamal; Sulleman, Sorefan; Beddu, Salmia; Thiruchelvam, Sivadass; Ismail, Firas B.; Usman, Fathoni; Liyana Mohd Kamal, Nur; Ashraful Alam, Md; Birima, Ahmed H.; Itam, Zarina; Zaroog, O. S.

    2016-03-01

    This paper investigate the effect of the thickness and mesh spacing on the impact of ferrocement for the concrete slab of 300mm × 300mm size reinforced subjected to low impact projectile test. A self-fabricated drop-weight impact test rig with a steel ball weight of 1.236 kg drop at height of 150 mm, 350mm, and 500mm has been used in this research work. The objective of this research is to study the relationship of impact resistance of ferrocement against the mortar grade and slab thickness. There is a good linear correlation between impact resistance of ferrocement against the mortar grade and the thickness of ferrocement slab. The first and ultimate crack impact resistance of mortar grade 43 (for 40 mm thick slab with mesh reinforcement) are 1.60 times and 1.53 times respectively against the mortar grade 17 slab (of same thickness with mesh reinforcement). The first and ultimate crack impact resistance for 40 mm thick slab (mortar grade 43 with mesh reinforcement) are 3.55 times and 4.49 times respectively against the 20 mm thick slab (of same mortar grade with mesh reinforcement).

  19. Construction of a polarization insensitive lens from a quasi-isotropic metamaterial slab

    NASA Astrophysics Data System (ADS)

    Luo, Hailu; Ren, Zhongzhou; Shu, Weixing; Li, Fei

    2007-02-01

    We propose to employ the quasi-isotropic metamaterial (QIMM) slab to construct a polarization insensitive lens, in which both E - and H -polarized waves exhibit the same refocusing effect. For shallow incident angles, the QIMM slab will provide some degree of refocusing in the same manner as an isotropic negative index material. The refocusing effect allows us to introduce the ideas of paraxial beam focusing and phase compensation by the QIMM slab. On the basis of angular spectrum representation, a formalism describing paraxial beams propagating through a QIMM slab is presented. Because of the negative phase velocity in the QIMM slab, the inverse Gouy phase shift and the negative Rayleigh length of paraxial Gaussian beam are proposed. We find that the phase difference caused by the Gouy phase shift in vacuum can be compensated by that caused by the inverse Gouy phase shift in the QIMM slab. If certain matching conditions are satisfied, the intensity and phase distributions at object plane can be completely reconstructed at image plane. Our simulation results show that the superlensing effect with subwavelength image resolution could be achieved in the form of a QIMM slab.

  20. Meteorological variables associated with deep slab avalanches on persistent weak layers

    USGS Publications Warehouse

    Marienthal, Alex; Hendrikx, Jordy; Birkeland, Karl; Irvine, Kathryn M.

    2014-01-01

    Deep slab avalanches are a particularly challenging avalanche forecasting problem. These avalanches are typically difficult to trigger, yet when they are triggered they tend to propagate far and result in large and destructive avalanches. For this work we define deep slab avalanches as those that fail on persistent weak layers deeper than 0.9m (3 feet), and that occur after February 1st. We utilized a 44-year record of avalanche control and meteorological data from Bridger Bowl Ski Area to test the usefulness of meteorological variables for predicting deep slab avalanches. As in previous studies, we used data from the days preceding deep slab cycles, but we also considered meteorological metrics over the early months of the season. We utilized classification trees for our analyses. Our results showed warmer temperatures in the prior twenty-four hours and more loading over the seven days before days with deep slab avalanches on persistent weak layers. In line with previous research, extended periods of above freezing temperatures led to days with deep wet slab avalanches on persistent weak layers. Seasons with either dry or wet avalanches on deep persistent weak layers typically had drier early months, and often had some significant snow depth prior to those dry months. This paper provides insights for ski patrollers, guides, and avalanche forecasters who struggle to forecast deep slab avalanches on persistent weak layers late in the season.

  1. High-quality slab-based intermixing method for fusion rendering of multiple medical objects.

    PubMed

    Kim, Dong-Joon; Kim, Bohyoung; Lee, Jeongjin; Shin, Juneseuk; Kim, Kyoung Won; Shin, Yeong-Gil

    2016-01-01

    The visualization of multiple 3D objects has been increasingly required for recent applications in medical fields. Due to the heterogeneity in data representation or data configuration, it is difficult to efficiently render multiple medical objects in high quality. In this paper, we present a novel intermixing scheme for fusion rendering of multiple medical objects while preserving the real-time performance. First, we present an in-slab visibility interpolation method for the representation of subdivided slabs. Second, we introduce virtual zSlab, which extends an infinitely thin boundary (such as polygonal objects) into a slab with a finite thickness. Finally, based on virtual zSlab and in-slab visibility interpolation, we propose a slab-based visibility intermixing method with the newly proposed rendering pipeline. Experimental results demonstrate that the proposed method delivers more effective multiple-object renderings in terms of rendering quality, compared to conventional approaches. And proposed intermixing scheme provides high-quality intermixing results for the visualization of intersecting and overlapping surfaces by resolving aliasing and z-fighting problems. Moreover, two case studies are presented that apply the proposed method to the real clinical applications. These case studies manifest that the proposed method has the outstanding advantages of the rendering independency and reusability.

  2. Low electrical resistivity associated with plunging of the Nazca flat slab beneath Argentina.

    PubMed

    Booker, John R; Favetto, Alicia; Pomposiello, M Cristina

    2004-05-27

    Beneath much of the Andes, oceanic lithosphere descends eastward into the mantle at an angle of about 30 degrees (ref. 1). A partially molten region is thought to form in a wedge between this descending slab and the overlying continental lithosphere as volatiles given off by the slab lower the melting temperature of mantle material. This wedge is the ultimate source for magma erupted at the active volcanoes that characterize the Andean margin. But between 28 degrees and 33 degrees S the subducted Nazca plate appears to be anomalously buoyant, as it levels out at about 100 km depth and extends nearly horizontally under the continent. Above this 'flat slab', volcanic activity in the main Andean Cordillera terminated about 9 million years ago as the flattening slab presumably squeezed out the mantle wedge. But it is unknown where slab volatiles go once this happens, and why the flat slab finally rolls over to descend steeply into the mantle 600 km further eastward. Here we present results from a magnetotelluric profile in central Argentina, from which we infer enhanced electrical conductivity along the eastern side of the plunging slab, indicative of the presence of partial melt. This conductivity structure may imply that partial melting occurs to at least 250 km and perhaps to more than 400 km depth, or that melt is supplied from the 410 km discontinuity, consistent with the transition-zone 'water-filter' model of Bercovici and Karato.

  3. Sustained delivery of chondroitinase ABC by poly(propylene carbonate)-chitosan micron fibers promotes axon regeneration and functional recovery after spinal cord hemisection.

    PubMed

    Ni, Shilei; Xia, Tongliang; Li, Xingang; Zhu, Xiaodong; Qi, Hongxu; Huang, Shanying; Wang, Jiangang

    2015-10-22

    We describe the sustained delivery of chondroitinase ABC (ChABC) in the hemisected spinal cord using polypropylene carbonate (PPC) electrospun fibers with chitosan (CS) microspheres as a vehicle. PPC and ChABC-loaded CS microspheres were mixed with acetonitrile, and micron fibers were generated by electrospinning. ChABC release was assessed in vitro with high-performance liquid chromatography (HPLC) and revealed stabilized and prolonged release. Moreover, the released ChABC showed sustained activity. PPC-CS micron fibers with or without ChABC were then implanted into a hemisected thoracic spinal cord. In the following 4 weeks, we examined functional recovery and performed immunohistochemical analyses. We found that sustained delivery of ChABC promoted axon sprouting and functional recovery and reduced glial scarring; PPC-CS micron fibers without ChABC did not show these effects. The present findings suggest that PPC-CS micron fibers containing ChABC are a feasible option for spinal cord injury treatment. Furthermore, the system described here may be useful for local delivery of other therapeutic agents. PMID:26315376

  4. Evaluation of micron size carbon fibers released from burning graphite composites

    NASA Technical Reports Server (NTRS)

    Sussholz, B.

    1980-01-01

    Quantitative estimates were developed of micron carbon fibers released during the burning of graphite composites. Evidence was found of fibrillated particles which were the predominant source of the micron fiber data obtained from large pool fire tests. The fibrillation phenomena were attributed to fiber oxidation effects caused by the fire environment. Analysis of propane burn test records indicated that wind sources can cause considerable carbon fiber oxidation. Criteria estimates were determined for the number of micron carbon fibers released during an aircraft accident. An extreme case analysis indicated that the upper limit of the micron carbon fiber concentration level was only about half the permissible asbestos ceiling concentration level.

