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Sample records for spun form domes

  1. Mitigating Abnormal Grain Growth for Friction Stir Welded Al-Li 2195 Spun Formed Domes

    NASA Technical Reports Server (NTRS)

    Chen, Po-Shou; Russell, Carolyn

    2012-01-01

    Formability and abnormal grain growth (AGG) are the two major issues that have been encountered for Al alloy spun formed dome development using friction stir welded blanks. Material properties that have significant influence on the formability include forming range and strain hardening exponent. In this study, tensile tests were performed for two 2195 friction stir weld parameter sets at 400 F to study the effects of post weld anneal on the forming range and strain hardening exponent. It was found that the formability can be enhanced by applying a newly developed post weld anneal to heat treat the friction stir welded panels. This new post weld anneal leads to a higher forming range and much improved strain hardening exponent. AGG in the weld nugget is known to cause a significant reduction of ductility and fracture toughness. This study also investigated how AGG may be influenced by the heating rate to the solution heat treatment temperature. After post-weld annealing, friction stir welds were strained to 15% and 39% by compression at 400 F before they were subjected to SHT at 950 F for 1 hour. Salt bath SHT is very effective in reducing the grain size as it helps arrest the onset of AGG and promote normal recrystallization and grain growth. However, heat treating a 18 ft dome using a salt bath is not practical. Efforts are continuing at Marshall Space Flight Center to identify the welding parameters and heat treating parameters that can help mitigate the AGG in the friction stir welds.

  2. Simulated Service and Stress Corrosion Cracking Testing for Friction Stir Welded Spun Formed Domes

    NASA Technical Reports Server (NTRS)

    Stewart, Thomas J.; Torres, Pablo D.; Caratus, Andrei A.; Curreri, Peter A.

    2010-01-01

    Simulated service testing (SST) development was required to help qualify a new 2195 aluminum lithium (Al-Li) alloy spin forming dome fabrication process for the National Aeronautics and Space Administration (NASA) Exploration Development Technology Program. The application for the technology is to produce high strength low weight tank components for NASA s next generation launch vehicles. Since plate material is not currently manufactured large enough to fabricate these domes, two plates are joined by means of friction stir welding. The plates are then pre-contour machined to near final thicknesses allowing for a thicker weld land and anticipating the level of stretch induced by the spin forming process. The welded plates are then placed in a spin forming tool and hot stretched using a trace method producing incremental contours. Finally the dome receives a room temperature contour stretch to final dimensions, heat treatment, quenching, and artificial aging to emulate a T-8 condition of temper. Stress corrosion cracking (SCC) tests were also performed by alternate immersion in a sodium chloride (NaCl) solution using the typical double beam assembly and with 4-point loaded specimens and use of bent-beam stress-corrosion test specimens under alternate immersion conditions. In addition, experiments were conducted to determine the threshold stress intensity factor for SCC (K(sub ISCC)) which to our knowledge has not been determined previously for Al-Li 2195 alloy. The successful simulated service and stress corrosion testing helped to provide confidence to continue to Ares 1 scale dome fabrication

  3. Simulated Service and Stress Corrosion Cracking Testing for Friction Stir Welded Spun Form Domes

    NASA Technical Reports Server (NTRS)

    Stewart, Thomas J.; Torres, Pablo D.; Caratus, Andrei A.; Curreri, Peter A.

    2010-01-01

    Damage tolerance testing development was required to help qualify a new spin forming dome fabrication process for the Ares 1 program at Marshall Space Flight Center (MSFC). One challenge of the testing was due to the compound curvature of the dome. The testing was developed on a sub-scale dome with a diameter of approximately 40 inches. The simulated service testing performed was based on the EQTP1102 Rev L 2195 Aluminum Lot Acceptance Simulated Service Test and Analysis Procedure generated by Lockheed Martin for the Space Shuttle External Fuel Tank. This testing is performed on a specimen with an induced flaw of elliptical shape generated by Electrical Discharge Machining (EDM) and subsequent fatigue cycling for crack propagation to a predetermined length and depth. The specimen is then loaded in tension at a constant rate of displacement at room temperature until fracture occurs while recording load and strain. An identical specimen with a similar flaw is then proof tested at room temperature to imminent failure based on the critical offset strain achieved by the previous fracture test. If the specimen survives the proof, it is then subjected to cryogenic cycling with loads that are a percentage of the proof load performed at room temperature. If all cryogenic cycles are successful, the specimen is loaded in tension to failure at the end of the test. This standard was generated for flat plate, so a method of translating this to a specimen of compound curvature was required. This was accomplished by fabricating a fixture that maintained the curvature of the specimen rigidly with the exception of approximately one-half inch in the center of the specimen containing the induced flaw. This in conjunction with placing the center of the specimen in the center of the load train allowed for successful testing with a minimal amount of bending introduced into the system. Stress corrosion cracking (SCC) tests were performed using the typical double beam assembly and with 4

  4. Spun Almost Normal Form

    NASA Astrophysics Data System (ADS)

    Paullin, Katherine L.

    Many of a 3-manifold's properties are determined by the surfaces they contain, and this knowledge leads to the foundation of decision algorithms for 3- manifolds. Popular work influencing the work of 3-manifold algorithms has it's roots in normal surface theory. In a triangulated 3-manifold, Haken and Kneser showed that we could put any incompressible surface into normal form. Expanding on those techniques, Rubinstein and Stocking later showed we could put any strongly irreducible surface into almost normal form. Walsh has more recently shown that in an ideal triangulation of a hyperbolic manifold many surfaces can be spun normalized. One unsolved problem in 3-manifold algorithms is studying the complexity of Lens Space Recognition. Spun almost normalization appears to be a part of solving this larger problem. In this dissertation, I will first discuss a nontraditional technique using graphs of equivalence classes of compressing disks that allows us to take a combinatorial approach to generalize the result of Walsh's to nonhyperbolic manifolds. Using that method, I'll also explore the conditions needed to show that a surface can be spun almost normalized.

  5. Large Spun Formed Friction-Stir Welded Tank Domes for Liquid Propellant Tanks Made from AA2195: A Technology Demonstration for the Next Generation of Heavy Lift Launchers

    NASA Technical Reports Server (NTRS)

    Stachulla, M.; Pernpeinter, R.; Brewster J.; Curreri, P.; Hoffman, E.

    2010-01-01

    Improving structural efficiency while reducing manufacturing costs are key objectives when making future heavy-lift launchers more performing and cost efficient. The main enabling technologies are the application of advanced high performance materials as well as cost effective manufacture processes. This paper presents the status and main results of a joint industrial research & development effort to demonstrate TRL 6 of a novel manufacturing process for large liquid propellant tanks for launcher applications. Using high strength aluminium-lithium alloy combined with the spin forming manufacturing technique, this development aims at thinner wall thickness and weight savings up to 25% as well as a significant reduction in manufacturing effort. In this program, the concave spin forming process is used to manufacture tank domes from a single flat plate. Applied to aluminium alloy, this process allows reaching the highest possible material strength status T8, eliminating numerous welding steps which are typically necessary to assemble tank domes from 3D-curved panels. To minimize raw material costs for large diameter tank domes for launchers, the dome blank has been composed from standard plates welded together prior to spin forming by friction stir welding. After welding, the dome blank is contoured in order to meet the required wall thickness distribution. For achieving a material state of T8, also in the welding seams, the applied spin forming process allows the required cold stretching of the 3D-curved dome, with a subsequent ageing in a furnace. This combined manufacturing process has been demonstrated up to TRL 6 for tank domes with a 5.4 m diameter. In this paper, the manufacturing process as well as test results are presented. Plans are shown how this process could be applied to future heavy-lift launch vehicles developments, also for larger dome diameters.

  6. Dome forming eruptions: a global hazards database

    NASA Astrophysics Data System (ADS)

    Ogburn, S. E.; Loughlin, S.; Calder, E. S.; Ortiz, N.

    2009-12-01

    The analysis of global datasets of historical eruptions is a powerful tool for decision-making as well as for scientific discovery. Lava dome forming eruptions are common throughout the world, can extend for significant periods of time and have many associated hazards, thus providing a rich source of data to mine. A database on dome forming eruptions is under development with the view to aiding comparative studies, providing scientists with valuable data for analysis, and enabling advances in modeling of associated hazards. For new eruptive episodes in particular, and in the absence of monitoring data or a knowledge of a volcano’s eruptive history, global analysis can provide a method of understanding what might be expected based on similar eruptions in the past. Important scientific information has already been gleaned from disparate collections of dome-forming eruption hazard information, such as variation in the mobility of different types of pyroclastic flows, magma ascent and extrusion dynamics, and mechanisms of lava dome collapse. Further, modeling (both empirically-based and geophysically-based) of volcanic phenomena requires extensive data for development, calibration and validation. This study investigates the relationship between large explosive eruptions (VEI ≥ 4) and lava dome-growth from 1000 CE to present by development of a world-wide database of all relevant information, including dome growth duration, pauses between episodes of dome growth, and extrusion rates. Data sources include the database of volcanic activity maintained by the Smithsonian Institute (Global Volcanism Program) and all relevant published review papers, research papers and reports. For example, nearly all dome-forming eruptions have been associated with some level of explosive activity. Most explosions are vulcanian with eruption plumes reaching less than 15 km, and with a Volcanic Explosivity Index (VEI) <3. However large Plinian explosions with a VEI ≥ 4 can also occur

  7. DomeHaz, a Global Hazards Database: Understanding Cyclic Dome-forming Eruptions, Contributions to Hazard Assessments, and Potential for Future Use and Integration with Existing Cyberinfrastructure

    NASA Astrophysics Data System (ADS)

    Ogburn, S. E.; Calder, E.; Loughlin, S.

    2013-12-01

    Dome-forming eruptions can extend for significant periods of time and can be dangerous; nearly all dome-forming eruptions have been associated with some level of explosive activity. Large Plinian explosions with a VEI ≥ 4 sometimes occur in association with dome-forming eruptions. Many of the most significant volcanic events of recent history are in this category. The 1902-1905 eruption of Mt. Pelée, Martinique; the 1980-1986 eruption of Mount St. Helens, USA; and the 1991 eruption of Mt. Pinatubo, Philippines all demonstrate the destructive power of VEI ≥ 4 dome-forming eruptions. Global historical analysis is a powerful tool for decision-making as well as for scientific discovery. In the absence of monitoring data or a knowledge of a volcano's eruptive history, global analysis can provide a method of understanding what might be expected based on similar eruptions. This study investigates the relationship between large explosive eruptions and lava dome growth and develops DomeHaz, a global database of dome-forming eruptions from 1000 AD to present. It is currently hosted on VHub (https://vhub.org/groups/domedatabase/), a community cyberinfrastructure for sharing data, collaborating, and modeling. DomeHaz contains information about 367 dome-forming episodes, including duration of dome growth, duration of pauses in extrusion, extrusion rates, and the timing and magnitude of associated explosions. Data sources include the The Smithsonian Institution Global Volcanism Program (GVP), Bulletin of the Global Volcanism Network, and all relevant published review papers, research papers, and reports. This database builds upon previous work (e.g Newhall and Melson, 1983) in light of newly available data for lava dome eruptions. There have been 46 new dome-forming eruptions, 13 eruptions that continued past 1982, 151 new dome-growth episodes, and 8 VEI ≥ 4 events since Newhall and Melson's work in 1983. Analysis using DomeHaz provides useful information regarding the

  8. Hot vacuum creep forming of scale shuttle external tank dome caps

    NASA Technical Reports Server (NTRS)

    Thomas, A. O.

    1974-01-01

    The feasibility of forming shuttle external tank dome caps by hot vacuum creep was investigated for a sub-scale configuration. Aluminum 2219-T37 at an elevated temperature equivalent to the artificial aging time and temperature was used to produce the T87 condition while achieving MIL-HBK -5 properties of 2219-T87 aluminum alloy material. A feasibility analysis was conducted in two phases: the design and build of a sub-scale hot vacuum creep forming (HVCF) die and the forming evaluation of various cap configurations. The contour was constant in all evaluations. This configuration was found to be too severe for the limited forming force available by HVCF.

  9. Friction-Stir-Welded and Spin-Formed End Domes for Cryogenic Tanks

    NASA Technical Reports Server (NTRS)

    Hales, S. J.; Tayon, W. A.; Domack, M. S.

    2012-01-01

    Manufacturing of single-piece end domes for cryogenic tanks employing spin forming of tailored, friction-stir-welded blanks of Al-Li alloy 2195 plate offers cost and reliability benefits. The introduction of plastic deformation into a friction stir weld is a unique feature of the proposed manufacturing route. This investigation addressed abnormal grain growth [AGG] within the friction stir weldments during postfabrication processing of a prototype dome. The phenomenon of AGG was observed during the solution heat treatment [SHT] phase of T8 tempering and is a major concern for meeting specifications. Such abrupt microstructural transitions can be detrimental to notch-sensitive mechanical properties, such as ductility and/or fracture toughness. If the issue of AGG cannot be resolved, then the acceptance of this approach as a viable manufacturing route may be in jeopardy. The innovative approach adopted in this investigation was the insertion of a stand-alone, Intermediate Annealing Treatment [IAT] between the spin forming and T8 processing operations. A simple, recovery annealing step was deemed to be the most readily-scalable solution when fabricating thin-walled, ellipsoidal domes. The research effort culminated in the development of an effective IAT, which resulted in a significant decrease in AGG following SHT. The processing philosophy adopted in designing the IAT is outlined and the microstructural reasons for success are discussed. The analytical results presented are consistent with promoting continuous grain growth during the IAT, thereby suppressing AGG during the SHT.

  10. Room temperature stretch forming of scale space shuttle external tank dome gores. Volume 1: Technical

    NASA Technical Reports Server (NTRS)

    Blunck, R. D.; Krantz, D. E.

    1974-01-01

    An account of activities and data gathered in the Room Temperature Stretch Forming of One-third Scale External Tank Bulkhead Gores for space shuttle study, and a tooling design and production cost study are reported. The following study phases are described: (1) the stretch forming of three approximately one-third scale external tank dome gores from single sheets of 2219-T37 aluminum alloy; (2) the designing of a full scale production die, including a determination of tooling requirements; and (3) the determination of cost per gore at the required production rates, including manufacturing, packaging, and shipping.

  11. Net Shape Spin Formed Cryogenic Aluminum Lithium Cryogenic Tank Domes for Lower Cost Higher Performance Launch Vehicles

    NASA Technical Reports Server (NTRS)

    Curreri, Peter A.; Hoffman, Eric; Domack, Marcia; Brewster, Jeb; Russell, Carolyn

    2013-01-01

    With the goal of lower cost (simplified manufacturing and lower part count) and higher performance (higher strength to weight alloys) the NASA Technical Maturation Program in 2006 funded a proposal to investigate spin forming of space launch vehicle cryogenic tank domes. The project funding continued under the NASA Exploration Technology Development Program through completion in FY12. The first phase of the project involved spin forming of eight, 1 meter diameter "path finder" domes. Half of these were processed using a concave spin form process (MT Aerospace, Augsburg Germany) and the other half using a convex process (Spincraft, Boston MA). The convex process has been used to produce the Ares Common Bulkhead and the concave process has been used to produce dome caps for the Space Shuttle light weight external tank and domes for the NASDA H2. Aluminum Lithium material was chosen because of its higher strength to weight ratio than the Aluminum 2219 baseline. Aluminum lithium, in order to obtain the desired temper (T8), requires a cold stretch after the solution heat treatment and quench. This requirement favors the concave spin form process which was selected for scale up. This paper describes the results of processing four, 5.5 meter diameter (upper stage scale) net shaped spin formed Aluminum Lithium domes. In order to allow scalability beyond the limits of foundry and rolling mills (about 12 foot width) the circular blank contained one friction stir weld (heavy lifter scales require a flat blank containing two welds). Mechanical properties data (tensile, fracture toughness, stress corrosion, and simulated service testing) for the parent metal and weld will also be discussed.

  12. Multiple timescales of cyclical behaviour observed at two dome-forming eruptions

    NASA Astrophysics Data System (ADS)

    Lamb, Oliver D.; Varley, Nick R.; Mather, Tamsin A.; Pyle, David M.; Smith, Patrick J.; Liu, Emma J.

    2014-09-01

    Cyclic behaviour over a range of timescales is a well-documented feature of many dome-forming volcanoes, but has not previously been identified in high resolution seismic data from Volcán de Colima (Mexico). Using daily seismic count datasets from Volcán de Colima and Soufrière Hills volcano (Montserrat), this study explores parallels in the long-term behaviour of seismicity at two long-lived systems. Datasets are examined using multiple techniques, including Fast-Fourier Transform, Detrended Fluctuation Analysis and Probabilistic Distribution Analysis, and the comparison of results from two systems reveals interesting parallels in sub-surface processes operating at both systems. Patterns of seismicity at both systems reveal complex but broadly similar long-term temporal patterns with cycles on the order of ~ 50- to ~ 200-days. These patterns are consistent with previously published spectral analyses of SO2 flux time-series at Soufrière Hills volcano, and are attributed to variations in the movement of magma in each system. Detrended Fluctuation Analysis determined that both volcanic systems showed a systematic relationship between the number of seismic events and the relative ‘roughness' of the time-series, and explosions at Volcán de Colima showed a 1.5-2 year cycle; neither observation has a clear explanatory mechanism. At Volcán de Colima, analysis of repose intervals between seismic events shows long-term behaviour that responds to changes in activity at the system. Similar patterns for both volcanic systems suggest a common process or processes driving the observed signal but it is not clear from these results alone what those processes may be. Further attempts to model conduit processes at each volcano must account for the similarities and differences in activity within each system. The identification of some commonalities in the patterns of behaviour during long-lived dome-forming eruptions at andesitic volcanoes provides a motivation for

  13. Carbon nanotube fiber spun from wetted ribbon

    DOEpatents

    Zhu, Yuntian T; Arendt, Paul; Zhang, Xiefei; Li, Qingwen; Fu, Lei; Zheng, Lianxi

    2014-04-29

    A fiber of carbon nanotubes was prepared by a wet-spinning method involving drawing carbon nanotubes away from a substantially aligned, supported array of carbon nanotubes to form a ribbon, wetting the ribbon with a liquid, and spinning a fiber from the wetted ribbon. The liquid can be a polymer solution and after forming the fiber, the polymer can be cured. The resulting fiber has a higher tensile strength and higher conductivity compared to dry-spun fibers and to wet-spun fibers prepared by other methods.

  14. Muon radiography and deformation analysis of the lava dome formed by the 1944 eruption of Usu, Hokkaido--contact between high-energy physics and volcano physics--.

    PubMed

    K M Tanaka, Hiroyuki; Yokoyama, Izumi

    2008-01-01

    Lava domes are one of the conspicuous topographic features on volcanoes. The subsurface structure of the lava dome is important to discuss its formation mechanism. In the 1944 eruption of Volcano Usu, Hokkaido, a new lava dome was formed at its eastern foot. After the completion of the lava dome, various geophysical methods were applied to the dome to study its subsurface structure, but resulted in a rather ambiguous conclusion. Recently, from the results of the levelings, which were repeated during the eruption, "pseudo growth curves" of the lava dome were obtained. The curves suggest that the lava dome has a bulbous shape. In the present work, muon radiography, which previously proved effective in imaging the internal structure of Volcano Asama, has been applied to the Usu lava dome. The muon radiography measures the distribution of the "density length" of volcanic bodies when detectors are arranged properly. The result obtained is consistent with the model deduced from the pseudo growth curves. The measurement appears to afford useful method to clarify the subsurface structure of volcanoes and its temporal changes, and in its turn to discuss volcanic processes. This is a point of contact between high-energy physics and volcano physics. PMID:18941290

  15. Magma ascent dynamic through Ti diffusion in magnetites. Application to lava dome-forming eruptions. Implications to lava dome superifical explosivity.

    NASA Astrophysics Data System (ADS)

    Boudon, Georges; Balcone-Boissard, Hélène; Morgan, Dan J.

    2016-04-01

    Superficial lava dome explosivity represents a major hazard during lava dome growth. But the origin of this explosive activity remains unclear until recently. By using geochemical (residual water content, silica abundance) and textural (vesicularity, microcristallinity) data, we constrain the occurrence of such hazard to the beginning of the lava dome activity. During the first stages of growth, the lava dome is small enough to develop an impermeable carapace that isolates a less degassed batch of magma inside, thus allowing an internal overpressurization of the volcano (Boudon et al., 2015). This study more precisely details the petrology and the texture of titano-magnetites as archive of magma ascent dynamic within the conduit. Titano-magnetites may exhibit two types of textures: exsolved or "limpid". When they are exsolved, no time constrain may be extracted as they re-equilibrate. On the contrary, when they are unexsolved, major element distribution, in particular Ti, may act as a powerful tool to decipher magma dynamic (differentiation, mixing) and estimate time that corresponds to the magma ascent time. The composition and elemental diffusion profiles are acquired by EPMA, following textural investigations by SEM. The time is then obtained by modelling the profile as a diffusion profile using the intracristalline diffusion coefficients published in literature. We applied this methodology to examples of lava dome superficial explosivity on Montagne Pelée in Martinique (Lesser Antilles Arc), and on Puy Chopine volcano in La Chaine des Puys, (French Massif Central). More precisely, the first phase of the Puy Chopine lava dome growth experienced a superficial explosion, as for Montagne Pelée, the first stages of the 1902 eruption (several superficial explosions occurred) and the 650 y. BP eruption (two superficial explosions destroyed the growing lava dome). We show that, for a single event, the vesiculated, undegassed batch of magma responsible of the

  16. Dome Schools.

    ERIC Educational Resources Information Center

    Cirulli, Carol

    1999-01-01

    Back in 1988, Emmett, Idaho, built the first monolithic dome school. Now, school boards in Arizona, Missouri, Florida, Minnesota, and New Mexico are among those that have voted to build domed school buildings. A monolithic dome is a steel- reinforced, concrete structure with a smooth, round surface that is inspired by the shape of an egg. (MLF)

  17. Correlation of Fracture Behavior With Microstructure in Friction Stir Welded, and Spin Formed AI-Li 2195 Domes

    NASA Technical Reports Server (NTRS)

    Tayon, Wesley A.; Domack, Marcia S.; Hales, Stephen J.

    2012-01-01

    Single-piece, spin-formed domes manufactured from friction stir welded (FSW) plates of Al-Li alloy 2195 have the potential to reduce the cost of fabricating cryogenic propellant tanks. Mechanical properties in the completed domes can be related directly to the final material condition and the microstructures developed. However, these new fabrication techniques have resulted in unexpected material challenges, such as abnormal grain growth in the weld nugget and the propensity for fracture in the adjacent thermo-mechanically affected zone (TMAZ). In this study, the microstructure and texture transformations within the TMAZ are related to fracture location in the vicinity of the weldment. The texture variations in the TMAZ are caused primarily by the varying amounts of shear deformation introduced during the FSW process. Grain morphology and microtexture characteristics are examined as a function of location in the TMAZ via electron backscatter diffraction (EBSD). A strong correlation between fracture location and the presence of texture banding in the TMAZ is observed. The fracture path tends to follow a distinct region of low Taylor Factor (TF) grains.

  18. Robotic Manufacturing of 5.5 Meter Cryogenic Fuel Tank Dome Assemblies for the NASA Ares I Rocket

    NASA Technical Reports Server (NTRS)

    Jones, Ronald E.

    2012-01-01

    The Ares I rocket is the first launch vehicle scheduled for manufacture under the National Aeronautic and Space Administration's (NASA's) Constellation program. A series of full-scale Ares I development articles have been constructed on the Robotic Weld Tool at the NASA George C. Marshall Space Flight Center in Huntsville, Alabama. The Robotic Weld Tool is a 100 ton, 7-axis, robotic manufacturing system capable of machining and friction stir welding large-scale space hardware. This presentation will focus on the friction stir welding of 5.5m diameter cryogenic fuel tank components; specifically, the liquid hydrogen forward dome (LH2 MDA), the common bulkhead manufacturing development articles (CBMDA) and the thermal protection system demonstration dome (TPS Dome). The LH2 MDA was the first full-scale, flight-like Ares I hardware produced under the Constellation Program. It is a 5.5m diameter elliptical dome assembly consisting of eight gore panels, a y-ring stiffener and a manhole fitting. All components are made from aluminumlithium alloy 2195. Conventional and self-reacting friction stir welding was used on this article. An overview of the manufacturing processes will be discussed. The LH2 MDA is the first known fully friction stir welded dome ever produced. The completion of four Common Bulkhead Manufacturing Development Articles (CBMDA) and the TPS Dome will also be highlighted. Each CBMDA and the TPS Dome consists of a 5.5m diameter spun-formed dome friction stir welded to a y-ring stiffener. The domes and y-rings are made of aluminum 2014 and 2219 respectively. The TPS Dome has an additional aluminum alloy 2195 barrel section welded to the y-ring. Manufacturing solutions will be discussed including "fixtureless" welding with self reacting friction stir welding.

  19. Monolithic Domes.

    ERIC Educational Resources Information Center

    Lanham, Carol

    2002-01-01

    Describes how the energy savings, low cost, and near-absolute protection from tornadoes provided by monolithic domes is starting to appeal to school districts for athletic and other facilities, including the Italy (Texas) Independent School District. Provides an overview of monolithic dome construction. (EV)

  20. Effect of Chemical Treatments on Flax Fibre Reinforced Polypropylene Composites on Tensile and Dome Forming Behaviour

    PubMed Central

    Wang, Wentian; Lowe, Adrian; Kalyanasundaram, Shankar

    2015-01-01

    Tensile tests were performed on two different natural fibre composites (same constituent material, similar fibre fraction and thickness but different weave structure) to determine changes in mechanical properties caused by various aqueous chemical treatments and whether any permanent changes remain on drying. Scanning electronic microscopic examinations suggested that flax fibres and the flax/polypropylene interface were affected by the treatments resulting in tensile property variations. The ductility of natural fibre composites was improved significantly under wet condition and mechanical properties (elongation-to-failure, stiffness and strength) can almost retain back to pre-treated levels when dried from wet condition. Preheating is usually required to improve the formability of material in rapid forming, and the chemical treatments performed in this study were far more effective than preheating. The major breakthrough in improving the formability of natural fibre composites can aid in rapid forming of this class of material system. PMID:25789505

  1. The optics of ellipsoidal domes

    NASA Astrophysics Data System (ADS)

    Ellis, Kenneth Scott

    An ellipsoidal dome is a conformal optical element used to replace a hemispherical dome on a missile to enhance its performance by reducing its aerodynamic drag. Conformal optics are a general class of optical systems in which the optical elements are shaped to optimize something other than image quality, such as aerodynamics. An ellipsoidal dome has lower aerodynamic drag than a comparably sized hemispherical dome. On a missile, lower drag improves its aerodynamic performance by increasing its range and fuel efficiency but degrades the quality of the transmitted wavefront. In particular, an ellipsoidal dome introduces a varying aberration component that depends on the orientation of the aperture stop, which is pivoted about a fixed axis inside the dome. The transmitted ray bundle is incident only on a portion of the dome surface, and the included area lacks axial symmetry. To better understand the imaging characteristics of an ellipsoidal dome in this application, the first- and third-order optical properties of a constant thickness dome are investigated. Particular emphasis is placed on the geometry and symmetry of an ellipse, which impose certain constraints on the form of the aberration coefficients. The geometry is defined in terms of the aerodynamic fineness ratio, outer diameter, and center thickness of the dome. Emphasis is placed on third-order astigmatism and coma, which are shown to be the dominant aberration terms. The effects of varying the fineness ratio, thickness, and index of refraction of a dome are also investigated.

  2. Cotton Quality Indices of Spun Yarn

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cotton was spun into yarn at the Cotton Quality Research Station by each of three spinning methods (ring, vortex, and open end spinning) to determine if a relationship exits between cotton fiber properties and the quality of spun yarn. Cotton was grown and harvested in 2001-2005 from three of the l...

  3. Ruemker Hills - A lunar volcanic dome complex

    NASA Technical Reports Server (NTRS)

    Smith, E. I.

    1974-01-01

    The Ruemker Hills, a volcanic dome-flow complex in the northern Oceanus Procellarum, is characterized by overlapping plains-forming units with lobate scarps, volcanic domes, a 60-km ring, and a scarp which separates the plateau from surrounding mare materials. Plains-forming units are interpreted as fluid volcanic flows, and domes as viscous extrusions. One dome may be a stratovolcano. The ring system is discordant with regional structural trends and probably has a local origin. The Ruemker Hills is the closest lunar analog to the large Martian shield structures revealed on the Mariner 9 photographs of Mars.

  4. Dysprosium-free melt-spun permanent magnets.

    PubMed

    Brown, D N; Wu, Z; He, F; Miller, D J; Herchenroeder, J W

    2014-02-12

    Melt-spun NdFeB powders can be formed into a number of different types of permanent magnet for a variety of applications in electronics, automotive and clean technology industries. The melt-spinning process produces flake powder with a fine uniform array of nanoscale Nd2Fe14B grains. These powders can be net-shape formed into isotropic polymer-bonded magnets or hot formed into fully dense magnets. This paper discusses the influence of heavy rare earth elements and microstructure on the magnetic performance, thermal stability and material cost of NdFeB magnets. Evidence indicates that melt-spun nanocrystalline NdFeB magnets are less dependent on heavy rare earth elements for high-temperature performance than the alternative coarser-grained sintered NdFeB magnets. In particular, hot-pressed melt-spun magnets are an attractive low-cost solution for applications that require thermal stability up to 175-200 °C. PMID:24468854

  5. What factors control superficial lava dome explosivity?

    PubMed Central

    Boudon, Georges; Balcone-Boissard, Hélène; Villemant, Benoît; Morgan, Daniel J.

    2015-01-01

    Dome-forming eruption is a frequent eruptive style and a major hazard on numerous volcanoes worldwide. Lava domes are built by slow extrusion of degassed, viscous magma and may be destroyed by gravitational collapse or explosion. The triggering of lava dome explosions is poorly understood: here we propose a new model of superficial lava-dome explosivity based upon a textural and geochemical study (vesicularity, microcrystallinity, cristobalite distribution, residual water contents, crystal transit times) of clasts produced by key eruptions. Superficial explosion of a growing lava dome may be promoted through porosity reduction caused by both vesicle flattening due to gas escape and syn-eruptive cristobalite precipitation. Both processes generate an impermeable and rigid carapace allowing overpressurisation of the inner parts of the lava dome by the rapid input of vesiculated magma batches. The relative thickness of the cristobalite-rich carapace is an inverse function of the external lava dome surface area. Explosive activity is thus more likely to occur at the onset of lava dome extrusion, in agreement with observations, as the likelihood of superficial lava dome explosions depends inversely on lava dome volume. This new result is of interest for the whole volcanological community and for risk management. PMID:26420069

  6. What factors control superficial lava dome explosivity?

    NASA Astrophysics Data System (ADS)

    Boudon, Georges; Balcone-Boissard, Hélène; Villemant, Benoît; Morgan, Daniel J.

    2015-09-01

    Dome-forming eruption is a frequent eruptive style and a major hazard on numerous volcanoes worldwide. Lava domes are built by slow extrusion of degassed, viscous magma and may be destroyed by gravitational collapse or explosion. The triggering of lava dome explosions is poorly understood: here we propose a new model of superficial lava-dome explosivity based upon a textural and geochemical study (vesicularity, microcrystallinity, cristobalite distribution, residual water contents, crystal transit times) of clasts produced by key eruptions. Superficial explosion of a growing lava dome may be promoted through porosity reduction caused by both vesicle flattening due to gas escape and syn-eruptive cristobalite precipitation. Both processes generate an impermeable and rigid carapace allowing overpressurisation of the inner parts of the lava dome by the rapid input of vesiculated magma batches. The relative thickness of the cristobalite-rich carapace is an inverse function of the external lava dome surface area. Explosive activity is thus more likely to occur at the onset of lava dome extrusion, in agreement with observations, as the likelihood of superficial lava dome explosions depends inversely on lava dome volume. This new result is of interest for the whole volcanological community and for risk management.

  7. Microstructure and stability of melt spun INCONEL 713 LC

    NASA Technical Reports Server (NTRS)

    Antolovich, S. D.; Bowman, R. R.

    1986-01-01

    The alloy IN-714LC was used in an investigation of the effect of process parameters on the microstructure of a rapidly solidified melt-spun material. The resultant ribbon microstructure consisted of several distinct regions, each of which corresponds to a different thermal history during processing. A chill zone of equiaxed randomly-oriented grains exists in a region of the foil which was in contact with the wheel during casting. This zone develops into a dendritic growth morphology with distance away from the lower ribbon surface. Dendrites inclined in the direction of wheel rotation result from growth into a flowing stream. TEM studies showed that a cell structure formed, the cell size decreasing with increasing wheel speed. Aging studies indicated that the cell structure plays an important role in gamma prime precipitation. Results relating to heat treatments (as would be encountered in compaction and use) and the stability of the melt-spun structure are considered.

  8. A Radar Survey of Lunar Dome Fields

    NASA Technical Reports Server (NTRS)

    Carter, Lynn M.; Campbell, Bruce A.; Hawke, B. Ray; Bussey, Ben

    2011-01-01

    The near side of the Moon has several areas with a high concentration of volcanic domes. These low relief structures are considerably different in morphology from terrestrial cinder cones, and some of the domes may be similar to some terrestrial shields formed through Hawaiian or Strombolian eruptions from a central pipe vent or small fissure [1]. The domes are evidence that some volcanic lavas were more viscous than the mare flood basalts that make up most of the lunar volcanic flows. It is still not known what types of volcanism lead to the creation of specific domes, or how much dome formation may have varied across the Moon. Prior work has shown that some domes have unusual radar polarization characteristics that may indicate a surface or subsurface structure that is different from that of other domes. Such differences might result from different styles of late-stage volcanism for some of the domes, or possibly from differences in how the erupted materials were altered over time (e.g. by subsequent volcanism or nearby cratering events). For example, many of the domes in the Marius Hills region have high circular polarization ratios (CPRs) in S-band (12.6 cm wavelength) and/or P-band (70 cm wavelength) radar data [2]. The high CPRs are indicative of rough surfaces, and suggest that these domes may have been built from overlapping blocky flows that in some cases have been covered by meters of regolith [2, 3]. In other cases, domes have low circular polarization ratios indicative of smooth, rock-poor surfaces or possibly pyroclastics. The 12 km diameter dome Manilius 1 in Mare Vaporum [1], has a CPR value of 0.20, which is significantly below values for the surrounding basalts [4]. To better understand the range of surface properties and styles of volcanism associated with the lunar domes, we are currently surveying lunar dome fields including the Marius Hills, Cauchy/Jansen dome field, the Gruithuisen domes, and domes near Hortensius and Vitruvius.

  9. Manufacturing of 5.5 Meter Diameter Cryogenic Fuel Tank Domes for the NASA Ares I Rocket

    NASA Technical Reports Server (NTRS)

    Jones, Ronald E.; Carter, Robert W.

    2012-01-01

    The Ares I rocket is the first launch vehicle scheduled for manufacture under the National Aeronautic and Space Administration s (NASA s) Constellation program. A series of full-scale Ares I development articles have been constructed on the Robotic Weld Tool at the NASA George C. Marshall Space Flight Center in Huntsville, Alabama. The Robotic Weld Tool is a 100 ton, 7-axis, robotic manufacturing system capable of machining and friction stir welding large-scale space hardware. This presentation will focus on the friction stir welding of 5.5m diameter cryogenic fuel tank components; specifically, the liquid hydrogen forward dome (LH2 MDA) and the common bulkhead manufacturing development articles (CBMDA). The LH2 MDA was the first full-scale, flight-like Ares I hardware produced under the Constellation Program. It is a 5.5m diameter elliptical dome assembly consisting of eight gore panels, a y-ring stiffener and a manhole fitting. All components are made from aluminum-lithium alloy 2195. Conventional and self-reacting friction stir welding was used on this article. Manufacturing solutions will be discussed including the implementation of photogrammetry, an advanced metrology technique, as well as fixtureless welding. The LH2 MDA is the first known fully friction stir welded dome ever produced. The completion of four Common Bulkhead Manufacturing Development Articles (CBMDA) will also be highlighted. Each CBMDA consists of a 5.5m diameter spun-formed dome friction stir welded to a y-ring stiffener. The domes and y-rings are made of aluminum 2014 and 2219 respectively. An overview of CBMDA manufacturing processes and the effect of tooling on weld defect formation will be discussed.

  10. Emplacement Scenarios for Volcanic Domes on Venus

    NASA Technical Reports Server (NTRS)

    Glaze, Lori S.; Baloga, Steve M.; Stofan, Ellen R.

    2012-01-01

    One key to understanding the history of resurfacing on Venus is better constraints on the emplacement timescales for the range of volcanic features visible on the surface. A figure shows a Magellan radar image and topography for a putative lava dome on Venus. 175 such domes have been identified with diameters ranging from 19 - 94 km, and estimated thicknesses as great as 4 km. These domes are thought to be volcanic in origin and to have formed by the flow of viscous fluid (i.e., lava) on the surface.

  11. Modular combustor dome

    NASA Technical Reports Server (NTRS)

    Glynn, Christopher Charles (Inventor); Halila, Ely Eskenazi (Inventor); Bibler, John David (Inventor); Morris, David Byron (Inventor)

    2001-01-01

    A combustor dome module includes a mixer tube having a hollow heat shield sealingly joined around the outlet end thereof. The modules may then be assembled in an array for defining the combustor dome, with each module being individually removable therefrom.

  12. The association of lava dome growth with major explosive activity (VEI ≥ 4): DomeHaz, a global dataset

    NASA Astrophysics Data System (ADS)

    Ogburn, S. E.; Loughlin, S. C.; Calder, E. S.

    2015-05-01

    Investigation of the global eruptive records of particular types of volcanoes is a fundamental and valuable method of understanding what style of activity can be anticipated in the future and can highlight what might be expected or unusual in particular settings. This paper investigates the relationship between large explosions (volcanic explosivity index, VEI ≥ 4) and lava dome growth from 1000 AD to present and develops the DomeHaz database. DomeHaz contains information from 397 dome-forming episodes, including duration of dome growth, duration of pauses in extrusion, extrusion rates, and the timing and magnitude (VEI) of associated large explosions. Major explosive activity, when associated with dome growth, is more likely to occur before dome growth rather than during, or at the end of, dome-forming eruptions. In most cases where major explosive activity has been associated with dome growth, the eruptions occurred at basaltic andesite to andesitic volcanoes (the most common type of dome-forming volcano), but a greater proportion of dacitic and rhyolitic dome growth episodes were associated with large explosions. High extrusion rates (>10 m3 s-1) seem to be associated with large explosions and may inhibit degassing or destabilize existing domes, leading to explosive decompression. Large explosions may, alternatively, be followed by dome growth, which represents the clearing of residual magma from the conduit. Relationships extracted from the global record can be used to construct probability trees for new and ongoing dome-forming eruptions or can be used in conjunction with other types of event trees to aid in forecasting volcanic hazards during a crisis, especially for volcanoes where data are sparse.

  13. Magnetic properties of Mn-Bi melt-spun ribbons

    NASA Astrophysics Data System (ADS)

    Saito, Tetsuji; Nishimura, Ryuji; Nishio-Hamane, Daisuke

    2014-01-01

    Mn-Bi melt-spun ribbons with the low temperature phase (LTP) of MnBi were produced by melt-spinning and subsequent annealing. The as-rapidly quenched Mn-Bi melt-spun ribbons contained some LTP MnBi phase and exhibited a high coercivity exceeding 8 kOe. Annealing of the melt-spun ribbons resulted in an increase in the amount of the LTP MnBi phase. A maximum remanence value of 42 emu/g was achieved in Mn50Bi50 melt-spun ribbon annealed at 673 K for 1 h. High-temperature measurements revealed that the coercivity of the annealed Mn50Bi50 melt-spun ribbon increased with increasing ambient temperature. Although the Mn50Bi50 melt-spun ribbons showed a much smaller coercivity than Nd15Fe77B8 melt-spun ribbon at room temperature, it exhibited a higher coercivity at temperatures of 473 K and higher. Therefore, the magnetic properties of Mn50Bi50 melt-spun ribbon are comparable to those of Nd-Fe-B melt-spun ribbon at an ambient temperature of 473 K and become superior to those of Nd-Fe-B melt-spun ribbon at 573 K.

  14. What factors control the superficial lava dome explosivity?

    NASA Astrophysics Data System (ADS)

    Boudon, Georges; Balcone-Boissard, Hélène; Villemant, Benoit; Morgan, Daniel J.

    2015-04-01

    Dome-forming eruption is a frequent eruptive style; lava domes result from intermittent, slow extrusion of viscous lava. Most dome-forming eruptions produce highly microcrystallized and highly- to almost totally-degassed magmas which have a low explosive potential. During lava dome growth, recurrent collapses of unstable parts are the main destructive process of the lava dome, generating concentrated pyroclastic density currents (C-PDC) channelized in valleys. These C-PDC have a high, but localized, damage potential that largely depends on the collapsed volume. Sometimes, a dilute ash cloud surge develops at the top of the concentrated flow with an increased destructive effect because it may overflow ridges and affect larger areas. In some cases, large lava dome collapses can induce a depressurization of the magma within the conduit, leading to vulcanian explosions. By contrast, violent, laterally directed, explosions may occur at the base of a growing lava dome: this activity generates dilute and turbulent, highly-destructive, pyroclastic density currents (D-PDC), with a high velocity and propagation poorly dependent on the topography. Numerous studies on lava dome behaviors exist, but the triggering of lava dome explosions is poorly understood. Here, seven dome-forming eruptions are investigated: in the Lesser Antilles arc: Montagne Pelée, Martinique (1902-1905, 1929-1932 and 650 y. BP eruptions), Soufrière Hills, Montserrat; in Guatemala, Santiaguito (1929 eruption); in La Chaîne des Puys, France (Puy de Dome and Puy Chopine eruptions). We propose a new model of superficial lava-dome explosivity based upon a textural and geochemical study (vesicularity, microcrystallinity, cristobalite distribution, residual water contents, crystal transit times) of clasts produced by these key eruptions. Superficial explosion of a growing lava dome may be promoted through porosity reduction caused by both vesicle flattening due to gas escape and syn-eruptive cristobalite

  15. Pancakelike domes on Venus

    NASA Astrophysics Data System (ADS)

    McKenzie, Dan; Ford, Peter G.; Liu, Fang; Pettengill, Gordon H.

    1992-10-01

    A comparison between the shape of seven large domes on the plains of Venus (volumes between 100 and 1000 cu cm) and that of an axisymmetric gravity current spreading over a rigid horizontal surface is presented. Both the altimetric profiles and the horizontal projection of the line of intersection of domes on the synthetic aperture radar images agree well with the theoretical similarity solution for a Newtonian fluid but not with the shape calculated for a rigid-plastic rheology or with that for a static model with a strong skin. The stress induced by the flow in the plains material below is obtained, and is found to be large enough to produce the short radial cracks in the surface of the plains beyond the domes. The viscosity of the domes can be estimated from their thermal time constant if spreading is possible only when the fluid is hot and lies between 10 exp 14 and 10 exp 17 Pa s. Laboratory experiments show that such viscosities correspond to temperatures of 610 to 700 C in dry rhyolitic magmas. It is shown that dome development can be understood using simple fluid dynamical ideas and that the magmas involved can be produced by wet melting at depths below 10 km, followed by eruption and degassing.

  16. In-situ Microwave Brightness Temperature Variability from Ground-based Radiometer Measurements at Dome C in Antarctica Induced by Wind-formed Features

    NASA Technical Reports Server (NTRS)

    Royer, A.; Picard, G.; Arnaud, L.; Brucker, L.; Fily, M..

    2014-01-01

    Space-borne microwave radiometers are among the most useful tools to study snow and to collect information on the Antarctic climate. They have several advantages over other remote sensing techniques: high sensitivity to snow properties of interest (temperature, grain size, density), subdaily coverage in the polar regions, and their observations are independent of cloud conditions and solar illumination. Thus, microwave radiometers are widely used to retrieve information over snow-covered regions. For the Antarctic Plateau, many studies presenting retrieval algorithms or numerical simulations have assumed, explicitly or not, that the subpixel-scale heterogeneity is negligible and that the retrieved properties were representative of whole pixels. In this presentation, we investigate the spatial variations of brightness temperature over arange of a few kilometers in the Dome C area (Antarctic Plateau).

  17. Pancakelike domes on Venus

    NASA Astrophysics Data System (ADS)

    McKenzie, Dan; Ford, Peter G.; Liu, Fang; Pettengill, Gordon H.

    1992-12-01

    The shape of seven large domes on the plains of Venus, with volumes between 100 and 1000 cu km, is compared with that of an axisymmetric gravity current spreading over a rigid horizontal surface. Both the altimetric profiles and the horizontal projection of the line of intersection of domes on the SAR images agree well with the theoretical similarity solution for a newtonian fluid, but not with the shape calculated for a rigid-plastic rheology, nor with that for a static model with a strong skin. As a viscous current spreads, it generates an isotropic strain rate tensor whose magnitude is independent of radius. Such a flow can account for the randomly oriented cracks that are uniformly distributed on the surface of the domes. The stress induced by the flow in the plains material below is obtained, and is probably large enough to produce the short radial cracks in the surface of the plains beyond the domes. The viscosity of the domes can be estimated from their thermal time constants if spreading is possible only when the fluid is hot, and lies between 1014 and 1017 Pa s. Laboratory experiments show that such viscosities correspond to temperatures of 610 - 690 C in dry rhyolitic magmas. These temperatures agree with laboratory measurements of the solidus temperature of wet rhyolite. These results show that the development of the domes can be understood using simple fluid dynamical ideas, and that the magmas involved can be produced by wet melting at depths below 10 km, followed by eruption and degassing.

  18. Pancakelike domes on Venus

    NASA Technical Reports Server (NTRS)

    Mckenzie, Dan; Ford, Peter G.; Liu, Fang; Pettengill, Gordon H.

    1992-01-01

    The shape of seven large domes on the plains of Venus, with volumes between 100 and 1000 cu km, is compared with that of an axisymmetric gravity current spreading over a rigid horizontal surface. Both the altimetric profiles and the horizontal projection of the line of intersection of domes on the SAR images agree well with the theoretical similarity solution for a newtonian fluid, but not with the shape calculated for a rigid-plastic rheology, nor with that for a static model with a strong skin. As a viscous current spreads, it generates an isotropic strain rate tensor whose magnitude is independent of radius. Such a flow can account for the randomly oriented cracks that are uniformly distributed on the surface of the domes. The stress induced by the flow in the plains material below is obtained, and is probably large enough to produce the short radial cracks in the surface of the plains beyond the domes. The viscosity of the domes can be estimated from their thermal time constants if spreading is possible only when the fluid is hot, and lies between 10(exp 14) and 10(exp 17) Pa s. Laboratory experiments show that such viscosities correspond to temperatures of 610 - 690 C in dry rhyolitic magmas. These temperatures agree with laboratory measurements of the solidus temperature of wet rhyolite. These results show that the development of the domes can be understood using simple fluid dynamical ideas, and that the magmas involved can be produced by wet melting at depths below 10 km, followed by eruption and degassing.

  19. Internal ballistics model update for ASRM dome

    NASA Technical Reports Server (NTRS)

    Bowden, Mark H.; Jenkins, Billy Z.

    1991-01-01

    A previous report (no. 5-32279, contract NAS8-36955, DO 51) describes the measures taken to adapt the NASA Complex Burning Region Model and code so that is was applicable to the Advanced Solid Rocket Motor as envisioned at that time. The code so modified was called the CBRM-A. CBRM-A could calculate the port volume and burning area for the star, transition, and cylindrically perforated regions of the motor. Described here is a subsequent effort to add computation of port volume and burning area for the Advanced Solid Rocket Motor head dome. Sample output, input, and overview of the models are included. The software was configured in two forms - a stand alone head dome code and a code integrating the head dome solution with the CBRM-A.

  20. Steep-sided domes on Venus - Characteristics, geologic setting, and eruption conditions from Magellan data

    NASA Technical Reports Server (NTRS)

    Pavri, Betina; Head, James W., III; Klose, K. B.; Wilson, Lionel

    1992-01-01

    A survey of more than 95 percent of the Venus surface reveals 145 steep-sided domes which can be subdivided into a variety of morphologic forms, the most common being shaped like inverted bowls or flat-topped domes. Results of a preliminary analysis of the distribution and geologic setting of the domes are presented. The relation of the domes to analogous terrestrial features is examined, and possible models for their mode of emplacement are outlined.

  1. Lava flows and domes

    SciTech Connect

    Fink, J. )

    1989-01-01

    This book discusses emplacement of silicic domes and mafic lava flows. The authors have utilized the combination of field, experimental and theoretical methods to constrain various characteristics of recently-emplaced lavas, including dimensions, growth rates, surface morphology, deformation styles, rheology, and volatile contents. Filed measurements from numerous volcanoes are presented. Focus is on data from Mount St. Helens. The value of such investigations is addressed.

  2. Investigation on the magnetocaloric effect in RNi2 (R: Dy, tb) melt-spun ribbon

    NASA Astrophysics Data System (ADS)

    de Souza, M. V.

    2016-08-01

    We report a theoretical and experimental investigation on the magnetocaloric properties of the rare earth RNi2 (R=Dy,Tb) in melt-spun ribbon and bulk form. The theoretical calculations were performed using a Hamiltonian model including the Zeeman-exchange interactions and the crystalline electrical field. Thus the magnetocaloric potential was calculated in the easy magnetic axes, in order an average over all of the possible directions. The isothermal entropy-change dependence on temperature calculated was compared with available experimental data for melt-spun ribbon and bulk material. We also investigated, theoretically and experimentally, the behavior of a DyNi2 and TbNi2 composite with optimized molar proportions and discussed this in the context of the optimum regeneration Ericsson cycle.

  3. Sustainable Outreach: Lessons Learned from Space Update and Discovery Dome

    NASA Astrophysics Data System (ADS)

    Reiff, P. H.; Sumners, C.; Law, C. C.

    2009-12-01

    A sustainable program lives on past its initial funding cycle, and develops a network of users that ensures continued life, either by fees, advertising revenue, or by making the program more successful in later sponsored grants. Teachers like free things, so having a sponsor for products such as lithographs or CD-Roms is key to wide distribution. In 1994 we developed “Space Update®”, under the NASA “Public Use of the Internet” program. It has new editions annually, with over 40,000 distributed so far (many purchased but most free at teacher and student workshops). In 1996 we created a special edition “Space Weather®”, which includes the space weather module from Space Update plus other resources. Initially developed with funding from the IMAGE mission, it is now sponsored by Cluster and MMS. A new edition is published annually and distributed in the “Sun-Earth Day” packet; total distribution now exceeds 180,000. “Earth Update” was created in 1999 under cooperative agreement “Museums Teaching Planet Earth”. It now has a total distribution of over 20,000. Both Earth Update and Space Update were developed to be museum kiosk software, and more than 15 museums have them on display. Over 4,000 users are active in our e-Teacher network and 577 in our museum educator network. Although these can certainly be considered successful because of their longevity and user base, we have had a far more dramatic sustainable program arise in the last six years… the “Discovery Dome®”. Invented at HMNS and developed under NASA Cooperative Agreement “Immersive Earth”, this dome was the first digital portable planetarium that also showed fulldome movies with an interactive interface (first shown to the public at the Dec 2003 AGU meeting). The Discovery Dome network (tinyurl.com/DiscDome) has spun those initial 6 NASA-funded domes into over 90 installations in 22 states and 23 countries. Creating high quality content is quite expensive and so needs

  4. The longevity of lava dome eruptions

    NASA Astrophysics Data System (ADS)

    Wolpert, Robert L.; Ogburn, Sarah E.; Calder, Eliza S.

    2016-02-01

    Understanding the duration of past, ongoing, and future volcanic eruptions is an important scientific goal and a key societal need. We present a new methodology for forecasting the duration of ongoing and future lava dome eruptions based on a database (DomeHaz) recently compiled by the authors. The database includes duration and composition for 177 such eruptions, with "eruption" defined as the period encompassing individual episodes of dome growth along with associated quiescent periods during which extrusion pauses but unrest continues. In a key finding, we show that probability distributions for dome eruption durations are both heavy tailed and composition dependent. We construct objective Bayesian statistical models featuring heavy-tailed Generalized Pareto distributions with composition-specific parameters to make forecasts about the durations of new and ongoing eruptions that depend on both eruption duration to date and composition. Our Bayesian predictive distributions reflect both uncertainty about model parameter values (epistemic uncertainty) and the natural variability of the geologic processes (aleatoric uncertainty). The results are illustrated by presenting likely trajectories for 14 dome-building eruptions ongoing in 2015. Full representation of the uncertainty is presented for two key eruptions, Soufriére Hills Volcano in Montserrat (10-139 years, median 35 years) and Sinabung, Indonesia (1-17 years, median 4 years). Uncertainties are high but, importantly, quantifiable. This work provides for the first time a quantitative and transferable method and rationale on which to base long-term planning decisions for lava dome-forming volcanoes, with wide potential use and transferability to forecasts of other types of eruptions and other adverse events across the geohazard spectrum.

  5. Evaluation of the structure and stratigraphy over Richton Dome, Mississippi

    SciTech Connect

    Werner, M.L.

    1986-05-01

    The structure and stratigraphy over Richton Salt Dome, Mississippi, have been evaluated from 70 borings that were completed to various depths above the dome. Seven lithologic units have been identified and tentatively correlated with the regional Tertiary stratigraphy. Structure-contour and thickness maps of the units show the effects of dome growth from Eocene through early Pliocene time. Growth of the salt stock from late Oligocene through early Pliocene is estimated to have averaged 0.6 to 2.6 centimeters (0.2 to 1.1 inches) per 1000 years. No dome growth has occurred since the early Pliocene. The late Oligocene to early Pliocene strata over and adjacent to the dome reflect arching over the entire salt stock; some additional arching over individual centers may represent pre-Quaternary differential movement in the salt stock. The lithology and structure of the caprock at the Richton Salt Dome indicate that the caprock probably was completely formed by late Oligocene. In late Oligocene, the caprock was fractured by arching and altered by gypsum veining. Since late Oligocene, there are no indications of significant hydrologic connections through the caprock - that is, there are no indications of dissolution collapse or further anhydrite caprock accumulation. This structural and stratigraphic analysis provides insights on dome growth history, dome geometry, and neardome hydrostratigraphy that will aid in planning site characterization field activities, including an exploratory shaft, and in the conceptual design of a high-level waste (HLW) repository.

  6. A spun elastomeric graft for dialysis access.

    PubMed

    Drasler, W J; Wilson, G J; Stenoien, M D; Jenson, M L; George, S A; Dutcher, R G; Possis, Z C

    1993-01-01

    A new composite vascular graft was developed using electrostatic spinning technology. The graft is primarily microfibrous polydimethylsiloxane spun onto a mandrel; a small diameter polyester yarn provides additional strength while minimizing wall thickness, and a helical bead provides crush and kink resistance. Eighteen grafts were implanted in a mongrel canine arteriovenous shunt model for 12 months. The grafts were implanted in femoral artery to femoral vein loops and were cannulated using three pairs of 16 gauge dialysis needles per week. Grafts were evaluated during each puncture session, and also followed using angiography. Histologic study of explanted grafts, regional lymph nodes, and lungs was performed. The grafts provided excellent handling and puncture characteristics, with no bleeding through the graft wall at puncture sites. Cumulative patency of these punctured grafts was 88% at 6 months and 80% at 1 year. Histologic study showed external fibroconnective tissue encapsulation of the grafts, with tissue growth through the interstices of the graft consisting of a microvascular network surrounded predominantly by histiocytes, many multinucleated foreign body giant cells, with some fibroblasts and collagen formation also present. Little luminal thrombus was seen at puncture sites in the patent grafts, and there was no evidence of pulmonary thromboemboli. This new elastomeric graft shows excellent promise for dialysis access; similar grafts under development may also find application for small diameter peripheral vascular reconstruction. PMID:8324257

  7. Mississippian oolites on West Virginia dome

    SciTech Connect

    Koehler, B.; Smosna, R. )

    1989-08-01

    The West Virginia dome, a positive feature during the Early Mississippian, was submerged during a Meramec-Chester transgression and became the site for ooid sedimentation. The dome's axis trended eastwest through Randolph County, West Virginia, where four outcrops of the lower Pickaway Limestone (Greenbrier Group) were studied. Pickaway oolites formed as mobile sand belts that paralleled the dome's axis. In detail, these belts consisted of sand waves up to 2 m in height that migrated north and south under the influence of tidal currents. Along the crest, both flood and ebb currents moved the sediment, whereas farther away flood tides dominated. Sand bodies shoaled upward with time, the sediment becoming coarser grained and better sorted to the top; large wedge-shaped cross-bed sets gave way to planar bedding; and frequently the ooid shoals were subaerially exposed. Ooids and other grains have been extensively micritized, indicating a slow sedimentation rate, and small-scale ripples record the effect of minor wave action. North of the dome, muddy skeletal sands accumulated in a somewhat restricted gulf. To the south along a very gentle sea floor, the ooid shoals passed into fully marine skeletal sands. On the east, a nearby landmass supplied locally large volumes of detrital quartz. The lower Pickaway was deposited during a single rise and fall of sea level that produced two oolites at each outcrop separated by off-shore sediments. This stratigraphic sequence constitutes a fifth-order cycle 7-26 m thick.

  8. Emplacement of Volcanic Domes on Venus and Europa

    NASA Technical Reports Server (NTRS)

    Quick, Lynnae C.; Glaze, Lori S.; Baloga, Steve M.

    2015-01-01

    Placing firmer constraints on the emplacement timescales of visible volcanic features is essential to obtaining a better understanding of the resurfacing history of Venus. Fig. 1 shows a Magellan radar image and topography for a putative venusian lava dome. 175 such domes have been identified, having diameters that range from 19 - 94 km, and estimated thicknesses as great as 4 km [1-2]. These domes are thought to be volcanic in origin [3], having formed by the flow of a viscous fluid (i.e., lava) onto the surface. Among the unanswered questions surrounding the formation of Venus steep-sided domes are their emplacement duration, composition, and the rheology of the lava. Rheologically speaking, maintenance of extremely thick, 1-4 km flows necessitates higher viscosity lavas, while the domes' smooth upper surfaces imply the presence of lower viscosity lavas [2-3]. Further, numerous quantitative issues, such as the nature and duration of lava supply, how long the conduit remained open and capable of supplying lava, the volumetric flow rate, and the role of rigid crust in influencing flow and final morphology all have implications for subsurface magma ascent and local surface stress conditions. The surface of Jupiter's icy moon Europa exhibits many putative cryovolcanic constructs [5-7], and previous workers have suggested that domical positive relief features imaged by the Galileo spacecraft may be volcanic in origin [5,7-8] (Fig. 2). Though often smaller than Venus domes, if emplaced as a viscous fluid, formation mechanisms for europan domes may be similar to those of venusian domes [7]. Models for the emplacement of venusian lava domes (e.g. [9-10]) have been previously applied to the formation of putative cryolava domes on Europa [7].

  9. Mechanical properties of continuously spun fibers of carbon nanotubes.

    PubMed

    Motta, Marcelo; Li, Ya-Li; Kinloch, Ian; Windle, Alan

    2005-08-01

    We report on the mechanical properties of fibers consisting of pure carbon nanotube fibers directly spun from an aerogel formed during synthesis by chemical vapor deposition. The continuous withdrawal of product from the gas phase imparts a high commercial potential to the process, either for the production of particularly strong fibers or for the economic production of bulk quantities of carbon nanotubes. Tensile tests were performed on fibers produced from the dissociation of three different hydrocarbons, namely, ethanol, ethylene glycol, and hexane, with a range of iron (catalyst) concentrations. The conditions were chosen to lie within the range known to enable satisfactory continuous spinning, the iron concentration being varied within this range. Increasing proportions of single wall nanotubes were found as the iron concentration was decreased, conditions which also produced fibers of best strength and stiffness. The maximum tensile strength obtained was 1.46 GPa (equivalent to 0.70 N/tex assuming a density of 2.1 g/cm(3)). The experiments indicate that significant improvements in the mechanical properties can be accomplished by optimizing the process conditions. PMID:16089483

  10. Melt spun aluminium alloys for moulding optics

    NASA Astrophysics Data System (ADS)

    Gubbels, G.; Tegelaers, L.; Senden, R.

    2013-09-01

    Melt spinning is a rapid quenching process that makes it possible to create materials with a very fine microstructure. Due to this very fine microstructure the melt spinning process is an enabler for diamond turning optics and moulds without the need of post-polishing. Using diamond turning of melt spun aluminium one can achieve <=2 nm Rq surface roughness. Application areas are imaging and projection optics, mirrors, moulds for contact lenses and spectacles. One of the alloys that RSP produces is RSA-905. This alloy has a solid track record as a better and cheaper concept in the application of moulds for optical components such as contact lenses. The RSA-905 is a dispersion hardened amorphous-like alloy that keeps its properties when exposed to elevated temperatures (up to 380°C). This gives the material unique features for optics moulding applications. RSA-905 moulds are cheaper and better than traditional mould concepts such as copper or brass with or without NiP plating. In addition logistics can be simplified significantly: from typical weeks-months into days-week. Lifetime is typically in the range of 100.000 - 200.000 shots. For high volume production typically ranging from several 100.000 - several 1.000.000 shots, NiP plated steel moulds are typically used. By using an appropriate optical coating concept RSA-905 can be upgraded to a competitive alternative to steel in terms of price, performance and logistics. This paper presents some recent developments for improved mould performance of such concept. Hardness, wear resistance and adhesion are topics of interest and they can be applied by special coatings such as diamond-like carbon (DLC) and chromium nitride (CrN). These coatings make the aluminium alloy suitable for moulding mass production of small as well as larger optics, such as spectacle lenses.

  11. The role of synoptic-scale features and advection in prolonged warming and generation of different forms of precipitation at Dome Fuji station, Antarctica, following a prominent blocking event

    NASA Astrophysics Data System (ADS)

    Hirasawa, Naohiko; Nakamura, Hisashi; Motoyama, Hideaki; Hayashi, Masahiko; Yamanouchi, Takashi

    2013-07-01

    A blocking event over the East Antarctic ice sheet during June 1997 generated the highest surface air temperature (which increased from around -70°C to around -30°C) and pressure of that year at the Dome Fuji station (77.5°S, 40°E). Following the blocking event, the anomalously high air temperature (around -50°C to -60°C) and pressure were maintained at the surface for about 1 week. This study investigates how these warm conditions were maintained and documents the sequential occurrence of two forms of synoptic-scale high-pressure systems with conditions that produced precipitation by different processes in each case. In the first half of the warm period, a solitary high-pressure system (the Solitary High) formed over the Dome Fuji station and traveled west over East Antarctica after being cut off from the tip of the preceding blocking ridge. During this phase, tropospheric temperatures were higher, and surface-based temperature inversions were more intense than during the following period. While a dry-out developed in the troposphere below about 300 hPa, the precipitation of ice crystals in the surface-based temperature inversion layer was generated by deposition of moisture that had become trapped in the boundary layer after being transported onto the continent by the previous blocking ridge. This mechanism has not been previously reported elsewhere. During the second half of the warm period, a ridge of high pressure (the Transcontinental Ridge) traversed East Antarctica almost completely, and its western section was amplified by the merging of the Solitary High with a preceding quasi-stationary Rossby wave train propagating along the Southern Ocean. This ridge allowed an intrusion of warm, moist air from the Weddell Sea toward the station, which generated precipitation throughout the whole troposphere by orographic uplift once again, and ended the dry-out. This represents the typical mechanism of both moisture transportation and the generation of

  12. Emplacement and composition of steep-sided domes on Venus

    NASA Astrophysics Data System (ADS)

    Stofan, Ellen R.; Anderson, Steven W.; Crown, David A.; Plaut, Jeffrey J.

    2000-11-01

    Steep-sided domes on Venus have surface characteristics that can provide information on their emplacement, including relatively smooth upper surfaces, radial and polygonal fracture patterns, and pits. These characteristics indicate that domes have surface crusts which are relatively unbroken, have mobile interiors after emplacement, and preserve fractures from only late in their history in response to endogenous growth or sagging of the dome surface. We have calculated the time necessary to form a 12-cm-thick crust for basalt and rhyolite under current terrestrial and Venusian ambient conditions. A 12-cm-thick crust will form in all cases in <10 hours. Although Venusian lava flows should develop a brittle carapace during emplacement, only late-stage brittle fractures are preserved at steep-sided domes. We favor an emplacement model where early-formed surface crusts are entrained or continually annealed as they deform to accommodate dome growth. Entrainment and annealing of fractures are not mutually exclusive processes and thus may both be at work during steep-sided dome emplacement. Our results are most consistent with basaltic compositions, as rhyolitic lavas would quickly form thick crusts which would break into large blocks that would be difficult to entrain or anneal. However, if Venus has undergone large temperature excursions in the past (producing ambient conditions of 800-1000 K [e.g., Bullock and Grinspoon, 1996, 1998]), rhyolitic lavas would be unable to form crusts at high surface temperatures and could produce domes with surface characteristics consistent with those of Venusian steep-sided domes.

  13. Analysis of aerothermal loads on spherical dome protuberances

    NASA Technical Reports Server (NTRS)

    Olsen, G. C.; Smith, R. E.

    1983-01-01

    Hypersonic flow over spherical dome protuberances was investigated to determine increased pressure and heating loads to the surface. The configuration was mathematically modeled in a time-dependent three-dimensional analysis of the conservation of mass, momentum (Navier-Stokes), and energy equations. A boundary mapping technique was used to obtain a rectangular parallelepiped computational domain, a MacCormack explicit time-split predictor-corrector finite difference algorithm was used to obtain solutions. Results show local pressures and heating rates for domes one-half, one, and two boundary layer thicknesses high were increased by factors on the order of 1.4, 2, and 6, respectively. Flow over the lower dome was everywhere attached while flow over the intermediate dome had small windward and leeside separations. The higher dome had an unsteady windward separation region and a large leeside separation region. Trailing vortices form on all domes with intensity increasing with dome height. Discussion of applying the results to a thermally bowed thermal protection system are presented.

  14. Yukimarimo at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Petenko, Igor

    2015-04-01

    Natural frostballs called "yukimarimo" were observed at at Dome C, Antarctica, during the winter of 2014. Frostballs have spheroidal or lightly oblate form. Four cases of the yukimarimo were observed in the period April - August. The characteristics concerning their sizes, density, distribution over the surface varied for different cases. The diameters ranged from several millimetres to 120 mm, the density ranged from 15 to 60 kg/m3 . The heaviest one weighted 14 g and had a diameter of ≈90 mm. The initial "material" from which they formed resembles candy floss or fluff. In one case, only the initial stage of the small-yukimarimo formation was observed; the further development was interrupted. The meteorological conditions observed diuring the yukimarimo were not particular. The near-surface temperature varied between -70° and -60°C. Winds favouring to the yukimarimo formation were low, but not less than 2 m/s^1. A two-step mechanism of their formation and development is assumed: 1) at the initial stage, an electrostatic attraction favours the clumping of ice crystals to form some ice mass resembling floss structured in spherical pieces; 2) some pieces of ice floss are rolled by the wind and collect more ice crystals and increase in size like to a tumbleweed. Special comprehensive studies of electrical properties of the frost during the initial stage are necessary. Videos of moving yukimarimo at different stages of their formation are available.

  15. Spun microstructured optical fibres for Faraday effect current sensors

    SciTech Connect

    Chamorovsky, Yury K; Starostin, Nikolay I; Morshnev, Sergey K; Gubin, Vladimir P; Ryabko, Maksim V; Sazonov, Aleksandr I; Vorob'ev, Igor' L

    2009-11-30

    We report a simple design of spun holey fibres and the first experimental study of the magneto-optical response of spun microstructured fibres with high built-in birefringence. Such fibres enable the Faraday-effect-induced phase shift to effectively accumulate in a magnetic field even at very small coiling diameters. For example, the magneto-optical sensitivity of a 5-mm-diameter fibre coil consisting of 100 turns is {approx}70% that of an ideal fibre, in good agreement with theoretical predictions. (optical fibres and fibreoptic sensors)

  16. First field identification of the Cuonadong dome in southern Tibet: implications for EW extension of the North Himalayan gneiss dome

    NASA Astrophysics Data System (ADS)

    Fu, Jiangang; Li, Guangming; Wang, Genhou; Huang, Yong; Zhang, Linkui; Dong, Suiliang; Liang, Wei

    2016-07-01

    The Cuonadong dome exposes in east-southern margin of the North Himalayan gneiss domes (NHGD), which is reported first time in this study. The Cuonadong dome is located at the southern part of the Zhaxikang ore concentration area, which is divided into three tectono-lithostratigraphic units by two curved faults around the dome geometry from upper to lower (or from outer to inner): the upper unit, middle unit and lower unit, and the outer fault is Nading fault, while the inner fault is Jisong fault. The Cuonadong dome is a magmatic orthogneiss and leucogranite mantled by orthogneiss and metasedimentary rocks, which in turn are overlain by Jurassic metasedimentary and sedimentary rocks. The grades of metamorphism and structural deformation increase towards the core, which is correspondence with the Ridang Formation low-metamorphic schist, tourmaline granitic-biotite gneiss, garnet-mica gneiss and mylonitic quartz-mica gneiss. The Cuonadong dome preserves evidences for four major deformational events: firstly top-to-S thrust (D1), early approximately N-S extensional deformation (D2), main approximately E-W extensional deformation (D3), and late collapse structural deformation (D4) around the core of the Cuonadong dome, which are consistent to three groups lineation: approximately N-S-trending lineation including L1 and L2, E-W trending L3, and L4 with plunging towards outside of the dome, respectively. The formation of the Cuonadong dome was probably resulted from the main E-W extensional deformation which is a result of eastward flow of middle or lower crust from beneath Tibet accommodated by northward oblique underthrusting of Indian crust beneath Tibet. The establishment of the Cuonadong dome enhanced the E-W extension of the NHGD, which is further divided into two structural dome zones according to the different extensional directions: approximately N-S extensional North Himalayan gneiss domes (NS-NHGD) and E-W extensional North Himalayan gneiss domes (EW

  17. Geodesic Domes in the Classroom.

    ERIC Educational Resources Information Center

    Lund, Charles

    1978-01-01

    Some practical, hands-on ways in which ideas about geodesic domes can be used in secondary school mathematics are described. Instructions for constructing a one-frequency geodesic sphere are given. (MP)

  18. Factors controlling lava dome morphology

    NASA Technical Reports Server (NTRS)

    Fink, Jonathan; Bridges, Nathan; Griffiths, Ross

    1991-01-01

    Research suggests that variations in lava dome morphology on different planets will depend much more critically on local gravity and the style of eruption than on the magma composition, ambient temperature, or the relative roles of convective and radiative cooling. Eruption style in turn reflects differences in tectonic conditions and the ability of magma to exsolve volatiles. Observed crude correlations between silica content and calculated yield strengths for terrestrial lava flows and domes probably are do to differences in extrusion rate and volatile solubility, rather than intrinsic rheological properties. Thus, even after taking the known effect of gravity into account, observed differences in gross dome morphology on different planets cannot by themselves be directly related to composition. Additional information such as the distribution of surface textures and structures, or spectroscopic data will be needed to conclusively establish dome compositions.

  19. A Dome Amidst the Hexagons

    ERIC Educational Resources Information Center

    American School and University, 1976

    1976-01-01

    Describes the design of the gymnasium of York (South Carolina) Comprehensive High School, a circular 12,000 square foot structure with a prefabricated domed roof constructed of steel hubs and curved wooden beams. (JG)

  20. Experimental Compaction of Pumiceous Dome Lavas

    NASA Astrophysics Data System (ADS)

    Kendrick, J.; Ashwell, P. A.; Lavalleé, Y.; Kennedy, B. M.; Hess, K. U.; Cole, J.; Dingwell, D. B.

    2012-04-01

    compaction process. We infer that the incongruent development of porosity and permeability in pumiceous dome lavas can lead to a localised build-up of overpressures during volcanic eruptions, resulting in lava dome failure. In extreme cases compaction of pumiceous lava may form a volcanic plug in the upper conduit which can result in catastrophic explosive eruptions.

  1. Integrated field and numerical modeling investigation of crustal flow mechanisms and trajectories in migmatite domes

    NASA Astrophysics Data System (ADS)

    Whitney, Donna; Teyssier, Christian; Rey, Patrice

    2016-04-01

    Integrated field-based and modeling studies provide information about the driving mechanisms and internal dynamics of migmatite domes, which are important structures for understanding the rheology of the lithosphere in orogens. Dome-forming processes range from extension (isostasy) driven flow to density (buoyancy) driven systems. Vertical flow (up or down) is on the scale of tens of km. End-member buoyancy-driven domes are typically Archean (e.g., Pilbara, Australia). Extension-driven systems include the migmatite domes in metamorphic core complexes of the northern North American Cordillera, as well as some domes in Variscan core complexes. The Entia dome of central Australia is a possible hybrid dome in which extension and density inversion were both involved in dome formation. The Entia is a "double dome", comprised of a steep high-strain zone bordered by high melt-fraction migmatite (subdomes). Field and numerical modeling studies show that these are characteristics of extension-driven domes, which form when flowing deep crust ascends beneath normal faults in the upper crust. Entia dome migmatite shows abundant evidence for extension, in addition to sequences of cascading, cuspate folds (well displayed in amphibolite) that are not present in the carapace of the dome, that do not have a consistent axial planar fabric, and that developed primarily at subsolidus conditions. We propose that these folds developed in mafic layers that had a density contrast with granodioritic migmatite, and that they formed during sinking of a denser layer above the rising migmatite subdomes. Extension-driven flow of partially molten (granodioritic) crust was therefore accompanied by sinking of a dense, mafic, mid-crustal layer, resulting in complex P-T-d paths of different lithologic units within the dome. This scenario is consistent with field and 2D modeling results, which together show how a combination of structural geology, metamorphic petrology, and modeling can illuminate the

  2. Europa Ridges, Hills and Domes

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This moderate-resolution view of the surface of one of Jupiter's moons, Europa, shows the complex icy crust that has been extensively modified by fracturing and the formation of ridges. The ridge systems superficially resemble highway networks with overpasses, interchanges and junctions. From the relative position of the overlaps, it is possible to determine the age sequence for the ridge sets. For example, while the 8-kilometer-wide (5-mile) ridge set in the lower left corner is younger than most of the terrain seen in this picture, a narrow band cuts across the set toward the bottom of the picture, indicating that the band formed later. In turn, this band is cut by the narrow 2- kilometer-wide (1.2-mile) double ridge running from the lower right to upper left corner of the picture. Also visible are numerous clusters of hills and low domes as large as 9 kilometers (5.5 miles) across, many with associated dark patches of non-ice material. The ridges, hills and domes are considered to be ice-rich material derived from the subsurface. These are some of the youngest features seen on the surface of Europa and could represent geologically young eruptions.

    This area covers about 140 kilometers by 130 kilometers (87 miles by 81 miles) and is centered at 12.3 degrees north latitude, 268 degrees west longitude. Illumination is from the east (right side of picture). The resolution is about 180 meters (200 yards) per pixel, meaning that the smallest feature visible is about a city block in size. The picture was taken by the Solid State Imaging system on board the Galileo spacecraft on February 20, 1997, from a distance of 17,700 kilometers (11,000 miles) during its sixth orbit around Jupiter.

    The Jet Propulsion Laboratory, Pasadena, CA, manages the mission for NASA's Office of Space Science, Washington D.C. This image and other images and data received from Galileo are posted on the World Wide Web Galileo mission home page at http://galileo.jpl.nasa.gov.

  3. Structure and mechanical properties of wet-spun fibers made from natural cellulose nanofibers.

    PubMed

    Iwamoto, Shinichiro; Isogai, Akira; Iwata, Tadahisa

    2011-03-14

    Cellulose nanofibers were prepared by TEMPO-mediated oxidation of wood pulp and tunicate cellulose. The cellulose nanofiber suspension in water was spun into an acetone coagulation bath. The spinning rate was varied from 0.1 to 100 m/min to align the nanofibers to the spun fibers. The fibers spun from the wood nanofibers had a hollow structure at spinning rates of >10 m/min, whereas the fibers spun from tunicate nanofibers were porous. Wide-angle X-ray diffraction analysis revealed that the wood and tunicate nanofibers were aligned to the fiber direction of the spun fibers at higher spinning rates. The wood spun fibers at 100 m/min had a Young's modulus of 23.6 GPa, tensile strength of 321 MPa, and elongation at break of 2.2%. The Young's modulus of the wood spun fibers increased with an increase in the spinning rate because of the nanofiber orientation effect. PMID:21302950

  4. Estimating dome seeing for LSST

    NASA Astrophysics Data System (ADS)

    Sebag, Jacques; Vogiatzis, Konstantinos

    2014-08-01

    Begin Dome seeing is a critical effect influencing the optical performance of ground based telescopes. A previously reported combination of Computational Fluid Dynamics (CFD) and optical simulations to model dome seeing was implemented for the latest LSST enclosure geometry. To this end, high spatial resolution thermal unsteady CFD simulations were performed for three different telescope zenith angles and four azimuth angles. These simulations generate time records of refractive index values along the optical path, which are post-processed to estimate the image degradation due to dome seeing. This method allows us to derive the distribution of seeing contribution along the different optical path segments that composed the overall light path between the entrance of the dome up to the LSST science camera. These results are used to recognize potential problems and to guide the observatory design. In this paper, the modeling estimates are reviewed and assessed relative to the corresponding performance allocation, and combined with other simulator outputs to model the dome seeing impact during LSST operations.

