Science.gov

Sample records for micron slab stability

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. Stability of a two-volume MRxMHD model in slab geometry

    NASA Astrophysics Data System (ADS)

    Tuen, Li Huey; Hole, Matthew; Dewar, Robert; Dennis, Graham

    2015-11-01

    Ideal MHD models are inadequate to describe various physical attributes of toroidal plasmas with no continuous symmetry, such as magnetic islands and stochastic regions. A new MHD formulation, MRxMHD, uses only a finite number of ideal-MHD flux surface interfaces, with relaxed plasma regions in between, thus allowing a stepped-pressure profile, magnetic islands, and stochastic regions. In toroidally asymmetric plasma, the existence of interfaces in MRxMHD is contingent on the field pitch, or rotational transform, of flux surfaces being irrational; a KAM argument shows that some good equilibrium flux surfaces continue to exist for small perturbations to an integrable system (foliated by flux surfaces), provided that the rotational transforms on both sides of each interface are sufficiently irrational. Building upon the MRxMHD stability model by Hole, we study the effects of irrationality of the rotational transform at interfaces in MRxMHD on plasma stability. Investigating the plasma stability of a two-volume MRxMHD periodic-slab, we find that the 2D system stability conditions are dependent on the interface and resonance layer magnetic field pitch at minimised energy states. While tearing instabilities exist at low order rational resonances, investigating instability of high-order rationals requires study of pressure-driven instabilities.

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

    NASA Astrophysics Data System (ADS)

    Basu, Rahul

    2016-04-01

    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.

  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. A Two Micron All Sky Survey Analysis of the Stability of Southern Bok Globules

    NASA Astrophysics Data System (ADS)

    Racca, Germán A.; Vilas-Boas, José W. S.; de la Reza, Ramiro

    2009-10-01

    We used near-infrared Two Micron All Sky Survey data to construct visual extinction maps of a sample of Southern Bok globules utilizing the NICE method. We derived radial extinction profiles of dense cores identified in the globules and analyzed their stability against gravitational collapse with isothermal Bonnor-Ebert spheres. The frequency distribution of the stability parameter (ξmax) of these cores shows that a large number of them are located in stable states, followed by an abrupt decrease of cores in unstable states. This decrease is steeper for globules with associated IRAS point sources than for starless globules. Moreover, globules in stable states have a Bonnor-Ebert temperature of T = 15 ± 6 K, while the group of critical plus unstable globules has a different temperature of T = 10 ± 3 K. Distances were estimated to all the globules studied in this work and the spectral class of the IRAS sources was calculated. No variations were found in the stability parameters of the cores and the spectral class of their associated IRAS sources. On the basis of 13CO J = 1 - 0 molecular line observations, we identified and modeled a blue-asymmetric line profile toward a globule of the sample, obtaining an upper limit infall speed of 0.25 km s-1. Based on a Ph.D. thesis made at Observatório Nacional, Rio de Janeiro, Brazil.

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

    NASA Astrophysics Data System (ADS)

    Nasehi, R.

    2016-03-01

    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.

  11. An etalon stabilized 10-GHz comb source using a slab coupled waveguide amplifier

    NASA Astrophysics Data System (ADS)

    Davila-Rodriguez, Josue; Ozdur, Ibrahim T.; Mandridis, Dimitrios; Williams, Charles; Delfyett, Peter J.; Plant, Jason J.; Juodawlkis, Paul W.

    2011-06-01

    An optical comb source based on a slab-coupled optical waveguide amplifier (SCOWA) is presented. The laser is harmonically mode-locked at 10.287 GHz repetition rate and stabilized to an intra-cavity Fabry-Pérot etalon via Pound- Drever-Hall locking. The Fabry-Pérot etalon serves as a reference for the optical frequency of the comb-lines and suppresses the fiber cavity modes to allow only a single longitudinal mode-set to oscillate, generating a frequency comb spaced by the repetition rate. The pulse-to-pulse timing jitter and energy fluctuations are < 2 fs and < 0.03%, respectively (integrated from 1Hz to 100 MHz). Fundamental to this result is the incorporation of the SCOW amplifier as the gain medium and the use of an ultra-low noise sapphire-loaded cavity oscillator to mode-lock the laser. The SCOWA has higher saturation power than commercially available gain media, permitting higher intra-cavity power as well as available power at the output, increasing the power of the photodetected RF tones which increases their signal-to-noise ratio. A high visibility optical frequency comb is observed spanning ~3 nm (at -10 dB), with optical SNR > 60 dB for a cavity with no dispersion compensation. Initial results of a dispersion compensated cavity are presented. A spectral width of ~7.6 nm (-10 dB) was obtained for this case and the pulses can be compressed to near the transform limit at ~930 fs.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. Ultrasonic energy input influence οn the production of sub-micron o/w emulsions containing whey protein and common stabilizers.

    PubMed

    Kaltsa, O; Michon, C; Yanniotis, S; Mandala, I

    2013-05-01

    Ultrasonication may be a cost-effective emulsion formation technique, but its impact on emulsion final structure and droplet size needs to be further investigated. Olive oil emulsions (20wt%) were formulated (pH∼7) using whey protein (3wt%), three kinds of hydrocolloids (0.1-0.5wt%) and two different emulsification energy inputs (single- and two-stage, methods A and B, respectively). Formula and energy input effects on emulsion performance are discussed. Emulsions stability was evaluated over a 10-day storage period at 5°C recording the turbidity profiles of the emulsions. Optical micrographs, droplet size and viscosity values were also obtained. A differential scanning calorimetric (DSC) multiple cool-heat cyclic method (40 to -40°C) was performed to examine stability via crystallization phenomena of the dispersed phase. Ultrasonication energy input duplication from 11kJ to 25kJ (method B) resulted in stable emulsions production (reduction of back scattering values, dBS∼1% after 10days of storage) at 0.5wt% concentration of any of the stabilizers used. At lower gum amount samples became unstable due to depletion flocculation phenomena, regardless of emulsification energy input used. High energy input during ultrasonic emulsification also resulted in sub-micron oil-droplets emulsions (D(50)=0.615μm compared to D(50)=1.3μm using method A) with narrower particle size distribution and in viscosity reduction. DSC experiments revealed no presence of bulk oil formation, suggesting stability for XG 0.5wt% emulsions prepared by both methods. Reduced enthalpy values found when method B was applied suggesting structural modifications produced by extensive ultrasonication. Change of ultrasonication conditions results in significant changes of oil droplet size and stability of the produced emulsions. PMID:23266492

  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. Progress on slab lasers

    NASA Astrophysics Data System (ADS)

    Albrecht, G. F.; Eggleston, J. M.; Petr, R. A.

    1986-01-01

    After a brief overview of slab geometry work published to date, zig-zag optical path slab laser development toward a 100-Hz slab YAG system ('Centurion') and a 10-Hz dual slab glass system ('Gemini') is described. Some of the major diagnostic work performed and in the process is also described to illustrate the major mechanisms responsible for beam distortion observed in these types of slab lasers.

  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. 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.

  3. 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.

  4. Deepest hypocentral distributions associated with stagnant slabs and penetrated slabs

    NASA Astrophysics Data System (ADS)

    Fukao, Y.; Obayashi, M.

    2013-12-01

    We constructed a new P-wave tomographic model of the mantle, GAP_P4, using more than ten millions of travel time data, including waveform-based differential travel times from ocean bottoms, to all of which the finite frequency kernels were applied in the inversion. Based on this model, we made a systematic survey for subducted slab images around the Circum Pacific. This survey revealed a progressive lateral variation of slab configuration along arc(s), where a subducted slab is in general in one or two of the following four stages: I. slab stagnant above the 660, II. slab penetrating the 660, III. slab trapped in the uppermost lower mantle (660 to ˜1000 km in depth), and IV. slab descending well into the deep lower mantle. The majority of the slab images are either at stage I or III. We interpret I to IV as the successive stages of slab subduction through the transition region with the 660 at the middle. There is a remarkable correlation of the slab configuration with the deepest shock hypocentral distribution. Subhorizontal distributions of deepest shocks are associated with stagnant slabs in the transition zone (slabs at stage I). Their focal depths are limited to shallower than ˜620 km. Steeply dipping deepest shock distributions are associated with penetrating slabs across the 660-km discontinuity or trapped slabs below it (slabs at stages II and III). Their focal depths extend well beyond ˜620 km. There are no cases of association of either a stagnant slab (at stage I) with subvertical distribution of deepest shocks or a trapped slab (at stage II or III) with their subhorizontal distribution. Only steeply dipping slabs appear to penetrate the 660 to be trapped in the uppermost lower mantle. The along-arc variations of stagnant-slab configuration and deepest shock distribution beneath the Bonin arc indicate a process of how the slab begins to penetrate the 660-km discontinuity after the slab stagnation. Those beneath the Java arc and Kermadec arc commonly

  5. Cordilleran slab windows

    SciTech Connect

    Thorkelson, D.J.; Taylor, R.P. )

    1989-09-01

    The geometry and geologic implications of subducted spreading ridges are topics that have bedeviled earth scientists ever since the recognition of plate tectonics. As a consequence of subduction of the Kula-Farallon and East Pacific rises, slab windows formed and migrated beneath the North American Cordillera. The probable shape and extent of these windows, which represent the asthenosphere-filled gaps between two separating, subducting oceanic plates, are depicted from the Late Cretaceous to the present. Possible effects of the existence and migration of slab windows on the Cordillera at various times include cessation of arc volcanism and replacement by rift or plate-edge volcanism; lithospheric uplift, attenuation, and extension; and increased intensity of compressional tectonism. Eocene extensional tectonism and alkaline magmatism in southern British Columbia and the northwestern United States were facilitated by slab-window development.

  6. Slab Ice and Snow Flurries in the Martian Polar Night

    NASA Astrophysics Data System (ADS)

    Titus, T.; Kieffer, H.; Mullins, K.; Christensen, P.

    1999-11-01

    In the 1970s, spacecraft observations of the polar regions of Mars revealed polar brightness temperatures that were significantly below the expected kinetic temperatures for CO_2 sublimation. For the past few decades, we have speculated as to the nature of these Martian polar cold spots. Are the cold spots surface or atmospheric effects? Do the cold spots behave as blackbodies, or do they have emissivities less than unity? Two developments allow us to begin to answer these questions: the measurement of the optical constants of CO_2 by Gary Hansen and direct thermal spectroscopy by the Thermal Infrared Spectrometer (TES). TES thermal data has identified numerous cold spots at the Martian north pole. These areas of the polar cap have a strong absorption feature at 25 microns that is indicative of fine-grained CO_2. Brightness temperatures at 18 microns and 15 microns constrain most of these cold spots to the surface. Cold spot formation is strongly dependent on topography, forming preferentially near craters and on polar slopes. While most cold spots are surface effects, the formation of the fine-grained CO_2 is not restricted to formation on the surface. TES data, combined with MOLA cloud data, atmospheric condensates form a few of the observed cold spots. TES observations seem to indicate that another major component of the north polar cap's composition is slab CO2 ice. Slab ice has near unity spectral emissivity and appears to have a low albedo. Two explanations for the low albedo are that the slab ice is intrinsically dark or the slab ice is transparent and TES is seeing through to the underlying substrate. Regions of the cap where [T_18-T_25] < 5 degrees indicates deposits of slab ice. Slab ice is the dominant endmember of the polar cap at latitudes south of the polar night.

  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. Micron Scale Mineralogy

    NASA Astrophysics Data System (ADS)

    Caldwell, W. A.; Tamura, N.; Celestre, R. S.; Padmore, H. A.; Patel, J. R.

    2002-12-01

    Although x-ray diffraction has been used for nearly a century as the mineralogist's definitive tool in determining crystalline structures, it has proved impossible to use this technique to spatially resolve the highly heterogeneous nature of many minerals at the mesoscopic level. Due to recent revolutions in the brightness of x-ray sources and in our ability to focus x-rays, we can now carry out conventional monochromatic rotation crystallography as well as Laue diffraction with sub-micron spatial resolution and produce maps of orientation, strain, mineral type, and even chemical speciation over tens of microns in a short amount of time. We have pioneered the development of these techniques at the 3rd generation synchrotron radiation source (Advanced Light Source) in Berkeley, and will describe their application to understanding the structure of a quartz-geode. Our results show the manner in which grain structure and texture change as a function of distance from the cavity wall and are compared with models of crystal growth in such systems. This example highlights the great utility of a synchrotron based x-ray micro-diffraction beamline and the possibilities it opens to the mineralogist.

  11. 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...

  12. [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. PMID:24893451

  13. Airborne Astronomy with a 150 microns - 400 microns Heterodyne Spectrometer

    NASA Technical Reports Server (NTRS)

    Betz, A. L.

    1995-01-01

    This report summarizes work done under NASA Grant NAG2-753 awarded to the University of Colorado. The project goal was to build a far-infrared heterodyne spectrometer for NASA's Kuiper Airborne Observatory, and to use this instrument to observe atomic and molecular spectral lines from the interstellar medium. This goal was successfully achieved. Detections of particular note have been the 370 micron line of neutral atomic carbon, the 158 micron transition of ionized carbon, many of the high-J rotational lines of CO-12 and CO-13 between J=9-8 and J=22-21, the 119 micron and 163 micron rotational lines of OH, the 219 micron ground-state rotational line of H2D(+), and the 63 micron fine structure line of neutral atomic oxygen. All of these lines were observed at spectral resolutions exceeding 1 part in 10(exp 6) thereby allowing accurate line shapes and Doppler velocities to be measured.

  14. 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.

  15. 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.

  16. Palmitoylethanolamide: problems regarding micronization, ultra-micronization and additives.

    PubMed

    Kriek, Rutger

    2014-06-01

    It can be established that at least two of the writers of the article published in 'Inflammopharmacology', title: 'Palmitoylethanolamide (PEA), a naturally occurring disease-modifying agent in neuropathic pain' have a direct connection to the companies Epitech and Innovet. These companies produce micronized and ultra-micronized PEA. Therefore it is of eminent importance to determine whether the statements in this paper have also taken into consideration the European guidelines for Good Clinical Practice and the codes of good scientific practices. This is very questionable. A minimum condition in clinical studies for proving the claim that PEA in its micronized and ultra-micronized formulations works better than in its pure form or in other formulations is that a comparison be made between: PEA in pure form or in other formulations, on the one hand; PEA in the micronized and ultra-micronized formulations, on the other hand. This minimum condition is not complied with. Based on additional studies discussed in this commentary and in view of the effects of ultra-micronization on the parameters discussed, as well as the potential side-effects of additives such as excipients and herbal extracts added to the products cited in the article, the preference should be for the time being to treat patients with pure PEA without any of these additives. PMID:24647619

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    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.