  5. Spatial variations of the 3-micron emission features within Orion's Bar

    NASA Technical Reports Server (NTRS)

    Moorhouse, A.; Brand, P. W. J. L.; Geballe, T. R.; Allamandola, L. J.; Tielens, A. G. G. M.

    1988-01-01

    3-micron spectra of the Orion Bar region have been obtained at three positions corresponding to different distances from the exciting source. The recently discovered unidentified features at 3.46, 3.51, and 3.57 microns are clearly visible. The spectra show that the 3.4 and 3.51-micron emission features increase in intensity relative to the strong 3.3-micron feature as the distance from the exciting source increases. The implications for polycyclic aromatic hydrocarbons and recent ideas concerning their ultraviolet excitation and spatial evolution are discussed.

  6. Airborne spectrophotometry of P/Halley from 16 to 30 microns

    NASA Technical Reports Server (NTRS)

    Herter, T.; Gull, G. E.; Campins, H.

    1986-01-01

    Comet Halley was observed in the 16 to 30 micron region using the Cornell University 7-channel spectrometer (resolution = 0.02) on board the Kuiper Airborne Observatory on 1985 Dec. 14.2. A 30-arcsec aperture (FWHM) was used. Measurements centered on the nuclear condensation micron indicate that if present, the 20 micron silicate feature is very weak, and that a relatively narrow strong feature centered at 28.4 microns possibly exists. However, this feature may be an artifact of incomplete correction for telluric water vapor absorption.

  7. Simulation of late Cenozoic South American flat-slab subduction using geodynamic models with data assimilation

    NASA Astrophysics Data System (ADS)

    Hu, Jiashun; Liu, Lijun; Hermosillo, Armando; Zhou, Quan

    2016-03-01

    The formation mechanisms of flat slabs in South America remain unclear. To quantitatively evaluate the earlier proposed mechanisms, we simulate the post-100 Ma subduction history below South America using 4-D geodynamic models by progressively incorporating plate kinematics, seafloor ages and key tectonic features including the buoyant oceanic crust, continental cratons, oceanic plateaus (i.e. the inferred Inca plateau, subducting Nazca Ridge and Juan Fernandez Ridge), as well as deformable trench profiles according to recent geological reconstructions. We find that, in the absence of an overriding plate and subducting buoyancy features, the seafloor age affects slab dip angle by controlling the slab's mechanical strength (i.e., the resistance to bending) and negative buoyancy (integrated positive density anomaly that enhances bending). Our models show that slab strength dominates its buoyancy at age >30 Ma and the opposite for younger ages. The existence of a thick overriding plate reduces the slab dip by increasing dynamic suction, and individual cratonic roots further lead to along-trench variations of dip angle reduction. While dynamic suction from the overriding plate generates a permanent reduction of the long-wavelength slab dip angle, it is the final addition of subducting oceanic plateau and aseismic ridges that produces the transient and localized flat-slabs as observed. These results suggest that all mechanisms except the buoyancy features affect the slab dip only at large spatial scales. Our best-fit model with all the above tectonic features included provides a good match to both the upper mantle Benioff zones and the temporal evolution of volcanic arcs since the mid-Miocene. The imperfect match of the Peruvian flat-slab is likely associated with the uncertain 3-D configuration of the Amazonian craton.

  8. Boron-isotope systematics of Halmahera arc (Indonesia) lava: Evidence for involvement of the subducted slab

    SciTech Connect

    Palmer, M.R. )

    1991-03-01

    Dehydration of sediments and oceanic crust within the subducting slab at convergent plate margins is probably a ubiquitous feature. This leads to fractionation of elements between fluids and solids so that the slab-derived component of island-arc lavas is modified from the originally subducted material. Sediments and altered oceanic crust are enriched in boron and cesium relative to uncontaminated mantle products, and these elements are highly mobile during fluid-rock interaction. The combination of B-isotope systematics and Cs concentrations in lavas from the Halmahera arc (Indonesia) suggests that they have been influenced by fluids derived from dehydration and/or melting of the subducted slab.

  9. Software Analytical Instrument for Assessment of the Process of Casting Slabs

    SciTech Connect

    Franek, Zdenek; Kavicka, Frantisek; Stetina, Josef; Masarik, Milos

    2010-06-15

    The paper describes the original proposal of ways of solution and function of the program equipment for assessment of the process of casting slabs. The program system LITIOS was developed and implemented in EVRAZ Vitkovice Steel Ostrava on the equipment of continuous casting of steel (further only ECC). This program system works on the data warehouse of technological parameters of casting and quality parameters of slabs. It enables an ECC technologist to analyze the course of casting melt and with using statistics methods to set the influence of single technological parameters on the duality of final slabs. The system also enables long term monitoring and optimization of the production.

  10. Experimental and numerical investigation of slabs on ground subjected to concentrated loads

    NASA Astrophysics Data System (ADS)

    Øverli, Jan

    2014-09-01

    An experimental program is presented where a slab on ground is subjected to concentrated loading at the centre, the edges and at the corners. Analytical solutions for the ultimate load capacity fit well with the results obtained in the tests. The non-linear behaviour of the slab is captured by performing nonlinear finite element analyses. The soil is modelled as a no-tension bedding and a smeared crack approach is employed for the concrete. Through a parametric study, the finite element model has been used to assess the influence of subgrade stiffness and shrinkage. The results indicate that drying shrinkage can cause severe cracking in slabs on grade.

  11. Out-of-plane resonances in terahertz photonic crystal slabs modulated by optical pumping.

    PubMed

    Shi, Yulei; Zhou, Qing-Li; Liu, Wei; Zhang, Cunlin

    2011-10-10

    This paper describes detailed optical-pump-terahertz-probe studies of two-dimensional photonic crystal slabs for propagation perpendicular to the slabs. When the slabs are excited by an 800 nm pump pulse and the effect of shielding by photocarriers is removed, we find that the decaying tail in the transmitted terahertz radiation is strikingly enhanced. The photocarriers weaken guided resonances, but they also greatly enhance the excitation efficiency of guided resonances and the ability of the guided resonances to transfer energy back to the radiation field. This increases the resonance-assisted contribution to transmitted field. The photoinduced resonant extremes agree well with the Fano model. PMID:21997090

  12. A high speed profiler based slab curvature index for jointed concrete pavement curling and warping analysis

    NASA Astrophysics Data System (ADS)

    Byrum, Christopher Ronald

    One of the biggest gaps of missing knowledge between accurate structural modeling of concrete pavement slab behavior and real pavement behavior is accounting for slab warping (locked-in curvature and moisture gradient effects) and curling (temperature gradient effects). Curling and warping are curvatures that can be present in a PCC slab that can cause corners and edges, or mid panel, of the slab to lift off of the ground resulting in relatively high deflection and stress in the system. The least understood type of curvature in slabs is apparent locked-in curvature, which can become excessive and control the overall behavior of the pavement system. This project is focused on quantifying slab curvatures and the effects of apparent locked-in curvature on the behavior and long-term performance of pavement systems. A high-speed profile analysis technique for detecting the amount of slab curvatures along pavement wheel paths is described. This signal processing technique can detect relatively small curvature variations in high-speed pavement elevation profiles obtained at normal highway operating speeds using special vehicles. A resulting curvature detection algorithm is applied to the Federal Highway Administration (FHWA) Long Term Pavement Performance (LTPP) database high-speed pavement profiles for jointed concrete pavements. The range and nature of slab curvatures detected in the profiles is described. The calculated locked-in curvature at the various pavement sites is compared to LTPP database information to evaluate curvature effects on pavement deterioration rates and the relation between site parameters and locked-in curvature. The significance of slab curvature is shown through statistics and predictive models developed for various pavement distress modes. It is shown that the amount of curvature locked into concrete slabs is one of the strongest factors in the FHWA LTPP data correlated to deterioration of pavements. This study shows that preventing locked

  13. Investigation of complete bandgaps in a piezoelectric slab covered with periodically structured coatings.

    PubMed

    Zou, Kui; Ma, Tian-Xue; Wang, Yue-Sheng

    2016-02-01

    The propagation of elastic waves in a piezoelectric slab covered with periodically structured coatings or the so-called stubbed phononic crystal slab is investigated. Four different models are selected and the effects of distribution forms and geometrical parameters of the structured coatings on complete bandgaps are discussed. The phononic crystal slab with symmetric coatings can generate wider complete bandgaps while that with asymmetric coatings is favorable for the generation of multi-bandgaps. The complete bandgaps, which are induced by locally resonant effects, change significantly as the geometry of the coatings changes. Moreover, the piezoelectric effects benefit the opening of the complete bandgaps.