  5. Growth of intra-caldera lava domes controlled by various modes of caldera collapse, the Štiavnica volcano-plutonic complex, Western Carpathians

    NASA Astrophysics Data System (ADS)

    Tomek, Filip; Žák, Jiří; Holub, František V.; Chlupáčová, Marta; Verner, Kryštof

    2016-02-01

    The Štiavnica volcano-plutonic complex is an erosional relic of Miocene caldera-stratovolcano in the Western Carpathians. The complex exposes a vertical section from the volcano basement through subvolcanic intrusions and a ring fault to volcanic edifice, comprising mostly andesitic lava flows and domes. This paper examines internal structure, magnetic fabric as derived from the anisotropy of magnetic susceptibility (AMS), and emplacement dynamics of three intra-caldera andesite domes (referred to as Domes 1-3) located near the presumed ring fault. Magnetic fabrics, carried by multi-domain titanomagnetite and titanomaghemite, are interpreted as recording various mechanisms of dome growth controlled by active caldera collapse. Dome 1 is explained as a lava coulée, fed by conduits located along the ring fault, with a long lava outflow down the sloping caldera floor. Dome 2 represents an elongated, ring fault-parallel dome wherein the lava flowed a short distance over a flat floor. Dome 3 is interpreted as a composite dome fed from multiple linear fissures opened at a high angle to the ring fault. Subsequently, the dome was intruded by ring fault-parallel dikes that may have potentially fed overlying, now largely eroded lava domes and flows. Finally, we suggest that all domes formed during collapse of the Štiavnica caldera and the various mechanisms of their growth reflect different stages of the caldera evolution from piston (Dome 2) through trap-door (Dome 1) to piecemeal (Dome 3).

  6. Phase delay of polarisation modes in elastically twisted spun fibres

    SciTech Connect

    Morshnev, Sergey K; Chamorovsky, Yury K; Vorob'ev, Igor' L

    2011-05-31

    The evolution of the phase delay between linearly polarised orthogonal modes in a spun fibre elastically twisted around its axis has been studied experimentally and theoretically using a model for a helical structure of the built-in linear birefringence axes. The phase delay is a sinusoidal function of elastic twist angle, with an amplitude and period dependent on fibre parameters: spin pitch and built-in linear birefringence beat length. It is shown that, at a known spin pitch, phase delay versus elastic twist angle data can be used to determine the beat length of built-in linear birefringence in the range 0.01 to 100 mm. The theoretical analysis results are supported by experimental data for conventional and microstructured spun fibres. (fibre optics)

  7. Thermal design of the Galileo spun and despun science

    NASA Technical Reports Server (NTRS)

    Greenfield, M.; Reeve, R.; Stultz, J.; Wu, P.

    1989-01-01

    The delay in the launching of the Galileo spacecraft, which was to be launched aboard the Space Shuttle Atlantis, caused by the Challenger accident resulted in a decrease in the Radioisotope Thermoelectric Generator (RTG) power. A change to the Inertial Upper Stage from the more powerful Centaur G-Prime resulted in a trajectory that requires gravity assists, once by Venus and twice by earth. The resulting peak solar intensity of this roundabout trajectory is more than twice the previous design value for the direct trajectory. The resulting changes in solar intensity range and the RTG power output were substantial and forced major thermal design changes. This paper discusses the thermal design and redesign of the Galileo Spun and Despun sciences. Data are presented on the allowable temperatures for the Spun and Despun sciences, the energy balance calculated for the Despun science, and the Despun science test results.

  8. Effects of Ag additions on melt-spun RE2Fe14B microstructure and texture

    SciTech Connect

    Oster, N.T.; Cavanaugh, D.T.; Dennis, K.W.; Kramer, M.J.; McCallum, R.W.; Anderson, I.E.

    2012-03-07

    Control of microstructure and texture is of critical importance in forming rare earth (RE)-iron-boron particulate suitable for anisotropic polymer-bonded permanent magnets and anisotropic sintered permanent magnets. In this study, the selected approach to controlling grain size, while maintaining texture, is through stabilization and refinement of directional growth in melt-spun ribbons. Varying concentrations of Ag were added to melt-spun ribbons of composition (Y{sub 0.55}Nd{sub 0.45}){sub 2.2}Fe{sub 14}B{sub 1.1}. Effects on microstructure and texture were observed through scanning electron microscopy (SEM) and x-ray diffraction (XRD). It was determined that Ag stabilized columnar growth (compared to alloys with no Ag added) with additions as small as 0.3 at. %, but the Ag also produced a unique texture in the ribbons. In RE-Fe-B ribbons without Ag, strong <001> texture is observed at the free surface and a mechanism has been established. In all Ag-containing ribbons, the observed texture is canted to both the c- and a-axes, but the mechanism remains unclear.

  9. Effects of Ag additions on melt-spun RE2Fe14B microstructure and texture

    SciTech Connect

    Oster, N.T.; Cavanaugh, D.T.; Dennis, K.W.; Kramer, Matthew; McCallum, R.W.; Anderson, Iver

    2012-03-07

    Control of microstructure and texture is of critical importance in forming rare earth (RE)-iron-boron particulate suitable for anisotropic polymer-bonded permanent magnets and anisotropic sintered permanent magnets. In this study, the selected approach to controlling grain size, while maintaining texture, is through stabilization and refinement of directional growth in melt-spun ribbons. Varying concentrations of Ag were added to melt-spun ribbons of composition (Y0.55Nd0.45)2.2Fe14B1.1. Effects on microstructure and texture were observed through scanning electron microscopy (SEM) and x-ray diffraction (XRD). It was determined that Ag stabilized columnar growth (compared to alloys with no Ag added) with additions as small as 0.3 at. %, but the Ag also produced a unique texture in the ribbons. In RE-Fe-B ribbons without Ag, strong <00l> texture is observed at the free surface and a mechanism has been established. In all Ag-containing ribbons, the observed texture is canted to both the c- and a-axes, but the mechanism remains unclear.

  10. 'Heat Dome' Heats Up United States

    MedlinePlus

    ... news/fullstory_160028.html 'Heat Dome' Heats Up United States Much of the country to be under ... As a massive "heat dome" stretches across the United States this week, sending temperatures and humidity levels ...

  11. The lunar Gruithuisen silicic extrusive domes: Topographic configuration, morphology, ages, and internal structure

    NASA Astrophysics Data System (ADS)

    Ivanov, M. A.; Head, J. W.; Bystrov, A.

    2016-07-01

    The Gruithuisen domes, situated on the western portion of the Imbrium basin rim, form three tall mountains (NW, Gamma, Delta) totaling ∼780 km3 in volume. The shapes of the domes are significantly different from that of mare-type domes elsewhere on the Moon. We use data from the Lunar Reconnaissance Orbiter (LRO) and Kaguya missions (LRO Lunar Orbiter Laser Altimeter, Lunar Reconnaissance Orbiter Camera, Diviner, and the Kaguya imager) to characterize the domes and assess models for their origin. The configuration of the domes (steep slopes, up to ∼18-20°) and their specific remote sensing characteristics (strong downturn in the UV, and results from the M3 and Diviner instruments) suggest that the domes formed by eruptions of highly viscous lava. The estimated surface volumes of the domes vary from ∼20 km3 (NW dome) to ∼290 km3 (Gamma dome) to ∼470 km3 (Delta dome). The domes occur on the portion of the Imbrium basin rim that is overlain by ejecta from the post-Imbrium Iridum crater. In some areas, relatively high albedo smooth volcanic plains are seen within the Iridum ejecta near the Gruithuisen domes, and low albedo mare deposits surround and embay the domes and Iridum crater. Dating of different units and features by crater counts indicates that impact melts from the Iridum basin are ∼3.9 Ga old, the domes Gamma and Delta are ∼3.8 Ga, and the ages of the plains near the domes vary from ∼2.3 to ∼3.6 Ga. A fresh impact crater exposes the internal structure of the Gamma dome. The most prominent features on the wall of the crater are rough, blocky layers that are typical of volcanic plains in the highlands and maria around the domes. The layers are interleaved with fine-grained materials of higher and lower albedo and the visible orientation of the layers changes over short (a few hundred meters) distances. These characteristics of the internal structure of the dome are consistent with eruptions of high viscosity lava (rough layers) that

  12. Emplacement of the final lava dome of the 2009 eruption of Redoubt Volcano, Alaska

    NASA Astrophysics Data System (ADS)

    Bull, Katharine F.; Anderson, Steven W.; Diefenbach, Angela K.; Wessels, Rick L.; Henton, Sarah M.

    2013-06-01

    After more than 8 months of precursory activity and over 20 explosions in 12 days, Redoubt Volcano, Alaska began to extrude the fourth and final lava dome of the 2009 eruption on April 4. By July 1 the dome had filled the pre-2009 summit crater and ceased to grow. By means of analysis and annotations of time-lapse webcam imagery, oblique-image photogrammetry techniques and capture and analysis of forward-looking infrared (FLIR) images, we tracked the volume, textural, effusive-style and temperature changes in near-real time over the entire growth period of the dome. The first month of growth (April 4-May 4) produced blocky intermediate- to high-silica andesite lava (59-62.3 wt.% SiO2) that initially formed a round dome, expanding by endogenous growth, breaking the surface crust in radial fractures and annealing them with warmer, fresh lava. On or around May 1, more finely fragmented and scoriaceous andesite lava (59.8-62.2 wt.% SiO2) began to appear at the top of the dome coincident with increased seismicity and gas emissions. The more scoriaceous lava spread radially over the dome surface, while the dome continued to expand from endogenous growth and blocky lava was exposed on the margins and south side of the dome. By mid-June the upper scoriaceous lava had covered 36% of the dome surface area. Vesicularity of the upper scoriaceous lava range from 55 to 66%, some of the highest vesicularity measurements recorded from a lava dome. We suggest that the stability of the final lava dome primarily resulted from sufficient fracturing and clearing of the conduit by preceding explosions that allowed efficient degassing of the magma during effusion. The dome was thus able to grow until it was large enough to exceed the magmastatic pressure in the chamber, effectively shutting off the eruption.

  13. A detailed gravity study of the Chattolanee Baltimore Gneiss Dome, Maryland, U.S.A.

    NASA Astrophysics Data System (ADS)

    Kodama, Kenneth P.; Chapin, David A.

    1984-05-01

    A detailed gravity survey over the Chattolanee Baltimore Gneiss Dome in the Maryland Piedmont suggests that the dome is an arched recumbent fold. The Baltimore Gneiss, which cores the dome, has a negative density contrast with the surrounding Cambro-Ordovician marbles and schists and is coincident with a large minimum in the simple Bouguer gravity. Three north-south profiles, which cut across the east-west-trending surface exposure of the dome were modeled two-dimensionally. The models suggest that the Baltimore Gneiss is thickest and tightly folded in an inverted V shape to the east and thinner and broadly arched to the west. It is also possible to fit the gravity data with a mushroom-shaped body at the easternmost profile, which could suggest a diapiric origin for the dome, but this interpretation is not favored based on geological arguments. The Baltimore Mafic Complex, located to the south of the Chattolanee Dome, can be modeled as an approximately 1 km thick slab with a subhorizontal base, suggesting that it is a thrust sheet. By analogy with the Phoenix Baltimore Gneiss Dome, mapped by Crowley [2], the Cambro-Ordovician sediments surrounding the Chattolanee Dome may also be involved in the recumbent folding which would suggest that the dome was formed during the Ordovician Taconic orogeny.

  14. Upheaval Dome, An Analogue Site for Gale Center

    NASA Technical Reports Server (NTRS)

    Conrad, P. G.; Eignebrode, J. L.

    2011-01-01

    We propose Upheaval Dome in southeastern Utah as an impact analogue site on Earth to Mars Science Laboratory candidate landing site Gale Crater. The genesis of Upheaval Dome was a mystery for some time--originally thought to be a salt dome. The 5 km crater was discovered to possess shocked quartz and other shock metamorphic features just a few years ago, compelling evidence that the crater was formed by impact, although the structural geology caused Shoemaker and Herkenhoff to speculate an impact origin some 25 years earlier. The lithology of the crater is sedimentary. The oldest rocks are exposed in the center of the dome, upper Permian sandstones, and progressively younger units are well exposed moving outward from the center. These are Triassic sandstones, siltstones and shales, which are intruded by clastic dikes. There are also other clay-rich strata down section, as is the case with Gale Crater. There is significant deformation in the center of the crater, with folding and steeply tilted beds, unlike the surrounding Canyonlands area, which is relatively undeformed. The rock units are well exposed at Upheaval Dome, and there are shatter cones, impactite fragments, shocked quartz grains and melt rocks present. The mineral shock features suggest that the grains were subjected to dynamic pressures> 10 GPa.

  15. Folding retractable protective dome for space vehicle equipment

    NASA Technical Reports Server (NTRS)

    Clark, Paul R. (Inventor); Messinger, Ross H. (Inventor)

    2008-01-01

    A folding, retractable dome for protecting a feature, such as a docking mechanism, a hatch or other equipment at an exterior surface of a space vehicle, includes a plurality of arcuate ribs, each having opposite ends respectively pinioned at opposite sides of the feature at the surface of the vehicle for rotational movement about an axis of rotation extending through the opposite ends and through an arcuate path of revolution extending over the feature, and a flexible cover attached to each of the ribs such that, in a deployed configuration of the dome, in which adjacent ribs are rotated apart from each other at a maximum relative angle therebetween, the cover is stretched generally tangentially between the adjacent ribs to form a generally arcuate shield over the feature, and in a retracted position of the dome, in which adjacent ribs are rotated together at a minimum relative angle therebetween, the cover is collapsed to define folded pleats between the adjacent ribs.

  16. Foldable dome climate measurements and thermal properties

    NASA Astrophysics Data System (ADS)

    Sliepen, Guus; Jägers, Aswin P. L.; Hammerschlag, Robert H.; Bettonvil, Felix C. M.

    2010-07-01

    As part of a larger project for measuring various aspects of foldable domes in the context of EST and with support of the Dutch Technology Foundation STW, we have collected over a year of continuous temperature and humidity measurements, both inside and outside the domes of the Dutch Open Telescope (DOT) on La Palma5 and the GREGOR telescope on Tenerife.6 In addition, we have measured the wind field around each dome. Although the structure of both domes is similar, the DOT dome has a single layer of cloth, and is situated on top of an open tower. In contrast, the GREGOR dome has a double layer of cloth, and is situated on top of a tower-shaped building. These differences result in large differences in temperature and humidity insulation when the dome is closed. We will present the changes in temperature and humidity one can expect for each dome within one day, and the statistics for the variations throughout a year. In addition, we will show that the main advantage of a foldable dome is the near instantaneous equilibration of the air inside the volume originally enclosed by the dome and that of the environment outside the dome. This property allows one to operate a telescope without needing expensive air conditioning and dome skin temperature control in order to limit dome and shell seeing effects. The measurements give also information about the weather fluctuations at the sites of the domes. It was observed that on small time scales the temperature fluctuations are significantly greater during the day than during the night.

  17. Thread-like supercapacitors based on one-step spun nanocomposite yarns.

    PubMed

    Meng, Qinghai; Wang, Kai; Guo, Wei; Fang, Jin; Wei, Zhixiang; She, Xilin

    2014-08-13

    Thread-like electronic devices have attracted great interest because of their potential applications in wearable electronics. To produce high-performance, thread-like supercapacitors, a mixture of stable dispersions of single-walled carbon nanotubes and conducting polyaniline nanowires are prepared. Then, the mixture is spun into flexible yarns with a polyvinyl alcohol outer sheath by a one-step spinning process. The composite yarns show excellent mechanical properties and high electrical conductivities after sufficient washing to remove surfactants. After applying a further coating layer of gel electrolyte, two flexible yarns are twisted together to form a thread-like supercapacitor. The supercapacitor based on these two yarns (SWCNTs and PAniNWs) possesses a much higher specific capacitance than that based only on pure SWCNTs yarns, making it an ideal energy-storage device for wearable electronics. PMID:24729355

  18. Programmable shape transformation of elastic spherical domes.

    PubMed

    Abdullah, Arif M; Braun, Paul V; Hsia, K Jimmy

    2016-07-20

    We investigate mismatch strain driven programmable shape transformation of spherical domes and report the effects of different geometric and structural characteristics on dome behavior in response to applied mismatch strain. We envision a bilayer dome design where the differential swelling of the inner layer with respect to the passive outer layer in response to changes in dome surroundings (such as the introduction of an organic solvent) introduces mismatch strain within the bilayer system and causes dome shape transformation. Finite element analysis reveals that, in addition to snap-through, spherical domes undergo bifurcation buckling and eventually gradual bending to morph into cylinders with increasing mismatch strain. Besides demonstrating how the snap-through energy barrier depends on the spherical dome shape, our analysis identifies three distinct groups of dome geometries based on their mismatch strain-transformed configuration relationships. Our experiments with polymer-based elastic bilayer domes that exhibit differential swelling in organic solvents qualitatively confirm the finite element predictions. We establish that, in addition to externally applied stimuli (mismatch strain), bilayer spherical dome morphing can be tuned and hence programmed through its geometry and structural characteristics. Incorporation of an elastic instability mechanism such as snap-through within the framework of stimuli-responsive functional devices can improve their response time which is otherwise controlled by diffusion. Hence, our proposed design guidelines can be used to realize deployable, multi-functional, reconfigurable, and therefore, adaptive structures responsive to a diverse set of stimuli across multiple length scales. PMID:27435451

  19. Formation of the giant Shakhdara migmatitic gneiss dome, Pamir, India-Asia collision zone

    NASA Astrophysics Data System (ADS)

    Stübner, Konstanze; Ratschbacher, Lothar; Hacker, Bradley; Dunkl, István; Gloaguen, Richard

    2013-04-01

    Cenozoic gneiss domes comprise one third of the surface exposure of the Pamir Mountains and provide a window into deep crustal processes of the India-Asia collision. The largest of these is the 350 × 90 km Shakhdara-Alichur composite dome of the southern Pamir, Tajikistan and Afghanistan. The Shakhdara and Alichur domes formed by footwall exhumation of two low-angle detachments: In the larger Shakhdara dome the top-to-S South Pamir shear zone (SPSZ) exhumed crust from 30-40 km depth; in the Alichur dome the top-to-N Alichur shear zone exhumed upper crustal rocks. The subdomes are separated by a low-strain horst. Non-coaxial shear in the Shakhdara dome is pervasive over the ~4 km thick SPSZ. The top of the shear zone is preserved at mountain peaks, the base is incised by the Panj gorge, which exposes the 'core' of the dome; total erosion is less than 4 km throughout most of the dome. We use a comprehensive geo-thermochronologic dataset of titanite, monazite, and zircon U/Th-Pb, mica Rb-Sr and 40Ar/39Ar, zircon and apatite fission track, and zircon (U-Th)/He ages to constrain the exhumation history of the southern Pamir domes. Doming started at ~21 Ma by crustal buckling and activation of a top-to-N normal shear zone (Gunt shear zone) along the northern rim of the Shakhdara dome, resulting in exhumation and cooling. The bulk of the exhumation was accomplished by northward extrusion of the SPSZ footwall, which was active from ~18-15 Ma to ~2 Ma; exhumation rates were 1-3 mm/yr. Erosion rates during and after the end of doming were 0.3-0.5 mm/yr within the domes and 0.1-0.3 mm/yr in the horst and in the SE Pamir plateau; incision rates of the major drainages were up to 1.0 mm/yr. Doming by footwall exhumation of the SPSZ resulted in up to 90 km N-S extension, coeval with ongoing N-S convergence between India and Asia. Extension opposes shortening along and above the reactivated Rushan-Pshart suture zone, a wide fold-thrust belt north of the Shakhdara-Alichur domes

  20. Magnetic properties of Sm{sub 5}Fe{sub 17} melt-spun ribbon

    SciTech Connect

    Saito, Tetsuji

    2007-05-01

    The relationship between the structures and magnetic properties of Sm{sub 5}Fe{sub 17} melt-spun ribbons was studied. The melt-spun ribbons obtained by annealing of amorphous Sm{sub 5}Fe{sub 17} melt-spun ribbon consisted of the Sm{sub 5}Fe{sub 17} phase when annealed at 973 K for 0 h (i.e., when the furnace was immediately turned off after heating) or the Sm{sub 5}Fe{sub 17} phase together with a small amount of the SmFe{sub 12} phase when produced by annealing at 973 K for 1 h. The coercivity of the annealed Sm-Fe melt-spun ribbons was strongly dependent on the annealing conditions. The maximum coercivity of the annealed Sm{sub 5}Fe{sub 17} melt-spun ribbons exceeded 36 kOe.

  1. On the temperature dependent magnetic properties of as-spun Mn-Bi ribbons

    NASA Astrophysics Data System (ADS)

    Kavita, S.; Seelam, U. M. R.; Prabhu, D.; Gopalan, R.

    2015-03-01

    The structural and magnetic properties of melt-spun ribbons with nominal composition of Mn55Bi45 were investigated using X-ray diffraction, transmission electron microscopy and magnetometer measurements. A large coercivity (Hc) of 0.8 T was observed in the as-spun ribbons. Microstructure reveals the presence of Mn-Bi nanoparticles in the as-spun ribbons. Coercivity was found to increase with increasing temperature with a maximum coercivity of 1.4 T at T=503 K in the as-spun ribbons. Heat treatment of the as-spun ribbons resulted in the increase of LTP MnBi phase. Spin reorientation transition (TSR) was observed around 100 K.

  2. Numerical modelling of lithospheric extension: doming vs. thermal condition

    NASA Astrophysics Data System (ADS)

    Schenker, Filippo Luca; Gerya, Taras; Kaus, Boris; Burg, Jean-Pierre

    2010-05-01

    Structural aspects of extensional doming have been modelled numerically using simplified 2D visco-plastic models (e.g. Huismans et al. 2005, Buiter et al. 2008) concentrating mainly on symmetric/asymmetric doming, fault tectonics and deformation of domes and surrounding rocks. Recent works focus their attention to the influence of geotherms on the rheology (Tirel et al. 2008), even taking into account melting (Rey et al., 2009). However, thermal aspects remain difficult to compute because of the coupled interaction between mechanical forces and temperature. This coupling is fundamental, because it provides a link between modelling and thermochronometry. Indeed, cooling ages of extensional dome flanks can constrain time, size, and patterns of metamorphic overprints simulated in thermo-mechanical models. We treat mechanical and thermal aspects together (including modelling of metamorphic P-T-time paths of crustal rocks), using a visco-elasto-plastic rheology in a four layer setup (upper crust, lower crust, lithospheric mantle and asthenospheric mantle). The asthenospheric mantle is considered in order to predict the bending effect of the lithosphere. We employed I2ELVIS, a numerical 2D computer code designed for conservative finite differences method. The model domain is 300 km wide and 160 km deep. We observed two modes of dome development and geometry, depending on first order parameters such as temperature at the Moho and thickness of the crust: (i) Lower crustal doming: with a hot Moho (TMOHO > 700 °C) and/or a thick crust, strain is localized in the upper crust and distributed in the mantle. At these conditions partial melting in the lower crust forms the core of the dome and maintains a flat Moho. (ii) Asthenospheric-triggered doming: with a cold Moho (TMOHO < 700 °C), strain is distributed in the crust and localized in the lithospheric mantle, which allows upwelling of the asthenosphere. The migmatite "core complexes" develop after the upwelling of the

  3. The hydrothermal alteration of cooling lava domes

    NASA Astrophysics Data System (ADS)

    Ball, Jessica L.; Stauffer, Philip H.; Calder, Eliza S.; Valentine, Greg A.

    2015-12-01

    Hydrothermal alteration is a recognized cause of volcanic instability and edifice collapse, including that of lava domes or dome complexes. Alteration by percolating fluids transforms primary minerals in dome lavas to weaker secondary products such as clay minerals; moreover, secondary mineral precipitation can affect the porosity and permeability of dome lithologies. The location and intensity of alteration in a dome depend heavily on fluid pathways and availability in conjunction with heat supply. Here we investigate postemplacement lava dome weakening by hydrothermal alteration using a finite element numerical model of water migration in simplified dome geometries. This is combined with the rock alteration index (RAI) to predict zones of alteration and secondary mineral precipitation. Our results show that alteration potential is highest at the interface between the hot core of a lava dome and its clastic talus carapace. The longest lived alteration potential fields occur in domes with persistent heat sources and permeabilities that allow sufficient infiltration of water for alteration processes, but not so much that domes cool quickly. This leads us to conclude that alteration-induced collapses are most likely to be shallow seated and originate in the talus or talus/core interface in domes which have a sustained supply of magmatic heat. Mineral precipitation at these zones of permeability contrast could create barriers to fluid flow, potentially causing gas pressurization which might promote deeper seated and larger volume collapses. This study contributes to our knowledge of how hydrothermal alteration can affect lava domes and provides constraints on potential sites for alteration-related collapses, which can be used to target hazard monitoring.

  4. Solidification process in melt spun Nd-Fe-B type magnets

    SciTech Connect

    Li, C.

    1998-02-23

    A generalized solidification model has been developed based on a systematic investigation on the microstructure of melt spun Nd-Fe-B alloys. Melt spinning was conducted on initial stoichiometric and TiC added Nd{sub 2}Fe{sub 14}B (2-14-1) compositions to produce under, optimally and over quenched microstructures. Microstructural characterization was carried out by TEM, SEM, Optical microscopy, XRD, DTA, VSM and DC SQUID techniques. By taking the dendritic breakup during recalescence into consideration, this generalized model has successfully explained the solidification process of the melt spun Nd-Fe-B alloys. Challenging the conventional homogeneous nucleation models, the new model explains the fine and uniform equiaxed 2-14-1 microstructure in optimally quenched ribbons as a result of the breakup of the 2-14-1 dendrites which nucleate heterogeneously from the wheel surface and grow dendritically across the ribbon thickness due to the recalescence. Besides this dendritic breakup feature, the under quenched microstructure is further featured with another growth front starting with the primary solidification of Fe phase near the free side, which results in a coarsely grained microstructure with Fe dendritic inclusions and overall variation in microstructure across the ribbon thickness. In addition, because a epitaxy exists between the Fe phase and the 2-14-1, the so-formed coarse 2-14-1 grains may be textured. C-axis texturing was observed in under quenched ribbons. As a constraint to solidification models in this system, the cause and characteristics of this phenomenon has been studied in detail to test the authors proposed model, and agreement has been found. An extension has also been made to understand the solidification process when TiC is added, which suggests that Ti and C slow down the growth front of both Fe and 2-14-1 phase.

  5. Geology of the Upheaval Dome impact structure, southeast Utah

    USGS Publications Warehouse

    Kriens, B.J.; Shoemaker, E.M.; Herkenhoff, K. E.

    1999-01-01

    Two vastly different phenomena, impact and salt diapirism, have been proposed for the origin of Upheaval Dome, a spectacular scenic feature in southeast Utah. Detailed geologic mapping and seismic refraction data indicate that the dome originated by collapse of a transient cavity formed by impact. Evidence is as follows: (1) sedimentary strata in the center of the structure are pervasively imbricated by top-toward-the-center thrust faulting and are complexly folded as well; (2) top-toward-the-center normal faults are found at the perimeter of the structure; (3) clastic dikes are widespread; (4) the top of the underlying salt horizon is at least 500 m below the surface at the center of the dome, and there are no exposures of salt or associated rocks of the Paradox Formation in the dome to support the possibility that a salt diapir has ascended through it; and (5) planar microstructures in quartz grains, fantailed fracture surfaces (shatter surfaces), and rare shatter cones are present near the center of the structure. We show that the dome formed mainly by centerward motion of rock units along listric faults. Outcrop-scale folding and upturning of beds, especially common in the center, are largely a consequence of this motion. We have also detected some centerward motion of fault-bounded wedges resulting from displacements on subhorizontal faults that conjoin and die out within horizontal bedding near the perimeter of the structure. The observed deformation corresponds to the central uplift and the encircling ring structural depression seen in complex impact craters. Copyright 1999 by the American Geophysical Union.

  6. Use of Spun optical fibres in current sensors

    SciTech Connect

    Gubin, Vladimir P; Isaev, Victor A; Morshnev, Sergey K; Sazonov, Aleksandr I; Starostin, Nikolay I; Chamorovsky, Yury K; Oussov, Aleksey I

    2006-03-31

    The polarisation properties of a Spun optical fibre are studied in connection with their applications in fibreoptic current sensors based on the Faraday effect. A model of this fibre is proposed which represents it as an anisotropic medium with the spiral structure of the fast and slow birefringence axes. A sensor is developed based on an all-fibre low-coherence linear interferometer with a threshold sensitivity of 70 mA Hz{sup -1/2}, a maximum measured current of 3000 A, and a scale-factor reproducibility of {+-}0.6%. It is found that for a given diameter of the fibre contour, the normalised sensitivity is independent of the fibre length. The experimental results confirm the theory. (laser applications and other topics in quantum electronics)

  7. Dome cities for extreme environments

    NASA Technical Reports Server (NTRS)

    Leonard, Raymond S.; Schwartz, Milton

    1992-01-01

    Extreme environments whether they be the frigid nights of the polar regions, the burning sands of the desert, or the harsh environment of space pose interesting challenges to the architect, the engineer, and the constructor in their efforts to create habitats for mankind. In space, the goals are to provide radiation protection while also providing an aesthetic living environment for long duration missions. Because of the need to provide both radiation protection and options for expansion of base facilities, a unique structural system which separates the radiation protection systems from the pressure envelope of the habitats was created. The system uses cable networks in a tensioned structural system, which supports the lunar regolith used for shielding above the facilities. The system is modular, easily expandable, and simple to construct. Additional innovations include the use of rock melting perpetrators for piles and anchoring deadmen, and various sized craters to provide side shielding. The reflective properties of the fabric used in the membrane are utilized to provide diffuse illumination. The use of craters along with the suspended shielding allows the dome to be utilized in fashions similar to those proposed by various designers unaware of the Moon's hostile radiation environment. Additional topics addressed deal with construction techniques for large domes, i.e., on the order of 100's to 1000's of meters, thermal control, the integration of tertiary water treatment schemes with architectural design, human factors, and its implications for the design of habitats for long term use in extreme environments.

  8. Dome cities for extreme environments

    NASA Astrophysics Data System (ADS)

    Leonard, Raymond S.; Schwartz, Milton

    Extreme environments whether they be the frigid nights of the polar regions, the burning sands of the desert, or the harsh environment of space pose interesting challenges to the architect, the engineer, and the constructor in their efforts to create habitats for mankind. In space, the goals are to provide radiation protection while also providing an aesthetic living environment for long duration missions. Because of the need to provide both radiation protection and options for expansion of base facilities, a unique structural system which separates the radiation protection systems from the pressure envelope of the habitats was created. The system uses cable networks in a tensioned structural system, which supports the lunar regolith used for shielding above the facilities. The system is modular, easily expandable, and simple to construct. Additional innovations include the use of rock melting perpetrators for piles and anchoring deadmen, and various sized craters to provide side shielding. The reflective properties of the fabric used in the membrane are utilized to provide diffuse illumination. The use of craters along with the suspended shielding allows the dome to be utilized in fashions similar to those proposed by various designers unaware of the Moon's hostile radiation environment. Additional topics addressed deal with construction techniques for large domes, i.e., on the order of 100's to 1000's of meters, thermal control, the integration of tertiary water treatment schemes with architectural design, human factors, and its implications for the design of habitats for long term use in extreme environments.

  9. Temperature dependences of phase and group birefringence in spun fibres

    SciTech Connect

    Morshnev, S K; Gubin, V P; Przhiyalkovsky, Y V; Starostin, N I

    2013-12-31

    We consider the application of the spectral method for measuring the beat length of birefringence in spun fibre. We have found that the beat length measured in spun fibres is the geometric mean of phase and group birefringence beat lengths. Temperature measurements of beat lengths and shifts of the entire spectrum as a whole make it possible to separate types of birefringence and to determine their dispersion. We have performed an experiment on a spun fibre and a linear polarisation maintaining fibre, drawn from the same preform. The experimental results confirm the theory. (fiber and integrated optics)

  10. A history of semi-active laser dome and window materials

    NASA Astrophysics Data System (ADS)

    Sullivan, Roger M.

    2014-05-01

    Semi-Active Laser (SAL) guidance systems were developed starting in the mid-1960's and today form an important class of precision guided weapons. The laser wavelengths generally fall in the short wave infrared region of the spectrum. Relative to passive, image based, infrared seekers the optical demands placed on the domes or windows of SAL seekers is very modest, allowing the use of low cost, easily manufactured materials, such as polycarbonate. This paper will examine the transition of SAL window and dome science and technology from the laboratory to battlefield, with special emphasis on the story of polycarbonate domes.

  11. Environmental assessment: Richton Dome site, Mississippi

    SciTech Connect

    none,

    1986-05-01

    In February 1983, the US Department of Energy (DOE) identified the Richton Dome site in Mississippi as one of the nine potentially acceptable sites for a mined geologic repository for spent nuclear fuel and high-level radioactive waste. To determine their suitability, the Richton Dome site and the eight other potentially acceptable sites have been evaluated in accordance with the DOE's General Guidelines for the Recommendation of Sites for the Nuclear Waste Repositories. These evaluations were reported in draft environmental assessments (EAs), which were issued for public review and comment. After considering the comments received on the draft EAs, the DOE prepared the final EAs. The site is in the Gulf interior region, which is one of five distinct geohydrologic settings considered for the first repository. This setting contains two other potentially acceptable sites--the Cypress Creek Dome site in Mississippi and the Vacherie Dome site in Louisiana. Although the Cypress Creek Dome and the Vacherie Dome sites are suitable for site characterization, the DOE has concluded that the Richton Dome site is the preferred site in the Gulf interior region. On the basis of the evaluations reported in this EA, the DOE has found that the Richton Dome site is not disqualified under the guidelines.

  12. Environmental assessment: Richton Dome Site, Mississippi

    SciTech Connect

    none,

    1986-05-01

    In February 1983, the US Department of Energy (DOE) identified the Richton Dome site in Mississippi as one of the nine potentially acceptable sites for a mined geologic repository for spent nuclear fuel and high-level radioactive waste. To determine their suitability, the Richton Dome site and the eight other potentially acceptable sites have been evaluated in accordance with the DOE's General Guidelines for the Recommendation of Sites for the Nuclear Waste Repositories. These evaluations were reported in draft environmental assessments (EAs), which were issued for public review and comment. After considering the comments received on the draft EAs, the DOE prepared the final EAs. The site is in the Gulf interior region, which is one of five distinct geohydrologic settings considered for the first repository. This setting contains two other potentially acceptable sites--the Cypress Creek Dome site in Mississippi and the Vacherie Dome site in Louisiana. Although the Cypress Creek Dome and the Vacherie Dome sites are suitable for site characterization, the DOE has concluded that the Richton Dome site is the preferred site in the Gulf interior region. On the basis of the evaluations reported in this EA, the DOE has found that the Richton Dome site is not disqualified under the guidelines.

  13. Submarine Analogs to Venusian Pancake Domes

    NASA Technical Reports Server (NTRS)

    Bridges, Nathan T.

    1995-01-01

    The morphology and dimensions of the large diameter, steep-sided, flat-topped "pancake domes" on Venus make them unlike any type of terrestrial subaerial volcano. Comparisons between images of Hawaiian seamounts and pancake domes show similarities in shapes and secondary features. The morphometry of pancake domes is closer to that of Pacific seamounts than subaerial lava domes. Considering both morphology and morphometry, seamounts seem a better analog to the pancake domes. The control of volatile exsolution by pressure on Venus and the seafloor can cause lavas to have similar viscosities and densities, although the latter will be counteracted by high buoyancy underwater. However, analogous effects of the Venusian and seafloor alone are probably not sufficient to produce similar volcanoes. Rather, Venusian lavas of various compositions may behave like basalt on the seafloor if appropriate rates and modes of extrusion and planetary thermal structure are also considered.

  14. Key variables influencing patterns of lava dome growth and collapse

    NASA Astrophysics Data System (ADS)

    Husain, T.; Elsworth, D.; Voight, B.; Mattioli, G. S.; Jansma, P. E.

    2013-12-01

    Lava domes are conical structures that grow by the infusion of viscous silicic or intermediate composition magma from a central volcanic conduit. Dome growth can be characterized by repeated cycles of growth punctuated by collapse, as the structure becomes oversized for its composite strength. Within these cycles, deformation ranges from slow long term deformation to sudden deep-seated collapses. Collapses may range from small raveling failures to voluminous and fast-moving pyroclastic flows with rapid and long-downslope-reach from the edifice. Infusion rate and magma rheology together with crystallization temperature and volatile content govern the spatial distribution of strength in the structure. Solidification, driven by degassing-induced crystallization of magma leads to the formation of a continuously evolving frictional talus as a hard outer shell. This shell encapsulates the cohesion-dominated soft ductile core. Here we explore the mechanics of lava dome growth and failure using a two-dimensional particle-dynamics model. This meshless model follows the natural evolution of a brittle carapace formed by loss of volatiles and rheological stiffening and avoids difficulties of hour-glassing and mesh-entangelment typical in meshed models. We test the fidelity of the model against existing experimental and observational models of lava dome growth. The particle-dynamics model follows the natural development of dome growth and collapse which is infeasible using simple analytical models. The model provides insight into the triggers that lead to the transition in collapse mechasnism from shallow flank collapse to deep seated sector collapse. Increase in material stiffness due to decrease in infusion rate results in the transition of growth pattern from endogenous to exogenous. The material stiffness and strength are strongly controlled by the magma infusion rate. Increase in infusion rate decreases the time available for degassing induced crystallization leading to a

  15. Formation of dome and basin structures: Results from scaled experiments using non-linear rock analogues

    NASA Astrophysics Data System (ADS)

    Zulauf, J.; Zulauf, G.; Zanella, F.

    2016-09-01

    Dome and basin folds are structures with circular or slightly elongate outcrop patterns, which can form during single- and polyphase deformation in various tectonic settings. We used power-law viscous rock analogues to simulate single-phase dome-and-basin folding of rocks undergoing dislocation creep. The viscosity ratio between a single competent layer and incompetent matrix was 5, and the stress exponent of both materials was 7. The samples underwent layer-parallel shortening under bulk pure constriction. Increasing initial layer thickness resulted in a decrease in the number of domes and basins and an increase in amplitude, A, arc-length, L, wavelength, λ, and layer thickness, Hf. Samples deformed incrementally show progressive development of domes and basins until a strain of eY=Z = -30% is attained. During the dome-and-basin formation the layer thickened permanently, while A, L, and λ increased. A dominant wavelength was not attained. The normalized amplitude (A/λ) increased almost linearly reaching a maximum of 0.12 at eY=Z = -30%. During the last increment of shortening (eY=Z = -30 to -40%) the domes and basins did not further grow, but were overprinted by a second generation of non-cylindrical folds. Most of the geometrical parameters of the previously formed domes and basins behaved stable or decreased during this phase. The normalized arc-length (L/Hf) of domes and basins is significantly higher than that of 2D cylindrical folds. For this reason, the normalized arc length can probably be used to identify domes and basins in the field, even if these structures are not fully exposed in 3D.

  16. Comparison of directly compressed vitamin B12 tablets prepared from micronized rotary-spun microfibers and cast films.

    PubMed

    Sebe, István; Bodai, Zsolt; Eke, Zsuzsanna; Kállai-Szabó, Barnabás; Szabó, Péter; Zelkó, Romána

    2015-01-01

    Fiber-based dosage forms are potential alternatives of conventional dosage forms from the point of the improved extent and rate of drug dissolution. Rotary-spun polymer fibers and cast films were prepared and micronized in order to direct compress after homogenization with tabletting excipients. Particle size distribution of powder mixtures of micronized fibers and films homogenized with tabletting excipients were determined by laser scattering particle size distribution analyzer. Powder rheological behavior of the mixtures containing micronized fibers and cast films was also compared. Positron annihilation lifetime spectroscopy was applied for the microstructural characterization of micronized fibers and films. The water-soluble vitamin B12 release from the compressed tablets was determined. It was confirmed that the rotary spinning method resulted in homogeneous supramolecularly ordered powder mixture, which was successfully compressed after homogenization with conventional tabletting excipients. The obtained directly compressed tablets showed uniform drug release of low variations. The results highlight the novel application of micronized rotary-spun fibers as intermediate for further processing reserving the original favorable powder characteristics of fibrous systems. PMID:25190153

  17. A model for submarine rhyolite dome growth: Ponza Island (central Italy)

    NASA Astrophysics Data System (ADS)

    DeRita, Donatella; Giordano, Guido; Cecili, Alessandro

    2001-07-01

    The Late Pliocene rhyolitic submarine volcanic rocks of Ponza island (Italy) can be interpreted as the subaqueous equivalent of subaerial dome complexes in terms of geometry and structure. Three coalescing domes of about 1 km radius and aligned along a NE-trending regional fracture have been identified. The main difference between subaqueous and subaerial lava domes is that in a subaqueous environment, lava is likely to undergo pervasive hyaloclastic brecciation, so that domes are mainly composed of variously brecciated, in situ to clast-rotated hyaloclastite rather than coherent lava. We suggest that the shape and rheologic behaviour through time of submarine domes are closely controlled by the development and thickness of the particulate hyaloclastic carapace, which assumes the role of the solid crust of domes in subaerial environment. The thickness of the hyaloclastic carapace at Ponza is greater than 150 m and emplaced during several different pulses (or eruptions). In the earliest pulses, lava is directly extruded on the seafloor and produces hyaloclastite, the degree of brecciation of which decreases inward to the coherent flow-banded rhyolite lava of the feeder dike. Once the hyaloclastic carapace is formed, further pulses of magma, combined with increase in height of the dome result in a local stress pattern characterised by a vertical σ1≫ σ2= σ3, producing concentric and radial fractures and normal faults. The newly rising magma, shielded by the hyaloclastic carapace, can intrude along these fault and fracture systems and invade previously emplaced but still water-saturated hyaloclastite. This produces the characteristic pattern of dikes observed at Ponza as a series of concentric dikes that are progressively less inclined outward with respect to the dome centre. These late stage dikes in turn produce hyaloclastite at their margins, but generally less fragmented than the embedding hyaloclastite, probably because the ascending magma is better shielded

  18. Unzipped Nanotube Sheet Films Converted from Spun Multi-Walled Carbon Nanotubes by O2 Plasma.

    PubMed

    Jangr, Hoon-Sik; Jeon, Sang Koo; Shim, Dae Seob; Lee, Nam Hee; Nahm, Seung Hoon

    2015-11-01

    Large-scale graphene or carbon nanotube (CNT) films are good candidates for transparent flexible electrodes, and the strong interest in graphene and CNT films has motivated the scalable production of a good-conductivity and an optically transmitting film. Unzipping techniques for converting CNTs to graphene are especially worthy of notice. Here, we performed nanotube unzipping of the spun multi-walled carbon nanotubes (MWCNTs) to produce networked graphene nanoribbon (GNR) sheet films using an 02 plasma etching method, after which we produced the spun MWCNT film by continually pulling MWCNTs down from the vertical well aligned MWCNTs on the substrate. The electrical resistance was slightly decreased and the optical transmittance was significantly increased when the spun MWCNT films were etched for 20 min by O2 plasma of 100 mA. Plasma etching for the optimized time, which does not change the thickness of the spun MWCNT films, improved the electrical resistance and the optical transmittance. PMID:26726645

  19. Observations of dome growth and lava flow development as determined by pixel offsets in photographs of the 2006 Merapi eruption

    NASA Astrophysics Data System (ADS)

    Walter, Thomas R.; Ratdomopurbo, Antonius; Subandriyo, Subandriyo; Aisyah, Nurnaning; Sri Brotopusptio, Kirbani; Salzer, Jacqueline; Lühr, Birger

    2013-04-01

    Viscous domes of explosive volcanoes commonly form by extrusion and are destroyed by collapses of the talus region. Although the growth and development of silicic domes and the associated flow and collapse mechanisms are of vital importance for understanding the occurrence and scale of pyroclastic flows, quantitative measurements of dome deformations are limited. We report on a sequence of photographs taken of a growing and deforming dome. Photographs of Mount Merapi in 2006, taken from similar camera positions, allow a digital image correlation algorithm to be applied to detect and explore the temporal evolution of pixel offsets. The results suggest that the dome underwent deformation in two regions between September and October 2006: (i) dome growth and spreading at the volcano summit and (ii) coulée flow through a narrow canyon. The latter is associated with strain localization and flow acceleration, which indicates that the displacements and flow velocities at silicic domes are governed by the topographic structure into which the flows develop. The downslope motion of the distal parts of the flow and apron slumps continue during episodes of dome extrusion by gravitational spreading. An analysis of the 2006 Merapi dome and coulée displacement also provides insights into processes of the newly established southerly eruption direction, which also controlled the 2010 eruption.

  20. Lunar Gruithuisen and Mairan domes: Rheology and mode of emplacement

    NASA Astrophysics Data System (ADS)

    Wilson, Lionel; Head, James W.

    2003-02-01

    The lunar steep-sided Gruithuisen and Mairan domes are morphologically and spectrally distinctive structures and appear similar to terrestrial extrusive volcanic features characterized by viscous magma. We use the basic morphologic and morphometric characteristics of the domes to estimate the yield strengths (~105 Pa), plastic viscosities (~109 Pa s), and effusion rates (~50 m3/s) of the magmas which formed them. These values are similar to those of terrestrial rhyolites, dacites, and basaltic andesites and support the hypothesis that these domes are an unusual variation of typical highlands and mare compositions. The dikes which formed them are predicted to have had widths of ~50 m and lengths of about 15 km. The magma rise speed implied by this geometry is very low, ~7 × 10-5 m/s, and the Reynolds number of the motion is ~2 × 10-8, implying a completely laminar flow regime. Estimates of emplacement duration range from one to several decades. These new calculations confirm the unusual nature of these features and support previous qualitative suggestions that they were formed from magmas with significantly higher viscosity than those typical of mare basalts.

  1. Pressure Dome for High-Pressure Electrolyzer

    NASA Technical Reports Server (NTRS)

    Norman, Timothy; Schmitt, Edwin

    2012-01-01

    A high-strength, low-weight pressure vessel dome was designed specifically to house a high-pressure [2,000 psi (approx. = 13.8 MPa)] electrolyzer. In operation, the dome is filled with an inert gas pressurized to roughly 100 psi (approx. = 690 kPa) above the high, balanced pressure product oxygen and hydrogen gas streams. The inert gas acts to reduce the clamping load on electrolyzer stack tie bolts since the dome pressure acting axially inward helps offset the outward axial forces from the stack gas pressure. Likewise, radial and circumferential stresses on electrolyzer frames are minimized. Because the dome is operated at a higher pressure than the electrolyzer product gas, any external electrolyzer leak prevents oxygen or hydrogen from leaking into the dome. Instead the affected stack gas stream pressure rises detectably, thereby enabling a system shutdown. All electrical and fluid connections to the stack are made inside the pressure dome and require special plumbing and electrical dome interfaces for this to be accomplished. Further benefits of the dome are that it can act as a containment shield in the unlikely event of a catastrophic failure. Studies indicate that, for a given active area (and hence, cell ID), frame outside diameter must become ever larger to support stresses at higher operating pressures. This can lead to a large footprint and increased costs associated with thicker and/or larger diameter end-plates, tie-rods, and the frames themselves. One solution is to employ rings that fit snugly around the frame. This complicates stack assembly and is sometimes difficult to achieve in practice, as its success is strongly dependent on frame and ring tolerances, gas pressure, and operating temperature. A pressure dome permits an otherwise low-pressure stack to operate at higher pressures without growing the electrolyzer hardware. The pressure dome consists of two machined segments. An O-ring is placed in an O-ring groove in the flange of the bottom

  2. Porous, Water-Resistant Multifilament Yarn Spun from Gelatin.

    PubMed

    Stoessel, Philipp R; Krebs, Urs; Hufenus, Rudolf; Halbeisen, Marcel; Zeltner, Martin; Grass, Robert N; Stark, Wendelin J

    2015-07-13

    Sustainability, renewability, and biodegradability of polymeric material constantly gain in importance. A plausible approach is the recycling of agricultural waste proteins such as keratin, wheat gluten, casein or gelatin. The latter is abundantly available from animal byproducts and may well serve as building block for novel polymeric products. In this work, a procedure for the dry-wet spinning of multifilament gelatin yarns was developed. The process stands out as precipitated gelatin from a ternary mixture (gelatin/solvent/nonsolvent) was spun into porous filaments. About 1000 filaments were twisted into 2-ply yarns with good tenacity (4.7 cN tex(-1)). The gelatin yarns, per se susceptible to water, were cross-linked by different polyfunctional epoxides and examined in terms of free lysyl amino groups and swelling degree in water. Ethylene glycol diglycidyl ether exhibited the highest cross-linking efficiency. Further post-treatments with gaseous formaldehyde and wool grease (lanolin) rendered the gelatin yarns water-resistant, allowing for multiple swelling cycles in water or in detergent solution. However, the swelling caused a decrease in filament porosity from ∼30% to just below 10%. To demonstrate the applicability of gelatin yarn in a consumer good, a gelatin glove with good thermal insulation capacity was fabricated. PMID:26035474

  3. Internal fabric development in complex lava domes

    NASA Astrophysics Data System (ADS)

    Závada, Prokop; Kratinová, Zuzana; Kusbach, Vladimír; Schulmann, Karel

    2009-03-01

    Viscous lava extrusions were modeled using plaster of Paris with admixed magnetite dust which served as a tracer of the internal anisotropy of magnetic susceptibility fabric in model lava domes. Used analogue material showed pseudoplastic behavior and yield strength level proportional to increasing mixing ratio of plaster powder and water. A series of models ranging from simple gravity flows to complex lava domes showing combined endogenous and exogenous growth were created by intrusion of plaster into a sandbox. The similarity of model bodies is compared with natural lava domes on the basis of dynamic scaling analysis. Growth dynamics, exogenous growth and internal fabric development in natural lava domes is critically discussed using the experimental results.

  4. Environmental assessment overview: Richton Dome site, Mississippi

    SciTech Connect

    none,

    1986-05-01

    In February 1983, the US Department of Energy (DOE) identified the Richton Dome site in Mississippi as one of the nine potentially acceptable sites for a mined geologic repository for spent nuclear fuel and high-level radioactive waste. To determine their suitability, the Richton Dome site and the eight other potentially acceptable sites have been evaluated in accordance with the DOE's General Guidelines for the Recommendation of Sites for the Nuclear Waste Repositories. The site is in the Gulf interior region, which is one of five distinct geohydrologic settings considered for the first repository. On the basis of the evaluations reported in this EA, the DOE has found that the Richton Dome site is not disqualified under the guidelines. On the basis of these findings, the DOE is nominating the Richton Dome site as one of five sites suitable for characterization. 3 figs.

  5. 'Heat Dome' Not Budging Until Week's End

    MedlinePlus

    ... fullstory_160083.html 'Heat Dome' Not Budging Until Week's End Eastern part of country still in its ... not be budging before the end of the week, weather forecasters said Tuesday. "With no strong pushes ...

  6. The design research of a spinel dome

    NASA Astrophysics Data System (ADS)

    Zhao, Hongwei; Hou, Tianjin; Zhu, Bin; Huang, Qiu; Gao, Zhifeng

    2011-08-01

    Based on the aerodynamic heating simulated results of a spinel middle-infrared (Mid IR) image guide missile dome flying at supersonic speed, a series of experiments are made and some methods of eliminating aero-heating effect are carried out successfully. First, a simulation experiment on the ground discarding an outside protective shell of a spinel dome is accomplished in order to inspect the withstanding impact ability of the dome. Second, an arc wind tunnel experiment is fulfilled to obtain thermal mechanics characteristic of the spinel dome, and a method to buildup obviously mechanics intensity is approved which is coating diamond protective layer on the external wall of the spinel dome. Third, two heated dome imaging experiments on the ground are made to study the aero-optical phenomenon. Finally, a rocket sled experiment of a guide missile head is made successfully. Experimental results show that when the guide missile head flies in a supersonic, by adjusting the frame integration time of detector etc. the aero-optic effect would decrease greatly.

  7. Extrusion cycles during dome-building eruptions

    NASA Astrophysics Data System (ADS)

    de' Michieli Vitturi, M.; Clarke, A. B.; Neri, A.; Voight, B.

    2013-06-01

    We identify and quantify controls on the timescales and magnitudes of cyclic (periodic) volcanic eruptions using the numerical model DOMEFLOW (de' Michieli Vitturi et al., 2010) which was developed by the authors for magma systems of intermediate composition. DOMEFLOW treats the magma mixture as a liquid continuum with dispersed gas bubbles and crystals in thermodynamic equilibrium with the melt and assumes a modified Poiseuille form of the viscous term for fully developed laminar flow in a conduit of cylindrical cross-section. During ascent, magma pressure decreases and water vapor exsolves and partially degasses from the melt as the melt simultaneously crystallizes, causing changes in mixture density and viscosity. Two mechanisms previously proposed to cause periodic eruption behavior have been implemented in the model and their corresponding timescales explored. The first applies a stick-slip model in which motion of a shallow solid plug is resisted by static/dynamic friction, as described in Iverson et al. (2006). For a constant magma supply rate at depth, this mechanism yields cyclic extrusion with timescales of seconds to tens of seconds with values generally depending on assumed friction coefficients. The second mechanism does not consider friction but treats the plug as a high-viscosity Newtonian fluid. During viscous resistance, pressure beneath the degassed plug can increase sufficiently to overcome dome overburden, plug weight, and viscous forces, and ultimately drive the plug from the conduit. In this second model cycle periods are on the order of hours, and decrease with increasing magma supply rate until a threshold is reached, at which point periodicity disappears and extrusion rate becomes steady (vanishingly short periods). Magma volatile content for fixed chamber pressure has little effect on cycle timescales, but increasing volatile content increases mass flow rate and cycle magnitude as defined by the difference between maximum and minimum

  8. The relation between the spherical aberration of a lens and the spun cusp diffraction catastrophe

    NASA Astrophysics Data System (ADS)

    Nye, J. F.

    2005-01-01

    A lens with spherical aberration, illuminated with an axial plane wave, produces a rotationally-symmetric cusped caustic together with an axial caustic line. Both caustics are truncated by the finite aperture of the lens, and they are decorated by diffraction. One may pass continuously from the limit of small aperture, where the diffraction pattern consists simply of Airy rings around the focus, to the limit of infinite aperture, where the diffraction pattern is that of the three-dimensional spun cusp. This contains ring zeros both inside and outside the cusped caustic. The rings are structurally stable phase singularities (wave dislocations), whose progress out of the focal plane can be traced as the aperture is enlarged. In any axial plane the dislocations are points. Before reaching their final destinations these dislocation points invariably trace out spirals, whose detailed form may be deduced by a perturbation theory. Apart from this, their trajectories, births and deaths are different from those encountered in the analogous case of the two-dimensional Pearcey pattern.

  9. Hybrid Silk Fibers Dry-Spun from Regenerated Silk Fibroin/Graphene Oxide Aqueous Solutions.

    PubMed

    Zhang, Chao; Zhang, Yaopeng; Shao, Huili; Hu, Xuechao

    2016-02-10

    Regenerated silk fibroin (RSF)/graphene oxide (GO) hybrid silk fibers were dry-spun from a mixed dope of GO suspension and RSF aqueous solution. It was observed that the presence of GO greatly affect the viscosity of RSF solution. The RSF/GO hybrid fibers showed from FTIR result lower β-sheet content compared to that of pure RSF fibers. The result of synchrotron radiation wide-angle X-ray diffraction showed that the addition of GO confined the crystallization of silk fibroin (SF) leading to the decrease of crystallinity, smaller crystallite size, and new formation of interphase zones in the artificial silks. Synchrotron radiation small-angle X-ray scattering also proved that GO sheets in the hybrid silks and blended solutions were coated with a certain thickness of interphase zones due to the complex interaction between the two components. A low addition of GO, together with the mesophase zones formed between GO and RSF, enhanced the mechanical properties of hybrid fibers. The highest breaking stress of the hybrid fibers reached 435.5 ± 71.6 MPa, 23% improvement in comparison to that of degummed silk and 72% larger than that of pure RSF silk fiber. The hybrid RSF/GO materials with good biocompatibility and enhanced mechanical properties may have potential applications in tissue engineering, bioelectronic devices, or energy storage. PMID:26784289

  10. On the Measurement of the Electrical Power Produced by Melt Spun Piezoelectric Textile Fibres

    NASA Astrophysics Data System (ADS)

    Matsouka, Dimitroula; Vassiliadis, Savvas; Prekas, Kleanthis; Bayramol, Derman Vatansever; Soin, Navneet; Siores, Elias

    2016-06-01

    Piezoelectric, melt spun, textile fibres as multifunctional materials appeared recently, and they are under thorough investigation and testing in order to define their performance and behaviour. Although piezoelectricity was first reported in 1880 and the piezoelectric behaviour of organic polymers materials has been known since 1969, the fibrous form of the piezoelectric materials under consideration opens new technological horizons; however, it introduces novel restrictions and further complex parameters are involved in their study. The major issue of the current research work is the study of the actual capacity of the piezoelectric fibres, i.e. the electric power produced following mechanical stimulation of the individual fibre. The measurements were made possible after the development of the necessary specific equipment. The test results enabled the ranking of the various types of the piezoelectric fibres according to the respective power generation. The main difference in this research approach is the measurement of the power generated by the fibres. Measurement of the power generated by an electrical power source (in the case of energy harvesting applications which is the prime interest of this research project) is an important characteristic as the requirements of various applications are expressed in units of power. Stating the voltage produced during mechanical deformation of the fibres is not enough (cf. voltage produced due to electrostatic phenomena on textiles where the voltage is in the range is the several kV, but the power is not enough to power a light-emitting diode).

  11. Radially fractured domes: A comparison of Venus and the Earth

    NASA Technical Reports Server (NTRS)

    Janes, Daniel M.; Squyres, Steven W.

    1993-01-01

    Radially fractured domes are large, tectonic and topographic features discovered on the surface of Venus by the Magellan spacecraft. They are thought to be due to uplift over mantle diapirism, and to date are known to occur only on Venus. Since Venus and the Earth are grossly similar in size, composition and structure, we seek to understand why these features have not been seen on the Earth. We model the uplift and fracturing over a mantle diapir as functions of lithospheric thickness and diapir size and depth. We find that lithospheres of the same thickness on the Earth and Venus should respond similarly to the same sized diapir, and that radially fractured domes should form most readily in thin oceanic lithospheres on Earth if diapiric activity is similar on the two planets. However, our current knowledge of the Earth's oceanic floors is insufficient to confirm or deny the presence of radially fractured domes. We compute the expected dimensions for these features on the Earth and suggest a search for them to determine whether mantle diapirism operates similarly on the Earth and Venus.

  12. Ice crystal precipitation at Dome C site (East Antarctica)

    NASA Astrophysics Data System (ADS)

    Santachiara, G.; Belosi, F.; Prodi, F.

    2016-01-01

    For the first time, falling ice crystals were collected on glass slides covered with a thin layer of 2% formvar in chloroform at the Dome Concordia site (Dome C), Antarctica. Samplings were performed in the framework of the 27th Italian Antarctica expedition of the Italian National Program for Research in Antarctica in the period 21 February-6 August 2012. Events of clear-sky precipitations and precipitations from clouds were considered and the replicas obtained were examined under Scanning Electron Microscope (SEM). Several shapes of ice crystals were identified, including "diamond dust" (plates, pyramids, hollow and solid columns), and crystal aggregates varying in complexity. Single events often contained both small (10 μm to 50 μm) and large (hundreds of microns) crystals, suggesting that crystals can form simultaneously near the ground (height of a few hundred metres) and at higher layers (height of thousands of metres). Images of sampled crystal replicas showed that single bullets are not produced separately, but by the disintegration of combinations of bullets. Rimed ice crystals were absent in the Dome C samples, i.e. the only mode of crystal growth was water vapour diffusion. On considering the aerosol in the sampled crystals, we reached the conclusion that inertial impaction, interception and Brownian motion were insufficient to explain the scavenged aerosol. We therefore presume that phoretic forces play a role in scavenging during the crystal growth process.

  13. Cristobalite in a rhyolitic lava dome: evolution of ash hazard

    NASA Astrophysics Data System (ADS)

    Horwell, Claire J.; Le Blond, Jennifer S.; Michnowicz, Sabina A. K.; Cressey, Gordon

    2010-03-01

    Prolonged and heavy exposure to particles of respirable, crystalline silica-rich volcanic ash could potentially cause chronic, fibrotic disease, such as silicosis, in individuals living in areas of frequent ash fall. Here, we show that the rhyolitic ash erupted from Chaitén volcano, Chile, in its dome-forming phase, contains increased levels of the silica polymorph cristobalite, compared to its initial plinian eruption. Ash erupted during the initial, explosive phase (2-5 May 2008) contained approximately 2 wt.% cristobalite, whereas ash generated after dome growth began (from 21 May 2008) contains 13-19 wt.%. The work suggests that active obsidian domes crystallise substantial quantities of cristobalite on time-scales of days to months, probably through vapour-phase crystallisation on the walls of degassing pathways, rather than through spherulitic growth in glassy obsidian. The ash is fine-grained (9.7-17.7 vol.% <4 µm in diameter, the respirable range) and the particles are mostly angular. Sparse, fibre-like particles were confirmed to be feldspar or glass.

  14. Radar scattering properties of steep-sided domes on Venus

    NASA Technical Reports Server (NTRS)

    Ford, Peter G.

    1994-01-01

    More than 100 quasi-circular steep-sided volcanic domes, with diameters ranging from 6 to 60 km, have been observed on the surface of Venus by the Magellan radar mapper. Assuming that they have the shape of a solidified high-viscosity Newtonian fluid, their radar scattering properties can be studied in detail from Magellan images, since a typical radar swath resolves each dome into several tens of thousands of measurements of radar cross section at incidence angles varying fom 15 deg to 55 deg. Through examination of 20 domes in detail, it appears that many of those situated on lava plains scatter radar in a manner that is indistinguishable from that of the surrounding material, suggesting that either (1) they were formed of a relatively high-density high-viscosity material, e.g., andesite, rather than a lower-density one, e.g., rhyolite or dacite; or (2) that their surfaces share a common origin with those of their surroundings, e.g., through in situ weathering or aeolian deposition.

  15. Charged nano-domes and bubbles in epitaxial graphene.

    PubMed

    Trabelsi, A Ben Gouider; Kusmartsev, F V; Robinson, B J; Ouerghi, A; Kusmartseva, O E; Kolosov, O V; Mazzocco, R; Gaifullin, Marat B; Oueslati, M

    2014-04-25

    For the first time, new epitaxial graphene nano-structures resembling charged 'bubbles' and 'domes' are reported. A strong influence, arising from the change in morphology, on the graphene layer's electronic, mechanical and optical properties has been shown. The morphological properties of these structures have been studied with atomic force microscopy (AFM), ultrasonic force microscopy (UFM) and Raman spectroscopy. After initial optical microscopy observation of the graphene, a detailed description of the surface morphology, via AFM and nanomechanical UFM measurements, was obtained. Here, graphene nano-structures, domes and bubbles, ranging from a few tens of nanometres (150–200 nm) to a few μm in size have been identified. The AFM topographical and UFM stiffness data implied the freestanding nature of the graphene layer within the domes and bubbles, with heights on the order of 5–12 nm. Raman spectroscopy mappings of G and 2D bands and their ratio confirm not only the graphene composition of these structures but also the existence of step bunching, defect variations and the carrier density distribution. In particular, inside the bubbles and substrate there arises complex charge redistribution; in fact, the graphene bubble–substrate interface forms a charged capacitance. We have determined the strength of the electric field inside the bubble–substrate interface, which may lead to a minigap of the order of 5 meV opening for epitaxial graphene grown on 4H-SiC face-terminated carbon. PMID:24675237

  16. Distributions of Cranial Pathologies Provide Evidence for Head-Butting in Dome-Headed Dinosaurs (Pachycephalosauridae)

    PubMed Central

    Peterson, Joseph E.; Dischler, Collin; Longrich, Nicholas R.

    2013-01-01

    Pachycephalosaurids are small, herbivorous dinosaurs with domed skulls formed by massive thickening of the cranial roof. The function of the dome has been a focus of debate: the dome has variously been interpreted as the product of sexual selection, as an adaptation for species recognition, or as a weapon employed in intraspecific combat, where it was used in butting matches as in extant ungulates. This last hypothesis is supported by the recent identification of cranial pathologies in pachycephalosaurids, which appear to represent infections resulting from trauma. However, the frequency and distribution of pathologies have not been studied in a systematic fashion. Here, we show that pachycephalosaurids are characterized by a remarkably high incidence of cranial injury, where 22% of specimens have lesions on the dome. Frequency of injury shows no significant difference between different genera, but flat-headed morphs (here interpreted as juveniles or females) lack lesions. Mapping of injuries onto a digitial pachycephalosaurid skull shows that although lesions are distributed across the dome, they cluster near the apex, which is consistent with the hypothesis that the dome functioned for intraspecific butting matches. PMID:23874691

  17. A Cascade of Wnt, Eda, and Shh Signaling Is Essential for Touch Dome Merkel Cell Development

    PubMed Central

    Thoresen, Daniel T.; Miao, Lingling; Williams, Jonathan S.; Wang, Chaochen; Atit, Radhika P.; Wong, Sunny Y.

    2016-01-01

    The Sonic hedgehog (Shh) signaling pathway regulates developmental, homeostatic, and repair processes throughout the body. In the skin, touch domes develop in tandem with primary hair follicles and contain sensory Merkel cells. The developmental signaling requirements for touch dome specification are largely unknown. We found dermal Wnt signaling and subsequent epidermal Eda/Edar signaling promoted Merkel cell morphogenesis by inducing Shh expression in early follicles. Lineage-specific gene deletions revealed intraepithelial Shh signaling was necessary for Merkel cell specification. Additionally, a Shh signaling agonist was sufficient to rescue Merkel cell differentiation in Edar-deficient skin. Moreover, Merkel cells formed in Fgf20 mutant skin where primary hair formation was defective but Shh production was preserved. Although developmentally associated with hair follicles, fate mapping demonstrated Merkel cells primarily originated outside the hair follicle lineage. These findings suggest that touch dome development requires Wnt-dependent mesenchymal signals to establish reciprocal signaling within the developing ectoderm, including Eda signaling to primary hair placodes and ultimately Shh signaling from primary follicles to extrafollicular Merkel cell progenitors. Shh signaling often demonstrates pleiotropic effects within a structure over time. In postnatal skin, Shh is known to regulate the self-renewal, but not the differentiation, of touch dome stem cells. Our findings relate the varied effects of Shh in the touch dome to the ligand source, with locally produced Shh acting as a morphogen essential for lineage specification during development and neural Shh regulating postnatal touch dome stem cell maintenance. PMID:27414798

  18. Features of Bayou Choctaw SPR caverns and internal structure of the salt dome.

    SciTech Connect

    Munson, Darrell E.

    2007-07-01

    The intent of this study is to examine the internal structure of the Bayou Choctaw salt dome utilizing the information obtained from graphical representations of sonar survey data of the internal cavern surfaces. Many of the Bayou Choctaw caverns have been abandoned. Some existing caverns were purchased by the Strategic Petroleum Reserve (SPR) program and have rather convoluted histories and complex cavern geometries. In fact, these caverns are typically poorly documented and are not particularly constructive to this study. Only two Bayou Choctaw caverns, 101 and 102, which were constructed using well-controlled solutioning methods, are well documented. One of these was constructed by the SPR for their use while the other was constructed and traded for another existing cavern. Consequently, compared to the SPR caverns of the West Hackberry and Big Hill domes, it is more difficult to obtain a general impression of the stratigraphy of the dome. Indeed, caverns of Bayou Choctaw show features significantly different than those encountered in the other two SPR facilities. In the number of abandoned caverns, and some of those existing caverns purchased by the SPR, extremely irregular solutioning has occurred. The two SPR constructed caverns suggest that some sections of the caverns may have undergone very regular solutioning to form uniform cylindrical shapes. Although it is not usually productive to speculate, some suggestions that point to the behavior of the Bayou Choctaw dome are examined. Also the primary differences in the Bayou Choctaw dome and the other SPR domes are noted.

  19. A Cascade of Wnt, Eda, and Shh Signaling Is Essential for Touch Dome Merkel Cell Development.

    PubMed

    Xiao, Ying; Thoresen, Daniel T; Miao, Lingling; Williams, Jonathan S; Wang, Chaochen; Atit, Radhika P; Wong, Sunny Y; Brownell, Isaac

    2016-07-01

    The Sonic hedgehog (Shh) signaling pathway regulates developmental, homeostatic, and repair processes throughout the body. In the skin, touch domes develop in tandem with primary hair follicles and contain sensory Merkel cells. The developmental signaling requirements for touch dome specification are largely unknown. We found dermal Wnt signaling and subsequent epidermal Eda/Edar signaling promoted Merkel cell morphogenesis by inducing Shh expression in early follicles. Lineage-specific gene deletions revealed intraepithelial Shh signaling was necessary for Merkel cell specification. Additionally, a Shh signaling agonist was sufficient to rescue Merkel cell differentiation in Edar-deficient skin. Moreover, Merkel cells formed in Fgf20 mutant skin where primary hair formation was defective but Shh production was preserved. Although developmentally associated with hair follicles, fate mapping demonstrated Merkel cells primarily originated outside the hair follicle lineage. These findings suggest that touch dome development requires Wnt-dependent mesenchymal signals to establish reciprocal signaling within the developing ectoderm, including Eda signaling to primary hair placodes and ultimately Shh signaling from primary follicles to extrafollicular Merkel cell progenitors. Shh signaling often demonstrates pleiotropic effects within a structure over time. In postnatal skin, Shh is known to regulate the self-renewal, but not the differentiation, of touch dome stem cells. Our findings relate the varied effects of Shh in the touch dome to the ligand source, with locally produced Shh acting as a morphogen essential for lineage specification during development and neural Shh regulating postnatal touch dome stem cell maintenance. PMID:27414798

  20. A comparison between semi-spheroid- and dome-shaped quantum dots coupled to wetting layer

    SciTech Connect

    Shahzadeh, Mohammadreza; Sabaeian, Mohammad

    2014-06-15

    During the epitaxial growth method, self-assembled semi-spheroid-shaped quantum dots (QDs) are formed on the wetting layer (WL). However for sake of simplicity, researchers sometimes assume semi-spheroid-shaped QDs to be dome-shaped (hemisphere). In this work, a detailed and comprehensive study on the difference between electronic and transition properties of dome- and semi-spheroid-shaped quantum dots is presented. We will explain why the P-to-S intersubband transition behaves the way it does. The calculated results for intersubband P-to-S transition properties of quantum dots show two different trends for dome-shaped and semi-spheroid-shaped quantum dots. The results are interpreted using the probability of finding electron inside the dome/spheroid region, with emphasis on the effects of wetting layer. It is shown that dome-shaped and semi-spheroid-shaped quantum dots feature different electronic and transition properties, arising from the difference in lateral dimensions between dome- and semi-spheroid-shaped QDs. Moreover, an analogy is presented between the bound S-states in the quantum dots and a simple 3D quantum mechanical particle in a box, and effective sizes are calculated. The results of this work will benefit researchers to present more realistic models of coupled QD/WL systems and explain their properties more precisely.

  1. Silicic lava dome growth in the 1934-1935 Showa Iwo-jima eruption, Kikai caldera, south of Kyushu, Japan

    NASA Astrophysics Data System (ADS)

    Maeno, Fukashi; Taniguchi, Hiromitsu

    2006-06-01

    The 1934-1935 Showa Iwo-jima eruption started with a silicic lava extrusion onto the floor of the submarine Kikai caldera and ceased with the emergence of a lava dome. The central part of the emergent dome consists of lower microcrystalline rhyolite, grading upward into finely vesicular lava, overlain by coarsely vesicular lava with pumice breccia at the top. The lava surface is folded, and folds become tighter toward the marginal part of the dome. The dome margin is characterized by two zones: a fracture zone and a breccia zone. The fracture zone is composed of alternating layers of massive lava and welded oxidized breccia. The breccia zone is the outermost part of the dome, and consists of glassy breccia interpreted to be hyaloclastite. The lava dome contains lava with two slightly different chemical compositions; the marginal part being more dacitic and the central part more rhyolitic. The fold geometry and chemical compositions indicate that the marginal dacite had a slightly higher temperature, lower viscosity, and lower yield stress than the central rhyolite. The high-temperature dacite lava began to effuse in the earlier stage from the central crater. The front of the dome came in contact with seawater and formed hyaloclastite. During the later stage, low-temperature rhyolite lava effused subaerially. As lava was injected into the growing dome, the fracture zone was produced by successive fracturing, ramping, and brecciation of the moving dome front. In the marginal part, hyaloclastite was ramped above the sea surface by progressive increments of the new lava. The central part was folded, forming pumice breccia and wrinkles. Subaerial emplacement of lava was the dominant process during the growth of the Showa Iwo-jima dome.

  2. Dome, Sweet Dome--Geodesic Structures Teach Math, Science, and Technology Principles

    ERIC Educational Resources Information Center

    Shackelford, Ray; Fitzgerald, Michael

    2007-01-01

    Today, geodesic domes are found on playgrounds, homes, over radar installations, storage facilities, at Disney's Epcot Center, and at World's Fairs. The inventor of the design, Buckminster Fuller, thought that geodesic domes could be used to cover large areas and even designed one to cover all of New York's Manhattan Island. This article details…

  3. Holodeck: Telepresence Dome Visualization System Simulations

    NASA Technical Reports Server (NTRS)

    Hite, Nicolas

    2012-01-01

    This paper explores the simulation and consideration of different image-projection strategies for the Holodeck, a dome that will be used for highly immersive telepresence operations in future endeavors of the National Aeronautics and Space Administration (NASA). Its visualization system will include a full 360 degree projection onto the dome's interior walls in order to display video streams from both simulations and recorded video. Because humans innately trust their vision to precisely report their surroundings, the Holodeck's visualization system is crucial to its realism. This system will be rigged with an integrated hardware and software infrastructure-namely, a system of projectors that will relay with a Graphics Processing Unit (GPU) and computer to both project images onto the dome and correct warping in those projections in real-time. Using both Computer-Aided Design (CAD) and ray-tracing software, virtual models of various dome/projector geometries were created and simulated via tracking and analysis of virtual light sources, leading to the selection of two possible configurations for installation. Research into image warping and the generation of dome-ready video content was also conducted, including generation of fisheye images, distortion correction, and the generation of a reliable content-generation pipeline.

  4. Using analog flow experiments to model morphologies developed during episodic dome growth: A case study of Mount St Helens, 1980-1986

    NASA Astrophysics Data System (ADS)

    Altman, K. M.; Teasdale, R.

    2009-12-01

    From 1980 to 1986 the dacite dome at Mount St. Helens was emplaced as a series of 17 events, identified by different growth rates, volumes, height to diameter ratios, emplacement rates, surface textures and dome morphologies (Swanson, 1989). Rates of emplacement characterize three periods; between October 18, 1980 and the end of 1981 the growth rate was 1.8 x 10^6 m^3/month; between March 1982 and March 1984 the growth rate was 1.3 x 10^6 m^3/month; followed by a growth rate of 0.62 x 10^6 m^3/month until the end of the emplacement events in 1986 (Swanson, 1989). The shape of the dome changed from 1980 to 1986 as a function of magma viscosity, tensile strength of the hot core, and thickness of the outer shell (Swanson, 1989). The height to diameter ratios (h:d) recorded throughout the growth of the dome have been used to quantify the changes in the shape of the dome. The dome was flatter during the first period of emplacement when larger volumes kept the dome hotter and hindered the formation of a thick, cool outer crust (Swanson, 1989). Once the growth rate slowed by June 1981, a thick skin had formed and allowed the dome to steepen (Swanson, 1989). Analog models presented here aim to reproduce the emplacement of the domes based on observations and data recorded at Mount St. Helens from 1980 to 1986. Flow experiments use a slurry of PEG (poly-ethelyne glycol) mixed with kaolin powder that is pumped into a tank of cold water (Fink and Griffiths, 1998). PEG is used because it is liquid at room temperature and solidifies in the cold water. Kaolin powder is added to the PEG to simulate the viscosity of the dacite domes. The observed and recorded data from Mount St. Helens are used to constrain analog flow model parameters such as slope, effusion rate, and PEG viscosity in an attempt to recreate the dome morphologies observed in the 1980 to 1986 episodes. As expected, dome morphology in experiments varies with the crustal thickness developed during experiments. The

  5. The effect of heat treatment on microstructures of melt-spun Fe 6.5 wt% Si alloys

    NASA Astrophysics Data System (ADS)

    Monstadt, H.; Hornbogen, E.; Rohde, J.

    1992-07-01

    The microstructures of melt-spun Fe 6.5 wt% Si alloys were investigated. In a special range of cooling rates, low silicon contents up to 9 wt% Si form a diffusion-controlled interface modulation (microsegregation). Amplitudes of the lamellar spacing increase with decreasing cooling rate. A model was developed to explain the transition from rapid crystallization of a homogeneous solid solution to microsegregation. A model for the homogenization of interdendritic segregation in the solid state was applied to the homogenization of the periodic microsegregations. The heat treatment parameters for the homogenization were verified by the experimental results. The relations of this structural phenomenon to bulk properties such as mechanical strength and ductility as well as magnetic properties are discussed briefly.