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

    PubMed

    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

  19. 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

  20. Phase conjugated slab laser designator

    SciTech Connect

    Chandra, S.; Paul, J.L.

    1989-06-06

    A laser designator is described comprising a laser pump means; a high power phase conjugated slab laser amplifier formed of GSGG:Cr:Nd as a lasing material on one side of the pump means; a low power rod shaped laser oscillator on the opposite side of the pump means; and a first plurality of optical reflecting and refracting means for directing and shaping a laser beam which surrounds the pump means and passes through the rod and slab; and a telescope means coupled to the beam to direct it to a distant target.

  1. A wrinkly phononic crystal slab

    NASA Astrophysics Data System (ADS)

    Bayat, Alireza; Gordaninejad, Faramarz

    2015-03-01

    The buckling induced surface instability is employed to propose a tunable phononic crystal slab composed of a stiff thin film bonded on a soft elastomer. Wrinkles formation is used to generate one-dimensional periodic scatterers at the surface of a finitely thick slab. Wrinkles' pattern change and corresponding stress is employed to control wave propagation triggered by a compressive strain. Simulation results show that the periodic wrinkly structure can be used as a transformative phononic crystal which can switch band diagram of the structure in a reversible behavior. Results of this study provide opportunities for the smart design of tunable switch and elastic wave filters at ultrasonic and hypersonic frequency ranges.

  2. 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

  3. 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.

  4. 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.

  5. Nonlinear Shear Instabilities in an Infinite Slab

    NASA Astrophysics Data System (ADS)

    Nepveu, M.

    1982-08-01

    The dynamical evolution of an infinite slab moving in denser and noisy (turbulent) surroundings is investigated with a 2D hydrodynamic code. The applicability of the results to astrophysical jets is discussed. Inviscid beams show internal shocks at regular intervals of a few beamwidths. Kinks are not obvious. In viscous beams shocks are less outspoken, but turbulence is triggered with maximum scales of a few beamwidths. These viscous beams broaden. Linear stability analysis may hold up to a few e-folding times, although the seed disturbance field is not infinitesimal. The computations suggest that viscous astrophysical beams may become blurred quite suddenly and may give rise to sudden change in radiation patterns (NGC 1265).

  6. 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.

  7. Across- and along-arc geochemical variations of lava chemistry in the Sangihe arc: Various fluid and melt slab fluxes in response to slab temperature

    NASA Astrophysics Data System (ADS)

    Hanyu, Takeshi; Gill, James; Tatsumi, Yoshiyuki; Kimura, Jun-Ichi; Sato, Keiko; Chang, Qing; Senda, Ryoko; Miyazaki, Takashi; Hirahara, Yuka; Takahashi, Toshiro; Zulkarnain, Iskandar

    2012-10-01

    The Sangihe arc, northern Indonesia, is an oceanic arc that is the western half of the only active arc-arc collision on Earth. To elucidate magma genesis and slab thermal structure in such a setting, we have obtained new geochemical data for lavas from the entire Sangihe arc. In the southern arc, the volcanic front lavas are enriched in fluid-mobile elements, while the rear arc lavas are more enriched in melt-mobile elements. The proportion of sediment versus altered oceanic crust in the slab component is only ˜20% but still larger in Sangihe than other arcs in the western Pacific such as Izu, suggesting more subduction of the thick sediments in the narrowing Molucca Sea. The slab component changes in character across the arc from low-temperature fluid, through high-temperature fluid, to partial melt during progressive subduction. The geochemical systematics, the estimated mass fraction of the slab component, and the inferred stability of accessory rutile, zircon, and phengite in the slab are all similar between the southern Sangihe and Izu arcs, indicating that the thermal structure of the slab is not affected by impending collision. In contrast, lavas from the dormant northern Sangihe arc show geochemical characteristics similar to the Quaternary rear arc rather than the Quaternary volcanic front lavas in the southern arc. This may be related to advanced collision in the northern arc that could have slowed the subduction rate and heated the slab in the Pliocene followed by cessation of volcanic activity in the Quaternary.

  8. Vibration characteristics of floating slab track

    NASA Astrophysics Data System (ADS)

    Kuo, Chen-Ming; Huang, Cheng-Hao; Chen, Yi-Yi

    2008-11-01

    Coupled equilibrium equations of suspended wheels and floating slab track system were solved with the fourth-order Runge-Kutta method to obtain the deflections, vibration velocities, and wheel-rail contact forces. The program was validated through several aspects. Cases with various vehicle speed, slab mass, and stiffness of slab bearing were analyzed to reveal the effects of slab bearing on track responses. The correlation between wheel-rail resonance and train speed was also discussed. It was found that rail deflections increase significantly as train speed increases. Although large slab mass may lower tuning frequency, it could also result in higher wheel-rail contact force and rail deflections. The floating slab track is effective in isolating loading above 10 Hz, which might present in some railway sections with irregularities. Adopting floating slab track for vibration control for environment along the railway may cause concerns about ride quality and track damages.

  9. Preface: Deep Slab and Mantle Dynamics

    NASA Astrophysics Data System (ADS)

    Suetsugu, Daisuke; Bina, Craig R.; Inoue, Toru; Wiens, Douglas A.

    2010-11-01

    We are pleased to publish this special issue of the journal Physics of the Earth and Planetary Interiors entitled "Deep Slab and Mantle Dynamics". This issue is an outgrowth of the international symposium "Deep Slab and Mantle Dynamics", which was held on February 25-27, 2009, in Kyoto, Japan. This symposium was organized by the "Stagnant Slab Project" (SSP) research group to present the results of the 5-year project and to facilitate intensive discussion with well-known international researchers in related fields. The SSP and the symposium were supported by a Grant-in-Aid for Scientific Research (16075101) from the Ministry of Education, Culture, Sports, Science and Technology of the Japanese Government. In the symposium, key issues discussed by participants included: transportation of water into the deep mantle and its role in slab-related dynamics; observational and experimental constraints on deep slab properties and the slab environment; modeling of slab stagnation to constrain its mechanisms in comparison with observational and experimental data; observational, experimental and modeling constraints on the fate of stagnant slabs; eventual accumulation of stagnant slabs on the core-mantle boundary and its geodynamic implications. This special issue is a collection of papers presented in the symposium and other papers related to the subject of the symposium. The collected papers provide an overview of the wide range of multidisciplinary studies of mantle dynamics, particularly in the context of subduction, stagnation, and the fate of deep slabs.

  10. Numerical Models of Subduction and Slab Detachment: Placing a Lower Bound on the Strength of Slabs

    NASA Astrophysics Data System (ADS)

    Billen, M. I.; Andrews, E.

    2007-12-01

    Subduction provides the main driving force for the motion of tectonic plates at the Earth's surface through slab- pull and sinking-induced flow in the surrounding mantle. The ability of the slab to directly transmit slab-pull forces to the tectonic plate at the surface depends on the minimum strength and rheology (e.g., viscous, plastic) of the slab. Previous models have shown that observations including the state of stress in slabs, dynamic topography and the geoid above slabs, the evolution of slab and the kinematic history of subduction can be well-matched by a variety of models with either low viscosity (i.e., 100-1,000 times more viscous than the surrounding mantle) or high viscosity slabs (i.e., more than 10,000 times more viscous than the surrounding mantle). However, in many of the models in which a good match to observations is found for low viscosity slabs, the maximum slab viscosity is imposed as a cut-off value, which forces the entire slab to have a more or less uniform viscosity independent of strain-rate or stress magnitude, rather than a plastic yielding-type rheology. We present numerical models demonstrating that when the non-Newtonian viscosity of the upper mantle and plastic yielding behavior of slabs are taken into account, the minimum yield strength that allows for continuous subduction is approximately 300- 500 MPa, which leads to high viscosity slabs with some localized lower viscosity regions. A yield stress of 10-100 MPa is required to form uniformly low viscosity slabs, but these slabs detach from the subducting plate, due to localized weakening, when the slab reaches a length of 200-300 km, even when subduction is facilitated by a low viscosity shear zone and kinematically-imposed surface velocities. In contrast, detachment of higher strength slabs in fully-dynamic models only occurs when the shear zone is removed and prevents further subduction.

  11. 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

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

    PubMed

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

    2011-05-17

    The second critical endpoint in the basalt-H(2)O 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

  13. 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

  14. 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.

  15. Dynamic uplift during slab flattening

    NASA Astrophysics Data System (ADS)

    Dávila, Federico M.; Lithgow-Bertelloni, Carolina

    2015-09-01

    Subduction exerts a strong control on surface topography and is the main cause of large vertical motions in continents, including past events of large-scale marine flooding and tilting. The mechanism is dynamic deflection: the sinking of dense subducted lithosphere gives rise to stresses that directly pull down the surface. Here we show that subduction does not always lead to downward deflections of the Earth's surface. Subduction of young lithosphere at shallow angles (flat subduction) leaves it neutrally or even positively buoyant with respect to underlying mantle because the lithosphere is relatively warm compared with older lithosphere, and because the thickened and hence drier oceanic crust does not undergo the transformation of basalt to denser eclogite. Accounting for neutrally buoyant flat segments along with large variations in slab morphology in the South American subduction zone explains along-strike and temporal changes in dynamic topography observed in the geologic record since the beginning of the Cenozoic. Our results show that the transition from normal subduction to slab flattening generates dynamic uplift, preventing back-arc marine flooding.

  16. 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.

  17. 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.

  18. 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.

  19. Looking east inside of the 44" slab mill building at ...

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

    Looking east inside of the 44" slab mill building at the red hot slabs being conveyed to the hot beds. - U.S. Steel Edgar Thomson Works, 44" Slab Mill, Along Monongahela River, Braddock, Allegheny County, PA

  20. A cryogenic slab CO laser

    SciTech Connect

    Ionin, Andrei A; Kozlov, A Yu; Seleznev, L V; Sinitsyn, D V

    2009-03-31

    A compact capacitive transverse RF-discharge-pumped slab CO laser with cryogenically cooled electrodes, which operates both in the cw and repetitively pulsed regimes, is fabricated. The laser operation is studied in the free running multifrequency regime at the vibrational - rotational transitions of the fundamental (V + 1 {yields} V) vibrational bands of the CO molecule in the spectral region from 5.1 to 5.4 {mu}m. Optimal operation conditions (gas mixture composition and pressure, RF pump parameters) are determined. It is shown that only gas mixtures with a high content of oxygen (up to 20% with respect to the concentration of CO molecules) can be used as an active medium of this laser. It is demonstrated that repetitively pulsed pumping is more efficient compared to cw pumping. In this case, quasi-cw lasing regime can be obtained. The maximum average output power of {approx}12 W was obtained for this laser operating on fundamental bands and its efficiency achieved {approx}14 %. The frequency-selective operation regime of the slab RF-discharge-pumped CO laser was realised at {approx} 100 laser lines in the spectral region from 5.0 to 6.5 {mu}m with the average output power of up to several tens of milliwatts in each line. Lasing at the transitions of the first vibrational overtone (V + 2 {yields} V) of the CO molecule is obtained in the spectral region from 2.5 to 3.9 {mu}m. The average output power of the overtone laser achieved 0.3 W. All the results were obtained without the forced gas mixture exchange in the discharge chamber. Under fixed experimental conditions, repetitively pulsed lasing (with fluctuations of the output characteristics no more than {+-}10 %) was stable for more than an hour. (lasers)

  1. On the Viability of Slab Melting

    NASA Astrophysics Data System (ADS)

    Van Hunen, J.; Bouilhol, P.; Magni, V.; Maunder, B. L.

    2014-12-01

    Melting subducted mafic crust is commonly assumed to be the main process leading to silicic melts with an adakitic signature, which may form Archaean granitoids and generate early continental crust. Alternatively, melting of the overriding lower mafic crust and near-Moho depth fractional crystallisation of mantle melts can form differentiated magmas with an adakitic signature. Previous work shows how only very young slabs melt through dehydration melting, or depict melting of dry eclogites via water addition from deeper slab dehydration. Alternatively, underplated subducted material via delamination and diapirism may be important in the generation of felsic continental crust. We quantify subduction dehydration and melting reactions in a warm subduction system using a thermo-mechanical subduction model with a thermodynamic database. We find that even young (hot) slabs dehydrate before reaching their solidus, which suppresses any slab dehydration melting and creates significant amounts of mantle wedge melting irrespective of slab age. Significant slab crust melting is only achieved in young slabs via water present melting if metamorphic fluids from the subducted mantle flux through the dry eclogites. These slab melts, however, interfere with massive mantle wedge melting and unlikely to participate in the overriding plate felsic magmatism, unlike the shallower, primitive mantle wedge melts. We also explore the conditions for delaminating the mafic subducted crust. For a wide range of ages, the uppermost part of the subducted slab might delaminate to form compositionally buoyant plumes that rise through the mantle wedge. Thick crust on young slabs (as perhaps representative for a hotter, early Earth) may delaminate entirely and reside in the mantle wedge. Under such conditions, this ponded crust might melts subsequently, forming "adakitic" felsic melts contributing to a significant amount of the overriding plate crustal volumes.

  2. 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.

  3. Cretaceous Arctic magmatism: Slab vs. plume? Or slab and plume?

    NASA Astrophysics Data System (ADS)

    Gottlieb, E. S.; Miller, E. L.; Andronikov, A. V.; Brumley, K.; Mayer, L. A.; Mukasa, S. B.