  14. INDEPENDENT VERIFICATION OF THE BUILDING 3550 SLAB AT OAK RIDGE NATIONAL LABORATORY OAK RIDGE, TENNESSEE

    SciTech Connect

    Weaver, Phyllis C.

    2012-05-08

    The Oak Ridge Institute for Science and Education (ORISE) has completed the independent verification survey of the Building 3550 Slab. The results of this effort are provided. The objective of this verification survey is to provide independent review and field assessment of remediation actions conducted by Safety and Ecology Corporation (SEC) to document that the final radiological condition of the slab meets the release guidelines. Verification survey activities on the Building 3550 Slab that included scans, measurements, and the collection of smears. Scans for alpha, alpha plus beta, and gamma activity identified several areas that were investigated.

  15. Selection of quasi-monodisperse super-micron aerosol particles

    NASA Astrophysics Data System (ADS)

    Rösch, Michael; Pfeifer, Sascha; Wiedensohler, Alfred; Stratmann, Frank

    2014-05-01

    Size-segregated quasi monodisperse particles are essential for e.g. fundamental research concerning cloud microphysical processes. Commonly a DMA (Differential Mobility Analyzer) is used to produce quasi-monodisperse submicron particles. Thereto first, polydisperse aerosol particles are bipolarly charged by a neutralizer, and then selected according to their electrical mobility with the DMA [Knutson et al. 1975]. Selecting a certain electrical mobility with a DMA results in a particle size distribution, which contains singly charged particles as well as undesired multiply charged larger particles. Often these larger particles need to either be removed from the generated aerosol or their signals have to be corrected for in the data inversion and interpretation process. This problem becomes even more serious when considering super-micron particles. Here we will present two different techniques for generating quasi-monodisperse super-micron aerosol particles with no or only an insignificant number of larger sized particles being present. First, we use a combination of a cyclone with adjustable aerodynamic cut-off diameter and our custom-built Maxi-DMA [Raddatz et al. 2013]. The cyclone removes particles larger than the desired ones prior to mobility selection with the DMA. This results in a reduction of the number of multiply charged particles of up to 99.8%. Second, we utilize a new combination of cyclone and PCVI (Pumped Counterflow Virtual Impactor), which is based on purely inertial separation and avoids particle charging. The PCVI instrument was previously described by Boulter et al. (2006) and Kulkarni et al. (2011). With our two setups we are able to produce quasi-monodisperse aerosol particles in the diameter range from 0.5 to 4.4 µm without a significant number of larger undesired particles being present. Acknowledgements: This work was done within the framework of the DFG funded Ice Nucleation research UnIT (INUIT, FOR 1525) under WE 4722/1-1. References

  16. Near-diffraction-limited green source by frequency doubling of a diode-stack pumped Q-switched Nd:YAG slab oscillator-amplifier system.

    PubMed

    Zhang, Hengli; Liu, Xiaomeng; Li, Daijun; Shi, Peng; Schell, Alex; Haas, Claus Rüdige; Du, Keming

    2007-09-10

    A near-diffraction-limited, stable, 18 mJ green source with a pulse width of 16.7 ns was generated at a 1 kHz repetition rate by frequency doubling of diode stacks end-pumped electro-optically Q-switched slab Nd:YAG oscillator-amplifier system. The pump to green optical conversion efficiency was 10.7%. At the output energy of 15 mJ at 532 nm, the M2 factors were 1.3 and 1.7 in the unstable and stable directions, respectively. The energy pulse stability was approximately 0.8%.

  17. Virtual Impactor for Sub-micron Aerosol Particles

    NASA Astrophysics Data System (ADS)

    Bolshakov, A. A.; Strawa, A. W.; Hallar, A. G.

    2005-12-01

    The objective of a virtual impactor is to separate out the larger particles in a flow from the smaller particles in such a way that both sizes of particles are available for sampling. A jet of particle-laden air is accelerated toward a collection probe so that a small gap exists between the acceleration nozzle and the probe. A vacuum is applied to deflect a major portion of the airstream away form the collection probe. Particles larger than a certain size have sufficient momentum so that they cross the deflected streamlines and enter the collection probe, whereas smaller particles follow the deflected streamlines. The result is that the collection probe will contain a higher concentration of larger particles than is in the initial airstream. Typically, virtual impactors are high-flow devices used to separate out particles greater than several microns in diameter. We have developed a special virtual impactor to concentrate aerosol particles of diameters between 0.5 to 1 micron for the purpose of calibrating the optical cavity ring-down instrument [1]. No similar virtual impactors are commercially available. In our design, we have exploited considerations described earlier [2-4]. Performance of our virtual impactor was evaluated in an experimental set-up using TSI 3076 nebulizer and TSI 3936 scanning mobility particle size spectrometer. Under experimental conditions optimized for the best performance of the virtual impactor, we were able to concentrate the 700-nm polystyrene particles no less than 15-fold. However, under experimental conditions optimized for calibrating our cavity ring-down instrument, a concentration factor attainable was from 4 to 5. During calibration experiments, maximum realized particle number densities were 190, 300 and 1600 cm-3 for the 900-nm, 700-nm and 500-nm spheres, respectively. This paper discusses the design of the impactor and laboratory studies verifying its performance. References: 1. A.W. Strawa, R. Castaneda, T. Owano, D.S. Baer

  18. Viewing Seasonality in 8 Megacities at 4 Microns

    NASA Astrophysics Data System (ADS)

    Tomaszewska, M. A.; Kovalskyy, V.; Small, C.; Henebry, G. M.

    2013-12-01

    The middle infrared (MIR) spectral region, between 3 and 5 microns, offers a different perspective on cities. The MIR is the mixing zone of both emitted terrestrial radiation and reflected solar radiation. The relatively long wavelengths enable views of surfaces often obscured by anthropogenic haze. Green vegetation appears very dark in the MIR due to high absorption by leaf water. In contrast, building, roofing, and paving materials reflect much MIR and exposed soils and dried vegetation reflect even more. Thus, physics dictates a strong expression of seasonality in the MIR. But is there sufficient signal in the MIR to merit it as a complementary approach for characterizing urbanized areas and monitoring their dynamics? We have explored this question in a research effort that links two NASA Interdisciplinary Science projects on the effect of cities on the environment. We focused on 8 global megacities: Beijing, Cairo, Istanbul, Mexico, Moscow, Nairobi, New Delhi, and São Paulo. We used Level 1B calibrated radiance data from band 23 (~4 microns) of the Aqua MODIS during ascending passes in 2010. These 1 km data were processed to reduce cloud cover using monthly maximum value compositing into four sensor view zenith angle (VZA) classes: 030°). SNR was higher in the summer

  19. Three-dimensional Numerical Models of Mantle Flow Through the Cocos-Nazca Slab Gap

    NASA Astrophysics Data System (ADS)

    Jadamec, M.; Fischer, K. M.

    2013-05-01

    Global slab geometry models suggest a 350 km to 1000 km spacing between the southern extent of the Cocos slab and the northern extent of the Nazca slab (Gudmundsson and Sambridge, 1998; Syracuse and Abers, 2006; Hayes et al., 2012). The apparent gap between the east-dipping Cocos and Nazca slabs at depth correlates to several tectonic features on the Pacific side of Central and northern South America that may limit subduction, namely the (a) Panama Fault zone, (b) incoming young lithosphere associated with the Cocos-Nazca spreading center, and (c) the Cocos, Coiba, Malpelo, and Carnegie ridges associated with the Galapogos hotspot and Cocos-Nazca spreading center (Protti et al., 1994; Johnston and Thorkelson, 1997; Gutscher et al., 1999; Abratis and Worner, 2001; Sdrolias and Muller, 2006; Mann et al., 2007; Gazel et al., 2011). In addition, on the Caribbean side of Central and northern South America, seismic data suggest that part of the Caribbean plate is subducting and dipping in a direction opposite to the Cocos and Nazca slabs (van der Hilst and Mann, 1994; Camacho et al., 2010). We construct high-resolution three-dimensional numerical models of the Cocos-Nazca subduction system to test the effects of a slab gap and variable overriding plate thickness on surface plate motion and mantle flow. The 3D tectonic configuration is generated with SlabGenerator (Jadamec and Billen, 2010, 2012) and the mantle convection code CitcomCU is used to solve for the viscous flow (Moresi and Solomatov, 1995; Zhong, 2006). The negative thermal buoyancy of the slabs drive the flow. No driving velocities are applied to the plates or any of the slabs in the model. The detailed geometries of the Cocos and Nazca slabs are constructed from seismicity and seismic tomography (Protti et al., 1994; Colombo et al., 1997; Gudmundsson and Sambridge, 1998; Rogers et al., 2002; Husen et al., 2003; Syracuse and Abers, 2006; Syracuse et al., 2008; Dzierma et al., 2011). Seismic tomography

  20. Analog Modeling of the Juan Fernández Ridge, Central Chile, and Implications for Flat-Slab Subduction Dynamics

    NASA Astrophysics Data System (ADS)

    Woodell, D.; Anderson, M. L.