  6. Interaction between an emerging flux region and a pre-existing fan-spine dome observed by IRIS and SDO

    NASA Astrophysics Data System (ADS)

    Jiang, Fayu; Zhang, Jun; Yang, Shuhong

    2015-08-01

    We present multiwavelength observations of a fan-spine dome in the active region NOAA 11996 with the Interface Region Imaging Spectrograph (IRIS) and the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory (SDO) on 2014 March 9. The destruction of the fan-spine topology owing to the interaction between its magnetic fields and a nearby emerging flux region (EFR) is observed for the first time. The line-of-sight magnetograms from the Helioseismic and Magnetic Imager on board the SDO reveal that the dome is located on the mixed magnetic fields, with its rim rooted in the redundant positive polarity surrounding the minority parasitic negative fields. The fan surface of the dome consists of a filament system and recurring jets are observed along its spine. The jet occurring around 13:54 UT is accompanied by a quasi-circular ribbon that brightens in the clockwise direction along the bottom rim of the dome, which may indicate an occurrence of slipping reconnection in the fan-spine topology. The EFR emerges continuously and meets with the magnetic fields of the dome. Magnetic cancellations take place between the emerging negative polarity and the outer positive polarity of the dome's fields, which lead to the rise of the loop connecting the EFR and brightenings related to the dome. A single Gaussian fit to the profiles of the IRIS Si IV 1394 Å line is used in the analysis. It appears that there are two rising components along the slit, in addition to the rise in the line-of-sight direction. The cancellation process repeats again and again. Eventually the fan-spine dome is destroyed and a new connectivity is formed. We suggest that magnetic reconnection between the EFR and the magnetic fields of the fan-spine dome is responsible for the destruction of the dome.

  7. Effective pine bark composting with the Dome Aeration Technology

    SciTech Connect

    Trois, Cristina . E-mail: troisc@ukzn.ac.za; Polster, Andreas

    2007-07-01

    In South Africa garden refuse is primarily disposed of in domestic landfills. Due to the large quantities generated, any form of treatment would be beneficial for volume reduction, waste stabilization and resource recovery. Dome Aeration Technology (DAT) is an advanced process for aerobic biological degradation of garden refuse and general waste [Paar, S., Brummack, J., Gemende, B., 1999a. Advantages of dome aeration in mechanical-biological waste treatment. In: Proceedings of the 7th International Waste Management and Landfill Symposium, Cagliari, 4-8 October 1999; Paar, S., Brummack, J., Gemende, B., 1999b. Mechanical-biological waste stabilization by the dome aeration method. Environment Protection Engineering 25 (3/99). Mollekopf, N., Brummack, J., Paar, S., Vorster, K., 2002. Use of the Dome Aeration Technology for biochemical stabilization of waste prior to landfilling. In: Proceedings of the Wastecon 2002, Waste Congress and Exhibition, Durban, South Africa.]. It is a non-reactor open windrow composting process, with the main advantage being that the input material needs no periodic turning. A rotting time of only 3-4 months indicates the high efficiency. Additionally, the low capital/operational costs, low energy inputs and limited plant requirements provide potential for use in aerobic refuse stabilization. The innovation in the DAT process is the passive aeration achieved by thermally driven advection through open windrows caused by temperature differences between the degrading material and the outside environment. This paper investigates the application of Dome Aeration Technology to pine bark composting as part of an integrated waste management strategy. A full-scale field experiment was performed at the Bisasar Road Landfill Site in Durban to assess the influence of climate, waste composition and operational conditions on the process. A test windrow was constructed and measurements of temperature and airflow through the material were taken. The process

  8. Geology of Damon Mound Salt Dome, Texas

    SciTech Connect

    Collins, E.W.

    1989-01-01

    Geological investigation of the stratigraphy, cap-rock characteristics, deformation and growth history, and growth rate of a shallow coastal diapir. Damon Mound salt dome, located in Brazoria County, has salt less than 600 feet and cap rock less than 100 feet below the surface; a quarry over the dome provides excellent exposures of cap rock as well as overlying Oligocene to Pleistocene strata. These conditions make it ideal as a case study for other coastal diapirs that lack bedrock exposures. Such investigations are important because salt domes are currently being considered by chemical waste disposal companies as possible storage and disposal sites. In this book, the author reviews previous research, presents additional data on the subsurface and surface geology at Damon Mound, and evaluates Oligocene to post-Pleistocene diapir growth.

  9. Isotopic analysis of northern Himalayan gneiss domes

    NASA Astrophysics Data System (ADS)

    Hassett, W. C.

    2010-12-01

    The Leo Pargil, Renbu, and Yalashangbo gneiss domes are among the western and eastern most in the chain of north Himalayan gneiss domes. The processes of gneiss dome formation are still debated, but there is a growing consensus that they result from the diapiric rise of pooled melt from a mid-crustal, ductile channel (Whitney et al., 2004). Under the channel flow model, the ductile channel is exhumed towards the southern Himalayan range front and is exposed as the Greater Himalayan Sequence (GHS) (Beaumont et al., 2004). Gneiss domes should have a petrogenetic relationship to the GHS if the channel flow theory is correct. Geochemical investigation of these gneiss domes can therefore help to determine their provenance and mode of origin. Leo Pargil is composed of high-grade metamorphic rocks consisting of schists, phyllites, metasiltstone, metagraywacke, and subordinate quartzites, with numerous cm-m scale two-mica granite, tourmaline granite, and leucogranite dikes that constitute between 10% and 50% of the host rock (Thiede, 2006). The Renbu gneiss dome consists of an undeformed two-mica leucogranite pluton intruded into Triassic shales, and lies on the west side of a northerly trending graben belonging to the Yadong-Gulu rift system (Miller, unpublished). The Yalashangbo gneiss dome consists of muscovite-biotite granite pluton, with common pegmatite dikes and gneisses (Zhang et al., 2007). Leo Pargil has relict U/Pb zircon core ages ranging from Late Archean to Middle Paleozoic (2.8 Ga to 400 Ma) and Middle Eocene to Middle Miocene ages (49 Ma to 15 Ma) for zircon rims. The Renbu dome has relict U/Pb zircon core ages ranging from Late Archean to Late Triassic (2.5 Ga to 200 Ma) and Late Eocene to Late Miocene ages (39 Ma to 7 Ma) for zircon rims. Yalashangbo has relict U/Pb zircon core ages ranging from Late Paleoproterozoic to Middle Cretaceous (1.8 Ga to 115 Ma), but has no zircon rim ages and therefore does not record the timing of most recent magmatism

  10. Environmental assessment, Richton Dome site, Mississippi (US)

    SciTech Connect

    none,

    1986-05-01

    The Nuclear Waste Policy Act of 1982 (42 USC Sections 10101-10226) requires the environmental assessment of a potential site to include a statement of the basis for the nomination of a site as suitable for characterization. Volume 2 of this environmental assessment provides a detailed evaluation of the Richton Dome Site and its suitability as the site for a radioactive waste disposal facility under DOE siting guidelines, as well as a comparison of the Richton Dome site with other proposed sites. Evaluation of the Richton Dome site is based on the reference repository design, but the evaluation will not change if based on the Mission Plan repository concept. The comparative evaluation of proposed sites is required under DOE guidelines, but is not intended to directly support the subsequent recommendation of three sites for characterization as candidate sites. 428 refs., 24 figs., 62 tabs. (MHB)

  11. Mount Unzen dome continues to grow

    NASA Astrophysics Data System (ADS)

    Volcanic activity on Japan's Mount Unzen, which erupted on June 3 killing 41 people, continues to build, according to latest reports. Dome extrusion and pyroclastic-flow formation continued at Unzen as of June 24. On June 14, the dome was 100 m wide and 50 m high; it grew another 20 m in height by June 16. Cracks in the dome emitted gas to 200-300 m height, and periodic explosions produced 1-km-high ash columns. The evacuation area was expanded on June 17, bringing the total number of evacuees to more than 10,000. The following report on recent activity at Unzen was provided by the Smithsonian Institution's Global Volcanism Network. All times are local (= UT + 9 hours).

  12. Spun optical fibres: A helical structure of linear birefringence or circular birefringence?

    SciTech Connect

    Morshnev, Sergey K; Gubin, Vladimir P; Vorob'ev, I P; Starostin, I I; Sazonov, Aleksandr I; Chamorovsky, Yury K; Korotkov, N M

    2009-03-31

    An experiment has been proposed, theoretically substantiated and accomplished which has provided conclusive evidence in favour of one of two models for the behaviour of polarised light in optical fibres fabricated by spinning preforms with a high built-in linear birefringence (spun fibres): a helical structure of the built-in linear birefringence axes and circular birefringence. The experiment, carried out with a reflective fibreoptic dual-polarisation interferometer, has shown that the behaviour of polarisation states in spun fibres can be understood in terms of a helical structure of the built-in linear birefringence axes. (optical fibres)

  13. OPTICAL FIBRES AND FIBREOPTIC SENSORS: Spun microstructured optical fibresfor Faraday effect current sensors

    NASA Astrophysics Data System (ADS)

    Chamorovsky, Yury K.; Starostin, Nikolay I.; Morshnev, Sergey K.; Gubin, Vladimir P.; Ryabko, Maksim V.; Sazonov, Aleksandr I.; Vorob'ev, Igor'L.

    2009-11-01

    We report a simple design of spun holey fibres and the first experimental study of the magneto-optical response of spun microstructured fibres with high built-in birefringence. Such fibres enable the Faraday-effect-induced phase shift to effectively accumulate in a magnetic field even at very small coiling diameters. For example, the magneto-optical sensitivity of a 5-mm-diameter fibre coil consisting of 100 turns is ~70% that of an ideal fibre, in good agreement with theoretical predictions.

  14. Metamorphism on the Moon: A terrestrial analogue in the Vredefort dome, South Africa?

    NASA Astrophysics Data System (ADS)

    Gibson, Roger L.; Reimold, W. Uwe; Ashley, Andrew J.; Koeberl, Christian

    2002-05-01

    A new model is proposed to explain the origin of enigmatic fine-grained granulite facies rocks sampled from the Moon, based on observations from the Vredefort dome, South Africa. The dome is the deeply eroded central uplift of the ˜300-km-diameter Vredefort impact structure. In the dome, fine-grained granulites displaying poikilitic or granoblastic microstructures were formed by relatively slow cooling of shock ± friction melts derived at T > 1350 °C. Slow cooling was achieved owing to the >7 km depth of burial of the rocks following the impact. At least some of the lunar granulitic impactites may also have formed by shock heating and slow cooling at deep levels within the central uplifts of large impact structures, without the need for additional heating by younger intrusive or impact melt bodies.

  15. Domes Made the Difference At Valley R-6.

    ERIC Educational Resources Information Center

    Graves, Larry

    2000-01-01

    Describes the development from conception through construction of three domes in the Valley R-6 School District (Washington County, Missouri). Arguments for, and investigations into, building monolithic domes, funding issues, and efforts to gain voter approval are discussed. (GR)

  16. FIRST OBSERVATIONS OF A DOME-SHAPED LARGE-SCALE CORONAL EXTREME-ULTRAVIOLET WAVE

    SciTech Connect

    Veronig, A. M.; Muhr, N.; Kienreich, I. W.; Temmer, M.; Vrsnak, B.

    2010-06-10

    We present first observations of a dome-shaped large-scale extreme-ultraviolet coronal wave, recorded by the Extreme Ultraviolet Imager instrument on board STEREO-B on 2010 January 17. The main arguments that the observed structure is the wave dome (and not the coronal mass ejection, CME) are (1) the spherical form and sharpness of the dome's outer edge and the erupting CME loops observed inside the dome; (2) the low-coronal wave signatures above the limb perfectly connecting to the on-disk signatures of the wave; (3) the lateral extent of the expanding dome which is much larger than that of the coronal dimming; and (4) the associated high-frequency type II burst indicating shock formation low in the corona. The velocity of the upward expansion of the wave dome (v {approx} 650 km s{sup -1}) is larger than that of the lateral expansion of the wave (v {approx} 280 km s{sup -1}), indicating that the upward dome expansion is driven all the time, and thus depends on the CME speed, whereas in the lateral direction it is freely propagating after the CME lateral expansion stops. We also examine the evolution of the perturbation characteristics: first the perturbation profile steepens and the amplitude increases. Thereafter, the amplitude decreases with r {sup -2.5{+-}0.3}, the width broadens, and the integral below the perturbation remains constant. Our findings are consistent with the spherical expansion and decay of a weakly shocked fast-mode MHD wave.

  17. Statistical forecasting of repetitious dome failures during the waning eruption of Redoubt Volcano, Alaska, February-April 1990

    USGS Publications Warehouse

    Page, R.A.; Lahr, J.C.; Chouet, B.A.; Power, J.A.; Stephens, C.D.

    1994-01-01

    successful forecasts and two false alarms; no events would have been missed. On closer examination, the intervals between successive dome failures are not uniform but tend to increase with time. This increase attests to the continuous, slowly decreasing supply of magma to the surface vent during the waning phase of the eruption. The domes formed in a precarious position in a breach in the summit crater rim where they were susceptible to gravitational collapse. The instability of the February 15-April 21 domes relative to the earlier domes is attributed to reaming the lip of the vent by a laterally directed explosion during the major dome-destroying eruption of February 15, a process which would leave a less secure foundation for subsequent domes. ?? 1994.

  18. Statistical forecasting of repetitious dome failures during the waning eruption of Redoubt Volcano, Alaska, February April 1990

    NASA Astrophysics Data System (ADS)

    Page, Robert A.; Lahr, John C.; Chouet, Bernard A.; Power, John A.; Stephens, Christopher D.

    1994-08-01

    successful forecasts and two false alarms; no events would have been missed. On closer examination, the intervals between successive dome failures are not uniform but tend to increase with time. This increase attests to the continuous, slowly decreasing supply of magma to the surface vent during the waning phase of the eruption. The domes formed in a precarious position in a breach in the summit crater rim where they were susceptible to gravitational collapse. The instability of the February 15-April 21 domes relative to the earlier domes is attributed to reaming the lip of the vent by a laterally directed explosion during the major dome-destroying eruption of February 15, a process which would leave a less secure foundation for subsequent domes.

  19. Water recycling at the Millennium Dome.

    PubMed

    Hills, S; Smith, A; Hardy, P; Birks, R

    2001-01-01

    Thames Water is working with the New Millennium Experience Company to provide a water recycling system for the Millennium Dome which will supply 500 m3/d of reclaimed water for WC and urinal flushing. The system will treat water from three sources: rainwater--from the Dome roof greywater--from handbasins in the toilet blocks groundwater--from beneath the Dome site The treatment technologies will range from "natural" reedbeds for the rainwater, to more sophisticated options, including biological aerated filters and membranes for the greywater and groundwater. Pilot scale trials were used to design the optimum configuration. In addition to the recycling system, water efficient devices will be installed in three of the core toilet blocks as part of a programme of research into the effectiveness of conservation measures. Data on water usage and customer behaviour will be collected via a comprehensive metering system. Information from the Dome project on the economics and efficiency of on-site recycling at large scale and data on water efficient devices, customer perception and behaviour will be of great value to the water industry. For Thames Water, the project provides vital input to the development of future water resource strategies. PMID:11436793

  20. After-Hours Science: Gee, A Dome!

    ERIC Educational Resources Information Center

    Santos, John G.

    1984-01-01

    Nature's Classroom (Southbridge, MA), which provides field experiences, academic classes, and activities in the natural sciences, has been recognized as an outstanding program by the National Science Teachers Association's Search for Excellence in Science Education project. Various program activities (including building a geodesic dome) are…

  1. Geodesic Dome Activity Provides Serious Fun!

    ERIC Educational Resources Information Center

    Anderson, Richard

    2009-01-01

    After the author's class completed last year's 44'-long timber-framed covered bridge project, he was pondering what other learning challenge he could pose to his students. He came across an article on geodesic dome construction in the September 2007 issue of "Tech Directions" and, he had his answer. In this article, the author and his students…

  2. Conformal dome correction with counterrotating phase plates

    NASA Astrophysics Data System (ADS)

    Sparrold, Scott W.; Mills, James P.; Knapp, David J.; Ellis, Kenneth S.; Mitchell, Thomas A.; Manhart, Paul K.

    2000-07-01

    Windows and domes that are shaped to aerodynamic requirements can increase range and speed for the host platform. This class of optical systems is referred to as conformal optics. The solution discussed here is intended for conformal missile systems having gimbals that point the optical line of sight through different parts of the dome. A conformal dome induces large amounts of varying aberration, tens to hundreds of waves across gimbal angle, and therefore requires dynamic correction. Space is very constricted in missile sensors, and it is therefore highly desirable to limit the number of motors used for aberration correction. This paper describes the performance of a new class of optical systems that employ counterrotating phase prisms to correct conformal dome aberrations while gimbaling the optical system. The phase surfaces on the prisms are described by Zernike circular polynomials. Since the shear across the phase surfaces is rotational, the only aberrations that are generated are those without rotational symmetry, such as tilt, coma, or astigmatism. Using this approach, CODE VTM was used to analyze and design a compact, high-performance conformal optical system.

  3. CMB Observations from DomeC

    NASA Astrophysics Data System (ADS)

    de Bernardis, P.

    DomeC is likely to be the best site in the world for mm and sub-mm observations. In this paper we focus on what can be done from DomeC to investigate the detailed properties of the Cosmic Microwave Background (CMB). Two experiment typologies are particularly promising: precision measurements of the polarization of the CMB, to confirm the presence of an inflation phase in the very early universe, and high resolution measurements of the Sunyaev-Zeldovich effect (SZE) in clusters of galaxies, which can be used to investigate dark energy and dark matter in the Universe. Several important teams are currently carrying out experiments of the first kind; DomeC is the location of the BRAIN experiment, which uses bolometric interferometry as the tool to produce sensitive measurements with low systematic effects, and certainly orthogonal to the systematic effects of all other instruments currently developed to this purpose. DomeC will be an ideal location for a large dish telescope for mm and sub-mm measurements. In addition to cutting-edge sub-mm science, a telescope complementing SPT (in size and/or in frequency) will be ideal for special CMB observation, like the detection of non-Gaussian features, the measurement of relativistic effects in SZE, the measurement of the SZE resulting from the decay products of super-symmetric dark matter in selected clusters.

  4. The Urban Dust Dome: A Demonstration Model

    ERIC Educational Resources Information Center

    Cross, Ralph D.

    1973-01-01

    Working plans for an inexpensive urban dust dome model are presented together with some generalizations about urban atmosphere pollution. Theories and principles of atmospheric pollution which are introduced can be made meaningful to elementary students through classroom use of this model. (SM)

  5. Dome Storage of Farmer Stock Peanuts

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The small-scale farmer stock storage research facility at the National Peanut Research Laboratory in Dawson, GA consisting of four warehouses and four monolithic domes was used to conduct a 3-yr study looking at the effects of storing peanuts through the summer months following harvest. The study wa...

  6. A chemically reactive spinning dope for significant improvements in wet spun carbon nanotube fibres.

    PubMed

    González-Domínguez, Jose M; Neri, Wilfrid; Maugey, Maryse; Poulin, Philippe; Ansón-Casaos, Alejandro; Martínez, M Teresa

    2013-05-11

    Single-walled carbon nanotubes can be spun in a polyvinyl alcohol stream to produce nanocomposite fibres. We use a facile ester linking between both elements to create improved fibres which exhibit outstanding enhancements in the absence of post-processing stages, providing a promising alternative based on a chemical method. PMID:23471091

  7. Relationships of cotton fiber properties to ring-spun yarn quality on selected High Plains cottons

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of this research was to evaluate the adequacy of High Volume Instruement (HVI) and Advanced Fiber Information System (AFIS) fiber quality parameters for predicting quality parameters of ring-spun yarns considering differences in harvest method. Fiber properties measured using the HVI (...

  8. The Impact of Short Fiber Content on the Quality of Cotton Ring Spun Yarn

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A study was carried to obtain a quantitative assessment of how the presence of short fiber (< 12.5 mm long) in raw cotton affect the quality of ring yarn spun from the mix. Properties of the raw cotton were measured on HVI and AFIS instruments and by the manual Suter-Webb Array method. Twenty-nine...

  9. COTTON FIBERS: PROPERTIES AND INTERACTION WITH FLAX FIBERS IN BLENDS (FOCUS ON ROTOR SPUN YARN)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    FASHION DICTATES WHAT FIBERS AND YARNS WILL BE UTILIZED TO MAKE APPAREL AND OTHER TEXTILE FASHION ITEMS. IN RECENT YEARS, THERE HAS BEEN AN INCREASE IN FLAX/COTTON BLENDS, PARTICULARLY IN APPAREL. TRADITIONALLY, FLAX HAS BEEN SPUN AS "LONG LINE" STAPLE LENGTH, AS WOULD BE THE CASE IN THE SPINNING ...

  10. Solution blow spun Poly(lactic acid)/Hydroxypropyl methylcellulose nanofibers with antimicrobial properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Poly(lactic acid) (PLA) nanofibers containing hydroxypropyl methylcellulose (HPMC) and tetracycline hydrochloride (THC) were solution blow spun from two different solvents, chloroform/acetone (CA, 80:20 v/v) and 2,2,2-triflouroethanol (TFE). The diameter distribution, chemical, thermal, thermal stab...

  11. Capabilites of an arch element for correcting conformal optical domes

    NASA Astrophysics Data System (ADS)

    Sparrold, Scott W.; Knapp, David J.; Manhart, Paul K.; Elsberry, Kevin W.

    1999-10-01

    This paper presents an approach for correcting conformal missile domes with a non-rotationally symmetric optical element called an arch. A parametric study in terms of aerodynamics, fineness ratio, maximum seeker look angle and dome index of refraction will demonstrate its capabilities for correcting conformal domes. A nomograph for trading optical performance versus relative missile range will also be presented.

  12. 49 CFR 178.255-3 - Expansion domes.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Expansion domes. 178.255-3 Section 178.255-3 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY... Specifications for Portable Tanks § 178.255-3 Expansion domes. (a) Expansion domes, if applied, must have...

  13. 49 CFR 178.255-3 - Expansion domes.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 3 2013-10-01 2013-10-01 false Expansion domes. 178.255-3 Section 178.255-3 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Portable Tanks § 178.255-3 Expansion domes. (a) Expansion domes, if applied, must have a minimum...

  14. 49 CFR 178.255-3 - Expansion domes.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 3 2012-10-01 2012-10-01 false Expansion domes. 178.255-3 Section 178.255-3 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Portable Tanks § 178.255-3 Expansion domes. (a) Expansion domes, if applied, must have a minimum...

  15. 49 CFR 178.255-3 - Expansion domes.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 3 2014-10-01 2014-10-01 false Expansion domes. 178.255-3 Section 178.255-3 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Portable Tanks § 178.255-3 Expansion domes. (a) Expansion domes, if applied, must have a minimum...

  16. 49 CFR 178.255-3 - Expansion domes.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 3 2011-10-01 2011-10-01 false Expansion domes. 178.255-3 Section 178.255-3 Transportation Other Regulations Relating to Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS SAFETY... Portable Tanks § 178.255-3 Expansion domes. (a) Expansion domes, if applied, must have a minimum...

  17. Influence of quenching rate on the microstructure and magnetic properties of melt-spun L1{sub 0}-FePt/Fe{sub 2}B nanocomposite magnets

    SciTech Connect

    Zhang, Wei; Yubuta, Kunio; Sharma, Parmanand; Makino, Akihiro; Inoue, Akihisa

    2007-05-01

    The quenching rate, which is dependent on the surface velocity (V{sub s}) of Cu wheel during melt spinning, has significant influence on the formation of nanocomposite structure in the Fe{sub 52}Pt{sub 32}B{sub 18} melt-spun ribbons. The L1{sub 0}-FePt/Fe{sub 2}B hard magnetic nanocomposite structure was formed at V{sub s}=20-37 m/s, while the soft magnetic fcc-FePt+amorphous phases were formed at V{sub s}=40-50 m/s. The ribbons melt spun at V{sub s}=37 m/s exhibit in-plane coercivity ({sub i}H{sub c})=760 kA/m, remanence (B{sub r})=0.71 T, and energy product (BH){sub max}=93.4 kJ/m{sup 3}. The B{sub r}=0.74-0.77 T, {sub i}H{sub c}=681-718 kA/m, and (BH){sub max}=101-108 kJ/m{sup 3} were obtained for the ribbons melt spun at V{sub s}=50 m/s and annealed at 748-773 K for 900 s. The improvement in hard magnetic properties is due to the formation of more finer and homogeneous nanocomposite structure, which results in the enhancement in exchange coupling among the nanosized hard L1{sub 0}-FePt and soft Fe{sub 2}B magnetic phases.

  18. Structure and Kinematics of a Complex Crater: Upheaval Dome, Southeast, Utah

    NASA Technical Reports Server (NTRS)

    Kriens, B. J.; Herkenhoff, K. E.; Shoemaker, E. M.

    1997-01-01

    Two vastly different phenomena, extraterrestrial impact and salt diapirism, have been proposed for the origin of Upheaval Dome. Upheaval Dome is a about 2.5-km-diameter structural dome surrounded by a 5-km-diameter ring structural depression, which is in turn flanked by extensive, nearly flat-lying Colorado Plateau strata. Seismic refraction data and geologic mapping indicate that the dome originated by the collapse of a transient cavity formed by impact; data also show that rising salt has had a negligible influence on dome development. Evidence for this includes several factors: (1) a rare lag deposit of impactite is present; (2) fan-tailed fracture surfaces (shatter surfaces) and a few shattercones are present; (3) the top of the underlying salt horizon is at least 500 m below the center of the dome, with no exposures of salt in the dome to support the possibility that a salt diapir has ascended through it; (4) sedimentary strata in the center are significantly imbricated by top-to-the-center thrust faulting and are complexly folded; (5) top-to-the-center low-angle normal faults are found at the perimeter of the structure; and (6) clastic dikes are widespread. The scarcity of melt rocks and shock fabrics is attributed to approximately 0.5 km of erosion; the structures of the dome reflect processes of complex crater development at a depth of about 0.5 km below the crater floor. Based on mapping and kinematic analysis, we infer that the dome formed mainly by centerward motion of rock units along listric faults. Outcrop-scale folding and upturning of beds, especially common in the center, largely resulted from this motion. In addition, we have detected some centerward motion of fault-bounded wedges resulting from displacements on subhorizontal faults that conjoin and die out within horizontal bedding in the perimeter of the structure. Collectively, the observed deformation accounts for the creation of both the central uplift and the encircling ring syncline.

  19. Subaqueous, basaltic lava dome and carapace breccia on King George Island, South Shetland Islands, Antarctica

    NASA Astrophysics Data System (ADS)

    Smellie, J. L.; Millar, I. L.; Rex, D. C.; Butterworth, P. J.

    On King George Island during latest Oligocene/earliest Miocene time, submarine eruptions resulted in the emplacement of a small (ca. 500m estimated original diameter) basalt lava dome at Low Head. The dome contains a central mass of columnar rock enveloped by fractured basalt and basalt breccia. The breccia is crystalline and is a joint-block deposit (lithic orthobreccia) interpreted as an unusually thick dome carapace breccia cogenetic with the columnar rock. It was formed in situ by a combination of intense dilation, fracturing and shattering caused by natural hydrofracturing during initial dome effusion and subsequent endogenous emplacement of further basalt melt, now preserved as the columnar rock. Muddy matrix with dispersed hyaloclastite and microfossils fills fractures and diffuse patches in part of the fractured basalt and breccia lithofacies. The sparse glass-rich clasts formed by cooling-contraction granulation during interaction between chilled basalt crust and surrounding water. Together with muddy sediment, they were injected into the dome by hydrofracturing, local steam fluidisation and likely explosive bulk interaction. The basalt lava was highly crystallised and degassed prior to extrusion. Together with a low effusion temperature and rapid convective heat loss in a submarine setting, these properties significantly affected the magma rheology (increased the viscosity and shear strength) and influenced the final dome-like form of the extrusion. Conversely, high heat retention was favoured by the degassed state of the magma (minimal undercooling), a thick breccia carapace and viscous shear heating, which helped to sustain magmatic (eruption) temperatures and enhanced the mobility of the flow.

  20. Shape and thermal modeling of the possible cryovolcanic dome Ganesa Macula on Titan: Astrobiological implications

    NASA Astrophysics Data System (ADS)

    Neish, C. D.; Lorenz, R. D.; O'Brien, D. P.; Cassini RADAR Team

    2005-08-01

    Observations of Titan by the Cassini spacecraft have revealed to us a world with an intricate and varied geology. In particular, there is evidence of extensive cryovolcanism. The 180 km structure Ganesa Macula observed in SAR imaging from Cassini's TA encounter in October 2004 resembles the pancake domes seen on Venus by the Magellan spacecraft and is comparable (in terms of years of planetary heatflow required to melt the lava volume) with the Deccan Traps on Earth. Cryovolcanism has important astrobiological implications, as it provides a means of exposing surface organics to liquid water. Aqueous chemistry permits Titan's hydrocarbons and nitriles to form more evolved and oxidized prebiotic species, such as amino acids and pyrimidines. In this work, we use Titan's observed backscatter function to model the radar appearance of domes of various shapes and heights to compare with the image of Ganesa: the SAR data are better fit by a ``spreading viscous drop" (``Huppert") shape than by one constrained by a skin strength (``Nye"). We then model the freezing of the model dome using a finite-element heat conduction code. Estimation of the dome height is presently underway, but even a dome only 1 km in height takes some 5 x 103 years to freeze for lava made entirely of liquid water, and 12 x 103 years for lava made of ammonia dihydrate. These timescales open a window for prebiotic chemistry far wider than can be explored in terrestrial laboratory experiments. This work was supported by the Cassini project.

  1. Deterministic precision finishing of domes and conformal optics

    NASA Astrophysics Data System (ADS)

    Shorey, Aric; Kordonski, William; Tricard, Marc

    2005-05-01

    In order to enhance missile performance, future window and dome designs will incorporate shapes with improved aerodynamic performance compared with the more traditional flats and spheres. Due to their constantly changing curvature and steep slopes, these shapes are incompatible with most conventional polishing and metrology solutions. Two types of a novel polishing technology, Magnetorheological Finishing (MRF®) and Magnetorheological (MR) Jet, could enable cost-effective manufacturing of free-form optical surfaces. MRF, a deterministic sub-aperture magnetically assisted polishing method, has been developed to overcome many of the fundamental limitations of traditional finishing. MRF has demonstrated the ability to produce complex optical surfaces with accuracies better than 30 nm peak-to-valley (PV) and surface micro-roughness less than 1 nm rms on a wide variety of optical glasses, single crystals, and glass-ceramics. The polishing tool in MRF perfectly conforms to the optical surface making it well suited for finishing this class of optics. A newly developed magnetically assisted finishing method MR JetTM, addresses the challenge of finishing the inside of steep concave domes and other irregular shapes. An applied magnetic field coupled with the properties of the MR fluid allow for stable removal rate with stand-off distances of tens of centimeters. Surface figure and roughness values similar to traditional MRF have been demonstrated. Combining these technologies with metrology techniques, such as Sub-aperture Stitching Interferometer (SSI®) and Asphere Stitching Interferometer (ASI®), enable higher precision finishing of the windows and domes today, as well as the finishing of future conformal designs.

  2. Textural evidence for origin of salt dome anhydrite cap rocks, Winnfield Dome, Louisiana

    SciTech Connect

    Ulrich, M.R.; Kyle, J.R.; Price, P.E.

    1985-02-01

    Textures within anhydrite cap rock are products of repeated cycles of halie dissolution and residual anhydrite accretion at tops of salt stocks. Quarrying operations at Winnfield dome have exposed extensive portions of the anhydrite cap rock zone. This zone is composed primarily of unoriented, xenoblastic anhydrite crystals in laminae less than 1 mm to several centimeters thick. Laminations are defined by thin, dark sulfide accumulations and pressure solution of anhydrite. Deformed, banded anhydrite clasts are contained locally within laminae. Multiple-laminated, concave downward anhydrite mounds occur along some horizons. They may contain anhydrite breccia fragments or sulfides. Coarsely crystalline salt mounds, containing disseminated idioblastic anhydrite also occur along horizons. Mound morphologies vary from tall and thin to broad and squat; maximum dimensions range from less than 0.5 to about 2.0 m. These moundlike structures are related spatially and genetically. Moundlike structures are believed to form from salt spines along the salt-anhydrite contact. As the spine dissolves through several cycles of dissolution and accretion, a laminated anhydrite mound is preserved; if the spine becomes isolated from dissolution, then a salt inclusion is preserved. Anhydrite beds within the Louann Salt, deformed during diapirism, are preserved as deformed anhydrite clasts. Steeply dipping, bedded anhydrite zones within the salt stock may produce brecciated anhydrite mounds when incorporated into the cap rock. Sulfides record the movement of metalliferous fluids through the salt-anhydrite contact.

  3. Volcanism on Venus: Large shields and major accumulations of small domes

    NASA Technical Reports Server (NTRS)

    Schaber, Gerald G.; Kozak, Richard C.

    1989-01-01

    The outer layers of the Venusian lithosphere appear to dissipate heat from the interior through mantle-driven thermal anomalies (hot spots, swells). As a result, Venus exhibits diverse forms of thin-skin tectonism and magmatic transfer to and extrusion from countless numbers of volcanic centers (e.g., shields, paterae, domes) and volcano-tectonic complexes (e.g., coronae, arachnoids). What is known about the distribution and morphologies of major Venusian shields is summarized, and the evidence for possible structural control of major accumulations as long as 5000 km of small volcanic domes is described.

  4. Exploring the possibility of developing a plastic missile dome for near-infrared transmission

    NASA Astrophysics Data System (ADS)

    Leuw, David H.

    1993-08-01

    The possibility was investigated of developing a missile dome from a transparent plastic for near infra-red transmission by which the windows form an integral part of it. The environmental requirements of the dome were severe as it had to stand up to a velocity in excess of 2 Mach at zero altitude without diminishing its transparency and thus, its optical performance. Several promising plastic candidates were investigated in a hot-wind tunnel and their eventual optical degradation was measured. Special coatings against EMI and reflection losses were applied resisting the high temperature and aero-dynamic pressure occurring during flight. Results of these experiments are given.

  5. Volcanism on Venus: Large shields and major accumulations of small domes

    NASA Astrophysics Data System (ADS)

    Schaber, Gerald G.; Kozak, Richard C.

    The outer layers of the Venusian lithosphere appear to dissipate heat from the interior through mantle-driven thermal anomalies (hot spots, swells). As a result, Venus exhibits diverse forms of thin-skin tectonism and magmatic transfer to and extrusion from countless numbers of volcanic centers (e.g., shields, paterae, domes) and volcano-tectonic complexes (e.g., coronae, arachnoids). What is known about the distribution and morphologies of major Venusian shields is summarized, and the evidence for possible structural control of major accumulations as long as 5000 km of small volcanic domes is described.

  6. Morphometrical and geochronological constraints on the youngest eruptive activity in East-Central Europe at the Ciomadul (Csomád) lava dome complex, East Carpathians

    NASA Astrophysics Data System (ADS)

    Karátson, Dávid; Telbisz, Tamás; Harangi, Szabolcs; Magyari, Enikő; Dunkl, István; Kiss, Balázs; Jánosi, Csaba; Veres, Daniel; Braun, Mihály; Fodor, Emőke; Biró, Tamás; Kósik, Szabolcs; von Eynatten, Hilmar; Lin, Ding

    2013-04-01

    The timing of Late Pleistocene volcanic activity of the Ciomadul (Csomád) dacitic lava dome complex, site of the youngest eruptions in the Carpathians, has been constrained by morphometric analysis and radiometric chronology. Peléan domes and asymmetric domes/coulées built up the volcano, including the central edifice that hosts the youngest twin craters of Mohoş (Mohos) peat bog and lake St. Ana (Szent Anna). A comparative digital elevation model (DEM)-based morphometric analysis of lava domes (29 worldwide examples including 5 domes from Ciomadul) shows that it is the mean slope of the upper dome flank that correlates best with age. Although the logarithmic relationship is only moderately strong (R = 0.80), slope characteristics of the Ciomadul domes fit to those of 10-100 ka old domes. These young ages contradict the previous K/Ar dates giving as old as 1 Ma ages on a number of domes, but are supported by ongoing U-Pb and (U-Th)/He zircon dating. The latter methods constrain the whole volcanic activity to the past 250 ka and the emplacement of most lava domes within the period of 150-100 ka. The volcanism at Ciomadul produced alternating effusive and explosive eruptions including lava dome collapses and successive crater formations. The latest, possibly subplinian explosive event formed the well-preserved St. Ana crater. Radiocarbon dating of organic remains from a sediment core that reached 11 m into the lacustrine infill of St. Ana suggests that the crater was formed prior to 26,000 years BP.

  7. A Look Inside Rotating Rubble-Pile Asteroids Spun to Disruption

    NASA Astrophysics Data System (ADS)

    Sanchez Lana, Diego; Scheeres, Daniel J.

    2014-11-01

    Driven by the images obtained by different space missions to small asteroids, during the last few years different researchers have used self-gravitating granular mechanics codes for the simulation of small rubble-pile asteroids. One of the many topics of research has been the response of these bodies to rotational evolution due to YORP, specifically the deformation and ultimate disruption of small bodies due to elevated angular velocities.In this research we use self-gravitating aggregates formed by thousands of spheres and a soft-sphere granular dynamics code to explore the effect of the variation of two parameters, friction angle and tensile strength, on their disruption process. The aggregates were slowly spun up to disruption controlling for friction angle, cohesion and global shape. How much each aggregate deformed before disruption was directly related to the angle of friction. The greater it was, the less the aggregate deformed before disruption. Cohesive forces controlled the mode of disruption and maximum spin rate, showing that the aggregates could disrupt by shedding particles or groups of particles from the equatorial region. For high values of tensile strength, the pieces that detached from the initial aggregate were sizable enough for the disruption process to be seen as a fission. This implies that the change from shedding to fission is continuous and therefore, they should not be seen as different processes but just as two ends of the spectrum.A closer look at the spherical aggregates showed that the reshaping of the bodies was not symmetrical. A granular aggregate cannot be completely homogeneous unless its particles are arranged in a crystalline structure, something we avoided. This resulted in an asymmetrically reshaped body, similar to that of 1999 KW4 (at times forming a binary system). For ellipsoidal aggregates, this meant the formation of tear-drop shapes and pairs. The failing of the granular structure is ultimately controlled by the inter

  8. Highly Symmetric and Congruently Tiled Meshes for Shells and Domes

    PubMed Central

    Rasheed, Muhibur; Bajaj, Chandrajit

    2016-01-01

    We describe the generation of all possible shell and dome shapes that can be uniquely meshed (tiled) using a single type of mesh face (tile), and following a single meshing (tiling) rule that governs the mesh (tile) arrangement with maximal vertex, edge and face symmetries. Such tiling arrangements or congruently tiled meshed shapes, are frequently found in chemical forms (fullerenes or Bucky balls, crystals, quasi-crystals, virus nano shells or capsids), and synthetic shapes (cages, sports domes, modern architectural facades). Congruently tiled meshes are both aesthetic and complete, as they support maximal mesh symmetries with minimal complexity and possess simple generation rules. Here, we generate congruent tilings and meshed shape layouts that satisfy these optimality conditions. Further, the congruent meshes are uniquely mappable to an almost regular 3D polyhedron (or its dual polyhedron) and which exhibits face-transitive (and edge-transitive) congruency with at most two types of vertices (each type transitive to the other). The family of all such congruently meshed polyhedra create a new class of meshed shapes, beyond the well-studied regular, semi-regular and quasi-regular classes, and their duals (platonic, Catalan and Johnson). While our new mesh class is infinite, we prove that there exists a unique mesh parametrization, where each member of the class can be represented by two integer lattice variables, and moreover efficiently constructable. PMID:27563368

  9. Sediment distribution about salt domes and ridges on Louisiana slope

    SciTech Connect

    Lowrie, A.

    1984-09-01

    Salt ridges and domes underlie much of the present Louisiana slope. The bathymetric expression of underlying salt could be either a mound or a flattening of the normal rate of descent down the slope. The mounded salt features form barriers to the gravity-driven sediments from the shelf break. Much industrial research has been done in the search for reservoir sands about such an obstruction. Parallel-bedded sediments from foredrifts on the upcurrent side of a seamount. These foredrift sediments were deposited where the prevailing ocean bottom currents were locally decelerated by the obstructing seamount. Moats are found on the sides of the obstruction and are the result of erosion or nondeposition owing to acceleration of deflected waters. Leedrifts are found on the downcurrent side of the obstruction. Current gyres result from deceleration of accelerated currents along the obstruction's flanks, and a complex sedimentation pattern results. Flow over the obstruction's top is determined by size and shape of the obstruction relative to size and velocity of the bottom-following current. A turbulent wave will be set up which may have sufficient amplitude to influence sedimentation on the downcurrent side. If ocean bottoms currents equal gravity-driven terrigenous sediment movement and seamounts equal salt domes and ridges, then the result of deep ocean surveys are directly applicable to sedimentation on slopes with underlying salt basement. The salt-related sedimentation pattern of the present slope should be applicable to similar paleoenvironments.

  10. Charged nano-domes and bubbles in epitaxial graphene

    NASA Astrophysics Data System (ADS)

    Ben Gouider Trabelsi, A.; Kusmartsev, F. V.; Robinson, B. J.; Ouerghi, A.; Kusmartseva, O. E.; Kolosov, O. V.; Mazzocco, R.; Gaifullin, Marat B.; Oueslati, M.

    2014-04-01

    For the first time, new epitaxial graphene nano-structures resembling charged ‘bubbles’ and ‘domes’ are reported. A strong influence, arising from the change in morphology, on the graphene layer’s electronic, mechanical and optical properties has been shown. The morphological properties of these structures have been studied with atomic force microscopy (AFM), ultrasonic force microscopy (UFM) and Raman spectroscopy. After initial optical microscopy observation of the graphene, a detailed description of the surface morphology, via AFM and nanomechanical UFM measurements, was obtained. Here, graphene nano-structures, domes and bubbles, ranging from a few tens of nanometres (150-200 nm) to a few μm in size have been identified. The AFM topographical and UFM stiffness data implied the freestanding nature of the graphene layer within the domes and bubbles, with heights on the order of 5-12 nm. Raman spectroscopy mappings of G and 2D bands and their ratio confirm not only the graphene composition of these structures but also the existence of step bunching, defect variations and the carrier density distribution. In particular, inside the bubbles and substrate there arises complex charge redistribution; in fact, the graphene bubble-substrate interface forms a charged capacitance. We have determined the strength of the electric field inside the bubble-substrate interface, which may lead to a minigap of the order of 5 meV opening for epitaxial graphene grown on 4H-SiC face-terminated carbon.

  11. Historical review: viruses, crystals and geodesic domes.

    PubMed

    Morgan, Gregory J

    2003-02-01

    In the mid 1950s, Francis Crick and James Watson attempted to explain the structure of spherical viruses. They hypothesized that spherical viruses consist of 60 identical equivalently situated subunits. Such an arrangement has icosahedral symmetry. Subsequent biophysical and electron micrographic data suggested that many viruses had >60 subunits. Drawing inspiration from architecture, Donald Caspar and Aaron Klug discovered a solution to the problem - they proposed that spherical viruses were structured like miniature geodesic domes. PMID:12575996

  12. Remote Control of the CFHT Dome Shutter

    NASA Astrophysics Data System (ADS)

    Look, Ivan; Roberts, Larry; Vermeulen, Tom; Taroma, Ralph; Matsushige, Grant

    2011-03-01

    Several years ago CFHT proposed developing a Remote Observing Environment aimed at producing Science Observations at their Facility on Mauna Kea from their Headquarters in Waimea, HI. This Remote Observing Project commonly referred to as OAP (Observatory Automation Project) was completed at the end of January 2011 and has been providing the majority of Science Data since. My poster will attempt to provide Design Information on the Dome Shutter, which is both Controlled and Monitored Remotely from Waimea. The Dome Shutter Control System incorporates an upgraded Allen-Bradley PLC processor (SLC 5/05), which provides Remote Operation and Monitoring of the existing System. Several earlier upgrade projects were integrated to provide improvement to the Shutter System such as PLC Control, System Feedback, and Safety Features. This particular upgrade provides Remote capability, CFHT developed Control GUI, and Remote monitoring that promise to deliver a more versatile, visual, and safer Shutter Operation. The Dome Shutter Control System provides three modes of Operation namely; Remote, Integration, and Local. The Control GUI is used to operate the Shutter remotely. Integration mode is provided to develop PLC software code and is performed by connecting a Laptop directly to the Shutter Control Panel. Local mode is retained to provide Remote Lockout (No Remote Control), which allows Shutter control ONLY via the existing Electrical Panel. This mode is primarily intended for Shutter maintenance and troubleshooting. The Dome Shutter remains the first Line-of-Defense for Telescope protection due to inclement weather and so special attention was considered during Remote development. The Shutter has been equipped with an Autonomous Shutdown sequence in the event of Power or Network failure. If Loss of HELCO Power or Start-up of our Stand-by Diesel Generator is detected; a planned timing sequence will Close the Shutter Automatically. Likewise, an internal CFHT Network heartbeat was

  13. Fabric and texture at Siple Dome, Antarctica

    USGS Publications Warehouse

    Diprinzio, C.L.; Wilen, L.A.; Alley, R.B.; Fitzpatrick, J.J.; Spencer, M.K.; Gow, A.J.

    2005-01-01

    Preferred c-axis orientations are present in the firn at Siple Dome, West Antarctica, and recrystallization begins as shallow as 200 m depth in ice below -20??C, based on digital analysis of c-axis fabrics, grain-sizes and other characteristics of 52 vertical thin sections prepared in the field from the kilometer-long Siple Dome ice core. The shallowest section analyzed, from 22 m, shows clustering of c axes toward the vertical. By 200 m depth, girdle fabric and other features of recrystallized ice are evident in layers (or regions), separated by layers (regions) of typically finer-grained ice lacking evidence of recrystallization. Ice from about 700-780 m depth, which was deposited during the last ice age, is especially fine-grained, with strongly vertical c axes, but deeper ice shows much larger crystals and strong evidence of recrystallization. Azimuthal asymmetry of some c-axis fabrics, trends in grain-size, and other indicators reveal additional information on processes and history of ice flow at Siple Dome.

  14. Underwater Calibration of Dome Port Pressure Housings

    NASA Astrophysics Data System (ADS)

    Nocerino, E.; Menna, F.; Fassi, F.; Remondino, F.

    2016-03-01

    Underwater photogrammetry using consumer grade photographic equipment can be feasible for different applications, e.g. archaeology, biology, industrial inspections, etc. The use of a camera underwater can be very different from its terrestrial use due to the optical phenomena involved. The presence of the water and camera pressure housing in front of the camera act as additional optical elements. Spherical dome ports are difficult to manufacture and consequently expensive but at the same time they are the most useful for underwater photogrammetry as they keep the main geometric characteristics of the lens unchanged. Nevertheless, the manufacturing and alignment of dome port pressure housing components can be the source of unexpected changes of radial and decentring distortion, source of systematic errors that can influence the final 3D measurements. The paper provides a brief introduction of underwater optical phenomena involved in underwater photography, then presents the main differences between flat and dome ports to finally discuss the effect of manufacturing on 3D measurements in two case studies.

  15. Volumetric Changes of the Bezymianny Dome: Insights on the Eruptive Behavior

    NASA Astrophysics Data System (ADS)

    Ushakov, S. V.; Dvigalo, V. N.; Izbekov, P. E.

    2010-12-01

    Bezymianny Volcano, Kamchatka erupted explosively on March 30, 1956 after ca. 1000 period of quiescence. The collapse of the eastern flank of the volcano followed by a directed blast and 4-hour-long explosive activity excavated a 1.3x2.5 km horse-shoe crater open to the East. The eruption continued through extrusive activity, which by the end of the 1956 formed a 300-m-tall dome in the middle of the crater. The extrusive dome growth accompanied by frequent partial collapses and block-and-ash flows dominated through mid 70s, when short vigorous explosions from central vent followed by effusions of viscous lava flows gradually became the prevailed eruption mechanisms. The volumetric changes of the Bezymianny dome have been measured by routine aerial surveys and stereophotogrammetry since 1956. In early 90s the observations has been interrupted due to the lack of funding. Support from the PIRE-Kamchatka project allowed us to resume Bezymianny dome aerial surveys and make three consecutive measurements on June 31, 2006, September 5, 2009, and July 24, 2010. The acquired data was used to generate high resolution digital elevation models of the dome area and to determine morphological and volumetric changes in response to the most recent eruptive activity. Our observations indicate that by 2005-2006 a new crater formed at the summit of the dome. This crater served as a vent for each of seven explosive-effusive events that occurred during 2006-2010. Volumetric changes due to extrusive activity between early 90s and 2006 and during 2006-2010 have been minimal and only occurred in the crater area. At present the dome is entirely covered by lava flows and pyroclastic flow deposits erupted from the central vent. The average annual increase of the dome volume for the 2006-2010 period was 6.8x10^6 cubic meters. Pyroclastic deposits filled the area between the dome and the 1956 crater rim, elevated the flow of the 1956 crater, and reduced the height of the rim above the floor to

  16. Finite Element Model of a Two-Phase Non-Newtonian Thixotropic Fluid: Mount St. Helens Lava Dome

    NASA Astrophysics Data System (ADS)

    Vincent, P.; Zevada, P.

    2011-12-01

    Extrusion of highly viscous lavas that spread laterally and form lava domes in the craters of large volcanoes is associated with significant volcanic hazards. Gas overpressure driven fragmentation of the lava dome or collapse and slumping of marginal sections or the entire mass of the dome can trigger dangerous pyroclastic flows that threaten surrounding populations up to tens of kilometers away. The rate of lava dome growth in the mature state of the dome evolution is often oscillatory. Relatively quiescent episodes are terminated by renewed extrusion and emplacement of exogenous "lobes" or "spines" of lava on the surface of the dome. Emplacement of new lobes is preceded by pressurization of magma in the magmatic conduit that can trigger volcanic eruptions and is preceded by crater floor deformation (e.g. Swanson and Holcombe, 1990). This oscillatory behavior was previously attributed primarily to crystallization kinetics and gas exsolution generating cyclic overpressure build-ups. Analogue modeling of the lava domes has revealed that the oscillatory growth rate can be reproduced by extrusion of isothermal, pseudoplastic and thixotropic plaster of Paris (analogue material for the magma) on a sand layer (analogue material for the unconsolidated deposits of the crater floor). The patterns of dome growth of these models closely correspond to both the 1980-1985 and 2004-2005 growth episodes of Mt. St. Helens lava dome (Swanson and Holcombe, 1990; Major et al., 2005). They also suggest that the oscillatory growth dynamics of the lavas can be explained by the mechanical interaction of the non-Newtonian magma with the frictional and deformable substrate below the lava dome rather than complex crystallization kinetics (e.g. Melnik and Sparks, 1999). In addition, these results suggest that the renewed growth episode of Mt. St. Helens dome in 2006 could be associated with an even higher degree of magma pressurization in the conduit than occurred during the 1980 - 1986

  17. Dynamics of cooling viscoplastic domes

    NASA Astrophysics Data System (ADS)

    Balmforth, N. J.; Craster, R. V.; Sassi, R.

    2004-01-01

    A variety of problems in engineering and geology involve spreading cooling non-Newtonian fluids. If the fluid is relatively shallow and spreads slowly, lubrication-style asymptotic approximations can be used to build reduced models for the spreading dynamics. The centrepiece of such models is a nonlinear diffusion equation for the local fluid thickness, and ideally this should become coupled to a correspondingly simple equation determining the local temperature field. However, when heat diffuses relatively slowly as the fluid flows, we cannot usefully reduce the temperature equation, and the asymptotic reduction couples the local thickness equation to an advection diffusion equation that crucially involves diffusion in the vertical. We present an efficient computational algorithm for numerically solving this more complicated type of lubrication model, and describe a suite of solutions that illustrate the dynamics captured by the model in the case of an expanding Bingham fluid with a temperature-dependent viscosity. Based on these solutions, we evaluate two simpler models that further approximate the temperature equation: a vertically isothermal theory, and a ‘skin theory’. The latter is based on the integral-balance method of heat-transfer theory, and demands that the vertical structure of the temperature field has the form of an advancing boundary layer, or skin. The vertically isothermal model performs well when the thermal conductivity is relatively large. The skin theory reproduces the full dynamics qualitatively, if not quantitatively, for all thermal conductivities. The main errors in both models arise near the fluid edge, where the numerical solutions show that chilled fluid is overridden as the fluid expands, creating an underlying collar of cold material. Encouraged by the success of the skin model, we extend the theory by incorporating extensional stresses in the skin, which emerge when cooling induces an extreme rheological change in the material

  18. Cyclic pressurisation of lava dome rocks. Laboratory results and implications for lava dome monitoring

    NASA Astrophysics Data System (ADS)

    Dainty, M. L.; Smith, R.; Sammonds, P.; Meredith, P. G.

    2009-12-01

    Lava domes are frequently subjected to cyclic heating and pressurisation. These processes may weaken the dome rocks, leading to collapse of the lava dome or explosion and extrusion events caused by unplugging of the magma conduit. By subjecting lava dome rocks to cyclic loading and heating in the laboratory, we can investigate how these processes affect the elastic moduli and strength of the dome rocks. These elastic moduli are crucial parameters for determining how the deformation measured at a volcano relates to the pressurisation and stress. Recording acoustic emissions (AE) during these cyclic loading tests can reveal when the cracking and damage occurs and indicate expected patterns in seismicity during cyclic pressurisation of lava domes. For this laboratory investigation of cyclic loading and heating of lava dome rocks, samples with four different extrusion dates within the 2004-2008 eruption of Mount St Helens were used. This allowed us to also investigate how the mechanical properties of this lava dome changed with time. For each timed sample, four 62.5 mm long x 25 mm diameter cores were deformed in uniaxial compression. The first sample was simply loaded to failure at a constant rate, to obtain the strength and elastic moduli. Of the remaining three cores from each sample, one was slowly heated and cooled to 900°C and one to 600°C (and the other not heated). The three cores from each sample were then initially loaded to 40 MPa at a constant rate and then unloaded to 5 MPa. They were then sequentially reloaded and unloaded at the same rate with the peak stress in each cycle increased by 5 MPa until failure. For all samples, the core loaded to failure with no cycling was stronger than those subjected to cyclic loading. However, there was no weakening or reduction in elastic moduli seen for the samples subjected to a heating cycle before cyclic loading. The sample extruded in 2004 compared to the later ones from 2005 and 2006, was the weakest at 60 to 70

  19. Surface valence transformation during thermal activation and hydrogenation thermodynamics of Mg-Ni-Y melt-spun ribbons

    NASA Astrophysics Data System (ADS)

    Zhang, Tiebang; Song, Wenjie; Kou, Hongchao; Li, Jinshan

    2016-05-01

    In this work, phase compositions and chemical valence states on the surface and subsurface of Mg67Ni33-xYx (x = 0, 1, 3, 6) ribbons during thermal activation have been investigated by X-ray photoelectron spectroscopy (XPS). The results indicate that the surface contaminants of melt-spun ribbons are mainly MgO, NiO, Y2O3 and organics. The oxides/hydroxides of Mg67Ni33-xYx (x = 0, 1, 3, 6) melt-spun ribbons are removed from the surface during thermal activation. Surface chemical valence firstly transforms from oxidized state to the metallic one during thermal activation, which accounts for hydrogenation of Mg67Ni33-xYx melt-spun ribbons. Hydrogen absorption capacities of Mg67Ni33-xYx (x = 0, 1, 3, 6) melt-spun ribbons are enhanced with the increase of cycle numbers during thermal activation. Hydrogenation thermodynamics of activated Mg67Ni33-xYx (x = 0, 1, 3, 6) melt-spun ribbons have been also compared and correlated with the surface valence transformation. The obtained enthalpy of hydride formation is -55.5, -50.5, -46.9 and -48.6 kJ/mol for Mg67Ni33-xYx melt-spun ribbons with x = 0, 1, 3 and 6, respectively.

  20. Was the millisecond pulsar in SN1987A spun up or born spinning fast?

    NASA Astrophysics Data System (ADS)

    Woosley, S. E.; Chevalier, R. A.

    1989-03-01

    It is argued here that the millisecond pulsar in SN1987A has been spun up by accretion. The accreted angular momentum in this case comes from the mixed mantle and helium core of the ejecta, of which roughly 0.1 solar mass fell back during the first day after the explosion. This sizable mass, and hence angular momentum, of the reimploded material is at least partly a consequence of the blue supergiant nature of the progenitor star.

  1. Was the millisecond pulsar in SN1987A spun up or born spinning fast?

    NASA Technical Reports Server (NTRS)

    Woosley, S. E.; Chevalier, R. A.

    1989-01-01

    It is argued here that the millisecond pulsar in SN1987A has been spun up by accretion. The accreted angular momentum in this case comes from the mixed mantle and helium core of the ejecta, of which roughly 0.1 solar mass fell back during the first day after the explosion. This sizable mass, and hence angular momentum, of the reimploded material is at least partly a consequence of the blue supergiant nature of the progenitor star.

  2. Measurement of high-birefringent spun fiber parameters using short-length fiber Bragg gratings.

    PubMed

    Vasiliev, S A; Przhiyalkovsky, Ya V; Gnusin, P I; Medvedkov, O I; Dianov, E M

    2016-05-30

    Spectral polarization characteristics of short-length fiber Bragg gratings UV-written in a highly-birefringent spun-fiber have been investigated. Based on the analysis of the characteristics the technique for measuring the built-in linear phase birefringence as well as the spin period in this fiber type has been suggested. In this method the birefringence dispersion is excluded and therefore the built-in linear phase birefringence can be measured with an improved accuracy. PMID:27410060

  3. Petrology of sapphirine-bearing gedrite-cordierite gneiss, Okanogan dome, Washington USA, and implications for gneiss dome tectonics

    NASA Astrophysics Data System (ADS)

    Kruckenberg, S. C.; Whitney, D. L.

    2007-12-01

    The northern Cordilleran migmatite domes (Thor-Odin, Valhalla, Okanogan) contain Mg-Al-rich (Si-poor) orthoamphibole-cordierite gneiss as layers and lenses surrounded by quartzofeldspathic migmatite. The Mg-Al- rich rocks contain assemblages and reaction textures that provide information about metamorphic conditions during the tectonic evolution of the migmatite dome. In the Okanogan dome, gedrite + anorthite + cordierite + spinel + sapphirine +/- kyanite +/- hornblende assemblages of the Tunk Creek Amphibolite indicate T > 700- 800 degrees C. This Okanogan unit structurally overlies a migmatite domain dominated by diatexite. In contrast to gedrite-cordierite gneiss in other northern Cordilleran domes, the Okanogan rocks occur in a discontinuous kilometer-scale unit rather than small pods; are more calcic; and lack garnet. In addition, kyanite did not transform to sillimanite, and spinel occurs most commonly as a blocky matrix phase rather than as vermicules in symplectite. The differences in textures of gedrite-cordierite gneiss in the Cordilleran domes may in part be related to differences in bulk composition, but are also likely related to differences in tectonic evolution. The Okanogan dome is located at a greater distance from the Rocky Mountain foreland-hinterland boundary, a major crustal boundary that localized and therefore maximized vertical flow (decompression) in domes adjacent to it. The Okanogan dome, ~200 km west of the boundary, may have experienced less isothermal decompression during dome emplacement compared to domes located closer to the boundary, and therefore contains relict kyanite and only minor corona/symplectite development.

  4. Where is the Best Site on Earth? Domes A, B, C, and F, and Ridges A and B

    NASA Technical Reports Server (NTRS)

    Suanders, Will; Lawrence, Jon S.; Storey, John W. V.; Ashley, Michael C. B.; Kato, Seiji; Minnis, Patrick; Winker, David M.; Liu, Guiping; Kulesa, Craig

    2009-01-01

    The Antarctic plateau contains the best sites on earth for many forms of astronomy, but none of the existing bases were selected with astronomy as the primary motivation. In this paper, we try to systematically compare the merits of potential observatory sites. We include South Pole, Domes A, C and F, and also Ridge B (running NE from Dome A), and what we call Ridge A (running SW from Dome A). Our analysis combines satellite data, published results and atmospheric models, to compare the boundary layer, weather, free atmosphere, sky brightness, pecipitable water vapour, and surface temperature at each site. We find that all Antarctic sites are likely compromised for optical work by airglow and aurorae. Of the sites with existing bases, Dome A is the best overall; but we find that Ridge A offers an even better site. We also find that Dome F is a remarkably good site. Dome C is less good as a thermal infrared or terahertz site, but would be able to take advantage of a predicted OH hole over Antarctica during Spring.

  5. Spider silk fibers spun from soluble recombinant silk produced in mammalian cells.

    PubMed

    Lazaris, Anthoula; Arcidiacono, Steven; Huang, Yue; Zhou, Jiang-Feng; Duguay, Francois; Chretien, Nathalie; Welsh, Elizabeth A; Soares, Jason W; Karatzas, Costas N

    2002-01-18

    Spider silks are protein-based "biopolymer" filaments or threads secreted by specialized epithelial cells as concentrated soluble precursors of highly repetitive primary sequences. Spider dragline silk is a flexible, lightweight fiber of extraordinary strength and toughness comparable to that of synthetic high-performance fibers. We sought to "biomimic" the process of spider silk production by expressing in mammalian cells the dragline silk genes (ADF-3/MaSpII and MaSpI) of two spider species. We produced soluble recombinant (rc)-dragline silk proteins with molecular masses of 60 to 140 kilodaltons. We demonstrated the wet spinning of silk monofilaments spun from a concentrated aqueous solution of soluble rc-spider silk protein (ADF-3; 60 kilodaltons) under modest shear and coagulation conditions. The spun fibers were water insoluble with a fine diameter (10 to 40 micrometers) and exhibited toughness and modulus values comparable to those of native dragline silks but with lower tenacity. Dope solutions with rc-silk protein concentrations >20% and postspinning draw were necessary to achieve improved mechanical properties of the spun fibers. Fiber properties correlated with finer fiber diameter and increased birefringence. PMID:11799236

  6. Neutron irradiation study of Nd-Fe-B permanent magnets made from melt-spun ribbons

    NASA Astrophysics Data System (ADS)

    Brown, R. D.; Cost, J. R.; Meisner, G. P.; Brewer, E. G.

    1988-11-01

    Radiation-induced changes in the magnetization of sintered Nd-Fe-B permanent magnets are known to vary widely among specimens produced by different manufacturers. Samples of Nd-Fe-B MAGNEQUENCH magnets, which are made from melt-spun ribbons, have not been studied and show a much reduced sensitivity to neutron irradiation than do sintered Nd-Fe-B magnets. All melt-spun ribbon-based MAGNEQUENCH magnets, i.e., epoxy-bonded, hot-pressed, and die-upset magnets, show essentially the same slow decrease in magnetic remanence with neutron dose. Measurements of the open-circuit remanence Br/Br 0 at various times during the irradiation show a decay of only 1.5% of the preirradiated value for the MAGNEQUENCH magnets after 1 h of irradiation, or a dose of 1.4×1016 neutrons/cm2, compared to a 4.6% drop in remanence for the best sintered Nd-Fe-B magnet (Sumitomo 30H) with the same irradiation dose. Moreover, after 5.3 h of irradiation, the remanence drops by only 3% for the MAGNEQUENCH magnets. Magnets made from melt-spun ribbons are thus the least sensitive to neutron irradiation so far measured for Nd-Fe-B permanent magnets, but are somewhat more sensitive than samarium-cobalt magnets.

  7. The nature and formation of cristobalite at the Soufrière Hills volcano, Montserrat: implications for the petrology and stability of silicic lava domes

    NASA Astrophysics Data System (ADS)

    Horwell, Claire J.; Williamson, Ben J.; Llewellin, Edward W.; Damby, David E.; Le Blond, Jennifer S.

    2013-03-01

    Cristobalite is commonly found in the dome lava of silicic volcanoes but is not a primary magmatic phase; its presence indicates that the composition and micro-structure of dome lavas evolve during, and after, emplacement. Nine temporally and mineralogically diverse dome samples from the Soufrière Hills volcano (SHV), Montserrat, are analysed to provide the first detailed assessment of the nature and mode of cristobalite formation in a volcanic dome. The dome rocks contain up to 11 wt.% cristobalite, as defined by X-ray diffraction. Prismatic and platy forms of cristobalite, identified by scanning electron microscopy (SEM), are commonly found in pores and fractures, suggesting that they have precipitated from a vapour phase. Feathery crystallites and micro-crystals of cristobalite and quartz associated with volcanic glass, identified using SEM-Raman, are interpreted to have formed by varying amounts of devitrification. We discuss mechanisms of silica transport and cristobalite formation, and their implications for petrological interpretations and dome stability. We conclude: (1) that silica may be transported in the vapour phase locally, or from one part of the magmatic system to another; (2) that the potential for transport of silica into the dome should not be neglected in petrological and geochemical studies because the addition of non-magmatic phases may affect whole rock composition; and (3) that the extent of cristobalite mineralisation in the dome at SHV is sufficient to reduce porosity—hence, permeability—and may impact on the mechanical strength of the dome rock, thereby potentially affecting dome stability.

  8. The origin of the silicic domes in the Macolod Corridor, Philippines

    NASA Astrophysics Data System (ADS)

    Flood, T. P.; Patino, L. C.; Vogel, T. A.; Arcilla, C.; Stimac, J. A.; Maximo, R. R.; Arpa, M. B.

    2002-12-01

    The petrogenesis of silicic magmas in areas that do not contain continental crust is often unclear. This study examines the composition of domes associated with Mount Makiling stratovolcano, Philippines, to understand the generation of silicic magmas, in an island arc setting. Makiling volcano and associated domes are located in the Macolod Corridor. The corridor is a tectonic depression between the West Luzon Arc (produced by east dipping South China Sea plate) and the East Luzon Arc (produced by the west dipping Philippine Sea plate) with numerous volcanic features. The volcanism in this part of the Macolod Corridor has occurred sporadically over at least the past million years. Sampling of Makiling volcano indicates a continuous range in composition from basaltic andesite to dacite. The range in composition in the domes is wider, from basalt to rhyolite. The chemical variation in samples from individual domes is small, and may be an indication of monogenetic nature of the magmatic activity. Howerver, most of the domes have similar compositions, with SiO2 modes of 70% and with little variation of other chemical parameters that may indicate derivation from a larger silicic magma system. At least one dome has bimodal composition, one set of samples ranges in composition form basalts-basaltic andesite and the other set of samples consists of dacites. There is a dubious association among the magmas from the Macolod corridor with subduction zone magmatism, the rocks from Makiling volcano and most of those sampled from the domes are calc-alkaline with large Nb and Ti depletion on spider diagrams. Conversely, one dome has tholeiitic characteristics with higher FeO/MgO ratios for a given SiO2 content. The major and minor elements data in the samples from Makiling volcano plot on trends that show little scatter. All the samples follow on a single trend for Mg, Fe, and Ca. Though, for other elements (Ti, Al, Sr, Na, K, Rb, and Zr) the samples from the northeastern part of

  9. Smooth Muscle Cell Alignment and Phenotype Control by Melt Spun Polycaprolactone Fibers for Seeding of Tissue Engineered Blood Vessels

    PubMed Central

    Agrawal, Animesh; Lee, Bae Hoon; Irvine, Scott A.; An, Jia; Bhuthalingam, Ramya; Singh, Vaishali; Low, Kok Yao; Chua, Chee Kai; Venkatraman, Subbu S.

    2015-01-01

    A method has been developed to induce and retain a contractile phenotype for vascular smooth muscle cells, as the first step towards the development of a biomimetic blood vessel construct with minimal compliance mismatch. Melt spun PCL fibers were deposited on a mandrel to form aligned fibers of 10 μm in diameter. The fibers were bonded into aligned arrangement through dip coating in chitosan solution. This formed a surface of parallel grooves, 10 μm deep by 10 μm across, presenting a surface layer of chitosan to promote cell surface interactions. The aligned fiber surface was used to culture cells present in the vascular wall, in particular fibroblasts and smooth muscle cells. This topography induced “surface guidance” over the orientation of the cells, which adopted an elongated spindle-like morphology, whereas cells on the unpatterned control surface did not show such orientation, assuming more rhomboid shapes. The preservation of VSMC contractile phenotype on the aligned scaffold was demonstrated by the retention of α-SMA expression after several days of culture. The effect was assessed on a prototype vascular graft prosthesis fabricated from polylactide caprolactone; VSMCs aligned longitudinally along a fiberless tube, whereas, for the aligned fiber coated tubes, the VSMCs aligned in the required circumferential orientation. PMID:26413093

  10. Identifying suitable "piercement" salt domes for nuclear waste storage sites

    SciTech Connect

    Kehle, R.

    1980-08-01

    Piercement salt domes of the northern interior salt basins of the Gulf of Mexico are being considered as permanent storage sites for both nuclear and chemically toxic wastes. The suitable domes are stable and inactive, having reached their final evolutionary configuration at least 30 million years ago. They are buried to depths far below the level to which erosion will penetrate during the prescribed storage period and are not subject to possible future reactivation. The salt cores of these domes are themselves impermeable, permitting neither the entry nor exit of ground water or other unwanted materials. In part, a stable dome may be recognized by its present geometric configuration, but conclusive proof depends on establishing its evolutionary state. The evolutionary state of a dome is obtained by reconstructing the growth history of the dome as revealed by the configuration of sedimentary strata in a large area (commonly 3,000 square miles or more) surrounding the dome. A high quality, multifold CDP reflection seismic profile across a candidate dome will provide much of the necessary information when integrated with available subsurface control. Additional seismic profiles may be required to confirm an apparent configuration of the surrounding strata and an interpreted evolutionary history. High frequency seismic data collected in the near vicinity of a dome are also needed as a supplement to the CDP data to permit accurate depiction of the configuration of shallow strata. Such data must be tied to shallow drill hole control to confirm the geologic age at which dome growth ceased. If it is determined that a dome reached a terminal configuration many millions of years ago, such a dome is incapable of reactivation and thus constitutes a stable storage site for nuclear wastes.

  11. Exhumation of high-pressure rocks in a Variscan migmatite dome (Montagne Noire, France)

    NASA Astrophysics Data System (ADS)

    Whitney, Donna; Roger, Francoise; Rey, Patrice; Teyssier, Christian

    2015-04-01

    of garnet rims presents a challenge for ascribing the zircon rim age to hydrothermal alteration. Of the 5 reported eclogite localities in the MN, 4 are located near a high-strain zone along the long axis of the dome and one is located in a shear zone at the SSW margin of the gneissic core. 2D and 3D numerical models show that migmatite domes may form in response to extension of the upper crust, as the partially molten deep crust ascends along a steep, axial high strain zone and then flows into subdomes flanking this zone, forming a double dome such as the MN. This mode of dome formation is an efficient mechanism for rapid exhumation of deep crust. Migmatite dome rocks equilibrate at LP/HT, but eclogite inclusion in migmatite preserve their deep origin, track exhumation, and inform the internal dynamics of domes. Domes like the MN demonstrate that the opportunistic low-viscosity deep crust flows readily to fill gaps created by extensional/ transtensional domains in the collapsing late-Variscan orogen.

  12. Numerical Simulation of Textile Composite Stamping On Double Dome

    SciTech Connect

    Xiongqi Peng; Zia Ur Rehman

    2011-05-04

    Stamping is one of the most effective ways to form textile composites in industry for providing high-strength, low-weight and cost-effective products. This paper presents a fully continuum mechanics-based approach for stamping simulation of textile fiber reinforced composites by using finite element (FE) method. A previously developed non-orthogonal constitutive model is used to represent the anisotropic mechanical behavior of textile composites under large deformation during stamping. Simulation are performed on a balanced plain weave composite with 0 deg./90 deg. and {+-}45 deg. as initial yarn orientation over a benchmark double dome device. Simulation results show good agreement with experimental output in terms of a number of parameters selected for comparison.

  13. Siple Dome: Is it in Steady State?

    NASA Astrophysics Data System (ADS)

    Pettit, E. C.; Waddington, E. D.; Nereson, N. A.; Zumberge, M. A.; Hamilton, G. S.

    2001-12-01

    Changes in the West Antarctic Ice Sheet since the end of the last ice age have implications for how we interpret its present behavior, in terms of both its stability and its record of climate history. Siple Dome, the ridge between Ice Streams C and D, is not presently thinning and is close to being in balance with present environmental conditions. We present three independent measurements of ice thickness change in the divide region of Siple Dome: a GPS surface horizontal strain network, fiber optic vertical strain measurements at depth, and precision GPS measurements of vertical motion of near-surface ice ("coffee-can" method). From the horizontal strain network, we calculate the divergence of the horizontal velocity. This divergence is equal to the gradient of vertical velocity at the surface and, with some assumptions about the distribution of strain rates with depth, we can calculate the vertical velocity at the surface. For steady state, the vertical velocity must be balanced by the local accumulation rate. The fiber optic instruments provide a profile of the relative vertical velocity with depth. We fit a theoretical vertical velocity pattern to these data and extrapolate to find the surface vertical velocity. Our third method (coffee-can) directly measures the vertical motion of a marker 20 meters deep using precision GPS and compares it with the local long-term rate of snow accumulation to calculate the net rate of ice sheet thickness change. All three methods reach the same conclusion: Siple Dome is currently very close to being in steady state. This result has two implications. First, ice dynamics models developed to interpret radar images or ice core data can assume steady state behavior, simplifying the models. Second, our result suggests that the central part of the Ross Embayment may have had a low-elevation profile during the late Holocene, even though other areas of the WAIS may have been thicker.

  14. Anatomy of a lava dome collapse: the 20 March 2000 event at Soufrière Hills Volcano, Montserrat

    NASA Astrophysics Data System (ADS)

    Carn, S. A.; Watts, R. B.; Thompson, G.; Norton, G. E.

    2004-03-01

    014863] and lacked precursory elevated seismic activity. We attribute the initiation of the 20 March 2000 collapse to a prolonged spell of heavy rainfall on the lava dome prior to and during the event. The precise causal mechanism remains controversial, though some combination of mechanical erosion and/or destabilization of a critically poised face of the lava dome, the action of pressurized steam or water on potential failure surfaces within the dome, rapid cooling of hot lava and small phreatic explosions seems likely. Anecdotal evidence exists for other rainfall-induced activity on Montserrat, and the triggering of explosive or pyroclastic flow activity by rainfall has been noted at dome-forming volcanoes elsewhere, including Merapi, Indonesia [Voight et al. (2000) J. Volcanol. Geotherm. Res. 100, 69-138], Unzen, Japan [Yamasato et al. (1997) Papers Meteorol. Geophys. 48], Santiaguito, Guatemala [Smithsonian Institution Global Volcanism Network Bull. 15 (1990)] and Mount St. Helens, USA [Mastin (1994) Geol. Soc. Am. Bull. 106, 175-185]. Hazard mitigation plans at dome-forming volcanoes would therefore benefit from the inclusion of meteorological forecasting and rain monitoring equipment, particularly in the tropics.

  15. Formation of lunar mare domes along crustal fractures: Rheologic conditions, dimensions of feeder dikes, and the role of magma evolution

    NASA Astrophysics Data System (ADS)

    Wöhler, Christian; Lena, Raffaello; Phillips, Jim

    2007-08-01

    In this study we examine a set of lunar mare domes located in the Hortensius/Milichius/T. Mayer region and in northern Mare Tranquillitatis with respect to their formation along crustal fractures, their rheologic properties, the dimensions of their feeder dikes, and the importance of magma evolution processes during dome formation. Many of these domes display elongated summit vents oriented radially with respect to major impact basins, and several dome locations are also aligned in these preferential directions. Analysis of Clementine UV/VIS and Lunar Prospector gamma ray spectrometer data reveals that the examined mare domes formed from low-Si basaltic lavas of high FeO and low to moderate TiO 2 content. Based on their morphometric properties (diameter, height, volume) obtained by photoclinometric and shape from shading analysis of telescopic CCD images, we derive rheologic quantities (lava viscosity during eruption, effusion rate, duration of the effusion process, magma rise speed) and the dimensions of the feeder dikes. We establish three rheologic groups characterised by specific combinations of rheologic properties and dike dimensions, where the most relevant discriminative parameter is the lava viscosity η. The first group is characterised by 10 Pas<η<10 Pas and contains the domes with elongated vents in the Milichius/T. Mayer region and two similar domes in northern Mare Tranquillitatis. The second group with 10 Pas<η<10 Pas comprises the very low aligned domes in northern Mare Tranquillitatis, and the third group with 10 Pas<η<10 Pas the relatively steep domes near Hortensius and in the T. Mayer region. The inferred dike dimensions in comparison to lunar crustal thickness data indicate that the source regions of the feeder dikes are situated within the upper crust for six of the domes in northern Mare Tranquillitatis, while they are likely to be located in the lower crust and in the upper mantle for the other examined domes. By comparing the time scale

  16. Dispersive thermohaline convection near salt domes: a case at Napoleonville Dome, southeast Louisiana, USA

    NASA Astrophysics Data System (ADS)

    Jamshidzadeh, Zahra; Tsai, Frank T.-C.; Ghasemzadeh, Hasan; Mirbagheri, Seyed Ahmad; Barzi, Majid Tavangari; Hanor, Jeffrey S.

    2015-08-01

    Density-driven flow around salt domes is strongly influenced by salt concentration and temperature gradients. In this study, a thermohaline convection numerical modeling is developed to investigate flow, salinity, and heat transport around salt domes under the impact of fluid dispersivity and variable density and viscosity. `Dispersive fluid flux of total fluid mass' is introduced to the density-driven flow equation to improve thermohaline modeling in porous media. The dispersive fluid flux term is derived to account for an additional fluid flux driven by the density gradient and mechanical dispersion. The model is first tested by a hypothetical salt-dome problem, where a circulation of flow is induced by an overpressure and density effect. The result shows a distinct salt-transport change due to the inclusion of the dispersive fluid flux and temperature effect. Then, the model is applied to investigate changes of groundwater flow, salinity, and heat transport near the west of Napoleonville salt dome, southeastern Louisiana, USA, due to a salt cavern failure. The result shows that an instant overpressure assumed to be created by the salt-cavern wall breach has little impact on salinity near the ground surface within a period of 3 months. However, salinity is significantly elevated near the breach area of the salt cavern, caused by strong flow velocities.