    2010-12-01

    Tectonic models for the Cretaceous paleogeographic evolution of the Arctic Ocean and its adjacent landmasses propose that rifting in the Amerasia Basin (AB) began in Jura-Cretaceous time, accompanied by the development of the High Arctic Large Igneous Province (HALIP). During the same timespan, deformation and slab-related magmatism, followed by intra-arc rifting, took place along the Pacific side of what was to become the Arctic Ocean. A compilation and comparison of the ages, characteristics and space-time variation of circum-Arctic magmatism allows for a better understanding of the role of Pacific margin versus Arctic-Atlantic plate tectonics and the role of plume-related magmatism in the origin of the Arctic Ocean. In Jura-Cretaceous time, an arc built upon older terranes overthrust the Arctic continental margins of North America and Eurasia, shedding debris into foreland basins in the Brooks Range, Alaska, across Chukotka, Russia, to the Lena Delta and New Siberian Islands region of the Russian Arctic. These syn-tectonic sediments have some common sources (e.g., ~250-300 Ma magmatic rocks) as determined by U-Pb detrital zircon geochronology. They are as young as Valanginian-Berriasian (~136 Ma, Gradstein et al., 2004) and place a lower limit on the age of formation of the AB. Subsequent intrusions of granitoid plutons, inferred to be ultimately slab-retreat related, form a belt along the far eastern Russian Arctic continental margin onto Seward Peninsula and have yielded a continuous succession of zircon U-Pb ages from ~137-95 Ma (n=28) and a younger suite ~91-82 Ma (n=16). All plutons dated were intruded in an extensional tectonic setting based on their relations to wall-rock deformation. Regional distribution of ages shows a southward migration of the locus of magmatism during Cretaceous time. Basaltic lavas as old as 130 Ma and as young as 80 Ma (40Ar/39Ar)) erupted across the Canadian Arctic Islands, Svalbard and Franz Josef Land and are associated with

  4. Slab Ice and Snow Flurries in the Mars Northern Polar Night

    NASA Technical Reports Server (NTRS)

    1999-01-01

    In the 1970s, spacecraft observations of the polar regions of Mars revealed polar brightness temperatures that were significantly below the expected kinetic temperatures for CO_2 sublimation. For the past few decades, we have speculated as to the nature of these Martian polar cold spots. Are the cold spots surface or atmospheric effects? Do the cold spots behave as blackbodies, or do they have emissivities less than unity? Two developments have allowed us to answer these questions: (1) the measurement of the optical constants of CO_2 by Gary Hansen (1997) and (2) direct thermal spectroscopy of the north polar cap by MGS TES (Kieffer et al., 1998).

    With a few possible excepts, cold spots are surface effects. The CO_2 frost in cold regions of the polar cap show a strong absorption feature at 25 microns that is indicative of fine-grained CO_2, thus explaining the low brightness temperatures observed by the Viking IRTM. Brightness temperatures at 18 microns are usually consistent with expected kinetic surface temperatures. In many cases, the brightness temperatures at 15 microns reveals an atmosphere that is too warm for CO_2 condensation to occur.

    Cold spot formation is strongly dependent on topography, forming preferentially near craters and on slopes of the perennial cap. While cold spots are surface effects, the formation of the fine-grained CO_2 deposits is not entirely restricted to surface formation. TES data, combined with MOLA cloud data (Ivanov and Muhleman, 1999), suggest that at least a few of these cold spots were formed from atmospheric condensates.

    Another major component to the north polar cap composition is slab CO_2 ice. Slab ice has near unity spectral emissivity (Kieffer et al.,1999; Hansen, 1998) and appears to have a low albedo. Two explanations for the low albedo are that the slab ice is intrinsically dark or the slab ice is transparent and we are seeing through to the underlying substrate. Regions of the cap where T_18-T_25 <5

  5. High Average Power Nd:YAG Slab Laser

    NASA Astrophysics Data System (ADS)

    Kasai, Takeshi; Sindo, Yoshihiko; Haga, Keiji

    1989-07-01

    A slab geometry Nd:YAG laser with a zigzag optical path is described. The dimensions of the Nd:YAG slab are 5.6 x 18.4 x 153.9 mm, and Nei' ion concentration is 1.1 at.%. Two krypton flashlamps, one located on each side of the YAG slab, are used for pumping. The conditions for normal pulsed operation were as follows: the repetition rate was from 5 to 27 pps, and the pulse durations were 4 and 9.9 ms. With the above conditions, a maximum average output power of 500 W was obtained with an efficiency of 2 %, the slope efficiency being 2.4 %. The beam divergence was estimated to be 10x25 mrad. The stability of the laser output power was about +/-1.5 %. Another oscillator that includes intra-cavity cylindrical lenses, was also designed. Using this resonator configuration reduced the beam divergence to about 7.6 x8.2 mrad. The preliminary laser processing experiment was attemped using this laser oscillator.

  6. 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.

  7. Detecting slab structure beneath the Mediterranean

    NASA Astrophysics Data System (ADS)

    Miller, Meghan S.; Sun, Daoyuan; Piana Agostinetti, Nicola

    2013-04-01

    The presence of subducted slabs in the Mediterranean has been well documented with seismic tomography, however, these images, which are produced by smoothed, damped inversions, underestimate the sharpness of the structures. The position and extent of the slabs and the presence possible tears or gaps in the subducted lithosphere are still debated, yet the shape and location these structures are important for kinematic reconstructions and evolution of the entire subduction zone system. Extensive distribution of broadband seismic instrumentation in the Mediterranean (Italian National Seismic Network in Italy and the NSF-PICASSO project in Spain and Morocco) has allowed us to use alternative methodologies to detect the position of the slabs and slab tears beneath the Central and Western Mediterranean. Using S receiver functions we are able to identify S-to-p conversions from the bottom of the subducted slab and a lack of these signals where there are gaps or tears in the slab. We also analyze broadband waveforms for changes in P wave coda from deep (> 300 km depth) local earthquakes. The waveform records for stations in southern Italy and around the Betic-Rif show large amplitude, high frequency (f > 5 Hz) late arrivals with long coda after relatively low-frequency onset. High frequency arrivals are the strongest from events whose raypaths travel within the slab to the stations where they are recorded allowing for mapping of where the subducted material is located within the upper mantle. These two methods, along with inferring the slab position from fast P-wave velocity perturbations in tomography and intermediate depth seismicity, provide additional geophysical evidence to aid in interpretation of the complex, segmented slab structure beneath the Mediterranean.

  8. Andean flat subduction maintained by slab tunneling

    NASA Astrophysics Data System (ADS)

    Schepers, Gerben; van Hinsbergen, Douwe; Kosters, Martha; Boschman, Lydian; McQuarrie, Nadine; Spakman, Wim

    2016-04-01

    In two segments below the Andean mountain belt, the Nazca Plate is currently subducting sub-horizontally below South America over a distance of 200-300 km before the plate bends into the mantle. Such flat slab segments have pronounced effects on orogenesis and magmatism and are widely believed to be caused by the downgoing plate resisting subduction due to its local positive buoyancy. In contrast, here we show that flat slabs primarily result from a local resistance against rollback rather than against subduction. From a kinematic reconstruction of the Andean fold-thrust belt we determine up to ~390 km of shortening since ~50 Ma. During this time the South American Plate moved ~1400 km westward relative to the mantle, thus forcing ~1000 km of trench retreat. Importantly, since the 11-12 Ma onset of flat slab formation, ~1000 km of Nazca Plate subduction occurred, much more than the flat slab lengths, which leads to our main finding that the flat slabs, while being initiated by arrival of buoyant material at the trench, are primarily maintained by locally impeded rollback. We suggest that dynamic support of flat subduction comes from the formation of slab tunnels below segments with the most buoyant material. These tunnels trap mantle material until tearing of the tunnel wall provides an escape route. Fast subduction of this tear is followed by a continuous slab and the process can recur during ongoing rollback of the 7000 km wide Nazca slab at segments with the most buoyant subducting material, explaining the regional and transient character of flat slabs. Our study highlights the importance of studying subduction dynamics in absolute plate motion context.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. Water in the Slab: a Trilogy

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    In this presentation we summarize the results of a project started in 2007 from a brilliant intuition of Luigi Burlini that suggested an additional anisotropy source for the interpretation of seismic anisotropy patterns observed at subduction zones. Such an anisotropic body located in the upper part of the slab would result from the hydration of the oceanic plate at the trench outer-rise. The natural continuation of the project was to understand the mechanical processes behind slab hydration and the fluid flow patterns established during slab dehydration. In both cases, we found that tectonic pressure gradients due to the bending and unbending of the subducting oceanic plate are fundamental in driving fluid flow. This last part of the project led to the other two chapters of the final trilogy about the long route of water in the slab. This trilogy is here described in detail and a chronologically ordered series of events presented below. The first episode is related to slab hydration occurring during bending at the trench-outer rise. Here, fluids are driven downward along active normal faults by bending-related, sub-hydrostatic pressure gradients. Water can percolate down to 15-20 km below the seafloor, triggering hydrothermal reactions and the formation of hydrous minerals. This results in an elongated pattern of mostly trench-dipping hydrated faults with a strike parallel to the trench and whose orientation below the forearc becomes sub-vertical. The second episode is related to the geophysical implications of a hydrated slab below the forearc. Indeed, both the subvertical layering of closely spaced hydrated and dry levels (SPO) and the syn-deformational, fault-parallel alignment of highly anisotropic minerals (CPO) such as serpentine and talc may contribute to the SKS splitting patterns observed in the forearc. We suggest that the upper part of the slab may have a strong seismic anisotropy that can be approximated by a transverse isotropic body with a sub

  17. Contribution of Elasticity in Slab Bending

    NASA Astrophysics Data System (ADS)

    Fourel, L.; Goes, S. D. B.; Morra, G.

    2014-12-01

    Previous studies have shown that plate rheology exerts a dominant control on the shape and velocity of subducting plates. Here, we perform a systematic investigation of the, often disregarded, role of elasticity in slab bending at the trench, using simple, yet fully dynamic, set of 2.5D models where an elastic, visco-elastic or visco-elasto-plastic plate subducts freely into a purely viscous mantle. We derive a scaling relationship between the bending radius of visco-elastic slabs and the Deborah number, De, which is the ratio of Maxwell time over deformation time. We show that De controls the ratio of elastically stored energy over viscously dissipated energy and find that at De exceeding 10-2, it requires substantially less energy to bend a visco-elastic slab to the same shape as a purely viscous slab with the same viscosity (90% less for De=0.1). Elastically stored energy at higher De facilitates slab unbending and hence favours retreating modes of subduction, while trench advance only occurs for some cases with De<10-2. We use our scaling relation to estimate apparent Deborah numbers, Deapp, from a global compilation of subduction-zone parameters. Values range from 10-3 to >1, where most zones have low Deapp<10-2, but a few young plates have Deapp>0.1. Slabs with Deapp ≤ 10-2 either have very low viscosities, ≤10 times mantle viscosity, or they may be yielding, in which case our apparent Deborah number may underestimate actual De by up to an order of magnitude. If a significant portion of the low Deapp slabs yield, then elastically stored energy may actually be important in quite a large number of subduction zones. Interestingly, increasing Deapp correlates with increasing proportion of larger seismic events (b-value) in both instrumental and historic catalogues, indicating that increased contribution of elasticity may facilitate rupture in larger, less frequent earthquakes.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Accidents due to falls from roof slabs.

    PubMed

    Rudelli, Bruno Alves; Silva, Marcelo Valerio Alabarce da; Akkari, Miguel; Santili, Claudio

    2013-01-01

    CONTEXT AND OBJECTIVE Falls from the roof slabs of houses are accidents of high potential severity that occur in large Brazilian cities and often affect children and adolescents. The aims of this study were to characterize the factors that predispose towards this type of fall involving children and adolescents, quantify the severity of associated lesions and suggest preventive measures. DESIGN AND SETTING Descriptive observational prospective longitudinal study in two hospitals in the metropolitan region of São Paulo. METHODS Data were collected from 29 cases of falls from roof slabs involving children and adolescents between October 2008 and October 2009. RESULTS Cases involving males were more prevalent, accounting for 84%. The predominant age group was schoolchildren (7 to 12 years old; 44%). Leisure activities were most frequently being practiced on the roof slab at the time of the fall (86%), and flying a kite was the most prevalent game (37.9%). In 72% of the cases, the children were unaccompanied by an adult responsible for them. Severe conditions such as multiple trauma and traumatic brain injuries resulted from 79% of the accidents. CONCLUSION Falls from roof slabs are accidents of high potential severity, and preventive measures aimed towards informing parents and guardians about the dangers and risk factors associated with this type of accident are needed, along with physical protective measures, such as low walls around the slab and gates with locks to restrict free access to these places. PMID:23903263

  3. Thermally induced phase changes, lateral heterogeneity of the mantle, continental roots, and deep slab anomalies

    NASA Technical Reports Server (NTRS)

    Anderson, Don L.

    1987-01-01

    Factors which influence the lateral heterogeneity in density and seismic velocity with depth in the upper earth mantle are discussed. It is emphasized that most of the increases in density and seismic velocity with depth are caused by pressure-induced solid-solid phase changes in the high-density high-velocity phases of mineral assemblage, due to variations in temperature. In particular, the ilmenite form of MgSiO3 and the gamma-spinel form of Mg2SiO4 have broad stability fields in cold mantle and are not stable in hotter mantle. It is emphasized that the density and velocity anomalies associated with temperature-induced phase changes in mineral assemblage must be taken into account in the thermal models of the slabs; when these effects are accounted for, the geoid and seismic anomalies associated with subducted slabs are consistent with slab confinement to the upper mantle and with layered models of mantle convection.

  4. Fluorescence losses from Yb:YAG slab lasers.

    PubMed

    Chen, Ying; Rapaport, Alexandra; Chung, Te-yuan; Chen, Bin; Bass, Michael

    2003-12-20

    We report on the distribution of fluorescence that can be emitted through the surfaces of a ytterbium-doped yttrium aluminum garnet (Yb:YAG) slab-shaped high-power solid-state laser. Slab shapes considered include parallel or antiparallel Brewster endfaced slabs and rectangular parallelepiped slabs. We treat cases in which all the faces of these slabs are in air, or with water or another coating on the largest faces. The fraction of the fluorescence emitted through each face, its distribution over that face, and the directions in which it travels are shown to be important to the design of high-power slab lasers. PMID:14717292

  5. Fatigue of concrete beams and slabs

    NASA Astrophysics Data System (ADS)

    Roesler, Jeffrey Raphael

    Traditionally, simply supported concrete beam (SSB) fatigue results have been used to characterize the fatigue resistance of fully supported concrete slabs (FSS). SSB concrete fatigue tests have been assumed to be equivalent to the fatigue resistance of concrete slabs in the field. The effect specimen size, boundary conditions, and loading configurations have on the fatigue of concrete beams and slabs have not been considered in the design of concrete pavements against fatigue. A laboratory study was undertaken to determine if the fatigue behavior of FSS and SSB were similar. A fully supported beam (FSB) was also tested under repeated loading, since it represented an intermediate specimen size and testing configuration between SSB and FSS. The best way to present fatigue results for all specimens was a stress ratio (S) to number of cycles to failure (N) curve (S-N curve). SSB fatigue behavior was similar to results obtained from the literature. FSB had similar fatigue behavior to SSB. The fatigue curve derived from repeated loading of FSS was 30 percent higher than the SSB fatigue curve. This suggested for a given number of cycles to failure, FSS could take a 30 percent higher bending stress as compared to SSB and FSB. The concrete modulus of rupture from a FSS test configuration was 30 percent greater than the concrete modulus of rupture from a SSB test setup. If the concrete modulus of rupture from a FSS test configuration was used in the slab's stress ratio, the slab's fatigue curve was the same as the SSB and FSB. This meant concrete behaved the same under fatigue loading, irrespective of specimen size and test configuration, as long as the correct concrete modulus of rupture was used in the stress ratio. Strain gages, attached to all specimens tested, indicated cracking in concrete occurred in a narrow band. Regions of high plastic strain were found in the plane of cracking, while adjacent areas experienced decreases in strain levels with cracking. Strain

  6. 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.