    2009-12-01

    This study compares the strain experienced by the subducting lithosphere in analog models to the strain recorded by earthquakes in the subduction zone that includes the Juan Fernández Ridge (JFR), near 33 S, 73 W, off the coast of central Chile. The JFR is an aseismic hot spot ridge that has a thickened oceanic crust. The overthickened crust reduces the total density of the slab when compared to the surrounding slab areas, and thus increases the buoyancy of the subducting Nazca plate at this particular location. It is hypothesized that the Nazca plate experiences “flat-slab” subduction at the JFR subduction zone due to this buoyancy. Brudzinski and Chen (2005) argue that, due to the poorly aligned direction of maximum extension (T axes) for earthquakes in the subducting slab in flat-slab subduction zones, the theory of “slab pull” may not be valid for flat-slab subduction zones, and there must be other forces at work. However, Anderson et al. (2007) develop new, more precise slab contours from newly determined earthquake locations and use these contours to qualitatively compare the earthquake data to slab dip directions and thus expected slab-pull directions. They conclude that T axes are parallel to slab dip, and thus slab pull is the only force necessary for explaining the T axis direction. In this study, we quantitatively compare extension produced in analog "flat-slab" models in the laboratory to T axes from the Anderson et al. (2007) study, extending and further testing their idea. Several materials comprise the analog models. Light corn syrup represents the asthenosphere, while silicon putty represents the lithosphere. Recreating the dynamics of the buoyant JFR necessitates two different densities of silly putty: a denser one for the bulk of the slab, and a less dense one for the buoyant ridge. Shallow circular indentations (strain ellipses) on the slab facilitate recording of the strain in the subducting slab. Video and still pictures record each

  1. Scalable Sub-micron Patterning of Organic Materials Toward High Density Soft Electronics

    PubMed Central

    Kim, Jaekyun; Kim, Myung-Gil; Kim, Jaehyun; Jo, Sangho; Kang, Jingu; Jo, Jeong-Wan; Lee, Woobin; Hwang, Chahwan; Moon, Juhyuk; Yang, Lin; Kim, Yun-Hi; Noh, Yong-Young; Yun Jaung, Jae; Kim, Yong-Hoon; Kyu Park, Sung

    2015-01-01

    The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. In this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-μm-scale. The successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics. PMID:26411932

  2. Micron dimensioned cavity array supported lipid bilayers for the electrochemical investigation of ionophore activity.

    PubMed

    Maher, Sean; Basit, Hajra; Forster, Robert J; Keyes, Tia E

    2016-12-01

    Microcavity supported lipid bilayers, MSLBs, were applied to an electrochemical investigation of ionophore mediated ion transport. The arrays comprise of a 1cm(2) gold electrode imprinted with an ordered array of uniform spherical-cap pores of 2.8μm diameter prepared by gold electrodeposition through polystyrene templating spheres. The pores were pre-filled with aqueous buffer prior to Langmuir-Blodgett assembly of a 1,2-dioleoyl-sn-glycero-3-phosphocholine bilayer. Fluorescence lifetime correlation spectroscopy enabled by the micron dimensions of the pores permitted study of lipid diffusion across single apertures, yielding a diffusion coefficient of 12.58±1.28μm(2)s(-1) and anomalous exponent of 1.03±0.02, consistent with Brownian motion. From FLCS, the MSLBs were stable over 3days and electrochemical impedance spectroscopy of the membrane with and without ionic gradient over experimental windows of 6h showed excellent stability. Two ionophores were studied at the MSLBs; Valinomycin, a K(+) uniporter and Nigericin, a K(+)/H(+) antiporter. Ionophore reconstituted into the DOPC bilayer resulted in a decrease and increase in membrane resistance and capacitance respectively. Significant increases in Valinomycin and Nigericin activity were observed, reflected in large decreases in membrane resistance when K(+) was present in the contacting buffer and in the presence of H(+) ionic gradient across the membrane respectively. PMID:27420132

  3. Scalable sub-micron patterning of organic materials toward high density soft electronics

    DOE PAGES

    Kim, Jaekyun; Kim, Myung -Gil; Kim, Jaehyun; Jo, Sangho; Kang, Jingu; Jo, Jeong -Wan; Lee, Woobin; Hwang, Chahwan; Moon, Juhyuk; Yang, Lin; et al

    2015-09-28

    The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. Inmore » this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-μm-scale. As a result, the successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics.« less

  4. Scalable sub-micron patterning of organic materials toward high density soft electronics

    SciTech Connect

    Kim, Jaekyun; Kim, Myung -Gil; Kim, Jaehyun; Jo, Sangho; Kang, Jingu; Jo, Jeong -Wan; Lee, Woobin; Hwang, Chahwan; Moon, Juhyuk; Yang, Lin; Kim, Yun -Hi; Noh, Yong -Young; Yun Jaung, Jae; Kim, Yong -Hoon; Kyu Park, Sung

    2015-09-28

    The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. In this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-μm-scale. As a result, the successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics.

  5. Scalable Sub-micron Patterning of Organic Materials Toward High Density Soft Electronics.

    PubMed

    Kim, Jaekyun; Kim, Myung-Gil; Kim, Jaehyun; Jo, Sangho; Kang, Jingu; Jo, Jeong-Wan; Lee, Woobin; Hwang, Chahwan; Moon, Juhyuk; Yang, Lin; Kim, Yun-Hi; Noh, Yong-Young; Jaung, Jae Yun; Kim, Yong-Hoon; Park, Sung Kyu

    2015-09-28

    The success of silicon based high density integrated circuits ignited explosive expansion of microelectronics. Although the inorganic semiconductors have shown superior carrier mobilities for conventional high speed switching devices, the emergence of unconventional applications, such as flexible electronics, highly sensitive photosensors, large area sensor array, and tailored optoelectronics, brought intensive research on next generation electronic materials. The rationally designed multifunctional soft electronic materials, organic and carbon-based semiconductors, are demonstrated with low-cost solution process, exceptional mechanical stability, and on-demand optoelectronic properties. Unfortunately, the industrial implementation of the soft electronic materials has been hindered due to lack of scalable fine-patterning methods. In this report, we demonstrated facile general route for high throughput sub-micron patterning of soft materials, using spatially selective deep-ultraviolet irradiation. For organic and carbon-based materials, the highly energetic photons (e.g. deep-ultraviolet rays) enable direct photo-conversion from conducting/semiconducting to insulating state through molecular dissociation and disordering with spatial resolution down to a sub-μm-scale. The successful demonstration of organic semiconductor circuitry promise our result proliferate industrial adoption of soft materials for next generation electronics.

  6. Micron dimensioned cavity array supported lipid bilayers for the electrochemical investigation of ionophore activity.

    PubMed

    Maher, Sean; Basit, Hajra; Forster, Robert J; Keyes, Tia E

    2016-12-01

    Microcavity supported lipid bilayers, MSLBs, were applied to an electrochemical investigation of ionophore mediated ion transport. The arrays comprise of a 1cm(2) gold electrode imprinted with an ordered array of uniform spherical-cap pores of 2.8μm diameter prepared by gold electrodeposition through polystyrene templating spheres. The pores were pre-filled with aqueous buffer prior to Langmuir-Blodgett assembly of a 1,2-dioleoyl-sn-glycero-3-phosphocholine bilayer. Fluorescence lifetime correlation spectroscopy enabled by the micron dimensions of the pores permitted study of lipid diffusion across single apertures, yielding a diffusion coefficient of 12.58±1.28μm(2)s(-1) and anomalous exponent of 1.03±0.02, consistent with Brownian motion. From FLCS, the MSLBs were stable over 3days and electrochemical impedance spectroscopy of the membrane with and without ionic gradient over experimental windows of 6h showed excellent stability. Two ionophores were studied at the MSLBs; Valinomycin, a K(+) uniporter and Nigericin, a K(+)/H(+) antiporter. Ionophore reconstituted into the DOPC bilayer resulted in a decrease and increase in membrane resistance and capacitance respectively. Significant increases in Valinomycin and Nigericin activity were observed, reflected in large decreases in membrane resistance when K(+) was present in the contacting buffer and in the presence of H(+) ionic gradient across the membrane respectively.