  17. Physical Volcanology of Obsidian Dome, California: A Complex Record of Emplacement of a Youthful Lava Dome

    NASA Astrophysics Data System (ADS)

    Kingsbury, Cole G.

    Obsidian Dome is a 550-650 year old, 1.5 by 1.8 km extrusion of high silica rhyolite situated along the Inyo Craters in eastern California. Field, and observations of drill core, reveals discrete metre-scale thick zones of rhyolitic glass exposed along the margin of Obsidian Dome as well as within its interior. Millimetre-scale flow-banded obsidian, pumice and rhyolite range from planar to chaotically folded, the latter a product of ductile, compressive deformation. Fractures, some of which display en-echelon splitting patterns are a result of brittle failure. Taken together, these features along with others, result from flow during lava dome growth and suggest complex emplacement patterns signified by vesiculation, crystallization and repeated brittle-ductile deformation, owing to episodic crossing of the glass transition. Evidence further shows that gas loss from the system occurred due to explosions, pumice formation and also brecciation of the melt as it episodically crossed the glass transition. Loss of gas by these mechanisms along with the inherent high viscosity of rhyolite melt explains the large amount of glass found on and within Obsidian Dome and other similar rhyolite extrusions in comparison to less silica-rich systems.

  18. Evolution of the microstructure and magnetic properties of as-cast and melt spun Fe2NiAl alloy during aging

    NASA Astrophysics Data System (ADS)

    Menushenkov, V. P.; Gorshenkov, M. V.; Shchetinin, I. V.; Savchenko, A. G.; Savchenko, E. S.; Zhukov, D. G.

    2015-09-01

    Fe2NiAl-based alloy with the nominal composition Fe51.1Ni23.5Al23.7Si1.7 was prepared by casting and melt-spinning. Comparison of the phase composition, microstructure and magnetic properties of water-quenched bulk samples and melt spun ribbons after isothermal aging in the 500-900 °C range were carried out. TEM investigations of the decomposition of the solid solution into β- and β2 phases during cooling or quenching and subsequent aging have revealed different types of decomposition products. The optimal periodic modulated structure with coercive force Hc~700 Oe was observed after cooling of as-cast alloy at a critical rate. In this structure the paramagnetic β2 phase forms a continuous network that isolates elongated single domain ferromagnetic β particles. The water-quenched bulk samples and melt spun ribbons were characterized by zone structure with zones about 10 nm and 4 nm in size. The isothermal aging of quenched samples resulted in the formation of modulated microstructure dissimilar to those of the optimal state. The coarsening of ferromagnetic β particles as well as deterioration of the magnetic insulation of β particles occur in bulk samples after aging at Tag>700 °C that decreases Hc≤350 Oe. The dependence δM(H) was measured and negative values of δM(H) in the H=0-2000 Oe range indicate that magnetostatic interactions between the β particles are dominant. The melt spun ribbons were characterized by the presence of antiphase domain boundaries (APD) and discontinuous precipitation (DP) products at grain boundaries (GB). The cellular areas at GBs consisting of alternating lamellas of β‧- and β2‧ type phases were formed after aging the ribbons at Tag>500 °C. At Tag>700 °C the modulated structure formed inside grains and the wide intergranular double-layer of β and β2 phases develops by the coalescence of the primary DP products that decrease Hc≤250 Oe. MFM image of the magnetic structure correlated with the microstructure of the

  19. Precipitation regime and stable isotopes at Dome C and Dome Fuji, East Antarctica

    NASA Astrophysics Data System (ADS)

    Schlosser, Elisabeth; Dittmann, Anna; Stenni, Barbara; Masson-Delmotte, Valerie; Powers, Jordan G.; Manning, Kevin W.; Raphael, Marilyn; Fujita, Koji; Werner, Martin; Valt, Mauro; Cagnati, Anselmo

    2016-04-01

    Dome Fuji and Dome C, both deep ice-core drilling sites in East Antarctica, are the only stations, for which direct daily precipitation measurements and stable isotope ratios of the precipitation samples are available. Whereas the Dome F series encompasses only one year of measurements, the Dome C series has been started in 2006 and is ongoing. For Dome C, the type of precipitation (diamond dust, hoar frost, snowfall) was determined based on crystal type analysis. The weather situations causing precipitation at the stations were analysed using data from the Antarctic Mesoscale Prediction System (AMPS). At both sites, major snowfall events were always related to an amplification of Rossby waves in the circumpolar westerlies, which led to an increased meridional transport of moisture and energy. Furthermore, increased amounts of diamond dust were observed after such event-type precipitation. The stable isotope data of the precipitation samples were related to the different weather situations and precipitation types and also simulated using a simple Rayleigh-type model (MCIM) and compared to output from the global isotopic-enhanced model ECHAM5wiso. Possible moisture sources were estimated using the synoptic analysis combined with back-trajectory calculation. MCIM was better in reproducing the annual cycle of deuterium excess, whereas ECHAM5wiso generally showed a smaller bias of the isotope ratios. Hoar frost shows isotope signals very different from diamond dust and snowfall, which hints at a more local cycle of sublimation and deposition for this type of precipitation, whereas both snowfall and diamond dust are related to large-scale moisture transport. Contrary to the literature, a more northern moisture source was found to be not necessarily associated with more depleted snowfall. This is explained by the strong warm air advection accompanying snowfall events, which decreases the temperature difference between source area and deposition site and thus leads to

  20. Estimate of pyroclastic flow velocities resulting from explosive decompression of lava domes

    NASA Astrophysics Data System (ADS)

    Fink, Jonathan H.; Kieffer, Susan W.

    1993-06-01

    APPARENTLY benign silicic domes or lava flows can travel for several kilometres and then suddenly collapse to generate pyroclastic phenomena capable of causing widespread destruction, as happened recently at Mount Unzen in Japan1. Two sources have been proposed for the energy that propels such 'Peléan' or 'Merapi'-type2 pyroclastic flows: gravitational col-lapse (supplemented by heating and expansion of air) and sudden expansion of pressurized gases from inside the lava flow. If gravity controls the energy transfer, then areas likely to be affected can be predicted on the basis of topography3, and the resulting deposits will bear a simple relationship to the part of the lava flow from which they issued. But if gas pressure adds a significant contribution, hazard assessment becomes more difficult because gas decompression adds velocities beyond those acquired by gravitational forces, putting much larger areas at risk and forming pyroclastic deposits that are much more difficult to relate to their source. Here we estimate the initial velocities of pyroclastic flows generated by dome disintegration for a range of lava compositions and volatile contents, and offer a conceptual framework for correlating the dynamics of dome-front collapse with the resulting sediment record. Our results indicate that explosive decompression at distal portions of domes can cause velocities comparable to gravitational collapse, especially in cases where volatiles become locally concentrated above equilibrium values.

  1. Distribution of axial lava domes along a superfast overlapping spreading center, 27-32°S on the East Pacific Rise

    NASA Astrophysics Data System (ADS)

    Bohnenstiehl, D. R.; Howell, J. K.; Hey, R. N.

    2008-12-01

    Deep-towed DSL-120 bathymetric data are used to investigate the pattern of lava dome formation along a superfast spreading portion of the southern East Pacific Rise (EPR), including the overlapping limbs of a giant (120 × 120 km) propagator near 29°S. Along the 670 km of the axis surveyed, 1172 small domes were identified using a closed contour algorithm. Their abundance, defined by spatial density, is well correlated with the along-axis relief of the ridge crest. Where the western and eastern limbs plunge toward the overlap zone, densities are high (3-6 km-2); however, where the axial depth profile is shallow and flat, densities are comparably low (0.4 km-2). Volcanic domes within the low abundance areas are characterized by lower ratios of height to basal radius (0.15 versus 0.22), smaller maximum heights (18 versus 40 m), and a larger relative percentage of small versus large mounds. The zone of high dome abundance encompasses the overlapping limbs of the rift and extends more than 100 km to the north and south beyond the overlap zone. Domes form dominantly during low effusion rate, point-source eruptions, which suggests that discontinuous melt lenses underlie the ridge axis proximal to the overlapper. Conversely, fissure-fed sheet flows dominate along the more distal segments, implying the presence of a more continuous axial magma lens. Throughout the survey area, dome abundance increases systematically near second-order segment boundaries. Within the high abundance zone, some third-order offsets also correlate with increased dome production, but local peaks in abundance are not tied exclusively to higher-order ridge offsets. Where dome abundance is low, domes are clustered tightly near second-order offsets and there is no increase in dome abundance near third-order segment boundaries.

  2. Exhumation Depths of the Lower Crustal Domes of the Pamir

    NASA Astrophysics Data System (ADS)

    McGraw, J. L.; Hacker, B. R.; Ratschbacher, L.

    2009-12-01

    Large-scale orogenic plateaux are important geodynamic features within continental collision systems. In this context, the indo-asian collision and the Tibetan plateau have been the focus of numerous studies aimed at understanding the development of these areas of over-thickened crust. However, the Pamir plateau may provide a better opportunity to understand the mechanics of plateau formation. Because of greater exhumation within the Pamir in the Cenozoic, deeper crustal rocks are exposed which may shed light on the crustal-scale processes occurring within the plateau interior. Examination of lower crustal exposures within the Pamir therefore provides an opportunity to understand the pressure-temperature history of the lower crust that is otherwise not directly observable in the Tibetan Plateau. Samples from three lower crustal domes from the Pamir plateau were analyzed by electron probe microanalysis. The sampled Kurgovat, Yazgulem, and Shakdhara domes likely formed diachronously as the Pamir grew northward, as they are dispersed north to south across the western half of the plateau. Exhumation depths determined from the pressure-temperature history of the rocks were obtained through quantitative thermobarometry. Well-established thermobarometers such as GASP, GHPQ, GBMP and GARB were used on the mainly metapelitic rocks. The typical peak pressure assemblage, garnet + kyanite + biotite + An20 plagioclase ± K-white mica, replaced staurolite, and is itself overgrown by sillimanite and more anorthitic plagioclase. Garnet cores are chemically homogeneous and rims are partially resorbed with long-wavelength rimward increases in Mn. Preliminary data indicate south to north variation in peak metamorphic pressures, which range from 9-11 kbar at temperatures of 700-800°C in the south to ~5 kbar at 500°C in the north; exhumation from peak pressures to 4-6 kbar occurred at temperatures of 500-700°C. These data imply exhumation depths of 32-40 km in the south and ~20 km

  3. Emplacement age of leucogranite in the Kampa Dome, southern Tibet

    NASA Astrophysics Data System (ADS)

    Liu, Xiao-Chi; Wu, Fu-Yuan; Yu, Liang-Jun; Liu, Zhi-Chao; Ji, Wei-Qiang; Wang, Jian-Gang

    2016-01-01

    Himalayan leucogranite is an important rock to decipher the orogenic evolution of the Himalayan orogen. It has been recognized that the leucogranite occurred as two separate, but parallel belts within Himalaya. Leucogranite in the north belt is mainly exposed an intrusion component within the gneissic dome. Although most domes have been intensively studied, the Kampa Dome, located in the east of Southern Tibet, is less investigated due to its inaccessibility. In this study, we conducted a comprehensive set of U(-Th)-Pb zircon, monazite and xenotime dating and trace element composition analyses using laser ablation technique, in order to constrain the emplacement age and lithological nature of the Kampa leucogranite. Zircons from gneiss are mainly magmatic and define a protolith age of ca. 498 Ma, but no Cenozoic age is documented. Zircons from leucogranite display inherited magmatic core overgrown by thin dark rim, which occasionally gives a much younger age of 27.7 ± 1.0 Ma. However, monazites from leucogranite yield a Th-Pb age of 25.7 ± 0.5 Ma to 26.8 ± 0.4 Ma, which is comparable to the U-Pb age of 24.8 ± 0.4 Ma obtained from xenotimes. For the granitic gneiss into which the leucogranite intruded, monazites and xenotimes give ages of 25.8 ± 0.6 Ma to 26.6 ± 0.8 Ma and 25.0 ± 0.4 Ma to 26.0 ± 1.0 Ma, respectively. These ages are comparable to those obtained from the leucogranite, and suggest that the metamorphic monazite and xenotime from gneiss formed during the leucogranite emplacement. Trace element analyses indicated that zircons from leucogranite have high P (up to 3721 ppm) and REE concentrations, but have low in Th/U ratios (0.04-0.16). Similarly, monazites from leucogranite generally show extreme HREE depletion and significant negative Eu anomaly with some displaying significantly tetrad effect. These geochemical features indicated that the Kampa leucogranite was highly fractionated during its evolution.

  4. DOME: operational metrics under one roof

    NASA Astrophysics Data System (ADS)

    Primas, F.; Marteau, S.; Tacconi-Garman, L. E.; Mainieri, V.; Rejkuba, M.; Mysore, S.

    2012-09-01

    Thirteen VLT/I instruments plus some extra critical components like the block-scheduling of the Laser Guide Star Facility and VLTI baselines make for a rather complex machine that constantly challenges our operational efficiencies. DOME (Dashboard for Operational Metrics at ESO) is an ongoing project developed, implemented and maintained by the ESO User Support Department. It aims at providing an ESO-internal dashboard where key operational metrics are published and updated at regular intervals. Here, we will present the project and report on the indicators that have been looked at until now.ty and VLTI baselines make for a rather complex machine that constantly challenges our operational efficiencies. DOME (Dashboard for Operational Metrics at ESO) is an ongoing project developed, implemented and maintained by the ESO User Support Department. It aims at providing an ESO-internal dashboard where key operational metrics are published and updated at regular intervals. Here, we will present the project and report on the indicators that have been looked at until now.

  5. Hydrostatic extrusion of Cu-Ag melt spun ribbon

    SciTech Connect

    Hill, Mary Ann; Bingert, John F.; Bingert, Sherri A.; Thoma, Dan J.

    1998-01-01

    The present invention provides a method of producing high-strength and high-conductance copper and silver materials comprising the steps of combining a predetermined ratio of the copper with the silver to produce a composite material, and melt spinning the composite material to produce a ribbon of copper and silver. The ribbon of copper and silver is heated in a hydrogen atmosphere, and thereafter die pressed into a slug. The slug then is placed into a high-purity copper vessel and the vessel is sealed with an electron beam. The vessel and slug then are extruded into wire form using a cold hydrostatic extrusion process.

  6. Hydrostatic extrusion of Cu-Ag melt spun ribbon

    SciTech Connect

    Hill, M.A.; Bingert, J.F.; Bingert, S.A.; Thoma, D.J.

    1998-09-08

    The present invention provides a method of producing high-strength and high-conductance copper and silver materials comprising the steps of combining a predetermined ratio of the copper with the silver to produce a composite material, and melt spinning the composite material to produce a ribbon of copper and silver. The ribbon of copper and silver is heated in a hydrogen atmosphere, and thereafter die pressed into a slug. The slug then is placed into a high-purity copper vessel and the vessel is sealed with an electron beam. The vessel and slug then are extruded into wire form using a cold hydrostatic extrusion process. 5 figs.

  7. Acoustic and Elastodynamic Redatuming for VSP Salt Dome Flank Imaging

    NASA Astrophysics Data System (ADS)

    Lu, R.; Willis, M.; Toksoz, N.

    2007-12-01

    We apply an extension of the concept of Time Reversed Acoustics (TRA) for imaging salt dome flanks using Vertical Seismic Profile (VSP) data. We demonstrate its performance and capabilities on both synthetic acoustic and elastic seismic data from a Gulf of Mexico (GOM) model. This target-oriented strategy eliminates the need for the traditional complex process of velocity estimation, model building, and iterative depth migration to remove the effects of the salt canopy and surrounding overburden. In this study, we use data from surface shots recorded in a well from a walkaway VSP survey. The method, called redatuming, creates a geometry as if the source and receiver pairs had been located in the borehole at the positions of the receivers. This process generates effective downhole shot gathers without any knowledge of the overburden velocity structure. The resulting shot gathers are less complex since the VSP ray paths from the surface source are shortened and moved to be as if they started in the borehole, then reflected off the salt flank region and captured in the borehole. After redatuming, we apply multiple passes of prestack migration from the reference datum of the borehole. In our example, the first pass migration, using only simple vertical velocity gradient model, reveals the outline of the salt edge. A second pass of reverse-time prestack depth migration using the full, two-way wave equation, is performed with an updated velocity model that now consists of the velocity gradient and the salt dome. The second pass migration brings out the dipping sediments abutting the salt flank because these reflectors were illuminated by energy that bounced off the salt flank forming prismatic reflections.

  8. SOLUTION MINING IN SALT DOMES OF THE GULF COAST EMBAYMENT

    SciTech Connect

    Griswold, G. B.

    1981-02-01

    Following a description of salt resources in the salt domes of the gulf coast embayment, mining, particularly solution mining, is described. A scenario is constructed which could lead to release of radioactive waste stored in a salt dome via inadvertent solution mining and the consequences of this scenario are analyzed.

  9. Astronaut Alan Bean doing acrobatics in OWS dome area

    NASA Technical Reports Server (NTRS)

    1973-01-01

    Astronaut Alan L. Bean, Skylab 3 commander, doing acrobatics in the dome area of the Orbital Workshop (OWS) on the space station cluster in Earth orbit. The dome area is about 22 feet in diameter and 19 feet from top to bottom.

  10. Astronaut Jack Lousma doing acrobatics in OWS dome area

    NASA Technical Reports Server (NTRS)

    1973-01-01

    Astronaut Jack R. Lousma, Skylab 3 pilot, doing acrobatics in the dome area of the Orbital Workshop (OWS) on the space station cluster in Earth orbit. The dome area is about 22 feet in diameter and 19 feet from top to bottom.

  11. Baseline design and requirements for the LSST rotating enclosure (dome)

    NASA Astrophysics Data System (ADS)

    Neill, D. R.; DeVries, J.; Hileman, E.; Sebag, J.; Gressler, W.; Wiecha, O.; Andrew, J.; Schoening, W.

    2014-07-01

    The Large Synoptic Survey Telescope (LSST) is a large (8.4 meter) wide-field (3.5 degree) survey telescope, which will be located on the Cerro Pachón summit in Chile. As a result of the wide field of view, its optical system is unusually susceptible to stray light; consequently besides protecting the telescope from the environment the rotating enclosure (Dome) also provides indispensible light baffling. All dome vents are covered with light baffles which simultaneously provide both essential dome flushing and stray light attenuation. The wind screen also (and primarily) functions as a light screen providing only a minimum clear aperture. Since the dome must operate continuously, and the drives produce significant heat, they are located on the fixed lower enclosure to facilitate glycol water cooling. To accommodate day time thermal control, a duct system channels cooling air provided by the facility when the dome is in its parked position.

  12. The Velay dome (French Massif Central): melt generation and granite emplacement during orogenic evolution

    NASA Astrophysics Data System (ADS)

    Ledru, P.; Courrioux, G.; Dallain, C.; Lardeaux, J. M.; Montel, J. M.; Vanderhaeghe, O.; Vitel, G.

    2001-12-01

    This paper is a synthesis of available data on the Velay dome that include both small- and large-scale lithologic and structural mapping, strain analysis, isotope geochemistry, geochronology and pressure-temperature estimates. The Velay dome, one of the largest granite-migmatite domes of the Variscan Belt, formed during orogenic collapse at around 300 Ma. Its study allows an assessment of the thermal and geodynamic context leading to voluminous crustal anatexis of the Variscan orogenic crust. A first melting stage developed in connection with south-verging thrust zones during the Early Carboniferous, leading to a crustal thickening estimated at 20 km minimum. The involvement of fertile lithologies and the intrusion of plutons of deep origin contributed to the development of water-saturated melts. The volume of biotite granite extracted from melt during this period was limited. The second phase of melting, corresponded to generalized melting of gneiss achieved by biotite-dehydration melting reactions and accompanied by the generation of cordierite-bearing granites. At this stage, crustal-scale detachment faults were active and partially obliterated the earlier structures. The new structures were progressively tilted to the vertical at the margin of the Velay dome due to the southward and lateral ballooning of the granitic dome. The reconstructed P, T path indicate that the large volume of melt produced was a consequence of a significant increase in temperature at the onset of biotite dehydration melting. At the base of the crust, this melting event is coeval with granulite facies metamorphism associated to underplating of mantle-derived magmas as suggested by the geochemical signature of Late Paleozoic lower crustal xenoliths sampled by Cenozoic volcanoes and with the isotopic signature of the late granitic intrusions. Accordingly, it is proposed that asthenospheric upwelling was responsible for the temperature increase favoring melting of hydrous minerals.

  13. Phase competition in trisected superconducting dome

    NASA Astrophysics Data System (ADS)

    Vishik, Inna

    2012-02-01

    The momentum-resolved nature of angle-resolved photoemission spectroscopy (ARPES) has made it a key probe of emergent phases in the cuprates, such as superconductivity and the pseudogap, which have anisotropic momentum-space structure. ARPES can be used to infer the origin of spectral gaps from their distinct phenomenology---temperature, doping, and momentum dependence, and this principle has been used to argue that the pseudogap is a distinct phase from superconductivity, rather than a precursor [1]. We have studied Bi2Sr2CaCu2O8+δ (Bi-2212) using laser-ARPES, and our data give evidence for three distinct quantum phases comprising the superconducting ground state, accompanied by abrupt changes at p˜0.076 and p˜0.19 in the doping-and-temperature dependence of the gaps near the bond-diagonal (nodal) direction [2]. The latter doping likely marks the quantum critical point of the pseudogap, while the former represents a distinct competing phase at the edge of the superconducting dome. Additionally, we find that the pseudogap advances closer towards the node when superconductivity is weak, just below Tc or at low doping, and retreats towards the antinode well below Tc and at higher doping. This phase competition picture together with the two critical doping are synthesized into our proposed phase diagram, which also reconciles conflicting phase diagrams commonly used in the field. Our results underscore the importance of quantum critical phenomena to cuprate superconductivity, provide a microscopic picture of phase competition in momentum space, and predict the existence of phase boundaries inside the superconducting dome which are different from simple extrapolations from outside the dome. [4pt] [1] I. M. Vishik, W. S. Lee, R.-H. He, M. Hashimoto, Z. Hussain, T. P. Devereaux, and Z.-X. Shen. New J. Phys. 12, 105008 (2010). [0pt] [2] I. M. Vishik, M. Hashimoto, R.-H. He, W. S. Lee, F. Schmitt, D. H. Lu, R.G. Moore, C. Zhang, W. Meevasana, T. Sasagawa, S. Uchida, K

  14. Miocene lava flows and domes, cooling fractures, carapace breccia, and avalanche deposits near Goldstone, California

    NASA Astrophysics Data System (ADS)

    Buesch, D.

    2013-12-01

    Mapping and petrography of volcanic rocks in western Fort Irwin (FI), California, provide insights into the cooling history of lava flows and domes and the formation of associated carapace breccia and avalanche deposits. The rocks formed on the eastern margin of the 19-16 Ma Eagle Crags volcanic field (Sabin and others, 1994). Lava compositions range from porphyritic olivine basalt to aphyric rhyolite. Basalt flows are 1-5 m thick and <1-2 km long, and sequences 5-50 m thick are traceable for >7 km. Andesite to rhyolite flows are 30-80 m thick and <1-3 km long, and domes have 100-300 m relief and radial length of 0.6-1.2 km. Cooling fractures, identified by occurrence of margins and geometry, are in all lava flows and domes. Similar to a 'rim' (Buesch and others, 1996 & 1999; Buesch, 2006), a 'margin' is a region along a fracture wall with a finer texture or different type of crystallinity or vesicularity compared to rock inward from the fracture. At FI, margins occur on many fractures and typically are 0.5-3 mm wide. They indicate that a fracture formed during initial cooling, before the bulk of the rock crystallized. Planarity and surface roughness are used to analyze fractures (Buesch and others, 1996). Typically at FI, cooling fractures are planar and smooth, and post-cooling fractures are slightly irregular and slightly rough. Typically, plan views of cooling fractures are 5-6 sided in olivine basalt, and 4-sided in andesite to rhyolite. Fracture sets are mostly perpendicular to the original surface of a flow, and some bend toward the interior. Many lava flows and domes have lateral and capping breccias referred to as carapace breccia. Similar breccia also cloaks individual lobes of composite domes. Carapace breccia can grade down into a non-brecciated interior, but in some cases, compositionally similar late-stage flow-banded lava was injected beneath the breccia, Breccia fragments are vitric or crystallized, and many have margins that do not match those of

  15. Geologic study of Kettle dome, northeast Washington. Final report

    SciTech Connect

    Not Available

    1980-10-01

    This geologic study of Kettle dome, northeast Washington, encompasses an area of approximately 800 square miles (2048 sq km). The evaluation of uranium occurrences associated with the igneous and metamorphic rocks of the dome and the determination of the relationship between uranium mineralization and stratigraphic, structural, and metamorphic features of the dome are the principal objectives. Evaluation of the validity of a gneiss dome model is a specific objective. The principal sources of data are detailed geologic mapping, surface radiometric surveys, and chemical analyses of rock samples. Uranium mineralization is directly related to the presence of pegmatite dikes and sills in biotite gneiss and amphibolite. Other characteristics of the uranium occurrences include the associated migmatization and high-grade metamorphism of wallrock adjacent to the pegmatite and the abrupt decrease in uranium mineralization at the pegmatite-gneiss contact. Subtle chemical characteristics found in mineralized pegmatites include: (1) U increase as K/sub 2/O increases, (2) U decreases as Na/sub 2/O increases, and (3) U increases as CaO increases at CaO values above 3.8%. The concentration of uranium occurrences in biotite gneiss and amphibolite units results from the preferential intrusion of pegmitites into these well-foliated rocks. Structural zones of weakness along dome margins permit intrusive and migmatitic activity to affect higher structural levels of the dome complex. As a result, uranium mineralization is localized along dome margins. The uranium occurrences in the Kettle dome area are classified as pegmatitic. Sufficient geologic similarities exist between Kettle dome and the Rossing uranium deposit to propose the existence of economic uranium targets within Kettle dome.

  16. The Discovery Dome: A Tool for Increasing Student Engagement

    NASA Astrophysics Data System (ADS)

    Brevik, Corinne

    2015-04-01

    The Discovery Dome is a portable full-dome theater that plays professionally-created science films. Developed by the Houston Museum of Natural Science and Rice University, this inflatable planetarium offers a state-of-the-art visual learning experience that can address many different fields of science for any grade level. It surrounds students with roaring dinosaurs, fascinating planets, and explosive storms - all immersive, engaging, and realistic. Dickinson State University has chosen to utilize its Discovery Dome to address Earth Science education at two levels. University courses across the science disciplines can use the Discovery Dome as part of their curriculum. The digital shows immerse the students in various topics ranging from astronomy to geology to weather and climate. The dome has proven to be a valuable tool for introducing new material to students as well as for reinforcing concepts previously covered in lectures or laboratory settings. The Discovery Dome also serves as an amazing science public-outreach tool. University students are trained to run the dome, and they travel with it to schools and libraries around the region. During the 2013-14 school year, our Discovery Dome visited over 30 locations. Many of the schools visited are in rural settings which offer students few opportunities to experience state-of-the-art science technology. The school kids are extremely excited when the Discovery Dome visits their community, and they will talk about the experience for many weeks. Traveling with the dome is also very valuable for the university students who get involved in the program. They become very familiar with the science content, and they gain experience working with teachers as well as the general public. They get to share their love of science, and they get to help inspire a new generation of scientists.

  17. Transdomes: Emplacement of Migmatite Domes in Oblique Tectonic Settings

    NASA Astrophysics Data System (ADS)

    Teyssier, C. P.; Rey, P. F.; Whitney, D. L.; Mondy, L. S.; Roger, F.

    2014-12-01

    Many migmatite domes are emplaced within wrench corridors in which a combination of strike-slip and extensional detachment zones (pull-apart, extensional relay, or transfer zones) focus deep-crust exhumation. The Montagne Noire dome (France, Variscan Massif Central) exemplifies wrench-related dome formation and displays the following structural, metamorphic, and geochronologic characteristics of a 'transdome': the dome is elongate in the direction of extension; foliation outlines a double dome separated by a high-strain zone; lineation is shallowly plunging with a fairly uniform trend that parallels the strike of the high-strain zone; subdomes contain recumbent structures overprinted by upright folds that affected upward by flat shear zones associated with detachment tectonics; domes display a large syn-deformation metamorphic gradient from core (upper amphibolite facies migmatite) to margin (down to greenschist facies mylonite); some rocks in the dome core experienced isothermal decompression revealed by disequilibrium reaction textures, particularly in mafic rocks (including eclogite); and results of U-Pb geochrononology indicate a narrow range of metamorphic crystallization from core to mantling schist spanning ~10 Myr. 3D numerical modeling of transdomes show that the dome solicits a larger source region of partially molten lower crust compared to 2D models; this flowing crust creates a double-dome architecture as in 2D models but there are differences in the predicted thermal history and flow paths. In a transtension setting, flow lines converge at depth (radial-centripetal flow) toward the zone of extension and diverge at shallow levels in a more uniform direction that is imposed by upper crust motion and deformation. This evolution produces a characteristic pattern of strain history, progressive fabric overprint, and P-T paths that are comparable to observed dome rocks.

  18. Spatial and temporal patterns of dome extrusion during the 2004-2008 eruption of Mount St. Helens

    NASA Astrophysics Data System (ADS)

    Salzer, J. T.; Denlinger, R. P.; Diefenbach, A. K.; Walter, T. R.

    2014-12-01

    Extensive efforts by the USGS Cascades Volcano Observatory in response to the 2004-2008 dome building eruption at Mount St. Helens recorded the extrusion of seven dacite spines. Efforts included a network of time-lapse cameras. Published studies of decimated data from these cameras show strong correlations between (long-term) extrusion velocities determined from the camera imagery and ancillary geophysical data, such as dome tilt and RSAM seismicity. However, more detailed analysis of these data should provide better constraints on physical processes behind dome extrusion. Here we apply modern computer vision techniques to explore the spatiotemporal variability and interactions occurring during spine extrusion and dome growth. Digital Image Correlation (DIC) delineates the deformation field in a series of images at sub-pixel level, and quantifies dome, talus and glacier deformation at unprecedented resolution, revealing spatiotemporal variability of the strain field on the time scale of hours. We identify sharp boundaries between the vertically extruding spine, laterally displaced material, and downward-creeping talus. The spine growth at Mount St. Helens appears locally constrained and structurally separated into distinct segments. The velocities of different dome segments are generally correlated, but displacement patterns of the talus are more complex. We identify short term fluctuations with periods of hours to days superimposed on longer term fluctuations having periods of several weeks. The short term episodes of high displacement rates are often associated with strongly degassing plumes observed in the camera imagery. Over longer periods (days to weeks), extrusion rates form a sinusoidal fluctuating pattern, marked by sharp increases and gradual decreases in velocity. These observations substantiate the correlations with seismic and geodetic data shown in previous studies, but more closely constrain the velocity fluctuations of each spine. These fluctuations

  19. Primary arm spacing in chill block melt spun Ni-Mo alloys

    NASA Technical Reports Server (NTRS)

    Tewari, S. N.; Glasgow, T. K.

    1986-01-01

    Chill block melt spun ribbons of Ni-Mo binary alloys containing 8.0 to 41.8 wt % Mo have been prepared under carefully controlled processing conditions. The growth velocity has been determined as a function of distance from the quench surface from the observed ribbon thickness dependence on the melt puddle residence time. Primary arm spacings measured at the midribbon thickness locations show a dependence on growth velocity and alloy composition which is expected from dendritic growth models for binary alloys directionally solidified in a positive temperature gradient.

  20. Tensile strength of dome rocks and lavas at Santiaguito dome complex, Guatemala

    NASA Astrophysics Data System (ADS)

    Hornby, Adrian; Lamb, Oliver; Lamur, Anthony; Lavallée, Yan

    2015-04-01

    Lava domes are inherently unstable structures, subject to intense gas flux and rapid variations in the state of stress. At shallow depths confining stresses are minimal and deformation is dilatant, occurring predominantly through tensile fractures. This fracture mode facilitates outgassing and contributes to the development of gas-and-ash activity as well as vulcanian eruptions. However, there is a paucity of tensile strength data for volcanic materials in the published literature, and we know of no paper which addresses this at high temperatures. We study the tensile strength of dome rocks collected at the Santiaguito dome complex, Guatemala, over a porosity range of 3-25%. Indirect tensile (Brazilian) tests were conducted on 40-mm diameter cores, by imposing a compressive displacement rate (radial to the core) of 4 micron/s at room temperature as well as an eruptive temperature of ca. 850 °C. An acoustic monitoring system is employed to track the nucleation, propagation and coalescence of fractures leading to complete sample failure. We find that the rocks' tensile strength exhibits a nonlinear decrease with porosity. Preliminary tests at high temperature indicate that some rocks exhibit a higher tensile strength (than at room temperature); in these experiments, samples containing a higher fraction of interstitial melt revealed an additional component of viscous flow. Further experiments conducted at higher strain rates will define the brittle response of the liquid during tensile failure. The data is compared against similar datasets for volcanic rocks. We will discuss implications for shallow volcanic processes ranging from dilation bands and tuffisite formation to gas-and-ash explosions and dome structural stability.

  1. Blowing off steam: Tuffisite formation as a regulator for lava dome eruptions

    NASA Astrophysics Data System (ADS)

    Kendrick, Jackie; Lavallée, Yan; Varley, Nick; Wadsworth, Fabian; Lamb, Oliver; Vasseur, Jérémie

    2016-04-01

    Tuffisites are veins of variably sintered, pyroclastic particles that form in conduits and lava domes as a result of localized fragmentation events during gas-and-ash explosions. Those observed in-situ on the active 2012 lava dome of Volcán de Colima range from voids with intra-clasts showing little movement and interpreted to be failure-nuclei, to sub-parallel lenses of sintered granular aggregate interpreted as fragmentation horizons, through to infilled fractures with evidence of viscous remobilization. All tuffisites show evidence of sintering. Further examination of the complex fracture-and-channel patterns reveals viscous backfill by surrounding magma, suggesting that lava fragmentation was followed by stress relaxation and continued viscous deformation as the tuffisites formed. The natural tuffisites are more permeable than the host andesite, and have a wide range of porosity and permeability compared to a narrower window for the host rock, and gauging from their significant distribution across the dome, we posit that the tuffisite veins may act as important outgassing pathways. To investigate tuffisite formation we crushed and sieved andesite from the lava dome and sintered it at magmatic temperatures for different times. We then assessed the healing and sealing ability by measuring porosity and permeability, showing that sintering reduces both over time. During sintering the porosity-permeability reduction occurs due to the formation of viscous necks between adjacent grains, a process described by the neck-formation model of Frenkel (1945). This process leads the granular starting material to a porosity-permeability regime anticipated for effusive lavas, and which describes the natural host lava as well as the most impervious of natural tuffisites. This suggests that tuffisite formation at Volcán de Colima constructed a permeable network that enabled gas to bleed passively from the magma. We postulate that this progressively reduced the lava dome

  2. The eastern Central Pamir Gneiss Domes: temporal and spatial geometry of burial and exhumation

    NASA Astrophysics Data System (ADS)

    Rutte, Daniel; Stearns, Michael; Ratschbacher, Lothar

    2013-04-01

    of the domes are Paleozoic. Detrital zircon data from the low-grade cover and surrounding units of the Muskol dome suggest that low-grade cover and high-grade dome formed from the same Paleozoic, possibly early Mesozoic strata. This indicates that the upper crust of the Central Pamir thickened to at least 30 km in phase (1). Based on our data and those of Robinson et al. (2012) underthrusted Karakul-Mazar (Songpan-Ganze) material (as discussed by Schwab et al. 2004), in analogy to the Tibetan Qiangtang domes (Kapp et al. 2000), can be ruled out as protolith for the Muskol and Shatput domes. (3) Neogene shortening is bi-vergent: top-to-S back-thrusting north of the Central Pamir Gneiss Domes opposes top-to-N thrusting in the south. Neogene deformation affected ~18 Ma (Ar-Ar) coarse fluvial and alluvial fan strata with basaltic dikes and flows south of the dome; restoration of these strata yielded up to 40% shortening. Total shortening by thrusting of the Central Pamir is at least 40% in the Shatput-Muskol area with a minimal total shortening of 70 km; internal deformation with recumbent north-verging folds within the domes and its cover indicate much higher values. Literature: Kapp, P., Yin, A., Manning, C. E., Murphy, M., Harrison, T. M., Spurlin, M., Lin, D., Yi-Guang, D., Cun-Ming, W. (2000) Blueshist-bearing metamorphic core complexes in the Qiangtang block reveal deep crustal structure of northern Tibet, Geology, v. 28; no. 1; p.19-22 Robinson, A. C., M. Ducea, and T. J. Lapen (2012), Detrital zircon and isotopic constraints on the crustal architecture and tectonic evolution of the northeastern Pamir, Tectonics, 31, TC2016, doi:10.1029/2011TC003013. Schwab, M., Ratschbacher, L., Siebel, W., McWilliams, M., Minaev, V., Lutkov., V., Chen, F., Stanek, K., Nelson, B. and Wooden, J. L. (2004) Assembly of the Pamir: Age and origin of magmatic belts from the southern Tien Shan to the southern Pamir and their relation to Tibet, Tectonics, 23, No. 4, TC4002

  3. Structural review of the Vredefort dome

    NASA Technical Reports Server (NTRS)

    Colliston, W. P.; Reimold, W. U.

    1992-01-01

    The structure of the older-than-3.2-Ga Archean basement and Archean-to-Precambrian sedimentary/volcanic rocks (3.07 to ca. 2.2 Ga) in the center of the Witwatersrand Basin to the southwest of Johannesburg (South Africa) is dominated by the ca. 2.0-Ga megascopic Vredefort 'Dome' structure. The effect of the 'Vredefort event' is demonstrably large and is evident within a northerly arc of about 100 km radius around the granitic core of the structure. Northerly asymmetric overturning of the strata is observed within the first 17 km (strata is horizontal in the south), followed by a 40-km-wide rim synclinorium. Fold and fault structures (normal, reverse, and strike-slip) are locally as well as regionally concentrically arranged with respect to the northern and western sides of the structure. The unusual category of brittle deformation, the so-called 'shock deformation', observed in the collar strata has attracted worldwide attention over the past two decades. These deformation phenomena include the presence of coesite and stishovite, mylonites, and pseudotachylites, cataclasis at a microscopic scale, and the ubiquitous development of multiply striated joint surfaces (which include shatter cones, orthogonal, curviplanar, and conjugate fractures). The macroscopic to microscopic deformation features have led to the formulation of various hypotheses to account for the origin of the Vredefort structure: (1) tectonic hypotheses--deep crustal shear model, doming and N-directed thrust fault model, fold interference model, and diapir model; (2) the exogenous bolide impact hypothesis; and (3) the endogenous cryptoexplosion model.

  4. Geohydrology of the Keechi, Mount Sylvan, Oakwood, and Palestine salt domes in the northeast Texas salt-dome basin

    USGS Publications Warehouse

    Carr, Jerry E.; Halasz, Stephen J.; Peters, Henry B.

    1980-01-01

    Additional problems concerning the hydrologic stability of Oakwood and Palestine Salt Domes have resulted from the disposal of oil-field salinewater in the cap rock at the Oakwood Dome and previous solution mining of salt at the Palestine Dome Additional investigations are needed to determine if a selected dome is hydrologically stable. Needed investigations include: (1) A more complete comparative analysis of the regional and local geohydrologic system; (2) a site-specific drilling and sampling program to analyze the cap rock-aquifer boundary, sediment distribution, hydraulic-parameter variations, hydraulic-head relationships, and hydrochemical patterns; and (3) mass-transport computer modeling of ground-water flow at the domes.

  5. The Vaasa migmatitic complex: the birth, growth and death of a thermal dome

    NASA Astrophysics Data System (ADS)

    Chopin, Francis; Korja, Annakaisa; Hölttä, Pentti; Eklund, Olav; Tapani Rämö, Osmo

    2015-04-01

    The Vaasa migmatitic complex, or Vaasa dome, is cored by diatexite migmatites and S-type granitoids and gradually mantled by metatexite migmatites and mica schist with thin metabasite-andesite intercalations. Previous geochemical studies have demonstrated that the metasediments are the sources of the melted core: it have been suggested that the complex have been formed by in-situ melting of a basin. Field work studies highlight the formation of a gently dipping metamorphic fabric with a lateral increase of the in-situ melt content towards the core of the dome (D1). This early layered and partially melted fabric is then affected by a regional N-S shortening forming km- to outcrop-scale E-W striking folds and new sub-vertical foliation (D2). Late sub-vertical shearing is visible along the dome border and within the diatexitic zone (D3). No late detachment structures have been observed. In the metamorphic belt, the grade increases from medium-T amphibolite facies to low-P granulite facies towards the core of the dome. Pseudosections in the MnNCKFMASHTO system have been performed in one mica schist (Grt+BtPl+Qz±Std+Sill+And) and one metatexite migmatite (Bt+Liq+Crd+Pl+Kfs+Grt+Qz±Sill+And). The metamorphic peaks are bracketed at 560°C at 5 kbar and 750-770°C at 4.5-5 kbar, respectively. The retrograde condition is situated at 540°C and <3 kbar for both lithologies. This implies an isobaric increase of the metamorphic grade towards the core of the dome. An isothermal decompression for the schist and a retrograde PT path for the migmatites are observed. Existing and new U/Pb monazite ages from mica schists, migmatites and clustered at 1860-1865 Ma whereas U/Pb ages from metamorphic and magmatic zircons are older and clustered at 1875 Ma. The latter might represent the peak of melting process and associated metamorphism whereas monazites ages might be related to the cooling of the orogenic middle crust. It has to be noticed that few monazites from metamorphic rocks of

  6. Applications of a simplified equation of state for the density of silicate hydrous magmas: The Volcán de Colima (Mexico) buoyancy-driven dome growth process. Similarities and differences with the Popocatépetl volcano domes

    NASA Astrophysics Data System (ADS)

    González-Mellado, Alex Onar; De la Cruz-Reyna, Servando; Navarro-Ochoa, Carlos

    2011-08-01

    Colima and Popocatépetl volcanoes began erupting during the second half of the twentieth century after periods or relatively long quiescence. Both eruptive episodes show similarities: persistent dome growth and destruction episodes over periods of decades, and differences: higher rates of magma and gas production at Popocatépetl, with similar magmas (Popocatépetl's slightly more acidic). We use a simplified equation of state (EOS) for calculating the density of the hydrous andesitic magmas of Volcán de Colima in a realistic range of pressures, temperatures and dissolved water content to model the density contrast with the host rock causing buoyancy of the magmatic column. We use this model to explain some aspects of the dome-forming effusive activity of Colima, and compare the results with a similar study made in a previous work on Popocatépetl. This dome-height isostatic model explains well the observed mean heights (around 50 m) of the Colima lava domes with the buoyant force resulting from a 2.5 wt.% H 2O content in the melt, a value consistent with recently published measurements of rock inclusions. The slightly higher H 2O contents required for the observed dome heights at Popocatépetl is explained in terms of the different depths of the isostatic compensation levels, the compositional differences between the magmas, and the structural differences between the volcanic edifices.

  7. The uppermost mantle beneath the Kenya dome and relation to melting, rifting and uplift in East Africa

    NASA Astrophysics Data System (ADS)

    Davis, Paul M.; Slack, Philip D.

    2002-04-01

    We compare new results on S-wave delays and P wave tomography to characterize the rising limb and melt zone of an inferred mantle convection cell beneath the Kenya dome. These results are extended to the Nyiragongo and Ethiopia domes using long wavelength gravity and topography. We suggest that the east African rift results from separation of deeper mantle upwelling into three currents that impinge on and erode the base of the lithosphere. Their thermal buoyancy drives the domal uplift, whereas brittle failure of the upper lithosphere forms the rift grabens.

  8. Lava Dome Growth at Volcan de Fuego MEXICO (Colima Volcano), October 2001 to May 2002

    NASA Astrophysics Data System (ADS)

    Suarez-Plascencia, C.; Nunez-Cornu, F. J.; Reyes-Davila, G. A.

    2002-12-01

    The Volcan de Fuego (19.512 N, 103.617 W) is located on the border between the States of Jalisco and Colima, Mexico, it is also known as Colima Volcano or Zapotl n Volcano, is a stratovolcano rising nearly 4000 m above sea level, and is the most active volcano in Mexico. Recent activity has been characterized by at least 3 different phases since January 1998 when seismic swarms began and ended with the extrusion of blocky lava in November 22, 1998 by the West vent as the 1991 eruptive process. That extrusive period lasted until the end of January, 1999 when was possible to observe a change in the seismic pattern, which mark the beginning of a new eruptive regime, an explosive one. On February 10, 1999 at approximately 0154 local time, 0754 gmt, an explosive event happens at the summit dome of Volc n de Fuego, four more big explosions took place at the summit the last one at dawn February 22, 2001. These explosions opened a new crater at the summit with a elliptical form with radius of 260 x 225 m and depth between 40 m and 15 m. A small dome structure inside the new crater was reported by March 2001. A reconnaissance flight in August 2001 shows two main features in the main crater an steep-sided mound(scoria cone) over the West vent and an inner crater on the NE vent. On October 31 Civil Defense members at Nevado Base on Nevado de Colima observed a neddle over the main crater rim, reconnaissance flight shows a spiny, 40 m high with a diameter of 20 m grows from the NE vent, the spiny seems to formed by material of the 1976 eruption. Continuous aerial observations allow us to follow the growth of a new dome pushing out the spiny. On November 23 the dimensions of the dome under the spiny were a radius of about 14 m and 21 m high for a total extrusion of 86,000 m3 which implies a extrusion rate of 0.027m3 /seg. By December the dome push out the spiny and began to grow from the NW vent. By December 29 an increase in the rate of extrusion was observed reaching a value

  9. Linking naturally and unnaturally spun silks through the forced reeling of Bombyx mori.

    PubMed

    Mortimer, Beth; Guan, Juan; Holland, Chris; Porter, David; Vollrath, Fritz

    2015-01-01

    The forced reeling of silkworms offers the potential to produce a spectrum of silk filaments, spun from natural silk dope and subjected to carefully controlled applied processing conditions. Here we demonstrate that the envelope of stress-strain properties for forced reeled silks can encompass both naturally spun cocoon silk and unnaturally processed artificial silk filaments. We use dynamic mechanical thermal analysis (DMTA) to quantify the structural properties of these silks. Using this well-established mechanical spectroscopic technique, we show high variation in the mechanical properties and the associated degree of disordered hydrogen-bonded structures in forced reeled silks. Furthermore, we show that this disorder can be manipulated by a range of processing conditions and even ameliorated under certain parameters, such as annealing under heat and mechanical load. We conclude that the powerful combination of forced reeling silk and DMTA has tied together native/natural and synthetic/unnatural extrusion spinning. The presented techniques therefore have the ability to define the potential of Bombyx-derived proteins for use in fibre-based applications and serve as a roadmap to improve fibre quality via post-processing. PMID:25242653

  10. Strength and Water Interactions of Cellulose I Filaments Wet-Spun from Cellulose Nanofibril Hydrogels

    NASA Astrophysics Data System (ADS)

    Lundahl, Meri J.; Cunha, A. Gisela; Rojo, Ester; Papageorgiou, Anastassios C.; Rautkari, Lauri; Arboleda, Julio C.; Rojas, Orlando J.

    2016-07-01

    Hydrogels comprising cellulose nanofibrils (CNF) were used in the synthesis of continuous filaments via wet-spinning. Hydrogel viscosity and spinnability, as well as orientation and strength of the spun filaments, were found to be strongly affected by the osmotic pressure as determined by CNF surface charge and solid fraction in the spinning dope. The tensile strength, Young’s modulus and degree of orientation (wide-angle X-ray scattering, WAXS) of filaments produced without drawing were 297 MPa, 21 GPa and 83%, respectively, which are remarkable values. A thorough investigation of the interactions with water using dynamic vapour sorption (DVS) experiments revealed the role of sorption sites in the stability of the filaments in wet conditions. DVS analysis during cycles of relative humidity (RH) between 0 and 95% revealed major differences in water uptake by the filaments spun from hydrogels of different charge density (CNF and TEMPO-oxidised CNF). It is concluded that the mechanical performance of filaments in the presence of water deteriorates drastically by the same factors that facilitate fibril alignment and, consequently, enhance dry strength. For the most oriented filaments, the maximum water vapour sorption at 95% RH was 39% based on dry weight.

  11. Strength and Water Interactions of Cellulose I Filaments Wet-Spun from Cellulose Nanofibril Hydrogels.

    PubMed

    Lundahl, Meri J; Cunha, A Gisela; Rojo, Ester; Papageorgiou, Anastassios C; Rautkari, Lauri; Arboleda, Julio C; Rojas, Orlando J

    2016-01-01

    Hydrogels comprising cellulose nanofibrils (CNF) were used in the synthesis of continuous filaments via wet-spinning. Hydrogel viscosity and spinnability, as well as orientation and strength of the spun filaments, were found to be strongly affected by the osmotic pressure as determined by CNF surface charge and solid fraction in the spinning dope. The tensile strength, Young's modulus and degree of orientation (wide-angle X-ray scattering, WAXS) of filaments produced without drawing were 297 MPa, 21 GPa and 83%, respectively, which are remarkable values. A thorough investigation of the interactions with water using dynamic vapour sorption (DVS) experiments revealed the role of sorption sites in the stability of the filaments in wet conditions. DVS analysis during cycles of relative humidity (RH) between 0 and 95% revealed major differences in water uptake by the filaments spun from hydrogels of different charge density (CNF and TEMPO-oxidised CNF). It is concluded that the mechanical performance of filaments in the presence of water deteriorates drastically by the same factors that facilitate fibril alignment and, consequently, enhance dry strength. For the most oriented filaments, the maximum water vapour sorption at 95% RH was 39% based on dry weight. PMID:27465828

  12. Electrocoagulation pretreatment of wet-spun acrylic fibers manufacturing wastewater to improve its biodegradability.

    PubMed

    Gong, Chenhao; Zhang, Zhongguo; Li, Haitao; Li, Duo; Wu, Baichun; Sun, Yuwei; Cheng, Yanjun

    2014-06-15

    The electrocoagulation (EC) process was used to pretreat wastewater from the manufacture of wet-spun acrylic fibers, and the effects of varying the operating parameters, including the electrode area/wastewater volume (A/V) ratio, current density, interelectrode distance and pH, on the EC treatment process were investigated. About 44% of the total organic carbon was removed using the optimal conditions in a 100 min procedure. The optimal conditions were a current density of 35.7 mA cm(-2), an A/V ratio of 0.28 cm(-1), a pH of 5, and an interelectrode distance of 0.8 cm. The biodegradability of the contaminants in the treated water was improved by the EC treatment (using the optimal conditions), increasing the five-day biological oxygen demand/chemical oxygen demand ratio to 0.35, which could improve the effectiveness of subsequent biological treatments. The improvement in the biodegradability of the contaminants in the wastewater was attributed to the removal and degradation of aromatic organic compounds, straight-chain paraffins, and other organic compounds, which we identified using gas chromatography-mass spectrometry and Fourier transform infrared spectroscopy. The EC process was proven to be an effective alternative pretreatment for wastewater from the manufacture of wet-spun acrylic fibers, prior to biological treatments. PMID:24813666

  13. Nanoporous Ag prepared from the melt-spun Cu-Ag alloys

    NASA Astrophysics Data System (ADS)

    Li, Guijing; Song, Xiaoping; Sun, Zhanbo; Yang, Shengchun; Ding, Bingjun; Yang, Sen; Yang, Zhimao; Wang, Fei

    2011-07-01

    Nanoporous Ag ribbons with different morphology and porosity were achieved by the electrochemical corrosion of the melt-spun Cu-Ag alloys. The Cu-rich phase in the alloys was removed, resulting in the formation of the nanopores distributed across the whole ribbon. It is found that the structures, morphology and porosity of the nanoporous Ag ribbons were dependent on the microstructures of the parent alloys. The most of ligaments presented a rod-like shape due to the formation of pseudoeutectic microstructure in the melt-spun Cu 55Ag 45 and Cu 70Ag 30 alloys. For nanoporous Ag prepared from Cu 85Ag 15 alloys, the ligaments were camber-like because of the appearance of the divorced microstructures. Especially, a novel bamboo-grove-like structure could be observed at the cross-section of the nanoporous Ag ribbons. The experiment reveals that nanoporous Ag ribbons exhibited excellent enhancement of surface-enhanced Raman scattering (SERS) effect, but a slight difference existed due to the discrepancy of their morphology.

  14. Strength and Water Interactions of Cellulose I Filaments Wet-Spun from Cellulose Nanofibril Hydrogels

    PubMed Central

    Lundahl, Meri J.; Cunha, A. Gisela; Rojo, Ester; Papageorgiou, Anastassios C.; Rautkari, Lauri; Arboleda, Julio C.; Rojas, Orlando J.

    2016-01-01

    Hydrogels comprising cellulose nanofibrils (CNF) were used in the synthesis of continuous filaments via wet-spinning. Hydrogel viscosity and spinnability, as well as orientation and strength of the spun filaments, were found to be strongly affected by the osmotic pressure as determined by CNF surface charge and solid fraction in the spinning dope. The tensile strength, Young’s modulus and degree of orientation (wide-angle X-ray scattering, WAXS) of filaments produced without drawing were 297 MPa, 21 GPa and 83%, respectively, which are remarkable values. A thorough investigation of the interactions with water using dynamic vapour sorption (DVS) experiments revealed the role of sorption sites in the stability of the filaments in wet conditions. DVS analysis during cycles of relative humidity (RH) between 0 and 95% revealed major differences in water uptake by the filaments spun from hydrogels of different charge density (CNF and TEMPO-oxidised CNF). It is concluded that the mechanical performance of filaments in the presence of water deteriorates drastically by the same factors that facilitate fibril alignment and, consequently, enhance dry strength. For the most oriented filaments, the maximum water vapour sorption at 95% RH was 39% based on dry weight. PMID:27465828

  15. The anisotropic mechanical behaviour of electro-spun biodegradable polymer scaffolds: Experimental characterisation and constitutive formulation.

    PubMed

    Limbert, Georges; Omar, Rodaina; Krynauw, Hugo; Bezuidenhout, Deon; Franz, Thomas

    2016-01-01

    Electro-spun biodegradable polymer fibrous structures exhibit anisotropic mechanical properties dependent on the degree of fibre alignment. Degradation and mechanical anisotropy need to be captured in a constitutive formulation when computational modelling is used in the development and design optimisation of such scaffolds. Biodegradable polyester-urethane scaffolds were electro-spun and underwent uniaxial tensile testing in and transverse to the direction of predominant fibre alignment before and after in vitro degradation of up to 28 days. A microstructurally-based transversely isotropic hyperelastic continuum constitutive formulation was developed and its parameters were identified from the experimental stress-strain data of the scaffolds at various stages of degradation. During scaffold degradation, maximum stress and strain in circumferential direction decreased from 1.02 ± 0.23 MPa to 0.38 ± 0.004 MPa and from 46 ± 11 % to 12 ± 2 %, respectively. In longitudinal direction, maximum stress and strain decreased from 0.071 ± 0.016 MPa to 0.010 ± 0.007 MPa and from 69 ± 24 % to 8 ± 2 %, respectively. The constitutive parameters were identified for both directions of the non-degraded and degraded scaffold for strain range varying between 0% and 16% with coefficients of determination r(2)>0.871. The six-parameter constitutive formulation proved versatile enough to capture the varying non-linear transversely isotropic behaviour of the fibrous scaffold throughout various stages of degradation. PMID:26301317

  16. A study on the magnetic properties of melt spun Co-Hf-Zr-B nanocomposite ribbons

    NASA Astrophysics Data System (ADS)

    Chang, H. W.; Lin, Y. H.; Shih, C. W.; Chang, W. C.; Shaw, C. C.

    2014-05-01

    Magnetic properties of melt spun Co86.5Hf11.5-xZrxB2 (x = 0-5) ribbons have been investigated. For the ribbons spun at the wheel speed of 40 m/s, hard magnetic properties with high energy product ((BH)max) of 34.4-52.8 kJ/m3 and intrinsic coercivity (iHc) of 176-216 kA/m were obtained for x = 0-2, but soft magnetic behavior was observed for x = 3-5 due to the appearance of the amorphous phase. By annealing the ribbons with x = 3-5, hard magnetic properties were improved arisen from the formation of magnetically hard phase. The variation of magnetic properties for Co86.5Hf11.5-xZrxB2 ribbons was correlated to microstructure change. Proper Zr substitution for Hf was helpful in refining the grain size from 10-35 nm for x = 0 to 5-15 nm for x = 1, and thus improving the magnetic properties effectively. The optimal hard magnetic properties of Co86.5Hf10.5Zr1B2 ribbons might be originated from the fine magnetically hard Co11(Hf, Zr)2 phase, and the exchange coupling effect among grains and/or with the face-center-cubic Co phase.

  17. Blow-spun chitosan/PEG/PLGA nanofibers as a novel tissue engineering scaffold with antibacterial properties.

    PubMed

    Bienek, Diane R; Hoffman, Kathleen M; Tutak, Wojtek

    2016-09-01

    Blow spinning is continuing to gain attention in tissue engineering, as the resultant nanofibrous structures can be used to create a biomimetic environment. In this study, blow spinning was used to construct nanofiber scaffolds with up to 10 % chitosan and poly(DL-lactide-co-glycolide) in the absence or presence of poly(ethylene glycol). Scanning electron microscopy demonstrated that nanofibers were distributed randomly to form three-dimensional mats. With respect to chitosan concentration, the average fiber diameter did not differ statistically in either the absence or presence of poly(ethylene glycol). In poly(ethylene glycol)-formulations, the average fiber diameter ranged from (981.9 ± 611.3) nm to (1139.2 ± 814.2) nm. In vitro cellular metabolic activity and proliferation studies using keratinized rat squamous epithelial cells (RL-65) showed that cytocompatibility was not compromised with the addition of poly(ethylene glycol). The cell responses at lower (1 and 2.5 %) chitosan concentrations were not significantly different from the groups without chitosan or no scaffold when cultivated for 3, 6, or 9 days. However, >15 % reduction in cellular responses were observed at 10 % chitosan. In presence of poly(ethylene glycol), nearly a 1-log incremental reduction in the number of colony forming units of Streptococcus mutans occurred as the chitosan concentration increased from 0-1 to 2.5 %. Bacterial preparations tested with poly(ethylene glycol) and 5 or 10 % chitosan were not significantly different than the positive kill control. Taken together, the most favorable conditions for attaining cytocompatibility and maintaining antibacterial functionality existed in poly(ethylene glycol)/poly(DL-lactide-co-glycolide) blow-spun scaffolds with integrated 1 or 2.5 % chitosan. PMID:27568217

  18. Maximum potential erosion and inundation of seven interior salt domes

    SciTech Connect

    Aronow, S.

    1982-08-01

    Seven interior salt domes have been evaluated in regard to erosion or inundation due to natural events. The most likely possibility of either event occurring would be associated with continental glaciation. The domes were evaluated based on maximum previous sea level changes due to glaciation and effects caused by melting of existing ice sheets. Results are listed for each of the seven domes. Past history indicates a likelihood of returning to a glacial period. The subsequent fall of sea level may cause regrading of streams in the area. A conservative evaluation of this phenomenon was performed and the results are reported.

  19. Merkel cells and touch domes: More than mechanosensory functions?

    PubMed Central

    Xiao, Ying; Williams, Jonathan S.; Brownell, Isaac

    2014-01-01

    The touch dome is an innervated structure in the epidermis of mammalian skin. Composed of specialized keratinocytes and neuroendocrine Merkel cells, the touch dome has distinct molecular characteristics compared to the surrounding epidermal keratinocytes. Much of the research on Merkel cell function has focused on their role in mechanosensation, specifically light-touch. Recently, more has been discovered about Merkel cell molecular characteristics and their cells of origin. Here we review Merkel cell and touch dome biology, and discuss potential functions beyond mechanosensation. PMID:24862916

  20. Scalloped margin domes: What are the processes responsible and how do they operate?

    NASA Technical Reports Server (NTRS)

    Bulmer, M. H.; Guest, J. E.; Michaels, G.; Saunders, S.

    1993-01-01

    Studies of scalloped margin domes (SMD) indicate the scallops are the result of slope failure. SMD's have similar but smaller average diameters (26.5 km) to unmodified domes (29.8 km), and the majority plot at altitudes ranging from 0.5-4.7 km, relative to the mean planetary diameter. A range of morphological types exist from those least modified to those that show heavy modification. Of the 200 SMD's examined, 33 have clearly discernible debris aprons. Examination and comparison of debris aprons with mass movement features on the Moon, Mars, and in sub-aerial and submarine environments on Earth using H/L against area (km(sup 2)), suggests there are three main types of failure; debris avalanche, slumps, and debris flow. The five examples representing the morphological range within the SMD's, show the different modified forms and the different types of slope failures that have occurred.

  1. 2. EXTERIOR OBLIQUE VIEW OF BUILDING 218 WITH DOMES TO ...

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

    2. EXTERIOR OBLIQUE VIEW OF BUILDING 218 WITH DOMES TO THE RIGHT, LOOKING NORTHWEST. - Mill Valley Air Force Station, Consolidated Open Mess, East Ridgecrest Boulevard, Mount Tamalpais, Mill Valley, Marin County, CA

  2. 4. FACING EAST ACROSS BRIDGE AT HALF DOME WITH BICYCLE ...

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

    4. FACING EAST ACROSS BRIDGE AT HALF DOME WITH BICYCLE PATH MARKERS IN FOREGROUND AND ELECTRICAL TRANSFORMER FOR CAMPGROUND TO RIGHT. - Ahwahnee Bridge, Spanning Merced River on service road, Yosemite Village, Mariposa County, CA

  3. Fourth floor rooftop corner detail, looking south. Note Capitol Dome ...

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

    Fourth floor rooftop corner detail, looking south. Note Capitol Dome and Washington Monument in distance. - Chesapeake & Potomac Telephone Company Warehouse, 1111 North Capitol Street, NE, Washington, District of Columbia, DC

  4. 4. WASHBURN POINT VISTA AREA. HALF DOME AT CENTER REAR. ...

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

    4. WASHBURN POINT VISTA AREA. HALF DOME AT CENTER REAR. LOOKING NE. GIS: N-37 43 13.7 / W-119 34 23.0 - Glacier Point Road, Between Chinquapin Flat & Glacier Point, Yosemite Village, Mariposa County, CA

  5. 1. PARKING LOT AT GLACIER POINT. HALF DOME AT CENTER ...

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

    1. PARKING LOT AT GLACIER POINT. HALF DOME AT CENTER REAR. LOOKING NE. GIS: N-36 43 45.8 / W-119 34 14.1 - Glacier Point Road, Between Chinquapin Flat & Glacier Point, Yosemite Village, Mariposa County, CA

  6. 5. GLACIER POINT ROAD VIEW AT SENTINEL DOME PARKING AREA. ...

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

    5. GLACIER POINT ROAD VIEW AT SENTINEL DOME PARKING AREA. LOOKING E. GIS: N-37 42 43.8 / W-119 35 12.1 - Glacier Point Road, Between Chinquapin Flat & Glacier Point, Yosemite Village, Mariposa County, CA

  7. SURVEY AND EVALUATION OF FINE BUBBLE DOME DIFFUSER AERATION EQUIPMENT

    EPA Science Inventory

    This research project was initiated with the overall objective of better defining the oxygen transfer performance, operation and maintenance (O&M) requirements, and proper design approaches for fine bubble dome diffuser aeration systems used in activated sludge wastewater treatme...

  8. INTERIOR STRUCTURAL DETAIL, INSIDE OF DRUM UNDER DOME ON STAIRS, ...

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

    INTERIOR STRUCTURAL DETAIL, INSIDE OF DRUM UNDER DOME ON STAIRS, LOOKING SOUTH. - Colt Fire Arms Company, East Armory Building, 36-150 Huyshope Avenue, 17-170 Van Dyke Avenue, 49 Vredendale Avenue, Hartford, Hartford County, CT

  9. DOME, NORTH ARMORY ON LEFT, OBLIQUE VIEW FROM SOUTHWEST. ...

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

    DOME, NORTH ARMORY ON LEFT, OBLIQUE VIEW FROM SOUTHWEST. - Colt Fire Arms Company, East Armory Building, 36-150 Huyshope Avenue, 17-170 Van Dyke Avenue, 49 Vredendale Avenue, Hartford, Hartford County, CT

  10. 8. Detail view of steam dome attached to top of ...

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

    8. Detail view of steam dome attached to top of Lancashire double flue boiler. - Hacienda Azucarera El Coto, Sugar Mill Ruins, .5 Mi. SW of Rt. 347 Bridge Over Guanajibo River, San German, San German Municipio, PR

  11. View of Statue of Freedom atop the Capitol Dome but ...

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

    View of Statue of Freedom atop the Capitol Dome but under scaffolding - U.S. Capitol, Statue of Freedom, Intersection of North, South, & East Capitol Streets & Capitol Mall, Washington, District of Columbia, DC

  12. STEEL TRUSS TENSION RING SUPPORTING DOME ROOF. TENSION RING COVERED ...

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

    STEEL TRUSS TENSION RING SUPPORTING DOME ROOF. TENSION RING COVERED BY ARCHITECTURAL FINISH. TENSION RING ROLLER SUPPORT AT COLUMN OBSCURED BY COLUMN COVERINGS. - Houston Astrodome, 8400 Kirby Drive, Houston, Harris County, TX

  13. Preliminary paragenetic interpretation of the Quaternary topaz rhyolite lava domes of the Blackfoot volcanic field, southeastern Idaho

    NASA Astrophysics Data System (ADS)

    Lochridge, W. K., Jr.; McCurry, M. O.; Goldsby, R.

    2015-12-01

    The Quaternary topaz rhyolite lava domes of the bimodal, basalt-dominated Blackfoot volcanic field (BVF), SE Idaho occur in three clusters. We refer to these as the China Hat lava dome field (southernmost; ~ 57 ka), and the 1.4 to 1.5 Ma Sheep Island and White Mountain (northernmost) lava dome fields. The rhyolites and surrounding, more voluminous basalt lavas closely resemble coeval Quaternary rocks erupted to the north along the Eastern Snake River Plain segment of the Yellowstone-Snake River Plain volcanic track. However rhyolites in BVF are distinguished by having more evolved Sr- and Nd-isotopic ratios, as well as having phenocryst assemblages that includes hydrous phases (biotite and hornblende), thorite, and vapor-phase topaz. This study seeks to improve our understanding of the unique conditions of magma evolution that led to these differences. We focus on textural features of major and accessory phenocrysts as a basis for inferring paragenesis for rhyolites from the China Hat lava dome field. Preliminary work indicates that there are three sequentially formed populations of textures among magmatic phases: 1. population of anhedral quartz and plagioclase; 2. population of euhedral grains that includes quartz, sandine, plagioclase, biotite, hornblende, Fe-Ti oxides, zircon and apatite; 3. boxy cellular (skeletal?) sanidine and quartz. We speculate that the first population are resorbed antecrysts, the second formed prior to eruption as autocrysts (at or near equilibrium?), and the third formed soon before or during eruption.

  14. Snodar: 2009 performance at Dome A, Antarctica

    NASA Astrophysics Data System (ADS)

    Bonner, Colin S.; Ashley, Michael C. B.; Bradley, Stuart G.; Cui, Xiangqun; Feng, Longlong; Gong, Xuefei; Lawrence, Jon S.; Luong-van, Daniel M.; Shang, Zhaohui; Storey, John W. V.; Wang, Lifan; Yang, Huigen; Yang, Ji; Zhou, Xu; Zhu, Zhenxi

    2010-07-01

    Snodar is a high resolution acoustic radar designed specifically for profiling the atmospheric boundary layer on the high Antarctic plateau. Snodar profiles the atmospheric temperature structure function constant to a vertical resolution of 1 m or better with a minimum sample height of 8 m. The maximum sampling height is dependent on atmospheric conditions but is typically at least 100 m. Snodar uses a unique in-situ intensity calibration method that allows the instrument to be autonomously recalibrated throughout the year. The instrument is initially intensity calibrated against tower-mounted differential microthermal sensors. A calibration sphere is located in the near-field of the antenna to provide a fixed echo of known intensity, allowing the instrument to be continuously re-calibrated once deployed. This allows snow accumulation, transducer wear and system changes due to temperature to be monitored. Year-round power and communications are provided by the PLATO facility. This allows processed data to be downloaded every 6 hours while raw data is stored on-site for collection the following summer. Over 4 million processed samples have been downloaded through PLATO to date. We present signal attenuation from accumulation of snow and ice on Snodar's parabolic reflector during the 2009 at Dome A.

  15. Phase competition in trisected superconducting dome

    PubMed Central

    Vishik, I. M.; Hashimoto, M.; He, Rui-Hua; Lee, Wei-Sheng; Schmitt, Felix; Lu, Donghui; Moore, R. G.; Zhang, C.; Meevasana, W.; Sasagawa, T.; Uchida, S.; Fujita, Kazuhiro; Ishida, S.; Ishikado, M.; Yoshida, Yoshiyuki; Eisaki, Hiroshi; Hussain, Zahid; Devereaux, Thomas P.; Shen, Zhi-Xun

    2012-01-01

    A detailed phenomenology of low energy excitations is a crucial starting point for microscopic understanding of complex materials, such as the cuprate high-temperature superconductors. Because of its unique momentum-space discrimination, angle-resolved photoemission spectroscopy (ARPES) is ideally suited for this task in the cuprates, where emergent phases, particularly superconductivity and the pseudogap, have anisotropic gap structure in momentum space. We present a comprehensive doping- and temperature-dependence ARPES study of spectral gaps in Bi2Sr2CaCu2O8+δ, covering much of the superconducting portion of the phase diagram. In the ground state, abrupt changes in near-nodal gap phenomenology give spectroscopic evidence for two potential quantum critical points, p = 0.19 for the pseudogap phase and p = 0.076 for another competing phase. Temperature dependence reveals that the pseudogap is not static below Tc and exists p > 0.19 at higher temperatures. Our data imply a revised phase diagram that reconciles conflicting reports about the endpoint of the pseudogap in the literature, incorporates phase competition between the superconducting gap and pseudogap, and highlights distinct physics at the edge of the superconducting dome. PMID:23093670

  16. Dome houses and energy conservation: an introductory bibliography. [38 references to dome efficiency

    SciTech Connect

    Not Available

    1983-01-01

    The appearance of geodesic domes in conventional neighborhoods is recent. The current popularity of these spherical designs is due to their energy efficiency. Some manufacturers have claimed over 40% efficiency improvement over conventional homes of the same size. A host of low utility bills across the country is now backing up these claims. This bibliography concentrates on the period from 1960 to the present, although there are a few entries from earlier periods. Most of the material is available in articles rather than books.

  17. Modified sensing element of a fibre-optic current sensor based on a low-eigenellipticity spun fibre

    SciTech Connect

    Przhiyalkovsky, Ya V; Morshnev, S K; Starostin, N I; Gubin, V P

    2014-10-31

    We have proposed and investigated a modified sensing element of a spun fibre current sensor for the case when the beat length of the built-in linear birefringence of the fibre is equal to or less than the spin pitch of its helical structure. The proposed configuration makes it possible to restore the interferometer contrast reduced because of the decrease in the ellipticity of the wavelength-averaged polarisation state of radiation propagating in such spun fibre. The modified sensing element contains two polarisation state converters: one, located at the spun fibre input, produces polarisation with ellipticity equal to the eigenellipticity of the fibre, and the other ensures conversion of the elliptical polarisation to an orthogonal one through mirror reflection at the fibre output. We have also demonstrated that the magneto-optical sensitivity decreases slightly for the analysed spectrum-averaged parameters of the polarisation state of radiation in the spun fibre. Experimental data lend support to the theoretical predictions. (fibre-optic sensors)

  18. Gradient Distribution of Martensite Phase in Melt-Spun Ribbons of a Fe-Ni-Ti-Al Alloy.

    PubMed

    Bondar, Volodymyr; Danilchenko, Vitalij; Dzevin, Ievgenij

    2016-12-01

    Metallographic, X-ray diffraction and magnetometric analysis were used to study the regularities of martensitic transformation in melt-spun ribbons of a Fe - 28 wt. % Ni - 2.1 wt. % Ti - 2 wt. % Al - 0.05 wt. % C alloy. The substantial differences in volume fractions of the martensite phase in local regions of thin melt-spun ribbons of the alloy are related to the size effect of the transformation and structural inhomogeneity of the ribbons. The distribution of austenitic grain size in different local areas of melt-spun ribbons is significantly different. The principal factor for changing the completeness of the martensitic transformation is the size effect of transformation. Difference in the martensite volume fraction in local regions of a ribbon is mainly determined by the different volume fractions of ultrafine-grained (500-1000 nm) and nanosized (80-100 nm and less) initial austenite grains, in which the transformation was slowed down or completely suppressed. Other factors almost do not affect the completeness of the martensitic transformation. The strong stabilizing effect of the reverse α-γ transformation with respect to the subsequent direct γ-α transformation in the melt-spun ribbons is also related to the grain size effect. PMID:26897002

  19. Gradient Distribution of Martensite Phase in Melt-Spun Ribbons of a Fe-Ni-Ti-Al Alloy

    NASA Astrophysics Data System (ADS)

    Bondar, Volodymyr; Danilchenko, Vitalij; Dzevin, Ievgenij

    2016-02-01

    Metallographic, X-ray diffraction and magnetometric analysis were used to study the regularities of martensitic transformation in melt-spun ribbons of a Fe - 28 wt. % Ni - 2.1 wt. % Ti - 2 wt. % Al - 0.05 wt. % C alloy. The substantial differences in volume fractions of the martensite phase in local regions of thin melt-spun ribbons of the alloy are related to the size effect of the transformation and structural inhomogeneity of the ribbons. The distribution of austenitic grain size in different local areas of melt-spun ribbons is significantly different. The principal factor for changing the completeness of the martensitic transformation is the size effect of transformation. Difference in the martensite volume fraction in local regions of a ribbon is mainly determined by the different volume fractions of ultrafine-grained (500-1000 nm) and nanosized (80-100 nm and less) initial austenite grains, in which the transformation was slowed down or completely suppressed. Other factors almost do not affect the completeness of the martensitic transformation. The strong stabilizing effect of the reverse α-γ transformation with respect to the subsequent direct γ-α transformation in the melt-spun ribbons is also related to the grain size effect.

  20. Structure Study of Cellulose Fibers Wet-Spun from Environmentally Friendly NaOH/Urea Aqueous Solutions

    SciTech Connect

    Chen,X.; Burger, C.; Wan, F.; Zhang, J.; Rong, L.; Hsiao, B.; Chu, B.; Cai, J.; Zhang, L.

    2007-01-01

    In this study, structure changes of regenerated cellulose fibers wet-spun from a cotton linter pulp (degree of polymerization {approx}620) solution in an NaOH/urea solvent under different conditions were investigated by simultaneous synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS). WAXD results indicated that the increase in flow rate during spinning produced a better crystal orientation and a higher degree of crystallinity, whereas a 2-fold increase in draw ratio only affected the crystal orientation. When coagulated in a H{sub 2}SO{sub 4}/Na{sub 2}SO{sub 4} aqueous solution at 15 {sup o}C, the regenerated fibers exhibited the highest crystallinity and a crystal orientation comparable to that of commercial rayon fibers by the viscose method. SAXS patterns exhibited a pair of meridional maxima in all regenerated cellulose fibers, indicating the existence of a lamellar structure. A fibrillar superstructure was observed only at higher flow rates (>20 m/min). The conformation of cellulose molecules in NaOH/urea aqueous solution was also investigated by static and dynamic light scattering. It was found that cellulose chains formed aggregates with a radius of gyration, R{sub g}, of about 232 nm and an apparent hydrodynamic radius, R{sub h}, of about 172 nm. The NaOH/urea solvent system is low-cost and environmentally friendly, which may offer an alternative route to replace more hazardous existing methods for the production of regenerated cellulose fibers.

  1. Subsidence at Boling salt dome: results of multiple resource production

    SciTech Connect

    Mullican, W.F. III

    1988-02-01

    Boling dome (Wharton and Fort Bend Counties) has experienced more overall subsidence and collapse than any other dome in Texas. These processes are directly related to production of sulfur and hydrocarbons from the southeastern quadrant of the dome. Greatest vertical movement due to subsidence and collapse is 35 ft (based on the Boling 7.5 min topographic map, last surveyed in 1953). Most of the subsidence (83%) is attributed to sulfur production, whereas only 11 to 12% can be linked to hydrocarbon production. Reservoir compaction is the dominant mechanism of land subsidence in areas of hydrocarbon production at Boling dome. Trough subsidence, chimneying, plug caving, and piping are the characteristic mechanisms over sulfur fields developed at the salt dome. The structural and hydrologic stability of the surface and subsurface at Boling dome is compromised by these active deformation processes. Damage to pipelines and well-casing strings may result in costly leaks which have the potential of being uncontrollable and catastrophic. Reduction in hydrologic stability may result if natural aquitards are breached and fresh water mixes with saline water or if hydrologic conduits to the diapir are opened, allowing unrestricted dissolution of the salt stock.

  2. Atmospheric Transmission at Dome C between 0 and 10 THz

    NASA Astrophysics Data System (ADS)

    Schneider, N.; Minier, V.; Durand, G.; Tremblin, P.; Urban, J.; Baron, P.