  7. Nd:glass slab laser for x-ray lithography

    NASA Astrophysics Data System (ADS)

    Reed, Murray K.; Byer, Robert L.

    1990-08-01

    A Nd:Glass laser has been used to generate laser produced plasmas (LLP). The plasma emission in the keV range useful for X-ray lithography has been measured. Lithography with sub-micron linewidths has been demonstrated with a thin absorbing mask. The Nd:Glass slab laser is operated in a Q-switched one-dimensional unstable resonator. The resulting beam quality is a few times diffraction limited and is focused to an area less than the lO cm2 in our vacuum chamber. We have operated at 5 J up to 4 Hz repetition rate without any degradation of the laser output. Injection mode locking of the Nd:Glass laser with 0.7 ns pulses increases the intensity of the Q-switched laser output by about a factor of 10 and allows us to achieve a total integrated pulse length of less than 10 ns. Optical damage limits the laser intensity. The damage threshold for injection mode locked pulses focused into a Nd:Glass slab outside the laser cavity is about 20 J/cm2. However, we have observed another damage mechanism at lower intensities in Nd:Glass slabs in use in the laser head. Brown discoloration occurs in filaments along the laser beam path and we believe solarization with the help of self-focusing and the ultra- violet flashlamp radiation may be occuring. We are still investigating this phenomenon but at present it is limiting the laser output to only 2 J per pulse. The focused laser intensity is 2.1013 W/cm2 on a solid copper target in our vacuum chamber. The plasma emission in the keV X-ray range has been measured through a variety of thin film X-ray filters with a Hamamatsu micro-channel plate detector. Using the published values for the detector quantum efficiency, the micro-channel plate gain, and the filter's transmission spectra, we estimate that the conversion efficiency in the plasma from laser radiation to soft X-rays of energy greater than 0.5 keV is around 2%. We have performed single-level demonstration exposures of PNMA resist through a 10 im thick aluminised Kapton debris

  8. Thickness Dependent Carrier Density at the Surface of SrTiO3 (111) Slabs

    SciTech Connect

    Sivadas, Mr. Nikhil; Dixit, Hemant M; Cooper, Valentino R; Xiao, Di

    2014-01-01

    We investigate the surface electronic structure and thermodynamic stability of the SrTiO3 (111) slabs using density functional theory. We observe that, for Ti-terminated slabs it is indeed possible to create a two-dimensional electron gas (2DEG). However, the carrier density of the 2DEG displays a strong thickness dependence due to the competition between electronic reconstruction and polar distortions. As expected, having a surface oxygen atom at the Ti termination can stabilize the system, eliminating any electronic reconstruction, thereby making the system insulating. An analysis of the surface thermodynamic stability suggests that the Ti terminated (111) surface should be experimentally realizable. This surface may be useful for exploring the behavior of electrons in oxide (111) interfaces and may have implications for modern device applications.

  9. 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…

  10. 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

  11. INTERIOR VIEW, LOOKING NORTHEAST, WITH OVENS AND SLAB BEING PROCESSED ...

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

    INTERIOR VIEW, LOOKING NORTHEAST, WITH OVENS AND SLAB BEING PROCESSED THROUGH PRESS/STECKLER (RIGHT). HEATED SLABS MAKE SEVERAL PASSES THROUGH THE STECKLER WITH THICKNESS OF THE SLAB DECREASED UNTIL REQUIRED GAGE IS REACHED. - Central Iron Foundry, Hot Strip Mill Building, 1700 Holt Road, Holt, Tuscaloosa County, AL

  12. Necessity of the Ridge for the Flat Slab Subduction: Insights from the Peruvian Flat Slab

    NASA Astrophysics Data System (ADS)

    Knezevic Antonijevic, S.; Wagner, L. S.; Beck, S. L.; Long, M. D.; Zandt, G.; Tavera, H.

    2014-12-01

    Flattening of the subducting plate has been linked to the formation of various geological features, 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]. However, the mechanism responsible for the slab flattening is still poorly understood. Here we focus on the Peruvian flat slab, where the Nazca plate starts to bend at ~80 km depth and travels horizontally for several hundred kilometers, at which point steep subduction resumes. Based on a 1500 km long volcanic gap and intermediate depth seismicity patterns, the Peruvian flat slab appears to have the greatest along-strike extent and, therefore, has been suggested as a modern analogue to the putative flat slab during the Laramide orogeny in the western United States (~80-55 Ma). Combining 3D shear wave velocity structure and Rayleigh wave phase anisotropy between ~10° and 18° S, we find that the subducting Nazca plate is not uniformly flat along the entire region, but fails to the north of the subducting Nazca Ridge. Our results show that, in combination with trench retreat, rapid overriding plate motion, and/or presence of a thick cratonic root, the subduction of buoyant overthickened oceanic crust, such as the Nazca Ridge, is necessary for the formation and sustainability of flat slabs. This finding has important implications for the formation of flat slabs both past and present.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. Effects of Thermodynamic Properties on Slab Evolution

    NASA Astrophysics Data System (ADS)

    Wada, I.; King, S. D.; Caddick, M. J.; Ross, N.

    2012-12-01

    We perform a series of numerical experiments to investigate the effects of thermodynamic properties on the geometrical evolution of subducting slabs. We calculate density (ρ), thermal expansivity (α), and heat capacity (cp) of mantle mineral assemblages of a harzburgite composition over a range of pressure and temperature conditions applicable to the Earth's mantle, using the thermodynamic database of Stixrude and Lithgow-Bertelloni [2011] and the thermodynamic calculation code Perple_X [Connolly, 2009]. Following Nakagawa et al. [2009], we assume that thermal diffusivity (κ) follows a power-law relationship with density (κ=κ0(ρ/ρ0)3, where κ0 and ρ0 are reference diffusivity and density, respectively). The calculations show that ρ, α, and κ change significantly along mantle geotherms; the ranges of their values are 3300-5100 km/m3, 1.5-3.5 10-5/K, and 3-17 W/m K, respectively. The change in cp is small (< 5%). We incorporate the pressure and temperature (PT) dependence of these thermodynamic properties into a 2-D finite element code with compressible convection formulations under the truncated anelastic liquid approximation [Lee and King, 2009] and develop a dynamic subduction model with kinematic boundary conditions. In the model, we use a composite mantle rheology that accounts for both diffusion and dislocation creep with flow law parameterization of wet olivine [Hirth and Kohlstedt, 2003]. Following Billen and Hirth [2007] and Lee and King [2011], we adjust the flow law parameter values for the lower mantle to test the effects of viscosity contrast between the upper and lower mantle on slab evolution. We use a reference model with a constant ρ, κ α, and cp, which is equivalent to using the incompressible extended Bousisnesq approximation. Preliminary results show that incorporating PT-dependent ρ enhances the vigor of the buoyancy driven flow compared to the reference model. Further, lithostatic pressure at a given depth is higher than in the

  18. The effect of metastable pyroxene on the slab dynamics

    NASA Astrophysics Data System (ADS)

    Agrusta, Roberto; Hunen, Jeroen; Goes, Saskia

    2014-12-01

    Seismic studies show that some subducting slabs penetrate straight into the lower mantle, whereas others seem to flatten near the base of the mantle transition zone. Slab stagnation is often attributed to an increase in viscosity and phase transformations in the olivine system. However, recent mineral physics studies showed that due to extremely low transformational diffusion rates, low-density metastable pyroxene may persist into the transition zone in cool slabs. Here we use a dynamically fully self-consistent subduction model to investigate the influence of metastable pyroxene on the dynamics of subducting oceanic lithosphere. Our results show that metastable pyroxene affects slab buoyancy at least as much as olivine metastability. However, unlike metastable olivine, which can inhibit slab penetration in the lower mantle only for cold, old, and fast slabs, metastable pyroxene is likely to also affect sinking of relatively young and slow slabs.

  19. 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

  20. 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.

  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. The Effect of Subducting Slabs in Global Shear Wave Tomography

    NASA Astrophysics Data System (ADS)

    Lu, Chang; Grand, Stephen P.

    2016-03-01

    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 travel time dataset for a theoretical slab model based on predicted thermal anomalies within slabs. The spectral element method 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 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%. 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%. 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 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 starting models in global

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. The 11 Micron Emissions of Carbon Stars

    NASA Astrophysics Data System (ADS)

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

    1995-08-01

    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, α: C-H, and MgS. In addition to the narrow 11+ microns emission feature that is commonly attributed to SiC, a broad 11+ microns emission feature, that is correlated with the 8.5 and 7.7 microns features, is found and attributed to α:C-H. SiC and α: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 α: C-H. If decreasing the temperature corresponds to a grain condensation sequence, then heterogeneous, or induced nucleation scenarios are supported. SiC grains precede α: 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 microns 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 microns 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, sp3, hydrocarbon bonds that may subsequently evolve into saturated bonds, sp2, 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 11.9 microns emission

  8. 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

  9. 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

  10. 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

  11. Dynamic buckling of subducting slabs reconciles geological and geophysical observations

    NASA Astrophysics Data System (ADS)

    Lee, Changyeol; King, Scott D.

    2011-12-01

    Ever since the early days of the development of plate tectonic theory, subduction zones have been engrained in geological thinking as the place where steady, linear slabs descend into the mantle at a constant, uniform dip angle beneath volcanic arcs. However, growing evidence from geological and geophysical observations as well as analog and numerical modeling indicates that subducting slabs buckle in a time-dependent manner, in contrast to the steady-state, linear cartoons that dominate the literature. To evaluate the implication of time-dependent slab buckling of geological events, we conduct a series of 2-D numerical dynamic/kinematic subduction experiments by varying the viscosity increase across the 660 km discontinuity and the strength of the subducting slab. Our results show that slab buckling is a universal figure in all the experiments when rate of the trench migration ( Vtrench) is relatively slow ( Vtrench| < 2 cm/a) and viscosity increases across the 660 km discontinuity are greater than a factor of 30. Slab buckling is expressed as alternate shallowing and steepening dip of the subducting slab (from ~ 40 to ~ 100°) which is correlated with increasing and decreasing convergent rate of the incoming oceanic plate toward the trench. Further, the slab buckling in our experiments is consistent with the previously developed scaling laws for slab buckling; using reasonable parameters from subducted slabs the buckling amplitude and period are ~ 400 km and ~ 25 Myr, respectively. The slab buckling behavior in our experiments explains a variety of puzzling geological and geophysical observations. First, the period of slab buckling is consistent with short periodic variations (~ 25 Myr) in the motions of the oceanic plates that are anchored by subduction zones. Second, the scattered distributions of slab dips (from ~ 20 to ~ 90°) in the upper mantle are snapshots of time-dependent slab dip. Third, the current compressional and extensional stress environments in

  12. Along-strike translation of a fossil slab

    NASA Astrophysics Data System (ADS)

    Pikser, Jacob E.; Forsyth, Donald W.; Hirth, Greg

    2012-05-01

    The Isabella anomaly is a high seismic velocity anomaly beneath the southern Central Valley of California that has previously been interpreted to represent a lithospheric drip or delaminated Sierra Nevada root. However, recent work suggests that the anomaly is a remnant slab, left over from Cenozoic subduction, attached to the Pacific plate underneath the edge of the North American plate. This hypothesis requires the slab to translate hundreds of kilometers along-strike while remaining intact and attached to the Pacific plate despite drag from the surrounding asthenosphere and overriding lithosphere. We use 3-D finite element models to simulate this scenario, and calculate the viscosity ratio between the slab and the surrounding asthenosphere required for the slab to translate undeformed. The required viscosity ratio increases with increasing downdip extent of the slab, and decreases with increasing slab dip; for geometries approximating that of our proposed slab, the required ratio ranges from 102 to 104. Given the thermal and petrologic history of the slab, mantle flow laws predict viscosity contrasts greater than or equal to these requirements. As such, we conclude that along-strike translation of a remnant slab is feasible, and serves as a possible explanation of the Isabella anomaly. The significance of this finding extends beyond our general understanding of subduction dynamics, in that the presence of such a slab could have implications for the water budget of the San Andreas Fault and its role in aseismic slip.

  13. Buoyancy, bending, and seismic visibility in deep slab stagnation

    NASA Astrophysics Data System (ADS)

    Bina, Craig R.; Kawakatsu, Hitoshi; Suetsugu, D.; Bina, C.; Inoue, T.; Wiens, D.; Jellinek, M.

    2010-11-01

    The petrological consequences of deep subhorizontal deflection ("stagnation") of subducting slabs should affect both apparent seismic velocity structures and slab morphology. We construct kinematic thermal models of stagnant slabs and perform thermodynamic modeling of the consequent perturbation of high-pressure phase transitions in mantle minerals, focusing upon Japan as our study area. We calculate associated thermo-petrological buoyancy forces and bending moments which (along with other factors such as viscosity variations and rollback dynamics) may contribute to slab deformation. We consider effects of variations in depth of stagnation, post-stagnation dip angle, phase transition sharpness, transition triplication due to multiple intersection of geotherms with phase boundaries, and potential persistence of metastable phases due to kinetic hindrance. We also estimate seismic velocity anomalies, as might be imaged by seismic tomography, and corresponding seismic velocity gradients, as might be imaged by receiver-function analysis. We find that buoyant bending moment gradients of petrological origin at the base of the transition zone may contribute to slab stagnation. Such buoyancy forces vary with the depth at which stagnation occurs, so that slabs may seek an equilibrium slab stagnation depth. Metastable phase bending moment gradients further enhance slab stagnation, but they thermally decay after ∱/4600•700 km of horizontal travel, potentially allowing stagnant slabs to descend into the lower mantle. Stagnant slabs superimpose zones of negative velocity gradient onto a depressed 660-km seismic discontinuity, affecting the seismological visibility of such features. Seismologically resolvable details should depend upon both stagnation depth and the nature of the imaging technique (travel-time tomography vs. boundary-interaction phases). While seismic tomography appears to yield images of stagnant slabs, discontinuity topography beneath Japan resolved by

  14. Evolution and diversity of subduction zones controlled by slab width.

    PubMed

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

    2007-03-15

    Subducting slabs provide the main driving force for plate motion and flow in the Earth's mantle, and geodynamic, seismic and geochemical studies offer insight into slab dynamics and subduction-induced flow. Most previous geodynamic studies treat subduction zones as either infinite in trench-parallel extent (that is, two-dimensional) or finite in width but fixed in space. Subduction zones and their associated slabs are, however, limited in lateral extent (250-7,400 km) and their three-dimensional geometry evolves over time. Here we show that slab width controls two first-order features of plate tectonics-the curvature of subduction zones and their tendency to retreat backwards with time. Using three-dimensional numerical simulations of free subduction, we show that trench migration rate is inversely related to slab width and depends on proximity to a lateral slab edge. These results are consistent with retreat velocities observed globally, with maximum velocities (6-16 cm yr(-1)) only observed close to slab edges (<1,200 km), whereas far from edges (>2,000 km) retreat velocities are always slow (<2.0 cm yr(-1)). Models with narrow slabs (< or =1,500 km) retreat fast and develop a curved geometry, concave towards the mantle wedge side. Models with slabs intermediate in width ( approximately 2,000-3,000 km) are sublinear and retreat more slowly. Models with wide slabs (> or =4,000 km) are nearly stationary in the centre and develop a convex geometry, whereas trench retreat increases towards concave-shaped edges. Additionally, we identify periods (5-10 Myr) of slow trench advance at the centre of wide slabs. Such wide-slab behaviour may explain mountain building in the central Andes, as being a consequence of its tectonic setting, far from slab edges. PMID:17361181

  15. 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

  16. 8- to 13-micron spectra of asteroids

    NASA Astrophysics Data System (ADS)

    Green, S. F.; Eaton, N.; Aitken, D. K.; Roche, P. F.; Meadows, A. J.