  7. Discovering Motifs in Biological Sequences Using the Micron Automata Processor.

    PubMed

    Roy, Indranil; Aluru, Srinivas

    2016-01-01

    Finding approximately conserved sequences, called motifs, across multiple DNA or protein sequences is an important problem in computational biology. In this paper, we consider the (l, d) motif search problem of identifying one or more motifs of length l present in at least q of the n given sequences, with each occurrence differing from the motif in at most d substitutions. The problem is known to be NP-complete, and the largest solved instance reported to date is (26,11). We propose a novel algorithm for the (l,d) motif search problem using streaming execution over a large set of non-deterministic finite automata (NFA). This solution is designed to take advantage of the micron automata processor, a new technology close to deployment that can simultaneously execute multiple NFA in parallel. We demonstrate the capability for solving much larger instances of the (l, d) motif search problem using the resources available within a single automata processor board, by estimating run-times for problem instances (39,18) and (40,17). The paper serves as a useful guide to solving problems using this new accelerator technology. PMID:26886735

  8. Tunneling of micron-sized droplets through soap films.

    PubMed

    Kim, Ildoo; Wu, X L

    2010-08-01

    When a micron-sized water droplet impacts on a freely suspended soap film with speed v(i), there exists a critical impact velocity of penetration v(C). Droplets with v(i)v(C) tunnel through it. In all cases, the film remains intact despite the fact that the droplet radius (R_{0}=26 μm) is much greater than the film thickness (0

  9. Tunneling of micron-sized droplets through soap films

    NASA Astrophysics Data System (ADS)

    Kim, Ildoo; Wu, X. L.

    2010-08-01

    When a micron-sized water droplet impacts on a freely suspended soap film with speed vi , there exists a critical impact velocity of penetration vC . Droplets with vivC tunnel through it. In all cases, the film remains intact despite the fact that the droplet radius (R0=26μm) is much greater than the film thickness (0

  10. [Micronized purified flavonoid fraction in treatment of pelvic varicose veins].

    PubMed

    Gavrilov, S G; Karalkin, A V; Moskalenko, E P; Beliaeva, E S; Ianina, A M; Kirienko, A I

    2012-01-01

    Presented herein are the results of studying efficacy of micronized purified flavonoid fraction (MPFF) in treatment of pelvic varicose veins (PVV) using reference ray-tracing methods of study. We examined a total of 85 patients with PVV. Of these, 65 subjects were found to have isolated dilatation of pelvic venous plexuses (study group), and 20 were diagnosed as having combined dilation of gonadal veins and venous plexuses of the pelvis (control group). Besides clinical examination, the patients were subjected to ultrasonographic angioscanning (USAS) and emission computed tomography (ECT) of pelvic veins before treatment and 2, 6, 12, 24, 36 and 60 months after the beginning of phlebotrophic therapy. Based on the findings of the clinical and instrumental studies, it was determined that MPFF was most efficient in patients with isolated dilatation of uterine and parametrial veins. In this group of patients, pelvic pain and other symptoms of the disease disappeared completely and the clinical effect persisted for a long time (up to 6-9 months). In the control group, venotonic therapy had a positive effect which was less pronounced as compared to the control group, and pelvic pain reappeared in the nearest time (up to 3 weeks) after withdrawal of MPFF.

  11. Micronization of silybin by the emulsion solvent diffusion method.

    PubMed

    Zhang, Zhi-Bing; Shen, Zhi-Gang; Wang, Jie-Xin; Zhang, Hai-Xia; Zhao, Hong; Chen, Jian-Feng; Yun, Jimmy

    2009-07-01

    Micronized silybin particles were successfully prepared by emulsion solvent diffusion method. Uniform spherical and rod-shaped particles with a mean size of 2.48 and 0.89 microm could be obtained using sodium dodecyl sulfate (SDS) concentration of 0.1 wt% at 30 and 15 degrees C, respectively. The characterization of silybin particles by SEM and particle size distribution (PSD) indicated that with the increase of temperature from 15 to 30 degrees C, the as-prepared particles became bigger and had a tendency to turn into spherical shapes; with the increase of SDS concentration from 0.02 to 0.1 wt%, the span of PSD became narrower while the mean particle size kept almost unchanged. XRD patterns and FT-IR spectra showed that the spherical and rod-shaped silybin particles possessed decreased crystallinity; however, the chemical structure and components were similar to those of the commercial silybin powder. Dissolution tests demonstrated that both of the spherical and rod-shaped silybin particles exhibited significantly enhanced dissolution rate when compared to the commercial silybin powder.

  12. Penetration and Effectiveness of Micronized Copper in Refractory Wood Species.

    PubMed

    Civardi, Chiara; Van den Bulcke, Jan; Schubert, Mark; Michel, Elisabeth; Butron, Maria Isabel; Boone, Matthieu N; Dierick, Manuel; Van Acker, Joris; Wick, Peter; Schwarze, Francis W M R

    2016-01-01

    The North American wood decking market mostly relies on easily treatable Southern yellow pine (SYP), which is being impregnated with micronized copper (MC) wood preservatives since 2006. These formulations are composed of copper (Cu) carbonate particles (CuCO3·Cu(OH)2), with sizes ranging from 1 nm to 250 μm, according to manufacturers. MC-treated SYP wood is protected against decay by solubilized Cu2+ ions and unreacted CuCO3·Cu(OH)2 particles that successively release Cu2+ ions (reservoir effect). The wood species used for the European wood decking market differ from the North American SYP. One of the most common species is Norway spruce wood, which is poorly treatable i.e. refractory due to the anatomical properties, like pore size and structure, and chemical composition, like pit membrane components or presence of wood extractives. Therefore, MC formulations may not suitable for refractory wood species common in the European market, despite their good performance in SYP. We evaluated the penetration effectiveness of MC azole (MCA) in easily treatable Scots pine and in refractory Norway spruce wood. We assessed the effectiveness against the Cu-tolerant wood-destroying fungus Rhodonia placenta. Our findings show that MCA cannot easily penetrate refractory wood species and could not confirm the presence of a reservoir effect. PMID:27649315

  13. Advancing dental implant surface technology--from micron- to nanotopography.

    PubMed

    Mendonça, Gustavo; Mendonça, Daniela B S; Aragão, Francisco J L; Cooper, Lyndon F

    2008-10-01

    Current trends in clinical dental implant therapy include use of endosseous dental implant surfaces embellished with nanoscale topographies. The goal of this review is to consider the role of nanoscale topographic modification of titanium substrates for the purpose of improving osseointegration. Nanotechnology offers engineers and biologists new ways of interacting with relevant biological processes. Moreover, nanotechnology has provided means of understanding and achieving cell specific functions. The various techniques that can impart nanoscale topographic features to titanium endosseous implants are described. Existing data supporting the role of nanotopography suggest that critical steps in osseointegration can be modulated by nanoscale modification of the implant surface. Important distinctions between nanoscale and micron-scale modification of the implant surface are presently considered. The advantages and disadvantages of nanoscale modification of the dental implant surface are discussed. Finally, available data concerning the current dental implant surfaces that utilize nanotopography in clinical dentistry are described. Nanoscale modification of titanium endosseous implant surfaces can alter cellular and tissue responses that may benefit osseointegration and dental implant therapy.

  14. Penetration and Effectiveness of Micronized Copper in Refractory Wood Species

    PubMed Central

    Civardi, Chiara; Van den Bulcke, Jan; Schubert, Mark; Michel, Elisabeth; Butron, Maria Isabel; Boone, Matthieu N.; Dierick, Manuel; Van Acker, Joris; Wick, Peter; Schwarze, Francis W. M. R.