    We present model calculations of the atmospheric transmission for DOME C in Antarctica for frequencies up to 10 THz (30 μm) using the forward model MOLIERE-5. Measurements of precipitable water vapor (pwv), obtained by the SUMMIT radiometer installed at the Concordia station during 2008 and working at a wavelength of 200 μm, are translated into atmospheric transmission using MOLIERE. Quartiles of transmission, calculated from 200 μm data are extrapolated to 350 μm and compared to the CCAT (Cornell-Caltech Atacama Telescope) site in Chile. It turns out that for 25% of the time at DOME C (CCAT), the transmission is around 20% (5%) at 200 μm. This corresponds to a pwv of 0.18 mm for DOME C. At 350 μm, for 50% of time at DOME C (CCAT) the transmission is around 55% (25%). This corresponds to a pwv of 0.22 mm for DOME C. These results show that DOME C is one of the best observing sites on Earth for submm-astronomy with respect to high atmospheric transmission over long time periods.

  3. Developments in the finishing of domes and conformal optics

    NASA Astrophysics Data System (ADS)

    Shorey, Aric B.; Kordonski, William; Tracy, Justin; Tricard, Marc

    2007-04-01

    The final finish and characterization of windows and domes presents a number of difficult challenges. Furthermore, there is a desire to incorporate conformal shapes into next generation imaging and surveillance systems to provide significant advantages in overall component performance. Unfortunately, their constantly changing curvature and steep slopes make fabrication of such shapes incompatible with most conventional polishing and metrology solutions. Two novel types of polishing technology, Magnetorheological Finishing (MRF®) and Magnetorheological Jet (MR Jet TM), along with metrology provided by the Sub-aperture Stitching Interferometer (SSI®) have several unique attributes that give them advantages in enhancing fabrication of hemispherical domes and even conformal shapes. The advantages that MRF brings to the precision finishing of a wide range of shapes such as flats, spheres (including hemispheres), cylinders, aspheres and even freeform optics, has been well documented. The recently developed MR Jet process provides additional benefits, particularly in the finishing the inside of steep concave domes and other irregular shapes. Combining these technologies with metrology techniques, such as the SSI, provides a solution for finishing current and future windows and domes. Recent exciting developments in the finishing of such shapes with these technologies will be presented. These include new advances such as the ability to use the SSI to characterize a range of shapes such as domes and aspheres, as well as progress in using MRF and MR Jet for finishing conventional and conformal windows and domes.

  4. Unique dome design for the SOAR telescope project

    NASA Astrophysics Data System (ADS)

    Teran, Jose U.; Porter, David S.; Hileman, Edward A.; Neff, Daniel H.

    2000-08-01

    The SOAR telescope dome is a 20 meter diameter 5/8 spherical structure built on a rotating steel frame with an over the top nesting shutter and covered with a fiberglass panel system. The insulated fiberglass panel system can be self- supporting and is typically used for radomes on ground based tracking systems. The enclosed observing area is ventilated using a down draft ventilation system. The rotating steel frame is comprised of a ring beam and dual arch girders to provide support to the panel system sections and guide the shutter. The dual door shutter incorporates a unique differential drive system that reduces the complexity of the control system. The dome, shutter and windscreen `track' the telescope for maximum wind protection. The dome rotates on sixteen fixed compliant bogie assemblies. The dome is designed for assembly in sections off the facility and lifted into place for minimal impact on assembly of other telescope systems. The expected cost of the complete dome; including structure, drives, and controls is under 1.7 million. The details covered in this paper are the initial trade-offs and rationale required by SOAR to define the dome, the detailed design performed by M3 Engineering and Technology, and the choices made during the design.

  5. Internal Convection on Ceres: A Possible Explanation for Dome Formation

    NASA Astrophysics Data System (ADS)

    Travis, B. J.; Feldman, W. C.; Sizemore, H. G.; O'Brien, D. P.; Sykes, M. V.

    2015-12-01

    Numerical 2-D whole-body simulations of the evolution of Ceres' internal dynamics and thermal structure over its history indicate that hydrothermal activity is very strong throughout the first half of Ceres' history, gradually weakening thereafter, but still active even today (Travis et al, 2015, 46th LPSC). Large-scale upwelling plumes of muddy water extend from the porous, permeable rocky core through an ocean layer and impinge on the bottom of the ice shell. These upwellings are very long-lasting. In addition, small scale, shorter-lived plumes frequently develop on the upper regions of the large plumes. The large-scale plumes occur at roughly +/- 25 o latitude. Recently, 3-D simulations of a sector of Ceres shows that the upwellings are indeed plumes and not sheets. In the 3-D model, plume diameters in the model are as small as 15-20 km in diameter, up to several 10s of km or more. Relating internal dynamics to surface features is challenging. Linkage to mounds seen on the surface may be possible. There appear to be two classes of mounds: Large domes (10s of km diameter) and small (<15 km diameter). Morphological evidence such as embayment relations imply that large mounds may be extrusive. The source of the small domes is less clear. They could be extrusive, or they could be pingo-like structures that form when large areas of melt are extruded or produced by impact, although they are larger than terrestrial or martian structures. Mound heights are typically no more than 1 - 5 km. One mechanism for generation of these mounds suggested by our modeling is extrusion of mud through fractures in the icy crust. Over-pressuring of upwelling plumes at the base of the icy crust from freezing of neighboring downwellings could generate fractures in a frozen mud crust. As plumes and icy crust cool, a significant volume expansion occurs due to freezing of water to ice. This pressurization is not uniform in space; the still-liquid upwellings will experience overpressure in

  6. Catastrophic lava dome failure at Soufrière Hills Volcano, Montserrat, 12-13 July 2003

    USGS Publications Warehouse

    Herd, Richard A.; Edmonds, Marie; Bass, Venus A.

    2005-01-01

    The lava dome collapse of 12–13 July 2003 was the largest of the Soufrière Hills Volcano eruption thus far (1995–2005) and the largest recorded in historical times from any volcano; 210 million m3 of dome material collapsed over 18 h and formed large pyroclastic flows, which reached the sea. The evolution of the collapse can be interpreted with reference to the complex structure of the lava dome, which comprised discrete spines and shear lobes and an apron of talus. Progressive slumping of talus for 10 h at the beginning of the collapse generated low-volume pyroclastic flows. It undermined the massive part of the lava dome and eventually prompted catastrophic failure. From 02:00 to 04:40 13 July 2003 large pyroclastic flows were generated; these reached their largest magnitude at 03:35, when the volume flux of material lost from the lava dome probably approached 16 million m3 over two minutes. The high flux of pyroclastic flows into the sea caused a tsunami and a hydrovolcanic explosion with an associated pyroclastic surge, which flowed inland. A vulcanian explosion occurred during or immediately after the largest pyroclastic flows at 03:35 13 July and four further explosions occurred at progressively longer intervals during 13–15 July 2003. The dome collapse lasted approximately 18 h, but 170 of the total 210 million m3 was removed in only 2.6 h during the most intense stage of the collapse.

  7. Development of Core Complex Domes Due to Along-Axis Variation in Diking

    NASA Astrophysics Data System (ADS)

    Buck, W. R.; Choi, E.; Tian, X.

    2014-12-01

    Continental and oceanic core complexes are characterized by fairly smooth, unfaulted, but corrugated surfaces of high grade rocks often domed both along and orthogonal to the transport direction. The corrugations, or mega-mullions, are remarkably continuous in the transport direction and may be tens of kilometers long. Spencer [1999] suggests that corrugations with across-transport wavelengths of millimeter to ~25 km scales are formed when the lower plate of a large-offset normal fault is "continuously cast," as warm, ductile mantle and gabbro is pulled up against the cooler upper plate. Continuous casting is widely accepted as a mechanism to form the shorter wavelength corrugations as a result of irregularities of the brittle upper plate surface. However, doming is generally ascribed to upflow of buoyant diapirs or transtensional deformation of the lithosphere. We suggest that doming of core complexes can be a product of continuous casting when a large-offset fault evolves to be curved in plan-view. For oceanic core complexes along-axis variation in magmatism can lead to lateral offset of a detachment fault relative to the spreading axis. We assume that near-ridge normal faults form relatively straight and consider that horizontal offsets in the along-axis position of a large-offset fault (or detachment) result from variations in the rate of magmatic diking. Assuming a sinusoidal variation in the rate of dike opening with distance along the axis the evolution of fault offset and the plan-view shape of the active fault is easy to describe. Because the fault length increases as it is offset, the work to slip on the fault increases with time. Eventually, it should be easier to slip in a new straight fault and the conditions for this can be described with an approximate analytic model. We are developing 3D numerical models to test the predictions of this analytic model and show how the topographic amplitude of the domes depends the fault dip, the amplitude of the

  8. Central pit and dome craters - Exposing the interiors of Ganymede and Callisto

    NASA Technical Reports Server (NTRS)

    Schenk, Paul M.

    1993-01-01

    Central pit craters on Ganymede and Callisto are an unusual crater class, perhaps related to the unusual properties of water ice. The domes and pits form rapidly, on the time scale of the impact itself, rather than by long-term, post-impact intrusion or extrusion. The bright domes in pit craters are most simply explained as the uplift and exposure of relatively ice-rich material from depths of approximately 3.5 to 5 km during impact. The unusual pit morphology on icy satellites may be the result of impact into crust that is mechanically much weaker at shallow depth than on rocky bodies such as the moon. Because crater morphology is strongly dependent on ice-rock composition, the similarity of pit and dome dimensions on Ganymede and Callisto indicates that the structure and rheology of the crusts of these bodies are very similar, and have been for several billion years. Pit crater morphology indicates that the crusts of both satellites are probably ice-rich and differentiated.

  9. Consolidation of Nd-Fe-B melt-spun ribbon by compression shearing method

    SciTech Connect

    Saito, Tetsuji; Takeishi, Hiroyuku; Nakayama, Noboru

    2007-05-01

    Commercially available Nd-Fe-B melt-spun ribbons (MQ powders) were consolidated at temperatures ranging from room temperature to 573 K in ambient atmosphere by the compression shearing method. The resultant bulk materials consisted of the Nd{sub 2}Fe{sub 14}B phase together with a small amount of the soft magnetic {alpha}-iron phase. The bulk material consolidated at room temperature was magnetically isotropic as was the case for the MQ powders. On the other hand, the bulk material consolidated at 573 K was found to be magnetically anisotropic and showed a remanence of 9.2 kG, higher than that of the MQ powders.

  10. Optimizing Aqua Splicer Parameters for Lycra-Cotton Core Spun Yarn Using Taguchi Method

    NASA Astrophysics Data System (ADS)

    Midha, Vinay Kumar; Hiremath, ShivKumar; Gupta, Vaibhav

    2015-10-01

    In this paper, optimization of the aqua splicer parameters viz opening time, splicing time, feed arm code (i.e. splice length) and duration of water joining was carried out for 37 tex lycra-cotton core spun yarn for better retained splice strength (RSS%), splice abrasion resistance (RYAR%) and splice appearance (RYA%) using Taguchi experimental design. It is observed that as opening time, splicing time and duration of water joining increase, the RSS% and RYAR% increases, whereas increase in feed arm code leads to decrease in both. The opening time and feed arm code do not have significant effect on RYA%. The optimum RSS% of 92.02 % was obtained at splicing parameters of 350 ms opening time, 180 ms splicing time, 65 feed arm code and 600 ms duration of water joining.

  11. Effect of magnetic fields on melt-spun Nd2Fe14B-based ribbons

    NASA Astrophysics Data System (ADS)

    Van Nguyen, Vuong; Rong, Chuanbing; Ding, Yong; Liu, J. Ping

    2012-04-01

    The effect of a magnetic field on microstructure and magnetic properties of Nd2Fe14B-based melt-spun ribbons is investigated. The magnetic field was applied in perpendicular or parallel direction to the ribbon plane during quench with a field strength up to several kilo Oersteds. The XRD patterns and TEM graphs show a strong grain size reduction upon the magnetic field application. The magnetic field also enhances the (00l) texture of ribbons when the field is perpendicular to the ribbon plane. The refined microstructure with significantly reduced grain size leads to enhanced magnetic exchange interactions between the hard and soft phases in the Nd2Fe14B/Fe nanocomposite ribbons. This magnetic field-assisted melt-spinning technique is promising for producing nanocomposite magnets with enhanced energy density.

  12. Temporal Evolution of Magma Flow Conditions during Dome Growth, Insights from Numerical Modelling.

    NASA Astrophysics Data System (ADS)

    Chevalier, L. A. C.; Collombet, M.; Pinel, V.

    2015-12-01

    Transitions from effusive to explosive regime at andesitic volcanoes are almost unpredictable at the moment. The reliability of empirical methods based on geophysical precursory patterns is still debated. A better understanding of the physical processes happening in the volcanic system before explosions and associated geophysical signals is needed. At andesitic volcanoes, dome building is often observed during the effusive phase. The weight of a forming dome is expected to have several effects: 1) It obviously induces a ground subsidence in the near field; 2) pressure increase at the top of the conduit causes magma properties and flow conditions evolution; 3) it increases pressure in the surrounding rock such decreasing rock permeability and thus gas loss through the conduit walls, possibly leading to gas pressurisation. Here we use numerical models that couple realistic magma flow conditions in the upper conduit with solid deformation, in 2D axisymmetry, to investigate all these effects. Subsiding effect due to the dome emplacement is simulated by a pressure loading of the rock surrounding the conduit. From realistic initial magma flow conditions in effusive regime (Collombet, 2009), we apply increasing pressure at the conduit top. Volatile solubility increases with pressure, then dome growth causes a decrease of magma porosity and permeability at the top of the conduit. This also causes a decrease of magma viscosity. From magma flow model, we extract pressure and shear stress conditions at the conduit wall, and apply them to the surrounding rock for ground deformation calculation . Darcy flow model is used to study the impacts of permeability decrease inside the conduit and in the surrounding rock on gas loss cinematics. Permeability decrease in the conduit and pressure increase in the surrounding rock cause gas pressurisation.

  13. Interaction of mid-latitude air masses with the polar dome area during RACEPAC and NETCARE

    NASA Astrophysics Data System (ADS)

    Bozem, Heiko; Hoor, Peter; Koellner, Franziska; Kunkel, Daniel; Schneider, Johannes; Schulz, Christiane; Herber, Andreas; Borrmann, Stephan; Wendisch, Manfred; Ehrlich, Andre; Leaitch, Richard; Willis, Megan; Burkart, Julia; Thomas, Jennie; Abbatt, Jon

    2016-04-01

    We present aircraft based trace gas measurements in the Arctic during RACEPAC (2014) and NETCARE (2014 and 2015) with the Polar 6 aircraft of Alfred Wegener Institute (AWI) covering an area from 134°W to 17°W and 68°N to 83°N. We focus on cloud, aerosol and general transport processes of polluted air masses into the high Arctic. Based on CO and CO2 measurements and kinematic 10-day back trajectories as well as Flexpart particle dispersion modeling we analyze the transport regimes of mid-latitude air masses traveling to the high Arctic prevalent during spring (RACEPAC 2014, NETCARE 2015) and summer (NETCARE 2014). In general more northern parts of the high Arctic (Lat > 75°N) were relatively unaffected from mid-latitude air masses. In contrast, regions further south are influenced by air masses from Asia and Russia (eastern part of Canadian Arctic and European Arctic) as well as from North America (central and western parts of Canadian Arctic). The transition between the mostly isolated high Arctic and more southern regions indicated by tracer gradients is remarkably sharp. This allows for a chemical definition of the Polar dome based on the variability of CO and CO2 as a marker. Isentropic surfaces that slope from the surface to higher altitudes in the high Arctic form the polar dome that represents a transport barrier for mid-latitude air masses to enter the lower troposphere in the high Arctic. Synoptic-scale weather systems frequently disturb this transport barrier and foster the exchange between air masses from the mid-latitudes and polar regions. This can finally lead to enhanced pollution levels in the lower polar troposphere. Mid-latitude pollution plumes from biomass burning or flaring entering the polar dome area lead to an enhancement of 30% of the observed CO mixing ratio within the polar dome area.

  14. Explosive destruction of a Pliocene hot lava dome underwater: Dogashima (Japan)

    NASA Astrophysics Data System (ADS)

    Jutzeler, Martin; McPhie, Jocelyn; Allen, Sharon R.

    2015-10-01

    Transition from effusive to explosive volcanism is common during subaerial eruptions, and here we demonstrate that this behavior is also possible underwater. The pyroclastic facies produced underwater are distinctive and can be used to distinguish subaqueous from subaerial eruptions and depositional settings. The Pliocene Dogashima Formation (Izu Peninsula, Japan) is a pumice-rich succession originally deposited in an open-marine, below wave-base setting (Jutzeler et al., 2014a). A thick, clast-supported, gray andesite breccia composed of very coarse, dense andesite clasts with quenched margins was sourced from disintegration of an active lava dome. Overall, the gray andesite breccia is gradationally to sharply overlain by thick, graded, clast-supported white pumice breccia chiefly composed of angular pumice clasts and free broken crystals. Regional setting and distinctive facies show that this succession was produced by a fully underwater, magmatic volatile-driven, pumice-forming explosive eruption. The gradational contact between the two breccias, compositional similarities, rare mingled clasts, and fluidal textures in the gray andesite clasts suggest that the explosive eruption destroyed a hot lava dome and generated an eruption-fed, high-concentration density current. In most places, the coarsest hot lava dome fragments were deposited first, followed by the lower density white pumice clasts. The low amount of fine (< 2 mm) components, well-developed hydraulically controlled grading and sorting, clast angularity, and very coarse dome-derived clasts, some including well-defined quenched margins and common fluidal textures, distinguish the products of subaqueous effusive-to-explosive eruptions from their subaerial counterparts.

  15. Volcán de Colima dome collapse of July, 2015 and associated pyroclastic density currents

    NASA Astrophysics Data System (ADS)

    Reyes-Dávila, Gabriel A.; Arámbula-Mendoza, Raúl; Espinasa-Pereña, Ramón; Pankhurst, Matthew J.; Navarro-Ochoa, Carlos; Savov, Ivan; Vargas-Bracamontes, Dulce M.; Cortés-Cortés, Abel; Gutiérrez-Martínez, Carlos; Valdés-González, Carlos; Domínguez-Reyes, Tonatiuh; González-Amezcua, Miguel; Martínez-Fierros, Alejandro; Ramírez-Vázquez, Carlos Ariel; Cárdenas-González, Lucio; Castañeda-Bastida, Elizabeth; Vázquez Espinoza de los Monteros, Diana M.; Nieto-Torres, Amiel; Campion, Robin; Courtois, Loic; Lee, Peter D.

    2016-06-01

    During July 10th-11th 2015, Volcán de Colima, Mexico, underwent its most intense eruptive phase since its Subplinian-Plinian 1913 AD eruption. Production of scoria coincident with elevated fumarolic activity and SO2 flux indicate a significant switch of upper-conduit dynamics compared with the preceding decades of dome building and vulcanian explosions. A marked increase in rockfall events and degassing activity was observed on the 8th and 9th of July. On the 10th at 20:16 h (Local time = UTM - 6 h) a partial collapse of the dome generated a series of pyroclastic density currents (PDCs) that lasted 52 min and reached 9.1 km to the south of the volcano. The PDCs were mostly channelized by the Montegrande and San Antonio ravines, and produced a deposit with an estimated volume of 2.4 × 106 m3. Nearly 16 h after the first collapse, a second and larger collapse occurred which lasted 1 h 47 min. This second collapse produced a series of PDCs along the same ravines, reaching a distance of 10.3 km. The total volume calculated for the PDCs of the second event is 8.0 × 106 m3. Including associated ashfall deposits, the two episodes produced a total of 14.2 × 106 m3 of fragmentary material. The collapses formed an amphitheater-shaped crater open towards the south. We propose that the dome collapse was triggered by arrival of gas-rich magma to the upper conduit, which then boiled-over and sustained the PDCs. A juvenile scoria sample selected from the second partial dome collapse contains hornblende, yet at an order of magnitude less abundant (0.2%) than that of 1913, and exhibits reaction rims, whereas the 1913 hornblende is unreacted. At present there is no compelling petrologic evidence for imminent end-cycle activity observed at Volcán de Colima.

  16. Interactive property of large thrust sheets with footwall rocks—the Sub thrust interactive duplex hypothesis: A mechanism of dome formation in thrust sheets

    NASA Astrophysics Data System (ADS)

    Hatcher, Robert D.

    1991-06-01

    Recently acquired Appalachian Ultradeep Core Hole (ADCOH) Project site investigation seismic reflection data and geologic data from the Appalachians and several other orogenic belts suggest an important mutually interdependent relationship exists between emplacement of large crystalline thrust sheets and the deforming foreland rocks beneath. This relationship suggests isolated domes beneath crystalline thrust sheets may be produced by passive folding of the sheet as a result of formation of an antiformal stack duplex in the platform sedimentary sequence beneath. Suggestions that domes in crystalline thrust sheets formed by interference of late open folds is doubtlessly still valid in places, but the platform duplex mechanism is probably also valid to explain the late doming of many crystalline and other large thrust sheets. The dome beneath the Shooting Creek and Brasstown Bald windows in the ADCOH site region is imaged as an antiformal stack duplex at depth. The Tallulah Falls dome, Grandfather Mountain and Mountain City windows, and Smokies Foothills duplex in the site region and elsewhere in the southern Blue Ridge are all late isolated domes and all are probably or demonstrably underlain by antiformal stack duplexes beneath the Blue Ridge-Piedmont composite crystalline thrust sheet. The Assynt window and footwall duplex benath the Arnabol and Moine thrusts in Scotland, and the Engadine window in the Alps may be similar structures.

  17. Reactivation of a collisional suture by Miocene transpressional domes associated with the Red River and Song Chay detachment faults, northern Vietnam

    NASA Astrophysics Data System (ADS)

    Osozawa, Soichi; Van Vuong, Nguyen; Van Tich, Vu; Wakabayashi, John

    2015-06-01

    Elongate Miocene gneissose and granitic domes in northern Vietnam formed in a dextral-transpressional ductile shear regime, possibly associated with large-scale restraining step-overs along dextral faults. Initial anticlinal D1 doming involved folding of both basement and hanging wall rocks with D1 secondary folds that verge toward the anticlinal axes. Such folds reflect dome-scale flexural slip folding. With continued shortening, D2 detachment faults developed on the flanks of the anticlines along the hanging wall-basement interface, so that the basement was extruded vertically into the overlying hanging wall rocks. The detachment faults were associated with D2 drag folds that verge away from the anticlinal axes. The hanging wall assemblage lacks a well-ordered stratigraphy, displaying primarily block-in-matrix fabric. We identified bedded cherts, associated with umbers and alkalic basaltic intrusions within these hanging wall rocks, a first report of such rocks from Vietnam. The association of cherts, umbers, and basaltic intrusions and extrusions with block-in-matrix units with clastic rocks strongly suggest that the hanging wall rocks comprise part of a subduction complex. Because the base of a subduction complex is a former subduction megathrust horizon, the hanging wall-basement interface represents a reactivated collisional suture. Such a suture was probably associated with the Indosinian orogeny, and the basement should be the Indochina continental block. This structure may have influenced the position of Miocene dextral faulting in addition to controlling the position of the dome detachments. The well-known Red River fault marks the boundary of one of the domes, but in this region it appears to be a detachment (normal) fault rather than a dextral strike-slip fault. However, the association with the dome evolution with large-scale restraining step-overs suggests that dextral faulting associated with dome development may lie further away from the dome axes

  18. Geostrophic circulation between the Costa Rica Dome and Central America

    NASA Astrophysics Data System (ADS)

    Brenes, C. L.; Lavín, M. F.; Mascarenhas, Affonso S.

    2008-05-01

    The geostrophic circulation between the Costa Rica Dome and Central America is described from CTD observations collected in two surveys: (a) The Wet Cruise in September-October 1993, and the Jet Cruise in February-March 1994. Poleward coastal flow was present on both occasions, but the transition from flow around the dome to the poleward Costa Rica Coastal Current flow was quite tortuous because of the presence of mesoscale eddies. In particular, a warm anticyclonic eddy was found off the Gulf of Fonseca during both cruises, at an almost identical position and with similar dimensions (150 m deep, 250 km in diameter) and surface speed (0.5 m s -1). In the Gulf of Panama, poleward flow was also observed, weaker in February-March 1994 than in September-October 1993, when it penetrated to 600 m depth and transported 8.5 Sv. In September-October 1993, the current between the dome and the coast was mostly ˜100 m deep and weak (˜0.15 m s -1), although in its southern side it was deeper (˜450 m) and faster at 0.3 m s -1. The poleward transport between the dome and the coast was ˜7 Sv. In February-March 1994 the Costa Rica Dome was a closed ring adjacent to the continental shelf, ˜500 km in diameter, at least 400 m deep, had geostrophic surface speeds ˜0.25 m s -1, and subsurface maximum speed (0.15-0.20 m s -1) at ˜180 m depth; the associated uplift of the isotherms was ˜150 m. The flow in the south part of the dome splits into two branches, the weakest one going around the dome and the strongest one continuing east and turning south before reaching the Gulf of Panama.

  19. Wind tunnel study of an observatory dome with a circular aperture

    NASA Technical Reports Server (NTRS)

    Zilliac, Gregory G.; Cliffton, Ethan W.

    1990-01-01

    Results of a wind tunnel test of a new concept in observatory dome design, the Fixed Shutter Dome are presented. From an aerodynamic standpoint, the new dome configuration is similar in overall shape to conventional observatory domes, with the exception of the telescope viewing aperture. The new design consists of a circular aperture of reduced area in contrast to conventional domes with rectangular or slotted openings. Wind tunnel results of a side-by-side comparison of the new dome with a conventional dome demonstrate that the mean and fluctuating velocity through the aperture and in the center of the new dome configuration are lower than those of conventional domes, thus reducing the likelihood of telescope flow-induced vibration.

  20. The behaviour of repaired composite domes subjected to external pressure

    NASA Astrophysics Data System (ADS)

    Mistry, J.; Levy-Neto, F.

    1992-07-01

    Six hemispherical and four torispherical composite plastic domes reinforced with either carbon or E-glass woven fabrics or a combination of both have been tested under external pressure. The domes were prepared using male or female moulds and employed the hand lay-up/vacuum bag method for their manufacture. The domes were observed to fail either by buckling or as a result of material failure. Both modes of failure were usually located at the meridian having the minimum average thickness. These domes were then repaired using a recommended technique and retested. It has been shown that the integrity of the repaired zones was guaranteed and further damage to the domes during retesting moved to new locations usually corresponding to the areas of the new minimum average thickness meridian. Two computer programs based on finite difference and finite element methods were employed to predict the critical buckling or material failure loads. The theoretical predictions were shown to correlate very well with the experimental results.

  1. Fracture fillings and intrusive pyroclasts, Inyo Domes, California

    SciTech Connect

    Heiken, G.; Wohletz, K.; Eichelberger, J.

    1988-05-10

    Fractures containing juvenile magmatic pyroclasts were encountered during drilling into a 600-year-old feeder dike beneath the Inyo Domes chain, California. The Inyo Domes consist of a north-south trending, 10-km-long chain of domes, rhyolitic tuff rings, and phreatic craters. Boreholes were cored through the 51-m-diameter conduit of Obsidian Dome, the largest of the Inyo Domes, and through an unvented portion of the intrusion (dike) 1 km to the south. Pyroclast-bearing fractures were intersected in both holes: (1) 7- to 40-cm-thick fractures in welded basaltic scoria and quartz monzonite country rock are adjacent to the conduit at depths of 400--411 m and 492--533 m; they contain gray, clastic deposits, which show truncated cross bedding and convolute bedding; (2) adjacent to the dike, massive fracture fillings occur at depths of 289--302 m (129 m east of the dike) and 366--384 m (95--87 m east of the dike).

  2. Contemporary doming of the Adirondack mountains: Further evidence from releveling

    USGS Publications Warehouse

    Isachsen, Y.W.

    1981-01-01

    The Adirondack Mountains constitute an anomalously large, domical uplift on the Appalachian foreland. The dome has a NNE-SSW axis about 190 km long, and an east-west dimension of about 140 km. It has a structural relief of at least 1600 m, and a local topographic relief of up to 1200 m. First-order leveling in 1955, and again in 1973 along a north-south line at the eastern margin of the Adirondack shows an uplift rate of 2.2 mm/yr at the latitude of the center of the dome and a subsidence rate of 2.8 mm/yr at the northern end of the line near the Canadian border. The net amount of arching along this releveled line is 9 cm ?? 2 cm (Isachsen, 1975). To test the idea that this arching represented an "edge effect" of contemporary doming of the Adirondacks as a whole, the National Geodetic Survey was encouraged to relevel a 1931 north-south line between Utica and Fort Covington (near the Canadian border) which crosses the center of the dome. The releveling showed that the mountain mass is undergoing contemporary domical uplift at a rate which reaches 3.7 mm/yr near the center of the dome (compare with 1 mm/yr for the Swiss Alps). Three other releveled lines in the area support this conclusion. ?? 1981.

  3. Explosive activity associated with the growth of volcanic domes

    USGS Publications Warehouse

    Newhall, C.G.; Melson, W.G.

    1983-01-01

    Domes offer unique opportunities to measure or infer the characteristics of magmas that, at domes and elsewhere, control explosive activity. A review of explosive activity associated with historical dome growth shows that: 1. (1) explosive activity has occurred in close association with nearly all historical dome growth; 2. (2) whole-rock SiO2 content, a crude but widely reported indicator of magma viscosity, shows no systematic relationship to the timing and character of explosions; 3. (3) the average rate of dome growth, a crude indicator of the rate of supply of magma and volatiles to the near-surface enviornment, shows no systematic relationship to the timing or character of explosions; and 4. (4) new studies at Arenal and Mount St. Helens suggest that water content is the dominant control on explosions from water-rich magmas, whereas the crystal content and composition of the interstitial melt (and hence magma viscosity) are equally or more important controls on explosions from water-poor magmas. New efforts should be made to improve current, rather limited techniques for monitoring pre-eruption volatile content and magma viscosity, and thus the explosive potential of magmas. ?? 1983.

  4. Two types of superconducting domes in unconventional superconductors

    NASA Astrophysics Data System (ADS)

    Das, Tanmoy; Panagopoulos, Christos

    In this talk, we present a comprehensive analysis of the SC properties and phase diagrams across several families of unconventional superconductors within the copper-oxides, heavy-fermions, organics, and the recently discovered iron-pnictides, iron-chalcogenides, and oxybismuthides. We find that there are two types of SC domes present in all families of SC materials, arising sometimes as completely isolated, or merged into one, or in some materials only any one of them appears. One of the SC dome appearing at or near a possible QCP usually possesses a lower transition temperature (Tc) . The other SC dome appearing at a different value of the tuning parameter around a non-Fermi liquid (NFL) state often has higher Tc. Both SC domes are not necessarily linked to each other, and so does the QCP and NFL state. In materials, where both domes are present, they can be isolated by multiple tuning (such as such as disorder, or pressure, or magnetic field in addition to doping, and vice versa), giving a unique opportunity to decouple the relationship between QCP, NFL, and their role on superconductivity. The systematic study the NFL state might be a generic route to higher-Tc superconductivity.

  5. Dry Creek salt dome, Mississippi Interior Salt basin

    SciTech Connect

    Montgomery, S.L.; Ericksen, R.L.

    1997-03-01

    Recent drilling of salt dome flanks in the Mississippi Salt basin has resulted in important new discoveries and the opening of a frontier play. This play is focused on gas/condensate reserves in several Cretaceous formations, most notably the Upper Cretaceous Eutaw and lower Tuscaloosa intervals and Lower Cretaceous Paluxy and Hosston formations. As many as eight domes have been drilled thus far; sandstones in the upper Hosston Formation comprise the primary target. Production has been as high as 3-5 Mcf and 500-1200 bbl of condensate per day, with estimated ultimate reserves in the range of 0.2 to 1.5 MBOE (million barrels oil equivalent) per well. As typified by discovery at Dry Creek salt dome, traps are related to faulting, unconformities, and updip loss of permeability. Previous drilling at Dry Creek, and in the basin generally, avoided the flank areas of most domes, due to geologic models that predicted latestage (Tertiary) piercement and breached accumulations. Recent data from Dry Creek and other productive domes suggest that growth was episodic and that piercement of Tertiary strata did not affect deeper reservoirs charged with hydrocarbons in the Late Cretaceous.

  6. Magma Dynamics in Dome-Building Volcanoes

    NASA Astrophysics Data System (ADS)

    Kendrick, J. E.; Lavallée, Y.; Hornby, A. J.; Schaefer, L. N.; Oommen, T.; Di Toro, G.; Hirose, T.

    2014-12-01

    The frequent and, as yet, unpredictable transition from effusive to explosive volcanic behaviour is common to active composite volcanoes, yet our understanding of the processes which control this evolution is poor. The rheology of magma, dictated by its composition, porosity and crystal content, is integral to eruption behaviour and during ascent magma behaves in an increasingly rock-like manner. This behaviour, on short timescales in the upper conduit, provides exceptionally dynamic conditions that favour strain localisation and failure. Seismicity released by this process can be mimicked by damage accumulation that releases acoustic signals on the laboratory scale, showing that the failure of magma is intrinsically strain-rate dependent. This character aids the development of shear zones in the conduit, which commonly fracture seismogenically, producing fault surfaces that control the last hundreds of meters of ascent by frictional slip. High-velocity rotary shear (HVR) experiments demonstrate that at ambient temperatures, gouge behaves according to Byerlee's rule at low slip velocities. At rock-rock interfaces, mechanical work induces comminution of asperities and heating which, if sufficient, may induce melting and formation of pseudotachylyte. The viscosity of the melt, so generated, controls the subsequent lubrication or resistance to slip along the fault plane thanks to non-Newtonian suspension rheology. The bulk composition, mineralogy and glass content of the magma all influence frictional behaviour, which supersedes buoyancy as the controlling factor in magma ascent. In the conduit of dome-building volcanoes, the fracture and slip processes are further complicated: slip-rate along the conduit margin fluctuates. The shear-thinning frictional melt yields a tendency for extremely unstable slip thanks to its pivotal position with regard to the glass transition. This thermo-kinetic transition bestows the viscoelastic melt with the ability to either flow or

  7. Lava dome morphometry and geochronology of the youngest eruptive activity in Eastern Central Europe: Ciomadul (Csomád), East Carpathians, Romania

    NASA Astrophysics Data System (ADS)

    Karátson, D.; Telbisz, T.; Harangi, Sz.; Magyari, E.; Kiss, B.; Dunkl, I.; Veres, D.; Braun, M.

    2012-04-01

    Volcanic evolution of the Ciomadul (Csomád) lava dome complex, site of the youngest (Late Pleistocene, late Marine Isotope Stage 3) eruptive activity in the Carpathians, has been studied by advanced morphometry and radiometric (U/Pb, U/He and 14C) geochronology. The volcano produced alternating effusive and intermittent explosive eruptions from individual domes, typical of common andesitic-dacitic lava domes. A comparative morphometry shows steep ≥30° mean slopes of domes' upper flank and the Csomád domes fit well to the 100-200 ka domes worldwide. Morphometric ages obtained from the mean slope vs age precipitation correlation results in ≤100 ka ages. The morphometric approach is supported by U/Pb and U/He chronology: preliminary results of zircon dating indicate ages ranging between 200(250) and 30 ka. The youngest ages of the data set obtained both from lavas and pumiceous pyroclastics argue for a more or less coeval effusive and explosive volcanism. Based also on volcanological data, we propose vulcanian eruptions and explosive dome collapses especially toward the end of volcanic activity. Moreover, radiometric chronology suggests that, possibly subsequently to the peripheral domes, a central lava dome complex built up ≤100 ka ago. This dome complex, exhibiting even more violent, up to sub-plinian explosions, emplaced pumiceous pyroclastic flow and fall deposits as far as 17 km. We propose that the explosive activity produced caldera-forming eruptions as well, creating a half-caldera. This caldera rim is manifested by the asymmetric morphology of the central edifice: the present-day elevated ridge of Ciomadul Mare (Nagy Csomád), encompassing the twin craters of Mohoş (Mohos) peat bog and Sf. Ana (Szent [St.] Anna). These latter craters may have been formed subsequently, ca. ~100-30 ka ago, after the caldera formation. Drilling of lacustrine sediments in the St. Anna crater shows that beneath the Holocene gyttja several meters of Late Pleistocene

  8. Anomalous zones in Gulf Coast Salt domes with special reference to Big Hill, TX, and Weeks Island, LA

    SciTech Connect

    Neal, J.T.; Magorian, T.R.; Thoms, R.L.; Autin, W.J.; McCulloh, R.P.; Denzler, S.; Byrne, K.O.

    1993-07-01

    Anomalous features in Gulf Coast Salt domes exhibit deviations from normally pure salt and vary widely in form from one dome to the next, ranging considerably in length and width. They have affected both conventional and solution mining in several ways. Gas outbursts, insolubles, and potash (especially carnallite) have led to the breakage of tubing in a number of caverns, and caused irregular shapes of many caverns through preferential leaching. Such anomalous features essentially have limited the lateral extent of conventional mining at several salt mines, and led to accidents and even the closing of several other mines. Such anomalous features, are often aligned in anomalous zones, and appear to be related to diapiric processes of salt dome development. Evidence indicates that anomalous zones are found between salt spines, where the differential salt intrusion accumulates other materials: Anhydrite bands which are relatively strong, and other, weaker impurities. Shear zones and fault displacement detected at Big Hill and Weeks Island domes have not yet had any known adverse impacts on SPR oil storage, but new caverns at these sites conceivably may encounter some potentially adverse conditions. Seismic reflection profiles at Big Hill dome have shown numerous fractures and faults in the caprock, and verified the earlier recognition of a major shear zone transecting the entire salt stock and forming a graben in the overlying caprock. Casing that is placed in such zones can be at risk. Knowledge of these zones should create awareness of possible effects rather than preclude the future emplacement of caverns. To the extent possible, major anomalous zones and salt stock boundaries should be avoided. Shear zones along overhangs may be particularly hazardous, and otherwise unknown valleys in the top of salt may occur along shear zones. These zones often can be mapped geophysically, especially with high-resolution seismic techniques.

  9. Final report on decommissioning of wells, boreholes, and tiltmeter sites, Gulf Coast Interior Salt Domes of Louisiana

    SciTech Connect

    Not Available

    1989-07-01

    In the late 1970s, test holes were drilled in northern Louisiana in the vicinity of Vacherie and Rayburn`s Salt Domes as part of the Department of Energy`s (DOE) National Waste Terminal Storage (NWTS) (rename the Civilian Radioactive Waste Management (CRWM)) program. The purpose of the program was to evaluate the suitability of salt domes for long term storage or disposal of high-level nuclear waste. The Institute for Environmental Studies at Louisiana State University (IES/LSU) and Law Engineering Testing Company (LETCo) of Marietta, Georgia performed the initial field studies. In 1982, DOE awarded a contract to the Earth Technology Corporation (TETC) of Long Beach, California to continue the Gulf Coast Salt Dome studies. In 1986, DOE deferred salt domes from further consideration as repository sites. This report describes test well plugging and site abandonment activities performed by SWEC in accordance with Activity Plan (AP) 1--3, Well Plugging and Site Restoration of Work Sites in Louisiana. The objective of the work outlined in this AP was to return test sites to as near original condition as possible by plugging boreholes, removing equipment, regrading, and seeding. Appendices to this report contain forms required by State of Louisiana, used by SWEC to document decommissioning activities, and pertinent documentation related to lease/access agreements.

  10. An assessment of hydrothermal alteration in the Santiaguito lava dome complex, Guatemala: implications for dome collapse hazards

    USGS Publications Warehouse

    Ball, Jessica L.; Calder, Eliza S.; Hubbard, Bernard E.; Bernstein, Marc L.

    2013-01-01

    A combination of field mapping, geochemistry, and remote sensing methods has been employed to determine the extent of hydrothermal alteration and assess the potential for failure at the Santiaguito lava dome complex, Guatemala. The 90-year-old complex of four lava domes has only experienced relatively small and infrequent dome collapses in the past, which were associated with lava extrusion. However, existing evidence of an active hydrothermal system coupled with intense seasonal precipitation also presents ideal conditions for instability related to weakened clay-rich edifice rocks. Mapping of the Santiaguito dome complex identified structural features related to dome growth dynamics, potential areas of weakness related to erosion, and locations of fumarole fields. X-ray diffraction and backscattered electron images taken with scanning electron microscopy of dacite and ash samples collected from around fumaroles revealed only minor clay films, and little evidence of alteration. Mineral mapping using ASTER and Hyperion satellite images, however, suggest low-temperature (<150 °C) silicic alteration on erosional surfaces of the domes, but not the type of pervasive acid-sulfate alteration implicated in collapses of other altered edifices. To evaluate the possibility of internal alteration, we re-examined existing aqueous geochemical data from dome-fed hot springs. The data indicate significant water–rock interaction, but the Na–Mg–K geoindicator suggests only a short water residence time, and δ18O/δD ratios show only minor shifts from the meteoric water line with little precipitation of secondary (alteration) minerals. Based on available data, hydrothermal alteration on the dome complex appears to be restricted to surficial deposits of hydrous silica, but the study has highlighted, importantly, that the 1902 eruption crater headwall of Santa María does show more advanced argillic alteration. We also cannot rule out the possibility of advanced alteration

  11. Geodesic-dome tank roof cuts water contamination, vapor losses

    SciTech Connect

    Barrett, A.E. )

    1989-07-10

    Colonial Pipeline Co. has established an ongoing program for using geodesic-dome roofs on tanks in liquid petroleum-product service. As its standard, Colonial adopted geodesicodone roofs, in conjunction with internal floating decks, to replace worn external floating roofs on existing tanks used in gasoline service and for use on new tanks in all types of product service. Geodesic domes are clear-span structures requiring no internal-support columns. This feature allows the associated use of a floating deck that is as vapor tight as is possible to construct. Further, geodesic domes can practically eliminate rainwater contamination, eliminate wind-generated vapor losses, and greatly reduce filling losses associated with conventional external floating roofs.

  12. Dome-shaped PDC cutters drill harder rock effectively

    SciTech Connect

    Moran, D.P. )

    1992-12-14

    This paper reports that rock mechanics and sonic travel time log data indicate that bits with convex-shaped polycrystalline diamond compact (PDC) cutters can drill harder rock formations than comparable bits with flat PDC cutters. The Dome-shaped cutters have drilled carbonate formations with sonic travel times as small as 50 [mu]sec/ft, compared to the standard cutoff of 75 [mu]sec/ft for flat PCD cutters. Recent field data from slim hole wells drilled in the Permian basin have shown successful applications of the 3/8-in. Dome cutter in the Grayburg dolomite with its sonic travel times as low as 50-55 [mu]sec/ft and compressive strengths significantly greater than the standard operating range for PDC bit applications. These field data indicate that the Dome cutters can successfully drill hard rock. The convex cutter shape as good impact resistance, cuttings removal, heat dissipation, and wear resistance.

  13. Giant magnetostriction in Tb-doped Fe{sub 83}Ga{sub 17} melt-spun ribbons

    SciTech Connect

    Wu, Wei; Liu, Jinghua; Jiang, Chengbao; Xu, Huibin

    2013-12-23

    Giant magnetostriction is achieved in lightly Tb-doped Fe{sub 83}Ga{sub 17} melt-spun ribbons. The average perpendicular magnetostriction λ{sub ⊥} is −886 ppm along the melt-spun ribbon direction in the Fe{sub 82.89}Ga{sub 16.88}Tb{sub 0.23} alloy and the calculated parallel magnetostriction λ{sub ‖‖} is 1772 ppm. These values are more than four times as large as those found in binary Fe{sub 83}Ga{sub 17}. The enhanced magnetostriction is attributed to a small amount of Tb entering solution in the A2 matrix phase during rapid solidification. The strong localized magnetocrystalline anisotropy of terbium is thought to cause the giant magnetostriction.

  14. New insights on kinematics and deformation within lava domes

    NASA Astrophysics Data System (ADS)

    Buisson, C.

    2003-04-01

    Highly viscous magma extrusions, such as lava domes, constitute a major volcanic risk, essentially because of their cataclysmal disruption occurring during or after emplacement. It is clear that destabilisation process depends mostly on lava domes growth setting and especially internal kinematics and deformation. This particular topic has never been tackled before. Simple scaled experiments have been conducted with a viscous fluid vertically injected from a reservoir into a feeding conduit and flowing on a planar base. Silicone putty is used as analogue magma. On models section, we can determine internal particle paths trough time, velocity gradients, sense of shearing and attitude of the flattening plane. The overall geometry is characterised by a prominent upper cupola located in the centre and corresponding to an injection field versus a gravity one, situated in dome periphery. Spatial distribution between these two zones evolves with time. A dome can be termed mature once the central domain has achieved its definitive shape. Then, dome growth is only expressed by lateral gravity field growth. Displacements are radial in plan and parabolic in section. The highest strain zone is situated above the feeding conduit. In cross-sections, stretch trajectories are remarkably concentric. To the lateral margins, a triple junction of stretch trajectories defines an isotropic point in the strain field. In the main central part of the dome, an intermediate zone of reversed sense of shearing is observed and attributed to velocity gradients variations. We complete analogues models by numerical approach intended to calculate the orientation and shape of the strain ellipsoid in the three dimensions of space. They reveal that the principal stretch, 1, is radial at the base, thus parallel to the flow direction and concentric, thus perpendicular to the flow direction, at the summit. In all the domes, deformation patterns are the results of a combination between pure shear and two

  15. Exploring Learning through Audience Interaction in Virtual Reality Dome Theaters

    NASA Astrophysics Data System (ADS)

    Apostolellis, Panagiotis; Daradoumis, Thanasis

    Informal learning in public spaces like museums, science centers and planetariums is increasingly popular during the last years. Recent advancements in large-scale displays allowed contemporary technology-enhanced museums to get equipped with digital domes, some with real-time capabilities like Virtual Reality systems. By conducting extensive literature review we have come to the conclusion that little to no research has been carried out on the leaning outcomes that the combination of VR and audience interaction can provide in the immersive environments of dome theaters. Thus, we propose that audience collaboration in immersive virtual reality environments presents a promising approach to support effective learning in groups of school aged children.

  16. Prediction of Limit Strains in Limiting Dome Height Formability Test

    NASA Astrophysics Data System (ADS)

    Zadpoor, Amir A.; Sinke, Jos; Benedictus, Rinze

    2007-04-01

    In this paper, the Marciniak-Kunczynski (MK) method is combined with the Storen-Rice analysis in order to improve accuracy of the predicted limit strains in Limiting Dome Height (LDH) test. FEM simulation is carried out by means of a commercial FEM code (ABAQUS) and FEM results are postprocessed by using an improved MK code. It has been shown that while original MK method considerably misspredicts the limit strains, a combination of MK method and Storen-Rice analysis can predict the dome height with a very good accuracy.

  17. Analysis and test of low profile aluminum aerospace tank dome

    NASA Astrophysics Data System (ADS)

    Ahmed, R.; Wilhelm, J. M.

    1993-12-01

    In order to increase the structural performance of cryogenic tanks, the aerospace industry is beginning to employ low-profile bulkheads in new generation launch vehicle designs. This report details the analysis and test of one such dome made from 2219 aluminum. Such domes have two potential failure modes under internal pressure, general tensile failure and hoop compression buckling (in regions near the equator). The test determined the buckling load and ultimate tensile load of the hardware and showed that both compared well with the analysis predictions. This effort was conducted under the auspices of NASA and the General Dynamics Cryogenic Tank Technology Program (CTTP).

  18. Analysis and test of low profile aluminum aerospace tank dome

    NASA Technical Reports Server (NTRS)

    Ahmed, R.; Wilhelm, J. M.

    1993-01-01

    In order to increase the structural performance of cryogenic tanks, the aerospace industry is beginning to employ low-profile bulkheads in new generation launch vehicle designs. This report details the analysis and test of one such dome made from 2219 aluminum. Such domes have two potential failure modes under internal pressure, general tensile failure and hoop compression buckling (in regions near the equator). The test determined the buckling load and ultimate tensile load of the hardware and showed that both compared well with the analysis predictions. This effort was conducted under the auspices of NASA and the General Dynamics Cryogenic Tank Technology Program (CTTP).

  19. Gravitational Collapse of Lava Domes Triggered by Volcanic Fluids

    NASA Astrophysics Data System (ADS)

    Elsworth, D.; Voight, B.; Taron, J.; Thompson, G.; Vinciguerra, S.; Simmons, J.

    2005-12-01

    Excess fluid pressures exert important controls on the stability of lava domes and of the flanks of volcanoes. Migrating overpressures reduce the shear strength of the edifice and may control the timing, morphology, and energetics of failure. Excess pressures may be developed both directly from magma degassing, and indirectly from the interaction of magma with infiltrating rainwater or groundwater. Interior gases influence the strength of the volcanic pile, and hence its stability, in at least two ways. In the fractured and solidified outer carapace high gas contents reduce effective stresses and concomitantly lower shear strength. In the dome interior, magmas which avoid the off-gassing of volatiles exhibit a low and primarily cohesive strength. Signatures of these various processes are evident in the extensive record of collapses which chart the episodic growth and destruction of the lava dome at Soufriere Hills volcano, Montserrat. Mechanisms include (1) interior pressurization by magma degassing, (2) the interaction of rainwater with the hot dome rind, and (3) the segregation of magmas extruded into the dome resulting in a relatively weak and potentially gas overpressured core. The influence of gas overpressures applied interior to a brittle carapace is typified by the response to episodes of cyclic inflation, where collapse may be delayed and may be triggered at inferred pressures below the peak reached in the prior cycle. Similar influences on timing, and in collapse style are present for rainfall-triggered events where deluges beyond a given intensity and duration are required to promote failure, and the style of collapse is influenced by the antecedent conditions of gas pressurization within the lava dome. In all instances, interior gas overpressures or the presence of a segregated plastic core are both viable mechanisms to promote a switch between shallow instability of the dome carapace to deep transaction of the dome core. Such switching to a more

  20. FLAMMABLE GAS DIFFUSION THROUGH SINGLE SHELL TANK (SST) DOMES

    SciTech Connect

    MEACHAM, J.E.

    2003-11-10

    This report quantified potential hydrogen diffusion through Hanford Site Single-Shell tank (SST) domes if the SSTs were hypothetically sealed airtight. Results showed that diffusion would keep headspace flammable gas concentrations below the lower flammability limit in the 241-AX and 241-SX SST. The purpose of this document is to quantify the amount of hydrogen that could diffuse through the domes of the SSTs if they were hypothetically sealed airtight. Diffusion is assumed to be the only mechanism available to reduce flammable gas concentrations. The scope of this report is limited to the 149 SSTs.

  1. Crosslinked Electro-Spun Chitosan Nanofiber Mats with Cd(II) as Template Ions for Adsorption Applications.

    PubMed

    Li, Yan; Xu, Cong; Qiu, Tianbao; Xu, Xiaoyan

    2015-06-01

    The Cd(II) ion imprinting electro-spun crosslinked chitosan nanofiber mats were successfully prepared using Cd(II) as template ions and glutaraldehyde (GA) as crosslinker to investigate the adsorption of Cd(II) and Pb(II) ions in aqueous solutions. The Cd(II) ion imprinting electro-spun crosslinked chitosan nanofiber mats were characterized by the Fourier Transform Infrared Spectrometer (FTIR), Scanning Electron Microscope (SEM), Thermal Gravimetric Analysis (TGA), elemental analysis and solubility tests. The prepared chitosan nanofiber mats exhibited a higher adsorption capacity for both Cd(II) (364.3 mg/g) and Pb(II) (272.0 mg/g) ions. The dynamic study demonstrated that the adsorption process followed the second-order kinetic equation. Langmuir and Freundlich adsorption models were used to analyze the equilibrium isotherm data. The results showed that the Langmuir model was best suitable for predicting the adsorption isotherm of the studied system. The as prepared Cd(II) ion imprinting electro-spun crosslinked chitosan nanofiber mats might be used as an effective adsorbent for Cd(II) and Pb(II) removal from heavy metal wastewater. PMID:26369036

  2. Evidence for Neoarchaean extensional faults in the Vredefort Dome, South Africa.

    NASA Astrophysics Data System (ADS)

    mashabela, sello

    2013-04-01

    The Vredefort Dome is an approximately 80-90 km wide impact structure, situated 120 km southwest of Johannesburg in South Africa. The dome is a preserved centrally uplifted region of an ancient 250-300 km wide multi-ringed crater that formed at 2.02 Ga. The ancient crater underwent 5-10 km of erosion to expose the Vredefort Dome, allowing for unique study of the deeper levels of the impact crater. The Vredefort Dome is composed of a 40 km wide core, bounded by a 20-25 km wide collar. The core is wholly composed of Mesoarchaean basement gneiss (ca. 3.1 Ga), and the collar is made up of mid-amphibolite to lower greenschist facies supracrustal rocks (ca. 3.0-2.2 Ga). Fault development in the collar has largely been attributed to the impact, except for two fault systems. The two exceptions have been described as pre-impact faults, with apparent strike-slip displacements up to 3 km. It is the focus of this study to distinguish pre-impact structures from impact-related structures. Ortho-photographs, satellite images, and field mapping have shown that pre-impact faults were listric in character, and associated with second order accommodation faults. The main fault is associated with a 20 m wide zone of pseudotachylitic breccia. Most of the pseudotachylitic breccia in the dome has been attributed to the impact, so these faults were possibly associated with earlier pseudotachylite generation. Cleavage associated with the listric faults is displaced by impact-related faults, confirming the existence of two deformation events in the dome. The geometry of the listric faults is similar to those observed in the West Wits Line and West Rand goldfields (55 km north of Vredefort Dome), which have been modelled by Manzi et al. (2012, a, b; submitted) using 3D seismic techniques. The authors attribute the development of listric faults (or a rift-like system of faults) to crustal extension that took place during deposition of Klipriviersberg Group lavas and Platberg Group (2709

  3. Mount St. Helens Lava Domes, Then and Now

    NASA Astrophysics Data System (ADS)

    Fink, J.; Anderson, S. W.

    2004-12-01

    When the Mount St. Helens (MSH) lava dome grew from 1980-1986, little was known about how volatiles, vesicularity or crystallinity were distributed in domes, or about overall patterns of growth. Six years of MSH observations, coupled with comparative petrologic, structural, and analog laboratory studies of domes at Soufriere of St. Vincent, Augustine, Redoubt, Merapi, Montserrat, Santiaguito, and elsewhere have provided a much better foundation for evaluating the 2004 eruptive activity. One of the main goals of the earlier studies was to differentiate intrusive processes from those operating when magma ascends near and onto the volcano's surface. Here we use some of our earlier isotopic, petrographic and remote sensing observations of textures and volatiles to speculate about the processes operating in 2004. We earlier linked variations in lava textures to degassing processes operating during ascent and emplacement. MSH lava was extruded in a relatively dense state. When the water content was high enough, hot, ductile lava beneath the quenched outer rind of the dome vesiculated during surface flow, creating a 1 to 2 meter thick scoriaceous carapace. Post-1983 lavas lacked this scoria because the dome had reached a critical size and strength, resulting in lower short-term eruption rates and extensive degassing of lava en route to the surface. Observations of a dense "fin" in October 2004 suggest that this initial dome-building magma experienced thorough degassing as it broke a new path to the crater floor. We also used hydrogen isotope analyses of water in 1980-86 dome samples to infer degassing processes occurring in the source magma chamber and conduit system. Water content and hydrogen isotopic values of dome samples varied according to texture, position on the flow, and repose period prior to eruption. We saw two trends: (1) lava from lobes emplaced after longer repose intervals were deuterium-enriched, and (2) within individual lobes, relatively dry, smooth

  4. Research on the performance of thermal shock and stress with infrared optical domes

    NASA Astrophysics Data System (ADS)

    Gao, Youtang; Qiao, Jianliang; Niu, Jun; Xu, Yuan; Yang, Yi

    2014-09-01

    The development of infrared optical materials is always closely related to the research and exploration of material science. The infrared optical domes bears shock and produces stress when the infrared optical domes mounted on the missile moving at a high speed is shocked by high temperature. According to aerodynamics theory and thermo shock theory, the surge current will be transferred to optical parts through holding up layer and warms the surface of optical parts when infrared optical parts are shocked by high temperature. A compress stress is formed on the hot external surface of optical parts forms and a tension stress is formed on the internal surface or optical parts under the circumstance of the edge of optical parts being fixed. The windows of optical parts become curvature radius of lens with the function of pressure difference which can cause aberration change. The brittle fracture of material will be caused if peak stress is beyond the strength which is permitted for infrared materials. Therefore, limits to design of windows thickness is proposed in this paper.

  5. Shapes of Venusian 'pancake' domes imply episodic emplacement and silicic composition

    NASA Astrophysics Data System (ADS)

    Fink, J. H.; Bridges, N. T.; Grimm, R. E.

    1993-02-01

    The main evidence available for constraining the composition of the large circular 'pancake' domes on Venus is their gross morphology. Laboratory simulations using polyethylene glycol show that the height to diameter (aspect) ratios of domes of a given total volume depend critically on whether their extrusion was continuous or episodic, with more episodes leading to greater cooling and taller domes. Thus without observations of their emplacement, the compositions of Venusian domes cannot be uniquely constrained by their morphology. However, by considering a population of 51 Venusian domes to represent a sampling of many stages during the growth of domes with comparable histories, and by plotting aspect ratio versus total volume, we find that the shapes of the domes are most consistent with episodic emplacement. On Earth this mode of dome growth is found almost exclusively in lavas of dacite to rhyolite composition, strengthening earlier inferences about the presence of evolved magmas on Venus.

  6. LAMELLA DOME FRAMING DETAIL. NOTE CATWALK AT 12 O'CLOCK AND ...

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

    LAMELLA DOME FRAMING DETAIL. NOTE CATWALK AT 12 O'CLOCK AND SUSPENDED PENTAGONAL LIGHT RING GONDOLA. ALSO NOTE COMPRESSION RING AT CROWN OF DOME. - Houston Astrodome, 8400 Kirby Drive, Houston, Harris County, TX

  7. Shapes of Venusian 'pancake' domes imply episodic emplacement and silicic composition

    NASA Technical Reports Server (NTRS)

    Fink, Jonathan H.; Bridges, Nathan T.; Grimm, Robert E.

    1993-01-01

    The main evidence available for constraining the composition of the large circular 'pancake' domes on Venus is their gross morphology. Laboratory simulations using polyethylene glycol show that the height to diameter (aspect) ratios of domes of a given total volume depend critically on whether their extrusion was continuous or episodic, with more episodes leading to greater cooling and taller domes. Thus without observations of their emplacement, the compositions of Venusian domes cannot be uniquely constrained by their morphology. However, by considering a population of 51 Venusian domes to represent a sampling of many stages during the growth of domes with comparable histories, and by plotting aspect ratio versus total volume, we find that the shapes of the domes are most consistent with episodic emplacement. On Earth this mode of dome growth is found almost exclusively in lavas of dacite to rhyolite composition, strengthening earlier inferences about the presence of evolved magmas on Venus.

  8. Tough and catalytically active hybrid biofibers wet-spun from nanochitin hydrogels.

    PubMed

    Das, Paramita; Heuser, Thomas; Wolf, Andrea; Zhu, Baolei; Demco, Dan Eugen; Ifuku, Shinsuke; Walther, Andreas

    2012-12-10

    Sustainable alternatives for high-performance and functional materials based on renewable resources are intensely needed as future alternatives for present-day, fossil-based materials. Nanochitin represents an emerging class of highly crystalline bionanoparticles with high intrinsic mechanical properties and the ability for conjugation into functional materials owing to reactive amine and hydroxyl groups. Herein we demonstrate that hydrogels containing surface-deacetylated chitin nanofibrils of micrometer length and average diameters of 9 nm, as imaged by cryogenic transmission electron microscopy, can be wet-spun into macrofibers via extrusion in a coagulation bath, a simple low energy and large-scale processing route. The resulting biofibers display attractive mechanical properties with a large plastic region of about 12% in strain, in which frictional sliding of nanofibrils allows dissipation of fracture energy and enables a high work-of-fracture of near 10 MJ/m3. We further show how to add functionality to these macrofibers by exploiting the amine functions of the surface chitosan groups to host catalytically active noble metal nanoparticles, furnishing biobased, renewable catalytic hybrids. These inorganic/organic macrofibers can be used repeatedly for fast catalytic reductions of model compounds without loss of activity, rendering the concept of hybridized chitin materials interesting as novel bioderived supports for nanoparticle catalysts. PMID:23102411

  9. Morphology dependent field emission of acid-spun carbon nanotube fibers

    NASA Astrophysics Data System (ADS)

    Fairchild, S. B.; Boeckl, J.; Back, T. C.; Ferguson, J. B.; Koerner, H.; Murray, P. T.; Maruyama, B.; Lange, M. A.; Cahay, M. M.; Behabtu, N.; Young, C. C.; Pasquali, M.; Lockwood, N. P.; Averett, K. L.; Gruen, G.; Tsentalovich, D. E.

    2015-03-01

    Acid spun carbon nanotube (CNT) fibers were investigated for their field emission properties and performance was determined to be dependent on fiber morphology. The fibers were fabricated by wet-spinning of pre-made CNTs. Fiber morphology was controlled by a fabrication method and processing conditions, as well as purity, size, and type of the CNT starting material. The internal fiber structure consisted of CNT fibrils held together by van der Waals forces. Alignment and packing density of the CNTs affects the fiber’s electrical and thermal conductivity. Fibers with similar diameters and differing morphology were compared, and those composed of the most densely packed and well aligned CNTs were the best field emitters as exhibited by a lower turn-on voltage and a larger field enhancement factor. Fibers with higher electrical and thermal conductivity demonstrated higher maximum current before failure and longer lifetimes. A stable emission current at 3 mA was obtained for 10 h at a field strength of <1 V μm-1. This stable high current operation makes these CNT fibers excellent candidates for use as low voltage electron sources for vacuum electronic devices.

  10. Morphology dependent field emission of acid-spun carbon nanotube fibers.

    PubMed

    Fairchild, S B; Boeckl, J; Back, T C; Ferguson, J B; Koerner, H; Murray, P T; Maruyama, B; Lange, M A; Cahay, M M; Behabtu, N; Young, C C; Pasquali, M; Lockwood, N P; Averett, K L; Gruen, G; Tsentalovich, D E

    2015-03-13

    Acid spun carbon nanotube (CNT) fibers were investigated for their field emission properties and performance was determined to be dependent on fiber morphology. The fibers were fabricated by wet-spinning of pre-made CNTs. Fiber morphology was controlled by a fabrication method and processing conditions, as well as purity, size, and type of the CNT starting material. The internal fiber structure consisted of CNT fibrils held together by van der Waals forces. Alignment and packing density of the CNTs affects the fiber's electrical and thermal conductivity. Fibers with similar diameters and differing morphology were compared, and those composed of the most densely packed and well aligned CNTs were the best field emitters as exhibited by a lower turn-on voltage and a larger field enhancement factor. Fibers with higher electrical and thermal conductivity demonstrated higher maximum current before failure and longer lifetimes. A stable emission current at 3 mA was obtained for 10 h at a field strength of <1 V μm(-1). This stable high current operation makes these CNT fibers excellent candidates for use as low voltage electron sources for vacuum electronic devices. PMID:25694166

  11. High performance electrochemical and electrothermal artificial muscles from twist-spun carbon nanotube yarn

    NASA Astrophysics Data System (ADS)

    Lee, Jae Ah; Baughman, Ray H.; Kim, Seon Jeong

    2015-04-01

    High performance torsional and tensile artificial muscles are described, which utilize thermally- or electrochemically-induced volume changes of twist-spun, guest-filled, carbon nanotube (CNT) yarns. These yarns were prepared by incorporating twist in carbon nanotube sheets drawn from spinnable CNT forests. Inserting high twist into the CNT yarn results in yarn coiling, which can dramatically amplify tensile stroke and work capabilities compared with that for the non-coiled twisted yarn. When electrochemically driven in a liquid electrolyte, these artificial muscles can generate a torsional rotation per muscle length that is over 1000 times higher than for previously reported torsional muscles. All-solid-state torsional electrochemical yarn muscles have provided a large torsional muscle stroke (53° per mm of yarn length) and a tensile stroke of up to 1.3% when lifting loads that are ~25 times heavier than can be lifted by the same diameter human skeletal muscle. Over a million torsional and tensile actuation cycles have been demonstrated for thermally powered CNT hybrid yarns muscles filled with paraffin wax, wherein a muscle spins a rotor at an average 11,500 revolutions/minute or delivers 3% tensile contraction at 1200 cycles/minute. At lower actuation rates, these thermally powered muscles provide tensile strokes of over 10%.

  12. Magnetic properties of Pr-Fe-B melt-spun ribbons with high coerecivity

    NASA Astrophysics Data System (ADS)

    Zhou, Dong; Yang, Jinbo; Zhu, Minggang; Han, Jingzhi; Li, Wei; Han, Rui; Wang, Xuchao; Liu, Shunquan; Wang, Changsheng

    2015-11-01

    The hard magnetic materials Pr13.5Fe80.6-xCoxGa0.4B5.5 (x=0, 2, 4, 8 and 15) have been prepared by melt-spinning technique. The melt-spun ribbons with a high coercivity iHc of 23 kOe are achieved without the heat treatments. It is found that Co substitution for Fe can reduce the portion of the amorphous phases and prevent the formation of the metastable phase in the ribbons. The crystalline grain size of the ribbons increases with increase of Co content. The Curie temperature of the magnet increases linearly with Co content x from 568 K for x=2 to 700 K for x=15. The formation of α-Fe is observed using in-situ measurement of the magnetic properties during the heat treatment, indicating that α-Fe phase can precipitate more easily from the ribbons when the crystalline grain size is smaller.

  13. Magnetocaloric Properties Response in High-Speed Melt-Spun La-Ce-Fe-Si Ribbons

    NASA Astrophysics Data System (ADS)

    Hou, Xueling; Han, Ning; Xue, Yun; Lu, Qianqian; Wang, Xiaochen; Phan, Manh-Huong

    2016-06-01

    The structure and magnetocaloric properties of La-Ce-Fe-Si alloys have been studied. The samples were prepared by melt spinning, the surface speed of the Cu wheel being 55 m/s. The as-spun ribbons were subsequently annealed at 1273 K for different times (10 min-1 h) and then quenched to room temperature. When the annealing time was 20 min, on a 1.5-T applied magnetic field, the maximum magnetic entropy change (ΔS M) of the ribbons reached values of 33.8 J/kg K at the Curie temperature of T C ˜ 182 K. When the annealing time was longer than 20 min, the maximum magnetic entropy change (|ΔS M,Max|) tended to decrease while the T C remained almost unchanged. In the annealing process, La/Ce located at grain boundaries was easily oxidized on the ribbon surface. The presence of large grain sizes and La2O3 or LaO were shown to degrade the magnetocaloric properties. On the other hand, the substitution of Ce for La improved the magnetocaloric effect of La-Fe-Si compounds, which is of practical importance for magnetic refrigeration.

  14. Microstructure Formation during Solidification of Melt-Spun Co-Fe-Mn-Si Alloys

    NASA Astrophysics Data System (ADS)

    Zollinger, J.; Adam, O.; Daloz, D.

    2012-01-01

    Cobalt-based alloys ribbons for the fabrication of cored wires require high elongation, e.g. a good metallurgical quality associated with a fine grain structure. The melt-spinning process allows fabricating the 200 μm thick ribbons in a single casting step. However, the properties of such ribbon suffer from the presence of casting defects, leading to early fractures in the material. The present study investigates the microstructure and defect formation in melt-spun Co-6.5Fe-2.6Mn-(0-1.6)Si alloys (in wt.%). These alloys exhibit uncommon intrinsic behaviour and properties such as high nucleation undercoolings (up to 295K in DTA experiments) or reduced solidification interval (10 < T0 < 25 K). It is found that the main defect leading to fracture is micro-shrinkage due to the solutal dendrite growth at low nucleation undercooling. Low silicon additions (0.6 wt.%) are found to reduce the size and the occurrence of shrinkage and increase the elongation, whereas larger silicon additions (1.6 wt.%) are detrimental to the ribbon properties.

  15. Moiré fringe analysis of small precipitates in melt-spun titanium-silicon alloys.

    PubMed

    Chumbley, L S; Fraser, H L

    1990-01-01

    Oxygen-contaminated, melt-spun, binary Ti-Si alloys have been examined by using transmission electron microscopy. The microstructure of alloys in the range of 4 to 10% Si (by weight) are cellular and consist primarily of alpha-Ti and the silicide Ti5Si3. Contained only within the Ti5Si3 regions are small, approximately spherical particles which are less than or equal to 10 nm in diameter. Due to their small size, the crystal structure of these particles could not be determined by using conventional diffraction techniques such as Selected Area or Convergent Beam Diffraction. By conducting a number of tilting experiments and observing the moiré fringe patterns produced when various matrix Ti5Si3 planes were used to image the sample, the crystal structure of the particles and the orientation relationship which exists between them and the matrix were deduced. The unknown particles, termed the Z phase, were found to be hexagonal with slightly different lattice parameters from the matrix Ti5Si3. Their relationship with the matrix was such that they appeared to be totally coherent. This may indicate that Z is an oxide based on the intermetallic Ti5Si3. PMID:2299418

  16. Microstructure and magnetic properties of melt-spun Alnico-5 alloys

    NASA Astrophysics Data System (ADS)

    Löwe, Konrad; Dürrschnabel, Michael; Molina-Luna, Leopoldo; Madugundo, Rajasekhar; Frincu, Bianca; Kleebe, Hans-Joachim; Gutfleisch, Oliver; Hadjipanayis, George C.

    2016-06-01

    The aim of this work is to investigate the effect of very fine grain sizes on the spinodal decomposition in the Alnico system. Commercial Alnico 5 was melted and melt-spun with varying copper wheel speeds, which led to a grain size of 1-2 μm. This value was further reduced to sub-micrometer size by a small addition of Boron (1 at%). The spinodal decomposition was induced through a two-step annealing treatment under magnetic field in the range of 600-900 °C. It was found that the size of the spinodal structures is not influenced much by increased wheel speeds but becomes smaller with the addition of Boron. However, the difference in coercivity between the samples with and without Boron is only 50 Oe (4 kA/m). To study the influence of the annealing treatment two sets of samples are compared, one with the highest coercivity (366 Oe/29 kA/m) and the other one with lower coercivity (180 Oe/14.5 kA/m). We found with Scanning transmission electron microscopy Energy-dispersive X-ray spectroscopy (STEM EDX) a much sharper chemical interface between the α1 and α2 precipitates in the former sample, which we attribute to be the main reason for the higher coercivity.

  17. Physio-chemical and antibacterial characteristics of pressure spun nylon nanofibres embedded with functional silver nanoparticles.

    PubMed

    Xu, Z; Mahalingam, S; Rohn, J L; Ren, G; Edirisinghe, M

    2015-11-01

    A novel and facile approach to prepare hybrid nanoparticle embedded polymer nanofibers using pressurised gyration is presented. Silver nanoparticles and nylon polymer were used in this work. The polymer solution's physical properties, rotating speed and the working pressure had a significant influence on the fibre diameter and the morphology. Fibres in the range of 60-500nm were spun using 10wt.%, 15wt.% and 20wt.% nylon solutions and these bead-free fibres were processed under 0.2MPa and 0.3MPa working pressure and a rotational speed of 36,000rpm. 1-4wt.% of Ag was added to these nylon solutions and in the case of wt.% fibres in the range 50-150nm were prepared using the same conditions of pressurised gyration. Successful incorporation of the Ag nanoparticles in nylon nanofibres was confirmed by using a combination of advanced microscopical techniques and Raman spectrometry was used to study the bonding characteristics of nylon and the Ag nanoparticles. Inductively coupled plasma mass spectroscopy showed a substantial concentration of Ag ions in the nylon fibre matrix which is essential for producing effective antibacterial properties. Antibacterial activity of the Ag-loaded nanofibres shows higher efficacy than nylon nanofibres for Gram-negative Escherichia coli and Pseudomonas aeruginosa microorganisms, and both Ag nanoparticles and the Ag ions were found to be the reason for enhanced cell death in the bacterial solutions. PMID:26249581

  18. Advanced silk material spun by a transgenic silkworm promotes cell proliferation for biomedical application.

    PubMed

    Wang, Feng; Xu, Hanfu; Wang, Yuancheng; Wang, Riyuan; Yuan, Lin; Ding, Huan; Song, Chunnuan; Ma, Sanyuan; Peng, Zhixin; Peng, Zhangchuan; Zhao, Ping; Xia, Qingyou

    2014-12-01

    Natural silk fiber spun by the silkworm Bombyx mori is widely used not only for textile materials, but also for biofunctional materials. In the present study, we genetically engineered an advanced silk material, named hSFSV, using a transgenic silkworm, in which the recombinant human acidic fibroblast growth factor (hFGF1) protein was specifically synthesized in the middle silk gland and secreted into the sericin layer to surround the silk fiber using our previously optimized sericin1 expression system. The content of the recombinant hFGF1 in the hSFSV silk was estimated to be approximate 0.07% of the cocoon shell weight. The mechanical properties of hSFSV raw silk fiber were enhanced slightly compared to those of the wild-type raw silk fiber, probably due to the presence of the recombinant of hFGF1 in the sericin layer. Remarkably, the hSFSV raw silk significantly stimulated the cell growth and proliferation of NIH/3T3 mouse embryonic fibroblast cells, suggesting that the mitogenic activity of recombinant hFGF1 was well maintained and functioned in the sericin layer of hSFSV raw silk. These results show that the genetically engineered raw silk hSFSV could be used directly as a fine biomedical material for mass application. In addition, the strategy whereby functional recombinant proteins are expressed in the sericin layer of silk might be used to create more genetically engineered silks with various biofunctions and applications. PMID:24980060

  19. High-coercivity samarium-iron-nitrogen from nitriding melt-spun ribbons

    SciTech Connect

    Pinkerton, F.E.; Fuerst, C.D. )

    1993-04-01

    Melt spinning has proven to be an excellent technique for magnetic hardening of a variety of permanent magnet materials, especially Nd-Fe-B. Recently, a new permanent magnet material has been discovered by nitriding the compound Sm[sub 2]Fe[sub 17] to obtain Sm[sub 2]Fe[sub 17]N[sub x]. The authors have obtained magnetically hard Sm-Fe-N ribbons with a room-temperature intrinsic coercivity H[sub ci] = 22 kOe (1.8 MA/m) by nitriding melt-spun Sm-Fe precursor ribbons. Best results were obtained by grinding the ribbons to a <25 [mu]m powder, then heat treating the powder in vacuum for 1 h at 700 C prior to nitriding in N[sub 2] gas at 450 to 480 C. X-ray diffraction shows that the primary phase is TbCu[sub 7]-type Sm[sub 2]Fe[sub 17]N[sub x], a disordered hexagonal modification of the rhombohedral Sm[sub 2]Fe[sub 17] phase.

  20. Topaz rhyolites of Nathrop, Colorado: Lava domes or rheomorphic flows?

    NASA Astrophysics Data System (ADS)

    Hernandez, B. M.; Panter, K. S.; Van Der Voo, R.

    2013-12-01

    Deposits of topaz-bearing rhyolite at Ruby and Sugarloaf Mountains in central Colorado are considered to be remnants of lava domes. The deposits are part of the Late Eocene-Oligocene Central Colorado Volcanic Field [1] that lies along the eastern margin of the Arkansas Graben of the Rio Grande Rift. Topaz-bearing rhyolite lava domes and flows have been identified elsewhere in Colorado and the western U.S., but an assortment of geomorphological, lithostratigraphical, and textural features of Ruby and Sugarloaf Mountains call into question their strict classification as such. Alternatively, the lava flows may be interpreted as rheomorphic ignimbrites. The volcanic deposits encompass a sequence of steeply (~70°) west-dipping units that form two N-S elongated edifices ~0.5 km long and a few hundred meters high. Their common lithostratigraphy from bottom to top is tuff breccia, vitrophyre, and flow-banded rhyolite. The tuff breccia includes large (up to ~1 m) pumice blocks and lithics that vary from nearly absent to moderately abundant (10-20%). At Sugarloaf lithics include rare cobble-sized clasts of granite, but the majority consists of flow-banded rhyolite. The tuff breccia grades normally upward into the vitrophyre with increased welding and a eutaxitic fabric defined by fiamme with increasing aspect ratios. Lithics are abundant in the vitrophyre at Sugarloaf but are rare or absent in the vitrophyre at Ruby Mountain. The transition from the vitrophyre to the flow-banded rhyolite is abrupt (<1 m) at both locations, though the lower rhyolite is less competent. The flow-banded rhyolite at Sugarloaf is crystal-rich (up to 50%), containing plagioclase, sanidine, smoky quartz, and biotite, while at Ruby the rhyolite is relatively crystal poor (2-3%) and biotite is absent. Pumiceous zones and lithophysae occur within the rhyolite at both locations. Zones of auto-brecciation are often associated with convoluted flow banding, especially along a vertical contact with

  1. [Analysis of the Basic Stress Pathway Above Acetabular Dome].