    1985-05-01

    It is pointed out that thermal emission from asteroids reaches a maximum in the 10- to 20-micron region. In connection with the present investigation, a uniform set of spectra was obtained in the 8- to 13-micron region for 12 asteroids (together with additional observations of 19 Fortuna). These spectra provide a potentially valuable data set for future use (e.g., with IRAS data). The main conclusion from the obtained results is that diagnostic emission features of the type observed by Feierberg et al. (1983) are not common in C- and M-type asteroids. Optical studies of 19 Fortuna do not reveal any unusual properties which distinguish it from other C-type asteroids observed.

  17. 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.

  18. The 2 micron plasmid purloins the yeast cohesin complex

    PubMed Central

    Mehta, Shwetal; Yang, Xian Mei; Chan, Clarence S.; Dobson, Melanie J.; Jayaram, Makkuni; Velmurugan, Soundarapandian

    2002-01-01

    The yeast 2 micron plasmid achieves high fidelity segregation by coupling its partitioning pathway to that of the chromosomes. Mutations affecting distinct steps of chromosome segregation cause the plasmid to missegregate in tandem with the chromosomes. In the absence of the plasmid stability system, consisting of the Rep1 and Rep2 proteins and the STB DNA, plasmid and chromosome segregations are uncoupled. The Rep proteins, acting in concert, recruit the yeast cohesin complex to the STB locus. The periodicity of cohesin association and dissociation is nearly identical for the plasmid and the chromosomes. The timely disassembly of cohesin is a prerequisite for plasmid segregation. Cohesin-mediated pairing and unpairing likely provides a counting mechanism for evenly partitioning plasmids either in association with or independently of the chromosomes. PMID:12177044

  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. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Slab coupled optical fiber sensor calibration

    NASA Astrophysics Data System (ADS)

    Whitaker, B.; Noren, J.; Chadderdon, S.; Wang, W.; Forber, R.; Selfridge, R.; Schultz, S.

    2013-02-01

    This paper presents a method for calibrating slab coupled optical fiber sensors (SCOS). An automated system is presented for selecting the optimal laser wavelength for use in SCOS interrogation. The wavelength calibration technique uses a computer sound card for both the creation of the applied electric field and the signal detection. The method used to determine the ratio between the measured SCOS signal and the applied electric field is also described along with a demonstration of the calibrated SCOS involving measuring the dielectric breakdown of air.

  7. Observation of the Early Transition from Slab to mixed Slab-Toroidal ETG Turbulence

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    Parametric studies of the transition between the slab branch of electron temperature gradient (ETG) mode and the mixed slab-toroidal branch of the ETG mode in CLM are reported. CLM was operated in a mirror machine configuration with a cell length of 50--100 cm, and a mirror ratio of 1--2. For typical CLM parameters and a mode localized at r = 2 cm this provides a range for inverse radius of curvature Rc - 1 between 0 and .006 cm-1. Under normal conditions theory predicts transition between slab and toroidal modes would occur when the parameter k| |Rc / 2k⊥ ρ ~ 1. Recent experiments have obtained an experimental scaling of mode amplitude and frequency as a function of Rc - 1. They indicate that even for much more modest levels of k| |Rc / 2k⊥ ρ ~ . 1 , there are substantial increases in saturated mode, up to 5 times larger than the pure slab mode. Changes in real frequency in the mode are generally small, on the order of <5%. This research was supported by the Department of Electrical Engineering of Columbia University.

  8. 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.

  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. 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.

  12. 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

  13. The Equivalent Slab Thickness of Mars' Ionosphere

    NASA Astrophysics Data System (ADS)

    Mendillo, M.; Lawler, G.; Narvaez, C.; Kofman, W.; Mouginot, J.; Morgan, D.; Gurnett, D.

    2014-04-01

    The integral with height of an electron density profile, called the ionospheric total electron content (TEC), is dominated by plasma near the height of maximum electron density (Nmax). The ratio τ = TEC/Nmax has a unit of distance, representing the thickness of a slab of plasma of uniform density (Nmax) with the same TEC. At Earth, the parameter τ has been found to vary far less than either Nmax or TEC, and thus models of τ can be used to generate values of TEC or Nmax when only one is observed. For an ionospheric layer dominated by photo-chemical processes, τ has also been related to the scale height of the neutral gas (H = kT/mg) that is ionized by sunlight. The MARSIS radio science package on the Mars Express satellite has produced large independent data sets of TEC and Nmax. We have used them to form slab thickness patterns versus phase of the solar cycle and solar zenith angle. The overall sample average for daytime (SZA < 90o) conditions is < τ >day = 71 ± 21 km, and for SZA between 90o - 100o, < τ >terminator = 55 ± 25 km. We will report on the possible use of τ patterns to infer characteristics of the martian ionosphere and thermosphere.

  14. Slab Profile Encoding (PEN) for Minimizing Slab Boundary Artifact in 3D Diffusion-Weighted Multislab Acquisition*

    PubMed Central

    Van, Anh T; Aksoy, Murat; Holdsworth, Samantha J; Kopeinigg, Daniel; Vos, Sjoerd B; Bammer, Roland

    2014-01-01

    Purpose To propose a method for mitigating slab boundary artifacts in 3D multislab diffusion imaging with no or minimal increases in scan time. Methods The multislab acquisition was treated as parallel imaging acquisition where the slab profiles acted as the traditional receiver sensitivity profiles. All the slabs were then reconstructed simultaneously along the slab direction using Cartesian-based sensitivity encoding (SENSE) reconstruction. The slab profile estimation was performed using either a Bloch simulation or a calibration scan. Results Both phantom and in vivo results showed negligible slab boundary artifacts after reconstruction using the proposed method. The performance of the proposed method is comparable to the state-of-the-art slab combination method without the scan time penalty that depends on the number of acquired volumes. The obtained g-factor map of the SENSE reconstruction problem showed a maximum g-factor of 1.7 in the region of interest. Conclusion We proposed a novel method for mitigating slab boundary artifacts in 3D diffusion imaging by treating the multislab acquisition as a parallel imaging acquisition and reconstructing all slabs simultaneously using Cartesian SENSE. Unlike existing methods, the scan time increase, if any, does not scale with the number of image volumes acquired. PMID:24691843

  15. 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). ).

  16. Optical isolators for 2-micron fibre lasers

    NASA Astrophysics Data System (ADS)

    Stevens, Gary; Legg, Thomas H.; Shardlow, Peter

    2015-02-01

    We report on the development and testing of optical isolators for use in 2-micron fiber laser systems. A variety of potential Faraday rotator materials were characterised to identify the most suitable materials for use in the 1700-2100nm wavelength range. Isolators based on the three best performing materials were then developed and packaged as fiber-in, fiber-out and fiber-in, beam-out devices. The isolators were then tested in CW, pulsed and ultrafast laser systems. The three different designs produced different performance characteristics, but all designs demonstrated isolation >25dB and insertion losses of <1.2 dB.

  17. 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.

  18. 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

  19. 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.

  20. The Two Micron All Sky Survey

    NASA Astrophysics Data System (ADS)

    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.

    1994-07-01

    The Two Micron All Sky Survey (2MASS) will provide a uniform survey of the entire sky at three near-infrared wavebands: J(lambdaeff = 1.25 micrometers), H(lambdaeff = 1.65 micrometers), and Ks(lambdaeff = 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.

  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. 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.

  3. The gravitational field of an infinite flat slab

    NASA Astrophysics Data System (ADS)

    Fulling, S. A.; Bouas, J. D.; Carter, H. B.

    2015-08-01

    We study Einstein's equations with a localized plane-symmetric source, with close attention to gauge freedom/fixing and to listing all physically distinct solutions. In the vacuum regions there are only two qualitatively different solutions, one curved and one flat; in addition, on each of the two sides there is a free parameter describing how the slab is embedded into the vacuum region. Surprisingly, for a generic slab source the solution must be curved on one side and flat on the other. We treat infinitely thin slabs in full detail and indicate how thick slabs can increase the variety of external geometry pairs. Positive energy density seems to force external geometries with curvature singularities at some distance from the slab; we speculate that such singularities occur in regions where the solution cannot be physically relevant anyway.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. Slab anisotropy from subduction zone guided waves in Taiwan

    NASA Astrophysics Data System (ADS)

    Chen, K. H.; Tseng, Y. L.; Hu, J. C.

    2014-12-01

    Frozen-in anisotropic structure in the oceanic lithosphere and faulting/hydration in the upper layer of the slab are expected to play an important role in anisotropic signature of the subducted slab. Over the past several decades, despite the advances in characterizing anisotropy using shear wave splitting method and its developments, the character of slab anisotropy remains poorly understood. In this study we investigate the slab anisotropy using subduction zone guided waves characterized by long path length in the slab. In the southernmost Ryukyu subduction zone, seismic waves from events deeper than 100 km offshore northern Taiwan reveal wave guide behavior: (1) a low-frequency (< 1 Hz) first arrival recognized on vertical and radial components but not transverse component (2) large, sustained high-frequency (3-10 Hz) signal in P and S wave trains. The depth dependent high-frequency content (3-10Hz) confirms the association with a waveguide effect in the subducting slab rather than localized site amplification effects. Using the selected subduction zone guided wave events, we further analyzed the shear wave splitting for intermediate-depth earthquakes in different frequency bands, to provide the statistically meaningful shear wave splitting parameters. We determine shear wave splitting parameters from the 34 PSP guided events that are deeper than 100 km with ray path traveling along the subducted slab. From shear wave splitting analysis, the slab and crust effects reveal consistent polarization pattern of fast directions of EN-WS and delay time of 0.13 - 0.27 sec. This implies that slab anisotropy is stronger than the crust effect (<0.1 s) but weaker than the mantle wedge and sub-slab mantle effect (0.3-1.3 s) in Taiwan.

  9. Along-strike translation of a fossil slab

    NASA Astrophysics Data System (ADS)

    Eichenbaum-Pikser, J. M.; Forsyth, D. W.; Hirth, G.

    2011-12-01

    The Isabella anomaly is a high seismic velocity anomaly beneath the southern Central Valley of California. Breaking from previous interpretations of the anomaly as a lithospheric drip (Zandt and Carrigan, 1993) or delaminated Sierra Nevada root (Zandt et al., 2004), Forsyth et al. (2011) propose that it is a remnant slab, left over from Cenozoic subduction, attached to the Monterey microplate and translating along-strike with the Pacific plate underneath the edge of the North American plate. This hypothesis requires the slab to translate hundreds of kilometers along strike while remaining intact and attached to the Pacific plate despite drag from the surrounding asthenosphere and overriding lithosphere. Using COMSOL Multiphysics, we design 3-D finite element fluid flow models to simulate this scenario, and calculate the viscosity ratio required between the slab and the surrounding asthenosphere in order for the slab to translate undeformed. The ratio needed increases with downdip extent of the slab, and decreases with slab dip; for geometries approximating that of our proposed slab, it ranges from 10^2 to 10^4. Given the thermal and hydrological history of the slab, mantle flow laws predict viscosity contrasts greater than or equal to these requirements. As such, we conclude that along-strike translation of a remnant slab is entirely feasible, and serves as possible explanation of the Isabella anomaly. The significance of this finding extends beyond our general understanding of subduction dynamics, in that the presence of such a slab could have interesting implications for the water budget of the San Andreas Fault and its role in aseismic slip.

  10. 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.

  11. Melting features along the western Ryukyu slab edge (northeast Taiwan) and Ryukyu slab tear (southernmost Okinawa Trough): Seismic evidence

    NASA Astrophysics Data System (ADS)

    Lin, J.; Hsu, S.; Sibuet, J.

    2003-12-01

    Behind the sedimentary Ryukyu arc lies the Okinawa Trough whose termination is located at the tip of the Ilan plain (northern Taiwan), just above the Ryukyu slab edge. The present-day active volcanic front, located 80-100 km above the Ryukyu slab, extends from Japan to Kueishantao Island, an islet situated 10-km offshore the Ilan plain. 3370 earthquakes recorded in northern Taiwan by 65 seismic land stations between December 1990 and May 1999 were used to determine the 3-D Vp and Vs velocity structures and Vp/Vs ratios. A low Vp, low Vs and high Vp/Vs sausage like body, about 20 km in diameter, lies within the Eurasian mantle wedge, on top of the western Ryukyu slab extremity, from depths ranging between 20 km and 100 km. We suggest that the friction of the Ryukyu slab edge against the Eurasian lithosphere and/or the upwelling of the underlying Philippine Sea plate lithospheric mantle around the slab edge would cause an abnormal heating resulting in the formation of partial melt. Part of this melt feeds obliquely the Kueishantao andesitic Island. An abnormal amount of volcanism occurs within the Okinawa Trough, east of a slab tear located 140 km from the Ryukyu slab edge. The power spectrum analysis of magnetic data shows the presence of a thick crust located above the slab tear, suggesting that a similar pattern to the one identified above of the Ryukyu slab edge might exist in the slab tear region, feeding obliquely this area of abnormal volcanism.