    2016-01-01

    The North American wood decking market mostly relies on easily treatable Southern yellow pine (SYP), which is being impregnated with micronized copper (MC) wood preservatives since 2006. These formulations are composed of copper (Cu) carbonate particles (CuCO3·Cu(OH)2), with sizes ranging from 1 nm to 250 μm, according to manufacturers. MC-treated SYP wood is protected against decay by solubilized Cu2+ ions and unreacted CuCO3·Cu(OH)2 particles that successively release Cu2+ ions (reservoir effect). The wood species used for the European wood decking market differ from the North American SYP. One of the most common species is Norway spruce wood, which is poorly treatable i.e. refractory due to the anatomical properties, like pore size and structure, and chemical composition, like pit membrane components or presence of wood extractives. Therefore, MC formulations may not suitable for refractory wood species common in the European market, despite their good performance in SYP. We evaluated the penetration effectiveness of MC azole (MCA) in easily treatable Scots pine and in refractory Norway spruce wood. We assessed the effectiveness against the Cu-tolerant wood-destroying fungus Rhodonia placenta. Our findings show that MCA cannot easily penetrate refractory wood species and could not confirm the presence of a reservoir effect. PMID:27649315

  15. Micron-gap ThermoPhotoVoltaics (MTPV)

    NASA Astrophysics Data System (ADS)

    DiMatteo, R.; Greiff, P.; Seltzer, D.; Meulenberg, D.; Brown, E.; Carlen, E.; Kaiser, K.; Finberg, S.; Nguyen, H.; Azarkevich, J.; Baldasaro, P.; Beausang, J.; Danielson, L.; Dashiell, M.; DePoy, D.; Ehsani, H.; Topper, W.; Rahner, K.; Siergiej, R.

    2004-11-01

    This paper discusses advances made in the field of Micron-gap ThermoPhotoVoltaics (MTPV). Initial modeling has shown that MTPV may enable significant performance improvements relative to conventional far field TPV. These performance improvements include up to a 10× increase in power density, 30% to 35% fractional increase in conversion efficiency, or alternatively, reduced radiator temperature requirements to as low as 550°C. Recent experimental efforts aimed at supporting these predictions have successfully demonstrated that early current and voltage enhancements could be done repeatedly and at higher temperatures. More importantly, these efforts indicated that no unknown energy transfer process occurs reducing the potential utility of MTPV. Progress has been made by running tests with at least one of the following characteristics relative to the MTPV results reported in 2001: • Tests at over twice the temperature (900°C). • Tests at 50% smaller gaps (0.12 μm) • Tests with emitter areas from 4 to 100 times larger (16 mm2 to 4 cm2). • Tests with over 20× reduction in parasitic spacer heat flow. Remaining fundamental challenges to realizing these improvements relative to the recent breakthroughs in conventional far field TPV include reengineering the photovoltaic (PV) diode, filter, and emitter system for MTPV and engineering devices and systems that can achieve submicron vacuum gaps between surfaces with large temperature differences.

  16. Airborne 20-65 micron spectrophotometry of Comet Halley

    NASA Technical Reports Server (NTRS)

    Glaccum, William; Moseley, S. H.; Campins, Humberto C.; Loewenstein, R. F.

    1988-01-01

    Observations of Comet Halley with a grating spectrometer on board the Kuiper Airborne Observatory on four nights in Dec. 1985 to Apr. 1986 are reported. Low resolution 20 to 65 micrometer spectra of the nucleus with a 40 arcsec FWHM beam was obtained on 17 Dec. 1985, and on 15 and 17 Apr. 1986. On 20 Dec. 1985, only a 20 to 35 micrometer spectrum was obtained. Most of the data have been discussed in a paper where the continuum was dealt with. In that paper, models were fit to the continuum that showed that more micron sized particles of grain similar to amorphous carbon were needed to fit the spectrum than were allowed by the Vega SP-2 mass distribution, or that a fraction of the grains had to be made out of a material whose absorption efficiency fell steeper than lambda sup -1 for lambda greater than 20 micrometers. Spectra was also presented taken at several points on the coma on 15 Apr. which showed that the overall shape to the spectrum is the same in the coma. Tabulated values of the data and calibration curves are available. The spectral features are discussed.

  17. Broadband dielectric microwave microscopy on micron length scales.

    PubMed

    Tselev, Alexander; Anlage, Steven M; Ma, Zhengkun; Melngailis, John

    2007-04-01

    We demonstrate that a near-field microwave microscope based on a transmission line resonator allows imaging in a substantially wide range of frequencies, so that the microscope properties approach those of a spatially resolved impedance analyzer. In the case of an electric probe, the broadband imaging can be used in a direct fashion to separate contributions from capacitive and resistive properties of a sample at length scales on the order of one micron. Using a microwave near-field microscope based on a transmission line resonator we imaged the local dielectric properties of a focused ion beam milled structure on a high-dielectric-constant Ba(0.6)Sr(0.4)TiO(3) thin film in the frequency range from 1.3 to 17.4 GHz. The electrostatic approximation breaks down already at frequencies above approximately 10 GHz for the probe geometry used, and a full-wave analysis is necessary to obtain qualitative information from the images.

  18. Slab melting as a barrier to deep carbon subduction.

    PubMed

    Thomson, Andrew R; Walter, Michael J; Kohn, Simon C; Brooker, Richard A

    2016-01-01

    Interactions between crustal and mantle reservoirs dominate the surface inventory of volatile elements over geological time, moderating atmospheric composition and maintaining a life-supporting planet. While volcanoes expel volatile components into surface reservoirs, subduction of oceanic crust is responsible for replenishment of mantle reservoirs. Many natural, 'superdeep' diamonds originating in the deep upper mantle and transition zone host mineral inclusions, indicating an affinity to subducted oceanic crust. Here we show that the majority of slab geotherms will intersect a deep depression along the melting curve of carbonated oceanic crust at depths of approximately 300 to 700 kilometres, creating a barrier to direct carbonate recycling into the deep mantle. Low-degree partial melts are alkaline carbonatites that are highly reactive with reduced ambient mantle, producing diamond. Many inclusions in superdeep diamonds are best explained by carbonate melt-peridotite reaction. A deep carbon barrier may dominate the recycling of carbon in the mantle and contribute to chemical and isotopic heterogeneity of the mantle reservoir. PMID:26738593

  19. Coherent combination of slab-coupled optical waveguide lasers

    NASA Astrophysics Data System (ADS)

    Huang, Robin K.; Chann, Bien; Missaggia, Leo J.; Augst, Steven J.; Connors, Michael K.; Turner, George W.; Sanchez-Rubio, Antonio; Donnelly, Joseph P.; Hostetler, John L.; Miester, Carl; Dorsch, Friedhelm

    2009-02-01

    A long-standing challenge for semiconductor lasers is scaling the optical power and brightness of many diode lasers by coherent beam combination. Because single-mode semiconductor lasers have limited power available from a single element, there is a strong motivation to coherently combine the outputs of many elements for applications including industrial lasers for materials processing, free space optical communications, and defense. Despite the fact that such a coherently-combined source is potentially the most efficient laser, coherent combination of semiconductor lasers is generally considered to be difficult, since precise phase control is required between elements. We describe our approach to coherent combination of semiconductor lasers. The Slab-Coupled Optical Waveguide Laser (SCOWL), invented at Lincoln Laboratory, is used as the single-mode diode laser element for coherent combination. With a 10-element SCOWL array, coherently combined output power as high as 7 W in continuous wave using an external cavity has been demonstrated, which is the highest output level achieved using a coherent array of semiconductor lasers. We are currently working on a related approach to scale the coherent power up to 100 W.

  20. Maximizing Photoluminescence Extraction in Silicon Photonic Crystal Slabs

    NASA Astrophysics Data System (ADS)

    Mahdavi, Ali; Sarau, George; Xavier, Jolly; Paraïso, Taofiq K.; Christiansen, Silke; Vollmer, Frank

    2016-04-01

    Photonic crystal modes can be tailored for increasing light matter interactions and light extraction efficiencies. These PhC properties have been explored for improving the device performance of LEDs, solar cells and precision biosensors. Tuning the extended band structure of 2D PhC provides a means for increasing light extraction throughout a planar device. This requires careful design and fabrication of PhC with a desirable mode structure overlapping with the spectral region of emission. We show a method for predicting and maximizing light extraction from 2D photonic crystal slabs, exemplified by maximizing silicon photoluminescence (PL). Systematically varying the lattice constant and filling factor, we predict the increases in PL intensity from band structure calculations and confirm predictions in micro-PL experiments. With the near optimal design parameters of PhC, we demonstrate more than 500-fold increase in PL intensity, measured near band edge of silicon at room temperature, an enhancement by an order of magnitude more than what has been reported.