    PubMed

    Nie, Yong; Ma, Jun; Haung, Qiang; Hu, Qinsheng; Shi, Xiaojun; Pei, Fuxing

    2015-08-01

    The basic stress pathway above the acetabular dome is important for the maintenance of implant stability in acetabular reconstruction of total hip arthroplasty (THA). The purpose of this study was to describe the basic stress pathway to provide evidence for clinical acetabular reconstruction guidance of THA. A subject-specific finite element (FE) model was developed from CT data to generate 3 normal hip models and a convergence study was conducted to determine the number of pelvic trabecular bone material properties using 5 material assignment plans. In addition, in the range of 0 to 20 mm above the acetabular dome, the models were sectioned and the stress pathway was defined as two parts, i.e., 3D, trabecular bone stress distribution and quantified cortical bone stress level. The results showed that using 100 materials to define the material property of pelvic trabecular bone could assure both the accuracy and efficiency of the FE model. Under the same body weight condition, the 3D trabecular bone stress distributions above the acetabular dome were consistent, and especially the quantified cortical bone stress levels were all above 20 MPa and showed no statistically significant difference (P>0.05). Therefore, defining the basic stress pathway above the acetabular dome under certain body weight condition contributes to design accurate preoperative plan for acetabular reconstruction, thus helping restore the normal hip biomechanics and preserve the stability of the implants. PMID:26710451

  2. Determining the coordinates of lamps in an illumination dome

    NASA Astrophysics Data System (ADS)

    MacDonald, Lindsay W.; Ahmadabadian, Ali H.; Robson, Stuart

    2015-05-01

    The UCL Dome consists of an acrylic hemisphere of nominal diameter 1030 mm, fitted with 64 flash lights, arranged in three tiers of 16, one tier of 12, and one tier of 4 lights at approximately equal intervals. A Nikon D200 digital camera is mounted on a rigid steel frame at the `north pole' of the dome pointing vertically downwards with its optical axis normal to the horizontal baseboard in the `equatorial' plane. It is used to capture sets of images in pixel register for visualisation and surface reconstruction. Three techniques were employed for the geometric calibration of flash light positions in the dome: (1) the shadow cast by a vertical pin onto graph paper; (2) multi-image photogrammetry with retro-reflective targets; and (3) multi-image photogrammetry using the flash lights themselves as targets. The precision of the coordinates obtained by the three techniques was analysed, and it was found that although photogrammetric methods could locate individual targets to an accuracy of 20 μm, the uncertainty of locating the centroids of the flash lights was approximately 1.5 mm. This result was considered satisfactory for the purposes of using the dome for photometric imaging, and in particular for the visualisation of object surfaces by the polynomial texture mapping (PTM) technique.

  3. 19. View of satcom communication dome with TR radome in ...

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

    19. View of satcom communication dome with TR radome in background right. - Clear Air Force Station, Ballistic Missile Early Warning System Site II, One mile west of mile marker 293.5 on Parks Highway, 5 miles southwest of Anderson, Anderson, Denali Borough, AK

  4. 14. PHOTOCOPY OF PHOTOGRAPH: DOMED CEILING OF AUDITORIUM, Date unknown. ...

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

    14. PHOTOCOPY OF PHOTOGRAPH: DOMED CEILING OF AUDITORIUM, Date unknown. from FOURTH CHURCH OF CHRIST, SCIENTIST ARCHIVE (used with permission) E. S. Cheney and R. B. Bird, Photographers, Cheney Photo Adv. Co., Oakland, California. - Fourth Church of Christ, Scientist, 1330 Lakeshore Avenue, Oakland, Alameda County, CA

  5. Power production with two-phase expansion through vapor dome

    SciTech Connect

    Amend, W.E.; Toner, S.J.

    1984-08-07

    In a system wherein a fluid exhibits a regressive vapor dome in a T-S diagram, the following are provided: a two-phase nozzle receiving the fluid in pressurized and heated liquid state and expanding the received liquid into saturated or superheated vapor state, and apparatus receiving the saturated or superheated vapor to convert the kinetic energy thereof into power.

  6. Processing method and process modeling of large aperture transparent magnesium aluminate spinel domes

    NASA Astrophysics Data System (ADS)

    Yu, Jian; McWilliams, Brandon; Kilczewski, Steven; Gilde, Gary; Lidie, Ashley; Sands, James

    2009-05-01

    Polycrystalline spinel serves as an alternative to materials such as sapphire and magnesium fluoride that are currently being used in electromagnetic window applications such as missile domes, where high strength, high hardness and high transmittance in the visible and infrared spectra are required. The cubic crystal lattice of spinel imparts an isotropy to the bulk optical property, which eliminates optical distortion due to birefringence that occurs in sapphire and other non-cubic materials. The current study is to find a reliable manufacturing process to produce large magnesium aluminate spinel domes from powder consolidation efficiently. A binder-less dry ball milling process was used to deflocculate the spinel powder to increase its fluidity in an effort to ease the shape-forming. Dry ball milling time trials were conducted at several intervals to determine the appropriate level of time required to break up both the hard and soft agglomerates associated with the virgin spinel powder. The common problems encountered in dry powder shape-forming are crack growth and delamination of the green body during cold isostatic pressing (CIPing). The cracking and the delamination are due to the buildup of stress gradients on the green body that are created by the frictional force between the powder and the die wall or mold wall. To understand the stresses during the CIPing process, a finite element analysis of stresses on the green body was conducted. The simulation was used to evaluate the effect of die tooling and process characteristics on the development of stress gradients in the green body dome. Additionally, the effect of friction between the die wall and powder was examined by the simulation. It was found that by mitigating the frictional forces, cracking and delamination on the green body could be eliminated. A stepped-pressure CIPing technique was developed to reduce stress gradient build-up during CIPing. Also, oleic acid lubricant was applied to the die wall to

  7. Dome collapse eruption in Tatun Volcanic Group near metropolitan Taipei, Taiwan at ~6 kyrs

    NASA Astrophysics Data System (ADS)

    Chen, C.; Lee, T.

    2010-12-01

    The Tatun Volcanic Group (TVG) is located in the north of metropolitan Taipei, Taiwan. Over 6 million inhabitants are living in Taipei City and suburban area. Another critical issue is an international airport and two nuclear power plants are lying at the foot of the TVG. If the TGV will be re-active, the serious hazard for human lives and economies in this area will definitely occur. Understanding the youngest eruption history of the TVG will be much important for prediction the future activity of eruption. The core was collected from the Dream Lake at the eastern slop of Cising Mt.. Total 21 samples from depth 190 cm to 231.5 cm have been tested. Comparison of chemical compositions of glass and minerals in the volcanic clasts with those of lava around TVG, they clearly showed that the volcanic clasts can be correlated with the eruption of the closest Cising Mt. According to the radiocarbon (C-14) age of core sample at the depth 225 cm, the age was extrapolated around 6150 yrs ca. C-14 B.P.. Moreover, the respiratory cristobalite in the volcanic clasts were firstly identified by the identical morphology, chemical composition and Laser Raman Spectrometry (LRS). The crystalline silica was produced by vapor-phase crystallization and devitrification in the andesite lava dome and volcanic ash generated by pyroclastic flows formed by lava dome collapse in Soufriere Hills volcano, Montserrat (Baxter et al.,1999). These new evidence demonstrated that there would probably have the lava dome collapse eruptions in the TVG in the last 6 kyrs. The result in this paper also sustained that the landslide caused by the weak phreatic eruption within the last 6000 yrs in the TVG (Belousov et al., 2010). It must further be noted that an efficient program of the volcanic hazard reduction should be practiced for the metropolitan Taipei and suburban area.

  8. Using Horizontal Cosmic Muons to Investigate the Density Distribution of the Popocatepetl Volcano Lava Dome

    NASA Astrophysics Data System (ADS)

    Grabski, V.; Lemus, V.; Nuñez-Cadena, R.; Aguilar, S.; Menchaca-Rocha, A.; Fucugauchi, J. U.

    2013-05-01

    Study of volcanic inner density distributions using cosmic muons is an innovative method, which is still in stage of development[1]. The method can be used to determine the average density along the muon track, as well as the density distribution of any volume by measuring the attenuation of cosmic muon flux in it[2]. In this study we present an analysis of using the muon radiography, integrating geophysical data to determine the density distribution of the Popocatepetl volcano. Popocatepelt is a large andesitic stratovolcano built in the Trans-Mexican volcanic arc, which has been active over the past years. The recent activity includes emplacement of a lava dome, with vulcanian explosions and frequent scoria and ash emissions. The study is directed to detect any variations in the dome and magmatic conduit system in some interval of time in the volume of Popocatepetl volcano lava dome. The study forms part of a long-term project of volcanic hazard monitoring that includes the Popocatepetl and Colima volcanoes[3]. The volcanoes are being studied by conventional geophysical techniques, including aerogeophysical surveys directed to determine the internal structure and characterize source characteristics and mechanism. The detector design mostly depends on the volume size to be investigated as well as the image-taking frequency to detect dynamic density variations. In this study we present a detector prototype design and suggestions on data taking, transferring and analyzing systems. We also present the approximate cost estimation of the suggested detector and discussion on a proposal about the creation of a national network for a volcanic alarm system. References [1] eg.H. Tanaka, et al., Nucl. Instr. and Meth. A 507 (2003) 657. [2] V. Grabski et al, NIM A 585 (2008) 128-135. [3] G. Conte, J. Urrutia-Fucugauchi, et al., International Geology Review, Vol. 46, 2004, p. 210-225.

  9. Concentration and isotope ratio of sulfur species in snow along the route to Dome Fuji, Antarctica

    NASA Astrophysics Data System (ADS)

    Hirabayashi, M.; Motoyama, H.

    2014-12-01

    Snow ice sample in Antarctica contains particulate matter. Particulates originate from continent, volcano, sea, space, and organism. Methanesulfonate ion and sulfate ion are major sulfur compounds packed in snow ice in Antarctica. The isotopic ratio of an element reflects the origin and the history of the particle matter. Since the isotopic ratio of sulfur species depends on the source, the information about the source contribution of particulate matter can be estimated by analyzing the isotopic ratios of sulfur species. In this research, concentrations of sulfur species and isotopic ratios of sulfur species in snow collected on the route form coastal area to Dome Fuji station in Antarctica were analyzed. The snow samples were collected along ca. 1000 km traverse route from Mikaeridai (S16; 69°01'S, 40°03'E, 590 m) to Dome Fuji station (77°19'S, 39°42'E, 3810 m) by the Japan Antarctica research expedition. The snow samples were also collected from a pit dug at Dome Fuji station. Those samples were collected in the 2009/2010 austral summer. The samples were transported to Japan without thawing. Quantitative analyses of sulfur species were performed using ion chromatograph and quadrupole type mass spectrometer. The isotopic ratios of isolated sulfur species were measured using elemental analyzer and the magnetic field type mass spectrometer. Average concentrations and maximum concentration of methanesulfonate ion in the snow samples were 17 ng/ml and 123 ng/ml, respectively. Average concentrations and maximum concentration of sulfate ion were ng/ml 63 and 419 ng/ml, respectively. Further results and discussion about the behavior and origin of sulfur species in the snow will be presented.

  10. Late Pleistocene zircon ages for intracaldera domes at Gölcük (Isparta, Turkey)

    NASA Astrophysics Data System (ADS)

    Schmitt, Axel K.; Danišík, Martin; Siebel, Wolfgang; Elitok, Ömer; Chang, Yu-Wei; Shen, Chuan-Chou

    2014-10-01

    Pleistocene to Quaternary volcanism in the Isparta region (SW Anatolia, Turkey) comprises potassic lavas and pyroclastic deposits, which are largely centered around Gölcük caldera. Trachytic intracaldera lava domes represent the latest eruptive event at Gölcük, and their eruption age is crucial for defining a minimum age for the preceding caldera-forming explosive eruption. Here, we present combined U-Th and (U-Th)/He zircon geochronological data for two intracaldera lava domes constraining their crystallization and eruption ages, respectively. U-Th zircon crystallization ages peak between ca. 15 and 25 ka. In rare instances U-Th zircon crystallization ages date back to ca. 59 and 136 ka. U-Th zircon crystallization ages also permit (U-Th)/He eruption ages from the same crystals to be individually corrected for uranium series decay chain disequilibrium, which is mainly due to the deficit of the intermediate daughter 230Th in zircon. Average disequilibrium-corrected (U-Th)/He zircon ages are 14.1 ± 0.5 and 12.9 ± 0.4 ka (1σ). These ages are indistinguishable within analytical uncertainties suggesting that both lavas erupted quasi simultaneously. This contradicts published K-Ar ages that suggest an extended hiatus from ca. 52 to 24 ka between intracaldera dome eruptions. Evidence for protracted zircon crystallization over several thousands of years prior to eruption indicates the presence of a long-lived magma reservoir underneath Gölcük caldera. Implications of the revised eruptive geochronology presented here include younger ages for the latest effusive eruptions at Gölcük, and potentially also a more recent explosive eruption than previously assumed.

  11. Cooling History in Mabja Dome, Southern Tibet: Implications for the Tectonic Evolution of the North Himalayan Gneiss Domes

    NASA Astrophysics Data System (ADS)

    Lee, J.; Wang, Y.; McWilliams, M.; Hourigan, J.; Blythe, A.; McClelland, W.

    2001-12-01

    The Mabja Dome (MD), southern Tibet, is one of a series of gneiss domes, called the North Himalayan Gneiss Domes, located south of the Indus-Tsangpo suture zone and north of the high Himalaya. The MD consists of an ~25 km diameter doubly plunging antiform cored by migmatitic K-feldspar augen biotite orthogneiss which is mantled by high grade metapelites and granitic orthogneisses. These rocks record two primary deformational events: an older deformational event, D1, characterized by ~EW-trending folds of S0 with an associated moderately N-dipping axial planar foliation, S1, and a younger event, D2, characterized by a domed mylonitic foliation, S2, and associated NS-trending mineral stretching lineation. Peak metamorphism is pre- to early syntectonic with D2 structures and defines a set of isograds that are subparallel to structure. Two-mica granites, one of which yielded an U/Pb monazite age of 14.5+/-0.1 Ma, were emplaced during the latest stages of D2 deformation. Mica and kspar Ar/Ar and apatite fission track (AFT) analyses were completed on orthogneisses, metasediments, and two-mica granites to shed light on the timing and mechanism of cooling of these rocks. Muscovite yielded Ar/Ar cooling ages of ~12.7 Ma on the northern flank of the dome, increasing to ~17.0 Ma in metapelite and orthogneiss at deeper structural levels, and decreasing to ~13.5 Ma within migmatite at the deepest structural levels. Biotites are disturbed and yield total gas ages that are slightly younger than muscovite on the flanks of the dome, but older within the core. Analyses of four kspars from orthogneiss and migmatite yielded complex spectra with old apparent ages at the lowest temperature steps, followed by ages that climb slowly from 12.5-13.0 Ma over the first 30% of 39Ar released, which in turn is followed by ages that climb to 100 Ma (orthogneiss) and 15-18 Ma (migmatite) at high temperature steps. AFT analyses from orthogneiss and migmatite yielded a mean age of 9.5 Ma indicating

  12. Probing permeability and microstructure: Unravelling the role of a low-permeability dome on the explosivity of Merapi (Indonesia)

    NASA Astrophysics Data System (ADS)

    Kushnir, Alexandra R. L.; Martel, Caroline; Bourdier, Jean-Louis; Heap, Michael J.; Reuschlé, Thierry; Erdmann, Saskia; Komorowski, Jean-Christophe; Cholik, Noer

    2016-04-01

    Low permeability dome rocks may contribute to conduit overpressure development in volcanic systems, indirectly abetting explosive activity. The permeability of dome-forming rocks is primarily controlled by the volume, type (vesicles and/or microcracks), and connectivity of the void space present. Here we investigate the permeability-porosity relationship of dome-forming rocks and pumice clasts from Merapi's 1888 to 2013 eruptions and assess their possible role in eruptive processes, with particular emphasis on the 2010 paroxysmal eruption. Rocks are divided into three simple field classifications common to all eruptions: Type 1 samples have low bulk density and are pumiceous in texture; Type 2 samples, ubiquitous to the 2010 eruption, are dark grey to black in hand sample and vary greatly in vesicularity; and Type 3 samples are weakly vesicular, light grey in hand sample, and are the only samples that contain cristobalite. Type 2 and Type 3 rocks are present in all eruptions and their permeability and porosity data define similar power law relationships, whereas data for Type 1 samples are clearly discontinuous from these trends. A compilation of permeability and porosity data for andesites and basaltic andesites with published values highlights two microstructural transitions that exert control on permeability, confirmed by modified Bayesian Information Criterion (BIC) analysis. Permeability is microcrack- and diktytaxitic-controlled at connected porosities, φc, < 10.5 vol.%; vesicle- and microcrack-controlled at 10.5 < φc < 31 vol.%; and likely vesicle-controlled for φc > 31 vol.%. Type 3 basaltic andesites, the least permeable of the measured samples and therefore the most likely to have originated in the uppermost low-permeability dome, are identified as relicts of terminal domes (the last dome extruded prior to quiescence). Cristobalite commonly found in the voids of Type 3 blocks may not contribute significantly to the reduction of the permeability of

  13. Heterogeneous nucleation of entrained eutectic Si in high purity melt spun Al-Si alloys investigated by entrained droplet technique and DSC

    NASA Astrophysics Data System (ADS)

    Li, J. H.; Albu, M.; Ludwig, T. H.; Hofer, F.; Arnberg, L.; Schumacher, P.

    2016-03-01

    Entrained droplet technique and DSC analyses were employed to investigate the influence of trace elements of Sr, Eu and P on the heterogeneous nucleation of entrained eutectic Si in high purity melt spun Al-5wt.% Si alloys. Sr and Eu addition was found to exert negative effects on the nucleation process, while an increased undercooling was observed. This can be attributed to the formation of phosphide compounds having a lower free energy and hence may preferentially form compared to AlP. Only a trace P addition was found to have a profound effect on the nucleation process. The nucleation kinetics is discussed on the basis of the classical nucleation theory and the free growth model, respectively. The estimated AlP patch size was found to be sufficient for the free growth of Si to occur within the droplets, which strongly indicates that the nucleation of Si on an AlP patch or AlP particle is a limiting step for free growth. The maximum nucleation site density within one droplet is directly related to the size distribution of AlP particles or AlP patches for Si nucleation, but is independent of the cooling rates. Although the nucleation conditions were optimized in entrained droplet experiments, the observed mechanisms are also valid at moderate cooling conditions, such as in shape casting.

  14. Foldable Thermoelectric Materials: Improvement of the Thermoelectric Performance of Directly Spun CNT Webs by Individual Control of Electrical and Thermal Conductivity.

    PubMed

    An, Cheng Jin; Kang, Young Hun; Lee, A-Young; Jang, Kwang-Suk; Jeong, Youngjin; Cho, Song Yun

    2016-08-31

    We suggest the fabrication of foldable thermoelectric (TE) materials by embedding conducting polymers into Au-doped CNT webs. The CNT bundles, which are interconnected by a direct spinning method to form 3D networks without interfacial contact resistance, provide both high electrical conductivity and high carrier mobility. The ZT value of the spun CNT web is significantly enhanced through two simple processes. Decorating the porous CNT webs with Au nanoparticles increases the electrical conductivity, resulting in an optimal ZT of 0.163, which represents a more than 2-fold improvement compared to the ZT of pristine CNT webs (0.079). After decoration, polyaniline (PANI) is integrated into the Au-doped CNT webs both to improve the Seebeck coefficient by an energy-filtering effect and to decrease the thermal conductivity by the phonon-scattering effect. This leads to a ZT of 0.203, which is one of the highest ZT values reported for organic TE materials. Moreover, Au-doped CNT/PANI web is ultralightweight, free-standing, thermally stable, and mechanically robust, which makes it a viable candidate for a hybrid TE conversion device for wearable electronics. When a 20 K temperature gradient is applied to the TE module consisting of seven p-n couples, 1.74 μW of power is generated. PMID:27501827

  15. Debris avalanches and slumps on the margins of volcanic domes on Venus: Characteristics of deposits

    NASA Technical Reports Server (NTRS)

    Bulmer, M. H.; Guest, J. E.; Beretan, K.; Michaels, Gregory A.; Saunders, R. Stephen

    1992-01-01

    Modified volcanic domes, referred to as collapsed margin domes, have diameters greater than those of terrestrial domes and were therefore thought to have no suitable terrestrial analogue. Comparison of the collapsed debris using the Magellan SAR images with volcanic debris avalanches on Earth has revealed morphological similarities. Some volcanic features identified on the seafloor from sonar images have diameters similar to those on Venus and also display scalloped margins, indicating modification by collapse. Examination of the SAR images of collapsed dome features reveals a number of distinct morphologies to the collapsed masses. Ten examples of collapsed margin domes displaying a range of differing morphologies and collapsed masses have been selected and examined.

  16. Microstructure and microhardness evolution of melt-spun Al-Si-Cu alloy

    NASA Astrophysics Data System (ADS)

    Ahmed, Emad M.; Ebrahim, M. R.

    2014-04-01

    Al-11 wt.% Si-11 wt.% Cu (11.29 at.% Si-5.1 at.% Cu) melt was rapidly solidified into ribbons and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and microhardness technique. The Rietveld X-ray diffraction analysis was applied successfully to analyze the microstructure and phase precipitations. The high cooling rate obtained in rapid solidification has a significant influence on the microstructure and microhardness of this alloy. On the basis of the Al peaks shift measured in the XRD scans, a solid solubility extension value of 3.95 at.% Si and 3.54 at.% Cu in α-Al were determined. No XRD peaks of the Si phase have been detected. XRD peaks of the intermetallic Al2Cu phase have been observed clearly with estimated content of 12.6 wt.%. During prolonged annealing process at 350°C/25 h, XRD peaks of the Si phase clearly appeared with estimated content of 8.6 wt.% and, moreover, the Al2Cu phase content increased to 16 wt.%. The estimated crystallite size and micro-strain % of α-Al are 30 nm and 0.056, respectively. The melt-spun wheel side ribbon represents ultra-fine microstructure with particles size less than 1μm and exhibits enhancement of hardness to 241 HV. Hardness has further increased to 291 HV during heat treatment (150°C/12 h). Rapid solidification exhibited a great influence on microstructure and microhardness of the Al-Si-Cu alloy.

  17. Site testing for submillimetre astronomy at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Tremblin, P.; Minier, V.; Schneider, N.; Durand, G. Al.; Ashley, M. C. B.; Lawrence, J. S.; Luong-van, D. M.; Storey, J. W. V.; Durand, G. An.; Reinert, Y.; Veyssiere, C.; Walter, C.; Ade, P.; Calisse, P. G.; Challita, Z.; Fossat, E.; Sabbatini, L.; Pellegrini, A.; Ricaud, P.; Urban, J.

    2011-11-01

    Aims: Over the past few years a major effort has been put into the exploration of potential sites for the deployment of submillimetre astronomical facilities. Amongst the most important sites are Dome C and Dome A on the Antarctic Plateau, and the Chajnantor area in Chile. In this context, we report on measurements of the sky opacity at 200 μm over a period of three years at the French-Italian station, Concordia, at Dome C, Antarctica. We also present some solutions to the challenges of operating in the harsh polar environment. Methods: The 200-μm atmospheric opacity was measured with a tipper. The forward atmospheric model MOLIERE (Microwave Observation LIne Estimation and REtrieval) was used to calculate the atmospheric transmission and to evaluate the precipitable water vapour content (PWV) from the observed sky opacity. These results have been compared with satellite measurements from the Infrared Atmospheric Sounding Interferometer (IASI) on Metop-A, with balloon humidity sondes and with results obtained by a ground-based microwave radiometer (HAMSTRAD). In addition, a series of experiments has been designed to study frost formation on surfaces, and the temporal and spatial evolution of thermal gradients in the low atmosphere. Results: Dome C offers exceptional conditions in terms of absolute atmospheric transmission and stability for submillimetre astronomy. Over the austral winter the PWV exhibits long periods during which it is stable and at a very low level (0.1 to 0.3 mm). Higher values (0.2 to 0.8 mm) of PWV are observed during the short summer period. Based on observations over three years, a transmission of around 50% at 350 μm is achieved for 75% of the time. The 200-μm window opens with a typical transmission of 10% to 15% for 25% of the time. Conclusions: Dome C is one of the best accessible sites on Earth for submillimetre astronomy. Observations at 350 or 450 μm are possible all year round, and the 200-μm window opens long enough and with a

  18. Timescales of texture development in a cooling lava dome

    NASA Astrophysics Data System (ADS)

    von Aulock, F. W.; Nichols, A. R. L.; Kennedy, B. M.; Oze, C.

    2013-08-01

    Crystal growth and crack development in cooling lava domes are both capable of redistributing and mobilizing water. Cracking and hydration decrease the stability of a dome, which may lead to hazards including partial dome collapse and block and ash flows. By examining the distribution of water around crystals and cracks, we identify and confine temperature and timescales of texture development in glassy rocks of volcanic domes. Four generations of textures have been identified: type a: spherulites, type b: cracks associated with spherulite growth, type c: perlitic cracks, and type d: disparate cracks. High-resolution imaging using Fourier Transform Infrared Spectroscopy (FTIR) performed on samples from the Ngongotaha dome, New Zealand, show an increase in H2O of up to 450% along gradients of around 100 μm up to 300 μm in length from perlitic cracks, spherulitic cracks and in haloes around spherulites. No gradients in water concentrations across the disparate cracks are present. Water diffusion models show potential timescale-temperature couples that coincide with textural observations and previous studies, and allow us to develop a conceptual model of spherulite growth and cracking in a cooling lava dome. Spherulite growth starts around the glass transition temperature (Tg) when the viscous melt cools to a brittle solid and proceeds with cracking related to volume changes at slightly lower temperatures and shorter timescales (days to weeks) compared to spherulite growth. Perlitic cracking happens at T≪Tg, allowing hydration of a permeable network within weeks to months. Low temperature (≲50 °C) cracks could not be hydrated in the time since eruption (≃230 ka). Our data show that textures in cooling glass develop during cooling below Tg within days, producing cracks and crystals that create inhomogeneities in the spatial distribution of water. The lengthscales of water diffusion away from spherulites, spherulite cracks, and perlite cracks suggest that most

  19. Inter-eruptive volcanism at Usu volcano: Micro-earthquakes and dome subsidence

    NASA Astrophysics Data System (ADS)

    Aoyama, H.; Onizawa, S.; Kobayashi, T.; Tameguri, T.; Hashimoto, T.; Oshima, H.; Mori, H.

    2009-12-01

    Post-eruptive crustal activity after the 2000 eruption of Usu volcano was investigated by seismic and geodetic field observations. Remarkable features of the magmatic eruptions that occur almost every 30 years include lava dome formation and strong precursory earthquakes. On the other hand, rapid dome subsidence was observed by electronic distance meter (EDM) measurement after the 1977-1982 summit eruption. Since the 2000 eruption, seismic activity at a shallow part under the summit crater has remained at a high level relative to that after the 1977-1982 eruption, although eruption occurred at the western foot of the volcano during the 2000 eruption. To reveal the shallow crustal activity in the inter-eruptive period around the summit area, seismicity and crustal deformation have been investigated since 2006. Dense temporary seismic observations and hypocenter relocation analysis using a three-dimensional velocity structure model revealed that the focal area is localized along the U-shaped fault that developed in the dome-forming stage of the 1977-1982 eruption. Three major focal clusters are distributed on the southwestern side of Usu-Shinzan cryptodome, which was built up during the 1977-1982 eruption. For the seven major events with magnitudes larger than 1, the focal mechanism was a large dip-slip component, which suggests the subsidence of Usu-Shinzan cryptodome. Interferomatetric satellite aperture radar (InSAR) image analysis and repeated GPS measurements revealed subsidence of the summit dome, which is almost centered at the Usu-Shinzan cryptodome. The area of rapid deformation is restricted to a small area around the summit crater. The estimated rate of dome subsidence relative to the crater floor is about 3 cm/year. These results strongly suggest that subsidence of Usu-Shinzan is associated with the small earthquakes along the U-shaped fault that surrounds the cryptodome. According to prior seismic and geodetic studies, it is thought that most of the

  20. Inter-eruptive volcanism at Usu volcano: Micro-earthquakes and dome subsidence

    NASA Astrophysics Data System (ADS)

    Aoyama, Hiroshi; Onizawa, Shin'ya; Kobayashi, Tomokadu; Tameguri, Takeshi; Hashimoto, Takeshi; Oshima, Hiromitsu; Mori, Hitoshi Y.

    2009-11-01

    Post-eruptive crustal activity after the 2000 eruption of Usu volcano was investigated by seismic and geodetic field observations. Remarkable features of the magmatic eruptions that occur almost every 30 years include lava dome formation and strong precursory earthquakes. On the other hand, rapid dome subsidence was observed by electronic distance meter (EDM) measurement after the 1977-1982 summit eruption. Since the 2000 eruption, seismic activity at a shallow part under the summit crater has remained at a high level relative to that after the 1977-1982 eruption, although eruption occurred at the western foot of the volcano during the 2000 eruption. To reveal the shallow crustal activity in the inter-eruptive period around the summit area, seismicity and crustal deformation have been investigated since 2006. Dense temporary seismic observations and hypocenter relocation analysis using a three-dimensional velocity structure model revealed that the focal area is localized along the U-shaped fault that developed in the dome-forming stage of the 1977-1982 eruption. Three major focal clusters are distributed on the southwestern side of Usu-Shinzan cryptodome, which was built up during the 1977-1982 eruption. For the seven major events with magnitudes larger than 1, the focal mechanism was a large dip-slip component, which suggests the subsidence of Usu-Shinzan cryptodome. Interferomatetric satellite aperture radar (InSAR) image analysis and repeated GPS measurements revealed subsidence of the summit dome, which is almost centered at the Usu-Shinzan cryptodome. The area of rapid deformation is restricted to a small area around the summit crater. The estimated rate of dome subsidence relative to the crater floor is about 3 cm/year. These results strongly suggest that subsidence of Usu-Shinzan is associated with the small earthquakes along the U-shaped fault that surrounds the cryptodome. According to prior seismic and geodetic studies, it is thought that most of the

  1. Geological evaluation of Gulf Coast salt domes: overall assessment of the Gulf Interior Region

    SciTech Connect

    1981-10-01

    The three major phases in site characterization and selection are regional studies, area studies, and location studies. This report characterizes regional geologic aspects of the Gulf Coast salt dome basins. It includes general information from published sources on the regional geology; the tectonic, domal, and hydrologic stability; and a brief description the salt domes to be investigated. After a screening exercise, eight domes were chosen for further characterization: Keechi, Oakwood, and Palestine Domes in Texas; Vacherie and Rayburn's domes in North Louisiana; and Cypress Creek and Richton domes in Mississippi. A general description of each, maps of the location, property ownership, and surface geology, and a geologic cross section were presented for each dome.

  2. Granitoid magmatism of Alarmaut granite-metamorphic dome, West Chukotka, NE Russia

    NASA Astrophysics Data System (ADS)

    Luchitskaya, M. V.; Sokolov, S. D.; Bondarenko, G. E.; Katkov, S. M.

    2009-04-01

    Main tectonic elements of West Chukotka are Alazey-Oloy, South-Anyui and Anyui-Chukotka fold systems, formed as a result of collision between structures of North-Asian continent active margin and Chukotka microcontinent [1-3]. South-Anyui fold system, separating Alazey-Oloy and Anyui-Chukotka systems, is considered as suture zon, formed as a result of oceanic basin closing [4-6]. Continent-microcontinent collision resulted in formation of large orogen with of northern and southern vergent structures, complicated by strike-slip deformations [7, 8]. Within Anyui-Chukotka fold system several rises, where most ancient deposits (crystalline basement and Paleozoic cover of Chukotka microcontinent) are exposed, were distinguished [2, 9-11]. Later they were considered as granite-metamorphic domes [12-14]. Alarmaut dome is located at West Chukotka to the north from Bilibino city and is traced from south to north in more than 120 km. General direction of structure is discordant to prevailing NW extensions of tectonic elements of the region. Paleozoic-Triassic deposits are exposed within the Alarmaut dome: 1) D3-C1 - crystalline schists, quartz-feldspar metasandstones, quartzites, marbles (700 m) [11]; 2) C1 - marblized limestones, quartz-feldspar metasandstones, quartzites, amphibole-pyroxene crystalline schists. Limestones contain corals, indicating Visean age of deposits [11]. Metamorphism reaches amphibolite facies, maximum P-T conditions are 660°С and 5 kbar. Migmatites, indicating in situ partial melting, are observed. Intensity of deformations of Paleozoic rocks increases at the boundary with Triassic deposits [11]; in the western part of dome slices of Pz rocks are separated by blastomylonite horizons [14]. Within Alramaut dome granitoids of Lupveem batholith (central part of dome), Bystrinsky pluton (southeastern part), and small Koyvel' and Kelil'vun plutons were studied. New U-Pb SHRIMP zircon data indicate Early Cretaceous (117-112 m.a.) age of granitoids [15

  3. Miocene calc-alkaline magmatism, calderas, and crustal extension in the Kofa and Castle Dome Mountains, southwestern Arizona

    SciTech Connect

    Grubensky, M.J. ); Bagby, W.C. )

    1990-11-10

    Two widespread lower Miocene rhyolite ash flow tuffs in the Kofa and Castle Dome Mountains of southwestern Arizona are products of caldera-forming eruptions. These closely erupted tuffs, the tuff of Yaqui Tanks and the tuff of Ten Ewe Mountain, are approximately 22 Ma in age and their eruptions culminate a 1- to 2-m.y.-long burst of calc-alkaline volcanic activity centered on the northern Castle Dome Mountains. Exotic blocks of Proterozoic and Mesozoic crystalline rocks up to 20 m across are present in exposures of the tuff of Yaqui Tanks exposed in the central Castle Dome Mountains and the southern Kofa Mountains. A single, thick cooling unit of the tuff of Ten Ewe Mountain that includes thick lenses of mesobreccia marks the location of the younger caldera that extends from Palm Canyon in the western Kofa Mountains eastward more than 7 km along strike to the central part of the range. Large residual Bouguer gravity anomalies, one beneath each inferred caldera, are interpreted as batholithic rocks or low-density caldera fill. Caldera-related volcanism in the Kofa region occurred during a transition in extensional tectonic regimes: From a regime of east-west trending uplifts and basins to a regime manifest primarily by northwest striking normal faults. A narrow corridor of folding and strike-slip faulting formed during volcanism in the southern Kofa Mountains. Upper Oligocene or lower Miocene coarse sedimentary rocks along the southern flank of the Chocolate Mountains anticlinorium in the southern Castle Dome Mountains mark the periphery of a basin similar to other early and middle Tertiary basins exposed in southern California. The volcanic section of the Kofa region was dissected by high-angle normal faults related to northeast-southwest oriented crustal extension typical of the southern Basin and Range province.

  4. Advanced imaging techniques III: a scalable and modular dome illumination system for scientific microphotography on a budget

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A scalable and modular LED illumination dome for microscopic scientific photography is described and illustrated, and methods for constructing such a dome are detailed. Dome illumination for insect specimens has become standard practice across the field of insect systematics, but many dome designs ...

  5. High coercivity of melt-spun Sm2Fe15Al2C1.5 compound

    NASA Astrophysics Data System (ADS)

    Zhang, Jun-Xian; Cheng, Zhao-Hua; Shen, Bao-Gen

    1996-04-01

    The magnetic hardening of melt-spun Sm2Fe17Cx was studied and the coercivity of 4.6 kOe for Sm2Fe17C1.5 alloys was reported a few years ago. Recently, we have succeeded in preparing single-phase compounds of Sm2(Fe, M)17Cx (M=Ga, Al, or Si) with high carbon concentration by arc melting. It was found that the substitution of Ga or Al not only facilitated the formation of high carbon concentration rare-earth iron compounds with a 2:17-type structure, but also was very effective in raising the value of the anisotropy field. For example, the sample of Sm2Fe15Al2C1.5 has a saturation magnetization of 110.2 emu/g, a Curie temperature of 576 K, and an anisotropy field of 111 kOe. It is known that melt spinning is an effective means to obtain high coercivity of magnetically hard materials. In this work, the hard magnetic properties of melt-spun Sm2Fe15Al2C1.5 alloys were investigated. It was found that the value of coercivity depends strongly on the quenching rates and an optimum coercivity of 9.4 kOe was obtained at the quenching rate of 20 m/s. X-ray diffraction patterns indicate that the as-quenched ribbons have a phase of the Th2Zn17-type structure. The high coercivity of these as-quenched ribbons originates from the excellent intrinsic magnetic properties of Sm2Fe15Al2C1.5. It can be concluded that the substitution of Al is very effective in raising the coercivity of melt-spun Sm2Fe15Al2C1.5 ribbons.

  6. Microstructure and electrochemical hydrogenation/dehydrogenation performance of melt-spun La-doped Mg{sub 2}Ni alloys

    SciTech Connect

    Hou, Xiaojiang; Hu, Rui; Zhang, Tiebang Kou, Hongchao; Song, Wenjie; Li, Jinshan

    2015-08-15

    This work focuses on microstructure and electrochemical hydrogen storage properties of La-doped Mg{sub 2}Ni alloys. The alloys with nominal compositions of Mg{sub 2}Ni{sub 1−x}La{sub x} (x = 0, 0.1, 0.3, 0.5) were prepared via metallurgical smelting and melt-spun on a rotating copper wheel. The scanning electron microscope, X-ray diffraction, differential scanning calorimetry and transition electron microscope, galvanostatic charging/discharging and other electrochemical measurements were employed to investigate. The results show that the increasing of La content and melt-spinning speed favors the formation of Mg–Ni–La amorphous/nanocrystalline alloys. It is found that the melt-spun ribbons display increased discharge capacities and superior cycle stabilities compared to the as-cast alloys with and without La. The potentiodynamic polarization results indicate that melt-spun La-doped Mg{sub 2}Ni ribbons possess more positive corrosion potential E{sub corr} and exhibit relatively high corrosion resistance against the alkaline solution. The mechanism for electrochemical hydrogenation/dehydrogenation has been proposed based on the effect of microstructures on the mass/charge transfer process for electrode electrochemical reaction. - Highlights: • Nanocrystalline/amorphous Mg–Ni–La alloys are obtained by melt-spinning. • Microstructures of as-cast and rapid quenched Mg{sub 2}Ni{sub 1−x}La{sub x} alloys are investigated. • Electrochemical hydrogenation properties of experimental alloys are characterized. • Electrochemical hydrogen absorption/desorption mechanism is proposed.

  7. Characterization of Atmospheric Ekman Spirals at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Rysman, Jean-François; Lahellec, Alain; Vignon, Etienne; Genthon, Christophe; Verrier, Sébastien

    2016-03-01

    We use wind speed and temperature measurements taken along a 45-m meteorological tower located at Dome C, Antarctica (75.06° S, 123.19° E) to highlight and characterize the Ekman spiral. Firstly, temperature records reveal that the atmospheric boundary layer at Dome C is stable during winter and summer nights (i.e., > 85 % of the time). The wind vector, in both speed and direction, also shows a strong dependence with elevation. An Ekman model was then fitted to the measurements. Results show that the wind vector follows the Ekman spiral structure for more than 20 % of the year (2009). Most Ekman spirals have been detected during summer nights, that is, when the boundary layer is slightly stratified. During these episodes, the boundary-layer height ranged from 25 to 100 m, the eddy viscosity from 0.004 to 0.06 m^2 s^{-1} , and the Richardson number from zero to 1.6.

  8. A Fourier transform spectrometer for site testing at Dome A

    NASA Astrophysics Data System (ADS)

    Li, Xin-Xing; Paine, Scott; Yao, Qi-Jun; Shi, Sheng-Cai; Matsuo, Hiroshi; Yang, Ji; Zhang, Qi-Zhou

    2009-07-01

    Observations in tera-hertz astronomy can only be done at a site with good atmospheric transmission at millimeter and submillimeter wavelengths. With extremely dry weather and calm atmosphere resulted by high altitude and cold temperature, Dome A (or Dome Argus), Antarctica, is possibly the best site on this earth for THz astronomy. To evaluate the site condition there, we are constructing a Fourier Transform Spectrometer (FTS) based on Martin-Puplett interferometer to measure the atmospheric transmission in the frequency range of 0.75~15THz. The whole FTS system is designed for unattended and outdoor (temperatures even below -70 degrees Celsius) operation. Its total power consumption is estimated to be approximately 200W. This contribution will give a brief overview of this FTS development.

  9. Nanocomposite optical ceramics for infrared windows and domes

    NASA Astrophysics Data System (ADS)

    Stefanik, Todd; Gentilman, Richard; Hogan, Patrick

    2007-04-01

    Currently available IR transparent materials typically exhibit a trade-off between optical performance and mechanical strength. For instance, sapphire domes are very strong, but lack full transparency throughout the 3-5 micron mid-wave IR band. Yttria is fully transparent from 3-5 microns, but lacks sufficient strength, hardness, and thermal shock resistance for the most demanding aero-thermal applications. Missile system designers must limit system performance in order to accommodate the shortcomings of available window and dome materials. Recent work in the area of nanocomposite ceramics may produce new materials that exhibit both excellent optical transparency and high strength, opening the door to improved missile performance. The requirements for optical nanocomposite ceramics will be presented and recent work in producing such materials will be discussed.

  10. Boscovich as an engineer: the statics of masonry domes

    NASA Astrophysics Data System (ADS)

    Corradi Dell'Acqu, L.

    The collection of writings by Ruggiero Boscovich contains a certain number of studies that can be considered of ``engineering'' character, mostly focusing on problems of hydraulics and structural mechanics. Nevertheless, such studies hardly can be regarded as part of Boscovich's direct interest. They were usually meant at answering specific questions, when Boscovich was acting as a consultant for people that were facing serious problems of different kind and asked his advise, considered as precious because of the prestige that Boscovich enjoyed in his time. In this paper attention is focused on one problem, the statics of masonry domes, which Boscovich faced twice in two different contexts. In these studies he employed, to my knowledge for the first time for computation purposes, a failure mechanism that at the end of the century became the basis for systematic and rigorous methods for the analysis of arches, vaults and domes. Boscovich work can be regarded as anticipating these results.

  11. SCIDAR: an optical turbulence profiler for Dome A

    NASA Astrophysics Data System (ADS)

    Liu, Li-Yong; Yao, Yong-Qiang; Vernin, Jean; Chadid, Merieme; Wang, Hong-Shuai; Wang, Yi-Ping

    2013-01-01

    This paper introduces a plan to detect turbulence profiles at Dome A with a Single Star Scidar (SSS), to enhance our understanding of the characteristics of the site. The development of a portable monitor for profiling vertical atmospheric optical turbulence and wind speed is presented. By analyzing the spatial auto and cross-correlation functions of very short exposure images of single star scintillation patterns, the SSS can provide the vertical profiles of turbulence intensity C 2 n (h) and wind speed V(h). A SSS prototype is already operational at Ali in Tibet which will be improved in order to become fully robotic and adapted to extreme weather conditions that prevail at Dome A in Antarctica.

  12. Linear and nonlinear optical absorption coefficients of spherical dome shells

    NASA Astrophysics Data System (ADS)

    Guo, Kangxian; Liu, Guanghui; Huang, Lu; Zheng, Xianyi

    2015-08-01

    Linear and nonlinear optical absorption coefficients of spherical dome shells are theoretically investigated within analytical wave functions and numerical quantized energy levels. Our results show that the inner radius, the outer radius and the cut-off angle of spherical dome shells have great influences on linear and nonlinear optical absorption coefficients as well as the total optical absorption coefficients. It is found that with the increase of the inner radius and the outer radius, linear and nonlinear optical absorption coefficients exhibit a blueshift and a redshift, respectively. However, with the increase of the cut-off angle, linear and nonlinear optical absorption coefficients do not shift. Besides, the resonant peaks of linear and nonlinear optical absorption coefficients climb up and then decrease with increasing the cut-off angle. The influences of the incident optical intensity on the total optical absorption coefficients are studied. It is found that the bleaching effect occurs at higher incident optical intensity.

  13. Arthroscopic intralesional curettage for large benign talar dome cysts

    PubMed Central

    El Shazly, Ossama; Abou El Soud, Maged M.; Nasef Abdelatif, Nasef Mohamed

    2015-01-01

    Introduction: Surgical management of large talar dome cysts is challenging due to increased morbidity by associated cartilage damage and malleolar osteotomy. The purpose of this study is to evaluate the clinical and radiological outcome of endoscopic curettage and bone graft for large talar dome cysts. Methods: This is a retrospective analysis of data for eight patients (eight feet) who were treated by arthroscopic curettage and grafting for large talar dome cysts. Seven cases were treated by posterior ankle arthroscopy as the lesion was located posteriorly while one case was treated by anterior ankle arthroscopy as the lesion was breached anteriorly. Results: The final diagnosis, was; large osteochondral lesion of talus (two cases), aneurysmal bone cyst (ABC) (two case), intra-osseous ganglion (two cases), Chronic infection in talus (one case) and angiomatous lesion of the talus (one case). The mean follow up period was 18.3 (±3.06 SD) months (range 16–25 months). The median preoperative AOFAS score was 74.5 (±5.34 SD) points. The mean postoperative AOFAS score at one year follow up was 94.6 (±2.97 SD) points. None of the patient had recurrence of the lesion during follow up. Return to normal daily activity was achieved at 11.25 (±2.37 SD) weeks. Discussion: In this short case series study, large talar dome bony cysts of different pathologies including aneurysmal bone cysts could be treated effectively by endoscopic curettage and bone grafting with no recurrence no complications during the follow-up period. PMID:27163087

  14. Mini-dome Fresnel lens photovoltaic concentrator development

    NASA Technical Reports Server (NTRS)

    Oneill, Mark J.; Piszczor, Michael F., Jr.

    1991-01-01

    Since 1986 work on a new high-performance, light-weight space photovoltaic concentration array has been conducted. An update on the mini-dome lens concentrator array development program is provided. Recent prototype cell and lens test results indicate that near-term array performance goals of 300 w/sq m and 100 w/kg are feasible, and that a longer-term goal of 200 w/kg is reasonable.

  15. Glacier geophysical studies at Taylor Dome: Your three

    SciTech Connect

    Morse, D.L.; Waddington, E.D. )

    1993-01-01

    Taylor Dome is the site of an ongoing ice core/paleoclimate project. The main activities of the 1992-1993 season included surveys by ground-based optical methods, surveys using satellite receivers, radio-echo sounding of bedrock topography, and depositional environment characterization. Monitoring continued of accumulation rate and three cores were sampled to detect the depths of atmospheric nuclear test fallout products. 5 refs., 1 fig.

  16. Analysis of the TMI-2 dome radiation monitor

    SciTech Connect

    Murphy, M B; Mueller, G M; Jernigan, W C

    1985-08-01

    Questions have been raised regarding the accuracy of the in-containment radiation readings from the LOCA qualified, dome radiation monitor, HP-R-214 during the March 28, 1979 accident at the Three Mile Island Unit 2 Reactor. This report discusses the accuracy of the readings, gives the results of examining the radiation monitor itself, and estimates the radiation environment inside containment during the accident.

  17. Ferrule and use thereof for cooling a melt spun hollow glass fiber as it emerges from a spinnerette

    DOEpatents

    Brown, William E.

    1977-01-01

    An improvement in the process of melt spinning thin walled, hollow fibers from relatively low melting glasses results if cooling of the emerging fiber is accomplished by use of a thin layer of gas to transfer heat from the fiber to a ferrule which fits closely to the spinnerette face and the individual fiber. The ferrule incorporates or is in contact with a heat sink and is slotted or segmented so that it may be brought into position around the moving fiber. Thinner walled, more uniform fibers may be spun when this method of cooling is employed.

  18. ON THE NATURE OF RECONNECTION AT A SOLAR CORONAL NULL POINT ABOVE A SEPARATRIX DOME

    SciTech Connect

    Pontin, D. I.; Priest, E. R.; Galsgaard, K.

    2013-09-10

    Three-dimensional magnetic null points are ubiquitous in the solar corona and in any generic mixed-polarity magnetic field. We consider magnetic reconnection at an isolated coronal null point whose fan field lines form a dome structure. Using analytical and computational models, we demonstrate several features of spine-fan reconnection at such a null, including the fact that substantial magnetic flux transfer from one region of field line connectivity to another can occur. The flux transfer occurs across the current sheet that forms around the null point during spine-fan reconnection, and there is no separator present. Also, flipping of magnetic field lines takes place in a manner similar to that observed in the quasi-separatrix layer or slip-running reconnection.

  19. Cybersickness Following Repeated Exposure to DOME and HMD Virtual Environments

    NASA Technical Reports Server (NTRS)

    Taylor, Laura C.; Harm, Deborah L.; Kennedy, Robert S.; Reschke, Millard F.; Loftin, R. Bowen

    2011-01-01

    Virtual environments (VE) offer unique training opportunities, including training astronauts to preadapt them to the novel sensory conditions of microgravity. However, one unresolved issue with VE use is the occurrence of cybersickness during and following exposure to VE systems. Most individuals adapt and become less ill with repeated interaction with VEs. The goal of this investigation was to compare motion sickness symptoms (MSS) produced by dome and head-mounted (HMD) displays and to examine the effects of repeated exposures on MSS. Sixty-one subjects participated in the study. Three experimental sessions were performed each separated by one day. The subjects performed a navigation and pick and place task in either a dome or HMD VE. MSS were measured using a Simulator Sickness Questionnaire before, immediately after, and at 1, 2, 4 and 6 hours following exposure to the VEs. MSS data were normalized by calculating the natural log of each score and an analysis of variance was performed. We observed significant main effects for day and time and a significant day by time interaction for total sickness and for each of the subscales, nausea, oculomotor and disorientation. However, there was no significant main effect for device. In conclusion, subjects reported a large increase in MSS immediately following exposure to both the HMD and dome, followed by a rapid recovery across time. Sickness severity also decreased over days, which suggests that subjects become dual-adapted over time making VE training a viable pre-flight countermeasure for space motion sickness.

  20. Upgrading, monitoring and operation of a dome drive system

    NASA Astrophysics Data System (ADS)

    Bauman, Steven E.; Cruise, Bill; Look, Ivan; Matsushige, Grant; Roberts, Larry; Salmon, Derrick; Taroma, Ralph; Vermeulen, Tom; Richards, Krieg

    2014-08-01

    CFHT's decision to move away from classical observing prompted the development of a remote observing environment aimed at producing science observations from headquarters facility in Waimea, HI. This remote observing project commonly referred to as the Observatory Automation Project (OAP ) was completed at the end of January 2011 and has been providing the majority of science data ever since. A comprehensive feasibility study was conducted to determine the options available to achieve remote operations of the observatory dome drive system. After evaluation, the best option was to upgrade the original hydraulic system to utilize variable frequency drive (VFD) technology. The project upgraded the hydraulic drive system, which initially utilized a hydraulic power unit and three (3) identical drive units to rotate the dome. The new electric drive system replaced the hydraulic power unit with electric motor controllers, and each drive unit reuses the original drive and swaps one for one the original hydraulic motors with an electric motor. The motor controllers provide status and monitoring parameters for each drive unit which convey the functionality and health of the system. This paper will discuss the design upgrades to the dome drive rotation system, as well as some benefits, control, energy savings, and monitoring.

  1. Winter sky brightness and cloud cover at Dome A, Antarctica

    NASA Astrophysics Data System (ADS)

    Moore, Anna M.; Yang, Yi; Fu, Jianning; Ashley, Michael C. B.; Cui, Xiangqun; Feng, Long Long; Gong, Xuefei; Hu, Zhongwen; Lawrence, Jon S.; Luong-Van, Daniel M.; Riddle, Reed; Shang, Zhaohui; Sims, Geoff; Storey, John W. V.; Tothill, Nicholas F. H.; Travouillon, Tony; Wang, Lifan; Yang, Huigen; Yang, Ji; Zhou, Xu; Zhu, Zhenxi

    2013-01-01

    At the summit of the Antarctic plateau, Dome A offers an intriguing location for future large scale optical astronomical observatories. The Gattini Dome A project was created to measure the optical sky brightness and large area cloud cover of the winter-time sky above this high altitude Antarctic site. The wide field camera and multi-filter system was installed on the PLATO instrument module as part of the Chinese-led traverse to Dome A in January 2008. This automated wide field camera consists of an Apogee U4000 interline CCD coupled to a Nikon fisheye lens enclosed in a heated container with glass window. The system contains a filter mechanism providing a suite of standard astronomical photometric filters (Bessell B, V, R) and a long-pass red filter for the detection and monitoring of airglow emission. The system operated continuously throughout the 2009, and 2011 winter seasons and part-way through the 2010 season, recording long exposure images sequentially for each filter. We have in hand one complete winter-time dataset (2009) returned via a manned traverse. We present here the first measurements of sky brightness in the photometric V band, cloud cover statistics measured so far and an estimate of the extinction.

  2. Small domes on Venus: probable analogs of Icelandic lava shields

    USGS Publications Warehouse

    Garvin, James B.; Williams, Richard S., Jr.

    1990-01-01

    On the basis of observed shapes and volumetric estimates, we interpret small, dome-like features on radar images of Venus to be analogs of Icelandic lava-shield volcanoes. Using morphometric data for venusian domes in Aubele and Slyuta (in press), as well as our own measurements of representative dome volumes and areas from Tethus Regio, we demonstrate that the characteristic aspect ratios and flank slopes of these features are consistent with a subclass of low Icelandic lava-shield volcanoes (LILS ). LILS are slightly convex in cross-section with typical flank slopes of ∼3°. Plausible lava-shield-production rates for the venusian plains suggest formation of ∼53 million shields over the past 0.25 Ga. The cumulative global volume of lava that would be associated with this predicted number of lava shields is only a factor of 3–4 times that of a single oceanic composite shield volcano such as Mauna Loa. The global volume of all venusian lava shields in the 0.5–20-km size range would only contribute a meter of resurfacing over geologically significant time scales. Thus, venusian analogs to LILS may represent the most abundant landform on the globally dominant plains of Venus, but would be insignificant with regard to the global volume of lava extruded. As in Iceland, associated lavas from fissure eruptions probably dominate plains volcanism and should be evident on the higher resolution Magellan radar images.

  3. The dome-shaped Fresnel-Köhler concentrator

    NASA Astrophysics Data System (ADS)

    Zamora, P.; Benitez, P.; Li, Y.; Miñano, J. C.; Mendes-Lopes, J.; Araki, K.

    2012-10-01

    Manufacturing tolerances, along with a high concentration ratio, are key issues in order to obtain cheap CPV systems for mass production. Consequently, this manuscript presents a novel tolerant and cost effective concentrator optic: the domed-shaped Fresnel-Köhler, presenting a curved Fresnel lens as Primary Optical Element (POE). This concentrator is based on two previous successful CPV designs: the FK concentrator, based on a flat Fresnel lens, and the dome-shaped Fresnel lens system developed by Daido Steel, resulting on a superior concentrator. The manuscript shows outstanding simulation results for geometrical concentration factor of Cg = 1,230x: high tolerance and high optical efficiency, achieving acceptance angles of 1.18° (dealing to a CAP*=0.72) and efficiencies over 85% (without any anti-reflective coating). Moreover, Köhler integration provides good irradiance uniformity on the cell surface without increasing system complexity by means of any extra element. Daido Steel advanced technique for demolding injected plastic pieces will allow for easy manufacture of the dome-shaped POE of DFK concentrator.

  4. Forecasting Lava Dome Eruptions from High Frequency Seismicity

    NASA Astrophysics Data System (ADS)

    Smith, R.; Kilburn, C. R.; Sammonds, P. R.

    2005-12-01

    Following its plinian eruption on 18 May 1980, Mount St Helens (Washington State, U.S.A.) entered a period of intermittent lava-dome extrusion until 1986. A re-analysis of the timing of volcano-tectonic (VT) earthquakes and eruptions indicates that: (1) all VT crises resulted in an eruption within 3 weeks (usually less than 10 days), (2) the majority of eruptions had VT precursors, and (3) patterns of precursory seismicity showed significant variations. Thus, although these seismic events could be used to warn of an impending eruption, specific forecasts were subject to significant uncertainty. It is proposed that: (1) Increased seismicity prior to later eruptions are a result of a larger more solidified dome acting as a greater impediment to magma ascent; (2) the consistency of seismic swarms resulting in an eruption indicate that stresses high enough to initiate fracturing in the country rock and lava dome carapace were only achieved once the approach to an eruption had already begun; and (3) discrepancies between models of accelerating rock fracture and the observed seismicity may arise due to a significant amount of the material failing and deforming through ductile mechanisms rather than seismogenic fracture.

  5. An Operationally Based Vision Assessment Simulator for Domes

    NASA Technical Reports Server (NTRS)

    Archdeacon, John; Gaska, James; Timoner, Samson

    2012-01-01

    The Operational Based Vision Assessment (OBVA) simulator was designed and built by NASA and the United States Air Force (USAF) to provide the Air Force School of Aerospace Medicine (USAFSAM) with a scientific testing laboratory to study human vision and testing standards in an operationally relevant environment. This paper describes the general design objectives and implementation characteristics of the simulator visual system being created to meet these requirements. A key design objective for the OBVA research simulator is to develop a real-time computer image generator (IG) and display subsystem that can display and update at 120 frame s per second (design target), or at a minimum, 60 frames per second, with minimal transport delay using commercial off-the-shelf (COTS) technology. There are three key parts of the OBVA simulator that are described in this paper: i) the real-time computer image generator, ii) the various COTS technology used to construct the simulator, and iii) the spherical dome display and real-time distortion correction subsystem. We describe the various issues, possible COTS solutions, and remaining problem areas identified by NASA and the USAF while designing and building the simulator for future vision research. We also describe the critically important relationship of the physical display components including distortion correction for the dome consistent with an objective of minimizing latency in the system. The performance of the automatic calibration system used in the dome is also described. Various recommendations for possible future implementations shall also be discussed.

  6. Lunar Mare Dome Identification and Morphologic Properties Analysis Using Chang'E-2 Lunar Data

    NASA Astrophysics Data System (ADS)

    Zeng, Xingguo; Mu, Lingli; Li, Chunlai; Liu, Jianjun; Ren, Xin; Wang, Yuanyuan

    2016-04-01

    Identify the lunar mare dome and study the morphologic properties to know more knowledge about the structure will enhance the study of lunar volcanism. Traditionally, most lunar domes are identified by the scientists from exploring the images or topographic maps of the lunar surface with manual method, which already found out a bunch of lunar domes in specific local areas. For the purpose of getting more knowledge about global lunar dome, it is necessary to identify the lunar dome from the global lunar mare. However, it is hard to find new lunar domes from the global lunar mare only with manual method, since in that case, the large volume lunar data is needed and such work is too time consumed, so that, there are few researchers who have indentified and study the properties of the lunar dome from the perspective of lunar global scale. To solve the problem mentioned above, in this approach , CE-2 DEM, DOM data in 7m resolution were used in the detection and morphologic analysis of the lunar domes and a dome detection method based on topographic characteristics were developed.We firstly designed a method considering the morphologic characteristics to identify the lunar dome with Chang'E2(CE-2) lunar global data, after that, the initial identified result with properties is analyzed, and finally, by integrating the result with lunar domes already found by former researchers, we made some maps about the spatial distribution of the global lunar mare dome. With the CE-2 data covering the former lunar domes and the new found lunar domes, we surveyed and calculated some morphologic properties, and found that, lunar domes are circular or eclipse shaped, obviously different from background in topography,which has a average diameter between 3-25km, circular degree less than 1.54, with a average slope less than 10°, average height less than 650m and diameter/height less than 0.065. Almost all of the lunar domes are located in the extent of 58°N~54°S,167°W~180°E,and nearly

  7. Dome design and coupled thermal-mechanical analysis of supersonic missile

    NASA Astrophysics Data System (ADS)

    Ai, Xing-qiao; Wei, Qun; Jia, Hong-guang

    2009-11-01

    A review of high-speed flow pressure and aerodynamic heating effect on Supersonic missile's dome is given. The dome should have excellent properties in optical, mechanical and chemical characteristics. A design of dome on supersonic mode is described according to tactical guide line of a missile. The dome made of quartz which is about 8mm thick and 141mm in window diameter. To check up the reliability of the dome, a reasonable finite element model (FEM) of dome is established, and a thermal-mechanical Analysis to the dome by finite element software NASTRAN has carried on, through these can obtained the distribution of temperature field and stress field when the speed is 2.3Ma. The results indicated that the stress was concentrated in the joint of the dome end and the Missile Section, and the maximum stress was 16.4Mpa. The stress of other nodes was smaller than the allowable stress of quartz glass. Reference to the results of the analysis, a lightweight revision to the dome structural dimension and a new method of dome fixing have put forward, which can reduce the stress concentration.

  8. Design and Development of a Composite Dome for Experimental Characterization of Material Permeability

    NASA Technical Reports Server (NTRS)

    Estrada, Hector; Smeltzer, Stanley S., III

    1999-01-01

    This paper presents the design and development of a carbon fiber reinforced plastic dome, including a description of the dome fabrication, method for sealing penetrations in the dome, and a summary of the planned test series. This dome will be used for the experimental permeability characterization and leakage validation of composite vessels pressurized using liquid hydrogen and liquid nitrogen at the Cryostat Test Facility at the NASA Marshall Space Flight Center (MSFC). The preliminary design of the dome was completed using membrane shell analysis. Due to the configuration of the test setup, the dome will experience some flexural stresses and stress concentrations in addition to membrane stresses. Also, a potential buckling condition exists for the dome due to external pressure during the leak testing of the cryostat facility lines. Thus, a finite element analysis was conducted to assess the overall strength and stability of the dome for each required test condition. Based on these results, additional plies of composite reinforcement material were applied to local regions on the dome to alleviate stress concentrations and limit deflections. The dome design includes a circular opening in the center for the installation of a polar boss, which introduces a geometric discontinuity that causes high stresses in the region near the hole. To attenuate these high stresses, a reinforcement system was designed using analytical and finite element analyses. The development of a low leakage polar boss system is also investigated.

  9. Glacier melting during lava dome growth at Nevado de Toluca volcano (Mexico): Evidences of a major threat before main eruptive phases at ice-caped volcanoes

    NASA Astrophysics Data System (ADS)

    Capra, L.; Roverato, M.; Groppelli, G.; Caballero, L.; Sulpizio, R.; Norini, G.

    2015-03-01

    Nevado de Toluca volcano is one of the largest stratovolcanoes in the Trans-Mexican Volcanic Belt. During Late Pleistocene its activity was characterized by large dome growth and subsequent collapse emplacing large block and ash flow deposits, intercalated by Plinian eruptions. Morphological and paleoclimate studies at Nevado de Toluca and the surrounding area evidenced that the volcano was affected by extensive glaciation during Late Pleistocene and Holocene. During the older recognized glacial period (27-60 ka, MIS 3), the glacier was disturbed by the intense magmatic and hydrothermal activity related to two dome extrusion episodes (at 37 ka and 28 ka). Glacier reconstruction indicates maximum ice thickness of 90 m along main valleys, as at the Cano ravines, the major glacial valley on the northern slope of the volcano. Along this ravine, both 37 and 28 ka block-and-ash deposits are exposed, and they directly overlay a fluviatile sequence, up to 40 m-thick, which 14C ages clearly indicate that their emplacement occurred just before the dome collapsed. These evidences point to a clear interaction between the growing dome and its hydrothermal system with the glacier. During dome growth, a large amount of melting water was released along major glacial valleys forming thick fluvioglacial sequences that were subsequently covered by the block-and-ash flow deposits generated by the collapse of the growing dome. Even though this scenario is no longer possible at the Nevado de Toluca volcano, the data presented here indicate that special attention should be paid to the possible inundation areas from fluviatile/lahar activity prior to the main magmatic eruption at ice-capped volcanoes.

  10. Merapi's lava dome splitting explosion on 18 November 2013 observed by lidar and digital image correlation analysis.

    NASA Astrophysics Data System (ADS)

    Darmawan, Herlan; Walter, Thomas; Nikkhoo, Mehdi; Richter, Nicole

    2015-04-01

    After the 2010 Merapi eruption, the lava dome in the summit of the volcano was firstly growing and then subject to gradual cooling and contraction. In November 2013, a major phreatomagmatic explosion occurred, which caused an eruption column rising over 2 km high and destroyed a number of monitoring instruments in the near field. Bombs were thrown out over 1 km distance. The eruption produced volcanic ash and very fine materials. Deformation data from tilt or EDM showed no wide inflation or deflation associated with this eruption. In addition, high resolution TerraSAR-X data analysis also showed no edifice-wide deformation (Walter et al., 2015). Here we further examine two datasets to determine the morphologic and structural effects of this eruption. First we exploit fixed installed monitoring cameras and use a digital image correlation method to investigate geometric changes before and after the eruption. Second we acquired a high resolution terrestrial Lidar data set after the explosion and compared this another lidar data set acquired before. The result shows details on the splitted dome, the volume of the eruption and thickness of the deposits, and suggests that a new block at the front of the dome is inherently unstable and might break off to form a block and ash flow in the near future. Reference: TR Walter, Subandriyo J, Kirbani S, Bathke H, Suryanto W, Aisyah N, Darmawan H, Jousset P, Lühr BG, Dahm T (2015) Volcano-tectonic control of Merapi's lava dome splitting: The November 2013 fracture observed from high resolution TerraSAR-X data. Tectonophysics 639, 12 January 2015, Pages 23-33. doi:10.1016/j.tecto.2014.11.007

  11. Microbial characterization of microbial ecosystems associated to evaporites domes of gypsum in Salar de Llamara in Atacama desert.

    PubMed

    Rasuk, Maria Cecilia; Kurth, Daniel; Flores, Maria Regina; Contreras, Manuel; Novoa, Fernando; Poire, Daniel; Farias, Maria Eugenia

    2014-10-01

    The Central Andes in northern Chile contains a large number of closed basins whose central depression is occupied by saline lakes and salt crusts (salars). One of these basins is Salar de Llamara (850 m a.s.l.), where large domed structures of seemingly evaporitic origin forming domes can be found. In this work, we performed a detailed microbial characterization of these domes. Mineralogical studies revealed gypsum (CaSO(4)) as a major component. Microbial communities associated to these structures were analysed by 454 16S rDNA amplicon sequencing and compared between winter and summer seasons. Bacteroidetes Proteobacteria and Planctomycetes remained as the main phylogenetic groups, an increased diversity was found in winter. Comparison of the upper air-exposed part and the lower water-submerged part of the domes in both seasons showed little variation in the upper zone, showing a predominance of Chromatiales (Gammaproteobacteria), Rhodospirillales (Alphaproteobacteria), and Sphingobacteriales (Bacteroidetes). However, the submerged part showed marked differences between seasons, being dominated by Proteobacteria (Alpha and Gamma) and Verrucomicrobia in summer, but with more diverse phyla found in winter. Even though not abundant by sequence, Cyanobacteria were visually identified by scanning electron microscopy (SEM), which also revealed the presence of diatoms. Photosynthetic pigments were detected by high-performance liquid chromatography, being more diverse on the upper photosynthetic layer. Finally, the system was compared with other endoevaporite, mats microbialite and Stromatolites microbial ecosystems, showing higher similitude with evaporitic ecosystems from Atacama and Guerrero Negro. This environment is of special interest for extremophile studies because microbial life develops associated to minerals in the driest desert all over the world. Nevertheless, it is endangered by mining activity associated to copper and lithium extraction; thus, its

  12. Soluble extracts from Helicobacter pylori induce dome formation in polarized intestinal epithelial monolayers in a laminin-dependent manner.

    PubMed

    Terrés, A M; Windle, H J; Ardini, E; Kelleher, D P

    2003-07-01

    Helicobacter pylori colonizes the stomach at the interface between the mucus layer and the apical pole of gastric epithelial cells. A number of secreted and shed products from the bacteria, such as proteins and lipopolysaccharide, are likely to have a role in the pathogenesis at the epithelial level. To determine the physiological response of transporting polarized epithelia to released soluble factors from the bacterium, we used the T84 cell line. Monolayers of T84 cells were exposed to soluble extracts from H. pylori. The extracts induced rapid "dome" formation as well as an immediate decrease in transepithelial electrical resistance. Domes are fluid-filled blister-like structures unique to polarized epithelia. Their formation has been linked to sodium-transporting events as well as to diminished adherence of the cells to the substrate. H. pylori-induced dome formation in T84 monolayers was exacerbated by amiloride and inhibited by ouabain. Furthermore, it was associated with changes in the expression of the laminin binding alpha 6 beta 4 integrin and the 67-kDa laminin receptor. Domes formed primarily on laminin-coated filters, rather than on fibronectin or collagen matrices, and their formation was inhibited by preincubating the bacterial extract with soluble laminin. This effect was specific to H. pylori and independent of the urease, vacA, cagA, and Lewis phenotype of the strains. These data indicate that released elements from H. pylori can alter the physiological balance and integrity of the epithelium in the absence of an underlying immune response. PMID:12819097

  13. Long and complex thermal history of the Song Chay metamorphic dome (Northern Vietnam) by multi-system geochronology

    NASA Astrophysics Data System (ADS)

    Roger, Francoise; Leloup, Philippe Hervé; Jolivet, Marc; Lacassin, Robin; Trinh, Phan Trong; Brunel, Maurice; Seward, Diane

    2000-06-01

    Multi-system geochronology was used to unravel the long and complex thermal history of the Song Chay range (Northern Vietnam), a high-grade granitic and metamorphic dome in the vicinity of the Cenozoic, Ailao Shan-Red River fault zone. It was considered to be Proterozoic South China basement, but its geological history was basically unknown. Scattered field observations suggest three episodes of high-temperature deformation: firstly at the time of granite emplacement, secondly a décollement with top to the north shear and thirdly anticlinal doming of the foliations formed during the two first stages. P- T estimates suggest that metamorphism coeval with the second deformation phase culminated at ˜580°C and ˜4.5 kbar (˜16 km depth). Multi-system geochronology is applied to a two-micas granite sample, slightly deformed within the décollement. U/Pb dating of zircon yields an age of 428±5 Ma (±2 σ) interpreted as the time of granite crystallization within the South China 'Caledonian' belt. Rb/Sr on white micas and biotite yields ages of 206±10 Ma and 176±5.3 Ma, respectively (2 σ), whereas 39Ar/ 40Ar ages of the same minerals are 210±9 and 190±8 Ma (2 σ). These ages suggest an Upper Triassic episode of rapid cooling interpreted as due to doming a few million years after the end of movement on the décollement. The K-feldspar irregular 39Ar/ 40Ar age spectrum can, to the first order, be explained by a cooling history with two episodes of rapid cooling: one at ˜140 Ma and a second around 41 to 25 Ma. Apatite fission tracks central age (33.6±3.6 Ma, 1 σ) confirms a Tertiary rapid cooling event interpreted as the final exhumation of the Song Chay dome.

  14. TEM microstructural characterization of melt-spun aged Al-6Si-3Cu-xMg alloys

    SciTech Connect

    Lopez, Ismeli Alfonso . E-mail: post18@jupiter.umich.mx; Zepeda, Cuauhtemoc Maldonado; Gonzalez Reyes, Jose Gonzalo; Flores, Ariosto Medina; Rodriguez, Juan Serrato; Gomez, Luis Bejar

    2007-06-15

    Three Al-6Si-3Cu-xMg alloys (x = 0.59, 3.80 and 6.78 wt.%) were produced using melt-spinning. As-melt-spun ribbons were aged at 150, 180 and 210 deg. C for times between 0.05 and 100 h. Microstructural changes were examined using transmission electron microscopy (TEM) and microhardness was measured. TEM analysis of the as-melt-spun alloys revealed 5 nm nanoparticles and larger particles (50 nm) composed of Al{sub 2}Cu ({theta}) for the 0.59% Mg alloy and Al{sub 5}Cu{sub 2}Mg{sub 8}Si{sub 6} (Q) for 3.80% and 6.78% Mg alloys. Silicon solid solubility was extended to 9.0 at.% and Mg in solid solution reached 6.7 at.%. After aging treatments the 6.78% Mg alloy exhibited the most significant increase in microhardness, reaching 260 kg/mm{sup 2}. TEM analysis of aged specimens also showed {theta} and Q phase (5-20 nm nanoparticles and 35-40 nm particles). The combination of the volume fraction and size of the particles plays an important role in microhardness variation.

  15. Effect of stretching on the mechanical properties in melt-spun poly(butylene succinate)/microfibrillated cellulose (MFC) nanocomposites.

    PubMed

    Zhou, Mi; Fan, Mao; Zhao, Yongsheng; Jin, Tianxiang; Fu, Qiang

    2016-04-20

    In order to prepare poly(butylene succinate)/microfibrillated cellulose composites with high performance, in this work, microfibrillated cellulose (MFC) was first treated by acetylchloride with ball-milling to improve its interfacial compatibility with poly(butylene succinate) (PBS). Then melt stretching processing was adopted to further improve the dispersion and orientation of MFC in as-spun PBS fiber. And the effect of MFC on the crystalline structure and mechanical properties were systematically investigated for the melt-spun fibers prepared with two different draw ratios. The dispersion, alignment of the MFC and interfacial crystalline structure in the composite fibers are significantly influenced by the stretching force during the melt spinning. The possible formation of nanohybrid shish kebab (NHSK) superstructure where aligned MFC as shish and PBS lamellae as kebab has been suggested via SEM and SAXS in the composite fibers prepared at the high draw ratio. Large improvement in tensile strength has been realized at the high draw ratio due to the enhanced orientation and dispersion of MFC as well as the formation of NHSK. PMID:26876865

  16. 7-forming, superconducting filaments through bicomponent dry spinning

    DOEpatents

    Tuominen, Olli P.; Morgan, Carol W.; Burlone, Dominick A.; Blankenship, Keith V.

    2001-01-01

    Fibers which contain potentially superconducting material are dry spun by the steps of preparing a suspension of potentially superconducting powder in a thickened solvent; preparing a solution of fiber-forming polymer; supplying the suspension and the solution to a spinning apparatus; in the spinning apparatus, arranging the solution and the suspension in a bicomponent arrangement; extruding the arranged solution and suspension from a spinneret as a bicomponent filament; and removing the solvent from the filament.

  17. Optimized design of the inside surface of supersonic missile's elliptical dome

    NASA Astrophysics Data System (ADS)

    Wei, Qun; Bai, Yang; Liu, Hui; Jia, Hongguang; Xuan, Ming

    2009-07-01

    Dome is the head of a missile which has such a strong effect on the missile's drag. When missiles attack at high speed, the drag caused by sphere dome is 50%~60% of whole missile's drag [1]. In order to reduce the dome's drag, the idea of "conformal optics" is studied in some papers. The state of the art of conformal optics is described in James P.Mils paper [2]. But most people's work focus on the outside of dome's shape design. This paper presents a way to design the dome's inside surface. This paper is composed by three main parts. The first part expands the calculation of dome's outflow and the shock wave. The second section describes how the optical optimizing function made. Finally, the last section shows the result.

  18. Conceptual model for regional radionuclide transport from a salt dome repository: a technical memorandum

    SciTech Connect

    Kier, R.S.; Showalter, P.A.; Dettinger, M.D.

    1980-05-30

    Disposal of high-level radioactive wastes is a major environmental problem influencing further development of nuclear energy in this country. Salt domes in the Gulf Coast Basin are being investigated as repository sites. A major concern is geologic and hydrologic stability of candidate domes and potential transport of radionuclides by groundwater to the biosphere prior to their degradation to harmless levels of activity. This report conceptualizes a regional geohydrologic model for transport of radionuclides from a salt dome repository. The model considers transport pathways and the physical and chemical changes that would occur through time prior to the radionuclides reaching the biosphere. Necessary, but unknown inputs to the regional model involve entry and movement of fluids through the repository dome and across the dome-country rock interface and the effect on the dome and surrounding strata of heat generated by the radioactive wastes.

  19. Venus pancake dome formation: Morphologic effects of a cooling-induced variable viscosity during emplacement

    NASA Technical Reports Server (NTRS)

    Sakimoto, S. E. H.; Zuber, M. T.

    1993-01-01

    The distinctive steep-sided 'pancake' domes discovered in the Magellan images of Venus have morphologies that suggest formation by a single continuous emplacement of a high viscosity magma. A resemblance of the venusian domes to much smaller terrestrial rhyolite and dacite volcanic domes has prompted some authors to suggest that the domes on Venus also have high silica compositions and thus, high viscosities. However, viscosity is a function of crystallinity as well as silica content in a magma, and thus increases as a result of magmatic cooling. To investigate the effect of a cooling-induced viscosity increase on dome morphology, we have modeled the domes as radial viscous gravity currents that cool during emplacement. Various aspects of the investigation are discussed.

  20. Deformation, lava dome evolution, and eruption cyclicity at Merapi volcano, Indonesia

    NASA Astrophysics Data System (ADS)

    Young, Kirby D.

    Deformation monitoring results are reported here for the period 1988-1998 at Merapi volcano, one of the most active and dangerous volcanoes in Indonesia. Comprehensive databases of various geophysical parameters were concurrently studied and analyzed to 2000, and similar data were subsequently considered during periods of eruption crisis in 2001 and 2006. Of particular emphasis was the study of lava eruption rates based on dome volume estimates and seismic proxies for dome collapse volumes. The detailed study period of deformation includes a major resumption in lava effusion in January 1992 and major dome collapses in November 1994, January 1997, and July 1998. Monitoring techniques employed in the field are of two types. Translational movements were recorded via electronic distance measurements (EDM) on a summit trilateration network, slope distance changes measured to the upper flanks, and other data collected from 1988 to 1995. Tilt changes were detected by a summit and flank network of tilt stations that operated at various times from 1993 to 1998. A major consequence of the deformation results is the documentation of a significant 4-year period of deformation precursory to the 1992 eruption. Cross-crater strain rates accelerated from less than 3 x 10-6/day between 1988 and 1990 to more than 11 x 10-6/day just prior to the January 1992 activity, representing a general, asymmetric extension of the summit during highlevel conduit pressurization. After the vent opened and effusion of lava resumed, strain occurred at a much reduced rate of less than 2 x 10-6/day. The Gendol breach, a pronounced depression formed by the juxtaposition of old lava coulees on the southeast flank, functioned as a major displacement discontinuity. An elevated phase of magma production with respect to the long-term rate for the 20th Century characterized the activity at Merapi volcano, Central Java/Yogyakarta, Indonesia, for the period 1992-2006. Most large (0.2 - 3.4 x 106 m3) dome

  1. The geology and mechanics of formation of the Fort Rock Dome, Yavapai County, Arizona

    USGS Publications Warehouse

    Fuis, Gary S.