  12. Decarbonation of subducting slabs: insight from thermomechanical-petrological numerical modelling

    NASA Astrophysics Data System (ADS)

    Gonzalez, Christopher M.; Gorczyk, Weronika; Gerya, Taras

    2015-04-01

    This work extends a numerical geodynamic modelling code (I2VIS) to simulate subduction of carbonated lithologies (altered basalts and carbonated sediments) into the mantle. Code modifications now consider devolatilisation of H2O-CO2 fluids, a CO2-melt solubility parameterisation for molten sediments, and allows for carbonation of mantle peridotites. The purpose is to better understand slab generated CO2 fluxes and consequent subduction of carbonates into the deep mantle via numerical simulation. Specifically, we vary two key model parameters: 1) slab convergence rate (1,2,3,4,5 cm y-1) and 2) converging oceanic slab age (20,40,60,80 Ma) based on a half-space cooling model. The aim is to elucidate the role subduction dynamics has (i.e., spontaneous sedimentary diapirism, slab roll-back, and shear heating) with respect to slab decarbonation trends not entirely captured in previous experimental and thermodynamic investigations. This is accomplished within a fully coupled petrological-thermomechanical modelling framework utilising a characteristics-based marker-in-cell technique capable of solving visco-plastic rheologies. The thermodynamic database is modified from its original state to reflect the addition of carbonate as CO2 added to the rock's overall bulk composition. Modifications to original lithological units and volatile bulk compositions are as follows: GLOSS average sediments (H2O: 7.29 wt% & CO2: 3.01 wt%), altered basalts (H2O: 2.63 wt% & CO2: 2.90 wt%), and metasomatised peridotite (H2O: 1.98 wt% & CO2: 1.5 wt%). We resolve stable mineralogy and extract rock properties via PerpleX at a resolution of 5K and 25 MPa. Devolatilisation/consumption and stability of H2O-CO2 fluid is determined by accessing the thermodynamic database. When fluid is released due to unstable conditions, it is tracked via markers that freely advect within the velocity field until consumed. 56 numerical models were completed and our results show excellent agreement in dynamics with

  13. 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.

  14. Analytical and numerical treatment of drift-tearing and resistive drift instabilities in plasma slab

    NASA Astrophysics Data System (ADS)

    Mirnov, V. V.; Hegna, C. C.; Sauppe, J. P.; Sovinec, C. R.

    2015-11-01

    We consider modification to linear resistive MHD instability theory in a slab due to two categories of non-MHD effects: (1) electron and ion diamagnetic flows caused by equilibrium pressure gradients and (2) electron and ion decoupling on short scales associated with kinetic Alfven and whistler waves. The relationship between the expected stabilizing response due to the effects (1) and the destabilizing contribution caused by the dispersive waves (2) is investigated. An analytic solution combining the effect of diamagnetic flows and the ion-sound gyroradius contribution is derived using a perturbative approach. Linear numerical simulations using the NIMROD code are performed with cold ions and hot electrons in plasma slab with a doubly periodic box bounded by two perfectly conducting walls. Configurations with magnetic shear are unstable to current-driven drift-tearing instability. A second linearly unstable resistive drift type mode with largely electrostatic perturbations is also observed in simulations. The resistive-drift mode is suppressed by magnetic shear in unbounded domains but can remain unstable in the simulations with finite slab thickness and perfectly conducting wall. Additionally, the growth rate is sensitive to the magnetic shear length. We analyze whether these modes can be unstable in cylindrical configurations with magnetic shear typical for reversed field pinches. The material is based on work supported by the U.S. DOE and NSF.

  15. A dipping, thick Farallon slab below central United States

    NASA Astrophysics Data System (ADS)

    Sun, D.; Gurnis, M.; Saleeby, J.; Helmberger, D. V.

    2015-12-01

    It has been hypothesized that much of the Laramide orogeny was caused by dynamic effects induced by an extensive flat slab during a period of plateau subduction. A particularly thick block containing the Shatsky Rise conjugate, now in the mid-mantle, left a distinctive deformation footprint from southern California to Denver, Colorado. Thus mid-mantle, relic slabs can provide fundamental information about past subduction and the history of plate tectonics if properly imaged. Here we find clear evidence for a northeastward dipping (35° dip), slab-like, but fat (up to 400-500 km thick) seismic anomaly within the top of the lower mantle below the central United States. Using a deep focus earthquake below Spain with direct seismic paths that propagate along the top and bottom of the anomaly, we find that the observed, stacked seismic waveforms recorded with the dense USArray show multi-pathing indicative of sharp top and bottom surfaces. Plate tectonic reconstructions in which the slab is migrated back in time suggest strong coupling of the slab to North America. In combination with the reconstructions, we interpret the structure as arising from eastward dipping Farallon subduction at the western margin of North America during the Cretaceous, in contrast with recent interpretations. The slab could have been fattened through a combination of pure shear thickening during flat-slab subduction and a folding instability during penetration into the lower mantle.

  16. 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)

  17. 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

  18. Performance of a 500 watt Nd:GGG zigzag slab oscillator

    SciTech Connect

    Zapata, L.; Manes, K.R.; Christie, D.; Davin, J.; Blink, J.; Penland, J.; Demaret, R.; Dallum, G.

    1990-01-12

    Realization of practical multi-kilowatt Nd:garnet lasers will require the scale-up of crystal dimensions as well as more powerful pumping sources. A high average power zigzag slab crystal amplifier testing facility has been established at LLNL which employs two 100 kW{sub e} vortex stabilized arc lamps, cooled reflectors and a cooled, spectrally filtered, crystal slab mounting fixture. The operational characteristics of the first crystal laser to be tested in this setup, a Nd:GGG zigzag oscillator, are presented. A Nd:GGG crystal of dimensions 18 {times} 7 {times} 0.5 cm{sup 3}, doped at 2 {times} 10{sup 20} cm{sup {minus}3} Nd{sup 3+} atomic density, was pumped by up to 40 kW of filtered argon line emission. A small-signal single pass gain (losses excluded) of 1.09 was measured with a probe laser when the DC input to the lamps was 43 kW{sub e}. Our power supply was then modified to operate in a pulsed mode and provided one to three milliseconds pulses at 120 Hz. An average optical output power of 490 watts was obtained at a lamp input power of 93 kW{sub e} in an unoptimized resonator. The laser output power declined after a few tens of seconds since the slab tips were not properly cooled. A birdhouse specular lamp reflector and a contoured diffuse reflector were tested; in both cases the pump illuminated crystal surface was smaller than the total crystal face area. Fluorescence imaging of the zigzag amplifier's output aperture registered a smoother, more uniform pumping profile when the diffuse reflector was used. Uniformity of pumping results in decreased resonator loss and yields higher laser output power. Thermo-optic distortions observed in these preliminary tests are analyzed with the aid of computer simulations of the thermal fields, stresses, and surface displacements of our crystal slab. 3 refs., 12 figs.

  19. Modelling Gravitational Instabilities: Slab Break-off and Rayleigh-Taylor Diapirism

    NASA Astrophysics Data System (ADS)

    Zlotnik, Sergio; Fernández, Manel; Díez, Pedro; Vergés, Jaume

    2008-08-01

    A non-standard new code to solve multiphase viscous thermo-mechanical problems applied to geophysics is presented. Two numerical methodologies employed in the code are described: A level set technique to track the position of the materials and an enrichment of the solution to allow the strain rate to be discontinuous across the interface. These techniques have low computational cost and can be used in standard desktop PCs. Examples of phase tracking with level set are presented in two and three dimensions to study slab detachment in subduction processes and Rayleigh-Taylor instabilities, respectively. The modelling of slab detachment processes includes realistic rheology with viscosity depending on temperature, pressure and strain rate; shear and adiabatic heating mechanisms; density including mineral phase changes and varying thermal conductivity. Detachment models show a first prolonged period of thermal diffusion until a fast necking of the subducting slab results in the break-off. The influence of several numerical and physical parameters on the detachment process is analyzed: The shear heating exerts a major influence accelerating the detachment process, reducing the onset time to one half and lubricating the sinking of the detached slab. The adiabatic heating term acts as a thermal stabilizer. If the mantle temperature follows an adiabatic gradient, neglecting this heating term must be included, otherwise all temperature contrasts are overestimated. As expected, the phase change at 410 km depth (olivine-spinel transition) facilitates the detachment process due to the increase in negative buoyancy. Finally, simple plume simulations are used to show how the presented numerical methodologies can be extended to three dimensions.

  20. 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.

  1. Aprepitant loaded solid preconcentrated microemulsion for enhanced bioavailability: A comparison with micronized Aprepitant.

    PubMed

    Kamboj, Sunil; Sharma, Radhika; Singh, Kuldeep; Rana, Vikas

    2015-10-12

    Aprepitant (APT) is a lipophilic, poorly water soluble drug with moderate permeability characteristic. Therefore, we aimed to improve solubility as well as permeability that could possibly improve oral bioavailability of APT. For this purpose, Quality by design (QbD) approach employing simplex lattice mixture design was used to prepare solid preconcentrated microemulsion (S-PCM). Further, the software generated numerically optimized S-PCM formulations were developed by utilizing desirability function. The spectral attributes (powder X-ray diffraction, ATR-FTIR, and differential scanning calorimetry) of S-PCM formulations suggested that APT was present in amorphous form. The results of droplet size (150-180 nm), zeta potential (-13 to -15 mV), poly dispersity index (PDI) (0.211-0.238) and emulsification time (<1 min), of these S-PCM formulations (SP1, SP2 and SP3) suggested spherical shape morphology (Transmission electron microscopy) with thermodynamic stability. The comparison of in vitro/ex vivo behavior of S-PCM (SP1) with micronized and non-micronized formulations of APT suggested 2-fold and 5-fold enhancement in solubility and permeability, respectively. This was further evident from pharmacokinetic studies in rabbits that showed 1.5-fold enhancement in bioavailability of S-PCM with respect to micronized APT. Thus, it could be envisaged that development of S-PCM formulation of APT is the best alternative to micronization technology based APT formulations reported earlier. PMID:26165621

  2. 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.

  3. Tunable one-dimensional photonic crystal slabs

    NASA Astrophysics Data System (ADS)

    Beccherelli, R.; Bellini, B.; Zografopoulos, D.; Kriezis, E.

    2007-05-01

    A 1D photonic crystal slab based on preferential etching of commercially available silicon-on-insulator wafers is presented. Compared to dry etching, anisotropic wet etching is more tolerant to errors as it is self-stopping on crystallographic {111} planes and it produces a more precise geometry with symmetries and homothetic properties, with surface roughness close to 1 nm. The resulting grooves are infiltrated by low viscosity liquid crystal having large positive optical anisotropy. The use of slanted grooves provides advantages: first of all the complete filling of slanted grooves is simplified when compared to vertical walls structures. Furthermore alignment is significantly facilitated. Indeed the liquid crystal molecules tend to align with their long axis along the submicron grooves. Therefore by forcing reorientation out of a rest position, the liquid crystal presents a choice of refractive indices to the propagating optical field. The liquid crystal behavior is simulated by a finite element method, and coupled to a finite difference time domain method. We investigate different photonic crystal configurations. Large tunability of bandgap edge for TE polarization is demonstrated when switching the liquid crystal with an applied voltage. We have also studied the use of the same device geometry as a very compact microfluidic refractometric sensor.

  4. 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.

  5. 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.

  6. 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.

  7. Diode-pumped efficient slab laser with two Nd:YLF crystals and second-harmonic generation by slab LBO.

    PubMed

    Li, Daijun; Ma, Zhe; Haas, Rüdiger; Schell, Alexander; Simon, Janosch; Diart, Robert; Shi, Peng; Hu, Peixin; Loosen, Peter; Du, Keming

    2007-05-15

    We demonstrate a diode-pumped electro-optical Q-switched slab laser with a high optical efficiency, high pulse energy, and short pulse width with two Nd:YLF crystals inside one resonator. The single compact slab resonator can generate a 1D top-hat beam at both the far field and the near field. With a slab-geometry-design lithium triborate (LBO) crystal, efficient critical phase-matching second-harmonic generation for a 1D top-hat beam with multiple transverse modes is achieved. PMID:17440558

  8. 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

  9. 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

  10. 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

  11. 7. NO. 2 CONTINUOUS SLAB REHEATING FURNACE OF THE 160' ...

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

    7. NO. 2 CONTINUOUS SLAB REHEATING FURNACE OF THE 160' PLATE MILL. INTERIOR REFRACTORY LINING VISIBLE BECAUSE OF DEMOLITION. - U.S. Steel Homestead Works, 160" Plate Mill, Along Monongahela River, Homestead, Allegheny County, PA

  12. PERSPECTIVE OF UNDERSIDE SHOWING ARCHED GIRDER AND SLAB CONSTRUCTION. NOTE ...

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

    PERSPECTIVE OF UNDERSIDE SHOWING ARCHED GIRDER AND SLAB CONSTRUCTION. NOTE TWISTED BAR STOCK REINFORCING CAN BE SEEN. - Keggereis Ford Bridge, Spanning West Branch Conococheague Creek at State Route 4006, Willow Hill, Franklin County, PA

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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

  18. 14. LOOKING NORTHWEST THROUGH WOODS TOWARD THE SLAB AND BUTTRESS ...

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

    14. LOOKING NORTHWEST THROUGH WOODS TOWARD THE SLAB AND BUTTRESS SECTION. NEW DAM MODIFICATIONS WILL IMPACT THIS AREA. - Pit 4 Diversion Dam, Pit River west of State Highway 89, Big Bend, Shasta County, CA

  19. 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.

  20. 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

  1. 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

  2. A VIEW OF FOUNDATION (SLAB ON GRADE) WITH SCALE POLE ...

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

    A VIEW OF FOUNDATION (SLAB ON GRADE) WITH SCALE POLE LOOKING INTO SPRINKLER BOX ON EAST SIDE OF BUILDING (01/03/2008) - Wake Island Airfield, Terminal Building, West Side of Wake Avenue, Wake Island, Wake Island, UM

  3. 10. REINFORCED CONCRETE SLAB ROOF FROM SOUTHEASTERN EDGE, ACCESS RAMPS ...

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

    10. REINFORCED CONCRETE SLAB ROOF FROM SOUTHEASTERN EDGE, ACCESS RAMPS AT LEFT AND RIGHT, 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

  4. 11. REINFORCED CONCRETE SLAB ROOF FROM THE SOUTHERN EDGE, VIEW ...

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

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

  5. 12. REINFORCED CONCRETE SLAB ROOF FROM NORTHEASTERN EDGE, VIEW TOWARDS ...

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

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

  6. 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

  7. 13. REINFORCED CONCRETE SLAB ROOF FROM SOUTHWESTERN EDGE, VIEW TOWARDS ...