  1. Maximizing Photoluminescence Extraction in Silicon Photonic Crystal Slabs

    PubMed Central

    Mahdavi, Ali; Sarau, George; Xavier, Jolly; Paraïso, Taofiq K.; Christiansen, Silke; Vollmer, Frank

    2016-01-01

    Photonic crystal modes can be tailored for increasing light matter interactions and light extraction efficiencies. These PhC properties have been explored for improving the device performance of LEDs, solar cells and precision biosensors. Tuning the extended band structure of 2D PhC provides a means for increasing light extraction throughout a planar device. This requires careful design and fabrication of PhC with a desirable mode structure overlapping with the spectral region of emission. We show a method for predicting and maximizing light extraction from 2D photonic crystal slabs, exemplified by maximizing silicon photoluminescence (PL). Systematically varying the lattice constant and filling factor, we predict the increases in PL intensity from band structure calculations and confirm predictions in micro-PL experiments. With the near optimal design parameters of PhC, we demonstrate more than 500-fold increase in PL intensity, measured near band edge of silicon at room temperature, an enhancement by an order of magnitude more than what has been reported. PMID:27113674

  2. Treacherous Pavements: Paving Slab Patterns Modify Intended Walking Directions.

    PubMed

    Leonards, Ute; Fennell, John G; Oliva, Gaby; Drake, Alex; Redmill, David W

    2015-01-01

    Current understanding in locomotion research is that, for humans, navigating natural environments relies heavily on visual input; in contrast, walking on even ground in man-made obstacle and hazard-free environments is so highly automated that visual information derived from floor patterns should not affect locomotion and in particular have no impact on the direction of travel. The vision literature on motion perception would suggest otherwise; specifically that oblique floor patterns may induce substantial veering away from the intended direction of travel due to the so-called aperture problem. Here, we tested these contrasting predictions by letting participants walk over commonly encountered floor patterns (paving slabs) and investigating participants' ability to walk "straight ahead" for different pattern orientations. We show that, depending on pattern orientation, participants veered considerably over the measured travel distance (up to 8% across trials), in line with predictions derived from the literature on motion perception. We argue that these findings are important to the study of locomotion, and, if also observed in real world environments, might have implications for architectural design.

  3. Maximizing Photoluminescence Extraction in Silicon Photonic Crystal Slabs.

    PubMed

    Mahdavi, Ali; Sarau, George; Xavier, Jolly; Paraïso, Taofiq K; Christiansen, Silke; Vollmer, Frank

    2016-01-01

    Photonic crystal modes can be tailored for increasing light matter interactions and light extraction efficiencies. These PhC properties have been explored for improving the device performance of LEDs, solar cells and precision biosensors. Tuning the extended band structure of 2D PhC provides a means for increasing light extraction throughout a planar device. This requires careful design and fabrication of PhC with a desirable mode structure overlapping with the spectral region of emission. We show a method for predicting and maximizing light extraction from 2D photonic crystal slabs, exemplified by maximizing silicon photoluminescence (PL). Systematically varying the lattice constant and filling factor, we predict the increases in PL intensity from band structure calculations and confirm predictions in micro-PL experiments. With the near optimal design parameters of PhC, we demonstrate more than 500-fold increase in PL intensity, measured near band edge of silicon at room temperature, an enhancement by an order of magnitude more than what has been reported. PMID:27113674

  4. Slab melting as a barrier to deep carbon subduction

    NASA Astrophysics Data System (ADS)

    Thomson, Andrew R.; Walter, Michael J.; Kohn, Simon C.; Brooker, Richard A.

    2016-01-01

    Interactions between crustal and mantle reservoirs dominate the surface inventory of volatile elements over geological time, moderating atmospheric composition and maintaining a life-supporting planet. While volcanoes expel volatile components into surface reservoirs, subduction of oceanic crust is responsible for replenishment of mantle reservoirs. Many natural, ‘superdeep’ diamonds originating in the deep upper mantle and transition zone host mineral inclusions, indicating an affinity to subducted oceanic crust. Here we show that the majority of slab geotherms will intersect a deep depression along the melting curve of carbonated oceanic crust at depths of approximately 300 to 700 kilometres, creating a barrier to direct carbonate recycling into the deep mantle. Low-degree partial melts are alkaline carbonatites that are highly reactive with reduced ambient mantle, producing diamond. Many inclusions in superdeep diamonds are best explained by carbonate melt-peridotite reaction. A deep carbon barrier may dominate the recycling of carbon in the mantle and contribute to chemical and isotopic heterogeneity of the mantle reservoir.

  5. Slab melting as a barrier to deep carbon subduction.

    PubMed

    Thomson, Andrew R; Walter, Michael J; Kohn, Simon C; Brooker, Richard A

    2016-01-01

    Interactions between crustal and mantle reservoirs dominate the surface inventory of volatile elements over geological time, moderating atmospheric composition and maintaining a life-supporting planet. While volcanoes expel volatile components into surface reservoirs, subduction of oceanic crust is responsible for replenishment of mantle reservoirs. Many natural, 'superdeep' diamonds originating in the deep upper mantle and transition zone host mineral inclusions, indicating an affinity to subducted oceanic crust. Here we show that the majority of slab geotherms will intersect a deep depression along the melting curve of carbonated oceanic crust at depths of approximately 300 to 700 kilometres, creating a barrier to direct carbonate recycling into the deep mantle. Low-degree partial melts are alkaline carbonatites that are highly reactive with reduced ambient mantle, producing diamond. Many inclusions in superdeep diamonds are best explained by carbonate melt-peridotite reaction. A deep carbon barrier may dominate the recycling of carbon in the mantle and contribute to chemical and isotopic heterogeneity of the mantle reservoir.

  6. Metamaterial slab-based super-absorbers and perfect nanodetectors for single dipole sources.

    PubMed

    Guo, Guang-Yu; Klimov, Vasily; Sun, Shulin; Zheng, Wei-Jin

    2013-05-01

    We propose to use double negative (DNG) metamaterial slabs to build effective super-absorbers and perfect nanodetectors for single divergent sources. We demonstrate by numerical simulations that an absorbing nanoparticle properly placed inside a DNG slab back-covered with a perfect electric conductor or perfect magnetic conductor mirror can absorb up to 100% radiation energy of a single dipole source placed outside the slab. Furthermore, we also show that even the simple DNG slab without any absorbing nanoparticle could be used as a perfect absorber for both plane and divergent beams. The proposed systems may focus the radiation in nanoscale and thus have applications in optical nanodevices for a variety of different purposes. PMID:23669990

  7. Oblique incidence of semi-guided waves on rectangular slab waveguide discontinuities: A vectorial QUEP solver

    NASA Astrophysics Data System (ADS)

    Hammer, Manfred

    2015-03-01

    The incidence of thin-film-guided, in-plane unguided waves at oblique angles on straight discontinuities of dielectric slab waveguides, an early problem of integrated optics, is being re-considered. The 3-D frequency domain Maxwell equations reduce to a parametrized inhomogeneous vectorial problem on a 2-D computational domain, with transparent-influx boundary conditions. We propose a rigorous vectorial solver based on simultaneous expansions into polarized local slab eigenmodes along the two orthogonal cross section coordinates (quadridirectional eigenmode propagation QUEP). The quasi-analytical scheme is applicable to configurations with - in principle - arbitrary cross section geometries. Examples for a high-contrast facet of an asymmetric slab waveguide, for the lateral excitation of a channel waveguide, and for a step discontinuity between slab waveguides of different thicknesses are discussed.

  8. 18. RADAR BED/SLAB AND ROOF OPENING FOR BEAM, WITH MIRROR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    18. RADAR BED/SLAB AND ROOF OPENING FOR BEAM, WITH MIRROR ABOVE, ROOM 3001, PENTHOUSE. - Hughes Aircraft Company, Assembly & Manufacturing Building, 6775 Centinela Avenue, Los Angeles, Los Angeles County, CA

  9. Effects of triggering mechanism on snow avalanche slope angles and slab depths from field data

    NASA Astrophysics Data System (ADS)

    McClung, David M.

    2013-04-01

    Field data from snow avalanche fracture lines for slope angle and slab depth (measured perpendicular to the weak layer) were analyzed for different triggering mechanisms. For slope angle, the results showed that the same probability density function (pdf) (of log-logistic type) and range (25 - 55 degrees) apply independent of triggering mechanism. For slab depth, the same pdf (generalized extreme value) applies independent of triggering mechanism. For both slope angle and slab depth, the data skewness differentiated between triggering mechanism and increased with applied triggering load. For slope angle, skewness is lowest for natural triggering by snow loads and highest for triggering from human intervention. For slab depth, the skewness is lowest for natural triggering and highest for a mix of triggers including explosive control with skier triggering being intermediate. The results reveal the effects of triggering mechanism which are important for risk analyses and to guide avalanche forecasting.