    1996-01-01

    The Fort Rock Dome, a craterlike structure in northern Arizona, is the erosional product of a circular domal uplift associated with a Precambrian shear zone exposed within the crater and with Tertiary volcanism. A section of Precambrian to Quaternary rocks is described, and two Tertiary units, the Crater Pasture Formation and the Fort Rock Creek Rhyodacite, are named. A mathematical model of the doming process is developed that is consistent with the history of the Fort Rock Dome.

  2. A decade of dome growth at Mount St. Helens, 1980-90

    USGS Publications Warehouse

    Swanson, D.A.

    1990-01-01

    The growth of the dacite dome at Mount St. Helens between 1980 and 1986 has been more intensively studied than that of any other dome-building eruption. The growth has been complex in detail, but remarkably regular overall. This paper summarizes some of what has been learned and provides many references to additional information. Whether dome building has ended is an open question, particularly in view of the renewed, though minor, explosive activity of late 1989 and early 1990. -Author

  3. Method of estimating time scales of the atmospheric piston and its application at Dome C (Antarctica).

    PubMed

    Kellerer, Aglae; Sarazin, Marc; du Foresto, Vincent Coudé; Agabi, Karim; Aristidi, Eric; Sadibekova, Tatyana

    2006-08-01

    Analysis of the first interferometric fringes recorded at Dome C, Antarctica are presented. Measurements were taken 31 January and 1 February 2005 during daytime. Our purpose in performing the analysis was to measure temporal fluctuations of the atmospheric piston, which are critical for interferometers, and determine their sensitivity. These scales are derived through the motion of the image that is formed in the focal plane of a Fizeau interferometer. We could establish a lower limit to the coherence time by studying the decay rate of correlation between successive fringes. Coherence times are measured to be larger than 10 ms, i.e., at least three times higher than the median coherence time measured at the site of Paranal (3.3 ms). PMID:16855670

  4. Method of estimating time scales of the atmospheric piston and its application at Dome C (Antarctica)

    SciTech Connect

    Kellerer, Aglae; Sarazin, Marc; Coude du Foresto, Vincent; Agabi, Karim; Aristidi, Eric; Sadibekova, Tatyana

    2006-08-01

    Analysis of the first interferometric fringes recorded at Dome C, Antarctica are presented. Measurements were taken 31 January and 1 February 2005 during daytime. Our purpose in performing the analysis was to measure temporal fluctuations of the atmospheric piston, which are critical for interferometers, and determine their sensitivity.These scales are derived through the motion of the image that is formed in the focal plane of a Fizeau interferometer.We could establish a lower limit to the coherence time by studying the decay rate of correlation between successive fringes. Coherence times are measured to be larger than 10 ms, i.e., at least three times higher than the median coherence time measured at the site of Paranal(3.3 ms)

  5. A Scalable and Modular Dome Illumination System for Scientific Microphotography on a Budget

    PubMed Central

    Kawada, Ricardo; Buffington, Matthew L.

    2016-01-01

    A scalable and modular LED illumination dome for microscopic scientific photography is described and illustrated, and methods for constructing such a dome are detailed. Dome illumination for insect specimens has become standard practice across the field of insect systematics, but many dome designs remain expensive and inflexible with respect to new LED technology. Further, a one-size-fits-all dome cannot accommodate the large breadth of insect size encountered in nature, forcing the photographer to adapt, in some cases, to a less than ideal dome design. The dome described here is scalable, as it is based on a isodecahedron, and the template for the dome is available as a downloaded file from the internet that can be printed on any printer, on the photographer’s choice of media. As a result, a photographer can afford, using this design, to produce a series of domes of various sizes and materials, and LED ring lights of various sizes and color temperatures, depending on the need. PMID:27138573

  6. Identifying and inventorying cypress domes in the Florida panhandle using Landsat imagery

    NASA Astrophysics Data System (ADS)

    Calaminus, Andre Kyle

    Cypress domes are swamp ecosystems dominated by pond cypress (Taxodium ascendens), a conifer native to North America. Cypress domes can be found in flatland depressions throughout the southeast United States, hydrologically separated from other water bodies. Threatened by urbanization and land use change, these unique ecosystems have experienced degradation, destruction, and habitat loss over the past few decades. While many domes have been identified in central and southern Florida, literature is lacking on cypress domes found in the Florida panhandle. Cypress domes within the Florida panhandle were located, inventoried, and analyzed for landscape patterns, including size and shape. Additionally, the cypress dome areas were subject to pixel change detection for temporal comparison of dome size from 2000 to 2013. Using satellite imagery from the Landsat 8 spacecraft, support vector machine classification, and publicly available data, a total of 1,568 cypress domes were found to exist in the Florida panhandle, with a mean area of 1.28 hectares, ranging from a minimum of 0.13 ha to a maximum of 4.95 ha, occupying 19.79 km2, or 0.078% of the panhandle study area. A change detection analysis over the 13 year period show a net gain of 284.63 ha in cypress dome growth.

  7. A Scalable and Modular Dome Illumination System for Scientific Microphotography on a Budget.

    PubMed

    Kawada, Ricardo; Buffington, Matthew L

    2016-01-01

    A scalable and modular LED illumination dome for microscopic scientific photography is described and illustrated, and methods for constructing such a dome are detailed. Dome illumination for insect specimens has become standard practice across the field of insect systematics, but many dome designs remain expensive and inflexible with respect to new LED technology. Further, a one-size-fits-all dome cannot accommodate the large breadth of insect size encountered in nature, forcing the photographer to adapt, in some cases, to a less than ideal dome design. The dome described here is scalable, as it is based on a isodecahedron, and the template for the dome is available as a downloaded file from the internet that can be printed on any printer, on the photographer's choice of media. As a result, a photographer can afford, using this design, to produce a series of domes of various sizes and materials, and LED ring lights of various sizes and color temperatures, depending on the need. PMID:27138573

  8. Longitudinal biases in the Seychelles Dome simulated by 35 ocean-atmosphere coupled general circulation models

    NASA Astrophysics Data System (ADS)

    Nagura, Motoki; Sasaki, Wataru; Tozuka, Tomoki; Luo, Jing-Jia; Behera, Swadhin K.; Yamagata, Toshio

    2013-02-01

    Seychelles Dome refers to the shallow climatological thermocline in the southwestern Indian Ocean, where ocean wave dynamics efficiently affect sea surface temperature, allowing sea surface temperature anomalies to be predicted up to 1-2 years in advance. Accurate reproduction of the dome by ocean-atmosphere coupled general circulation models (CGCMs) is essential for successful seasonal predictions in the Indian Ocean. This study examines the Seychelles Dome as simulated by 35 CGCMs, including models used in phase five of the Coupled Model Intercomparison Project (CMIP5). Among the 35 CGCMs, 14 models erroneously produce an upwelling dome in the eastern half of the basin whereas the observed Seychelles Dome is located in the southwestern tropical Indian Ocean. The annual mean Ekman pumping velocity in these models is found to be almost zero in the southern off-equatorial region. This result is inconsistent with observations, in which Ekman upwelling acts as the main cause of the Seychelles Dome. In the models reproducing an eastward-displaced dome, easterly biases are prominent along the equator in boreal summer and fall, which result in shallow thermocline biases along the Java and Sumatra coasts via Kelvin wave dynamics and a spurious upwelling dome in the region. Compared to the CMIP3 models, the CMIP5 models are even worse in simulating the dome longitudes.

  9. A preliminary report of the geohydrology of the Mississippi Salt-Dome Basin

    USGS Publications Warehouse

    Spiers, C.A.; Gandl, L.A.

    1980-01-01

    The U.S. Department of Energy is investigating the suitability of salt domes in the Mississippi salt-dome basin as repositories for storing radioactive wastes. The Department of Energy has requested that the U.S. Geological Survey describe the groundwater hydrology of the Mississippi salt-dome basin, giving special attention to direction and rate of movement of water. In this first part of a continuing investigation the data obtained from one year of extensive literature search and data compilation are summarized. The regional groundwater hydrology in the salt-dome basin is defined with respect to (1) groundwater flow, (2) facies changes, (3) geological structure, (4) recharge and discharge, (5) freshwater-saltwater relations, and (6) identification of localities where additional data are needed. From the 50 piercement-type salt domes in the Mississippi salt-dome basin three domes (Richton, Cypress Creek, and Lampton) were selected for more intensive study. To further evaluate the geohydrology of Richton, Lampton, and Cypress Creek domes as possible sites for storage of radioactive waste, an intensive geohydrologic study based on a comprehensive test drilling program near the domes is planned. (USGS)

  10. Seafloor doming driven by active mantle degassing offshore Naples (Italy)

    NASA Astrophysics Data System (ADS)

    Ventura, Guido; Passaro, Salvatore; Tamburrino, Stella; Vallefuoco, Mattia; Tassi, Franco; Vaselli, Orlando; Giannini, Luciano; Caliro, Stefano; Chiodini, Giovanni; Sacchi, Marco; Rizzo, Andrea

    2016-04-01

    Structures and processes associated with shallow water hydrothermal fluid discharges on continental shelves are poorly known. We report geomorphological, geophysical, and geochemical evidences of a 5.5 x 5.3 km seabed doming located 5 km offshore the Naples harbor (Italy). The dome lies between 100 and 170 m of water depth and it is 15-20 m higher than the surrounding seafloor. It is characterized by a hummocky morphology due to 280 sub-circular to elliptical mounds, about 660 cones, and 30 pockmarks. The mounds and pockmarks alignments follow those of the main structural discontinuity affecting the Gulf of Naples. The seafloor swelling and breaching require relatively low pressures (about 2-3 MPa), and the sub-seafloor structures, which consists of 'pagodas' affecting the present-day seabed, record the active upraise, pressurization, and release of magmatic fluids. The gas composition of the sampled submarine emissions is consistent with that of the emissions from the hydrothermal systems of Ischia, CampiFlegrei and Somma-Vesuvius active volcanoes, and CO2 has a magmatic/thermometamorphic origin. The 3He/4He ratios (1.66-1.96 Ra) are slightly lower than in the Somma-Vesuvius and Campi Flegrei volcanoes (~2.6-3.0 Ra) indicating the contamination of fluids originated from the same magmatic source by crustal-derived radiogenic 4He. All these evidences concur to hypothesize an extended magmatic reservoir beneath Naples and its offshore. Seabed doming, faulting, and hydrothermal discharges are manifestations of non-volcanic unrests potentially preluding submarine eruptions and/or hydrothermal explosions. We conclude that seabed deformations and hydrothermal discharge must be included in the coastal hazard studies.

  11. Winter sky brightness & cloud cover over Dome A

    NASA Astrophysics Data System (ADS)

    Yang, Yi; Moore, A. M.; Fu, J.; Ashley, M.; Cui, X.; Feng, L.; Gong, X.; Hu, Z.; Laurence, J.; LuongVan, D.; Riddle, R. L.; Shang, Z.; Sims, G.; Storey, J.; Tothill, N.; Travouillon, T.; Wang, L.; Yang, H.; Yang, J.; Zhou, X.; Zhu, Z.; Burton, M. G.

    2014-01-01

    At the summit of the Antarctic plateau, Dome A offers an intriguing location for future large scale optical astronomical Observatories. The Gattini DomeA project was created to measure the optical sky brightness and large area cloud cover of the winter-time sky above this high altitude Antarctic site. The wide field camera and multi-filter system was installed on the PLATO instrument module as part of the Chinese-led traverse to Dome A in January 2008. This automated wide field camera consists of an Apogee U4000 interline CCD coupled to a Nikon fish-eye lens enclosed in a heated container with glass window. The system contains a filter mechanism providing a suite of standard astronomical photometric filters (Bessell B, V, R), however, the absence of tracking systems, together with the ultra large field of view 85 degrees) and strong distortion have driven us to seek a unique way to build our data reduction pipeline. We present here the first measurements of sky brightness in the photometric B, V, and R band, cloud cover statistics measured during the 2009 winter season and an estimate of the transparency. In addition, we present example light curves for bright targets to emphasize the unprecedented observational window function available from this ground-based location. A ~0.2 magnitude agreement of our simultaneous test at Palomar Observatory with NSBM(National Sky Brightness Monitor), as well as an 0.04 magnitude photometric accuracy for typical 6th magnitude stars limited by the instrument design, indicating we obtained reasonable results based on our ~7mm effective aperture fish-eye lens.

  12. Phase evolution and magnetocaloric effect of melt-spun Mn{sub 3}Sn{sub 2-xM{sub x}} (M = B, C; x = 0-0.5) ribbons

    SciTech Connect

    Zhao, X. G.; Lee, E. H.; Hsieh, C. C.; Shih, C. W.; Chang, W. C.; Zhang, Z. D.

    2012-04-01

    The effects of B and C substitution for Sn on phase components, Curie temperature T{sub C}, and magnetocaloric effect of melt-spun Mn{sub 3}Sn{sub 2-x}M{sub x} (M B, C; x = 0-0.5) ribbons have been investigated. X-ray diffraction (XRD) results show that the main phase in the as-spun Mn{sub 3}Sn{sub 2-xM{sub x}} (M = B, C; x 0-0.5) ribbons is Mn{sub 3}Sn{sub 2} of Ni{sub 3}Sn{sub 2}-type (Pnma). Minor Mn{sub 2}B (when x {>=} 0.1) or Mn{sub 5}C{sub 2} (when x > 0.1) secondary phase is formed, and their amounts increase with increasing B and C concentration, respectively. The Curie temperature T{sub C} of these ribbons varies in the temperature range of 240-250 K. The peak values of the maximal magnetic entropy change, -{Delta}S{sub M}{sup max}, are about 13.6-18.3 mJ/cm{sup 3} K for B-substituted ribbons and 13.6-17.5 mJ/cm{sup 3} K for C-substituted ribbons, respectively, at a maximum applied field of 50 kOe. These values are about one fifth that of Gd (81.4 mJ/cm{sup 3} K). However, the relatively broader temperature range of the half maximum of {Delta}S{sub M} peak ({approx}100 K), low-cost and nontoxic elements still make Mn{sub 3}Sn{sub 2}-based ribbons the promising candidates for magnetic refrigeration applications close to room temperature.

  13. Domed Fresnel lens concentrator technology for space application

    NASA Technical Reports Server (NTRS)

    Piszczor, Michael F., Jr.; Oneill, Mark J.

    1989-01-01

    Over the past three years, NASA Lewis and Entech, Inc. have been investigating the use of high efficiency refractive photovoltaic concentrators for use in space. The design currently under investigation uses a square domed Fresnel lens to focus light on a GaAs concentrator cell. A prismatic cell cover, which directs light away from the front contacts and thus eliminates metalization losses, is applied to the top of the GaAs cell to further enhance array efficiency. The latest experimental results based on testing the GaAs cell/prism cover assembly at standard and operating conditions are presented.

  14. Near-automatic generation of lava dome DEMs from photos

    NASA Astrophysics Data System (ADS)

    James, M. R.; Varley, N.

    2012-04-01

    Acquiring accurate digital elevation models (DEMs) of growing lava domes is critical for hazard assessment. However, most techniques require expertise and time (e.g. photogrammetry) or expensive equipment (e.g. laser scanning and radar-based techniques). Here, we use a photo-based approach developed within the computer vision community that offers the potential for near-automatic DEM construction using a consumer-grade digital camera and freely available software. The technique is based on a combination of structure-from-motion and multi-view stereo algorithms (SfM-MVS) and can generate dense 3D point clouds (millions of points) from multiple photographs of a scene taken from different positions. Processing is carried out by automated 'reconstruction pipeline' software downloadable from the internet, e.g. http://blog.neonascent.net/archives/bundler-photogrammetry-package/. Such reconstructions are initally un-scaled and un-oriented so additional software (http://www.lancs.ac.uk/ staff/jamesm/software/sfm_georef.htm) has been developed to permit scaling or full georeferencing. Although this step requires the presence of some control points or knowledge of scale within the scene, it does not have the relatively strict image acquisition and control requirements of traditional photogrammetry. For accuracy and to allow error analysis, georeferencing observations are made within the image set, rather than requiring feature matching within the point cloud. Here we demonstrate the results of using the technique for deriving 3D models of the Volcán de Colima lava dome. 5 image sets have been collected by different people over a period of 12 months during overflights in a light aircraft. Although the resulting imagery is of variable quality for 3D reconstruction, useful data can be extracted from each set. Scaling and georeferencing is carried out using a combination of ortho-imagery (downloaded from Bing) and a few GPS points. Overall precisions are ~1 m and DEM qualities

  15. Field Survey of Cactus Crater Storage Facility (Runit Dome)

    SciTech Connect

    Douglas Miller, Terence Holland

    2008-10-31

    The US Department of Energy, Office of Health and Safety (DOE/HS-10), requested that National Security Technologies, LLC, Environmental Management directorate (NSTec/EM) perform a field survey of the Cactus Crater Storage Facility (Runit Dome), similar to past surveys conducted at their request. This field survey was conducted in conjunction with a Lawrence Livermore National Laboratory (LLNL) mission on Runit Island in the Enewetak Atoll in the Republic of the Marshall Islands (RMI). The survey was strictly a visual survey, backed up by digital photos and a written description of the current condition.

  16. Motivations for Imaging Spectroscopy atDomeC

    NASA Astrophysics Data System (ADS)

    Kelz, A.

    Antarctica offers unique conditions for ground-based observations, such as low sky background in the infrared, improved seeing, and low turbulence and scintillation noise. These properties are particularly beneficial to imaging, precision photometry, and infrared observations. It may be less clear if Antarctica offers equally compelling advantages for spectroscopy, in particular in the optical domain. However, scientific programmes that make use of imaging (or 3D) spectroscopy for selected follow-up studies of IR surveys, long-term monitoring of extended targets and resolved stellar population studies in crowded fields, also benefit from the site conditions at DomeC.

  17. Arthroscopic management of talar dome lesions using a transmalleolar approach.

    PubMed

    Grady, John; Hughes, David

    2006-01-01

    Surgical treatment of posteromedial talar dome lesions is frequently necessary for Berndt and Harty grade IV osteochondral defects and nondisplaced osteochondral fragments resistant to conservative modalities. When operative intervention is indicated, the approach and management can be complicated by the location and extent of the injury. The operative technique we advocate allows direct exposure of the lesion and minimizes damage to healthy articular cartilage and surrounding soft tissue. Use of a drill guide assists the surgeon in precisely placing a transmalleolar portal through the tibia for subchondral drilling of osteochondral defects when the lesions are inaccessible through traditional arthroscopic portals. PMID:16707640

  18. Accuracy of 3d Reconstruction in AN Illumination Dome

    NASA Astrophysics Data System (ADS)

    MacDonald, Lindsay; Toschi, Isabella; Nocerino, Erica; Hess, Mona; Remondino, Fabio; Robson, Stuart

    2016-06-01

    The accuracy of 3D surface reconstruction was compared from image sets of a Metric Test Object taken in an illumination dome by two methods: photometric stereo and improved structure-from-motion (SfM), using point cloud data from a 3D colour laser scanner as the reference. Metrics included pointwise height differences over the digital elevation model (DEM), and 3D Euclidean differences between corresponding points. The enhancement of spatial detail was investigated by blending high frequency detail from photometric normals, after a Poisson surface reconstruction, with low frequency detail from a DEM derived from SfM.

  19. Static analysis of a sonar dome rubber window

    NASA Technical Reports Server (NTRS)

    Lai, J. L.

    1978-01-01

    The application of NASTRAN (level 16.0.1) to the static analysis of a sonar dome rubber window (SDRW) was demonstrated. The assessment of the conventional model (neglecting the enclosed fluid) for the stress analysis of the SDRW was made by comparing its results to those based on a sophisticated model (including the enclosed fluid). The fluid was modeled with isoparametric linear hexahedron elements with approximate material properties whose shear modulus was much smaller than its bulk modulus. The effect of the chosen material property for the fluid is discussed.

  20. Origin of sulfate in barite and calcite cements in the Jebel Madar salt dome (Oman)

    NASA Astrophysics Data System (ADS)

    Vandeginste, V.; John, C. M.; Gilhooly, W. P.

    2012-12-01

    Jebel Madar is a 500-m high mountain rising in the desert at the Oman Foothills. The Jebel consists of Triassic to Cretaceous carbonate host rocks forming the carapace of a salt dome. Halokinesis caused major fracturing and faulting at Jebel Madar, and the resulting structures acted as the main pathways for fluids that generated diagenetic cements composed of both barite and calcite. The spatial distribution of calcite and barite occurrences shows that calcite is formed in large abundance along the three main faults, whereas barite is more concentrated along faults further away from the three main ones. The stable carbon and oxygen isotope composition of calcite and fluid inclusion data from both calcite and barite show a distinct evolution of the fluid with a highly saline component towards more mixing with meteoric water. This is in agreement with clumped isotopes data on calcite cements indicating an evolution towards lower temperatures, consistent with doming of the Jebel and greater input of lower-temperature descending meteoric fluids. Here, we present sulphur and oxygen isotopic data on barite that suggest a link between the barite formation and the Precambrian salt underlying Jebel Madar. The average δ34S measured in barite is 33‰ CDT (1σ = 5‰; n = 33), which falls at the lower end of the δ34S range reported for the Ara Group anhydrite. The average δ18O in the same barite samples is 23‰ VSMOW (1σ = 2‰; n = 33). Data from the barite will be compared with sulphur isotopes from the carbonate-associate sulfate in the calcite cements. The overall goal of our research is to gain a better insight in the formation process of barite and calcite in Jebel Madar and its link with salt tectonics. We would like to acknowledge the financial support of QCCSRC (funded jointly by Qatar Petroleum, Shell and the Qatar Science & Technology Park) and the GSA Laubach fund for this study.

  1. Electrochemical properties of melt spun Si-Cu-Ti-Zr-Ni alloy powders for the anode of Li-ion batteries

    NASA Astrophysics Data System (ADS)

    Bae, Seong Min; Sohn, Keun Yong; Park, Won-Wook

    2014-07-01

    The Si-Cu-Ti-Zr-Ni alloys of various compositions were prepared using arc-melting under an argon atmosphere, and the alloys were re-melted several times to ensure chemical homogeneity. The alloyed ingots were melt-spun to produce rapidly solidified ribbons under vacuum in order to prevent oxidation. Finely dispersed silicon particles 50-100 nm in diameter mainly consisting of Cu3Si, NiSi2 and TiSi2 phases were formed in the matrices. The alloy ribbons were then fragmented using ball-milling to produce powders. In order to evaluate the electrochemical properties of the alloys, anode electrodes were fabricated by mixing the active alloy materials (80 wt. %) with Ketjenblack® (2 wt. %) as a conductive material and polyamide imide (PAI, 8 wt. %) binder, and the mixtures were dissolved in N-methyl-2-pyrrolidinone (NMP) and SFG6 (10 wt. %). The anode performances of Si-Cu-Ti-Zr-Ni alloy cells were measured in the range 0.01-1.5 V (versus Li/Li+). The results showed that the Si68(Cu47Ti34Zr11Ni8)32 alloy ribbons had the highest specific discharge capacities, and the Si68(Cu40Ti40Zr10Ni10)32 alloy ribbons had relatively stable electrochemical properties and cycle performances due to the very fine microstructure including partially distributed amorphous phase. The matrix phases of the Si-Cu-Ti-Zr-Ni alloy ribbons effectively accommodated the change in Si particle volume during cycling.

  2. Volcanic synchronization of Dome Fuji and Dome C Antarctic deep ice cores over the past 216 kyr

    NASA Astrophysics Data System (ADS)

    Fujita, S.; Parrenin, F.; Severi, M.; Motoyama, H.; Wolff, E.

    2015-02-01

    Two deep ice cores, Dome Fuji (DF) and EPICA Dome C (EDC), drilled at remote dome summits in Antarctica, were synchronized to better understand their chronology. A total of 1401 volcanic tie points were identified covering the past 216 kyr. DFO2006, the chronology for the DF core characterized by strong constraining by the O2/N2 age markers, was compared with AICC2012, the chronology for 5 cores including the EDC core, and characterized by glaciological approaches combining ice flow modelling with various age markers. The age gaps between the two chronologies are within 2 kyr, except at Marine Isotope Stage (MIS) 5. DFO2006 gives ages older than AICC2012, with peak values of the gap of 4.5 and 3.1 kyr at MIS 5d and MIS 5b, respectively. Accordingly, ratios of duration DFO2006/AICC2012 are 85% at a period from the late stage of MIS 6 to MIS 5d and 114% at a period from MIS 5d to 5b. We then compared the DFO2006 with another chronology of the DF core, DFGT2006, characterized by glaciological approaches with weaker constraining by age markers. Features of the DFO2006/DFGT2006 age gaps are very similar to those of the DFO2006/AICC2012 age gaps. This fact lead us to hypothesize that a cause of the systematic DFO2006/AICC2012 age gaps at MIS 5 are associated with differences in the dating approaches. Besides, ages of speleothem records from China agreed well with DFO2006 at MIS 5c and 5d but not at MIS 5b. Thus, we hypothesize at least at MIS 5c and 5d, major sources of the gaps are systematic errors in surface mass balance estimation in the glaciological approach. Compatibility of the age markers should be carefully assessed in future.

  3. Regular Characterisation of Volcán de Colima's Dome Through Photo-based 3D Topographic and Thermal Surveys

    NASA Astrophysics Data System (ADS)

    James, M. R.; Moss-Davies, H.; Varley, N. R.

    2014-12-01

    Following an 18-month period of quiescence at Volcán de Colima - the longest seen since the beginning of the 1998 eruptive regime - the latest effusive period was heralded by the partial destruction of the 2007 lava dome by a significant explosion on 6th January, 2013. Subsequent small Vulcanian explosions, which have been more frequent than during the preceding 2007-2011 effusive period, have accompanied the extrusion of new lava. The effusion, which continues to the present day (July, 2014), has been monitored by monthly overflights in a light aircraft, allowing aerial surveys of the activity through the capture of oblique photographs and thermal infrared imagery. Using 'structure from motion' based photogrammetric analysis of the photographs has enabled metre-to-sub-metre resolution digital elevation models (DEMs) to be produced[1], from which volumetric and morphological changes to the dome can be assessed. Although extrusion of lava was observed on the 10th January, it was not until a subsequent survey on 25th February, in which a newly emplaced blocky dome was apparent in the excavated crater, that a reliable effusion rate could be calculated. The derived volumetric change, excluding losses due to minor explosions during this period, represents an effusion rate of <0.1 m3s-1, similar to that of that of the 2007-2011 effusion period (~0.02 m3s-1) and indicative of another period of slow growth. Continued growth of the dome led it to overflow the crater and form a lava flow, as detected in the survey of 21st March. The combination of regular oblique photography with a consumer camera and the use of modern 3D photo-based reconstruction software has enabled unprecedented numbers of DEMs to be produced for activity at Colima. We explore the potential of integrating the thermal data with the surface models for visualisation of areas of elevated activity. [1] James & Varley (2012) Identification of structural controls in an active lava dome with high resolution

  4. Photogrammetric monitoring of lava dome growth during the 2009 eruption of Redoubt Volcano

    NASA Astrophysics Data System (ADS)

    Diefenbach, Angela K.; Bull, Katharine F.; Wessels, Rick L.; McGimsey, Robert G.

    2013-06-01

    The 2009 eruption of Redoubt Volcano, Alaska, began with a phreatic explosion on 15 March followed by a series of at least 19 explosive events and growth and destruction of at least two, and likely three, lava domes between 22 March and 4 April. On 4 April explosive activity gave way to continuous lava effusion within the summit crater. We present an analysis of post-4 April lava dome growth using an oblique photogrammetry approach that provides a safe, rapid, and accurate means of measuring dome growth. Photogrammetric analyses of oblique digital images acquired during helicopter observation flights and fixed-wing volcanic gas surveys produced a series of digital elevation models (DEMs) of the lava dome from 16 April to 23 September. The DEMs were used to calculate estimates of volume and time-averaged extrusion rates and to quantify morphological changes during dome growth. Effusion rates ranged from a maximum of 35 m3 s- 1 during the initial two weeks to a low of 2.2 m3 s- 1 in early summer 2009. The average effusion rate from April to July was 9.5 m3 s- 1. Early, rapid dome growth was characterized by extrusion of blocky lava that spread laterally within the summit crater. In mid-to-late April the volume of the dome had reached 36 × 106 m3, roughly half of the total volume, and dome growth within the summit crater began to be limited by confining crater walls to the south, east, and west. Once the dome reached the steep, north-sloping gorge that breaches the crater, growth decreased to the south, but the dome continued to inflate and extend northward down the gorge. Effusion slowed during 16 April-1 May, but in early May the rate increased again. This rate increase was accompanied by a transition to exogenous dome growth. From mid-May to July the effusion rate consistently declined. The decrease is consistent with observations of reduced seismicity, gas emission, and thermal anomalies, as well as declining rates of geodetic deflation or inflation. These trends

  5. Measurement of air quality within storage domes in technical area 54, areas G and L

    SciTech Connect

    Anderson, E.

    1994-03-15

    The concentrations of volatile organic compounds (VOCs) and tritium inside of storage domes at TA-54 were measured to assess worker exposure and support the Area G site characterization, including the Radioactive Air Emissions Management (RAEM) program. Samples were collected at 2-3 locations within Domes 48, 49, and 153 on up to six days during the summer of 1994. Samples were collected to evaluate three scenarios: (1) normal working activities with the domes open; (2) after domes were closed overnight; and (3) after domes were closed for three days. Eight-hour integrated samples were collected and analyzed in Radian`s Austin laboratories. Tritium activities from 17.1 to 69,900 pCi/m{sup 3} were measured. About two dozen individual VOCs were identified in each sample, but most of the concentration levels were very low (e.g.; < 1 to 10 ppbv). The highest concentrations measured were bromomethane (56.5 ppbv), 1, 1,1-trichloroethane (75.4 ppbv), propane (958 ppbv), methylene chloride (1,450 ppbv), and toluene (22.8). The measured VOC concentrations were well below the action levels developed by the New Mexico Environment Department and the measured tritium concentrations were well below the DOE`s derived air concentration (DAC). The variability in concentration within a dome during a single sampling episode was small. The concentrations were about an order of magnitude (i.e., 10x) higher after the domes had been closed overnight compared with the domes when open. Closing the domes over the weekend did not result in significantly higher concentrations (e.g.; > 20%) than when the domes were closed only overnight. The data were used to generate estimated annual dome emission rates of 0.3 Ci/yr of tritium and less than 100 lbs/yr of VOCs. The measured VOC concentrations were collected during the warmest months of the year and therefore should represent worst-case air impacts.

  6. Unzen Dome Dacite Density: Influence On Fragmentation Behaviour

    NASA Astrophysics Data System (ADS)

    Küppers, U.; Spieler, O.; Dingwell, D. B.

    Preliminary experimental investigations of the fragmentation of dome lava from Un- zen volcano, Kyushu Island (Japan), have indicated that fragmentation is influenced by density. Two field campaigns (2000 and 2001) have been conducted to obtain extensive density information on the pyroclastic flow deposits of the 1990 to 1995 eruption. This allows the characterisation of the pre-collapse dome density. Such density data enable us to evaluate the effect and influence of transport processes on the density distribution inside the deposits. Experiments have been performed to determine the fragmentation threshold of hot, pressurised rock cylinders (60 x 26 mm) due to rapid decompression. The cylinders are pressurised using argon gas. The fragmentation bomb simulates the conditions for volcanic fragmentation induced by rapid decompression. At 850 C dense dacite with an open porosity of 3.76 % requires an initial pressure difference of 22.5 MPa to overcome the threshold. The threshold value decreases steeply with increasing porosity. At porosities greater than 12 % the rate of decrease of threshold value is reduced. The results presented here correlate with those obtained from Merapi, Montserrat and Mt. St. Helens (Spieler, 2001). Natural pyroclastics and pyroclastics generated experimentally have been compared using a laser particle size analyzer to correlate our experimental trends with data from natural products.

  7. The AST3 project: Antarctic Survey Telescopes for Dome A

    NASA Astrophysics Data System (ADS)

    Yuan, Xiangyan; Cui, Xiangqun; Gu, Bozhong; Yang, Shihai; Du, Fujia; Li, Xiaoyan; Wang, Daxing; Li, Xinnan; Gong, Xuefei; Wen, Haikun; Li, Zhengyang; Lu, Haiping; Xu, Lingzhe; Zhang, Ru; Zhang, Yi; Wang, Lifan; Shang, Zhaohui; Hu, Yi; Ma, Bin; Liu, Qiang; Wei, Peng

    2014-07-01

    The AST3 project consists of three large field of view survey telescopes with 680mm primary mirror, mainly for observations of supernovas and extrasolar planets searching from Antarctic Dome A where is very likely to be the best astronomical site on earth for astronomical observations from optical wavelength to thermal infrared and beyond, according to the four years site testing works by CCAA, UNSW and PRIC. The first AST3 was mounted on Dome A in Jan. 2012 and automatically run from March to May 2012. Based on the onsite winterization performance of the first AST3, some improvements such as the usage of high resolution encoders, defrosting method, better thermal control and easier onsite assembly et al were done for the second one. The winterization observation of AST3-2 in Mohe was carried on from Nov. 2013 to Apr. 2014, where is the most northern and coldest part of China with the lowest temperature around -50°. The technical modifications and testing observation results will be given in this paper. The third AST3 will be optimized from optical to thermal infrared aiming diffraction limited imaging with K band. Thus the whole AST3 project will be a good test bench for the development of future larger aperture optical/infrared Antarctic telescopes such as the proposed 2.5m Kunlun Dark Universe Survey Telescope project.

  8. Characterization of Atmospheric Ekman Spirals at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Rysman, Jean-François; Lahellec, Alain; Vignon, Etienne; Genthon, Christophe; Verrier, Sébastien

    2016-08-01

    We use wind speed and temperature measurements taken along a 45-m meteorological tower located at Dome C, Antarctica (75.06°S, 123.19°E) to highlight and characterize the Ekman spiral. Firstly, temperature records reveal that the atmospheric boundary layer at Dome C is stable during winter and summer nights (i.e., >85 % of the time). The wind vector, in both speed and direction, also shows a strong dependence with elevation. An Ekman model was then fitted to the measurements. Results show that the wind vector follows the Ekman spiral structure for more than 20 % of the year (2009). Most Ekman spirals have been detected during summer nights, that is, when the boundary layer is slightly stratified. During these episodes, the boundary-layer height ranged from 25 to 100 m, the eddy viscosity from 0.004 to 0.06 m^2 s^{-1}, and the Richardson number from zero to 1.6.

  9. Performance limits of planar phased array with dome lens

    NASA Astrophysics Data System (ADS)

    Geren, W. P.; Taylor, Michael

    1998-10-01

    Communication systems based on low-earth-orbit (LEO) satellites have generated a requirement for high-performance phased array antennas with exceptional gain, sidelobe levels, and axial ratio over broad scan angles and 360 degree azimuth coverage. One approach to mitigating the effects of scan dependence is to cover the planar array with a hemispherical lens, or dome, which implements passive or active phase correction of the scanned beam. The phase correction over the dome surface may be represented as the function (Delta) (Phi) ((theta) , (phi) ), with (theta) and (phi) the polar and azimuth angles in a coordinate system having z-axis normal to the array. The purpose of this study was to determine the performance improvement achievable with such an ideal lens. Three cases were considered: a conventional lens with fixed optimum phase correction, an active lens with scan-dependent phase correction a function of polar angle only, and an active lens with phase correction a function of polar and azimuthal angles. In all cases, the planar array distribution had a fixed radial Taylor amplitude distribution and a phase taper consisting of a linear beam-pointing term and a non-linear focusing term.

  10. Exceptional astronomical seeing conditions above Dome C in Antarctica.

    PubMed

    Lawrence, Jon S; Ashley, Michael C B; Tokovinin, Andrei; Travouillon, Tony

    2004-09-16

    One of the most important considerations when planning the next generation of ground-based optical astronomical telescopes is to choose a site that has excellent 'seeing'--the jitter in the apparent position of a star that is caused by light bending as it passes through regions of differing refractive index in the Earth's atmosphere. The best mid-latitude sites have a median seeing ranging from 0.5 to 1.0 arcsec (refs 1-5). Sites on the Antarctic plateau have unique atmospheric properties that make them worth investigating as potential observatory locations. Previous testing at the US Amundsen-Scott South Pole Station has, however, demonstrated poor seeing, averaging 1.8 arcsec (refs 6, 7). Here we report observations of the wintertime seeing from Dome C (ref. 8), a high point on the Antarctic plateau at a latitude of 75 degrees S. The results are remarkable: the median seeing is 0.27 arcsec, and below 0.15 arcsec 25 per cent of the time. A telescope placed at Dome C would compete with one that is 2 to 3 times larger at the best mid-latitude observatories, and an interferometer based at this site could work on projects that would otherwise require a space mission. PMID:15372024

  11. PHOTOMETRY OF VARIABLE STARS FROM DOME A, ANTARCTICA

    SciTech Connect

    Wang Lingzhi; Macri, Lucas M.; Krisciunas, Kevin; Wang Lifan; Ashley, Michael C. B.; Lawrence, Jon S.; Luong-Van, Daniel; Storey, John W. V.; Cui Xiangqun; Gong Xuefei; Yuan Xiangyan; Feng Longlong; Yang Ji; Zhu Zhenxi; Liu Qiang; Zhou Xu; Pennypacker, Carl R.; Shang Zhaohui; Yang Huigen; York, Donald G.

    2011-11-15

    Dome A on the Antarctic plateau is likely one of the best observing sites on Earth thanks to the excellent atmospheric conditions present at the site during the long polar winter night. We present high-cadence time-series aperture photometry of 10,000 stars with i < 14.5 mag located in a 23 deg{sup 2} region centered on the south celestial pole. The photometry was obtained with one of the CSTAR telescopes during 128 days of the 2008 Antarctic winter. We used this photometric data set to derive site statistics for Dome A and to search for variable stars. Thanks to the nearly uninterrupted synoptic coverage, we found six times as many variables as previous surveys with similar magnitude limits. We detected 157 variable stars, of which 55% were unclassified, 27% were likely binaries, and 17% were likely pulsating stars. The latter category includes {delta} Scuti, {gamma} Doradus, and RR Lyrae variables. One variable may be a transiting exoplanet.

  12. Unfinished business: the rebirth of the ALPO Lunar Dome Survey

    NASA Astrophysics Data System (ADS)

    Huddleston, Marvin W.

    2004-05-01

    The ALPO board of directors approved the revival of the Lunar Dome Survey during their annual board meeting in the summer of 2003. The initial LDS program was conceived by Harry Jamieson in the early 1960's and headed by him when the British Astronomical Assn. (BAA) was invited to join the program, which they did. The joint effort between the ALPO and BAA lunar sections lasted for approximately 14 years, ending officially around 1976 due to a decline in interest. The program was again revived in 1987 under the direction of Jim Phillips and lasted until the mid-1990's. All told, this program has been one of the longest running programs in the history of the Lunar Section of ALPO. The revived program will concentrate on cleaning up the existing catalog, classification and confirmation of the objects contained therein, and analysis of the database created in the process. It is hoped that, as in the past, much of the newly revived Lunar Dome Survey will be an international effort.

  13. Superior reinforcement in melt-spun polyethylene/multiwalled carbon nanotube fiber through formation of a shish-kebab structure.

    PubMed

    Mai, Fang; Wang, Ke; Yao, Meijun; Deng, Hua; Chen, Feng; Fu, Qiang

    2010-08-26

    The formation of a shish kebab (SK) structure, where carbon nanotubes (CNTs) serve as shish and polymer lamellae serve as kebab, is particularly interesting and provides a novel way to enhance the polymer-CNT interface. A fine SK structure is achieved through melt spinning. High density polyethylene and pristine CNTs were first compounded in an extruder. The compound was then spun into fibers with different draw ratios with the aid of a capillary rheometer. The crystalline structure and mechanical behavior were characterized by scanning electron microscopy, differential scanning calorimetry, two-dimensional wide-angle X-ray scattering, polarized Raman spectroscopy, and tensile testing. An increase in tensile strength as high as 3 times has been achieved in the fiber. The formation of SKs is considered as the main mechanism responsible for the enhanced interfacial interaction and excellent tensile property. PMID:20677770

  14. Large magnetoresistance in highly textured Mn44.7Ni43.5Sn11.8 melt spun ribbons

    NASA Astrophysics Data System (ADS)

    Chen, Fenghua; Huang, Qingxue; Jiang, Zhengyi; Xuan, Haicheng; Zhang, Mingang; Xu, Xiaohong; Zhao, Jingwei

    2016-05-01

    Highly textured Heusler alloy Mn44.7Ni43.5Sn11.8 ribbons were prepared by melt spinning. The magnetoresistance (MR) properties were evaluated by the magnetic field perpendicular to the ribbon surface with the field up to 30 kOe. A large MR (about 25%) with a lower magnetic field (10 kOe) was obtained at 276 K. Due to the rapid solidification. The ribbons with a specific texture can get a large MR twice than polycrystalline alloys at the same magnetic field. The highly textured Mn–Ni–Sn melt spun ribbons may be broadly applied in magnetic memory and as temperature and magnetic sensors as well.

  15. Effects of annealing process on magnetic properties and structures of Nd-Pr-Ce-Fe-B melt-spun powders

    NASA Astrophysics Data System (ADS)

    Pei, Kun; Lin, Min; Yan, Aru; Zhang, Xing

    2016-05-01

    The effects of annealing process on magnetic properties and structures of Nd-Pr-Ce-Fe-B melt-spun powders have been investigated. The magnetic properties improve a lot when the annealing temperature is 590-650 °C and the annealing time exceeds 1 min. The magnetic properties is stable when the annealing time is 590-650 °C. The powders contains obvious grains when the annealing time is only 1 min, while the grains grow up obviously, leading to the decrease of Br and (BH)max, when the annealing time is more than 9 min. The Hcj changes little for different annealing time. The cooling rate also affects the magnetic properties of powders with different Ce-content. Faster cooling rate is favorable to improve magnetic properties with low Ce-content powders, while high Ce-content powders need slower cooling rate.

  16. E-Spun Composite Fibers of Collagen and Dragline Silk Protein: Fiber Mechanics, Biocompatibility, and Application in Stem Cell Differentiation

    PubMed Central

    2015-01-01

    Biocomposite matrices with high mechanical strength, high stability, and the ability to direct matrix-specific stem cell differentiation are essential for the reconstruction of lesioned tissues in tissue engineering and cell therapeutics. Toward this end, we used the electrospinning technique to fabricate well-aligned composite fibers from collagen and spider dragline silk protein, obtained from the milk of transgenic goats, mimicking the native extracellular matrix (ECM) on a similar scale. Collagen and the dragline silk proteins were found to mix homogeneously at all ratios in the electrospun (E-spun) fibers. As a result, the ultimate tensile strength and elasticity of the fibers increased monotonically with silk percentage, whereas the stretchability was slightly reduced. Strikingly, we found that the incorporation of silk proteins to collagen dramatically increased the matrix stability against excessive fiber swelling and shape deformation in cell culture medium. When human decidua parietalis placental stem cells (hdpPSCs) were seeded on the collagen–silk matrices, the matrices were found to support cell proliferation at a similar rate as that of the pure collagen matrix, but they provided cell adhesion with reduced strengths and induced cell polarization at varied levels. Matrices containing 15 and 30 wt % silk in collagen (CS15, CS30) were found to induce a level of neural differentiation comparable to that of pure collagen. In particular, CS15 matrix induced the highest extent of cell polarization and promoted the development of extended 1D neural filaments strictly in-line with the aligned fibers. Taking the increased mechanical strength and fiber stability into consideration, CS15 and CS30 E-spun fibers offer better alternatives to pure collagen fibers as scaffolds that can be potentially utilized in neural tissue repair and the development of future nanobiodevices. PMID:25405355

  17. E-spun composite fibers of collagen and dragline silk protein: fiber mechanics, biocompatibility, and application in stem cell differentiation.

    PubMed

    Zhu, Bofan; Li, Wen; Lewis, Randolph V; Segre, Carlo U; Wang, Rong

    2015-01-12

    Biocomposite matrices with high mechanical strength, high stability, and the ability to direct matrix-specific stem cell differentiation are essential for the reconstruction of lesioned tissues in tissue engineering and cell therapeutics. Toward this end, we used the electrospinning technique to fabricate well-aligned composite fibers from collagen and spider dragline silk protein, obtained from the milk of transgenic goats, mimicking the native extracellular matrix (ECM) on a similar scale. Collagen and the dragline silk proteins were found to mix homogeneously at all ratios in the electrospun (E-spun) fibers. As a result, the ultimate tensile strength and elasticity of the fibers increased monotonically with silk percentage, whereas the stretchability was slightly reduced. Strikingly, we found that the incorporation of silk proteins to collagen dramatically increased the matrix stability against excessive fiber swelling and shape deformation in cell culture medium. When human decidua parietalis placental stem cells (hdpPSCs) were seeded on the collagen-silk matrices, the matrices were found to support cell proliferation at a similar rate as that of the pure collagen matrix, but they provided cell adhesion with reduced strengths and induced cell polarization at varied levels. Matrices containing 15 and 30 wt % silk in collagen (CS15, CS30) were found to induce a level of neural differentiation comparable to that of pure collagen. In particular, CS15 matrix induced the highest extent of cell polarization and promoted the development of extended 1D neural filaments strictly in-line with the aligned fibers. Taking the increased mechanical strength and fiber stability into consideration, CS15 and CS30 E-spun fibers offer better alternatives to pure collagen fibers as scaffolds that can be potentially utilized in neural tissue repair and the development of future nanobiodevices. PMID:25405355

  18. Teapot Dome: Site Characterization of a CO2- Enhanced Oil Recovery Site in Eastern Wyoming

    SciTech Connect

    Friedmann, S J; Stamp, V

    2005-11-01

    Naval Petroleum Reserve No. 3 (NPR-3), better known as the Teapot Dome oil field, is the last U.S. federally-owned and -operated oil field. This provides a unique opportunity for experiments to provide scientific and technical insight into CO{sub 2}-enhanced oil recovery (EOR) and other topics involving subsurface fluid behavior. Towards that end, a combination of federal, academic, and industrial support has produced outstanding characterizations of important oil- and brine-bearing reservoirs there. This effort provides an unparalleled opportunity for industry and others to use the site. Data sets include geological, geophysical, geochemical, geomechanical, and operational data over a wide range of geological boundary conditions. Importantly, these data, many in digital form, are available in the public domain due to NPR-3's federal status. Many institutions are already using portions of the Teapot Dome data set as the basis for a variety of geoscience, modeling, and other research efforts. Fifteen units, 9 oil-bearing and 6 brine-bearing, have been studied to varying degrees. Over 1200 wells in the field are active or accessible, and over 400 of these penetrate 11 formations located below the depth that corresponds to the supercritical point for CO{sub 2}. Studies include siliciclastic and carbonate reservoirs; shale, carbonate, and anhydrite cap rocks; fractured and unfractured units; and over-pressured and under-pressured zones. Geophysical data include 3D seismic and vertical seismic profiles. Reservoir data include stratigraphic, sedimentological, petrologic, petrographic, porosity, and permeability data. These have served as the basis for preliminary 3D flow simulations. Geomechanical data include fractures (natural and drilling induced), in-situ stress determination, pressure, and production history. Geochemical data include soil gas, noble gas, organic, and other measures. The conditions of these reservoirs directly or indirectly represent many reservoirs

  19. Rift-related volcanism and karst geohydrology of the southern Ozark Dome

    USGS Publications Warehouse

    Harrison, Richard W.; Weary, David J.; Orndorff, Randall C.; Repetski, John E.; Pierce, Herbert A.; Lowell, Gary R.

    2010-01-01

    This field trip examines the geology and geohydrology of a dissected part of the Salem Plateau in the Ozark Plateaus province of south-central Missouri. Rocks exposed in this area include karstified, flat-lying, lower Paleozoic carbonate platform rocks deposited on Mesoproterozoic basement. The latter is exposed as an uplift located about 40 mi southwest of the St. Francois Mountains and form the core of the Ozark dome. On day 1, participants will examine and explore major karst features developed in Paleozoic carbonate strata on the Current River; this will include Devil's Well and Round Spring Cavern as well as Montauk, Round, Alley, and Big Springs. The average discharge of the latter is 276 × 106 gpd and is rated in the top 20 springs in the world. Another, Alley Spring, is equally spectacular with an average discharge of 81 × 106 gpd. Both are major contributors to the Current and Eleven Point River drainage system which includes about 50 Mesoproterozoic volcanic knobs and two granite outcrops. These knobs are mainly caldera-erupted ignimbrites with a total thickness of 7–8 km. They are overlain by post-collapse lavas and intruded by domes dated at 1470 Ma. Volcaniclastic sediment and air-fall lapilli tuff are widely distributed along this synvolcanic unconformity. On day 2, the group will examine the most important volcanic features and the southernmost granite exposure in Missouri. The trip concludes with a discussion of the Missouri Gravity Low, the Eminence caldera, and the volcanic history of southern Missouri as well as a discussion of geologic controls on regional groundwater flow through this part of the Ozark aquifer.

  20. Mechanical and spatial determinants of cytoskeletal geodesic dome formation in cardiac fibroblasts.

    PubMed

    Entcheva, Emilia; Bien, Harold

    2009-02-01

    This study tests the hypothesis that the cell cytoskeletal (CSK) network can rearrange from geodesic dome type structures to stress fibers in response to microenvironmental cues. The CSK geodesic domes are highly organized actin microarchitectures within the cell, consisting of ordered polygonal elements. We studied primary neonatal rat cardiac fibroblasts. The cues used to trigger the interconversion between the two CSK architectures (geodesic domes and stress fibers) included factors affecting spatial order and the degree of CSK tension in the cells. Microfabricated three-dimensional substrates with micrometre sized grooves and peaks were used to alter the spatial order of cell growth in culture. CSK tension was modified by 2,3-butanedione 2-monoxime (BDM), cytochalasin D and the hyphae of Candida albicans. CSK geodesic domes occurred spontaneously in about 20% of the neonatal rat cardiac fibroblasts used in this study. Microfabricated structured surfaces produced anisotropy in the cell CSK and effectively converted geodesic domes into stress fibers in a dose-dependent manner (dependence on the period of the features). Affectors of actin structure, inhibitors of CSK tension and cell motility, e.g. BDM, cytochalasin D and the hyphae of C. albicans, suppressed or eliminated the geodesic domes. Our data suggest that the geodesic domes, similar to actin stress fibers, require maintenance of CSK integrity and tension. However, microenvironments that promote structural anisotropy in tensed cells cause the transformation of the geodesic domes into stress fibers, consistent with topographic cell guidance and some previous CSK model predictions. PMID:20023805

  1. Mechanical and spatial determinants of cytoskeletal geodesic dome formation in cardiac fibroblasts

    PubMed Central

    Bien, Harold

    2015-01-01

    This study tests the hypothesis that the cell cytoskeletal (CSK) network can rearrange from geodesic dome type structures to stress fibers in response to microenvironmental cues. The CSK geodesic domes are highly organized actin microarchitectures within the cell, consisting of ordered polygonal elements. We studied primary neonatal rat cardiac fibroblasts. The cues used to trigger the interconversion between the two CSK architectures (geodesic domes and stress fibers) included factors affecting spatial order and the degree of CSK tension in the cells. Microfabricated three-dimensional substrates with micrometre sized grooves and peaks were used to alter the spatial order of cell growth in culture. CSK tension was modified by 2,3-butanedione 2-monoxime (BDM), cytochalasin D and the hyphae of Candida albicans. CSK geodesic domes occurred spontaneously in about 20% of the neonatal rat cardiac fibroblasts used in this study. Microfabricated structured surfaces produced anisotropy in the cell CSK and effectively converted geodesic domes into stress fibers in a dose-dependent manner (dependence on the period of the features). Affectors of actin structure, inhibitors of CSK tension and cell motility, e.g. BDM, cytochalasin D and the hyphae of C. albicans, suppressed or eliminated the geodesic domes. Our data suggest that the geodesic domes, similar to actin stress fibers, require maintenance of CSK integrity and tension. However, microenvironments that promote structural anisotropy in tensed cells cause the transformation of the geodesic domes into stress fibers, consistent with topographic cell guidance and some previous CSK model predictions. PMID:20023805

  2. The ongoing dome emplacement and destruction cyclic process at Popocatépetl volcano, Central Mexico

    NASA Astrophysics Data System (ADS)

    Gómez-Vazquez, Angel; De la Cruz-Reyna, Servando; Mendoza-Rosas, Ana Teresa

    2016-09-01

    The ongoing eruptive activity of Popocatépetl volcano has been characterized by emplacement and subsequent destruction of a succession of lava domes. Between the onset of the current eruption in 1994 and the time of this submission, 38 episodes of lava dome formation and removal have been identified. Each dome has showed particular features related to the magma extrusion process. Among other manifestations, dome-emplacement events have been usually accompanied by relatively low-intensity, protracted explosions referred to as exhalations. After variable times of residence, emplacements have ended in partial or total destruction of the domes by strong vulcanian explosions that produced sizeable ash plumes, with most of them also ejecting incandescent debris onto the volcano flanks. Here, we present a detailed account for the observed activity related to the domes' growth and destruction, related seismic monitoring signals, and morphological features of the domes based on 19 years of visual observations and image analysis. We then discuss a model for the process of dome growth and destruction and its hazard implications.

  3. Sensitivity of storage field performance to geologic and cavern design parameters in salt domes.

    SciTech Connect

    Ehgartner, Brian L.; Park, Byoung Yoon; Herrick, Courtney Grant

    2010-06-01

    A sensitivity study was performed utilizing a three dimensional finite element model to assess allowable cavern field sizes in strategic petroleum reserve salt domes. A potential exists for tensile fracturing and dilatancy damage to salt that can compromise the integrity of a cavern field in situations where high extraction ratios exist. The effects of salt creep rate, depth of salt dome top, dome size, caprock thickness, elastic moduli of caprock and surrounding rock, lateral stress ratio of surrounding rock, cavern size, depth of cavern, and number of caverns are examined numerically. As a result, a correlation table between the parameters and the impact on the performance of a storage field was established. In general, slower salt creep rates, deeper depth of salt dome top, larger elastic moduli of caprock and surrounding rock, and a smaller radius of cavern are better for structural performance of the salt dome.

  4. Fabrication of conformal ZnS domes by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Goela, Jitendra S.; Askinazi, Joel

    1999-07-01

    Aspheric shape ZnS domes were fabricated by a scalable and cost-effective chemical vapor deposition (CVD) process to demonstrate the feasibility of producing aerodynamic domes that conform to the shape of the missile body. These domes provide enhanced performance by substantially reducing the missile drag, although they also present issues of CVD deposition, optical fabrication to the required figure and finish, particularly the inside surface, and metrology. Domes were fabricated on 'male' mandrels in a CVD chamber to produce net-shape or precision replicated inside surface and then diamond turned to produce surfaces with figure of a fraction of a wave and finish of 180 angstrom RMS. Important issues involved in near-net-shaping and precision replication of ZnS domes are discussed and data on mandrel and release coating materials, degree of replication achieved and mandrel durability are presented.

  5. Sensitivity of storage field performance to geologic and cavern design parameters in salt domes.

    SciTech Connect

    Ehgartner, Brian L.; Park, Byoung Yoon

    2009-03-01

    A sensitivity study was performed utilizing a three dimensional finite element model to assess allowable cavern field sizes for strategic petroleum reserve salt domes. A potential exists for tensile fracturing and dilatancy damage to salt that can compromise the integrity of a cavern field in situations where high extraction ratios exist. The effects of salt creep rate, depth of salt dome top, dome size, caprock thickness, elastic moduli of caprock and surrounding rock, lateral stress ratio of surrounding rock, cavern size, depth of cavern, and number of caverns are examined numerically. As a result, a correlation table between the parameters and the impact on the performance of storage field was established. In general, slower salt creep rates, deeper depth of salt dome top, larger elastic moduli of caprock and surrounding rock, and a smaller radius of cavern are better for structural performance of the salt dome.

  6. A structural outline of the Yenkahe volcanic resurgent dome (Tanna Island, Vanuatu Arc, South Pacific)

    NASA Astrophysics Data System (ADS)

    Merle, O.; Brothelande, E.; Lénat, J.-F.; Bachèlery, P.; Garaébiti, E.

    2013-12-01

    A structural study has been conducted on the resurgent Yenkahe dome (5 km long by 3 km wide) located in the heart of the Siwi caldera of Tanna Island (Vanuatu arc, south Pacific). This spectacular resurgent dome hosts a small caldera and a very active strombolian cinder cone - the Yasur volcano - in the west and exhibits an intriguing graben in its central part. Detailed mapping and structural observations make it possible to unravel the volcano-tectonic history of the dome. It is shown that, following the early formation of a resurgent dome in the west, a complex collapse (caldera plus graben) occurred and this was associated with the recent uplift of the eastern part of the present dome. Eastward migration of the underlying magma related to regional tectonics is proposed to explain this evolution.

  7. Strategic Petroleum Reserve (SPR) geological site characterization report, Big Hill Salt Dome

    SciTech Connect

    Hart, R.J.; Ortiz, T.S.; Magorian, T.R.

    1981-09-01

    Geological and geophysical analyses of the Big Hill Salt Dome were performed to determine the suitability of this site for use in the Strategic Petroleum Reserve (SPR). Development of 140 million barrels (MMB) of storage capacity in the Big Hill Salt Dome is planned as part of the SPR expansion to achieve 750 MMB of storage capacity. Objectives of the study were to: (1) Acquire, evaluate, and interpret existing data pertinent to geological characterization of the Big Hill Dome; (2) Characterize the surface and near-surface geology and hydrology; (3) Characterize the geology and hydrology of the overlying cap rock; (4) Define the geometry and geology of the dome; (5) Determine the feasibility of locating and constructing 14 10-MMB storage caverns in the south portion of the dome; and (6) Assess the effects of natural hazards on the SPR site. Recommendations are included. (DMC)

  8. Venusian pancake domes: Insights from terrestrial voluminous silicic lavas and thermal modeling

    NASA Technical Reports Server (NTRS)

    Manley, Curtis R.

    1993-01-01

    The so-called 'pancake' domes, and several other volcanoes on Venus, appear to represent large extrusions of silicic lava. Similar voluminous rhyolite lava flows, often associated with mantle plumes, are known on Earth. Venus' high ambient temperature, and insulation by the dome's brecciated carapace, both act to prolong cooling of a dome's interior, allowing for episodic lava input over an extended period of time. Field relations and aspect ratios of terrestrial voluminous rhyolite lavas imply continuous, non-episodic growth, reflecting tapping of a large volume of dry, anatectic silicic magma. Petrogenetically, the venusian domes may be analogous to chains of small domes on Earth, which represent 'leakage' of evolved material from magma bodies fractionating from much more mafic liquids.

  9. Citronelle Dome: A giant opportunity for multizone carbon storage and enhanced oil recovery in the Mississippi Interior Salt Basin of Alabama

    USGS Publications Warehouse

    Esposito, R.A.; Pashin, J.C.; Walsh, P.M.

    2008-01-01

    The Citronelle Dome is a giant, salt-cored anticline in the eastern Mississippi Interior Salt Basin of southern Alabama that is located near several large-scale, stationary, carbon-emitting sources in the greater Mobile area. The dome forms an elliptical, four-way structural closure containing opportunities for CO2-enhanced oil recovery (CO2-EOR) and large-capacity saline reservoir CO2 sequestration. The Citronelle oil field, located on the crest of the dome, has produced more than 169 million bbl of 42-46?? API gravity oil from sandstone bodies in the Lower Cretaceous Rodessa Formation. The top seal for the oil accumulation is a thick succession of shale and anhydrite, and the reservoir is underfilled such that oil-water contacts are typically elevated 30-60 m (100-200 ft) above the structural spill point. Approximately 31-34% of the original oil in place has been recovered by primary and secondary methods, and CO2-EOR has the potential to increase reserves by up to 20%. Structural contour maps of the dome demonstrate that the area of structural closure increases upward in section. Sandstone units providing prospective carbon sinks include the Massive and Pilot sands of the lower Tuscaloosa Group, as well as several sandstone units in the upper Tuscaloosa Group and the Eutaw Formation. Many of these sandstone units are characterized by high porosity and permeability with low heterogeneity. The Tuscaloosa-Eutaw interval is capped by up to 610 m (2000 ft) of chalk and marine shale that are proven reservoir seals in nearby oil fields. Therefore, the Citronelle Dome can be considered a major geologic sink where CO2 can be safely stored while realizing the economic benefits associated with CO2-EOR. Copyright ?? 2008. The American Association of Petroleum Geologists/Division of Environmental Geosciences. All rights reserved.

  10. Long-term landscape evolution in the Hangay Dome, Mongolia

    NASA Astrophysics Data System (ADS)

    McDannell, K. T.; Ancuta, L. D.; Smith, S. G.; Idleman, B. D.; Wegmann, K. W.; Zeitler, P. K.

    2013-12-01

    The Hangay Dome in central Mongolia is an example of high-elevation (>3000 m), low-relief topography in a continental interior between the thick Siberian craton to the north and the active Himalaya deformation belt to the far south. Detrital and granitic bedrock apatite (U-Th)/He samples yield ages of ~85-200 Ma and ~95-120 Ma, respectively. These low-temperature data in conjunction with K-feldspar 40Ar/39Ar ages of ~200-225 Ma, raise questions about when this preserved, epeirogenic landscape was uplifted and how it has responded to minimal exhumation since the Mesozoic. Alpine cirques and intact moraine deposits are indicative of a more recent, climate-driven erosional signal in the higher elevation regions of the Hangay. Pecube modeling indicates that a recent, regional uplift signal produces younger, Early-Mid Cenozoic cooling ages in lower elevations of the Selenga River drainage basin to the north of the Hangay Dome. Modeled low exhumation rates of 0.038 mm/yr over 122 Ma generate cooling ages in agreement with preliminary geomorphic and geochronologic results. Basalt total fusion 40Ar/39Ar ages constrain the earliest surface exposure of the landscape to ~30 Ma in the Hangay, with flows as young as ~5 Ka present in a few areas. Geomorphic observations coupled with age-constrained basalt stratigraphy allow us to calculate minimum incision rates in the eastern Hangay for the Miocene and Late Pliocene-Holocene of 0.032 mm/yr and 0.039 mm/yr, respectively. In addition, basalt-bedrock contact mapping in one area places a ~10 Ma old basal flow erupted onto an undulated bedrock surface, suggesting the existence of topography at the time of eruption. Volumetric analysis reveals that rock removed in the past ~6 Ma (uppermost basalt flow age) yields a net erosion rate of 0.037 mm/yr. This rate is also comparable to our 10Be basin-averaged erosion rates from samples collected in adjacent drainages. In contrast to previous inferences that central Mongolia has undergone

  11. The Hangay Dome, central Mongolia: A relict Mesozoic landscape

    NASA Astrophysics Data System (ADS)

    McDannell, K. T.; Zeitler, P. K.; Ancuta, L. D.; Idleman, B. D.; Boulton, S. L.; Wegmann, K. W.

    2014-12-01

    The Hangay Dome is a broad upland in central Mongolia characterized by a high elevation (>3000-4000 m), low relief landscape within the greater Mongolian Plateau (~2000 m avg. elevation) of central Asia. We have assessed the long-term, large-scale landscape evolution of the region using thermochronologic analysis. Detrital apatite (U-Th-Sm)/He samples from the Selenga River (n = 55) and Orkhon River (n = 15) basins north of the Hangay Dome yield central ages of 134.2 ± 6 and 131.3 ± 9.8 (1σ) Ma, respectively. The regional granitic bedrock apatite (U-Th-Sm)/He single grain age distribution is approximately 95 to 200 Ma, with a homogenized grain central age of 131.2 ± 6.1 Ma. These low-temperature data, in conjunction with K-feldspar MDD 40Ar/39Ar ages of ~200-230 Ma, suggest regional exhumation in the Mesozoic. HeFTy (Ketcham, 2005) modeling corroborates these data and suggests cooling rates of ~3°C/Ma from 220-185 Ma, and applying a geothermal gradient of 21 ± 3°C/km for central Mongolia (Lysak and Dorofeeva, 2003), rock uplift rates from Late Triassic to Mid-Late Jurassic are approximately 100 m/My and from the Early Cretaceous (130 Ma) to the present approximately ≤ 30 m/My. Regional bedrock age patterns, detrital age populations, and thermal modeling suggest that significant recent, rapid rock uplift in central Mongolia is unlikely. Pecube thermo-kinematic models (Braun, 2003) indicate that any rapid (> 500 m/My) event in the Late Miocene-Pliocene would produce Early-Mid Cenozoic cooling ages in lower elevations of the Selenga River drainage basin, which is not supported by the detrital age signal. Pecube modeling of slow rock uplift rates of <50 m/My since the Early Triassic produce regional ages in agreement with geomorphic and geochronologic data. Regional apatite helium age-elevation patterns suggest long-term thermal stability of the upper crust and possible lowering of relief since Mesozoic exhumation. Basalt total fusion 40Ar/39Ar ages

  12. Long-term geochemical surveillance of fumaroles at Showa-Shinzan dome, Usu volcano, Japan

    USGS Publications Warehouse

    Symonds, R.B.; Mizutani, Y.; Briggs, P.H.

    1996-01-01

    This study investigates 31 years of fumarole gas and condensate (trace elements) data from Showa-Shinzan, a dacitic dome-cryptodome complex that formed during the 1943-1945 eruption of Usu volcano. Forty-two gas samples were collected from the highest-temperature fumarole, named A-1, from 1954 (800??C) to 1985 (336??C), and from lower-temperature vents. Condensates were collected contemporaneously with the gas samples, and we reanalyzed ten of these samples, mostly from the A-1 vent, for 32 cations and three anions. Modeling using the thermochemical equilibrium program, SOLVGAS, shows that the gas samples are mild disequilibrium mixtures because they: (a) contain unequilibrated sedimentary CH4 and NH3; (b) have unequilibrated meteoric water; or (c) lost CO, either by air oxidation or by absorption by the sodium hydroxide sampling solution. SOLVGAS also enabled us to restore the samples by removing these disequilibrium effects, and to estimate their equilibrium oxygen fugacities and amounts of S2 and CH4. The restored compositions contain > 98% H2O with minor to trace amounts of CO2, H2, HCl, SO2, HF, H2S, CO, S2 and CH4. We used the restored gas and condensate data to test the hypotheses that these time-series compositional data from the dome's fumaroles provide: (1) sufficient major-gas data to analyze long-term degassing trends of the dome's magma-hydrothermal system without the influence of sampling or contamination effects; (2) independent oxygen fugacity-versus-temperature estimates of the Showa-Shinzan dacite; (3) the order of release of trace elements, especially metals, from magma; and (4) useful information for assessing volcanic hazards. The 1954-1985 restored A-1 gas compositions confirm the first hypothesis because they are sufficient to reveal three long-term degassing trends: (1) they became increasingly H2O-rich with time due to the progressive influx of meteoric water into the dome; (2) their C/S and S/Cl ratios decreased dramatically while their Cl

  13. Computer vision: automating DEM generation of active lava flows and domes from photos

    NASA Astrophysics Data System (ADS)

    James, M. R.; Varley, N. R.; Tuffen, H.

    2012-12-01

    Accurate digital elevation models (DEMs) form fundamental data for assessing many volcanic processes. We present a photo-based approach developed within the computer vision community to produce DEMs from a consumer-grade digital camera and freely available software. Two case studies, based on the Volcán de Colima lava dome and the Puyehue Cordón-Caulle obsidian flow, highlight the advantages of the technique in terms of the minimal expertise required, the speed of data acquisition and the automated processing involved. The reconstruction procedure combines structure-from-motion and multi-view stereo algorithms (SfM-MVS) and can generate dense 3D point clouds (millions of points) from multiple photographs of a scene taken from different positions. Processing is carried out by automated software (e.g. http://blog.neonascent.net/archives/bundler-photogrammetry-package/). SfM-MVS reconstructions are initally un-scaled and un-oriented so additional geo-referencing software has been developed. Although this step requires the presence of some control points, the SfM-MVS approach has significantly easier image acquisition and control requirements than traditional photogrammetry, facilitating its use in a broad range of difficult environments. At Colima, the lava dome surface was reconstructed from recent and archive images taken from light aircraft over flights (2007-2011). Scaling and geo-referencing was carried out using features identified in web-sourced ortho-imagery obtained as a basemap layer in ArcMap - no ground-based measurements were required. Average surface measurement densities are typically 10-40 points per m2. Over mean viewing distances of ~500-2500 m (for different surveys), RMS error on the control features is ~1.5 m. The derived DEMs (with 1-m grid resolution) are sufficient to quantify volumetric change, as well as to highlight the structural evolution of the upper surface of the dome following an explosion in June 2011. At Puyehue Cord

  14. Prospective Type Ia Supernova Surveys From Dome A

    SciTech Connect

    Kim, A.; Bonissent, A.; Christiansen, J.L.; Ealet, A.; Faccioli, L.; Gladney, L.; Kushner, G.; Linder, E.; Stoughton, C.; Wang, L.; /Texas A-M /Purple Mountain Observ.

    2010-02-01

    Dome A, the highest plateau in Antarctica, is being developed as a site for an astronomical observatory. The planned telescopes and instrumentation and the unique site characteristics are conducive toward Type Ia supernova surveys for cosmology. A self-contained search and survey over five years can yield a spectro-photometric time series of {approx}1000 z < 0.08 supernovae. These can serve to anchor the Hubble diagram and quantify the relationship between luminosities and heterogeneities within the Type Ia supernova class, reducing systematics. Larger aperture ({approx}>4-m) telescopes are capable of discovering supernovae shortly after explosion out to z {approx} 3. These can be fed to space telescopes, and can isolate systematics and extend the redshift range over which we measure the expansion history of the universe.

  15. Heavy metals in Antarctic ice from Law Dome: Initial results

    SciTech Connect

    Hong, S. |; Boutron, C.F. |; Edwards, R.; Morgan, V.I.

    1998-08-01

    Pb, Cd, Cu, and Zn have been measured using ultraclean procedures in eight sections taken from two well-dated ice cores from Law Dome, an independent small size ice cap with high accumulation rate situated in the coastal area of East Antarctica. Seven sections were dated from the 1830s to 1940s and one was dated from three millennia ago. The data show that there are strong seasonal variations in the concentrations of Pb and Cd, with values {approximately} two- to four-fold higher in winter than in spring-summer. Evaluation of the contributions from the different sources suggests that contribution from sea salt spray is relatively important, especially for Cd. Contribution from marine biogenic emissions could also be very significant. The importance of marine contributions is consistent with strong intrusions of marine air masses at this coastal site, especially during wintertime.

  16. Prospective Type Ia supernova surveys from Dome A

    SciTech Connect

    Kim, A.; Bonissent, A.; Christiansen, J. L.; Ealet, A.; Faccioli, L.; Gladney, L.; Kushner, G.; Linder, E.; Stoughton, C.; Wang, L.

    2010-03-10

    Dome A, the highest plateau in Antarctica, is being developed as a site for an astronomical observatory. The planned telescopes and instrumentation and the unique site characteristics are conducive toward Type Ia supernova surveys for cosmology. A self-contained search and survey over 5 years can yield a spectro-photometric time series of ~;; 1000 z< 0:08 supernovae. These can serve to anchor the Hubble diagram and quantify the relationship between luminosities and heterogeneities within the Type Ia supernova class, reducing systematics. Larger aperture (>=4-m) telescopes are capable of discovering supernovae shortly after explosion out to z ~;; 3. These can be fed to space telescopes, and can isolate systematics and extend the redshift range over which we measure the expansion history of the universe.

  17. Precision CMB Polarization from Dome-C: the BRAIN experiment

    NASA Astrophysics Data System (ADS)

    Masi, S.; de Bernardis, P.; Giordano, C.; Nati, F.; Piacentini, F.; Polenta, G.; Veneziani, M.; Gervasi, M.; Sironi, G.; Tartari, A.; Zannoni, M.; Peterzen, S.; Bartlett, J.; Giraud-Heraud, Y.; Piat, M.; Rosset, C.; Giard, M.; Pons, R.; Maffei, B.; Ade, P.; Gear, W.; Mauskopf, P.; Piccirillo, L.; Pisano, G.; Savini, G.

    In the current cosmological scenario, part of the linearly polarized emission of the CMB is expected to be rotational (B-modes). This component is due to tensor perturbations of the metric produced by primordial gravitational waves, which are generated a split-second after the Big Bang. The signal expected is of the order of ≲ 0.1 μ K, well below the non-rotational component of the polarization signal (E-modes), and beyond the sensitivity of present generation instruments. New, more sensitive instruments are developed in several labs, with the goal to measure the B-modes. Control of systematics and foregrounds will be the key to make the results of these experiments believable. In this paper we shortly outline BRAIN, a bolometric interferometer devoted to B-modes research, and its pathfinder experiment, devoted to test the Dome-C site.

  18. Sojourner Rover View of Shark and Half Dome

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The rounded knobs (arrows) up to 3 or 4 cm wide on Shark (left; approximately 70 cm wide)) and Half Dome (upper right) and in the foreground could be pebbles in a cemented matrix of clays, silts, and sands; such rocks are called conglomerates. Well-rounded objects like these were not seen at the Viking sites.

    NOTE: original caption as published in Science Magazine.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech).

  19. Cambrian to Holocene structural and burial history of Nashville dome

    SciTech Connect

    Stearns, R.G.; Reesman, A.L.

    1986-02-01

    About 14,000 ft (4270 m) of strata covered basement over the present crest of the Nashville dome by the end of the Paleozoic (calculated by estimating the geothermal gradient, and using temperatures of veins in Stones River Group and Knox Dolomite). At least 7500 ft (2290 m) of post-Devonian strata have been removed by subsequent erosion. Estimates of other erosional episodes include 350 ft (107 m) of upper Knox (during the Middle Ordovician) and 500 ft (152 m) of Devonian-Ordovician (during the Late Devonian). Mesozoic to Holocene uplift was at least 6350 ft (1940 m), 1500 ft or 460 m (25%) of which occurred in the latest 100 m.y. and 450 ft or 140 m (7%) during the latest 2 m.y., a rate ranging from about 15 ft/m.y. (4.6 m/m.y.) for the longer term to over 225 ft/m.y. (70 m/m.y.) in the Pleistocene to Holocene. Earliest structure of the area was a series of elongate basins, probably rifts synchronous with Reelfoot rift to the west. Uplifts trending N10/sup 0/E moved about 40 mi (65 km) westward during the Middle Ordovician. These may relate to similar trending (and moving) Appalachian orogenic events. A change to uplifts trending N50/sup 0/E (parallel to strikes of Appalachian thrusts) occurred in the Late Ordovician and continued to the Devonian; this may reflect a similar Late Ordovician change in the orientation of Appalachian tectonism. In the interval from post-Mississippian to Late Cretaceous, the dome curved westward to join the Pascola arch in response to Ouachita activity. 11 figures, 3 tables.

  20. Behaviour of Atmospheric Boundary Layer Height at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Pietroni, I.; Argentini, S.

    2009-09-01

    The Antarctic Atmospheric Boundary Layer presents characteristics which are substantially different from the mid-latitudes ABLs. On the Antarctic plateau two different extreme situations are observed. During the summer a mixing height develops during the warmer hours of the day although the sensible heat flux is reduced compared to that at mid-latitudes. During the winter a long lived stable boundary layer is continuously present, the residual layer is never observed, consequently the inversion layer is connected at the free atmosphere. To understand the stable ABL process the STABLEDC (Study of the STAble Boundary Layer Environmental at Dome C) experimental field was held at Concordia, the French Italian plateau station at Dome C, during 2005. In the same period the RMO (Routine Measurements Observations) started. The data included turbulence data at the surface, temperature profiles by a microwave profiler (MTP-5P), a mini-sodar and radio-soundings. In this work we will show the results of a comparison of the ABL height at Concordia (3233 m a.s.l) during the summer and the winter using direct measurements and parameterization. The winter ABL height was estimated directly using experimental data (radio-soundings and radiometer temperature and wind velocity profiles) and different methods proposed in literature. The stable ABL height was also estimated using the formulation proposed by Zilitinkevich et al. (2007) for the long-lived stable boundary layer. The correlation of ABL height with the temperature and wind speed is also shown. The summer mixing height was instead estimated by mini-sodar data and compared with the height given by the model suggested by Batchvarova and Gryning (1991) which use as input the turbulence data.

  1. Designing the SALT facility to minimize dome seeing effects

    NASA Astrophysics Data System (ADS)

    de Kock, Mariana; Venter, Sarel J.