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

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

  8. 13. REINFORCED CONCRETE SLAB ROOF FROM THE NORTHERN EDGE, VIEW ...

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

    13. REINFORCED CONCRETE SLAB ROOF FROM THE NORTHERN EDGE, 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

  9. 9. REINFORCED CONCRETE SLAB ROOF FROM NORTHEAST EDGE, VIEW TOWARDS ...

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

    9. REINFORCED CONCRETE SLAB ROOF FROM NORTHEAST EDGE, VIEW TOWARDS SOUTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-4, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  10. 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

  11. 10. REINFORCED CONCRETE SLAB ROOF FROM SOUTHEAST EDGE, VIEW TOWARDS ...

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

    10. REINFORCED CONCRETE SLAB ROOF FROM SOUTHEAST EDGE, VIEW TOWARDS NORTHWEST. - Glenn L. Martin Company, Titan Missile Test Facilities, Captive Test Stand D-4, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO

  12. 12. REINFORCED CONCRETE SLAB ROOF FROM THE NORTHERN EDGE, VIEW ...

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

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

  13. 8. REINFORCED CONCRETE SLAB ROOF FROM NORTHWEST EDGE, ACCESS RAMP ...

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

    8. REINFORCED CONCRETE SLAB ROOF FROM NORTHWEST EDGE, ACCESS RAMP IN FOREGROUND, 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

  14. 11. REINFORCED CONCRETE SLAB ROOF, GUARD RAIL AT CENTER, VIEW ...

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

    11. REINFORCED CONCRETE SLAB ROOF, GUARD RAIL AT CENTER, 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

  15. 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

  16. INTERIOR VIEW, LOOKING NORTHEAST, WITH OVENS AND STEEL SLAB EXITING ...

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

    INTERIOR VIEW, LOOKING NORTHEAST, WITH OVENS AND STEEL SLAB EXITING (LEFT) AND EDGING MACHINE/PRESS (RIGHT). - Central Iron Foundry, Hot Strip Mill Building, 1700 Holt Road, Holt, Tuscaloosa County, AL

  17. INTERIOR VIEW, LOOKING NORTHEAST, WITH OVENS AND STEEL SLAB HAVING ...

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

    INTERIOR VIEW, LOOKING NORTHEAST, WITH OVENS AND STEEL SLAB HAVING EXITED (LEFT) AND PROCEEDING TO EDGER (RIGHT). - Central Iron Foundry, Hot Strip Mill Building, 1700 Holt Road, Holt, Tuscaloosa County, AL

  18. INTERIOR VIEW, LOOKING NORTHEAST, WITH OVENS (LEFT) AND SLAB BEING ...

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

    INTERIOR VIEW, LOOKING NORTHEAST, WITH OVENS (LEFT) AND SLAB BEING PROCESSED THROUGH PRESS/STECKLER (RIGHT). - Central Iron Foundry, Hot Strip Mill Building, 1700 Holt Road, Holt, Tuscaloosa County, AL

  19. EXTERIOR VIEW, LOOKING NORTHEAST, WITH SLAB YARD. AT RIGHT IS ...

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

    EXTERIOR VIEW, LOOKING NORTHEAST, WITH SLAB YARD. AT RIGHT IS HOT STRIP MILL BUILDING AND FURNACE. VIEW AT LEFT IS TOWARD CUT TO LENGTH BUILDING. - Central Iron Foundry Site, 1700 Holt Road, Holt, Tuscaloosa County, AL

  20. Estimation of dielectric slab permittivity using a flared coaxial line

    NASA Astrophysics Data System (ADS)

    Shin, Dong H.; Eom, Hyo J.

    2003-04-01

    Estimation of dielectric slab permittivity is considered by using a flared coaxial line. A problem of reflection from a flared coaxial line that radiates into a dielectric slab with a flange is solved. A flared coaxial line is modeled with multiply stepped coaxial lines with different inner and outer conductors. A set of simultaneous equations for the modal coefficients is constituted based on the boundary conditions. Computations are performed to illustrate the reflection behavior in terms of the coaxial line geometry, frequency, and permittivity of a dielectric slab. Nomograms are developed to estimate the permittivity from the measured reflection coefficients. The utility of a flared coaxial line for the determination of slab permittivity is discussed.

  1. 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

  2. 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 G.; McKenzie, Bonnie B.; 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

  3. Carrier transport in Bi2Se3 topological insulator slab

    NASA Astrophysics Data System (ADS)

    Gupta, Gaurav; Lin, Hsin; Bansil, Arun; Jalil, Mansoor Bin Abdul; Liang, Gengchiau

    2015-11-01

    Electron transport in Bi2Se3 topological insulator slabs is investigated in the thermal activation regime (>50 K) both in the absence (ballistic) and presence of weak and strong acoustic phonon scattering using the non-equilibrium Green function approach. Resistance of the slab is simulated as a function of temperature for a range of slab thicknesses and effective doping in order to gain a handle on how various factors interact and compete to determine the overall resistance of the slab. If the Bi2Se3 slab is biased at the Dirac point, resistance is found to display an insulating trend even for strong electron-phonon coupling strength. However, when the Fermi-level lies close to the bulk conduction band (heavy electron doping), phonon scattering can dominate and result in a metallic behavior, although the insulating trend is retained in the limit of ballistic transport. Depending on values of the operating parameters, the temperature dependence of the slab is found to exhibit a remarkably complex behavior, which ranges from insulating to metallic, and includes cases where the resistance exhibits a local maximum, much like the contradictory behaviors seen experimentally in various experiments.

  4. Double seismic zone and dehydration embrittlement of the subducting slab

    NASA Astrophysics Data System (ADS)

    Yamasaki, Tadashi; Seno, Tetsuzo

    2003-04-01

    Dehydration embrittlement of metamorphosed oceanic crust and mantle in the subducting slab may be responsible for the occurrence of intermediate-depth earthquakes. We explore the possibility that this hypothesis can explain the morphology of the double seismic zones observed in northeast Japan, southwest Japan, northeast Taiwan, northern Chile, Cape Mendocino, and eastern Aleutians. We calculate transient temperature structures of slabs based on geologically estimated subduction histories of these regions. We then determine dehydration loci of metamorphosed oceanic crust and serpentinized mantle using experimentally derived phase diagrams. The depth range of the dehydration loci of metamorphosed oceanic crust and serpentine is dependent on slab age. The dehydration loci of serpentine produce a double-layered structure. Because the upper dehydration loci of serpentine are mostly located in the wedge mantle above the slab, we regard the upper plane seismicity representing dehydration embrittlement in the oceanic crust, and we fix the slab geometry so that the upper plane seismicity is just below the upper surface of the slab. We find that the lower plane seismicity is located at the lower dehydration loci of serpentine, which indicates that the morphology of the double seismic zones is consistent with the dehydration embrittlement.

  5. Prediction of Inhomogeneous Distribution of Microalloy Precipitates in Continuous-Cast High-Strength, Low-Alloy Steel Slab

    NASA Astrophysics Data System (ADS)

    Roy, Suparna; Patra, Sudipta; Neogy, S.; Laik, A.; Choudhary, S. K.; Chakrabarti, Debalay

    2012-06-01

    Spatial distribution in size and frequency of microalloy precipitates have been characterized in two continuous-cast high-strength, low-alloy steel slabs, one containing Nb, Ti, and V and the other containing only Ti. Microsegregation during casting resulted in an inhomogeneous distribution of Nb and Ti precipitates in as-cast slabs. A model has been proposed in this study based on the detailed characterization of cast microalloy precipitates for predicting the spatial distribution in size and volume fraction of precipitates. The present model considers different models, which have been proposed earlier. Microsegregation during solidification has been predicted from the model proposed by Clyne and Kurz. Homogenization of alloying elements during cooling of the cast slab has been predicted following the approach suggested by Kurz and Fisher. Thermo-Calc software predicted the thermodynamic stability and volume fraction of microalloy precipitates at interdendritic and dendritic regions. Finally, classical nucleation and growth theory of precipitation have been used to predict the size distribution of microalloy precipitates at the aforementioned regions. The accurate prediction and control over the precipitate size and fractions may help in avoiding the hot-cracking problem during casting and selecting the processing parameters for reheating and rolling of the slabs.

  6. Elasticity and rheology of phase D and implications for seismic anisotropy in deep subducted slabs

    NASA Astrophysics Data System (ADS)

    Rosa, A. D.; Sanchez-Valle, C.; Ghosh, S.; Merkel, S.

    2011-12-01

    Dense hydrous magnesium silicate (DHMS) Phase D, MgSi2H2O6 (10-18 wt% H2O), may be the most important water carrier along cold slab geotherms and thus may play a critical role in the recycling of water into the deep mantle. Recent petrological studies have shown that Fe and Al substitutions extends the stability field of phase D toward higher slab temperatures [Ghosh, unpublished], and that phase D can account for more than 40 vol% in very hydrous peridotites between 700 and 1300 km depth [Iwamori 2004]. The stability and large volume fractions of phase D in subducted slabs, together with the highly anisotropic behavior under compression [Hushur et al. 2011] and ability to align in non-hydrostatic stress fields due to its layered structure [Rosa et al. 2010] suggest that phase D may strongly influence the seismic properties of down going slabs [Chen and Brudzinki, 2003; Laurence and Wysession, 2006]. In this contribution we combine elasticity measurements and plastic deformation experiments to evaluate the contribution of phase D to the seismic anisotropy and velocity anomalies of hydrous subducted slabs at lower mantle pressures. The elastic properties were determined by Brillouin scattering spectroscopy on Mg-bearing and Al-Fe-bearing Phase D single-crystals, synthesized at 24 GPa and 1200 °C in a multianvil apparatus at ETH Zurich. The results resolve discrepancies between previous experimental and computational studies [Liu et al 2004; Mainprice at al. 2007] and assess the effect of compositional variations on the seismic velocities of phase D. The end-member Mg-Phase D displays higher acoustic velocities than the Al-Fe-bearing Phase D. Synchrotron X-ray radial diffraction experiments were also performed to investigate the rheological properties (texturing and preferred orientations) of Mg-bearing, Fe-bearing and Al-Fe-bearing samples at pressures up to 45 GPa. Experiments were conducted in panoramic diamond anvil cells at the ESRF ID09 beamline. The uniaxial

  7. Production excimer drilling process for producing micron exit holes in polyimide

    NASA Astrophysics Data System (ADS)

    Lizotte, Todd; Ohar, Orest

    2006-02-01

    Producing micron level exit holes or vias interconnects for applications involving critical drug delivery and microelectronic packaging is no easy task. The design of excimer beam delivery optics, the physical system configuration, construction materials used and laser material interaction play significant roles in the ultimate process results. As a result of higher density microelectronic package designs and the critical nature of drug delivery, these processes need to be robust and repeatable to a 3σ level. Many companies who look to source new laser systems to meet these new demands come face to face with the reality of this dilemma. Matching laser process to material selection sets the stage for a successful integration, of most concern is the materials ability to resolve the features desired and the ease of cleaning the debris once the features are formed. This paper will present application specific laser beam delivery methods, focus/image stability techniques, beam shaping and inline inspection technology to stabilize such processes and present statistical and quality data on a process that was developed to form (1) one micron exit holes through 25 micron thick polyimide for a critical drug delivery application. The data will cover a 31 day period of processing.

  8. 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

  9. 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.

  10. Extinction and scattering by several types of silicate sphere of radius 0.05-1.0 micron, for the wavelength range 0.21-50 microns.

    NASA Technical Reports Server (NTRS)

    Bromage, G. E.; Nandy, K.; Khare, B. N.

    1973-01-01

    The exact calculation of scattering and absorption by various sub-micron sized silicate spheres is presented here, using accurately determined optical constants in the wavelength range from 50 to 0.21 microns. The extinction features near 10 and 20 microns for various samples are discussed. It is found that the ratio of peak extinction at 20 microns to that at 10 microns is constant for small particles up to 0.4-micron radius, but is less for particles of 1-micron radius. The ratio of maximum extinction in the ultraviolet to that at 10 microns decreases with increasing particle size.

  11. 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

  12. Aegean tectonics: Strain localisation, slab tearing and trench retreat

    NASA Astrophysics Data System (ADS)

    Jolivet, Laurent; Faccenna, Claudio; Huet, Benjamin; Labrousse, Loïc; Le Pourhiet, Laetitia; Lacombe, Olivier; Lecomte, Emmanuel; Burov, Evguenii; Denèle, Yoann; Brun, Jean-Pierre; Philippon, Mélody; Paul, Anne; Salaün, Gwenaëlle; Karabulut, Hayrullah; Piromallo, Claudia; Monié, Patrick; Gueydan, Frédéric; Okay, Aral I.; Oberhänsli, Roland; Pourteau, Amaury; Augier, Romain; Gadenne, Leslie; Driussi, Olivier

    2013-06-01

    We review the geodynamic evolution of the Aegean-Anatolia region and discuss strain localisation there over geological times. From Late Eocene to Present, crustal deformation in the Aegean backarc has localised progressively during slab retreat. Extension started with the formation of the Rhodope Metamorphic Core Complex (Eocene) and migrated to the Cyclades and the northern Menderes Massif (Oligocene and Miocene), accommodated by crustal-scale detachments and a first series of core complexes (MCCs). Extension then localised in Western Turkey, the Corinth Rift and the external Hellenic arc after Messinian times, while the North Anatolian Fault penetrated the Aegean Sea. Through time the direction and style of extension have not changed significantly except in terms of localisation. The contributions of progressive slab retreat and tearing, basal drag, extrusion tectonics and tectonic inheritance are discussed and we favour a model (1) where slab retreat is the main driving engine, (2) successive slab tearing episodes are the main causes of this stepwise strain localisation and (3) the inherited heterogeneity of the crust is a major factor for localising detachments. The continental crust has an inherited strong heterogeneity and crustal-scale contacts such as major thrust planes act as weak zones or as zones of contrast of resistance and viscosity that can localise later deformation. The dynamics of slabs at depth and the asthenospheric flow due to slab retreat also have influence strain localisation in the upper plate. Successive slab ruptures from the Middle Miocene to the Late Miocene have isolated a narrow strip of lithosphere, still attached to the African lithosphere below Crete. The formation of the North Anatolian Fault is partly a consequence of this evolution. The extrusion of Anatolia and the Aegean extension are partly driven from below (asthenospheric flow) and from above (extrusion of a lid of rigid crust).

  13. 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.

  14. 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. PMID:25767101

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    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.

  16. 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

  17. A high resolution atlas of the galactic plane at 12 microns and 25 microns

    NASA Technical Reports Server (NTRS)

    Price, Stephan D.; Korte, Rose M.; Sample, Rebecca S.; Kennealy, John P.; Gonsalves, Robert A.