  10. Quasi-phase matching of high-order harmonics in modulated slab waveguide

    NASA Astrophysics Data System (ADS)

    Gu, Peng; Liu, Shi-Bing; Song, Hai-Ying

    2016-11-01

    A femtosecond Ti:sapphire laser is focused into a modulated He-filled slab waveguide to generate high-order harmonics. The modulated slab waveguide is used to periodically vary the intensity of the laser pulse along the direction of propagation in order to implement quasi-phase matching of the high-order harmonics. Experimental results show that compared with the spectra emitted from an unmodulated slab waveguide, there is an obvious increase in the yield of high harmonics at wavelengths close to the cutoff region. This finding is in agreement with theory and calculations reported in previous research. Therefore, our experiment indicates that, as with the modulated hollow-core waveguide, a slab waveguide can also achieve quasi-phase matched high-order harmonics.

  11. Reasonable Temperature Schedules for Cold or Hot Charging of Continuously Cast Steel Slabs

    NASA Astrophysics Data System (ADS)

    Li, Yang; Chen, Xin; Liu, Ke; Wang, Jing; Wen, Jin; Zhang, Jiaquan

    2013-12-01

    Some continuously cast steel slabs are sensitive to transverse fracture problems during transportation or handling away from their storage state, while some steel slabs are sensitive to surface transverse cracks during the following rolling process in a certain hot charging temperature range. It is revealed that the investigated steel slabs with high fracture tendency under room cooling condition always contain pearlite transformation delayed elements, which lead to the internal brittle bainitic structure formation, while some microalloyed steels exhibit high surface crack susceptibility to hot charging temperatures due to carbonitride precipitation. According to the calculated internal cooling rates and CCT diagrams, the slabs with high fracture tendency during cold charging should be slowly cooled after cutting to length from hot strand or charged to the reheating furnace directly above their bainite formation temperatures. Based on a thermodynamic calculation for carbonitride precipitation in austenite, the sensitive hot charging temperature range of related steels was revealed for the determination of reasonable temperature schedules.

  12. Goos-Haenchen shifts of the reflected waves from a cold, inhomogeneous, and magnetized plasma slab

    SciTech Connect

    Xu Guoding; Zang Taocheng; Pan Tao

    2010-01-15

    We discuss theoretically the Goos-Haenchen (GH) shifts of the reflected waves from a cold, inhomogeneous, and magnetized plasma slab by using the invariant imbedding approach. Aiming at the linear and parabolic electron-density profiles, we demonstrate numerically the dependences of the co- and cross-polarized GH shifts on the angle of incidence, external static magnetic field, and the thickness of the plasma slab. The results show that the different electron-density profiles of plasma can result in the very different dependences of the GH shifts on the angle of incidence, external magnetic field, and the slab's thickness; the GH shifts can be switched between the considerably large positive and negative values under certain conditions. Particularly, without altering the structure of the plasma slab, the GH shifts can be manipulated by modifying the angle of incident or the external static magnetic field.

  13. Evidence for slab material under Greenland and links to Cretaceous High Arctic magmatism

    NASA Astrophysics Data System (ADS)

    Shephard, G. E.; Trønnes, R. G.; Spakman, W.; Panet, I.; Gaina, C.

    2016-04-01

    Understanding the evolution of extinct ocean basins through time and space demands the integration of surface kinematics and mantle dynamics. We explore the existence, origin, and implications of a proposed oceanic slab burial ground under Greenland through a comparison of seismic tomography, slab sinking rates, regional plate reconstructions, and satellite-derived gravity gradients. Our preferred interpretation stipulates that anomalous, fast seismic velocities at 1000-1600 km depth imaged in independent global tomographic models, coupled with gravity gradient perturbations, represent paleo-Arctic oceanic slabs that subducted in the Mesozoic. We suggest a novel connection between slab-related arc mantle and geochemical signatures in some of the tholeiitic and mildly alkaline magmas of the Cretaceous High Arctic Large Igneous Province in the Sverdrup Basin. However, continental crustal contributions are noted in these evolved basaltic rocks. The integration of independent, yet complementary, data sets provides insight into present-day mantle structure, magmatic events, and relict oceans.

  14. Evolution of attached and detached slabs and their associated mantle dynamics

    NASA Technical Reports Server (NTRS)

    Hsui, Albert T.

    1992-01-01

    Over the two years of the NASA grant, this project has produced a significant amount of research results related to the plate subduction process and the surface crustal deformation at convergent boundaries (i.e., above subduction zones). While some research objectives are completely accomplished, other research tasks remain active and continue to be investigated at present. A steady state analytic thermal model for subducting slabs was used to examine the torques acting on a descending slab. It is found that gravitational torque vanishes when a slab is dipping either vertically or horizontally, unlike previous studies indicating that the magnitude of gravitational torque decreases as dip angle increases. Subsequently, a new time-dependent, analytic thermal model for a subducting slab was developed. The new model enables us to study transient phenomena associated with plate subduction analytically. On the basis of this model, the nature of slab dip angles was evaluated. Slab dip angles are found to be transient features. As they penetrate into the mantle and increase their lengths, the associated gravitational torque also increases resulting in a downward pulling of the slab to the steeper dip angle. This is especially true once a slab penetrates the olivine-spinel phase boundary at about 400 km depth. However, if the phase transformation does not follow the equilibrium condition, the gravitational torque may have a different behavior. This problem was investigated. Except for fast descending slabs, non-equilibrium phase transformation can only slow down the transient increase of slab dip angles discussed earlier. Its effect is not sufficiently strong to reverse the downward pulling for most of the slabs. However, when slabs subducting at 10 cm/yr or faster, a sufficient amount of metastable olivine can exist beneath 400 km. Because of its low density compared with the surrounding spinel, an upward buoyancy is produced resulting in an upward bending of the slab and

  15. 29. SPILLWAY BUCKET SLAB: REINFORCEMENT DETAILS NO. 3. Sheet S40, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    29. SPILLWAY BUCKET SLAB: REINFORCEMENT DETAILS NO. 3. Sheet S-40, December, 1939. File no. SA 342/49. - Prado Dam, Spillway, Santa Ana River near junction of State Highways 71 & 91, Corona, Riverside County, CA

  16. 28. SPILLWAY BUCKET SLAB: REINFORCEMENT DETAILS NO. 1. Sheet S37, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    28. SPILLWAY BUCKET SLAB: REINFORCEMENT DETAILS NO. 1. Sheet S-37, December, 1939. File no. SA 342/47. - Prado Dam, Spillway, Santa Ana River near junction of State Highways 71 & 91, Corona, Riverside County, CA

  17. 22. SPILLWAY CHANNEL SLAB REINFORCEMENT DETAILS, NO. 1. Sheet S4, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    22. SPILLWAY CHANNEL SLAB REINFORCEMENT DETAILS, NO. 1. Sheet S-4, February, 1939. File no. SA 343/67. - Prado Dam, Spillway, Santa Ana River near junction of State Highways 71 & 91, Corona, Riverside County, CA

  18. 30. SPILLWAY BUCKET SLAB: REINFORCEMENT DETAILS NO. 4. Sheet S44, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    30. SPILLWAY BUCKET SLAB: REINFORCEMENT DETAILS NO. 4. Sheet S-44, December, 1939. File no. SA 342/50. - Prado Dam, Spillway, Santa Ana River near junction of State Highways 71 & 91, Corona, Riverside County, CA

  19. An overview on in situ micronization technique - An emerging novel concept in advanced drug delivery.

    PubMed

    Vandana, K R; Prasanna Raju, Y; Harini Chowdary, V; Sushma, M; Vijay Kumar, N

    2014-09-01

    The use of drug powders containing micronized drug particles has been increasing in several pharmaceutical dosage forms to overcome the dissolution and bioavailability problems. Most of the newly developed drugs are poorly water soluble which limits dissolution rate and bioavailability. The dissolution rate can be enhanced by micronization of the drug particles. The properties of the micronized drug substance such as particle size, size distribution, shape, surface properties, and agglomeration behaviour and powder flow are affected by the type of micronization technique used. Mechanical communition, spray drying and supercritical fluid (SCF) technology are the most commonly employed techniques for production of micronized drug particles but the characteristics of the resulting drug product cannot be controlled using these techniques. Hence, a newer technique called in situ micronization is developed in order to overcome the limitations associated with the other techniques. This review summarizes the existing knowledge on in situ micronization techniques. The properties of the resulting drug substance obtained by in situ micronization were also compared.

  20. Method of producing carbon coated nano- and micron-scale particles

    DOEpatents

    Perry, W. Lee; Weigle, John C; Phillips, Jonathan

    2013-12-17

    A method of making carbon-coated nano- or micron-scale particles comprising entraining particles in an aerosol gas, providing a carbon-containing gas, providing a plasma gas, mixing the aerosol gas, the carbon-containing gas, and the plasma gas proximate a torch, bombarding the mixed gases with microwaves, and collecting resulting carbon-coated nano- or micron-scale particles.