    2003-02-01

    Aspects of the design and experience of the Hobby-Eberly Telescope (HET) were incorporated in the SALT facility design. The characteristics of the local environment were taken into account to ensure a building that is cost effective and functional. The effect of heat from the control room and other warm areas were studied and their locations changed to limit thermal effects. A steel false floor, incorporating forced ventilation and extending around the telescope azimuth pier, was installed. This prevents heat radiating from large concrete surfaces with temperatures potentially higher than ambient. Because site testing (i.e. micro thermal measurements) indicated high turbulence within ~5 m of the ground level, the telescope and pier were raised to improve dome seeing. The SALT site is significantly windy all year round (median velocity = 4.8 m/s), and this was utilized to design better ventilation of the facility using adjustable louvers for natural ventilation. Results of a computational fluid dynamic analysis (CFD) are presented which show an adequate temperature distribution at wind speeds as low as 0.5 m/s. The telescope chamber and dome are build out of insulation panels to ensure low thermal losses during the day when the chamber is air conditioned and thus limit electricity consumption and thermal gradients. Large equipment that emit heat or vibration are housed in a separate utility building 50 m from the telescope in the non-prevailing wind direction in order to limit their effect on the telescope. Vented air from the building is also released at this site.

  2. Volcanic synchronization of Dome Fuji and Dome C Antarctic deep ice cores over the past 216 kyr

    NASA Astrophysics Data System (ADS)

    Fujita, S.; Parrenin, F.; Severi, M.; Motoyama, H.; Wolff, E. W.

    2015-10-01

    Two deep ice cores, Dome Fuji (DF) and EPICA Dome C (EDC), drilled at remote dome summits in Antarctica, were volcanically synchronized to improve our understanding of their chronologies. Within the past 216 kyr, 1401 volcanic tie points have been identified. DFO2006 is the chronology for the DF core that strictly follows O2 / N2 age constraints with interpolation using an ice flow model. AICC2012 is the chronology for five cores, including the EDC core, and is characterized by glaciological approaches combining ice flow modelling with various age markers. A precise comparison between the two chronologies was performed. The age differences between them are within 2 kyr, except at Marine Isotope Stage (MIS) 5. DFO2006 gives ages older than AICC2012, with peak values of 4.5 and 3.1 kyr at MIS 5d and MIS 5b, respectively. Accordingly, the ratios of duration (AICC2012 / DFO2006) range between 1.4 at MIS 5e and 0.7 at MIS 5a. When making a comparison with accurately dated speleothem records, the age of DFO2006 agrees well at MIS 5d, while the age of AICC2012 agrees well at MIS 5b, supporting their accuracy at these stages. In addition, we found that glaciological approaches tend to give chronologies with younger ages and with longer durations than age markers suggest at MIS 5d-6. Therefore, we hypothesize that the causes of the DFO2006-AICC2012 age differences at MIS 5 are (i) overestimation in surface mass balance at around MIS 5d-6 in the glaciological approach and (ii) an error in one of the O2 / N2 age constraints by ~ 3 kyr at MIS 5b. Overall, we improved our knowledge of the timing and duration of climatic stages at MIS 5. This new understanding will be incorporated into the production of the next common age scale. Additionally, we found that the deuterium signals of ice, δDice, at DF tends to lead the one at EDC, with the DF lead being more pronounced during cold periods. The lead of DF is by +710 years (maximum) at MIS 5d, -230 years (minimum) at MIS 7a and +60

  3. Magnetic and microstructural investigation of high-coercivity net-shape Nd-Fe-B-type magnets produced from spark-plasma-sintered melt-spun ribbons blended with DyF3

    NASA Astrophysics Data System (ADS)

    Žagar, Kristina; Kocjan, Andraž; Kobe, Spomenka

    2016-04-01

    Nanostructured Nd-Fe-B-type materials produced by melt-spinning (MS) are used in a variety of applications in the electronics, automotive, and sensor industries. The very rapid MS process leads to flake-like powders with metastable, nanoscale, Nd2Fe14B grains. These powders are then formed into net-shaped, isotropic, polymer-bonded magnets, or they are hot formed into fully dense, metallic magnets that are isotropic and anisotropic. These fully dense magnets are usually produced with a conventional hot press without the inclusion of additives prior to the hot pressing. As a result, their properties, particularly the coercivity (Hci), are insufficient at automotive-relevant temperatures of 100-150 °C since the material Hci has a large temperature coefficient. In this study, we instead add a thin layer of DyF3 to the melt-spun ribbons prior to their hot consolidation in order to enhance the coercivity through a diffusion-based, partial substitution of the Nd by Dy. This is accomplished by applying extremely rapid, spark-plasma sintering to minimize any growth of the nanoscale Nd2Fe14B grains during consolidation. The result is a very high-coercivity magnet with drastically reduced amounts of heavy rare earths that is suitable for high-temperature applications. This work clearly demonstrates how rapidly formed, metastable states can provide us with properties that are unobtainable with conventional techniques.

  4. Degassing history of a mid-ocean ridge rhyolite dome on the Alarcon Rise, Gulf of California

    NASA Astrophysics Data System (ADS)

    Portner, R. A.; Dreyer, B. M.; Clague, D. A.; Lowenstern, J. B.; Head, J. W., III; Saal, A. E.

    2014-12-01

    A 2350 meter deep rhyolite lava dome and surrounding intermediate-mafic complex on the Alarcon Rise mid-ocean ridge in the Gulf of California was sampled extensively during a 2012 MBARI expedition. The dome is predominantly composed of sparsely vesicular (<10%) obsidian with local deposits of pumiceous breccia. Pumiceous lapilli comprise highly vesicular (40-60%) fracture networks that separate non-vesicular obsidian "pseudoclasts". Textures and major element geochemistry suggest that both lithologies originated from the same magma that formed the majority of the dome. This is corroborated by comparable major element compositions (~75% SiO2) and near-equilibrium phenocryst assemblages including olivine (Fo10) and plagioclase (An17). Attenuated total reflectance (ATR) and transmission FTIR spectroscopy was used to measure H2O concentrations in olivine and plagioclase melt inclusions as well as host glasses (CO2 was below detection, <30 ppm). Rhyolite host glass contains 1.5-2.0 wt% H2O, similar to nearby andesite and dacite. These concentrations agree with saturation limits for H2O (1.7%) at the depth of Alarcon Rise, but are slightly less than what is predicted by fractional crystallization modeling. Melt inclusions from plagioclase and olivine in rhyolite contain a maximum of 3.5-4.5% H2O suggesting that up to 3.0% H2O exsolved into bubbles during a 3 km ascent. Hydrostatic pressures (23 MPa) at the eruptive vent would have permitted 53% vesiculation in agreement with petrographic observations. Although ~50% vesiculation and exsolved H2O contents of 3.0 wt% are less than the ideal threshold for magmatic fragmentation, the presence of highly vesicular ash particles representing fragmented pumiceous breccia argues otherwise. We posit that decoupled volatiles from a deeper magma body migrated through fracture networks to the surface causing mild explosivity.

  5. Bayesian Inversion using Physics-based Models Applied to Dome Extrusion at Mount St. Helens 2004-2008

    NASA Astrophysics Data System (ADS)

    Wong, Y. Q.; Segall, P.; Anderson, K. R.; Bradley, A. M.

    2015-12-01

    Physics-based models of volcanic eruptions have grown more sophisticated over the past few decades. These models, combined with Bayesian inversion, offer the potential of integrating diverse geological and geophysical datasets to better understand volcanic systems. Using a Markov Chain Monte Carlo (MCMC) algorithm with a physics-based conduit model, we invert data from the 2004-2008 dome-forming eruption at Mount St. Helens, USA. We extend the 1D cylindrical conduit model of Anderson and Segall [2011] to include vertical and lateral gas loss from the magma, as well as equilibrium crystallization. The melt viscosity increases strongly with crystal content. Magma permeability obeys the Kozeny-Carman law with a threshold porosity. Excess pressure in the magma chamber drives Newtonian flow of magma upwards until the viscous resistance to flow exceeds the rate-dependent frictional strength on the conduit wall, at which point the magma transitions from viscous flow to plug flow. We investigate the steady-state solutions for lava dome growth between March and December 2005, in which magma chamber pressure, initial water content, permeability and friction parameters are unknown model parameters. These parameters are constrained by: dome rock porosity, extrusion rate from photogrammetry, plug depth from drumbeat earthquakes, and crystallization pressure from petrologic studies. Posterior probability density functions (PDFs) reveal the constraints on the model parameters and their correlations. Assuming lithostatic normal stress on the plug, low coefficients of friction (0.1-0.3) are required to allow extrusion at the observed rate while maintaining reasonable magma chamber pressures. Lower effective normal stress or melt viscosity could allow for larger friction coefficients. Future work will investigate the time-dependent system, thereby allowing us to incorporate time-evolving geodetic and eruption rate data into the inversion.

  6. On lava dome growth, with application to the 1979 lava extrusion of the soufrière of St. Vincent

    NASA Astrophysics Data System (ADS)

    Huppert, Herbert E.; Shepherd, John B.; Haraldur Sigurdsson, R.; Sparks, Stephen J.

    1982-12-01

    A theoretical analysis is presented for the spread of a viscous liquid flowing under its own hydrostatic pressure on a horizontal surface in order to model lava dome formation. Two situations are considered in detail: the spreading of a constant volume of liquid and the case where the amount of liquid is continually increased. Experiments with silicone liquids show close agreement with theory. The formation of a basaltic andesite lava extrusion in 1979 on the crater floor of the Soufrière of St. Vincent (West Indies) provided the motivation for and an application of the model. The extrusion reached a diameter of 868 m and a height of 133 m over a period of 150 days. Over the first 90 days the growth relationships were consistent with those predicted by theory. Application of the theory to the Soufrière dome suggests an effective viscosity of 2 X 10 12 poise for the basaltic andesite lava. The large effective viscosity calculated for the lava may be attributed to the dominant influence of a high-viscosity skin which forms at the margins of the flow as it cools. After 70 days, the rate of growth of the extrusion markedly decreased because a substantial collar of rubble accumulated at the flow front. Due to this collar the growth of the extrusion ceased after 150 days. From approximately two weeks after the initiation of the extrusion, the discharge rate of lava decreased approximately linearly with increasing dome height. This observation suggests that the lava ascended under a decreasing hydrostatic driving pressure and that extrusion ceased when the lava column reached hydrostatic equilibrium.

  7. Real-Time Measurements of Aft Dome Insulation Erosion on Space Shuttle Reusable Solid Rocket Motor

    NASA Technical Reports Server (NTRS)

    McWhorter, Bruce; Ewing, Mark; Albrechtsen, Kevin; Noble, Todd; Longaker, Matt

    2004-01-01

    Real-time erosion of aft dome internal insulation was measured with internal instrumentation on a static test of a lengthened version of the Space Shuffle Reusable Solid Rocket Motor (RSRM). This effort marks the first time that real-time aft dome insulation erosion (Le., erosion due to the combined effects of thermochemical ablation and mechanical abrasion) was measured in this kind of large motor static test [designated as Engineering Test Motor number 3 (ETM3)I. This paper presents data plots of the erosion depth versus time. The data indicates general erosion versus time behavior that is in contrast to what would be expected from earlier analyses. Engineers have long known that the thermal environment in the aft dome is severe and that the resulting aft dome insulation erosion is significant. Models of aft dome erosion involve a two-step process of computational fluid dynamics (CFD) modeling and material ablation modeling. This modeling effort is complex. The time- dependent effects are difficult to verify with only prefire and postfire insulation measurements. Nozzle vectoring, slag accumulation, and changing boundary conditions will affect the time dependence of aft dome erosion. Further study of this data and continued measurements on future motors will increase our understanding of the aft dome flow and erosion environment.

  8. An Attempt to Asses Suitability of Middle-Poland Salt Domes for Natural Gas Storage / Ocena Przydatności Środkowopolskich Wysadów Solnych Do Magazynowania Gazu Ziemnego

    NASA Astrophysics Data System (ADS)

    Ślizowski, Jarosław; Urbańczyk, Kazimierz

    2012-11-01

    The aim of the paper is to assess geological conditions in Middle-Poland salt domes and their suitability for natural gas storage. The starting point to the assessment were statistical distributions of caverns depth and volume in Mogilno CUGS. The distributions were generalized to other domes using the part of anticline forms in the salt mirror surface. The expected average cavern volumes, depths with their standard deviations are evaluated. Storing capacity of the caverns and the risk of a borehole unsuitable for cavern location are also given.

  9. The annual cycle and biological effects of the Costa Rica Dome

    NASA Astrophysics Data System (ADS)

    Fiedler, Paul C.

    2002-02-01

    The Costa Rica Dome is similar to other tropical thermocline domes in several respects: it is part of an east-west thermocline ridge associated with the equatorial circulation, surface currents flow cyclonically around it, and its seasonal evolution is affected by large-scale wind patterns. The Costa Rica Dome is unique because it is also forced by a coastal wind jet. Monthly climatological fields of thermocline depth and physical forcing variables (wind stress curl and surface current divergence) were analyzed to examine the structure and seasonal evolution of the dome. The annual cycle of the dome can be explained by wind forcing in four stages: (1) coastal shoaling of the thermocline off the Gulf of Papagayo during February-April, forced by Ekman pumping on the equatorward side of the Papagayo wind jet; (2) separation from the coast during May-June when the intertropical convergence zone (ITCZ) moves north to the countercurrent thermocline ridge, the wind jet stops, and the North Equatorial Countercurrent extends toward the coast on the equatorward flank of the ridge; (3) countercurrent thermocline ridging during July-November, when the dome expands to the west as the countercurrent thermocline ridge shoals beneath a band of cyclonic wind stress curl on the poleward side of the ITCZ; and (4) deepening during December-January when the ITCZ moves south and strong trade winds blow over the dome. Coastal eddies may be involved in the coastal shoaling observed during February-March. A seasonally predictable, strong, and shallow thermocline makes the Costa Rica Dome a distinct biological habitat where phytoplankton and zooplankton biomass are higher than in surrounding tropical waters. The physical structure and biological productivity of the dome affect the distribution and feeding of whales and dolphins, probably through forage availability.

  10. Analysis of the imaging performance of panoramic annular lens with conic conformal dome

    NASA Astrophysics Data System (ADS)

    Huang, Xiao; Bai, Jian

    2015-10-01

    Panoramic annular lens (PAL) is a kind of the specific wide angle lenses which is widely applied in panoramic imaging especially in aerospace field. As we known, to improve the aerodynamic performance of the aircraft, conformal dome, which notably reduces the drag of an aircraft, is also functioning as an optical window for the inbuilt optical system. However, there is still no report of the specific analysis of the imaging performance of PAL with conformal dome, which is imperative in its aerospace-related applications. In this paper, we propose an analysis of the imaging performance of a certain PAL with various conic conformal domes. Working in visible wavelength, the PAL in our work observes 360° surroundings with a large field of view (FOV) ranging from 30° ~105° . Meanwhile, various thicknesses, half-vertex angles, materials of the conic dome and the central distances between the dome and PAL are considered. The imaging performances, mainly indicated by modulation transfer function (MTF) as well as RMS radius of the spot diagram, are systematically compared. It is proved that, on the contrary to the general cases, the dome partly contributes to the imaging performance of the inbuilt PAL. In particular, with a conic conformal dome in material of K9 glass with a half-vertex angle of 25° and a thickness of 6mm, the maximum MTF at 100lp/mm could be improved by 6.68% with nearly no degeneration of the minimum MTF, and the RMS radius could be improved by 14.76% to 19.46% in different FOV. It is worth to note that the PAL is adaptive to panoramic aerospace applications with conic or quasi-conic conformal dome and the co-design of both PAL and the dome is very important.

  11. Selected Aspects of the Structural Analysis of the North Dome in the 'Four Domes Pavilion'/ Wybrane Aspekty Analizy Konstrukcyjnej Kopuły Północnej W Pawilonie Czterech Kopuł

    NASA Astrophysics Data System (ADS)

    Jasieńko, Jerzy; Raszczuk, Krzysztof; Moczko, Marta; Piechówka-Mielnik, Magdalena

    2015-06-01

    The subject of the paper is north dome of the Four Domes Pavilion in Wroclaw, which was erected according to the project by architect Hans Poelzig in 1913. The geometry of the dome (plan, rise, thickness) has an essential influence on the stress distribution in the structure and may be a crucial factor determining the cracking pattern. The results of the study of archival documents and numerical analysis indicate that there is a need for increasing the bearing capacity of the structure. After carrying out 3D FEM analysis, it was decided to apply strengthening technology based on the FRCM system with carbon and P.B.O. fibers on the surface and on the external ring of the dome. Powszechnie występującą na całym świecie formą przekryć historycznych jest kopuła, która może być realizowana m.in. na rzucie koła, elipsy czy ośmioboku. Geometria kopuły (rzut, wyniesienie oraz grubość) wpływa na rozkład naprężeń w konstrukcji i może być decydującym czynnikiem wpływającym na propagację rys. Przedmiotem pracy jest Pawilon Czterech Kopuł we Wrocławiu, który powstał wg projektu Hansa Poelziga w 1913r. Analiza dokumentacji archiwalnej wykazuje, iż wszelkie zmiany jakich się podejmowano w trakcie realizacji prac były wynikiem: braku czasu, opóźnień w wykonaniu oceny statycznej, przekazaniu rysunków projektowych w nieodpowiedniej skali oraz prowadzenia prac budowlanych w zimie. Efektem powyższych działań jest niedostateczne zbrojenie kopuły, która uległa uszkodzeniom w formie pęknięć południkowych i równoleżnikowych od strony zewnętrznej i wewnętrznej. W wyniku przeprowadzonej analizy konstrukcyjnej przy użyciu Metody Elementów Skończonych (MES) podjęto decyzję o wzmocnieniu przekrycia przy użyciu siatek z włókien węglowych w systemie FRCM oraz wzmocnienie pierścienia górnego przy użyciu siatek z włókien P.B.O. w matrycy mineralnej.

  12. Evolution of the microstructure and hardness of a rapidly solidified/melt-spun AZ91 alloy upon aging at different temperatures

    SciTech Connect

    Wang Baishu; Liu Yongbing; An Jian; Li Rongguang; Su Zhenguo; Su Guihua; Lu You; Cao Zhanyi

    2009-04-15

    The effect of aging at different temperatures on a rapidly solidified/melt-spun AZ91 alloy has been investigated in depth. The microstructures of as-spun and aged ribbons with a thickness of approximately 60 {mu}m were characterized using X-ray diffraction, transmission electron microscopy and laser optical microscopy; microhardness measurements were also conducted. It was found that the commercial AZ91 alloy undergoes a cellular/dendritic transition during melt-spinning at a speed of 34 m/s. A strengthening effect due to aging was observed: a maximum hardness of 110 HV/0.05 and an age-hardenability of 50% were obtained when the ribbon was aged at 200 deg. C for 20 min. The {beta}-Mg{sub 17}Al{sub 12} phase exhibits net and dispersion types of distribution during precipitation. The dispersion of precipitates in dendritic grains or cells is the main source of strengthening.

  13. Design and Test of Low-Profile Composite Aerospace Tank Dome

    NASA Technical Reports Server (NTRS)

    Ahmed, R.

    1999-01-01

    This report summarizes the design, analysis, manufacture, and test of a subscale, low-profile composite aerospace dome under internal pressure. A low-profile dome has a radius-to-height ratio greater than the square root of two. This effort demonstrated that a low-profile composite dome with a radius-to-height ratio of three was a feasible design and could adequately withstand the varying stress states resulting from internal pressurization. Test data for strain and displacement versus pressure are provided to validate the design.

  14. Preliminary investigation of gold mineralization in the Pedro Dome-Cleary Summit area, Fairbanks district, Alaska

    USGS Publications Warehouse

    Pilkington, H.D.; Forbes, R.B.; Hawkins, D.B.; Chapman, R.M.; Swainbank, R.C.

    1969-01-01

    Anomalous gold values in mineralized veins and hydrothermally altered quartz-mica schist in the Pedro Dome-Cleary Summit area of the Fairbanks district suggest the presence of numerous small low- to high-grade lodes. Anomalous concentrations of gold were found to exist in the wall rocks adjacent to mineralized veins. In general, the gold concentration gradients in these wall rocks are much too steep to increase appreciably the mineable width of the veins. Anomalous gold values were also detected in bedrock samples taken by means of a power auger on the Murphy Dome Road along the southwest extension of the Pedro Dome-Cleary Summit mineralized belt.

  15. Finite element analysis/hydroburst test data correlation for reverse dome integrated stage application

    NASA Astrophysics Data System (ADS)

    Burson, K. S.; Nowakowski, M.; Tiwari, S.

    1993-02-01

    The U.S. Army's Missile Integrated Stage ('MIST') program has undertaken the development of an advanced strategic interceptor booster's solid-fueled rocket motor. The primary structural components of this booster are a composite case with full-diameter aft closure opening, a titanium reverse dome, and a forced-deflection nozzle plug housing. Attention is presently given to the correlation between the analytical models used in this program and the hydroburst test data obtained for the MIST reverse dome. It is found that the reverse dome exceeded the minimum required burst pressure of 2300 psig.

  16. High-resolution ground layer turbulence from inside the CFHT dome using a lunar scintillometer

    NASA Astrophysics Data System (ADS)

    Pfrommer, T.; Hickson, P.

    2015-04-01

    For ground layer adaptive optics systems, knowledge of the local height- and time- resolved ground layer (GL) turbulence is crucial to link local topography with optical turbulence. Such turbulence profiles have been obtained in the years 2009 and 2010 over 250 hours on Mauna Kea, Hawaii. Results from measurements inside the Canada-France-Hawaii Telescope (CFHT) dome indicate severe degradation of image quality due to a poorly vented dome and thus provide input for dome modifications and design aspects for a new ground layer adaptive optics system. The outside median GL seeing above 6 metres was determined to be 0.48±0.01”.

  17. Volcanism in southern Guinevere Planitia, Venus: Regional volcanic history and morphology of volcanic domes

    NASA Technical Reports Server (NTRS)

    Crown, David A.; Stofan, Ellen R.; Plaut, Jeffrey J.

    1993-01-01

    Guinevere Planitia is a low-lying region located between the highlands of Beta Regio and Eistla Regio. Analyses of Pioneer Venus, Goldstone, and Arecibo radar data suggested that the surface of Guinevere Planitia is dominated by volcanism, primarily in the form of bright, dark, and mottled plains units. Also identified in this region was the Beta-Eistla Deformation Zone, composed of ovoids and discontinuous segments of lineament belts that have been embayed by the surrounding plains. The resolution of Magellan SAR images allows detailed investigations of the volcanic deposits found in the area in order to determine the types of eruptive activity which have occurred and to constrain the regional volcanic history. Analyses of an area of southern Guinevere Planitia between 0-25 deg N and 300-330 deg indicate the presence of a wide variety of volcanic land forms, including large shield volcanoes, widespread plains, lava flow fields, and small domes, cones, and shields as well as coronae and other circular structures that have associated volcanic deposits.

  18. Investigation of the Nozzle Diameter as a Control Parameter of the Properties of Melt-Spun Sb2- x Bi x Te3

    NASA Astrophysics Data System (ADS)

    Ohorodniichuk, V.; Dauscher, A.; Masschelein, Ph.; Candolfi, C.; Baranek, Ph.; Dalicieux, P.; Lenoir, B.

    2016-03-01

    Three kinds of Sb1.6Bi0.4Te3.1 samples were prepared by the melt-spinning technique using quartz tubes with different nozzle's diameters (1.0, 0.7 and 0.5 mm) to study the sensitivity of the thermoelectric properties to the variations of this parameter. The melt-spun ribbons were densified by spark plasma sintering (SPS). The melt-spun samples were characterized by powder x-ray diffraction and scanning electron microscopy. The dimensionless figures of merit ( ZT) were calculated from the data obtained by measuring the Seebeck coefficient, electrical resistivity and thermal conductivity in the direction perpendicular to the uniaxial pressing direction of SPS. All ZT values for this set of samples were close to 1.0 around 380 K. The highest ZT value was obtained for the sample prepared using the largest nozzle diameter of 1.0 mm. Despite some variations in the carrier concentrations of the samples being observed, these results indicate a weak sensitivity of the melt-spun Sb1.6Bi0.4Te3.1 samples to the nozzle's diameter during the melt-spinning process.

  19. An Analysis of Gas Pressure Forming of Superplastic AL 5083 Alloy

    SciTech Connect

    Syn, C K; O'Brien, M J; Lesuer, D R; Sherby, O D

    2001-05-04

    Al 5083 disks of a superplastic forming grade were gas-pressure formed to hemispheres and cones at constant forming pressures with and without back pressure. The forming operation was performed using an in-house designed and built biaxial forming apparatus. The temporal change of dome heights of the hemispheres and cones were measured for the different forming and back pressures applied. The flow stresses and strain rates developed at the top of the dome during the forming step were shown to closely follow the flow stress-strain rate relationship obtained from the strain rate change tests performed at the same temperature using uniaxial tensile samples.

  20. Precipitation regime and stable isotopes at Dome Fuji, East Antarctica

    NASA Astrophysics Data System (ADS)

    Dittmann, Anna; Schlosser, Elisabeth; Masson-Delmotte, Valérie; Powers, Jordan G.; Manning, Kevin W.; Werner, Martin; Fujita, Koji

    2016-06-01

    A unique set of 1-year precipitation and stable water isotope measurements from the Japanese Antarctic station, Dome Fuji, has been used to study the impact of the synoptic situation and the precipitation origin on the isotopic composition of precipitation on the Antarctic Plateau. The Antarctic Mesoscale Prediction System (AMPS) archive data are used to analyse the synoptic situations that cause precipitation. These situations are investigated and divided into five categories. The most common weather situation during a precipitation event is an upper-level ridge that extends onto the Antarctic Plateau and causes strong northerly advection from the ocean. Most precipitation events are associated with an increase in temperature and wind speed, and a local maximum of δ18O. During the measurement period, 21 synoptically caused precipitation events caused 60 % of the total annual precipitation, whereas the remaining 40 % were predominantly attributed to diamond dust. By combining the synoptic analyses with 5-day back-trajectories, the moisture source regions for precipitation events were estimated. An average source region around a latitude of 55° S was found. The atmospheric conditions in the source region were used as initial conditions for running a Rayleigh-type isotopic model in order to reproduce the measured isotopic composition of fresh snow and to investigate the influence of the precipitation source region on the isotope ratios. The model represents the measured annual cycle of δ18O and the second-order isotopic parameter deuterium excess reasonably well, but yields on average too little fractionation along the transport/cooling path. While simulations with an isotopic general circulation model (GCM) (ECHAM5-wiso) for Dome Fuji are on average closer to the observations, this model cannot reproduce the annual cycle of deuterium excess. In the event-based analysis, no evidence of a correlation of the measured deuterium excess with the latitude of the

  1. Discovery of Critical Oxygen Content for Glass Formation in Zr80Pt20 Melt Spun Ribbons

    SciTech Connect

    D.J. Sordelet; E.A. Rozhkova; X. Yang; M.J. Kramer

    2004-09-30

    Zr{sub 80}Pt{sub 20} alloys may form meta-stable quasicrystals either during devitrification of an amorphous phase or directly upon cooling from a liquid depending on processing conditions. To date, little attention has been given to the role of oxygen on the glass formation or devitrification behavior of Zr-Pt and similar alloys. This study reveals that oxygen content during melt spinning indeed strongly influences the formation of the as-quenched structure. A critical amount of oxygen was found to be required to form amorphous ribbons at a fixed quench rate. At lower oxygen levels (i.e., <500 ppm mass), a fully crystallized is formed; the structure is composed mainly of meta-stable {beta}-Zr with a small fraction of a quasicrystalline phase. At higher oxygen levels, the as-quenched structure transitions to a fully amorphous structure ({approx}1000 ppm mass), and with further oxygen addition forms a mixture of amorphous and quasicrystalline ({approx}1500 ppm mass) or crystalline phases (>2500 ppm mass). Details regarding the structure of the meta-stable {beta}-Zr phase in the low-oxygen ribbons are provided along with a discussion of the structural similarity between this phase and the quasicrystal structure that formed in this alloy.

  2. Water-quality data for aquifers, streams, and lakes in the vicinity of Keechi, Mount Sylvan, Oakwood, and Palestine salt domes, northeast Texas salt-dome basin

    USGS Publications Warehouse

    Carr, Jerry E.; Halasz, Stephen J.; Liscum, Fred

    1980-01-01

    This report contains water-quality data for aquifers, streams, and lakes in the vicinity of Keechi, Mount Sylvan, Oakwood, and Palestine Salt Domes, in the northeast Texas salt-dome basin. Water-quality data were compiled for aquifers in the Wilcox Group, the Carrizo Sand, and the Queen City Sand. The data include analyses for dissolved solids, pH, temperature, hardness, calcium, magnesium, sodium, bicarbonate, chloride, and sulfate. Water-quality and streamflow data were obtained from 63 surface-water sites in the vicinity of the domes. These data include water discharge, specific conductance, pH, water temperature, and dissolved oxygen. Samples were collected at selected sites for analysis of principal and selected minor dissolved constituents.

  3. Spin Forming of Aluminum Metal Matrix Composites

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.; Munafo, Paul M. (Technical Monitor)

    2001-01-01

    An exploratory effort between NASA-Marshall Space Flight Center (MSFC) and SpinCraft, Inc., to experimentally spin form cylinders and concentric parts from small and thin sheets of aluminum Metal Matrix Composites (MMC), successfully yielded good microstructure data and forming parameters. MSFC and SpinCraft will collaborate on the recent technical findings and develop strategy to implement this technology for NASA's advanced propulsion and airframe applications such as pressure bulkheads, combustion liner assemblies, propellant tank domes, and nose cone assemblies.

  4. Realizing the full nanofiller enhancement in melt-spun fibers of poly(vinylidene fluoride)/carbon nanotube composites.

    PubMed

    Yang, Jinghui; Chen, Qiyi; Chen, Feng; Zhang, Qin; Wang, Ke; Fu, Qiang

    2011-09-01

    Strong interfacial interaction is extremely important for achieving efficient mechanical reinforcement in polymer/inorganic nanoparticle composites. In this study, it was demonstrated for the first time that largely improved interfacial interaction could be obtained in continuously melt-spun fibers of poly(vinylidene fluoride) (PVDF)/multi-walled carbon nanotube (MWCNTs) composites, just by an increasing of the deformation extent (draw ratio). The superior interaction is attributed to high deformation inducing a formation of charge-transfer-type F-C bonding between all-trans conformation PVDF chains and extended MWCNTs. As a result, a large mechanical enhancement has been achieved. For the fibers prepared at the highest draw ratio of 200, the tensile strength and modulus are improved for 235% and 109%, respectively, after adding only 0.5 wt% MWCNTs to PVDF. More importantly, a mechanical model fitting, based on the rule of mixtures, indicates that in the case of the highest draw ratio the theoretical strength of MWCNTs is comparable to its real failure strength measured directly between two opposing AFM cantilever tips (Yu et al 2000 Science 287 637). Our present study suggests a great deal of promise for achieving highly efficient CNT enhancement via the non-covalent interaction arising from simple physical fabrication like melt-spinning. PMID:21821872

  5. Microstructural homogeneity of support silk spun by Eriophora fuliginea (C.L. Koch) determined by scanning X-ray microdiffraction

    NASA Astrophysics Data System (ADS)

    Riekel, C.; Craig, C. L.; Burghammer, M.; Müller, M.

    2001-01-01

    Scanning X-ray microdiffraction (SXD) permits the 'imaging' in-situ of crystalline phases, crystallinity and texture in whole biopolymer samples on the micrometre scale. SXD complements transmission electron microscopy (TEM) techniques, which reach sub-nanometre lateral resolution but require thin sections and a vacuum environment. This is demonstrated using a support thread from a web spun by the orb-weaving spider Eriophora fuliginea (C.L. Koch). Scanning electron microscopy (SEM) shows a central thread composed of two fibres to which thinner fibres are loosely attached. SXD of a piece of support thread approximately 60 µm long shows in addition the presence of nanometre-sized crystallites with the β-poly(L-alanine) structure in all fibres. The crystallinity of the thin fibres appears to be higher than that of the central thread, which probably reflects a higher polyalanine content of the fibroins. The molecular axis of the polymer chains in the central thread is orientated parallel to the macroscopic fibre axis, but in the thin fibres the molecular axis is tilted by about 71° to the macroscopic fibre axis. A helical model is tentatively proposed to describe this morphology. The central thread has a homogeneous distribution of crystallinity along the macroscopic fibre axis.

  6. Spun-wrapped aligned nanofiber (SWAN) lithography for fabrication of micro/nano-structures on 3D objects.

    PubMed

    Ye, Zhou; Nain, Amrinder S; Behkam, Bahareh

    2016-07-01

    Fabrication of micro/nano-structures on irregularly shaped substrates and three-dimensional (3D) objects is of significant interest in diverse technological fields. However, it remains a formidable challenge thwarted by limited adaptability of the state-of-the-art nanolithography techniques for nanofabrication on non-planar surfaces. In this work, we introduce Spun-Wrapped Aligned Nanofiber (SWAN) lithography, a versatile, scalable, and cost-effective technique for fabrication of multiscale (nano to microscale) structures on 3D objects without restriction on substrate material and geometry. SWAN lithography combines precise deposition of polymeric nanofiber masks, in aligned single or multilayer configurations, with well-controlled solvent vapor treatment and etching processes to enable high throughput (>10(-7) m(2) s(-1)) and large-area fabrication of sub-50 nm to several micron features with high pattern fidelity. Using this technique, we demonstrate whole-surface nanopatterning of bulk and thin film surfaces of cubes, cylinders, and hyperbola-shaped objects that would be difficult, if not impossible to achieve with existing methods. We demonstrate that the fabricated feature size (b) scales with the fiber mask diameter (D) as b(1.5)∝D. This scaling law is in excellent agreement with theoretical predictions using the Johnson, Kendall, and Roberts (JKR) contact theory, thus providing a rational design framework for fabrication of systems and devices that require precisely designed multiscale features. PMID:27283144

  7. Influence of hydroxyapatite crystallization temperature and concentration on stress transfer in wet-spun nanohydroxyapatite-chitosan composite fibres.

    PubMed

    Xie, J Z; Hein, S; Wang, K; Liao, K; Goh, K L

    2008-06-01

    Hydroxyapatite possesses appropriate osteoconductivity and biocompatibility for hard-tissue replacement implants but suffers from brittleness. One approach to overcome this problem is to incorporate nanometre hydroxyapatite (nHA) into a polymer matrix, such as chitosan, to yield a hydroxyapatite-chitosan (HC) composite. Here, a novel HC composite was synthesized and its elastic properties were investigated by varying (1) nHA concentration and (2) crystallization temperature (T), where T is a parameter which influences the morphology of the crystals. Crystals of nHA were precipitated at T = 40 degrees C and 100 degrees C, blended in a chitosan matrix, and wet-spun to yield fibres of HC composites at 5, 15, 20 and 40% concentrations (mass fraction of nHA). Scanning electron microscopy and energy-dispersive x-ray spectroscopy revealed a uniform distribution of nanocrystallites within the fibre. Tensile testing revealed that HC fibres, which comprised nHA treated at T = 100 degrees C, possessed low tensile strength, sigma(0), and stiffness, E, at low nHA concentrations but high sigma(0) and E at higher concentrations, i.e. beyond a 15% mass fraction of nHA. However, with nHA treated at T = 40 degrees C, the fibres yielded high sigma(0) and E at low nHA concentrations but low sigma(0) and E at high concentrations. The results strongly implicate the underlying effect of crystallite morphology on stress transfer at different concentrations. PMID:18477816

  8. Magnetization and magnetoresistance in melt-spun Cu{sub 80}Fe{sub 5}Ni{sub 15}

    SciTech Connect

    Martins, C. S.; Missell, F. P.

    2001-06-01

    Magnetization and magnetoresistance (MR) were studied (0{lt}H{lt}70kOe, 4.2K{lt}T{lt}300K) in as-cast and annealed (T{sub an}=400, 450, and 500{degree}C) samples of melt-spun Cu{sub 80}Fe{sub 5}Ni{sub 15}. Field-cooled magnetization curves, when compared with the Curie{endash}Weiss law, suggest the presence of antiferromagnetic interactions ({Theta}={minus}57K) between nanoparticles for T{sub an}=450 and 500{degree}C. Antiferromagnetic interactions have been predicted when dipolar interactions dominate Ruderman{endash}Kittel{endash}Kasuya{endash}Yosida interactions in large particles. Here antiferromagnetic interactions are attributed to particles roughly 4 to 5 nm in size. The largest MR value (MR{similar_to}17% at H=70kOe and T=10K) is found for the as-cast material. For samples annealed at 400{degree}C, MR curves are linear in H above 10 kOe and are in qualitative agreement with a model which considers short-range magnetic scattering by particles of different sizes. {copyright} 2001 American Institute of Physics.

  9. Magnetic hardening of melt-spun nanocomposite Nd{sub 2}Fe{sub 14}B/Fe magnets

    SciTech Connect

    Panagiotopoulos, I.; Withanawasam, L.; Murthy, A.S.; Hadjipanayis, G.C.; Singleton, E.W.; Sellmyer, D.J.

    1996-04-01

    Coercivity optimization studies were done on melt-spun nanocomposite Nd{sub 4}R{sub 2}Fe{sub 87{minus}{ital x}}NbT{sub x}B{sub 6} (R=Nd,Y,Dy; T=Ag,Cu) isotropic ribbon samples. The maximum attainable coercivities, after adjusting the annealing time, were found to be very sensitive to the annealing temperatures. The optimum magnetic properties [{ital H}{sub {ital C}}=3.9 kOe, (BH){sub max}=10 MGOe] were obtained by annealing at 750{endash}775{degree}C for a few minutes. Optimization by flash annealing gave similar results. Microstructural studies show that the grain size is greater than the theoretically predicted grain size for optimum coupling between the hard and the soft phase. With the annealing conditions used, Nd{sub 4}Dy{sub 2}Fe{sub 87}NbB{sub 6} samples gave moderate coercivities and in Nd{sub 4}Y{sub 2}Fe{sub 87}NbB{sub 6} samples the coercivity was reduced more than the expected reduction in the anisotropy field due to the presence of Y. {copyright} {ital 1996 American Institute of Physics.}

  10. Transformation characteristics of organic pollutants in Fered-Fenton process for dry-spun acrylic fiber wastewater treatment.

    PubMed

    Wei, Jian; Song, Yonghui; Meng, Xiaoguang; Tu, Xiang; Pic, Jean-Stéphane

    2014-01-01

    The Fered-Fenton process using Ti sheet as cathode and RuO2/Ti as anode was employed for the pretreatment of dry-spun acrylic fiber manufacturing wastewater. The effects of feeding mode and concentration of H2O2 on chemical oxygen demand (COD) removal efficiency as well as the biodegradability variation during the Fered-Fenton process were investigated. The feeding mode of H2O2 had significant influence on COD removal efficiency: the removal efficiency was 44.8% if all the 60.0 mM H2O2 was fed at once, while it could reach 54.1% if the total H2O2 was divided into six portions and fed six times. The biochemical oxygen demand/COD ratio increased from 0.29 to above 0.68 after 180 min treatment. The transformation characteristics of organic pollutants during the Fered-Fenton process were evaluated by using gas chromatography-mass spectrometry (GC-MS), Fourier transform infrared spectroscopy (FTIR) and fluorescence excitation-emission matrix (EEM) spectroscopy. Most of the refractory organic pollutants with aromatic structure or large molecular weight were decomposed during the Fered-Fenton process. PMID:25521133

  11. Long-lasting tectonic activities of the Lepontine Dome. New evidence from low-temperature thermochronology

    NASA Astrophysics Data System (ADS)

    Elfert, Simon; Reiter, Wolfgang; Spiegel, Cornelia

    2013-11-01

    To investigate the Neogene exhumation history of the central European Alps, we apply low-temperature thermochronology in combination with thermal history modelling. Fission track and (U-Th-Sm)/He ages on apatites from the central Lepontine Dome (Ticino, Switzerland) indicate higher exhumation rates in the centre of the dome and rather moderate exhumation at the northern and southern boundaries since Neogene times. We present a model for explaining the latest stage exhumation of the central Lepontine Dome and show that (I) both episodic and continuous exhumations are found on small-scale throughout the Neogene, (II) compressional tectonics control the exhumation until the Late Neogene, (III) the exhumation regime changes between 6 and 4 Ma and (IV) increasing hinterland exhumation rates at the Mio-Pliocene boundary cannot be related to tectonic structures of the dome and they are thus explained by climatic changes.

  12. Rheology of Lava Flows on Europa and the Emergence of Cryovolcanic Domes

    NASA Technical Reports Server (NTRS)

    Quick, Lynnae C.; Glaze, Lori S.; Baloga, Steve M.

    2015-01-01

    There is ample evidence that Europa is currently geologically active. Crater counts suggest that the surface is no more than 90 Myr old, and cryovolcanism may have played a role in resurfacing the satellite in recent geological times. Europa's surface exhibits many putative cryovolcanic features, and previous investigations have suggested that a number of domes imaged by the Galileo spacecraft may be volcanic in origin. Consequently, several Europa domes have been modeled as viscous effusions of cryolava. However, previous models for the formation of silicic domes on the terrestrial planets contain fundamental shortcomings. Many of these shortcomings have been alleviated in our new modeling approach, which warrants a re-assessment of the possibility of cryovolcanic domes on Europa.

  13. Mixing in the dome region of a staged gas turbine combustor

    NASA Astrophysics Data System (ADS)

    Sowa, W. A.; Brady, R. A.; Samuelsen, G. S.

    1992-07-01

    To lower NO(x) emissions from gas-turbine engines the effect of dome design and operational changes on the mixing quality in the fuel-rich region is studied. A statistical analysis is employed to establish the parametric sensitivity in this complex flow. A mixing-effectiveness index is defined and used to optimize the gas-species uniformity and the extent of reaction at the exit plane of the dome. Mixing effectiveness is tied to the fuel and air injection locations, the macroscale structure of the dome aerodynamics, and the level of turbulence. Increases in nozzle/air to fuel ratio, reference velocities, and the dome expansion angle increased the level of turbulence. The optimum configuration featured counter-swirling fuel and air streams and produced a strong torroidal recirculation zone, an effective spray angle of 45 degrees, and azimuthal velocities that decayed to zero inside of two duct diameters. The results underscore the system specific nature of mixing optimization.

  14. Observation of Double-Dome Superconductivity in Potassium-Doped FeSe Thin Films.

    PubMed

    Song, Can-Li; Zhang, Hui-Min; Zhong, Yong; Hu, Xiao-Peng; Ji, Shuai-Hua; Wang, Lili; He, Ke; Ma, Xu-Cun; Xue, Qi-Kun

    2016-04-15

    We report on the emergence of two disconnected superconducting domes in alkali-metal potassium- (K-)doped FeSe ultrathin films grown on graphitized SiC(0001). The superconductivity exhibits hypersensitivity to K dosage in the lower-T_{c} dome, whereas in the heavily electron-doped higher-T_{c} dome it becomes spatially homogeneous and robust against disorder, supportive of a conventional Cooper-pairing mechanism. Furthermore, the heavily K-doped multilayer FeSe films all reveal a large superconducting gap of ∼14  meV, irrespective of film thickness, verifying the higher-T_{c} superconductivity only in the topmost FeSe layer. The unusual finding of a double-dome superconducting phase is a step towards the mechanistic understanding of superconductivity in FeSe-derived superconductors. PMID:27127981

  15. Tithonium Chasma Domes: A Result of Salt Diapirism by Means of Thin-skinned Extension?

    NASA Astrophysics Data System (ADS)

    Popa, C. I.; Esposito, F.; Ori, G. G.; Marinangeli, L.; Colangeli, L.

    2007-03-01

    The study focuses on the origin and evolution of the salt bearing deposits in Tithonium Chasma. We tested the hypothesis of domes as result of diapirism upraise in thin-skinned extension conditions from a previously deposited salt layer.

  16. Hydrogen-isotope evidence for extrusion mechanisms of the Mount St Helens lava dome

    NASA Technical Reports Server (NTRS)

    Anderson, Steven W.; Fink, Jonathan H.

    1989-01-01

    Hydrogen isotope analyses were used to determine water content and deuterium content for 18 samples of the Mount St Helens dome dacite in an attempt to identify the triggering mechanisms for periodic dome-building eruptions of lava. These isotope data, the first ever collected from an active lava dome, suggest a steady-state process of magma evolution combining crystallization-induced volatile production in the chamber with three different degassing mechanisms: closed-system volatile loss in the magma chamber, open-system volatile release during ascent, and kinetically controlled degassing upon eruption at the surface. The data suggest the future dome-building eruptions may require a new influx of volatile-rich magma into the chamber.

  17. Observation of Double-Dome Superconductivity in Potassium-Doped FeSe Thin Films

    NASA Astrophysics Data System (ADS)

    Song, Can-Li; Zhang, Hui-Min; Zhong, Yong; Hu, Xiao-Peng; Ji, Shuai-Hua; Wang, Lili; He, Ke; Ma, Xu-Cun; Xue, Qi-Kun

    2016-04-01

    We report on the emergence of two disconnected superconducting domes in alkali-metal potassium- (K-)doped FeSe ultrathin films grown on graphitized SiC(0001). The superconductivity exhibits hypersensitivity to K dosage in the lower-Tc dome, whereas in the heavily electron-doped higher-Tc dome it becomes spatially homogeneous and robust against disorder, supportive of a conventional Cooper-pairing mechanism. Furthermore, the heavily K-doped multilayer FeSe films all reveal a large superconducting gap of ˜14 meV , irrespective of film thickness, verifying the higher-Tc superconductivity only in the topmost FeSe layer. The unusual finding of a double-dome superconducting phase is a step towards the mechanistic understanding of superconductivity in FeSe-derived superconductors.

  18. Tharsis dome, Mars: New evidence for Noachian-Hesperian thick-skin and Amazonian thin-skin tectonics

    NASA Astrophysics Data System (ADS)

    Anguita, Francisco; Farelo, Agustín-Felipe; López, Valle; Mas, Cristina; Muñoz-Espadas, María-Jesús; Márquez, Álvaro; Ruiz, Javier

    2001-04-01

    A photogeological reconnaissance of Viking mosaics and images of the Tharsis dome has been carried out. Fifteen new areas of transcurrent faulting have been located which, together with other structures previously detected, support a model in which the Thaumasia Plateau, the southeastern part of the Tharsis dome, is proposed to be an independent lithospheric block that experienced buckling and thrust faulting in Late Noachian or Early Hesperian times as a result of an E-W directed compression. Evidence is presented that this stress field, rather than the Tharsis uplift, was decisive in the inception of Valles Marineris, which we consider a transtensive, dextral accident. The buckling spacing permits us, moreover, to tentatively reconstruct a Martian Hesperian lithosphere similar in elastic thickness to the mean present terrestrial oceanic lithosphere, thus supporting the possibility of a restricted lithospheric mobility in that period. Tharsis lithosphere was again subjected to shear stresses in Amazonian times, a period in which important accidents, such as strike-slip faults, wrinkle ridges, and straight and sigmoidal graben, were formed under a thin-skin tectonic regime, while the lithosphere as a mechanical unit had become too thick and strong to buckle. The possible causes of those stresses, and especially their relationships to a putative period of plate tectonics, are discussed.

  19. Blue Mountain and The Gas Rocks: Rear-Arc Dome Clusters on the Alaska Peninsula

    USGS Publications Warehouse

    Hildreth, Wes; Fierstein, Judy; Calvert, Andrew T.

    2007-01-01

    Behind the single-file chain of stratovolcanoes on the Alaska Peninsula, independent rear-arc vents for mafic magmas are uncommon, and for silicic magmas rarer still. We report here the characteristics, compositions, and ages of two andesite-dacite dome clusters and of several nearby basaltic units, all near Becharof Lake and 15 to 20 km behind the volcanic front. Blue Mountain consists of 13 domes (58-68 weight percent SiO2) and The Gas Rocks of three domes (62-64.5 weight percent SiO2) and a mafic cone (52 weight percent SiO2). All 16 domes are amphibole-biotite-plagioclase felsite, and nearly all are phenocryst rich and quartz bearing. Although the two dome clusters are lithologically and chemically similar and only 25 km apart, they differ strikingly in age. The main central dome of Blue Mountain yields an 40Ar/39Ar age of 632?7 ka, and two of the Gas Rocks domes ages of 25.7?1.4 and 23.3?1.2 ka. Both clusters were severely eroded by glaciation; surviving volumes of Blue Mountain domes total ~1 km3, and of the Gas Rocks domes 0.035 km3. Three basaltic vents lie close to The Gas Rocks, another lies just south of Blue Mountain, and a fifth is near the north shore of Becharof Lake. A basaltic andesite vent 6 km southeast of The Gas Rocks appears to be a flank vent of the arc-front center Mount Peulik. The basalt of Ukinrek Maars has been called transitionally alkalic, but all the other basaltic rocks are subalkaline. CO2-rich gas emissions near the eponymous Gas Rocks domes are not related to the 25-ka dacite dome cluster but, rather, to intracrustal degassing of intrusive basalt, one batch of which erupted 3 km away in 1977. The felsic and mafic vents all lie along or near the Bruin Bay Fault where it intersects a broad transverse structural zone marked by topographic, volcanologic, and geophysical discontinuities.

  20. Effect of boron additions on phase formation and magnetic properties of TbCu7-type melt spun SmFe ribbons

    NASA Astrophysics Data System (ADS)

    Zheng, Chuanjiang; Yu, Dunbo; Li, Kuoshe; Luo, Yang; Jin, Jinling; Lu, Shuo; Li, Hongwei; Mao, Yongjun; Quan, Ningtao

    2016-08-01

    Melt spun ribbons of a series of SmFe12Bx (x=0.0, 0.5, 0.75, 1.0, 1.25, and 1.5) have been prepared by the melt spinning technique. Sm-Fe-B melt spun ribbons with single phase TbCu7-type structure were prepared from the SmFe12Bx (x=0.5, 0.75, and 1.0) alloys at the surface velocity around 40 m/s. The addition of boron not only inhibits the appearance of soft magnetic phase α-Fe, but also enhances the ability of amorphous formation for melt spun Sm-Fe ribbons. The concentration of boron atoms, however, exceeds the limit of the solubility (x>1.0) of Sm-Fe alloys, which does not impede the appearance of α-Fe but accelerates the formation of metastable phase Sm2Fe23B3 that is unfavorable to their magnetic properties. Moreover, it is found that the addition of boron whose concentration is 0.0≤x≤0.75 can stabilize the metastable TbCu7-type structure because of the increase of the lattice parameter ratio c/a. The magnetic properties of as-annealed SmFe12B1.0 melt spun ribbons with an energy product of 2.19MGOe, a coercivity of 2.36 kOe and a remanence of 4.8 kGs have been achieved. The microstructural characteristics of as-annealed melt spun SmFe12 and SmFe12B1.0 ribbons have been discussed as well. The following sequence of the hyperfine field H(6l)

  1. First single star scidar measurements at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Vernin, J.; Chadid, M.; Aristidi, E.; Agabi, A.; Trinquet, H.; van der Swaelmen, M.

    2009-06-01

    Aims: We investigate the first operational running of the Single Star Scidar (SSS instrument) under harsh weather conditions at Dome C in Antarctica and examine continuous monitoring of the optical turbulence and wind speed profiles throughout the atmosphere. Methods: SSS is mainly composed of commercially available light-weight components and a 16 inch telescope installed on an equatorial mount. Scintillation patterns were computed (auto and cross-correlations) in real time and analyzed off line to retrieve continuously vertical profiles of optical turbulence C_N^2(h) and wind speed V(h), from the ground up to 20 km. Results: Using a simulated annealing method, we have analyzed about 6.5 h of observations, revealing the strong surface layer contribution to seeing degradation. SSS results show a good seeing agreement with simultaneous measurements with a Differential Image Motion Monitor, even under very good seeing as low as 0.2 arcsec, as well as wind speed agreement when compared to the weather archive from NOAA. Conclusions: SSS has shown its usefulness for site characterization since it simultaneously measures C_N2 and V profiles, from which most adaptative optic parameters are deduced, such as isoplanatic angle and coherence time of the wavefront. Due to its small size, it is well adapted for site characterization, even when low infrastructure is available.

  2. High precision metrology of domes and aspheric optics

    NASA Astrophysics Data System (ADS)

    Murphy, Paul E.; Fleig, Jon; Forbes, Greg; Tricard, Marc

    2005-05-01

    Many defense systems have a critical need for high-precision, complex optics. However, fabrication of high quality, advanced optics is often seriously hampered by the lack of accurate and affordable metrology. QED's Subaperture Stitching Interferometer (SSI®) provides a breakthrough technology, enabling the automatic capture of precise metrology data for large and/or strongly curved (concave and convex) parts. QED"s SSI complements next-generation finishing technologies, such as Magnetorheological Finishing (MRF®), by extending the effective aperture, accuracy and dynamic range of a phase-shifting interferometer. This workstation performs automated sub-aperture stitching measurements of spheres, flats, and mild aspheres. It combines a six-axis precision stage system, a commercial Fizeau interferometer, and specially developed software that automates measurement design, data acquisition, and the reconstruction of the full-aperture figure error map. Aside from the correction of sub-aperture placement errors (such as tilts, optical power, and registration effects), our software also accounts for reference-wave error, distortion and other aberrations in the interferometer"s imaging optics. The SSI can automatically measure the full aperture of high numerical aperture surfaces (such as domes) to interferometric accuracy. The SSI extends the usability of a phase measuring interferometer and allows users with minimal training to produce full-aperture measurements of otherwise untestable parts. Work continues to extend this technology to measure aspheric shapes without the use of dedicated null optics. This SSI technology will be described, sample measurement results shown, and various manufacturing applications discussed.

  3. Hard transparent domes and windows from magnesium aluminate spinel

    NASA Astrophysics Data System (ADS)

    DiGiovanni, Anthony A.; Fehrenbacher, Larry; Roy, Don W.

    2005-05-01

    Transparent magnesium aluminate spinel is an attractive material for use in a wide range of optical applications including windows, domes, armor, and lenses, which require excellent transmission from the visible through to the mid IR. Theoretical transmission is very uniform and approaches 87% between 0.3 to 5 microns. Transmission characteristics rival that of ALON and sapphire in the mid-wave IR, making it especially attractive for the everincreasing performance requirements of current and next-generation IR imaging systems. Future designs in missile technology will require materials that can meet stringent performance demands in both optical and RF wavelengths. Loss characteristics for spinel are being investigated to meet those demands. Technology Assessment and Transfer Inc. (TA&T), have established a 9000 ft2 production facility for optical quality spinel based on the traditional hot-pressing followed by hot isostatic pressing (HIPing) route. Additionally, TA&T is developing pressureless sintering - a highly scalable, near net shape processing method based on traditional ceramic processing technology - to fabricate optical components. These two main processing approaches allow the widest variety of applications to be addressed using a range of optical components and configurations. The polycrystalline nature of spinel facilitates near net shape processing, which provides the potential to fabricate physically larger optical parts or larger quantities of parts at significantly lower costs compared to single crystal materials such as sapphire. Current research is focused at optimizing the processing parameters for both synthesis routes to maximize strength and transparency while minimizing the cost of fabrication.

  4. Time domain astronomy from Dome C: results from ASTEP

    NASA Astrophysics Data System (ADS)

    Rivet, J.-P.; Abe, L.; Agabi, K.; Barbieri, M.; Crouzet, N.; Goncalves, I.; Guillot, T.; Mekarnia, D.; Szulagyi, J.; Daban, J.-B.; Gouvret, C.; Fantei-Caujolle, Y.; Schmider, F.-X.; Furth, T.; Erikson, A.; Rauer, H.; Fressin, F.; Alapini, A.; Pont, F.; Aigrain, S.

    2013-01-01

    ASTEP (Antarctic Search for Transiting Exo Planets) is a research program funded mainly by French ANR grants and by the French Polar Institute (IPEV), dedicated to the photometric study of exoplanetary transits from Antarctica. The preliminary ``pathfinder'' instrument ASTEP-South is described in another communication (Crouzet et al., these proceedings), and we focus in this presentation on the main instrument of the ASTEP program: ``ASTEP-400'', a 40 cm robotized and thermally-controlled photometric telescope operated from the French-Italian Concordia station (Dome C, Antarctica). ASTEP-400 has been installed at Concordia during the 2009-2010 summer campaign. Since, the telescope has been operated in nominal conditions during 2010 and 2011 winters, and the 2012 winterover is presently in progress. Data from the first two winter campaigns are available and processed. We give a description of the ASTEP-400 telescope from the mechanical, optical and thermal point of view. Control and software issues are also addressed. We end with a discussion of some astronomical results obtained with ASTEP-400.

  5. Three-dimensional representations of salt-dome margins at four active strategic petroleum reserve sites.

    SciTech Connect

    Rautman, Christopher Arthur; Stein, Joshua S.

    2003-01-01

    Existing paper-based site characterization models of salt domes at the four active U.S. Strategic Petroleum Reserve sites have been converted to digital format and visualized using modern computer software. The four sites are the Bayou Choctaw dome in Iberville Parish, Louisiana; the Big Hill dome in Jefferson County, Texas; the Bryan Mound dome in Brazoria County, Texas; and the West Hackberry dome in Cameron Parish, Louisiana. A new modeling algorithm has been developed to overcome limitations of many standard geological modeling software packages in order to deal with structurally overhanging salt margins that are typical of many salt domes. This algorithm, and the implementing computer program, make use of the existing interpretive modeling conducted manually using professional geological judgement and presented in two dimensions in the original site characterization reports as structure contour maps on the top of salt. The algorithm makes use of concepts of finite-element meshes of general engineering usage. Although the specific implementation of the algorithm described in this report and the resulting output files are tailored to the modeling and visualization software used to construct the figures contained herein, the algorithm itself is generic and other implementations and output formats are possible. The graphical visualizations of the salt domes at the four Strategic Petroleum Reserve sites are believed to be major improvements over the previously available two-dimensional representations of the domes via conventional geologic drawings (cross sections and contour maps). Additionally, the numerical mesh files produced by this modeling activity are available for import into and display by other software routines. The mesh data are not explicitly tabulated in this report; however an electronic version in simple ASCII format is included on a PC-based compact disk.

  6. Why there was a useful plausible analogy between geodesic domes and spherical viruses.

    PubMed

    Morgan, Gregory J

    2006-01-01

    In 1962, Donald Caspar and Aaron Klug published their classic theory of virus structure. They developed their theory with an explicit analogy between spherical viruses and Buckminster Fuller's geodesic domes. In this paper, I use the spherical virus-geodesic dome case to develop an account of analogy and deductive analogical inference based on the notion of an isomorphism. I also consider under what conditions there is a good reason to claim an experimentally untested analogy is plausible. PMID:17702504

  7. Technologies for precision manufacture of current and future windows and domes

    NASA Astrophysics Data System (ADS)

    Hallock, Bob; Shorey, Aric

    2009-05-01

    The final finish and characterization of windows and domes presents a number of challenges in achieving desired precision with acceptable cost and schedule. This becomes more difficult with advanced materials and as window and dome shapes and requirements become more complex, including acute angle corners, transmitted wavefront specifications, aspheric geometries and trending toward conformal surfaces. Magnetorheological Finishing (MRF®) and Magnetorheological Jet (MR Jet®), along with metrology provided by Sub-aperture Stitching Interferometry (SSI®) have several unique attributes that provide them advantages in enhancing fabrication of current and next generation windows and domes. The advantages that MRF brings to the precision finishing of a wide range of shapes such as flats, spheres (including hemispheres), cylinders, aspheres and even freeform optics, has been well documented. Recent advancements include the ability to finish freeform shapes up to 2-meters in size as well as progress in finishing challenging IR materials. Due to its shear-based removal mechanism in contrast to the pressure-based process of other techniques, edges are not typically rolled, in particular on parts with acute angle corners. MR Jet provides additional benefits, particularly in the finishing of the inside of steep concave domes and other irregular shapes. The ability of MR Jet to correct the figure of conformal domes deterministically and to high precision has been demonstrated. Combining these technologies with metrology techniques, such as SSI provides a solution for finishing current and future windows and domes in a reliable, deterministic and cost-effective way. The ability to use the SSI to characterize a range of shapes such as domes and aspheres, as well as progress in using MRF and MR Jet for finishing conventional and conformal windows and domes with increasing size and complexity of design will be presented.

  8. Reconnaissance and deep-drill site selection on Taylor Dome, Antarctica

    NASA Technical Reports Server (NTRS)

    Grootes, Pieter M.; Waddington, Edwin D.

    1993-01-01

    Taylor Dome is a small ice dome near the head of Taylor Valley, Southern Victoria Land. The location of the dome, just west of the Transantarctic Mountains, is expected to make the composition of the accumulating snow sensitive to changes in the extent of the Ross Ice Shelf. Thus, it is linked to the discharge of the West Antarctic Ice Sheet but protected against direct influences of glacial-interglacial sea-level rise. The record of past climatic and environmental changes in the ice provides a valuable complement to the radiocarbon-dated proxy record of climate derived from perched deltas, strandlines, and moraines that have been obtained in the nearby Dry Valleys. We carried out a reconnaissance of the Taylor Dome area over the past two field seasons to determine the most favorable location to obtain a deep core to bedrock. A stake network has been established with an 80-km line roughly along the crest of Taylor Dome, and 40-km lines parallel to it and offset by 10 km. These lines have been surveyed 1990/91, and the positions of 9 grid points have been determined with geoceivers. A higher density stake network was placed and surveyed around the most likely drill area in the second year. Ground-based radar soundings in both years provided details on bedrock topography and internal layering of the ice in the drill area. An airborne radar survey in January 1992, completed the radar coverage of the Taylor Dome field area.

  9. A user`s perspective on aluminum dome roofs for aboveground tanks

    SciTech Connect

    Myers, P.E.

    1995-12-31

    There is a trend in the petroleum industry to install aluminum dome roofs on storage tanks of all kinds. Although most dome roofs have been installed on floating roof tanks, there is a trend to install them on fixed roof tanks as well, substituting the familiar shallow fixed cone roof with a geodesic dome. In part, this trend has been caused by EPA requirements causing a greater number of closed tanks to be vented to vapor recovery or vapor destruction systems. Both the aluminum roof manufacturing community and the user have moved into a whole new set of problems associated with the change in dome roof applications from atmospheric to those requiring internal pressure. New problems are just now being dealt with and solved because cost factors tend to make the aluminum dome an economic solution for many cases where sealed tank systems must be used. Because of the increased numbers of geodesic domes as either an alternative to a fixed cone roof tank or as a way to convert an external floating roof tank to an internal floating roof tank or as their potential to serve as tools in the environmental arena, it is the intent of this paper to examine them from the user`s perspective. In addition, some areas of research that should resolve some reliability and safety issues are presented for consideration and research by not only manufacturers but the users as well.

  10. Performance analysis of the retractable dome for the Chinese Large Telescope.

    PubMed

    Nian, Pan; Wen-Li, Ma

    2015-10-01

    In order to quantitatively assess the influence of the retractable dome on the observational performance of the 4-m Chinese Large Telescope (CLT), an integrated analysis method based on computational fluid dynamics (CFD) and sub-harmonic phase screen is proposed in this paper. The pressure, the temperature, and the speed of air surrounding the retractable dome are attained by CFD simulations, and then the fluctuation of refractive index of air is calculated. Based on sub-harmonic phase screen algorithm, three kinds of performance evaluation parameters are presented: irradiance, phase of the target, and Full Width Half Maximum (FWHM). The wind tunnel tests (WT) with a 1:120 scaled model of the retractable dome for the CLT are conducted to verify the calculated precision of the CFD. The results show that the fluctuation of air refractive index surrounding the CLT is mainly caused by the inhomogeneous distribution of temperature and speed, and with the help of pier's height the impact of inhomogeneous air temperature from the ground layer on the fluctuation of air refractive index can be effectively decreased. Furthermore, the lower of the air speed is, the better performance of the retractable dome will be, and when the speed of air is less than 5m/s, the dome seeing induced by the retractable dome on the observational wave front is less than 0.13 arcsec. PMID:26480059

  11. Diaphragm dome surface segmentation in CT data sets: a 3D active appearance model approach

    NASA Astrophysics Data System (ADS)

    Beichel, Reinhard; Gotschuli, Georg; Sorantin, Erich; Leberl, Franz W.; Sonka, Milan

    2002-05-01

    Knowledge about the location of the diaphragm dome surface, which separates the lungs and the heart from the abdominal cavity, is of vital importance for applications like automated segmentation of adjacent organs (e.g., liver) or functional analysis of the respiratory cycle. We present a new 3D Active Appearance Model (AAM) approach to segmentation of the top layer of the diaphragm dome. The 3D AAM consists of three parts: a 2D closed curve (reference curve), an elevation image and texture layers. The first two parts combined represent 3D shape information and the third part image intensity of the diaphragm dome and the surrounding layers. Differences in height between dome voxels and a reference plane are stored in the elevation image. The reference curve is generated by a parallel projection of the diaphragm dome outline in the axial direction. Landmark point placement is only done on the (2D) reference curve, which can be seen as the bounding curve of the elevation image. Matching is based on a gradient-descent optimization process and uses image intensity appearance around the actual dome shape. Results achieved in 60 computer generated phantom data sets show a high degree of accuracy (positioning error -0.07+/-1.29 mm). Validation using real CT data sets yielded a positioning error of -0.16+/-2.95 mm. Additional training and testing on in-vivo CT image data is ongoing.

  12. Final report on decommissioning boreholes and wellsite restoration, Gulf Coast Interior Salt Domes of Mississippi

    SciTech Connect

    Not Available

    1989-04-01

    In 1978, eight salt domes in Texas, Louisiana, and Mississippi were identified for study as potential locations for a nuclear waste repository as part of the National Waste Terminal Storage (NWTS) program. Three domes were selected in Mississippi for ``area characterization`` phase study as follows: Lampton Dome near Columbia, Cypress Creek Dome near New Augusta, and Richton Dome near Richton. The purpose of the studies was to acquire geologic and geohydrologic information from shallow and deep drilling investigations to enable selection of sites suitable for more intensive study. Eleven deep well sites were selected for multiple-well installations to acquire information on the lithologic and hydraulic properties of regional aquifers. In 1986, the Gulf Coast salt domes were eliminated from further consideration for repository development by the selection of three candidate sites in other regions of the country. In 1987, well plugging and restoration of these deferred sites became a closeout activity. The primary objectives of this activity are to plug and abandon all wells and boreholes in accordance with state regulations, restore all drilling sites to as near original condition as feasible, and convey to landowners any wells on their property that they choose to maintain. This report describes the activities undertaken to accomplish these objectives, as outlines in Activity Plan 1--2, ``Activity Plan for Well Plugging and Site Restoration of Test Hole Sites in Mississippi.``

  13. Percutaneous Ethanol Injection via an Artificially Induced Right Hydrothorax for Hepatocellular Carcinoma in the Hepatic Dome

    SciTech Connect

    Kume, Akimichi Nimura, Yuji; Kamiya, Junichi; Nagino, Masato; Kito, Yasushi

    2003-11-15

    To evaluate the efficacy of sonographically (US) guided percutaneous ethanol injection (PEI) via an artificially induced right hydrothorax (transthoracic PEI) to treat US-invisible hepatocellular carcinoma (HCC) in the hepatic dome. Five cirrhotic patients with US-invisible HCC in the hepatic dome, who were poor surgical candidates, underwent transthoracic PEI. An artificial right hydrothorax was created by instilling 500 ml saline, and absolute ethanol was injected transhydrothoracically into the hepatic dome lesion under local anesthesia. The success and complications were assessed radiologically. The patients were followed up serologically and radiologically for 12-44 (mean 28.4) months. Twenty-five hydrothoraces were induced. All hydrothoraces enabled US visualization of the entire hepatic dome. Eight of the nine small lesions were treated successfully by the treatment. Two of the three local recurrences were eradicated by repeat transthoracic PEI. One large lesion was treated by a combination of transthoracic and regular PEI. The only complication was one clinically insignificant pneumothorax. Induction of a right hydrothorax is feasible and safe. The hydrothorax enables US visualization of the entire hepatic dome and permits US-guided PEI for HCC in the hepatic dome that otherwise would not be possible.

  14. Time-delayed source and interferometric measurement of domes and windows

    NASA Astrophysics Data System (ADS)

    Kuhn, William P.; Dubin, Matthew

    2007-04-01

    Measurement of the transmitted wavefront of domes and windows is a long-standing problem. One may use a large return sphere and measure the interference cavity without the dome present and again with the dome present. The difference between the two measurements is a double-pass measurement of the transmitted wavefront of the dome. Even so, the long coherence length of the source results in many extraneous fringe patterns. Windows may be tested by using a collimated source and return flat. A time-delayed source (TDS) having a short-coherence length is used to obtain a single interference pattern due only to interference of light reflected by the two surfaces of a dome or window. Standard phase shifting algorithms may be used with the TDS to measure the optical thickness of a dome or window without errors due to multiple reflections. Since most of the interferometer is common-path, environmental sensitivity is reduced and alignment is straightforward compared to typical interferometers. Finally, since there is no reference surface, stitching of sub-aperture measurements is simplified.

  15. The Effectiveness of Modified Vertical Dome Division Technique in Reducing Nasal Tip Projection in Rhinoplasty

    PubMed Central

    Gandomi, Behrooz; Arzaghi, Mohammad Hossein; Rafatbakhsh, Mohammad

    2011-01-01

    Background: The technique of vertical dome division or tip defining, involves incising the lateral crura and vestibular skin at or lateral to the dome or tip defining point. The incision divides the lower lateral cartilage into a lateral segment and a medial segment, which are advanced anteriorly and sutured together to increase tip projection. The present study aimed at assessing a new vertical dome division, which is a modified version of vertical dome technique to decrease nasal tip projection, and increase or decrease nasal tip rotation and other tip deformities. Methods: The medical files of patients undergone rhinoplasty from 2003 to 2008 were retrospectively analyzed. The files were selected from a computerized rhinoplasty database of patients, who had been operated using a modified vertical dome technique and followed-up for one year or more after the surgery. Results: A total of 3756 patients were operated. Complications related to the nasal tip such as bossae, bifidity, persistent tip projection or tip asymmetry was seen in 81 patients (2.1%). Revisions for tip-related problems were performed in 42 patients (1.1%). Conclusions: The findings suggest that the modified vertical dome technique is an effective method for nasal tip deprojection and narrowing via an open approach. The length of follow-up and the large sample size support effectiveness of the technique. PMID:23359623

  16. Buyer's guide to telescopes at the best sites: Dome A, L2, and Shackleton Rim

    NASA Astrophysics Data System (ADS)

    Angel, J. Roger P.

    2004-10-01

    Future optical/infrared telescopes will need to be much larger than today"s, if they are to address such key challenges as direct observations of Earth-like exoplanets and of the first stars formed after the big bang. In this paper I consider the most promising of the new sites, both on the ground and in space, and telescope concepts to take advantage of their complementary scientific potential. Ground based telescopes with adaptive optics will be capable of diffraction limited imaging, down to a short wavelength limit set by the amplitude and speed of the atmospheric turbulence. The best conditions are on the high Antarctic plateau, where recent measurements at Dome C show turbulence typically half the amplitude of the best temperate sites, with temporal evolution at half the speed1. Thus uniquely in Antarctica, diffraction limited imaging at optical wavelengths should be practical. Conditions there are also best for infrared astronomy, given the combination of minimal aberration and winter temperatures averaging as low as 200K at Dome A (the highest point). In space, well away from the warm Earth, conditions are even better, with 24 hour/day observing free from all atmospheric aberration, and the potential for passive cooling to 50K or less by use of a sunshield. L2 and the Moon's south pole are such optimal space locations. A telescope at L2 requires only a little fuel to stay on orbit, and can be accurately pointed despite solar torques by well established active methods based on star trackers, gyros and reaction wheels. By contrast, the Moon provides a completely stable platform where a telescope with no moving parts can remain pointed indefinitely along the spin axis, or a telescope on a hexapod mount can be oriented and tracked by reaction to the turning lunar surface. Solar shielding on the Moon requires a polar location such as the high rim of the Shackleton crater, adjacent to the south pole, where there is also nearly continuous solar power. Long term

  17. Vertical profiles of the specific surface area of the snow at Dome C, Antarctica

    NASA Astrophysics Data System (ADS)

    Gallet, J.-C.; Domine, F.; Arnaud, L.; Picard, G.; Savarino, J.

    2010-09-01

    The specific surface area (SSA) of snow determines in Part the albedo of snow surfaces and the capacity of the snow to adsorb chemical species and catalyze reactions. Despite these crucial roles, almost no value of snow SSA are available for the largest permanent snow expanse on Earth, the Antarctic. We have measured the first vertical profiles of snow SSA near Dome C (DC: 75°06´ S, 123°20´ E, 3233 m a.s.l.) on the Antarctic plateau, and at seven sites during the logistical traverse between Dome C and the French coastal base Dumont D'Urville (DDU: 66°40´ S, 140°01´ E) during the Austral summer 2008-2009. We used the DUFISSS system, which measures the IR reflectance of snow at 1310 nm with an integrating sphere. At DC, the mean SSA of the snow in the top 1 cm is 38 m2 kg-1, decreasing monotonically to 14 m2 kg-1 at a depth of 15 cm. Along the traverse, the snow SSA profile is similar to that at DC in the first 600 km from DC. Closer to DDU, the SSA of the top 5 cm is 23 m2 kg-1, decreasing to 19 m2 kg-1 at 50 cm depth. This is attributed to wind, which causes a rapid decrease of surface snow SSA, but forms hard windpacks whose SSA decrease more slowly with time. Since light-absorbing impurities are not concentrated enough to affect albedo, the vertical profiles of SSA and density were used to calculate the spectral albedo of the snow for several realistic illumination conditions, using the DISORT radiative transfer model. A preliminary comparison with MODIS data is presented for use in energy balance calculations and for comparison with other satellite retrievals. These calculated albedos are compared to the few existing measurements on the Antarctic plateau. The interest of postulating a submillimetric, high-SSA layer at the snow surface to explain measured albedos is discussed.

  18. Mechanisms for rainfall-concurrent lava dome collapses at Soufrière Hills Volcano, 2000 2002

    NASA Astrophysics Data System (ADS)

    Taron, Joshua; Elsworth, Derek; Thompson, Glenn; Voight, Barry

    2007-02-01

    The evolution of rainfall-concurrent dome collapses at Soufrière Hills volcano is followed using a limit equilibrium model for rain infiltration into a hot lava carapace. Magma infusing into the dome both supplies heat and builds the slopes. The dome rocks are cooled by episodic rain infiltration and climatic cooling. Rainfall infiltrates fractures that develop in the hot dome carapace, occludes the void space, and staunches effusive gas flow. Gases may originate from juvenile de-gassing of the dome interior, or result from the vaporization of infiltrating water. Gas pressures build in cracks blocked-off by rain, and may destabilize the dome. The effects of dome growth, heating by magma infusion, and cooling by rain infiltration and climatic influences, are combined to follow the growth of the dome towards ultimate collapse. For a fixed suite of strength and transport parameters, and for measured magma influx rates, the evolution of instability may be followed. The evolving factor of safety tracks the observed March 2000 and July 2001 rainfall-concurrent collapse events, which evolve over months. However, the resolution of the hindcast is unable to discriminate between the effects of closely-timed rainfall events (order of hours). The heightening of the dome is shown to exert the principal influence on average slopes and in the evolution of instability. Collapse removes the over-heightened dome, and temporarily restores stability.

  19. Postural Control Disturbances Produced By Exposure to HMD and Dome Vr Systems

    NASA Technical Reports Server (NTRS)

    Harm, D. L.; Taylor, L. C.

    2005-01-01

    Two critical and unresolved human factors issues in VR systems are: 1) potential "cybersickness", a form of motion sickness which is experienced in virtual worlds, and 2) maladaptive sensorimotor performance following exposure to VR systems. Interestingly, these aftereffects are often quite similar to adaptive sensorimotor responses observed in astronauts during and/or following space flight. Most astronauts and cosmonauts experience perceptual and sensorimotor disturbances during and following space flight. All astronauts exhibit decrements in postural control following space flight. It has been suggested that training in virtual reality (VR) may be an effective countermeasure for minimizing perceptual and/or sensorimotor disturbances. People adapt to consistent, sustained alterations of sensory input such as those produced by microgravity, and experimentally-produced stimulus rearrangements (e.g., reversing prisms, magnifying lenses, flight simulators, and VR systems). Adaptation is revealed by aftereffects including perceptual disturbances and sensorimotor control disturbances. The purpose of the current study was to compare disturbances in postural control produced by dome and head-mounted virtual environment displays. Individuals recovered from motion sickness and the detrimental effects of exposure to virtual reality on postural control within one hour. Sickness severity and initial decrements in postural equilibrium decreases over days, which suggests that subjects become dual-adapted over time. These findings provide some direction for developing training schedules for VR users that facilitate adaptation, and address safety concerns about aftereffects.

  20. Strain-collapsed metamorphic isograds in a sillimanite gneiss dome, Seward Peninsula, Alaska

    SciTech Connect

    Miller, E.L.; Calvert, A.T.; Little, T.A. )

    1992-06-01

    Unusually closely spaced Barrovian series isograds have been described along the flanks of the Kigluaik Mountains, Seward Peninsula, Alaska, where they separate a high-grade gneiss complex intruded by granites of Cretaceous age from surrounding, regionally developed, blueschist to greenschist facies rocks. Structural mapping of the transition zone between the two metamorphic types indicates that their juxtaposition was aided by significant syn- to late-metamorphic solid-state flow that served to attenuate the overlying rock column and thus collapse the field metamorphic gradient. On the basis of field relations, structural data, petrography, and geochronologic data, strain appears to have accompanied the rapid (adiabatic) rise of high-temperature rocks from several tens of kilometers to less than 10 km depth during the Cretaceous, in an event younger than the unrelated to high-P metamorphism. Granite-cored gneiss domes on the Seward Peninsula may have formed during extension of previously thickened continental crust, resulting in the {approximately}35-km-thick crust and near-sea-level elevations of the region today.