    1994-01-01

    High resolution images of the 12 micron and 25 micron IRAS survey data from each HCON crossing the Galactic Plane are being created for those regions that the original IRAS processing labeled as confused. This encompasses the area within 100 deg longitude of the Galactic Center and within 3 deg to 10 deg of the Plane. The procedures used to create the images preserve the spatial resolution inherent in the IRAS instrument. The images are separated into diffuse and point source components and candidate sources are extracted from the point source image after non-linear spatial sharpening. Fluxes are estimated by convolving the candidate sources with the point response function and cross-correlating with the original point source image. A source is considered real if it is seen on at least two HCON's with a rather generous flux match but a stringent position criterion. A number of fields spanning a range of source densities from low to high have been examined. Initial analysis indicates that the imaging and extraction works quite well up to a source density of about 100 sources per square degree or down to roughly 0.8 Janskys.

  18. Substitution of Micron by Nanometer Scale Powders in Magnetorheological Fluids

    NASA Astrophysics Data System (ADS)

    Chaudhuri, A.; Wang, G.; Wereley, N. M.; Tasovksi, Vasil; Radhakrishnan, R.

    The effects of substitution of micron size powder by nanometer size powder in magnetorheological (MR) fluids are investigated in this study. Three MR fluid samples containing iron powder with 45% weight fraction in a carrier fluid were made by Materials Modification Inc. The difference among these three fluids is size of the magnetic particles. The first MR fluid sample contained only micron size iron powder with 10μm particle size. In the second sample, 5% micron iron was substituted with nano powders having 30~40nm mean diameter, while the third sample had 37.5% micron powder and 7.5% nano powder. Rheological tests were conducted on the three samples using a parallel disk rheometer. Highest yield stress was observed in the second MR fluid sample containing 40% micron and 5% nano iron powder. By replacing only 5% micron iron powder with nanoparticles, we achieved substantial increment in yield stress. However, when nano powder content is increased to 7.5%, the yield stress decreases and is lower than that in the all micron MR fluid. Thus, by doping a reasonable percent of nano iron powder in the MR fluid, a substantial change in the rheological characteristics is obtainable. Further investigations of effects of nano iron powder in MR fluids for higher weight fraction MR fluids will be carried out in future.

  19. 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.

  20. 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

  1. Slab laser development at MSNW - The Gemini and Centurion systems

    NASA Astrophysics Data System (ADS)

    Eggleston, J. M.; Albrecht, G. F.

    Two, zig-zag-optical-path, slab-geometry, solid-state lasers, referred to as Gemini and Centurion, are described. The Nd:glass laser (Gemini) uses a pump geometry in which the flash lamps are located between two slabs in the same laser head. The dimensions and functions of the glass slabs are studied and the single-sided pumping of the Nd:glass laser is examined. The system is verified using the Nd:YAG laser system (Centurion). The Centurion system uses four flash lamps to pump a single 6 mm x 2 cm x 15.5 cm Nd:YAG slab; the reflector structure of the system is analyzed. The thermal-optical model for the Nd:glass laser and the Trace 3D, a three-dimensional flashlamp-slab coupling code, are evaluated. The oscillation performance and defocusing of a single-pass beam are measured; it is observed that the single-sided pump output is 30 percent more efficient than the standard configuration and no major defocusing effect is detected. The use of the Trace 3D code to design a reflector system for Gemini is discussed.

  2. The effect of metastable pyroxene on the slab dynamics

    NASA Astrophysics Data System (ADS)

    Agrusta, R.; Van Hunen, J.; Goes, S. D. B.

    2014-12-01

    Global seismic studies show variations near the base of mantle transition zone, where some slabs penetrate straight into the lower mantle, whereas others seem to flatten. The dynamics of cold subducting slabs are mainly controlled by negative thermal buoyancy forces and by buoyancy anomalies due to density contrasts of the different mineralogical phases. Recent experiments show that pyroxene dissolves into the denser garnet, forming the majorite-garnet, at very slow rates, and pyroxene can remain metastable to temperatures as high as 1400 °C.Because metastable pyroxene may potentially persist in subduction zones over large volumes and to great depths, a self-consistent subduction model has been used to investigate the influence of metastable phase on the dynamics of subducting oceanic lithosphere. The phase boundary of pyroxene to garnet (300 km equilibrium depth) is considered together with the phase transition of olivine to wadsleyite (410 km equilibrium), and ringwoodite to perovskite-magnesiowustite (670 km equilibrium). The kinetics of the phase transition for ol-wd and in px-gt are treated considering a temperature-dependent diffusion rate. To quantify the buoyant contributions of the metastable phase on the subduction dynamics, an extensive parameter sensitivity study has been performed.Results from this study illustrate that metastable pyroxene affects slab buoyancy at least as much as olivine metastability. Slab age and phase change kinetics are the most dominant parameters, and buoyancy effects are stronger for old subducting lithosphere and for low diffusion rates, favouring slab stagnation in the transition zone.

  3. 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

  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. 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.

  6. On the possible bipolar nature of 21 micron IRAS sources

    NASA Technical Reports Server (NTRS)

    Hrivnak, Bruce J.; Kwok, S.

    1991-01-01

    The discovery of another IRAS source (22574 + 6609) showing the unidentified 21-micron emission feature is reported. Its overall energy distribution is similar to the well-known edge-on bipolar nebulae AFGL 2688 and AFGL 618. Ground-based optical and infrared observations of this object and two other 21-micron sources show that while all three have very similar infrared properties, they differ greatly in the visual region. All three of these 21-micron sources are intrinsically similar bipolar nebulae, viewed at different orientations.

  7. The Tonga-Vanuatu Subduction Complex -- a Self-Optimized 3D Slab-Slab-Mantle Heat Pump

    NASA Astrophysics Data System (ADS)

    McCreary, J. A.

    2008-12-01

    Recently published geophysical and geochemical data and increasingly actualistic free subduction models prompted a fresh look at 2 classics hinting, in combination, that a coupled 3D slab-slab-upper mantle interaction (Scholz and Campos, 1995; full citations at URL below) might power the prodigious surface heat dissipation (Lagabrielle et al., 1997) characterizing one of Earth's most remarkable tectonomagmatic systems, the Tonga-Vanuatu Subduction Complex (TVSC). The 3D TVSC includes (1) the kinematically, magmatically, and bathymetrically distinct North Tonga (NT, 14-26° S) and South Vanuatu (SV, 16-23° S) trenches and slabs, (2) the shared NT-SV backarc, and (3) entrained mobile upper mantle (MUM). That Earth's greatest convergence, rollback, and spreading rates; most disseminated spreading (the North Fiji Basin (NFB) ridge swarm); and greatest concentration of aggregate active ridge length coincide in a 1,500 km TVSC can't be accidental. To the north and south, the respective active NT and SV trenches swing abruptly 90° counterclockwise into continuity with the Vitiaz and Hunter fossil trenches, both active in the Late Miocene but now sinistral strike-slip loci standing over long exposed PA and AU slab edges. These 2 active-fossil trench pairs bracket a hot, shallow and geophysically and geochemically exceptional TVSC interior consisting of 2 rapidly spreading backarcs set back-to-back in free sublithospheric communication: The Lau-Havre NT backarc on the east and the ridge-infested SV backarc (NFB) on the west. The NFB and adjacent North Fiji Plateau make up the unplatelike New Hebrides-Fiji Orogen (Bird, 2003). As in the western Aleutians, the NT-Vitiaz and SV-Hunter subduction-to-strike-slip transitions (SSSTs) stand above toroidal fluxes of hot, dry PA and AU MUM driven along-trench and around the free NT and SV slab edges from subslab to supraslab regions by dynamic pressure gradients powered by slab free-fall and induced viscous couplings. These edge

  8. Search for deep slabs in the Northwest Pacific mantle.

    PubMed

    Zhou, H W; Anderson, D L

    1989-11-01

    A residual sphere is formed by projecting seismic ray travel-time anomalies, relative to a reference Earth model, onto an imaginary sphere around an earthquake. Any dominant slab-like fast band can be determined with spherical harmonic expansion. The technique is useful in detecting trends associated with high-velocity slabs beneath deep earthquakes after deep-mantle and near-receiver effects are removed. Two types of corrections are used. The first uses a tomographic global mantle model; the second uses teleseismic station averages of residuals from many events over a large area centered on the events of interest. Under the Mariana, Izu-Bonin, and Japan trenches, the dominant fast bands are generally consistent with seismicity trends. The results are unstable and differ from the seismicity trend for Kurile events. The predominant fast band for most deep earthquakes under Japan is subhorizontal rather than near vertical. We find little support for the deep slab penetration hypothesis. PMID:16594080

  9. 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

  10. Controlling of optical bistability and multistability in a defect slab

    NASA Astrophysics Data System (ADS)

    Jabbari, Masoud

    2016-02-01

    Optical bistability (OB) and optical multistability (OM) due to wide applications in all-optical switching and transistors is studied in this paper. Here, we study the OB and OM properties of incident light in a defect slab doped by a GaAs quantum well (QW) nanostructure. It is shown that OB and OM features can be manipulated by spin coherence created by circular polarized laser fields in GaAs QWs. The impacts of laser field features, such as intensity, frequency detuning, and relative phase, on OB and OM are simulated. Moreover, the dependence of OB and OM features of a probe light on the thickness of the slab, then, are analyzed. It is found that the thickness of the slab can provide a new way to optimize the intensity threshold of OB and OM. We hope that our proposed model may be useful for developing all-optical devices on nanoscales.

  11. 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

  12. 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

  13. 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.

  14. Stress Distribution in the Subducted Slab in the Transition Zone

    NASA Astrophysics Data System (ADS)

    Běhounková, M.; Běhounková, M.; Čížková, H.; Matyska, C.; Špičák, A.

    2006-12-01

    We present the results of numerical modelling of subduction process in a 2-D cartesian box. Our numerical code is based on the method of Gerya and Yuen 2003. We concentrate on the deformation and stress distribution within the slab in the transition zone. Our composite rheological model includes diffusion creep, dislocation creep and power-law stress limiter. The effects of phase transitions at the depths 410 km and 660 km are taken into account. The model is applied to the Tonga subduction region, where the currently subducting plate might face the remnants of the high viscosity subducted material in the transition zone. This material might possibly originate either from a previous episode of the subduction (Chen and Brudzinski, 2001) or from the buoyant detached slab broken off from the active subducting slab (Green, 2001). We prescribe the cold and relatively high viscosity piece of old slab lying above the 660 km interface. The stress distribution in the new subducting place is then investigated as the plate approaches these remnants of old slab. Stress directions and amplitudes are compared to the data available from the analyses of the earthquake mechanisms in Tonga region. Chen W.-P., Brudzinski R, 2001. Evidence for a Large-Scale Remnant of Subducted Lithosphere Beneath Fiji, Science 292, 2475--2479. Gerya T.V., Yuen D.A., 2003. Characteristics-based marker-in-cell method with conservative finite-differences schemes for modelling geological flows with strongly variable transport properties, Phys. Earth Planet. Int. 140, 293--318. Green, H.W., 2001. A graveyard for buoyant slabs?, Science 292, 2445-2446.

  15. 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 ...

  16. 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%.

  17. 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.

  18. Improved Fabrication of Lithium Films Having Micron Features

    NASA Technical Reports Server (NTRS)

    Whitacre, Jay

    2006-01-01

    An improved method has been devised for fabricating micron-dimension Li features. This approach is intended for application in the fabrication of lithium-based microelectrochemical devices -- particularly solid-state thin-film lithium microbatteries.

  19. 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.

  20. 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.

  1. 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

  2. Subduction and slab detachment in the Mediterranean-Carpathian region.

    PubMed

    Wortel, M J; Spakman, W

    2000-12-01

    Seismic tomography models of the three-dimensional upper mantle velocity structure of the Mediterranean-Carpathian region provide a better understanding of the lithospheric processes governing its geodynamical evolution. Slab detachment, in particular lateral migration of this process along the plate boundary, is a key element in the lithospheric dynamics of the region during the last 20 to 30 million years. It strongly affects arc and trench migration, and causes along-strike variations in vertical motions, stress fields, and magmatism. In a terminal-stage subduction zone, involving collision and suturing, slab detachment is the natural last stage in the gravitational settling of subducted lithosphere. PMID:11110653

  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. Diffractive properties of imaginary-part photonic crystal slab

    PubMed Central

    2012-01-01

    The diffraction spectra of imaginary-part photonic crystal (IPPC) slabs are analyzed using the scattering-matrix method. By investigating the thickness dependence of the diffraction, we find a remarkable red shift of central wavelength of the diffraction spectrum, which obviously distinguishes from the phenomenon of spectral hole. We observe that diffraction efficiency can be enhanced more than 20-fold by optimizing the geometry parameters. These imply that the diffraction spectra of the IPPC slab can be controlled at will and used to guide the design to achieve useful nanoscale devices. PMID:22720871

  6. 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.

  7. Optical modes in slab waveguides with magnetoelectric effect

    NASA Astrophysics Data System (ADS)

    Talebi, Nahid

    2016-05-01

    Optical modes in anisotropic slab waveguides with topological and chiral magnetoelectric effects are investigated analytically, by deriving the closed-form characteristic equations of the modes and hence computing the dispersion-diagrams. In order to compute the characteristic equations, a vector-potential approach is introduced by incorporating a generalized Lorentz gauge, and the Helmholtz equations are derived correspondingly. It will be shown that the formation of the complex modes and hybridization of the optical modes in such slab waveguides is inevitable. Moreover, when the tensorial form of the permittivity in the waveguide allows for a hyperbolic dispersion, complex transition from the photonic kinds of modes to the plasmonic modes is expected.

  8. Novel power switch using oblique incidence to a nonlinear slab

    NASA Astrophysics Data System (ADS)

    Liu, Hwei-Yuan; Wang, Way-Seen

    1995-05-01

    A simple 1 x n optical power switch employing oblique incidence to a nonlinear slab was recommended. When the input power was within the range of interest, the number n can be augmented by increasing the slab thickness, although the optimum input powers must be recomputed. This rendered the proposed switch extremely flexible and was potentially applicable to all-optical signal processing. In addition, it was determined that the nonlinear dispersion relation was usually applied for the analysis of the wave-guide modes in a specific nonlinear wave guide. However, it was not very precise in the analysis of soliton switching unless the effective index was substituted by an average one.

  9. Seismic Behaviour of Masonry Vault-Slab Structures

    NASA Astrophysics Data System (ADS)

    Chesi, Claudio; Butti, Ferdinando; Ferrari, Marco

    2008-07-01

    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.

  10. 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.